Swachh Power - POWERGRID

September, 2015

Swachh Power A Glimpse of Power Quality in India

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About the Report

Economic growth of any country is directly influenced by availability of reliable and

quality power. Manufacturing sector plays an important role in industrialization and it requires

quality power for increased productivity. With the increased use of power electronics / non-

linear devices in the industrial, commercial, domestic sectors, as well as in the renewable

generation especially wind and solar generation connected through inverter or other electronic

devices; new power quality problems such as harmonics, interruptions, voltage dips, variations

in grid parameters etc. have emerged which need to be addressed suitably. Power quality has

now become an important component of service reliability to both utility and customers. It has

now become more critical due to modern industrial and commercial equipment becoming more

sensitive to minor voltage variations & quality of supply in general.

The Quality of Power Supply or ‘Power Quality’ is a new & ‘not so talked about’ term

for the Indian Power Sector. Quality of power can be measured in terms of parameters like

power frequency, supply voltage magnitude, flicker, voltage deviations (dips and swells),

voltage interruptions, transients, voltage unbalance, voltage harmonics, voltage inter-

harmonics, rapid voltage changes, under & over voltages etc. To assess the status of power

quality in the Indian Power System and plan for necessary preventive /corrective measures, the

first & foremost step is to conduct nation-wide surveys/measurements, collect the relevant data,

draw the financial aspects of maintaining Power-Quality & subsequently identify the mitigating

solutions. .

In this direction, Power Grid Corporation of India Ltd. has taken pioneering initiative

to measure the Power-Quality indices across the country at various towns/cities (at different

voltage levels), create a baseline data repository & present an analysis of Power-Quality in

Indian power system. This will enable identification of mitigating measures, its deployment

locations, industrial requirements etc. Towards this Power Quality measurement has been

carried out at about 175 towns/cities across the country covering almost all the states and union

territories through POWERGRID substations. These measurements have created a database of

more than 500 different locations in India. The observations on these measurements and

analyses have been presented in this report along with basic literature related to Power Quality,

measures to ensure Quality Power, proposed Investment requirements and International

initiatives in this direction.

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This report has been structured to understand the Power Quality in general and know

its baseline status across the country. It provides necessary fundamentals on power quality,

international experience and summary of field measurements at various voltage levels,

identified mitigating measures, way forward estimated investment required to address power

quality issues in Indian context. In this report an initial investment of Rs. 24,840 Cr. has been

identified towards providing quality power in India. There are seven (7) chapters in the report.

Chapter-1 describes the Power Quality concepts and their significance in power system.

Chapter-2 provides necessary fundamentals on power quality, its causes and consequences as

well as impact of power quality. Chapter-3 discusses various power quality standards

developed by IEEE, IEC, CEA, and other organizations. Some international experience on the

Power Quality Management has been presented in Chapter-4. Summary of Power quality

parameters at different voltage levels (765kV, 400kV, 220kV, 132kV, 66kV and in the LT

supplies) in the grid at different locations across the country based on field measurements along

with measurements carried out with various house hold appliances are presented in Chapter-5.

In addition to understanding power quality fundamentals and standards, it is important

to know how to solve the issues associated with various Power Quality Problems which are

deliberated in Chapter-6. Various types of power conditioning equipment addressing power

quality issues are presented, along with how they can solve the power quality problems.

Chapter-7 deals with the economics associated with power quality problem and

estimated investment required for mitigating measures to be deployed in Indian Power System.

At the end of this report, Annexure-A shows a brief analysis of Power Quality Measurements

done with various household equipment like TV, fan, CFL, mobile charger, oven, etc. An

exhaustive list of bibliography/references on Power Quality is also included to facilitate further

research/reading in this area.

This report is an initial milestone achieved in the direction of studying the Quality of

Power Supply in India; first attempt in the world to measure the Quality of Power across the

Grid, at various voltage-levels in a country. The improvement in the Quality of Power is not

just an aim but a regular process. Further periodic reviews would be required to keep a check

on the Quality of Supply at all the Voltage levels (especially Distribution Levels). Hence,

further improvements in the form of feedbacks from all the stakeholders are always solicited.

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TABLE OF CONTENTS

TABLE OF CONTENTS ..................................................................................................................... 1

LIST OF ABBREVIATIONS ............................................................................................................... I

CHAPTER-1 ................................................................................................................................... 1

1. POWER QUALITY AND ITS SIGNIFICANCE ...................................................................... 1

1.1 What is Power Quality? .......................................................................................................................... 1

1.2 Significance of Power Quality ................................................................................................................. 3

1.3 Reasons of poor power quality: .............................................................................................................. 4

1.3.1 Non-linear Loads .................................................................................................................................. 4

1.3.2 Unstable Power System ....................................................................................................................... 6

1.3.3 Large Machines / Equipment ............................................................................................................... 6

1.4 Impacts of Poor Power Quality ............................................................................................................... 6

1.4.1 Loss to Consumer ................................................................................................................................ 7

1.4.2 Loss to Utility ....................................................................................................................................... 9

1.5 Financial Losses ...................................................................................................................................... 9

1.5.1 Direct Costs .......................................................................................................................................... 9

1.5.2 Indirect Costs ..................................................................................................................................... 10

CHAPTER-2 ................................................................................................................................. 11

2 POWER QUALITY PARAMETERS ...................................................................................... 11

2.1 Harmonic Distortion ............................................................................................................................. 12

2.1.1 Sources of Harmonics ........................................................................................................................ 14

2.1.2 Problems caused by Non-linear loads ............................................................................................... 15

2.1.3 Effects of Harmonic Distortion .......................................................................................................... 16

2.2 Inter-harmonics .................................................................................................................................... 19

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2.2.1 Sources of Inter-harmonics ............................................................................................................... 19

2.2.2 Consequences of Inter-harmonics ..................................................................................................... 20

2.3 Power Factor ........................................................................................................................................ 20

2.3.1 Sources of Poor Power Factor ........................................................................................................... 21

2.3.2 Consequences of Poor Power Factor ................................................................................................. 21

2.4 Voltage Sag (or Dip) .............................................................................................................................. 22

2.4.1 Sources of Voltage Sag ...................................................................................................................... 22

2.4.2 Consequences of Voltage Sag ............................................................................................................ 23

2.5 Voltage Swell ........................................................................................................................................ 24

2.5.1 Sources of Voltage Swell.................................................................................................................... 24

2.5.2 Consequences of Voltage Swell ......................................................................................................... 25

2.6 Over Voltage / Under Voltage............................................................................................................... 25

2.6.1 Sources of Over / Under Voltage ....................................................................................................... 25

2.6.2 Consequences of Over / Under Voltage ............................................................................................ 26

2.7 Voltage Interruptions ........................................................................................................................... 26

2.7.1 Causes of Voltage Interruptions ........................................................................................................ 26

2.7.2 Effect of Voltage Interruptions .......................................................................................................... 27

2.8 Transient .............................................................................................................................................. 27

2.8.1 Sources of Transients......................................................................................................................... 28

2.8.2 Consequences of Transients .............................................................................................................. 29

2.9 Spike ..................................................................................................................................................... 29

2.9.1 Sources of Spikes ............................................................................................................................... 30

2.9.2 Consequences of Spikes .................................................................................................................... 30

2.10 Voltage Fluctuations & Flicker .......................................................................................................... 30

2.10.1 Sources of Voltage Fluctuation and Flicker ................................................................................... 31

2.10.2 Consequences of Voltage Fluctuation and Flicker ........................................................................ 32

2.11 Voltage Unbalance ........................................................................................................................... 32

2.11.1 Sources of Voltage Unbalance ...................................................................................................... 32

2.11.2 Consequences of Voltage Unbalance ........................................................................................... 33

2.11.3 Mitigation of Voltage Unbalance .................................................................................................. 33

2.12 DC Offset .......................................................................................................................................... 33

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2.13 K-Factor in Transformer ................................................................................................................... 34

2.14 Grounding for Power Quality ........................................................................................................... 35

2.15 Neutral Grounding for MV/HV/EHV Networks ................................................................................. 37

2.16 Impact of Power Quality .................................................................................................................. 39

CHAPTER-3 ................................................................................................................................. 41

3 POWER QUALITY STANDARDS ......................................................................................... 41

3.1 Standard related to various PQ phenomena ......................................................................................... 43

3.2 Standards for measurement, monitoring and mitigation ...................................................................... 45

3.3 Standards for testing procedure and equipment .................................................................................. 45

3.4 Standards regarding limitations for different PQ phenomena .............................................................. 46

3.5 Transformer overheating standards ..................................................................................................... 49

3.6 Trends in Power Quality Standards ....................................................................................................... 49

3.7 Power Quality in India .......................................................................................................................... 50

3.8 Some points to be noted: ..................................................................................................................... 53

CHAPTER-4 ................................................................................................................................. 56

4 INTERNATIONAL EXPERIENCES ON POWER QUALITY MANAGEMENT .............. 56

4.1 Power Quality Contracts ....................................................................................................................... 56

4.1.1 Power quality contracts by EdF (Électricité de France), France ........................................................ 56

4.1.2 Detroit Edison Company, USA ........................................................................................................... 58

4.1.3 National Electricity Regulator (NER), South Africa ............................................................................ 58

4.1.4 Norwegian Water Resources and Energy Directorate (NVE), Norway .............................................. 60

4.2 Extensive Measurements ...................................................................................................................... 61

4.3 Power Quality Services ......................................................................................................................... 61

4.4 Power Quality Labeling ......................................................................................................................... 62

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4.5 Cost of Poor Power Quality Survey: ...................................................................................................... 63

4.6 Voltage Sags in Process Industry Applications ...................................................................................... 64

4.7 The costs of Interruptions/Outages ...................................................................................................... 66

4.8 A Case Study in India: ........................................................................................................................... 69

4.9 Cost of poor Power Quality in India ...................................................................................................... 72

CHAPTER-5 ................................................................................................................................. 76

5 POWER QUALITY MONITORING ...................................................................................... 76

5.1 Where to look for Power Quality Issues? .............................................................................................. 76

5.2 Power Quality Measurement Tools ...................................................................................................... 76

5.3 Monitoring Power Quality .................................................................................................................... 77

5.4 Typical Harmonic Spectrum Signatures ................................................................................................. 79

5.5 Planning Power Quality Field Measurement ......................................................................................... 82

5.5.1 Measurement Procedure .................................................................................................................. 82

5.5.2 Set up ................................................................................................................................................. 82

5.5.3 Power Quality Data Management ..................................................................................................... 83

5.6 Field Measurement of Power Quality Parameters at EHV Grid Substations .......................................... 85

5.6.1 Power Quality Observation at 765 kV: .............................................................................................. 85



5.7 Region-Wise Summary of Power Quality Measurements in India ......................................................... 98

5.7.1 Summary of Power Quality Measurement in Eastern Region ........................................................... 98

5.7.2 Summary of Power Quality Measurement in Northern Region ...................................................... 106

5.7.3 Summary of Power Quality Measurement in Western Region ....................................................... 113

5.7.4 Summary of Power Quality Measurement in Southern Region ...................................................... 119

5.7.5 Summary of Power Quality Measurement in North-Eastern Region .............................................. 125

5.8 Power Quality Measurement in Typical Buildings ............................................................................... 132

5.9 Power Quality Measurement at a 132/33 kV Distribution substation ................................................. 135

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5.10 Power Quality Measurement on LT supply at various substations ................................................. 137

5.11 Power Quality Measurement of various household appliances ...................................................... 140

5.12 Broad Observation ......................................................................................................................... 142

CHAPTER-6 .............................................................................................................................. 147

6 SOLUTIONS FOR POWER QUALITY PROBLEMS ....................................................... 147

6.1 Mitigation of Power Quality Problems ................................................................................................ 147

6.1.1 Power Factor Improvement............................................................................................................. 147

6.1.2 Mitigation of Voltage Sag / Swell .................................................................................................... 149

6.1.3 Mitigation of Over / Under Voltage Conditions............................................................................... 149

6.1.4 Reduction of Voltage Interruptions ................................................................................................. 149

6.1.5 Mitigation of Transients .................................................................................................................. 149

6.1.6 Remedy for Voltage Notching ......................................................................................................... 149

6.1.7 Mitigation of Voltage Fluctuation and Flicker ................................................................................. 150

6.1.8 Mitigation of Harmonic / Inter Harmonic Distortions ..................................................................... 150

6.2 Planning for mitigation of Power Quality Issues ................................................................................. 152

6.3 Enhanced Interface Devices ................................................................................................................ 155

6.3.1 Series Capacitor ............................................................................................................................... 155

6.3.2 Shunt Capacitors .............................................................................................................................. 156

6.3.3 Static Var Compensator (SVC) ......................................................................................................... 156

6.3.4 STATCOM ......................................................................................................................................... 158

6.3.5 D-STATCOM ..................................................................................................................................... 161

6.3.6 Dynamic Voltage Restorer (DVR) ..................................................................................................... 162

6.3.7 Unified Power Quality Conditioner (UPQC) ..................................................................................... 163

6.3.8 Harmonic Filters .............................................................................................................................. 163

6.3.9 K-Factor Transformer ...................................................................................................................... 164

6.3.10 Transient Voltage Surge suppressors (TVSS) .............................................................................. 165

6.3.11 Isolation transformer .................................................................................................................. 165

6.4 Make End-use Devices Less Sensitive .................................................................................................. 166

CHAPTER-7 .............................................................................................................................. 169

7 INVESTMENTS FOR POWER QUALITY ........................................................................ 169

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7.1 Estimated Investments required in next 5 years ................................................................................. 169

7.2 Proposed Roles & Responsibilities of Statutory Bodies/Authorities towards ensuring Quality Supply in

the Indian Power System: ............................................................................................................................ 173

WAY FORWARD ................................................................................................................... 175

EXHIBIT A ................................................................................................................................ 179

POWER QUALITY CHARACTERISTICS OF HOUSEHOLD EQUIPMENT ....................... 179

REFERENCES ................................................................................................................................. 201

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List of Figures

FIGURE 1-1: TYPICAL LINEAR & NON-LINEAR CURRENT WAVEFORMS .................................................................. 5

FIGURE 1-2: DESKTOP SALES IN INDIA .................................................................................................................... 5

FIGURE 1-3: TABLET SALES IN INDIA ....................................................................................................................... 6

FIGURE 1-4: EQUIPMENT FAILURE DUE TO POOR POWER QUALITY ...................................................................... 8

FIGURE 2-1: FUNDAMENTAL WITH 3RD HARMONICS .......................................................................................... 12

FIGURE 2-2: FUNDAMENTAL WITH MULTIPLE HARMONICS ................................................................................ 13

FIGURE 2-3: DISTORTED COMPOSITE CURRENT WAVEFORM .............................................................................. 18

FIGURE 2-4: ADDITIVE THIRD HARMONICS .......................................................................................................... 18

FIGURE 2-5: POWER FACTOR RELATIONSHIP FOR LINEAR AND NON-LINEAR LOAD ............................................ 20

FIGURE 2-6: A TYPICAL VOLTAGE SAG .................................................................................................................. 22

FIGURE 2-7: TYPICAL CURRENT DRAWN BY ARC FURNACE .................................................................................. 23

FIGURE 2-8: TYPICAL VOLTAGE SWELL ................................................................................................................. 24

FIGURE 2-9: VOLTAGE SWELL OBSERVED ON A TYPICAL 400 KV LINE.................................................................. 25

FIGURE 2-10: TYPICAL VOLTAGE INTERRUPTIONS ................................................................................................ 26

FIGURE 2-11: TWO TYPES OF TRANSIENT WAVEFORMS ...................................................................................... 27

FIGURE 2-12: TYPICAL TRANSIENT DUE TO CAPACITOR SWITCHING ................................................................... 29

FIGURE 2-13: A TYPICAL SPIKE .............................................................................................................................. 29

FIGURE 2-14: VOLTAGE WAVEFORM CAUSING FLICKER ...................................................................................... 30

FIGURE 2-15: FLICKER SENSITIVITY CURVE BY GE ................................................................................................. 31

FIGURE 2-16: TYPICAL VOLTAGE UNBALANCE ...................................................................................................... 33

FIGURE 2-17: TYPICAL DC OFFSET IN VOLTAGE WAVEFORM. .............................................................................. 34

FIGURE 2-18: GROUNDING WITHOUT GROUND ROD .......................................................................................... 35

FIGURE 2-19: GROUNDING WITH GROUND ROD ................................................................................................. 36

FIGURE 3-1: POWER QUALITY STANDARDS HISTORICAL TREND .......................................................................... 50

FIGURE 3-2: TYPICAL VARIATION IN THD / TDD VS. LOAD (MW) ......................................................................... 53

FIGURE 4-1: POWER QUALITY CONTRACTS TO BE IMPLEMENTED BY THE DISTRIBUTION COMPANY ................ 59

FIGURE 4-2: COST OF POOR POWER QUALITY IN EU ............................................................................................ 63

FIGURE 4-3: COST OF POOR POWER QUALITY IN USA.......................................................................................... 64

FIGURE 4-4: CBEMA LIMITS .................................................................................................................................. 65

FIGURE 4-5: A TYPICAL COST VS. INTERRUPTION ................................................................................................. 66

FIGURE 4-6: COST OF MOMENTARY INTERRUPTIONS AND OUTAGES ................................................................. 67

FIGURE 4-7: LOSS PER VOLTAGE SAG IN DIFFERENT INDUSTRIES ........................................................................ 68

FIGURE 4-8: AVG. COST OF ELECTRICITY PER UNIT (LEFT) & AVG. MONTHLY ELECTRICITY COST (RIGHT) .......... 69

FIGURE 4-9: DISTRIBUTION OF INDUSTRIAL POWER SHORTAGE (HOURS PER WEEK) ......................................... 70

FIGURE 4-10: SHORTFALL IN PRODUCTION DUE TO POWER OUTAGES ............................................................... 70

FIGURE 4-11: COST ESCALATION DUE TO INTERRUPTIONS IN POWER SUPPLY ................................................... 71

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FIGURE 4-12: POWER QUALITY SOLUTIONS ......................................................................................................... 74

FIGURE 5-1: POINT OF COMMON COUPLING ....................................................................................................... 76

FIGURE 5-2: PQ DATA MANAGEMENT, REPORTING & ANALYTICS (POWER QUALITY DASHBOARD) .................. 84

FIGURE 5-3: AVERAGE VOLTAGE HARMONIC SPECTRUM AT 765 KV ACROSS INDIA ........................................... 86

FIGURE 5-4: DURATION CURVE OF VOLTAGE THD AT 765KV ACROSS INDIA ....................................................... 86

FIGURE 5-5: AVERAGE VOLTAGE THD AT 765KV LEVEL ........................................................................................ 87

FIGURE 5-6: TYPICAL AVERAGE VOLTAGE HARMONICS DAILY TREND AT 765 KV ACROSS THE COUNTRY .......... 88

FIGURE 5-7: AVERAGE THD IN PHASE VOLTAGES AT 400 KV LEVEL ..................................................................... 89

FIGURE 5-8: DURATION CURVE-400KV VOLTAGE THD ......................................................................................... 90

FIGURE 5-9: AVERAGE VOLTAGE HARMONIC SPECTRUM AT 400 KV ACROSS INDIA ........................................... 90

FIGURE 5-10: TYPICAL AVERAGE VOLTAGE HARMONICS DAILY TREND AT 400 KV ACROSS THE COUNTRY ........ 91

FIGURE 5-11: AVERAGE VOLTAGE UNBALANCE AT 400 KV .................................................................................. 92

FIGURE 5-12: AVERAGE THD IN PHASE AND NEUTRAL CURRENTS AT 400 KV SUBSTATIONS ACROSS INDIA ...... 93

FIGURE 5-13: THD IN PHASE VOLTAGES AT 220 KV LEVEL.................................................................................... 95

FIGURE 5-14: DURATION CURVE-220KV VOLTAGE THD ....................................................................................... 95

FIGURE 5-15: AVERAGE VOLTAGE HARMONIC SPECTRUM AT 220 KV ACROSS INDIA ......................................... 96

FIGURE 5-16: TYPICAL AVERAGE VOLTAGE HARMONICS DAILY TREND AT 220 KV ACROSS THE COUNTRY ........ 96

FIGURE 5-17: VOLTAGE UNBALANCE AT 220 KV .................................................................................................. 97

FIGURE 5-18: AVERAGE VOLTAGE HARMONICS MEASURED IN EASTERN REGION (AT 765KV) ........................... 98

FIGURE 5-19: AVERAGE CURRENT HARMONICS MEASURED IN EASTERN REGION (AT 765KV) ........................... 98

FIGURE 5-20: OVERALL POWER FACTOR DURATION CURVE (AT 765 KV LEVEL) .................................................. 99

FIGURE 5-21: VOLTAGE UNBALANCE DURATION CURVE (AT 765 KV LEVEL) ....................................................... 99

FIGURE 5-22: AVERAGE VOLTAGE HARMONICS MEASURED IN EASTERN REGION (400KV) .............................. 100

FIGURE 5-23: AVERAGE CURRENT HARMONICS MEASURED IN EASTERN REGION (400KV) .............................. 100

FIGURE 5-24: AVG. POWER FACTOR DURATION CURVE .................................................................................... 101

FIGURE 5-25: VOLTAGE UNBALANCE DURATION CURVE (AT 400KV) ................................................................ 101

FIGURE 5-26: AVERAGE VOLTAGE HARMONICS MEASURED IN EASTERN REGION (AT 220KV) ......................... 102

FIGURE 5-27: AVERAGE CURRENT HARMONICS MEASURED IN EASTERN REGION (AT 220KV) ......................... 102

FIGURE 5-28: OVERALL POWER FACTOR DURATION CURVE AT 220 KV LEVEL .................................................. 103

FIGURE 5-29: OVERALL VOLTAGE UNBALANCE DURATION CURVE AT 220 KV LEVEL ........................................ 103

FIGURE 5-30: AVERAGE VOLTAGE HARMONICS MEASURED IN EASTERN REGION (132KV) .............................. 104

FIGURE 5-31: AVERAGE CURRENT HARMONICS MEASURED IN EASTERN REGION (132KV) .............................. 104

FIGURE 5-32: OVERALL POWER FACTOR DURATION CURVE AT 132 KV LEVEL .................................................. 105

FIGURE 5-33: VOLTAGE UNBALANCE DURATION CURVE AT 132 KV LEVEL ........................................................ 105

FIGURE 5-34: AVERAGE VOLTAGE HARMONICS MEASURED IN EASTERN REGION (415V) ................................ 106

FIGURE 5-35: AVERAGE VOLTAGE HARMONICS AT 765 KV ................................................................................ 106

FIGURE 5-36: AVERAGE CURRENT HARMONICS AT 765 KV ................................................................................ 107

FIGURE 5-37: POWER FACTOR DURATION CURVE (AT 765KV) ........................................................................... 107


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FIGURE 5-38: UNBALANCE DURATION CURVE (AT 400KV) ................................................................................. 108

FIGURE 5-39: AVERAGE VOLTAGE HARMONICS (AT 400KV) .............................................................................. 108

FIGURE 5-40: AVERAGE CURRENT HARMONICS (AT 400KV) .............................................................................. 109

FIGURE 5-41 : POWER FACTOR DURATION CURVE (AT 400KV) .......................................................................... 109

FIGURE 5-42 : UNBALANCE DURATION CURVE (AT 400KV) ................................................................................ 110

FIGURE 5-43 : AVERAGE VOLTAGE HARMONICS MEASURED (AT 220KV) .......................................................... 110

FIGURE 5-44 : AVERAGE CURRENT HARMONICS MEASURED (AT 220KV) .......................................................... 111


FIGURE 5-46 : AVG. VOLTAGE UNBALANCE DURATION CURVE (AT 220KV) ....................................................... 112

FIGURE -5-47 : AVERAGE VOLTAGE HARMONICS IN 415V LT SUPPLY ................................................................ 112

FIGURE 5-48 : AVERAGE VOLTAGE HARMONICS (AT 765KV) ............................................................................. 113

FIGURE 5-49 : AVERAGE CURRENT HARMONICS (AT 765KV) ............................................................................. 113

FIGURE 5-50: OVERALL POWER FACTOR DURATION CURVE (AT 765 KV) .......................................................... 114

FIGURE 5-51: VOLTAGE UNBALANCE DURATION CURVE (AT 765 KV) ................................................................ 114



FIGURE 5-54 : POWER FACTOR DURATION CURVE (AT 400 KV) ......................................................................... 115

FIGURE 5-55: UNBALANCE DURATION CURVE (AT 400KV) ................................................................................. 116




FIGURE 5-59: UNBALANCE DURATION CURVE (AT 220 KV) ................................................................................ 118

FIGURE 5-60: AVERAGE VOLTAGE HARMONICS IN LT NETWORK ...................................................................... 118

FIGURE 5-61: AVERAGE VOLTAGE HARMONICS MEASURED (AT 765KV) ........................................................... 119

FIGURE 5-62: AVERAGE CURRENT HARMONICS MEASURED AT 765 KV ............................................................ 119

FIGURE 5-63: AVERAGE POWER FACTOR DURATION CURVE (AT 765 KV) ......................................................... 120

FIGURE 5-64: AVERAGE VOLTAGE HARMONICS MEASURED AT 400 KV ............................................................ 121

FIGURE 5-65: AVERAGE CURRENT HARMONICS MEASURED AT 400 KV ............................................................ 121

FIGURE 5-66: AVERAGE POWER FACTOR IN 400 KV ........................................................................................... 122

FIGURE 5-67: AVERAGE VOLTAGE UNBALANCE (VN%) IN 400 KV ...................................................................... 122

FIGURE 5-68: AVERAGE VOLTAGE HARMONICS MEASURED AT 220/230KV ...................................................... 123

FIGURE 5-69: AVERAGE CURRENT HARMONICS AT 220 KV ................................................................................ 123

FIGURE 5-70: POWER FACTOR DURATION CURVE (AT 220KV) ........................................................................... 124

FIGURE 5-71: UNBALANCE DURATION CURVE (AT 220 KV) ................................................................................ 124

FIGURE 5-72: AVERAGE VOLTAGE HARMONICS MEASURED AT LT NETWORK .................................................. 125

FIGURE 5-73: INDIVIDUAL VOLTAGE HARMONICS AT 400KV ............................................................................. 125

FIGURE 5-74: INDIVIDUAL CURRENT HARMONICS AT 400KV ............................................................................. 126

FIGURE 5-75: POWER FACTOR DURATION CURVE AT 400 KV ............................................................................ 126

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FIGURE 5-76: UNBALANCE DURATION CURVE AT 400KV ................................................................................... 127

FIGURE 5-77: INDIVIDUAL VOLTAGE HARMONICS MEASURED AT 220KV ......................................................... 127

FIGURE 5-78: INDIVIDUAL CURRENT HARMONICS AT 220KV LEVEL .................................................................. 128

FIGURE 5-79: POWER FACTOR DURATION CURVE AT 220KV ............................................................................. 128

FIGURE 5-80: VOLTAGE UNBALANCE DURATION CURVE AT 220KV ................................................................... 129

FIGURE 5-81: INDIVIDUAL VOLTAGE HARMONICS AT 132KV LEVEL .................................................................. 129

FIGURE 5-82: INDIVIDUAL CURRENT HARMONICS AT 132KV ............................................................................. 130

FIGURE 5-83 : POWER FACTOR DURATION CURVE AT 132KV ............................................................................ 130

FIGURE 5-84 : UNBALANCE DURATION CURVE AT 132KV .................................................................................. 131

FIGURE 5-85: HARMONIC SPECTRUM OF VOLTAGE AT PCC OF THE OFFICE BUILDING ..................................... 133

FIGURE 5-86: HARMONIC SPECTRUM IN UPS SUPPLY FEEDER OF A TYPICAL OFFICE BUILDING ....................... 134

FIGURE 5-87: HARMONIC SPECTRUM IN LIGHTING CURRENT OF A TYPICAL OFFICE BUILDING CONTAINING CFL,

FLUORESCENT & LED LAMPS ..................................................................................................................... 134

FIGURE 5-88: HARMONIC PROFILE &SPECTRUM IN THE CURRENT OF AIR CONDITIONING PLANT FEEDER OF A

TYPICAL OFFICE BUILDING ........................................................................................................................ 135

FIGURE 5-89: VOLTAGE & CURRENT HARMONIC SPECTRUM ON A 33 KV FEEDER. ........................................... 136

FIGURE 5-90: VOLTAGE HARMONIC SPECTRUM IN LT SUPPLY OF SUBSTATION ............................................... 137

FIGURE 5-91: OVERALL DURATION CURVE FOR TOTAL HARMONIC DISTORTION AT 415V ............................... 138

FIGURE 5-92: TYPICAL VOLTAGE AND CURRENT WAVE FORM OF A NON-LINEAR SINGLE PHASE APPLIANCE AND

HARMONIC CONTENT OF THE CURRENT DRAWN. ................................................................................... 141

FIGURE 5-93: TYPICAL VOLTAGE AND CURRENT WAVE FORM OF A LINEAR SINGLE PHASE APPLIANCE AND

HARMONIC CONTENT OF THE CURRENT DRAWN .................................................................................... 142

FIGURE 5-94: REGION-WISE POWER QUALITY PARAMETERS OBSERVED ACROSS THE COUNTRY ..................... 143

FIGURE 5-95 : POWER QUALITY MAP OF INDIA .................................................................................................. 146

FIGURE 6-1: POWER FACTOR IMPROVEMENT .................................................................................................... 148

FIGURE 6-2: PRINCIPLE OF PASSIVE HARMONIC FILTERS ................................................................................... 151

FIGURE 6-3: PRINCIPLE OF ACTIVE HARMONIC FILTERS ..................................................................................... 152

FIGURE 6-4: COST OF POWER QUALITY SOLUTION ............................................................................................ 153

FIGURE 6-5: BASIC STEPS INVOLVED IN POWER QUALITY PROBLEM EVALUATION. (COURTESY OF EPRI.) ....... 153

FIGURE 6-6: SOLUTIONS FOR POWER QUALITY PROBLEM ................................................................................. 154

FIGURE 6-7: VOLTAGE RISE DUE TO SERIES CAPACITORS ................................................................................... 155

FIGURE 6-8: STATIC VAR COMPENSATOR (SVC) ................................................................................................. 157

FIGURE 6-9: EFFECT OF STATIC VAR COMPENSATION ........................................................................................ 157

FIGURE 6-10: THYRSITOR-CONTROLLED REACTORS WITH FIXED CAPACITORS (OR SHUNT FILTERS) ................ 158

FIGURE 6-11: THYRISTOR-SWITCHED CAPACITORS (TSC) ................................................................................... 158

FIGURE 6-12: STATCOM (STATIC SYNCHRONOUS COMPENSATOR) ................................................................... 159

FIGURE 6-13: V-I CHARACTERISTICS OF STATCOM ............................................................................................. 160

FIGURE 6-14: D-STATCOM SCHEMATIC REPRESENTATION ................................................................................ 161


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FIGURE 6-15: DYNAMIC VOLTAGE RESTORER (DVR) SCHEMATIC DIAGRAM ..................................................... 162

FIGURE 6-16: TYPICAL HARDWARE STRUCTURE OF UPQC ................................................................................. 163

FIGURE 6-17: ISOLATION TRANSFORMER ........................................................................................................... 166

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Swachh Power

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List of Tables

TABLE 1-1: INCONVENIENCES TO CONSUMERS DUE TO POWER QUALITY PROBLEM ........................................... 8

TABLE 2-1: POWER QUALITY PROBLEMS BASED ON PARAMETERS DEVIATED .................................................... 12

TABLE 2-2: CLASSIFICATION OF OSCILLATORY TRANSIENTS ................................................................................. 28

TABLE 2-3: SUMMARY OF POWER QUALITY PROBLEMS, THEIR CAUSES AND EFFECTS ....................................... 38

TABLE 3-1: ORGANIZATIONS PUBLISHING POWER QUALITY STANDARDS ........................................................... 42

TABLE 3-2: POWER QUALITY STANDARDS ............................................................................................................ 43

TABLE 3-3: CHARACTERIZATION OF DIFFERENT PQ PHENOMENA SPECIFIED BY IEEE 1159-1995 ....................... 44

TABLE 3-4: VOLTAGE LIMITS AS PER CEA[8] ......................................................................................................... 46

TABLE 3-5: TEMPORARY OVER VOLTAGE LIMITS AS PER CEA[8] .......................................................................... 46

TABLE 3-6: PERMISSIBLE VOLTAGE UNBALANCE AS PER CEA[8] .......................................................................... 47

TABLE 3-7: VOLTAGE HARMONICS LIMIT AS PER CEA[8] ...................................................................................... 47

TABLE 3-8: CURRENT DISTORTION LIMITS FOR HARMONICS [3] ........................................................................... 48

TABLE 3-9: K-FACTORS FOR DIFFERENT LOADS .................................................................................................... 49

TABLE 4-1: EDF’S AND CUSTOMERS' OBLIGATIONS FOR MEDIUM VOLTAGE (BASIC CONTRACT) ....................... 57

TABLE 4-2: NRS-048 COMPLIANCE LIMITS IN SOUTH AFRICA .............................................................................. 60

TABLE 4-3: NVE DIRECTORATE COMPLIANCE LIMITS ........................................................................................... 61

TABLE 4-4: VIEW OF INDUSTRIAL FIRMS ON WILLINGNESS TO PAY FOR RELIABLE SUPPLY[12] ............................ 72

TABLE 5-1: TYPICAL HARMONICS FOUND IN DIFFERENT CONVERTERS ............................................................... 79

TABLE 5-2 SUMMARY OF POWER QUALITY MEASUREMENTS ON COMMON APPLIANCES ................................. 80

TABLE 5-3: THD & INDIVIDUAL HARMONICS IN VOLTAGE AT 765 KV .................................................................. 88

TABLE 5-4: MAX THD & INDIVIDUAL HARMONICS OBSERVED IN VOLTAGE AT 400 KV ....................................... 91

TABLE 5-5: MAX THD & INDIVIDUAL HARMONICS IN VOLTAGE AT 220 KV ......................................................... 96

TABLE 5-6: VOLTAGE HARMONICS DISTRIBUTION IN A TYPICAL OFFICE BUILDING POWER SUPPLY................. 132

TABLE 5-7: CURRENT HARMONICS DISTRIBUTION IN A TYPICAL OFFICE BUILDING POWER SUPPLY ................ 132

TABLE 5-8: VOLTAGE HARMONICS DISTRIBUTION AT A TYPICAL 132/33 KV S/STN ON 33 KV SIDE .................. 136

TABLE 5-9: CURRENT HARMONICS DISTRIBUTION AT A TYPICAL 132/33 KV S/STN ON 33 KV SIDE .................. 136

TABLE 5-10: VOLTAGE HARMONICS IN LT SUPPLY OF SUBSTATION .................................................................. 137

TABLE 5-11: CURRENT HARMONICS IN LT SUPPLY OF SUBSTATION .................................................................. 137

TABLE 5-12: THD, PST & PLT MEASURED IN LT/AUXILIARY SUPPLY AT VARIOUS SUBSTATIONS ....................... 138

TABLE 5-13: OVERVIEW OF POWER QUALITY PARAMETERS OBSERVED ACROSS THE COUNTRY ...................... 142

TABLE 5-14: SUMMARY OF CRITICAL POWER QUALITY PARAMETERS ............................................................... 143

TABLE 5-15: STATE WISE POWER QUALITY SEVERITY LEVEL .............................................................................. 144

TABLE 5-16: POWER QUALITY SEVERITY INDEX CALCULATION .......................................................................... 145

TABLE 6-1: SUMMARY OF POWER QUALITY PROBLEM AND SOLUTIONS .......................................................... 167

TABLE 7-1: STATE-WISE CONNECTED LOADS IDENTIFIED FOR POWER QUALITY IMPROVEMENT* ................... 169

TABLE 7-2: TOTAL CONNECTED LOAD IDENTIFIED FOR POWER QUALITY IMPROVEMENT* .............................. 169



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TABLE 7-3: COST OF POWER CONDITIONING DEVICE FOR A TYPICAL DT OF 500KVA ........................................ 171

TABLE 7-4: INDUSTRIAL VFDS/ASDS IN INDIA ..................................................................................................... 171

TABLE 7-5: INITIAL INVESTMENTS FOR POWER QUALITY IMPROVEMENT ......................................................... 172

TABLE 7-6: ROLES & RESPONSIBILITY OF VARIOUS AGENCIES ........................................................................... 173

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LIST OF ABBREVIATIONS

AHF Active Harmonic Filter

ASD Adjustable Speed Drive

CEA Central Electricity Authority

CEER Council of European Energy Regulators

CFL Compact Fluorescent lamp

CIGRE International Council on Large Electric Systems (French)

CVT Capacitive Voltage Transformer

DER Distributed Energy Resources

DG Distributed Generation

DPF Displacement Power Factor

DSTATCOM Distribution Static Compensator

DVR Dynamic Voltage Restorer

EDLC Electrochemical Double Layer Capacitor

ER Eastern Region

FACTS Flexible AC Transmission System

FC/TCR Fixed Capacitor/ Thyristor Controlled Reactor

GIC Geomagnetically Induced Current

GTO Gate Turn-Off

IEC International Electrotechnical Commission

IEEE Institute of Electrical and Electronics Engineers

IGBT Insulated Gate Bipolar Transistor

LPQI Leonardo Power Quality Initiative

NER North Eastern Region

NR Northern Region

OLTC On Load Tap Changer

PCC Point of Common Coupling

PLC Programmable Logic Controller

PQ Power Quality

PWM Pulse Width Modulation

SLG Single Line to Ground

SMC Special Manufacturing Contract

SMES Superconducting Magnetic Energy Storage

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SMPS Switched Mode Power Supply

SR Southern Region

SSSC Static Synchronous Series Compensator

STATCOM Static Synchronous Compensator

SVC Static VAR Compensator

TDD Total Demand Distortion

THD Total Harmonic Distortion

TVSS Transient Voltage Surge Suppression

UHV AC Ultra High Voltage AC

UPQC Unified Power Quality Conditioner

UPS Uninterruptible Power Supply

VFD Variable Frequency Drive

VSI Voltage Source Inverter

WR Western Region

i

Executive Summary

1. Power Quality and its Significance

Traditionally, the power system was simple and unidirectional, i.e. the flow of

electricity (power) used to be from source (generator) to sink (load) only. Power was

generated in bulk using conventional resources and then transmitted, distributed and

consumed by end users as load. Availability of power had more concern than the quality and

therefore the target used to be “to keep the lights on”, without taking reliability and quality of

power into account. Now the scenario is gradually changing. Modern power system has many

types of generation resources including renewable which have specific characteristics of

variability and intermittency connected to the grid through power conditioning equipment.

Transmission systems have become multifaceted with technologies like Ultra High Voltage

AC (UHVAC) / High Voltage Direct Current (HVDC) systems, power electronics based

Flexible AC Transmission Systems (FACTS) devices etc. Distributed generation and battery

storage systems are being connected with distribution system using power electronics

inverters to provide power supply including in remote areas.

Loads at consumer end have also changed their characteristics. Most of the electronic

devices being used by the consumers are non-linear type & sensitive to power quality.

Cumulatively all such changes in power system are affecting the quality of power supply. At

the same time consumers’ awareness, requirement and aspirations for quality power in terms

of continuity, sinusoidal shape and specified limits etc. are increasing.

Quality of Power Supply in any country also portrays the nation’s prosperity. With the

new initiatives like ‘Make in India’, India is already getting international attention especially

in the field of setting up new industries / manufacturing facilities. Other than the political

support, these industries certainly need Quality Power. It has been observed that International

Companies don’t have a good image of Power Supply in India. This is one of the reasons

which behold the foreign industries to set-up manufacturing facilities / plants or sophisticated

factories in India. Considering all these facts, maintaining ‘Power-Quality’ has now become

one of the major concerns for power system stakeholders.

To ensure high quality power for end consumers, it is important to identify the power

quality issues and its effects along with the locations for deployment of mitigating solutions.

In this direction, Power Grid Corporation of India Ltd. has taken pioneering initiative to

ii

measure the Power-Quality parameters across the country at various towns/cities (at different

voltage levels), create a baseline data repository & present an analysis of Power-Quality

situation in India. Towards this, Power Quality Measurements have been carried out at

various towns/cities across the country covering almost all the states and union territories

through 175 substations of POWERGRID. These measurements have created a database of

power quality parameters for more than 500 different feeders/points in India, since every

substation has multiple feeders connecting to different towns/cities (as shown in Figure 1).

Figure 1: Power Quality Measurement locations

2. Classification of Power Quality Problems

Power quality problems may be classified on the basis of events such as transient and

steady state, the quantity such as current, voltage, and frequency, or the load and supply

systems. The transient type of power quality problems include most of the phenomena

occurring in transient nature (e.g., impulsive or oscillatory in nature), such as voltage sag

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(dip), swell, short-duration voltage variations, power frequency variations, and voltage

fluctuations. The steady-state types of power quality problems include long-duration voltage

variations, waveform distortions, unbalanced voltages, DC offset, flicker, poor power factor,

unbalanced load currents, load harmonic currents, and excessive neutral current.

The second classification can be made on the basis of quantity such as voltage,

current and frequency. Corresponding to voltage, these include voltage distortions, flicker,

sag, swell, unbalance, under-voltage/overvoltage; similarly for the current, these include

reactive power component of the current, harmonic currents, unbalanced currents, excessive

neutral current etc.

The third classification of power quality problems is based on the load or the supply

system. Normally, power quality problems due to nature of the load (e.g., fluctuating loads

such as arc furnaces) consisting of current harmonics, reactive power component of the

current, unbalanced currents, neutral current, DC offset and so on.

The power quality problems due to the supply system consist of voltage and

frequency related issues such as voltage distortion, unbalance, sag, swell & flicker. These

may also consists of combination of both voltage and current based power quality problems

in the system. The frequency-related power quality problems are frequency variation above

or below the desired value. These affect the performance of a number of loads and other

equipment such as transformers, motors, luminaire etc. in the distribution system including

reduction of their service life & increased losses.

3. Brief Description of Various Power Quality Parameters

A brief description of various power quality parameters is elucidated in the following section:

Harmonic Distortion

Voltage or current waveforms in power system are normally expected to be sinusoidal

in shape of fundamental frequency (say 50 Hz). The harmonic frequencies are integral

multiples of fundamental frequency. For example 2nd harmonic in a 50Hz system is 2x50 i.e.,

100 Hz frequency.

Voltage Distortion is represented by the Total Harmonic Distortion (THD) which is

defined as the root mean square (r.m.s.) of the harmonics expressed as a percentage of the

fundamental component. Voltage Harmonics in the system are generated due to electric

machines working above the knee of the magnetization curve (magnetic saturation), arc

iv

furnaces, welding machines, rectifiers, DC brushless motors, non-linear loads (such as power

electronics equipment including Adjustable Speed Drives (ASDs), fan regulators, Compact

Fluorescent Lamps (CFLs), televisions, Switched Mode Power Supplies (SMPS), data

processing equipment, high efficiency lighting etc. While current harmonics are injected into

the system by the non-linear loads. The amount of voltage harmonics often depends upon the

amount of harmonic current drawn by the load, and the source impedance, which includes all

the wiring and transformers back to the source of the electricity. Harmonic currents increase

the rms value of supply current, increase losses, cause poor utilization and heating of

components of the distribution system, reducing their service life, malfunction of relay i.e.

protection system thereby affecting system safety & quality of supply, interference to

communication system & other equipment etc. and also cause distortion and notching in

voltage waveforms at the point of common coupling due to voltage drop in the source

impedance.

Power Factor

Power factor is a measure of how effectively a specific load consumes electricity to

produce work. Figure 2 shows the power vector relationships for both linear and non-linear

loads.

Figure 2: Power Factor Relationship for linear & Non-linear load

Power factor may be further classified as Displacement power factor and True power

factor. Displacement power factor is the cosine of the angle between the fundamental voltage

and current waveforms. The presence of harmonics introduces additional phase shift between

the voltage and the current. True power factor is calculated as the ratio between the total

v

active power used in a circuit (including harmonics) and the total apparent power (including

harmonics) supplied from the source. True power factor is always less than displacement

power factor if harmonics are present in the system.

Poor power factor results into requirement of higher apparent power and higher

current flow to do the same work against good power factor. It results into following

disadvantages:

i. Greater conductor size, hence, increased cost

ii. Higher capacity electrical equipment like generator or transformers which increases

size and cost of the system.

iii. Due to high current for low power factor, the losses increase in the conductors and

switchgear machinery

The large current at low lagging power factor causes greater voltage drops in

alternators, motors, transformers and transmission lines. This leads to decrease in voltage at

the driving end and forces the use of extra equipment to counter act the voltage drop like

voltage stabilizers.

Voltage Sag (or Dip)

Voltage Sag (or Dip) is defined as the reduction in voltage level in the range of 10%

to 90% of the nominal r.m.s. voltage at the power frequency, for a duration of 0.5 cycles to 1

minute. Figure 3 shows a typical voltage sag phenomena. Voltage sags are caused by faults

on the transmission or distribution network (most of the times on parallel feeders), faults at

consumer’s installation, connection of heavy loads, start-up of large motors etc. Arc furnace

is a good example of load that can produce large voltage sags in electrical power systems.

Figure 3: Typical Voltage sag phenomena

vi

Voltage sag may result into malfunction of Information Technology (IT) equipment,

namely microprocessor-based control systems (Personal Computers, Adjustable Speed

Drives, etc.) that may lead to a process stoppage, tripping of contactors and

electromechanical relays, disconnection and loss of efficiency in electric rotating machines,

thus loss in overall production etc.

Voltage Swell

Increase in voltage above 110% but below 180% of nominal, for a duration of 0.5

cycle to 1 minute is known as voltage swell. Figure 4 shows typical voltage swell waveform.

Figure 4: Typical Voltage Swell phenomena

Voltage swells are usually associated with system switching conditions. This is

particularly true for ungrounded or floating delta systems, where the sudden change in ground

reference result in a voltage rise on the ungrounded phases. Voltage swell due to a single

line-to-ground (SLG) fault on the system, results into a temporary voltage rise on the

unfaulted phases, which last for the duration of the fault. Voltage swells can also be caused

by the de-energization of a very large load.

Effects of a voltage swell are often more destructive. It may cause insulation failure,

breakdown of components on the power supplies of the equipment, malfunctioning of

protection system, though the effect may be gradual, but accumulative in type. It can cause

control problems and hardware failure in the equipment, due to overheating that could

eventually result to shut down. It also results in flickering of lighting and visualization

screens causing stress on human eyes / affects health.

Over / Under Voltage

Increase in the voltage to the level of 110% to 120% of the nominal voltage for more

than one (1) minute is known as over voltage, whereas reduction in voltage to the level of

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90% to 80% of the nominal voltage for more than 1 minute is called under voltage

phenomenon.

Over / under voltage is caused due to sudden load changes, high / low load conditions,

improper operation of compensation device, outage of lines / transformers /motors etc.

Lightly loaded long lines / cables causes over voltage in the system whereas heavily loaded

lines / cables causes under voltage. Continuous over voltage may result into over stress of

equipment, increased corona, flashover of insulators etc. whereas continuous under voltage

may result into inefficient operation of devices, increased losses, high current drawl, heating

effect and mal-operation of the power system components affecting system safety & quality

of supply.

Voltage interruption

A voltage interruption is the complete loss of voltage (<0.1 pu). Figure 5 shows

typical voltage interruption phenomena.

Figure 5: Typical Voltage Interruptions Phenomena

A disconnection of power supply causes interruption, which usually occur due to

opening of a circuit breaker, line recloser, or fuse due to faults. Tripping of protection

devices, loss of information and malfunction of data processing equipment and stoppage of

operation of sensitive equipment, such as ASDs, PCs, PLCs etc. happen due to voltage

interruptions.

Voltage Transients

Transients are momentary changes in voltage or current that occurs over a short

period of time generally of the order of microseconds as shown in Figure 6.

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Figure 6: Typical Two types of Transient Waveforms

A transient can be impulsive or a damped oscillatory types as shown in Figure-6. The

most common well known reason of transient is lightning, which causes induced voltage onto

conductors whenever it strikes near the power line. Other reasons of transients include

switching of large loads, opening and closing of disconnectors on energized lines, switching

of capacitor banks, switching of inductive loads, re-closure operations, tap changing on

transformers, loose connections in the power system etc.

Transients affect equipment in transmission / distribution system badly. It degrades

the contacting surfaces of switches, disconnectors, and circuit breakers. Electrical

transformers are forced to operate inefficiently because of the hysteresis losses produced by

transients and can run hotter than normal. Transients / Surge cause motors to run at higher

temperatures and result into vibration, noise, and excessive heat. Motor winding insulation is

degraded and eventually fails. It also produces hysteresis losses in motors and can cause early

failures. Transients also cause early failures of lighting devices and electronic equipment.

Voltage Fluctuation and Flicker

Voltage fluctuations are systematic variations of the voltage envelope, or a series of

random voltage changes in which amplitude is modulated by a signal with frequency less

than 25 Hz. In this phenomenon, voltage varies in the range of 0.1% to 7 % of the nominal

voltage. The most important effect of this power quality problem is the variation in the light

output of various lighting sources, commonly termed as Flicker. Flicker is the impression of

instability of the visual sensation brought about by a light stimulus, whose luminance

fluctuates with time. Light flicker results when there are voltage sub-harmonics in the range

of 1-30 Hz. The human eye is most sensitive at 8.8 Hz, where just a 0.5 % variation in the

rms voltage is noticeable with certain types of lighting. The result of this can be simply

ix

annoying, producing headaches and eye fatigue. Figure 7 shows the voltage fluctuation

causing flicker.

Figure 7: Typical Voltage waveform causing flicker

Loads such as electric arc furnaces, static frequency converters, cycloconverters,

rolling mill drives, main winders, large motors, bulbs during starting etc. may cause voltage

fluctuations and flicker. Small power loads such as welders, power regulators, boilers, cranes

and elevators, to name a few, may cause voltage fluctuation and flicker depending on the

electrical system where they are connected. Other causes of voltage fluctuations include

capacitor switching, transformer on-load tap changers (OLTC), other devices that alter the

inductive component of the source impedance, variations in generation capacity, particularly

intermittent type renewables (e.g. wind turbines, solar panels/inverters), low frequency

voltage inter-harmonics, loose connections etc.

Flicker is considered the most significant effect of voltage fluctuation, because it can

affect the production environment by causing personnel fatigue and lower work concentration

levels. In addition, voltage fluctuations may stress electrical and electronic equipment

towards detrimental effects that may disrupt production processes with considerable financial

loss.

Voltage Unbalance

Voltage unbalance in a three phase system occurs when variation in three phase

voltage magnitudes or the phase- angle differences between them are not equal. It is caused

by faulty operation of power factor correction equipment, unbalanced or unstable utility

supply, unbalanced transformer bank supplying a three-phase load that is too large for the

bank, unevenly distributed single-phase loads, unidentified single-phase to ground faults, an

x

open circuit on the system primary, large single-phase loads (induction furnaces, traction

loads) etc. Figure 8 shows the typical voltage unbalance phenomenon.

Figure 8: Typical Voltage Unbalance

Unbalanced systems imply the existence of a negative sequence component that is

harmful to all three- phase loads. The most affected loads are three-phase induction

machines. The main effect of voltage unbalance is motor damage from excessive heat.

Voltage unbalance can create a current unbalance 6 to 10 times the magnitude of voltage

unbalance, causing interference in nearby system besides damage of equipment.

DC Offset

DC offset is the presence of a DC current and/or voltage component in an AC system.

Main causes of DC offset in power systems are operation of rectifiers and other electronic

switching devices, geomagnetic disturbances causing Geo-magnetically Induced Current

(GIC) etc. Figure 9 shows typical dc offset in voltage waveform. DC offset in AC networks

cause saturation of transformer / reactor core, generation of even harmonics in addition to

odd harmonics, additional heating in appliances and electrolytic erosion of grounding

electrodes and other connectors. Three limb transformers with relatively large air gap

between core and tank is used for removal of dc offset caused by rectifiers and geo

magnetically induced currents.

xi

Figure 9: Typical DC offset in voltage waveform.

4. Impact of Power Quality

Until a few years ago, Power quality phenomena were considered just because of their

effects on the electromagnetic behavior of electrical devices, with a focus on fault

probability, components’ loss of life, or overload and so on. Now, increased attention to

environmental protection and energy savings in general drives us to consider Power Quality

phenomena also in the perspective of related energy losses. Poor power quality usually results

in various types of losses resulting due to increase in the rms value of supply current,

overheating of equipment, failures of equipment, shutting down of electronic equipment,

unwanted circuit breaker tripping, interference on communication system, flickering of

fluorescent lights, saturation of non-linear devices, reducing the service life of equipment,

requirement of higher size equipment, production loss in process industries etc.

As per a study on poor power quality (discussed in chapter 4), it has been observed

that industrial firms do not suffer any shortfall in production due to the erratic supply,

because the firms have adapted themselves to the current power scenario so well that all they

suffer is cost escalation due to use of power backups to support their production. The

industrial sector witnesses weekly interruptions ranging from less than one hour to more than

40 hours. Assuming an average interruption of say 30 minutes per week to the Industrial load

(connected load is approx.170 GW) in India, the average cost escalation (due to the use of

extra power backups) accounts to be around Rs. 2.65 Lakh Cr. per year. (Considering a very

conservative cost escalation of Rs. 10 per minute per kW of connected industrial load). In

addition, loss occur due to harmonics and poor power factor as well.

5. Power Quality Standards

Power quality Standards are needed for all the stakeholders in Power System. How

can utilities deliver and their customers receive the quality of power without Power quality

xii

standards? How can the electronic industries produce sensitive electronic equipment without

power quality standards? How can the Power conditioning industry manufacture devices that

will protect sensitive electronic equipment without power Quality standards? They can’t.

Therefore, stakeholders in the power sector have developed power quality standards.

They realize that the increased use of sensitive electronic equipment, increased application of

non-linear devices but to reduce stress on equipment, losses and improve energy efficiency,

and the increasingly complex and interconnected power system, integration of renewables

etc. all contribute to the need of power quality standards. Utilities need standards that define

limits on the amount of voltage distortion (caused by customer’s pollution), their power

systems can tolerate. End users need standards that set limits not only on the electrical

pollution produced by utility systems, but also similar pollution generated by other end users.

There are various prevailing Industrial Power-Quality standards like IEEE 519,

CBEMA, IEEE 1159, IEC 61000, etc. along with some of the standards by Central Electricity

Authority (CEA) to measure, mitigate & limit the various indices of Power-Quality.

6. Power Quality Field measurement

Importance of Power Quality is well understood internationally and appropriate

methods have been developed and employed to ensure quality power. In India, Central

Electricity Authority have notified required standards. In this direction, to establish base line

data about Power Quality parameters in the Indian Power system, Power quality

measurement were taken up by POWERGRID at the Grid level starting from its own sub-

stations across all the five regions in the country covering all the states and union territories.

Simultaneous measurements of various power quality parameters were carried out using

portable 3-phase Power Quality Analyser. Measurements from 6 hours to 24 hours at each

HV/EHV/UHV feeder/point were recorded at secondary terminals of respective CT/PT

whereas for LT supply direct measurements in auxiliary and state supply feeders were done.

In this endeavour Power Quality measurement of various household appliances, typical office

building, and distribution substations were also carried out. Broad observations in this regard

are presented in the following section.

7. Broad Observation based on Field Measurement

Power quality measurement in 175 cities / towns at various voltage levels covering

more than 500 feeders/points indicate presence of high content of voltage harmonics at 65

cities/towns, for duration ranging up to 4% of time. Transmission system as well as LT

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supply (415V) voltages (HV/EHV/UHV) and current were found to be rich in 3rd and 5th

harmonics respectively.

Voltage unbalance exceeding permissible limit (for short durations) was observed at

79 cities/towns during the field measurement. Instances of voltage sag/dip were also observed

during the measurement. Higher value of Flicker that gives an impression of instability in the

visual sensation were observed mainly in the LT supply at almost all the cities/town across

the country. Flicker observed in the transmission system at 220kV, 400 kV & 765kV level

was of very low magnitude.

Table 1: Overview of Power Quality Parameters observed across the country

S.No. Power Quality

Parameters

Northern

Region

Southern

Region

Western

Region

Eastern

Region

North

Eastern

Region

No. Of

Locations

Exceeding

Permissible

Limits

1 Voltage Sag 29 7 12 13 12 73

2 Voltage Harmonic 17 18 18 12 0 65

3 Unbalance 27 14 16 9 13 79

4 Current Harmonics 11 6 10 11 0 38

4 Voltage Swell 4 2 4 1 0 11

5 DC offset 4 3 2 1 0 10

6 Interruptions 0 3 3 2 0 8

Table 1 shows the number of locations identified to be critical with respect to various

power quality parameters. On the other hand, Power quality parameters measured at the

consumers ‘end, on common appliances used in the offices and homes show their non-linear

nature, which in turn reflects in the form of high content of harmonics. It has been observed

that these appliances draw current rich in odd harmonics such as 3rd, 5th, 7th, and so on in the

diminishing order of magnitude. Further, high content of harmonics were also observed in the

current/voltage of the supply feeder of offices and apartments along with large amount of

neutral current rich in harmonics. Other power Quality events like, Voltage Sag/Swell,

Unbalance etc. were also observed at the point of common coupling in the LT supply. An

overview of power quality parameters observed across different parts of the country is shown

in Table 1, Table 2 & Figure 10, which indicates that critical Power Quality Parameters are

voltage sag, harmonics, and voltage unbalance.

xiv

Figure 10: Region-wise Power Quality Parameters observed across the country

CEA has defined power quality standards for Harmonics, Unbalance and Voltage limits.

Therefore, these three parameters out of the various power quality parameters measured,

have been considered to classify power quality in various states of the country. Power quality

levels have been analyzed for above parameters by considering equal weightage for each

parameter and based on the results, states have been classified into two categories; Critical

and Non-critical as shown in the Power Quality map in Figure 11.

Table 2: Summary of Critical Power Quality Parameters

Sl. No. Region Name Critical Power Quality Parameter

1 Northern Sag, Voltage Unbalance

2 Western Harmonics

3 Southern Harmonics

4 Eastern Sag, Harmonics

5 North Eastern Voltage Unbalance, Sag

States where monitored power quality parameters exceeded the limits, have been

marked as critical areas, whereas states with less severity have been marked as Non-critical

as shown in Table 3.

Table 3: State wise Power Quality Severity Level

Sl No. State Power Quality Severity Index Remarks

1 Himachal Pradesh 0.667 Critical

2 J&K 0.667 Critical

3 Maharashtra 0.619 Critical

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4 Punjab 0.611 Critical

5 Assam 0.611 Critical

6 Gujarat 0.571 Critical

7 Chhattisgarh 0.556 Critical

8 Orissa 0.542 Critical

9 Telangana 0.500 Critical

10 New Delhi 0.500 Critical

11 Haryana 0.485 Non-Critical

12 Uttar Pradesh 0.422 Non-Critical

13 Bihar 0.407 Non-Critical

14 West Bengal 0.370 Non-Critical

15 Rajasthan 0.370 Non-Critical

16 Madhya Pradesh 0.361 Non-Critical

17 Tamil Nadu 0.333 Non-Critical

18 Goa 0.333 Non-Critical

19 Mizoram 0.333 Non-Critical

20 Nagaland 0.333 Non-Critical

21 Manipur 0.333 Non-Critical

22 Meghalaya 0.333 Non-Critical

23 Tripura 0.333 Non-Critical

24 Uttrakhand 0.333 Non-Critical

25 Andhra Pradesh 0.333 Non-Critical

26 Arunachal Pradesh 0.333 Non-Critical

27 Karnataka 0.278 Non-Critical

28 Kerala 0.250 Non-Critical

29 Jharkhand 0.083 Non-Critical

30 Sikkim 0.000 Non-Critical

Note:

Power Quality Severity Index: Number of Power Quality Parameters exceeding the limits at

different voltage level in a city/town, normalized over total number of power quality

xvi

measured and averaging all normalized measurements across the state. (Detail calculation is

given in section 5.12 of this report).

Figure 11 : Power Quality Map of India

xvii

8. Brief on Field measurement of Power Quality Parameters

Power Quality Measurement at EHV Grid Substations

765 kV level

At 765 kV level Power Quality measurement was carried out at 26 cities/towns. Based

on measurement, it can be seen that average THD observed in voltage waveform at 765 kV

voltage level varies from 0.44% to 1.17% against the limit of 1.5%. Average THD in Voltage

is shown in Figure 12.

Figure 12: THD in Phase Voltages at 765 kV Level

xviii

Figure 13: Average Voltage Harmonic Spectrum at 765 kV across India

Figure 14: Duration curve of Voltage THD at 765kV across India

Average voltage Harmonic spectrum at 765kV and its duration curve is shown Figure 13 and

Figure 14 respectively. It can be observed that most dominant voltage harmonic observed at

765 kV is 5th harmonic and for a very short duration i.e. 0.63% of time THD goes beyond 1%

as shown in duration curve at Figure 14. High THD level were observed at Gaya, Moga,

Solapur, Raichur, Jabalpur area as shown on all India map in Figure 12.

400 kV level

At 400 kV level Power Quality measurement was carried out at 144 cities/towns.

Based on measurement, it can be seen that average THD observed in voltage waveform at

400 kV voltage level varies from 0.11% to 3.3% against the limit of 2%. It goes beyond 2%

only for a short duration i.e. 3.6% of time as shown in duration curve at Figure 15. High THD

was mainly observed at Kala, Vapi, Navsari, Magarwada, Udupi, Chamba, Panchkula,

Meerut, Arasur, Bhadrawati, Agra, Keonjhar, Rengali out of the 144 cities/towns where

Power Quality Measurement were done at 400kV. Typical Average Voltage Harmonics daily

Trend shown in Figure 16 indicates that most dominant harmonics at this voltage level are 3rd

& 5th harmonics.

xix

Figure 15: Duration Curve-400kV Voltage THD


Figure 17 shows that the average THD at 400 kV level in the Indian Power System. The

nodes which are more meshed up with multiple connections are comparatively stronger (e.g.

central India) and hence show less distortion in voltage waveform.

Average Voltage unbalances observed in the voltages at 400 kV varies from 0.04% to 5.00%.

xx


220/230kV level

At 220/230 kV level Power Quality measurement was carried out at 111 cities/towns.

It can be seen from the duration curve of average THD in voltage at this level goes beyond

prescribed limit of 2.5% for a very small duration i.e. 1.56 % of time as shown in Duration

Curve (Figure 20).

High content of harmonics were mainly observed at Abdullapur, Mapusa, Khamam,

Baripada, Vapi, Chinhat, Tepla, Lalpur areas as shown in Figure 18 as well as at the stations

where high content of harmonics were observed at 400 kV THD in Phase Voltages at 400 kV

Level.

xxi



Typical Average Voltage Harmonics spectrum is shown in Figure 19 which indicates

that most dominant harmonics at this voltage level is the 3rd harmonics. It has been found that

average THD in voltage at 220 kV varies from 0.1% to 2.9% against the limit of 2.5%.

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Figure 20: Duration Curve-220kV Voltage THD

33 kV & 415V LT Supply

Observation based on Power quality Measurement at 33 kV level Feeder indicate that

relatively high content of odd harmonics of the order of 3rd, 5th, 7th are present in the voltage

and current waveforms. Overall average THD is found to be of the order of 1-2% in Voltage

as well as current at 33kV level.

Observation based on Power quality Measurement at LT supply (415 Volts) level

indicate that relatively high content of odd harmonics of the order of 3rd, 5th, 7th , 13th are

present in the voltage waveform. Average Voltage THD is found to be of the order of 1%-2%

in 415V LT supply, but it goes up to as high as 15% for short durations as shown in Figure

21.

Figure 21: Overall Duration Curve for Average THD at 415V

The measurements have been taken at LT/Auxiliary supply at more than 90 different

cities/towns. Similarly Flicker (Short Term-Pst & Long Term -Plt) values have been

observed to be more than 2 while the limits for Pst & Plt are 1 and 0.65 respectively.

xxiii

9. PQ measurement on commonly used appliances

To understand the contribution of consumer appliances in the prevailing electrical

pollution observed in the power system i.e. Power Quality parameters were measured for

various commonly used household & office use appliances. It can be observed that most of

the commonly used Information Technology (IT) related appliances, such as Laptop, Mobile

charger, Television, desktop PC and other household appliances like LED light, micro wave

oven, UPS etc. draw discontinuous current from the supply only for a fraction of each half

cycle. Voltage and Current waveform & harmonics spectrum of such a typical appliance is

shown in Figure 22. It can be seen that it contains large current harmonics.

Figure 22: Typical Voltage and current wave form of a non-linear single phase appliance and

harmonic content of the current drawn.

The main source of such type of harmonic current are due to the phase angle

controlled rectifiers and inverters, often called static power converters and Switched Mode

Power Supplies used in various appliances such PC, Printers, Televisions, Mobile Charger

etc. Power factor of various loads are also poor, thus drawing more energy affecting

equipment efficiency & increasing system loss. Summary of observation made on various

commonly used appliances are given in Table 4. It can be seen that most of these appliances

draw currents rich in harmonics, which contains mainly odd harmonics in the diminishing

order of magnitude. Most dominant among them is 3rd order harmonic, which needs to be

controlled.

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Table 4: Summary of power quality measurements on common appliances

Device

THD

(Current)

%

Most

Dominant

Harmonic

Order

Other

Harmonics

Input

Power Output

Power

(Watt) Power Factor

(Volt-

amp)

Laptop 179.1 3 5, 7, 9, 11 77.5 VA 36.4W 0.47 Leading

Mobile Charger 172.1 3

5, 7, 9, 11,

13 12.4 VA 6.1W 0.49 Leading

LED Bulb (12W) 164 3

5, 7, 9, 11,

13 21.1 VA 10.6 W 0.5 Leading

Desktop Monitor (TFT) 161.9 3

5, 7, 9, 11,

13 24.5 10.1W 0.41 Leading

Small Tube light 129.8 3

5, 7, 9, 11,

13 11.6 VA 6.6W 0.57 Leading

Computer with TFT Monitor 91.2 3

5, 7, 9, 11,

13 204.2VA 157.2W 0.76 Lagging

Computer with CRT Monitor 75.4 3

5, 7, 9, 11,

13 138.2VA 103W 0.75 Lagging

Printer under idle condition 40.2 3

5, 7, 9, 11,

13 108.6VA 76.9W 0.71 Leading

Printer (during warm-up) 40 3

5, 7, 9, 11,

13

Upto

1.14kVA

Upto

1.17kW

0.3

to 1 Leading

Oven 32 3 5,7,9 1470VA 1377.5W 0.99 Lagging

LED Bulb (2.5W) 31.3 3

5, 7, 9, 11,

13 10.5VA 2.5W 0.24 Leading

LED Bulb (7W) 16.1 3 5, 7, 9, 11 7.5VA 7.1W 0.95 Leading

Note: Above Mentioned Observations are typical & indicative in nature

10. Power Quality Measurement in Typical Buildings

Power Quality Measurements were carried out on LT feeders of a typical office

building & two different residential complexes. It is observed that voltage & current in all the

three (3) phases of these feeders’ contain odd harmonics of the order of 3rd, 5th, 7th, 11thand so

on. Power Quality events like sag, swell, transients, interruptions, flicker etc. were also

observed during the measurement period. Among the various harmonics present, 3rd

harmonic current was most dominant followed by 5th, 7th, 9th, 11th etc. Even harmonics were

mostly absent. Large neutral current and high unbalance in the phase currents were also

observed. Sometimes, DC component were also observed in the phase and neutral current.

High content of THD as well as individual Harmonics (3rd, 5th, 7th, 11th etc.) in the neutral

voltage & current indicates the presence of large volume of non-linear loads in the office.

It is observed that the current in lighting feeder consists of various odd harmonics like, 3rd,

5th, 7th, 9th, 11th, 13th and so on whereas UPS current mainly contains characteristics

harmonics of rectifier / converter like 5th, 7th, 11th, 13th etc.

xxv

11. Mitigation of Power Quality Issues

Power quality problems exist in every part of the power supply chain and therefore

solutions needs to be deployed across the chain. Mitigation methods/ technology vary in

different segments of transmission, distribution and at the end-use equipment as shown in

Figure 23.

Figure 23: Solutions for power quality problem

By using proper interface devices, power quality issues at the load end may be

minimized. Solutions are generally defined in two (2) categories; corrective solutions and

preventive solutions. Corrective solutions are the techniques to overcome the existing

problems. Use of active and passive filters, dynamic compensators, and reconfiguration of

the feeders or reallocation of capacitor banks etc. are some examples. Whereas preventive

measures aim to avoid power quality issues during installation of the equipment itself. Proper

design of the equipment and control system protect the equipment from power quality

problems and also eliminate disturbance generated within the equipment. Some of the

mitigation devices are described in the following section:

Series Capacitor

Series Capacitors are generally applied to compensate the inductance of long

transmission lines, in order to reduce the line voltage drop, improve its voltage regulation,

minimize losses by optimizing load distribution between parallel transmission lines, and to

increase the power transfer capability. Series capacitors positively affect the voltage and

reactive power balance.

xxvi

Shunt Capacitors

Shunt capacitors are usually called “power factor correction capacitors”. They are used at all

voltage levels from end-user utilization to extra high voltages. Shunt capacitors, either at the

customer location for power factor correction or on the distribution system for voltage

control, alter the system impedance variation with frequency.

Utilities use shunt capacitors at distribution and utilization voltage levels to provide

reactive power near the inductive loads that require it. This reduces the total current flowing

on the distribution feeder, which improves the voltage profile along the feeder, release

additional feeder capacity and reduces losses.

Static Var Compensator (SVC)

Static Var Compensator (SVC) provides fast reactive power compensation in power

system using combination of capacitors and reactors to regulate the voltage. These are

primarily used to mitigate voltage fluctuation, dynamic voltage support as well as the

resulting flicker. As an automated impedance matching device, they have the added benefit of

bringing the system power factor close to unity. Therefore, SVC is usually installed near high

and rapidly varying loads, such as electric arc furnaces, welding plants and other industries

prone to voltage fluctuations and flicker.

STATCOM

STATCOM or Static Synchronous Compensator is a shunt device, which uses force-

commutated power electronics (i.e. GTO, IGBT) devices/switches to control power flow and

improve transient stability on electrical power networks. The STATCOM basically performs

the same function as the static var compensators but with additional advantages.

STATCOM is composed of the following components:

(i) Voltage-Source Converter (VSC):

(ii) DC Capacitor

(iii)Inductive Reactance (X)

(iv) Harmonic Filters

D-STATCOM

A D-STATCOM (Distribution Static Compensators) is a fast-response, solid-state

power controller that provides power quality improvements at the point of connection to the

http://www.powerqualityworld.com/2011/09/static-var-compensator-svc.html

xxvii

utility distribution feeder. It is the most important power quality controller for the distribution

networks. It has been widely used for precisely regulate the system voltage and /or for load

compensation. It can exchange both active and reactive power with the distribution system

by varying the amplitude and phase angle of the voltage of the VSC (Voltage Source

Converter) with respect to the PCC voltage, if an energy storage system is included into the

DC bus. However, a capacitor supported D-STATCOM is preferred for power quality

improvement in the currents, such as reactive power compensation for unity power factor or

voltage regulation at PCC, load balancing and neutral current compensation. These

compensating devices are also used to regulate the terminal voltage, suppress voltage flicker,

and improve voltage balance in three phase systems. One of the major factors in advancing

the D-STATCOM technology is the advent of fast, self-commutating solid-state devices.

With the introduction of IGBT (insulated gate bipolar transistor), the D-STATCOM

technology has got a real boost.

Dynamic Voltage Restorer (DVR)

To mitigate the voltage based power quality problems such as spikes, surges, flickers,

sags, swells, notches, fluctuations, voltage imbalance, waveform distortion, etc. in the

distribution system solid-state series compensators (SSC) and dynamic voltage restorer are

commonly used. These active series compensators are recently reported with some

modifications as cost-effective filters with series active power filters to eliminate harmonic

currents in voltage-fed nonlinear loads and with shunt passive filters to eliminate harmonic

currents in current fed non-linear loads. These compensators are based on the principle of

injecting a voltage in series with the supply. This compensator inserts a voltage of required

waveform so that it can protect the sensitive consumer loads from supply disturbances such

as sag, swell, spikes, notches, unbalance, harmonics, and so on in supply voltage.

UPQC (Unified Power Quality Compensators)

A UPQC, which is a combination of shunt and series compensators, is proposed as a

single solution for mitigating multiple power quality problems. The power circuit of a UPQC

consists of two VSCs connected back to back by a common DC link. The shunt devices

known as DSTATCOM provides reactive power compensation along with load balancing,

neutral current compensation, and elimination of harmonics (if required) and is positioned

parallel to consumer load. The series device known as DVR keeps the load end voltage

insensitive to supply voltage quality problems such as voltage sag/swell, surge spikes,

xxviii

notches, or unbalance. The DVR injects a compensating voltage between the supply and the

consumer load, and restores the load voltage to its reference value.

Harmonic Filters

Harmonic Filters are used to mitigate the power quality problem known as harmonic

waveform distortion. Consequently, they minimize the thermal and electrical stress on the

electrical infrastructure, eliminate the risk of harmonics-related reliability issues and allow

for long-term energy efficiency and cost savings. Harmonic filters are classified as following:

a) Passive Harmonic filters: Passive harmonic filters provide low impedance path to

the harmonic frequencies to be attenuated using passive components (inductors,

capacitors and resistors). It absorbs the harmonic current to which it is tuned and

filters it out of the system.

b) Active harmonic filters: Active Harmonic Filters monitor the non-linear load and

dynamically provide controlled current injection, which cancels out the harmonic

currents in the electrical system. They also correct poor displacement power factor by

compensating the system’s reactive current.

c) Hybrid harmonic filter: It is a combination of both passive & active harmonic

filters.

12. International Experience

The availability of sophisticated and sensitive appliances at consumer end has led

demand for higher levels of power quality across the world. To meet these needs, various

approaches have been followed by utilities worldwide. Some utilities have set up premium

power quality contracts for their customers, whereas some identify the additional costs

involved in providing the services and bill the customer for it. Experience across the world in

this regard is described in the following section:

EdF, France:

EdF, France has set up a number of electricity supply contracts and services for large

and medium customers to ensure higher level of power quality. In 1994, EdF began to use the

“Emeraude” contract as an experiment for 6,000 customers. Presently, EdF offer their

customers with customized contracts of assigned voltage quality levels. If the customer

claims for better contractual levels than the normal ones, they can avail the same by paying

extra charges. In these contracts, consumers are required to limit the maximum electrical

emission level to the system.

xxix

Detroit Edison Company (DEC), USA

DEC offers a special manufacturing contract (SMC) with premium power quality for

consumers in their region. The SMC specifies that the consumers are compensated when

certain level of predefined parameters have been exceeded. On the other hand, DEC also

offers special interruptible rates to residential, commercial and industrial customers.

Customers get discounted electricity prices in return for permission to occasionally interrupt

electrical service.

National Electricity Regulator (NER), South Africa

National Electricity Regulator (NER) has mandated that utility shall be responsible

for the power quality levels delivered to all of its customers and independent power producers

connected to its network. Utility shall implement suitable contracts with all customers

connected in its network for various power quality parameters including voltage quality,

voltage dips and harmonics.

United Illuminating Company, Connecticut, USA

This utility uses extensive measurements of power quality parameters on the medium

voltage network to ensure quality in power supply. These measurement data are used to set

performance benchmarking. Measurement data is not only used for focusing on customer

needs, but also for planning long-term improvements in the grid. They inform potential

customers about the number of voltage dips expected in different parts of the power network

and accordingly sensitive customers choose appropriate place to setup their establishment.

Netherland

Figure 24: Classification of Power Quality Levels in different areas

Distribution network operators in the Netherlands have initiated an easy classification

system based on labeling the power quality on a scale of normalized power quality

xxx

characteristics. To keep the labeling meaningful and transparent, aggregation of large

amounts of measured data is done to have single measure of quality as shown in Figure 24.

Areas with +ve normalized value of Power Quality are considered either normal or

high in quality depending on its value. On the other hand areas with –ve normalized value of

Power Quality are considered poor in quality.

Norway

In 1995 mandatory reporting of interruptions greater than 3 minutes was added in the

regulation of quality of supply that began in 1991 and about 179 network companies were

required to report key figures on voltage quality. Subsequently, in 2005 the Norwegian

Water Resource and Energy Directorate (NVE) put into force “Regulations relating to the

quality of supply in Norwegian power system”. This regulation applies to all network voltage

levels.

PowerGrid Ltd., Singapore

PowerGrid Ltd, a subsidiary of Singapore Power Ltd, responsible for the transmission

and distribution of electricity at 400kV, 230kV, 66kV, 22kV and 6.6kV levels has put up a

comprehensive power quality improvement plan to meet the needs of the high–tech

industries. The plan covers initiatives including Power Quality Monitoring System,

application of mitigation technologies for voltage dip ride-through, network enhancement,

cost-effective mitigation devices, condition monitoring, cable damage prevention etc.

India

The Electricity Act (EA), 2003, explicitly specifies the responsibility to supply quality

power to end consumers. The technical standards for construction of electrical plants and

electric lines and connectivity to the grid have been specified by the Central Electricity

Authority (CEA). Grid code has been notified by the Central and State electricity

Commissions for supply code and standard of performance regulations as per Electricity Act.

Some SERCs have notified distribution codes such as Gujarat Electricity Regulatory

Commission has notified ‘Gujarat Electricity Distribution Code’ and Orissa Electricity

Regulatory Commission has constituted a PQ monitoring committee to oversee the quality of

Supply.

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13. Investment Required to Improve Power Quality

An estimate of investments required to improve the Quality of Power Supply by

installing Power-Quality interface devices in the distribution network, is proposed in the

following section. As mentioned in section 5.12 of this report, ten (10) different states (shown

in have been identified as critical with respect to Power Quality in India. The connected load

across different categories of consumers in these states is shown in Table 6. All these loads

are not equally sensitive to Power Quality parameters. Considering a certain proportion of

loads, being relatively more sensitive to Power Quality; deployment of mitigating measures

can be planned in phased manner for these loads; and initially, 50% of connected load in

Industrial, Commercial & Domestic domains may be selected for Power Quality

improvement.

Table 5: State-Wise connected loads identified for Power Quality Improvement*

State Industrial Load

(GW) Domestic Load

(GW) Commercial Load

(GW) Total (GW)

Himachal Pradesh 1.79 2.63 0.56 4.98

Jammu & Kashmir 0.58 1.06 0.24 1.88

Punjab 7.73 10.14 3.13 21.00

Delhi 1.91 10.68 7.41 20.00

Gujarat 13.55 12.09 5.29 30.93

Chhattisgarh 2.27 1.63 0.94 4.85

Maharashtra 23.81 25.30 10.46 59.56

Andhra Pradesh 34.95 36.26 12.50 83.71

Odisha 2.61 4.37 0.82 7.80

Assam 0.99 2.14 0.53 3.65

Total 90.2 106.3 41.8 238.3

Table 6: Loads identified for Power Quality Improvement*

(*Source: CEA Report) Note: All the investments calculated hereafter are based on the above segregation

Type of Load Various Types

of Connected

Load*

Proportion assumed to

be sensitive towards

Power Quality

Quantum of connected

Load considered for PQ

improvement

Industrial 90.2 50% 45 GW

Domestic 106.3 50% 53 GW

Commercial 41.8 50% 20 GW

Total 238.3 GW 118 GW

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Power Quality interface devices as described in previous sections can be broadly classified

under following two major categories:

1. Voltage sag & Interruption protection devices such as dynamic Voltage Restorer

(DVR), Voltage Sag Corrector, etc.

2. Reactive Power & Harmonic compensation devices (PQ conditioning devices), Active

Power Filters (APF), Automatic Power Factor Controller (APFC), SVG (Static Var

Generator), D-STATCOM, etc.

The cost of these Power Quality improvement devices usually depends on load

requirement in terms of kW or MW. Based on a market survey, it has been found that cost of

such devices (at 415V) may vary from Rs. 4,000/Amp to Rs. 17,000/Amp. Market survey

also reveals that there are very limited domestic manufacturers of Power Quality mitigating /

monitoring devices. Even if some types of mitigating / monitoring devices are available, their

size (rating) and features are limited. However, there are several international manufacturers

in this field. Above mentioned cost is a rough estimate of typical such devices. Estimated

investment has been worked out assuming that the PQ conditioning device would cost around

Rs.10,000 per Amp. (Rs. 2,100 per kW of connected load). Detailed calculations are given in

chapter 7.

Installation of Power Conditioning devices at the LT level (415V) supply is

considered. It has been assumed that the each ‘Power-Conditioning’ device would improve

the power-factor from 0.8 to 0.9 and also mitigate the current harmonics of the order of 20

Amps at LT level (415V). Based on the field measurement it has been observed that the net

harmonic current is of the order of few tens of Amp in LT supply.

There are about 15 Lakh total industrial drives of various sizes operating in the country.

The VFDs/ASDs used in industries inject distortions in the Grid, which may cause voltage

sags/swells, Unbalance, Harmonics etc. It is proposed to install Hybrid Active Filters (Active

Power Filter + 5 p.u. line reactor) to mitigate Harmonics at the VFDs/ASDs in industries. A

line reactor along with the Harmonic mitigating device reduces the rating requirement of the

Harmonic mitigating device for a given load.

Along with the Power conditioning devices at various strategic locations, it is also

necessary to install Power Quality monitoring devices, which are available in the market in

the names like Power-Quality Analyzer, Power Quality Logger, Power Quality Monitor etc.

xxxiii

It is proposed to install one monitoring device for every 50MW of connected load out of

118GW load identified in Table 6.

Considering all the investments mentioned above, the total estimated investment required

during initial phase for Power Quality improvement for the loads identified in Table 6 is

about Rs. 24,840 Cr. as shown in Table 7.

Table 7: Estimated Investments for Power Quality Improvement

Sl No. Load Category Load Considered for PQ

Improvement (GW)

Rate

Rs per KW

Estimated Investment

(Rs. Cr.)

A. Power Conditioning Device

(Such as DSTATCOM, SVG, APF, DVR, Active Power Filter, etc.) 1 Industrial 45

2,100 9,450

2 Domestic 53 11,130 3 Commercial 20 4,200

Sub-Total 24,780

Sl

No.

Number of Power Quality Monitoring

devices required

Rate

Rs per Device


(Rs. Cr.)

B. Power Quality Monitoring Device

(Such as Power Quality Analyzer, Power Quality Logger etc.) 1 1180 5,00,000 59

Sub-Total 59

14. Way forward: Actions required for Power Quality improvement

This report has highlighted the importance of power quality while building an insight upon

power quality standards, pan India power quality status based on primary measurement, the

ill effects of poor power quality and possible mitigating measures required for the same.

Power Quality Measurements have been done on various voltage levels ranging from

distribution (415 V) to EHV (765 kV) throughout India.

These measurements were done for 6 to 24 hours on each feeder in a non-simultaneous

manner. From the measurements, it was observed that voltage harmonics are high in certain

pockets of the country. The higher magnitude of Voltage Harmonics in these pockets

necessitates the need for corrective measures to be taken.

High current distortions have been observed invariably at all voltage levels. Various

challenges and threats posed by poor power quality including harmonics have been discussed

Total Investment (A+B) Rs. 24,840 Cr.

xxxiv

in this report. Prudent mitigating measures to address these challenges, viz. STATCOM,

passive harmonic filters, active power filters, DVR, power factor conditioners etc. have been

discussed and suggested.

Installation of these devices is to be done at locations which may be decided by extensive

system studies. Sizing of these power quality devices also need to be carried out through

meticulous data analysis and simulation studies. Further course of action imperative to ensure

a good quality power at the national level is as follows:

Identification of critical nodes with critical level of electrical pollution.

Detailed measurement of power quality for longer duration and further analysis of

data.

Development of infrastructure to periodically monitor the Power-Quality parameters

across the Grid at all the Voltage Levels, including distribution network.

Assessment of various power quality improvement devices depending upon issue,

ratings, voltage level, economic considerations etc.

Development of regulatory framework and economic model to facilitate the

deployment of mitigating solutions.

Enforcement of regulations for maintaining power quality parameters for various

stake holders.

Simulation based study for further improvement at varying voltage level.

To ensure Quality Supply in the entire Power System, any single stakeholder can’t be

made responsible. Since Power-Quality has a very broad spectrum, all the stakeholders in the

Power Supply Value chain are expected to contribute in a collaborative manner to ensure

high quality of power to end consumers. Various actions that need to be taken by different

stakeholders are enlisted below:

1. Necessary standards shall be formulated / updated under the emerging scenario of

large penetration of non-linear loads, volatile renewable generation capacity addition,

increasing inverter penetration & stringent quality requirements by various categories

of load.

2. Utilities need to strengthen/upgrade their network to ensure high quality of power.

3. Manufacturers need to produce electrical / electronic appliances/ gadgets meeting the

standards and end consumer needs.

xxxv

4. Power conditioning equipment manufacturer need to produce devices that would

facilitate maintaining required power quality.

5. Adequate compensation to utilities for ensuring high quality power through special

tariff /penalty schemes.

6. Awareness about Power Quality among various stakeholders.

7. Capacity building and training program need to be conducted among various

stakeholders.

8. Monitoring / control of Power Quality at various stages of power supply value chain.

9. Establishment of National and State level Organization for certifying Power Quality.

10. Use of Power Quality complied / conditioning equipment by the end consumers.

11. Research, development& demonstration work in Power quality industries and

academic institutions.

12. Regulations for measurement of PQ parameters at different voltage level by each

utility/ major establishment periodically.

15. Roles and Responsibilities of various stakeholders:

Some of the suggested roles and responsibilities along with related agencies proposed

are as follows:

S.No. Activities Roles/ Responsibilities

1. Development of Power Quality Standards for Utilities and

the End-Users.

CEA/MoP/

NITI Ayog/BIS

2.

Specify electrical/electronic equipment with the necessary

resilience to Power Quality related events (e.g., Voltage

Sag, Interruptions etc.)

BIS

3. Ensure Reliable & Quality Supply Genco/CTU/STU/

DISCOM /Utilities

4. Provision of special tariff/penalty for companies/utilities/

individuals contributing to power quality. CERC/SERC

5. Regulations for periodic measurement of PQ parameters at

different voltage level by each utility CERC/SERC

6.

Design, development & installation of Power

Conditioning devices like harmonic filters, DVRs, D-

STATCOMs, APFC etc. at strategically identified nodes

in the Grid (MV and LV nodes)

Transco/ DISCOM /

Manufacturer

7. Bring awareness about power quality amongst the

stakeholders.

BEE/State Govts./

Discom/MoP/STUs/

CTU

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S.No. Activities Roles/ Responsibilities

8.

Conduct a nation-wide Power Quality Survey to reveal the

impacts of Poor Power Quality (e.g., Cost of Interruptions,

Sags, Harmonics etc.) to various stakeholders especially

Industries).

BEE/MoP/ DISCOMs

9. Use of Power Quality complied/conditioning equipment

(especially in industries/ domestic areas).

SERC/Discom/

End Users

10. Setting up PQ institutes at National Level for knowledge

dissemination, awareness and R&D activities

MoP/ State Govt/

NITI Ayog

11. Capacity Building MoP/State/DISCOM

Utilities/Genco/Transco

Discom

Note: This report is an attempt to study and analyze the impact of various power quality

parameters in the power system at various voltage levels in different towns and cities across

the country. It includes the baseline data about power quality parameters in different places.

However, this needs to be periodically updated and reviewed. Inputs / feedback from all

stakeholders would help in further improvement and making this report more pragmatic.

Swachh Power

1

Chapter-1

1. Power Quality and its

Significance Traditionally, the power system was simple and unidirectional; the flow of electricity

(power) used to be from source (generator) to sink (load) only. Power was generated in bulk

using conventional resources and then transmitted, distributed and consumed by end users as

load. Availability of power had more concern than the quality and therefore the target used to

be “to keep the lights On”, without taking reliability and quality of power into account. Now

the scenario is gradually changing.

Modern power system has many types of generation resources including renewables (which

have specific characteristics of variability and intermittency) connected to the grid through

power conditioning equipment. Transmission systems have become multifaceted with

technologies like UHVAC / HVDC systems, FACTS devices etc. Distributed generation and

battery storage systems have been connected with distribution system using inverters.

Loads at consumer end have also changed their characteristics. Most of the electronic

devices being used by the consumers are sensitive and non-linear loads. Cumulatively all such

changes in power system have affected quality of the power supply. At the same time

consumers’ awareness, requirement and aspirations for quality power in terms of continuity,

sinusoidal shape and specified limits etc. are increasing. Hence, Power Quality has now

become one of the major concerns for power system stakeholders.

1.1 What is Power Quality?

The Power Quality (PQ) aspect in the Power System is largely ignored, often not

understood and so is rarely demanded or enforced. Our industry does not readily recognise the

impacts of a poor Power Quality environment since the costs are not captured. There is a

readiness to invest in energy efficiency, where the return is more easily visible, and tendency

to ignore PQ, where the idea of losses is nebulous or non-existent. But recently the awareness

of customers towards power quality problems has increased tremendously because of the

following reasons:

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The customer’s equipment have become much more sensitive to power quality problems

than these have been earlier due to the use of digital control and power electronic

converters, which are highly sensitive to the quality of supply and other disturbances.

Moreover, the industries have also become conscious about loss of production due to power

quality issues.

The increase in use of solid-state controllers in a number of equipment with other benefits

such as decreasing the losses, increasing overall efficiency, and reducing the cost of

production has resulted in the increased harmonic level, distortion, notches, and other

power quality problems. Typical examples are adjustable speed drives (ASDs) and energy

saving electronic blasts, which have substantial energy savings and some other benefits;

however, they are the sources of waveform distortion and much more sensitive to the

number of power quality disturbances.

The awareness of power quality problems has increased among the customers due to direct

and indirect penalties enforced on them, which are caused by interruptions, loss of

production, equipment failure, standards, and so on.

The disturbances to other important appliances such as telecommunication network, TVs,

computers, metering systems, and protection systems have forced the end users to either

reduce or eliminate power quality problems or dispense the use of power polluting devices

and equipment.

Distributed generation using renewable energy and other local energy sources has increased

power quality problems as it needs, in many situations, solid-state conversion and

variations in input power, which in turn adds new problems of voltage quality.

Power quality is a measure of the fitness of electrical power fed into the consumer devices.

The term is used to describe electric power that drives an electrical load and the load's ability

to function as intended. Without the quality power, an electrical device (or load) may

malfunction, fail prematurely, become economically unviable due to losses or not operate at

all. There are various parameters which are related to quality of power and deviation in their

value from reference results into poor quality of power.

IEC 61000-4-30[5]defines power quality as “The characteristics of the electricity at a given

point on an electrical system, evaluated against a set of reference technical parameters”.

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As per “Economic Framework for Power Quality”, CIGRE/CIRED, Joint Working Group

C4.107[2],“Power quality” is the term generically used to describe the extent to which the

electrical power available at the point of use is compatible with the needs of the load equipment

connected at that point.” The lack of compatibility between electrical power supply and

sensitivity of load is termed as a Power Quality problem.

1.2 Significance of Power Quality

Theoretically Power Quality issues have been studied and analyzed for long. However, with

changing pattern of loads as well as generation, “Power Quality” (PQ) no more remains a

theoretical concept. Rather, it has become a critical concern incurring high losses & damages

to equipment. Hence, PQ measurement and mitigation initiatives are being taken up globally

by utilities.

Today, consumers are becoming more & more aware and concerned regarding PQ issues

and it is found that complaints on PQ related disturbances (for example: harmonics, voltage

dips, flicker, interruptions, voltage unbalance etc.) are increasing day by day due to resultant

deficiency in performance of their appliances / equipment. It is observed that almost 70% of

the PQ disturbances are originated at the customer’s premises while 30% are in the network

side [Emanuel & McNeil, 1997]. Voltage sags (dips) and swells, transients, over-voltages (due

to capacitor switching), harmonics, interruptions, voltage unbalance and grounding related

problems are the most common PQ complaints among the consumers.

A PQ campaign was conducted by the Leonardo Power Quality Initiative (LPQI)[23] among

various customers in the EU-25 countries in 2004. It emerged that on average the absolute share

of impacts of power quality and reliability related problems are due to voltage dips (23.6%),

short interruptions (18.8%), long interruptions (12.5%), harmonics (5.4%), transients & surges

(29%) and other PQ related problems (10.7%).

As mentioned above, consumers are nowadays not only concerned with the availability of

power but also with the quality of power supply. In line with this, several standards and

regulations are being formulated and implemented by the statutory authorities, regulatory

bodies, for utilities as well as consumers.

In Europe, the quality of electricity that is provided by a grid operator has to comply with

reference parameters set in the European standard EN 50160 and other specific standards or

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the national grid codes. In India, CEA has stipulated limits for some of the PQ phenomena [8]

like voltage harmonics, over voltage, under voltage, voltage / current unbalance etc.

1.3 Reasons of poor power quality:

There are number of reasons for the pollution of the AC supply systems, including natural

ones such as lightening, flashover, equipment failure, and faults (around 60%) and forced ones

such as voltage distortions and notches (about 40%). A number of customer’s equipment also

pollute the supply system, which may result in failure or mal-operation of customer’s

equipment and also pollute the supply system as they draw non-sinusoidal current and behave

as non-linear loads.

Power quality is quantified in terms of voltage, current, or frequency deviation of supply

system, which may result in failure or mal-operation of customer’s equipment. Typically, some

power quality problems related to the voltage at the point of common coupling (PCC) where

various loads are connected are the presence of voltage harmonics, surge, spikes, notches,

sag/dip, swell, unbalance, fluctuations, glitches, flickers, outages, and so on. These problems

are present in the supply system due to various disturbances in the system or due to the presence

of various non-linear loads such as furnaces, uninterrupted power supplies (UPS), modern

electronic equipment and adjustable speed drive (ASDs). However, some power quality

problem related to the current drawn from the AC mains are poor power factor, reactive power

burden, harmonic currents, unbalance currents, and an excessive neutral current in polyphase

system due to unbalancing and harmonic currents generated by some non-linear loads. Quality

of power may be affected due to number of reasons associated with source of power as well as

type of load connected. Some of the reasons are discussed below.

1.3.1 Non-linear Loads

Electronic hardware are the major components of several industrial sectors such as

Information Technology sector, Telecommunication sector, Automobiles sector, Electronic

appliances sector, Special Medical equipment sector, etc.

But, almost all the Electronic equipment (Domestic,

Industrial & Commercial) like arc furnaces, variable speed

drives (VSDs), televisions, video and audio equipment,

multimedia devices, computers, heating ventilation and air

Almost all the Modern

Electronic Equipment are

highly non-linear!

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conditioning equipment with variable speed motor drives, electronic lighting products, telecom

equipment chargers etc. are all non-linear loads. A load is considered non-linear if its

impedance changes with the applied voltage. Due to changing impedance current drawn by the

non-linear load will not be sinusoidal even if it is supplied with a sinusoidal voltage. These

non-sinusoidal currents contain harmonics that interact with the impedance of the power

system to create voltage distortion that can affect both the network equipment and loads

connected to it. Non-linear loads create power quality problems like harmonics, low power

factor, noise etc. Figure 1-1 shows typical waveforms of linear & non-linear loads.

Figure 1-1: Typical linear & non-linear current waveforms

The number of non-linear loads in India is rapidly increasing. Desktop computers sales

have touched 11.31 million in 2012-13

and the sales have been increasing with

a CAGR growth rate of around 14%

(Figure 1-2).While the sales of tablets

has shown massive growth of more

than 400% from 2011-12 to 2012-13

(Figure 1-3).

Figure 1-2: Desktop Sales in India

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The growth in telecom products demand have been breathtaking and India is adding 2

million mobile phone users every

month!

In the industrial domain, there are

more than 15 Lakh LT motors used with

VSD/ASD applications, which are

highly non-linear. Moreover, nearly 5

Lakh such motors are getting added to

the Indian industry use, each year. Most of the Industrial Energy is used by motors which are

used for various applications like pumps, fans, compressors, Mechanical Movement, etc. All

these changes in the system have been introducing more and more of non-linearity in the

system, which will keep increasing.

1.3.2 Unstable Power System

Power system instability caused by inadequate planning, improper design of protection

systems, grounding related issues, aging of transformer & other equipment, overloading of

feeders & transformers etc. may result into various power quality problems. There may be

interruptions and voltage sags due to frequent tripping of feeders / transformers, voltage

unbalance due to unmatched impedances of lines / transformers and noise due to improper

grounding or arcing in the system.

1.3.3 Large Machines / Equipment

Switching on / off of large machines / equipment may cause some of the power quality

issues like voltage dip / swell, voltage fluctuations, flicker etc. Saturation of magnetic core of

induction motors, transformers, reactors and saliency of motors / generators causes harmonics

in the system. Inter-turn faults of motors / generators results into voltage/ current unbalances.

1.4 Impacts of Poor Power Quality

Poor Power Quality not only causes reduction in performance of the appliances / consumer

equipment but also results into increased losses in system, failure of equipment, additional

capacity requirement, financial loss etc.[4]. Some of the major impacts of poor power quality

are mentioned below:

Figure 1-3: Tablet Sales in India

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Increased losses in distribution system and electric machines, noise, vibrations, over-

voltages and excessive current due to resonance

Equipment overheating (transformers, motors, etc.) leading to their lifetime reduction

Failure of capacitor banks

Unexpected power supply failures (breakers tripping, fuses blowing, etc.)

Negative sequence current in generators and motors resulting in, especially rotor

heating, derating of cables, dielectric breakdown, signal interference and relay and

breaker malfunctions, false metering, interferences to the motor controllers and digital

controllers and so on.

Damage to sensitive equipment (PCs, production line control systems, etc.)

Electronic communication interference.

Increase in running costs and associated higher carbon footprint.

Penalties imposed by utilities for damaging power quality.

Interruption of processes for several hours, wastage of raw materials, etc. in automated

industrial processes, namely, semiconductor manufacturing, pharmaceutical industries,

and banking etc.

Impression of unsteadiness of visual sensation induced by a light stimulus whose

luminance or spectral distribution fluctuates with time (flicker).

These power quality problems have become much more serious with the use of solid state

controllers, which cannot be dispensed due to benefits of the cost and size reduction, energy

conservation, ease of control, low wear and tear, and other reduced maintenance requirements

in the modern electric equipment. Unfortunately, the electronically controlled energy-efficient

industrial and commercial electrical loads are more sensitive to power quality problems and

they themselves generate power quality problems due to the use of solid-state controllers in

them. In broad terms following are the disadvantages of poor power quality:

1.4.1 Loss to Consumer

Consumers are badly affected due to poor quality of power supply in the system. The

consumer appliances continue to operate even when the supply parameters are different from

the rated values to some extent. However, such operation is accompanied with extra losses

incurred. For example, motors and transformers get overheated due to harmonics in the supply

system. Motors draw extra current while operating at reduced voltages. Similarly, a three phase

system with unbalanced loading leads to extra copper losses due to significant neutral current.

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Further, all electrical equipment are designed to operate within a given range of input

parameters. Major variations in the supply parameters, if unaddressed by a protection or

monitoring scheme may cause degradation or complete failure of equipment. Figure 1-4 shows

some of the disastrous effects on equipment due to poor PQ phenomena.

Figure 1-4: Equipment failure due to poor power quality

Some of the inconveniences due to poor power quality and the affected consumer devices

are presented in Table 1-1.

Table 1-1: Inconveniences to consumers due to power quality problem

S.No. Perceived inconvenience Affected Devices Reported Power

Quality Problem

1 Computer lock-ups and data

loss

IT equipment(that are

sensitive to change in

voltage signal)

Presence of earth

leakage current

causing small voltage

drops in earth

conductors

2 Loss of synchronization in

processing equipment

Sensitive measurements of

process control equipment

Severe harmonic

distortion creating

additional zero-

crossings within a

cycle of the sine wave.

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S.No. Perceived inconvenience Affected Devices Reported Power

Quality Problem

3 Computer, electronics

equipment damage

Electronic devices like

computer, DVD player etc.

Lightning or a

switching surge

4 Lights flicker, blink or

dimming

Flickering, blinking or

dimming of lighting

devices, and other visual

screens

Fast voltage changes

leading to visible light

flicker, Eye fatigue

5

Malfunctioning of motors and

process devices. Extra

heating, decreased operational

efficiency and premature

aging of equipment

Motors and process

devices

Presence of voltage

and current harmonics

in the power supply

6 Nuisance tripping of

protective devices

Relays, circuit breakers

and contactors

Distorted voltage wave

form because of

voltage dip

7 Noise interference to

telecommunication lines

Telecommunication

system

Electrical noise

causing interference in

signals 1.4.2 Loss to Utility

Most of the power system equipment is designed for a balanced three phase operation.

However, unbalanced operation, harmonic currents etc. cause extra losses in the system.

Similarly over voltages, transients etc. cause additional stress to the insulation. Hence, to ensure

safe operation under poor power quality, utilities derate their equipment, which reduces

equipment capacity (sub-optimal utilization). K-rating of transformer is evaluated for the same

purpose. Puncturing of insulator due to overvoltage, transients, failure of power factor

correction capacitors due to harmonic currents and resonance etc. are some examples where

utilities face damages due to electrical pollution. Also the technical losses in transmission line

increases with unbalancing and presence of harmonic currents.

1.5 Financial Losses

The financial losses due to poor power quality can be categorized as following:

1.5.1 Direct Costs

The costs that can be directly attributable to the poor power quality are termed as direct

costs. These costs include the damage in the equipment, loss of production, loss of raw material,

salary overheads during non-productive period and restart costs. Sometimes, during the non-

productive period some savings are achieved, such as energy savings, which must be subtracted

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to the costs. Some power quality disturbances do not imply production stoppage, but may have

other costs associated, such as reduction of equipment efficiency and reduction of equipment

lifetime, which are also considered direct costs e.g. voltage sag, under frequency etc.

1.5.2 Indirect Costs

Due to some power quality disturbances and non-productive periods, customer may not be

able to accomplish the deadlines for some deliveries and loose future orders. Such costs

incurred are termed as ‘Indirect Costs’. Investments to safeguard equipment/facilities against

power quality problems may be considered as an indirect cost as well.

It can be summarized that power quality degradation results into enormous direct & indirect

losses. These costs are particularly huge for industries like semiconductors, electronics, steel,

paint, paper, packaging etc. and for services like financial institutions, banks, data centers, IT

services etc. Therefore improvement in power quality is utmost important for benefits of

consumers, utility and society as a whole.

***

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Chapter-2

2 Power Quality Parameters There are a number of power quality problems in the modern electrical/electronic

equipment/systems. These may be classified on the basis of events such as transient & steady

state, the quantity such as current, voltage, and frequency, or the load and supply systems. The

transient type of power quality problems include most of the phenomena occurring in transient

nature (e.g., impulsive or oscillatory in nature), such as sag(dip), swell, short-duration voltage

variations, power frequency variations, and voltage fluctuations. The steady-state types of

power quality problems include long-duration voltage variations, waveform distortions,

unbalanced voltages, notches, DC offset, flicker, poor power factor, unbalanced load currents,

load harmonic currents, and excessive neutral current.

The second classification can be made on the basis of quantity such as voltage, current

and frequency. Corresponding to voltage, these include voltage distortions, flicker, notches,

noise, sag, swell, unbalance, under-voltage and overvoltage; similarly for the current, these

include reactive power component of the current, harmonic currents, unbalanced currents, and

excessive neutral current.

The third classification of power quality problems is based on the load or the supply

system. Normally, power quality problems due to nature of the load (e.g., fluctuating loads

such as furnaces) are current harmonics, reactive power component of the current, unbalanced

currents, neutral current, DC offset and so on.

The power quality problems due to the supply system consist of voltage and frequency

related issues such as voltage distortion, unbalance, sag, swell, flicker and noise. These may

also consists of combination of both voltage-and current based power quality problems in the

system. The frequency related power quality problems are frequency variation above or below

the desired value. These affect the performance of a number of loads and other equipment such

as transformers in the distribution system[9].

Subsequently, it can be said that, “Continuous availability of balanced three phase

power supply of perfect sinusoidal shape, rated voltage and rated frequency optimized to

perform real work implies a good quality power.” Any deviation from the above statement

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represents a power quality problem. Based on the parameters deviated, the power quality

problems may be derived as shown in Table 2-1.

Table 2-1: Power Quality problems based on parameters deviated

Desired Parameters Power Quality Problem resulted due to

deviation

Continuous Availability Interruptions, Black out, Brown out, Outage

Balanced three phase Voltage unbalance

Perfect sinusoidal shape Harmonics, Inter-harmonics, Notch / Spike,

Transients, Noise etc.

Rated Voltage Over voltage, Under voltage, Sag / Dip,

Swell, Flicker, Fluctuation etc.

Rated Frequency Over / Under Frequency

Optimized to perform real work Power factor

Thus occurrence of above events or existence of the above listed phenomena in a power

supply system serves as parameters for Power Quality measurement or evaluation. Some of the

common power quality parameters are described as under [6]:

2.1 Harmonic Distortion

Voltage or current waveforms are normally sinusoidal in shape of fundamental frequency

(say 50 Hz). The harmonic frequencies are integral multiples of fundamental frequency For

example 2nd harmonic in a 50Hz system is 2x50 i.e., 100 Hz.

Figure 2-1: Fundamental with 3rd harmonics

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Figure 2-2: Fundamental with multiple harmonics

Whenever harmonics having frequency multiples of fundamental frequency are generated

sinusoidal shape of voltage and current is distorted. This distortion is called harmonic

distortion. Frequencies that are not integral of multiples of the fundamental frequency are

called “inter-harmonics” There is also a special category of inter-harmonics, which are

frequency values less than the fundamental frequency, called sub-harmonics. The presence of

sub-harmonics is often observed by the lighting flicker.

One other parameter to be aware of is the phase angle of the harmonic relative to the

fundamental. Figure 2-1 and Figure 2-2 shows various combination of waveforms with

harmonics in phase with fundamental and 180 degrees out-of-phase with the each other. The

resulting waveform looks quite different.

Total Harmonic Distortion (THD)

Voltage Distortion is represented by the Total Harmonic Distortion (THD). THD is defined

as the root mean square (r.m.s.) of the harmonics expressed as a percentage of the fundamental

component, i.e.

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THD = √∑ Vn2N

n=2

V1

Where Vn is the single frequency r.m.s. voltage at harmonic n, N is the maximum harmonic

order to be considered and V1 is the fundamental line to neutral r.m.s. voltage. In general N is

taken up to the 50th harmonic.

The maximum THD

which is acceptable in the

utility system is 5.0% at

33-132 kV, 2.5% at 220

kV, 2.0% at 400 kV and 1.5% at 765 kV voltage levels (as per CEA standards [8]). Harmonics

may be generated upto 100th order with magnitude of 20%.

Total Demand Distortion (TDD)

The severity of harmonic distortions in the current wave is measured in terms of Total

Demand Distortion (TDD).

TDD = √∑ In2N

n=2

IL= THD x (I1/IL)

Where In is the single frequency r.m.s. current at harmonic n, N is the maximum harmonic

order to be considered and IL is the fundamental r.m.s. current at rated load & I1 is the

fundamental component of current at current load. In general N is taken up to the 50th

harmonic.

2.1.1 Sources of Harmonics

Voltage Harmonics in the system are generated due to electric machines working above the

knee of the magnetization curve (magnetic saturation), arc furnaces, welding machines,

rectifiers, DC brush motors, non-linear loads (such as power electronics equipment including

ASDs (Adjustable Speed Drives), fan regulators, CFLs, televisions, switched mode power

supplies, data processing equipment, high efficiency lighting etc.). While current harmonics

are injected into the system by the non-linear loads. The process of melting metal in an electric

arc furnace can result into large currents that are comprised of the fundamental, inter-harmonic,

and sub-harmonic frequencies being drawn from the electric power grid. These levels can be

quite high during melt-down phase, and usually affect the voltage waveform. The amount of

Note: When referring to harmonics in Voltage waveforms, we

always use THD; while referring to harmonics in current

waveform, we always use the term TDD.

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voltage harmonics often depends upon the amount of harmonics current drawn by the load, and

the source impedance, which includes all the wiring and transformers back to the source of the

electricity. If the source harmonic impedance is very low (often referred to as ‘stiff’ system)

then the harmonic current will result in lower harmonic voltages than if the source impedance

were high (such as found with some types of isolation transformers). The impedance of an

inductive device goes up as the frequency goes up, while the impedance goes down for

capacitive devices for higher harmonics.

2.1.2 Problems caused by Non-linear loads

Non-linear loads cause a number of power quality problems in the distribution system.

They inject harmonic currents into the AC mains. These harmonic currents increase the r.m.s.

value of supply current, increase losses, cause poor utilization and heating of components of

the distribution system, and also cause distortion and notching in voltage waveforms at the

point of common coupling due to voltage drop in the source impedance.

Some of the major effects of non-linear loads are as follows:

Increased r.m.s. value of the supply current

Increased losses

Poor utilization of distribution system

Heating of components of distribution system

Derating of the distribution system

Distortion in voltage waveform at the point of common coupling, which indirectly

affects many types of equipment

Disturbance to the nearby consumers

Interference in communication system

Mal-operation of protection systems such as relays

Interference in controllers of many other types of equipment

Capacitor bank failure due to overload, resonance, harmonic amplification, and

nuisance fuse operation

Excessive neutral current

Harmonic voltage at the neutral point

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Some of these nonlinear loads, in addition to harmonics, require reactive power and create

unbalancing, which not only increases the severity of the above-mentioned problems but also

causes additional problems like:

Voltage regulation problems and voltage fluctuations

Unbalance in three-phase voltages

Derating of cables and feeders

The voltage Unbalance

creates substantial

problems for electrical

machines due to negative

sequence currents, noise,

vibration, torque pulsation,

rotor heating, and so on and

of course their derating.

Summary of various power quality problem, their causes and impacts are given in Table 2-3.

A typical electronic device like a computer (which is non-linear load) with a TFT screen

consumes 160W power from the supply, while makes 146W of harmonic power to get wasted

in the power lines. (Refer Exhibit-A).

2.1.3 Effects of Harmonic Distortion

Harmonics generated by non-linear loads like arc furnaces, battery charger etc.

substantially increase the losses in distribution transformers. This increase in losses, increases

operating costs and can shorten transformer life. Harmonic distortion caused by non-linear

loads on the electricity supply system, result in currents in the system that are of higher

magnitude than expected and contain harmonic frequency components. These currents cannot

be adequately measured by some of the lower cost portable test meters commonly used by

installation and maintenance technicians, leading to current levels being seriously under-

estimated, sometimes by as much as 40%. This error in magnitude alone can result in circuits

being installed with conductors that are too small. Even if the current is within the capacity of

the overcurrent protection device, conductors run at higher temperatures and waste energy,

typically 2-3% of the load. Frequently the overcurrent protection device rating is too close to

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the real load current (because it was under-estimated) and the circuit is prone to so-called

nuisance tripping.

a) Increased losses in Transformer:

Delta windings of the transformer get overheated, where triplen harmonics generated on

the load side of a delta-wye transformer will circulate in the transformer. Transformer loss

components include no load (core loss) and load losses (copper loss). Harmonics significantly

increases losses which are primarily of I2R copper losses and eddy current losses. Harmonics

increase these losses in the following ways:

a) Copper Losses (I2R): Harmonic currents are influenced by a phenomenon known as

skin effect. Since they are of higher frequency than the fundamental current they tend

to flow primarily along the outer edge of a conductor. This reduces the effective cross

sectional area of the conductor and increases its resistance. The higher resistance will

lead to higher I2R losses.

b) Eddy Current Losses: Stray electromagnetic fields induce circulating currents in a

transformer’s windings, core and other structural parts. These eddy current produce

losses that increase substantially at the higher harmonic frequencies.

b) Error in measurement when using average reading meters:

If a test tool is labeled and specified to respond to true rms value, it means that the tool’s

internal circuit calculates the rms value according to the rms formula. This method will give

the correct rms value regardless of the current’s wave shape. Average responding tools do not

have true-rms cicuitary. Such meters capture the rectified average of an AC waveform and

multiply the number by 1.1 to calculate the r.m.s. value. In other words, the value they display

is not true value, rather a calculated value based on assumption about the wave shape. The

average-responding methods works for pure sine waves, but can lead to large reading errors

(up to 40%) when the waveform is distorted by non-linear loads such as variable speed drives

or computerized controls.

c) Malfunction of Equipment:

Nuisance operation of protective devices, including false tripping of relay and failure of a

UPS to transfer properly, especially if the controls incorporate zero-crossing sensing circuits.

Figure 2-3 shows composite current waveform with 70% third order in phase with fundamental

and 50% fifth order harmonics, 180º out of phase with fundamental added to the fundamental.

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In practice on several occasions, distorted waveforms will be much more complex than this

example, containing many more harmonics with a more complex phase relationship. In this

composite current waveform, it can be observed that there are six zero-crossing points per cycle

instead of two, so any equipment/ protection system that uses zero crossing as a reference may

malfunction.

Figure 2-3: Distorted Composite Current waveform

d) Excessive Neutral Current, resulting in overheated neutrals:

The odd triplen (3rd order) harmonics in three phase wye circuits are actually additive in

neutral.

Figure 2-4: Additive Third Harmonics

This is because the harmonics number multiplied by 120º phase shift between phases is a

integer multiple of 360º. This puts the harmonics from each of the three phase legs in-phase

with each other in the neutral, as shown in Figure 2-4.

e) Zero, negative sequence voltages on motors and generators:

In a balanced system, voltage harmonics can either be positive (fundamental, 4th, 7th, …),

negative (2nd, 5th, 8th … ), or zero( 3rd, 6th, 9th, …) sequence values. This means that the

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voltage at that particular frequency tries to rotate the motor forward, backward or neither(just

heats up the motor), respectively.

Sequence Harmonic Order

Positive (+) 1 (fundamental) 7 13 19

Zero (0) 3 9 15 21

Negative (-) 5 11 17 23

f) Blown fuses on power factor correction capacitors, due to high voltage and currents from

resonance with line impedance.

g) Reduced power factor

h) Loss of efficiency in electric machines / equipment

i) Electromagnetic interference with communication systems,

j) Reduction in equipment life

k) Light flickers, etc.

2.2 Inter-harmonics

Harmonics having frequency of a non-integer multiple of the fundamental frequency are

known as inter-harmonics. By analogy to the order of a harmonic, the order of inter-harmonic

is given by the ratio of the inter-harmonic frequency to the fundamental frequency. If its value

is less than unity, the frequency is also referred to as a sub-harmonic frequency.

2.2.1 Sources of Inter-harmonics

There are two basic mechanisms for the generation of inter-harmonics. One is due to

generation of components in the sidebands of the supply voltage frequency and its harmonics

as a result of changes in their magnitudes and/or phase angles. These are caused by rapid

changes of current in equipment and installations, which can also be a source of voltage

fluctuations. Examples of such inter-harmonic sources are variable frequency drives (VFDs),

arc furnaces, fluctuating loads etc.

The second mechanism is the asynchronous switching (i.e. not synchronized with the power

system frequency) of semiconductor devices in static converters. Typical examples are

cycloconverters and pulse width modulation (PWM) converters. Inter-harmonics generated by

them may be located anywhere in the spectrum with respect to the power supply voltage

harmonics frequency) of semiconductor devices in static converters.

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2.2.2 Consequences of Inter-harmonics

Inter-harmonic currents cause inter-harmonic distortion of the voltage waveform

depending on magnitudes of the current components and the supply system impedance at that

frequency. The greater the range of current components’ frequencies, greater is the risk of

occurrence of unwanted resonant phenomena, which can increase the voltage distortion and

cause overloading or disturbances in the operation of equipment and installations. Among the

most common, direct, effects of inter-harmonics are thermal effects, low-frequency oscillations

in mechanical systems, disturbances in fluorescent lamps and electronic equipment operation,

interference with control and protection signals in power supply lines, overloading of passive

parallel filters for high order harmonics, telecommunication interference, acoustic disturbance,

saturation of current transformers etc.

2.3 Power Factor

Power factor is a measure of how effectively a specific load consumes electricity to produce

work. The higher the power factor, the more work produced for a given voltage and current.

Figure 2-5 shows the power vector relationships for both linear and non-linear loads. Power

factor is always measured as the ratio between real power in kilowatts (kW) and apparent power

in kilovolt amperes (kVA).

Figure 2-5: Power factor relationship for linear and non-linear load

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For linear loads, the apparent power in kVA (S = V•I) is the vector sum of the reactive power

in kVAR (Q) and the real power in kW (P). The power factor is P/S = CosΦ, where Φ is the

angle between S and P. This angle is the same as the displacement angle between the voltage

and the current for linear loads. Power factor may be lagging when current lags voltage due to

inductive loads and leading when current leads voltage in case of capacitive loads. For a given

amount of current, increasing the displacement angle will increase Q, decrease P, and lower

the power factor.

Power factor may be further classified as displacement power factor and true power factor.

Displacement power factor is the cosine of the angle between the fundamental voltage and

current waveforms. The fundamental waveforms are by definition pure sinusoids. But, if there

is waveform distortion due to harmonics, the power factor angles are different than what would

be for the fundamental waves alone. The presence of harmonics introduces additional phase

shift between the voltage and the current. True power factor is calculated as the ratio between

the total active power used in a circuit (including harmonics) and the total apparent power

(including harmonics) supplied from the source:

True power factor = Total active power/ Total apparent power

True power factor is always less than displacement power factor if harmonics are present.

2.3.1 Sources of Poor Power Factor

Main source of poor power factors are inductive loads like induction motors, arc furnaces,

electric discharge lamps, industrial heating furnace, high intensity discharge lightings etc. and

various non-linear loads. These loads draw higher reactive power resulting into drawl of more

apparent power whereas active power demand remains the same, which causes low power

factor.

2.3.2 Consequences of Poor Power Factor

Poor power factor results into requirement of higher apparent power and higher current

flow to do the same work against good pf. It results into following disadvantages:

i. Greater conductor size

ii. Higher capacity electrical machines like generator or transformers are required which

increases size and cost of the system.

iii. Due to the high current for low power factor, the losses increases in the conductors and

switchgear machinery

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iv. The large current at low lagging power factor causes greater voltage drops in

alternators, transformers and transmission lines. This results in decrease in voltage at

the driving end and forces the use of extra equipment to counter act the voltage drop

like voltage stabilizers. This increases the cost of power supply system.

2.4 Voltage Sag (or Dip)

Decrease of the normal voltage level between 10% and 90% of the nominal r.m.s. voltage

at the power frequency, for durations of 0.5 cycles to 1 minutes is known as voltage sag or dip.

Instantaneous voltage sag lasts from 0.5 cycles to 30 cycles whereas momentary sag is from 30

cycles to 3 sec and temporary sags are from 3 sec to 1 min.

Figure 2-6: A Typical Voltage sag

Figure 2-6 shows typical voltage sag phenomena. Voltage sag differs from other voltage

reduction disturbances. Other voltage reduction disturbances often occur intermittently, like

voltage flicker, while voltage sags occur once, for a short time.

2.4.1 Sources of Voltage Sag

Voltage sags are caused by faults on the transmission or distribution network (most of

the times on parallel feeders), faults in consumer’s installation, connection of heavy loads,

start-up of large motors etc. Whenever, any of the above mentioned phenomena takes place

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very high current flows through load impedance which pulls the voltage down. Transmission

faults cause Voltage Sags that last for about 5 cycles (100ms). Distribution faults last longer

than transmission faults, while large motor loads can cause voltage sag on utility’s and end

user’s power system.

Arc furnace is a good example of load that can produce large voltage sags in electrical

power systems. Arc furnaces operate by imposing a short circuit in a batch of metal and then

drawing an arc, which produces temperatures in excess of 10,000˚C, which melt the metal

batch. Arc furnaces employ large inductors to stabilize the current due to the arc. Tens of

thousands of amperes are drawn during the initial few seconds of the process.

Figure 2-7 depicts typical current drawn by an arc furnace. Once the arc becomes stable, the

current drawn becomes more uniform. Due to the nature of the current drawn by the arc

furnace, which is extremely nonlinear, large harmonic currents are also produced.

Figure 2-7: Typical Current drawn by Arc Furnace

Utility faults are also responsible for voltage sags. Approximately 70% of the utility-related

faults occur in overhead power lines. Some common causes of utility faults are lightning

strikes, contact with trees or birds and animals, and failure of insulators. The utility attempts to

clear the fault by opening and closing the faulted circuit using reclosers, which can require

from 40 to 60 cycles. The power line experiences voltage sags or total loss of power for the

short duration it takes to clear the fault. Obviously, if the fault persists, the power outage

continues until the problem is corrected.

2.4.2 Consequences of Voltage Sag

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As per site measurements/observations, Voltage Sag is found to be the most frequently

occurring event in the Power Supply at almost all the voltage levels. Voltage sag may result

into malfunction of information technology equipment, namely microprocessor-based control

systems (PCs, PLCs, ASDs, etc.) that may lead to a process stoppage, tripping of contactors

and electromechanical relays, disconnection and loss of efficiency in electric rotating

machines. Compared to other power quality problems affecting industrial and commercial end

users, voltage sag occurs most frequently. They reduce the energy being delivered to the end

user and cause computers to fail, adjustable speed drive to shut down, and motors to stall and

overheat.

2.5 Voltage Swell

Increase in voltage above 110% but below 180% of normal, with a duration of 0.5 cycle to

1 minute is known as voltage swell. Instantaneous voltage swell lasts from 0.5 cycles to 30

cycles whereas momentary swell is from 30 cycles to 3 sec. and temporary swell are from 3

sec to 1 min. Figure 2-8 shows typical voltage swell waveform.

Figure 2-8: Typical Voltage swell

2.5.1 Sources of Voltage Swell

Voltage swells are usually associated with system fault conditions. This is particularly true

for ungrounded or floating delta systems, where the sudden change in ground reference result

in a voltage rise on the ungrounded phases. In the case of a voltage swell due to a single line-

to-ground (SLG) fault on the system, the result is a temporary voltage rise on the unfaulted

phases, which last for the duration of the fault. Voltage swells can also be caused by the de-

energization of a very large load. The abrupt interruption of current can generate a large voltage

due to the capacitance of the line and change in current flow. Voltage swell is also caused by

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switching of large capacitor banks, long transmission lines, badly dimensioned power sources,

badly regulated transformers etc.

Figure 2-9: Voltage swell observed on a typical 400 kV line

2.5.2 Consequences of Voltage Swell

Effects of a voltage swell are often more destructive. It may cause breakdown of

components on the power supplies of the equipment, though the effect may be a gradual, but

accumulative in type. The increased energy from a voltage swell often overheats equipment

and reduce its life. It can cause control problems and hardware failure in the equipment, due to

overheating that could eventually result to shutdown. Also, electronics and other sensitive

equipment are prone to damage due to voltage swell. It also results in flickering of lighting and

visualization screens.

2.6 Over Voltage / Under Voltage

Increase in the voltage to the level of 110% to 120% of the nominal voltage for more than

1 minute is known as over voltage, whereas reduction in voltage to the level of 90% to 80% of

the nominal voltage for more than 1 minute is called under voltage phenomenon.

2.6.1 Sources of Over / Under Voltage

Over / under voltage is caused due to sudden load changes, high / low load conditions,

improper operation of compensation device, outage of lines / transformers etc. Lightly loaded

long lines / cables causes over voltage in the system whereas heavily loaded lines / cables

causes under voltage. The major cause of overvoltage is capacitor switching, charging a long

transmission line, dropping of loads etc. On the other hand too much load on the utility’s

system, during very cold or hot weather, loss of major transmission line serving a region may

Swell

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result in under voltage. Overloading inside an end user’s own distribution system can also cause

under voltages.

2.6.2 Consequences of Over / Under Voltage

Continuous over voltage may result into over stress of equipment, increased corona,

flashover of insulators etc. whereas continuous under voltage may result into inefficient

operation of devices, increased losses, high current drawl, heating effect and mal-operation of

the power system components.

2.7 Voltage Interruptions

A voltage interruption is the complete loss of electric voltage or a drop to less than 10% of

nominal voltage (<0.1 pu). Voltage interruptions are further defined as instantaneous,

momentary, temporary & sustained. Short duration interruption of loss of voltage (<0.1 pu) on

one or more phase conductors for a time period less than 0.5 cycle is termed as instantaneous

interruption whereas similar interruption between 0.5 cycles and 3 seconds is called momentary

interruptions and between 3 seconds and 1 minutes is known as temporary interruption. Long

duration or sustained interruption is complete loss of voltage on one of more phase conductors

for a time greater than 1 minute. Figure 2-10 shows typical voltage interruption phenomena,

where different types of interruptions have been defined over time scale.

Figure 2-10: Typical Voltage interruptions

2.7.1 Causes of Voltage Interruptions

A disconnection of power supply causes interruption, which usually occur due to opening

of a circuit breaker, line recloser, or fuse due to faults. For example, if a tree branch comes into

contact with an overhead electricity line (short circuit), a circuit breaker will clear the fault and

may automatically reclose and the customers who receive their power through the faulted line

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will lose power supply and experience an interruption. Momentary / temporary interruptions

may occur due to opening and automatic reclosure of protection devices, insulation failure,

lightning and insulator flashover. Whereas long/sustained interruptions may be caused by

equipment failure, storms and objects (trees, cars, etc.), striking lines or poles, fire, improper

coordination of protection devices, human error etc.

2.7.2 Effect of Voltage Interruptions

Tripping of protection devices, loss of information and malfunction of data processing

equipment and stoppage of operation of sensitive equipment, such as ASDs, PCs, PLCs etc.

happen due to voltage interruptions. Loss of production in a business costs money. Any kind

of interruption can result in a loss of production in an office, retail market, or industrial factory.

It’s not that only loss of electrical service causes loss of production, but the time required to

restore electrical service also leads to lost production. Some types of processes cannot “ride

through “even short interruptions. “Ride through” is the capability of equipment to continue to

operate during a power disturbance. For example, in a plastic injection molding plant; for a

short interruption of 0.5 sec it takes about 6 hours to restore the production.

2.8 Transient

Transients are momentary changes in voltage or current that occurs over a short period of

time generally of the order of microseconds. ANSI Std. 1100-1992 defines transient as “A sub-

cycle disturbance in the AC waveform that is evidenced by a sharp brief discontinuity of the

waveform. Transients may be of either polarity and may be of additive or subtractive energy

to the nominal waveform.”

Figure 2-11: Two types of Transient Waveforms

A transient can be impulsive or a damped oscillatory types as shown in Figure 2-11.

Impulsive transient are known as a sudden, non–power frequency change in the steady-state

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condition of voltage, current, or both that is unidirectional in polarity – either primarily positive

or negative. These are classified into three categories according to their rise and decay times.

Nanosecond transients generally exist near the source of the disturbance. It rises in 5 ns with

duration of less than 50 ns. Microsecond impulsive transients are relatively unusual, but they

have much higher amplitudes. It rises in 1μs and has duration of 50 ns to 1 ms. Millisecond

impulsive transient is the most common to occur in a power system. It rises in 0.1 ms and lasts

more than 1 ms.

Oscillatory Transient is described as a sudden, non–power frequency change in the steady-

state condition of voltage, current, or both that has both positive and negative polarity values

(bidirectional). Oscillatory transients are categorized in Table 2-2

Table 2-2: Classification of oscillatory transients

Type of Oscillatory

Transient

Frequency Duration Typical voltage

magnitude

Low frequency <5 kHz 0.3-50 ms 0-4 pu

Medium frequency 5-500 kHz 20 Micro second 0-8 pu

High Frequency 0.5-5 MHz 5 Micro second 0-4 pu

Most of the surges in any

system/facility occur due to

internal switching transients

(turning on/off motors,

transformers, photocopiers, etc.)

2.8.1 Sources of Transients

The most common well known reason of transient is lightning, which causes induced

voltage onto conductors whenever it strikes near the power line. Other reasons of transients

include switching of large loads, opening and closing of disconnectors on energized lines,

switching of capacitor banks, re-closure operations, tap changing on transformers, loose

connections in the power system etc. Figure 2-12 shows transients developed due to capacitor

switching.

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Figure 2-12: Typical Transient due to capacitor switching

2.8.2 Consequences of Transients

Transients affect equipment in transmission / distribution system badly. It degrades the

contacting surfaces of switches, disconnectors, and circuit breakers. Intense transient activity

can produce "nuisance tripping" of breakers by “heating” the breaker and "fooling" it into

reacting to a non-existent current demand. Electrical transformers are forced to operate

inefficiently because of the hysteresis losses produced by transients and can run hotter than

normal.

Transients / Surges cause motors to run at higher temperatures and result into vibration, noise,

and excessive heat. Motor winding insulation is degraded and eventually fails. It also produces

hysteresis losses in motors and can cause early failures. Transients also cause early failures of

lighting devices and electronic equipment.

2.9 Spike

A Spike is a very fast variation of the voltage value for durations from a several

microseconds to few milliseconds.

Figure 2-13: A Typical Spike

Transient

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2.9.1 Sources of Spikes

A Spike may be caused by lightning, switching of lines or power factor correction

capacitors, disconnection of heavy loads etc.

2.9.2 Consequences of Spikes

Voltage spikes may result in destruction of components and insulation materials, data

processing errors or data loss, electromagnetic interferences etc.

2.10 Voltage Fluctuations & Flicker

Voltage fluctuations are systematic variations of the voltage waveform envelope, or a series

of random voltage changes in which amplitude is modulated by a signal with frequency less

than 25 Hz. In this phenomenon voltage varies in the range of 0.1% to 7 % of the nominal

voltage. The most important effect of this power quality problem is the variation in the light

output of various lighting sources, commonly termed as Flicker.

Flicker is the impression of instability of the visual sensation brought about by a light

stimulus, whose luminance fluctuates with time. It is the effect of power quality on humans

rather than on equipment where human eye can detect it as a variation in the lamp intensity of

a standard bulb. Light flicker results when there are voltage sub-harmonics in the range of 1-

30 Hz. The human eye is most sensitive at 8.8 Hz, where just a 0.5 % variation in the R.M.S.

voltage is noticeable with certain types of lighting. The result of this can be simply annoying,

producing headaches and eye fatigue. Figure 2-14 shows the voltage fluctuation causing

flicker.

Figure 2-14: Voltage waveform causing flicker

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Because of subjective nature of light flicker, standards organizations have difficulty

correlating voltage fluctuations standards to perceptible light flicker that is irritating to the

observer. In this context, various standards refers GE flicker curve published in 1951, shown

in Figure 2-15 .

Figure 2-15: Flicker Sensitivity Curve by GE

2.10.1 Sources of Voltage Fluctuation and Flicker

Equipment or devices that exhibit continuous, rapid load current variations (mainly in the

reactive component) can cause voltage fluctuations and light flicker. Normally, these loads

have a high rate of change of power with respect to the short-circuit capacity at the point of

common coupling. Such loads include electric arc furnaces, static frequency converters,

cycloconverters, rolling mill drives, main winders, large motors during starting etc. Small

power loads such as welders, power regulators, boilers, cranes and elevators, to name a few,

may cause voltage fluctuation and flicker depending on the electrical system where they are

connected.

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Other causes of voltage fluctuations

thereby flicker include, capacitor switching,

transformer on-load tap changers (OLTC),

step voltage regulators, other devices that

alter the inductive component of the source

impedance, variations in generation capacity,

particularly intermittent type renewables (e.g.

wind turbines, solar panels), low frequency

voltage inter-harmonics, loose connections etc.

2.10.2 Consequences of Voltage Fluctuation and Flicker

Flicker is considered the most significant effect of voltage fluctuation, because it can affect

the production environment by causing personnel fatigue and lower work concentration levels.

In addition, voltage fluctuations may stress electrical and electronic equipment towards

detrimental effects that may disrupt production processes with considerable financial costs.

Other effects of voltage fluctuation include nuisance tripping due to mal-operation of relays

and contactors, unwanted triggering of UPS units to switch on battery mode, problems with

some sensitive electronic equipment (which require a constant voltage) etc.

2.11 Voltage Unbalance

Voltage unbalance in a three phase system occurs when variation in three phase voltage

magnitudes or the phase- angle differences between them are not equal. ANSI C84.1-1995

defines voltage unbalance as the maximum deviation from the average of the three-phase

voltages or currents, expressed in percent.

Voltage unbalance = (max. deviation from average voltage / average voltage) x 100

Where average voltage = (Sum of voltages of each phase) / 3

2.11.1 Sources of Voltage Unbalance

It is caused by faulty operation of power factor correction equipment, unbalanced or

unstable utility supply, unbalanced transformer bank supplying a three-phase load that is too

large for the bank, unevenly distributed single-phase loads, unidentified single-phase to ground

faults, an open circuit on the system primary, large single-phase loads (induction furnaces,

traction loads) etc. Figure 2-16 shows the typical voltage unbalance.

It has been found that 50% of people tested

perceive light flicker as an annoyance

under the following conditions

Voltage Change Changes/Second

1 volt 4

2 volts 2

4 volts 1

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Figure 2-16: Typical voltage unbalance

2.11.2 Consequences of Voltage Unbalance

Unbalanced systems imply the existence of a negative sequencecomponent that is harmful

to all three- phase loads. The most affected loads are three-phase induction machines.The main

effect of voltage unbalance is motor damage from excessive heat. Voltage unbalance can create

a current unbalance 6 to 10 times the magnitude of voltage unbalance. In turn, current

unbalance produces heat in the motor windings that degrades motor insulation causing

cumulative and permanent damage to the motor.

2.11.3 Mitigation of Voltage Unbalance

Voltage unbalance can be mitigated by proper maintenance of equipment, re-distributing

the loads, providing AC line reactors and dc link reactors with variable speed drives etc.

Installation of single phase regulators, static var compensators, STATCOM, line conditioners

etc. may also help in reducing voltage unbalance.

2.12 DC Offset

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DC offset is the presence of a DC current and/or voltage component in an AC system. Main

causes of DC offset in power systems are operation of rectifiers and other electronic switching

devices, geomagnetic disturbances causing Geo-magnetically Induced Current (GIC) etc.

Figure 2-17 shows typical dc offset in voltage waveform. DC offset in AC networks cause half-

cycle saturation of transformer / reactor core, generation of even harmonics in addition to odd

harmonics, additional heating in appliances and electrolytic erosion of grounding electrodes

and other connectors.

Figure 2-17: Typical DC offset in voltage waveform.

Three limb transformers with relatively large air gap between core and tank is used for removal

of dc offset caused by rectifiers and geo magnetically induced currents.

2.13 K-Factor in Transformer

The “K-factor” is a number that quantifies potential losses in transformers due to harmonic

currents. Higher order harmonics influence the K-factor more than low order harmonics. The

k factor is equal to the sum of the square of the harmonic frequency currents (expressed as a

ratio of the total R.M.S. current) multiplied by the square of the harmonic frequency numbers:

Transformers that are required to supply large non-linear loads must bederated to handle

the harmonics. This derating factor is based on the percentage of the harmonic currents in the

load and the rated winding eddy current losses.

All the above parameters as explained are commonly used to evaluate power quality.

Standards for above parameters have been defined by various institutions / utilities to provide

quality power to consumers. Some of the standards in this respect are discussed in next chapter.

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2.14 Grounding for Power Quality

Good grounding is essential for electrical equipment and distribution systems’ safety. Good

grounding provides the level of safety required to protect personnel and equipment from shock

hazards. Every solution to a power quality problem in any facility should start with a thorough

ground study.

The IEEE Emerald book, which has long been accepted as the industry standard for

grounding electronic and electrical equipment, states that ground resistance should be 1 ohm

for substations and 2-5 ohms for commercial and industrial services. (Though, many household

equipment vendors require less than 3 ohms only, the answer to this is explained in the

following sections). Let’s examine the following example that will illustrate the need for a low

resistance ground.

Example 1: This illustrates a typical equipment installation of a piece of equipment that

has internal sensitive electronic and electrical components. Quite often the manufacturer of this

equipment will insist on a ground rod driven at the piece of equipment or the warranty will be

void. The manufacturer of this equipment may have good intentions in regard to establishing a

good ground, the establishment of this separate ground is both a safety hazard and a Power

Quality problem. The next illustration shows the dangers of a separate ground rod.

Figure 2-18: Grounding without ground rod

Let’s say that ground rod #1 has a ground resistance of 10 ohms and ground rod #2 has a

ground resistance of 20 ohms. Note both are less than the NEC 250-56 of 25 ohms. The

difference in resistance between both ground rods is: Ground rod #2 20 ohms minus Ground

rod #1 10 ohms equals a 10 ohm difference.

For demonstration purposes in Example 2 let’s say a lighting strike occurred close to this

facility and it induced only 1000 amps into the earth under the facility. This number of 1000

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amps is not out of line as induced current flow from lighting has been measured at much higher

values. Using Ohms Law we can deduce the following:

10 ohms difference between ground rods times 1000 amps of current flow from the lightning

strike equals 10,000 volts of potential between the electrical service and our machine with

sensitive components.

This large voltage is both a safety hazard and a Power Quality hazard as both can and do

cause problems in the facility. One way to solve this problem is to bond the two ground rods

together. This will lower the difference between the two ground rods, thus, lowering the voltage

between the same.

The pyramid illustrates the need for a good ground to

build the solid base in a program to solve power quality

problems in any facility. Only after establishing a good

base one can address the other issues &solve the problems

in a facility.

An effective grounding system:

Provides a more stable system with a minimum of transient voltages and electrical

noise. (Using Surge Protection Devices)

Provides a path to ground in fault conditions to insure proper operation of ground fault

protection equipment.

Provides grounding of all conductive enclosures that may be touched by personnel,

thereby reducing shock hazards.

Reduces static electricity that may be generated within facilities.

Figure 2-19: Grounding with ground rod

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Provides protection from large electrical disturbances (such as lighting) by creating a

low resistive path to earth.

Should be built so that it can be EASILY measured on a REGULAR basis to make sure

it is still functioning properly.

2.15 Neutral Grounding for MV/HV/EHV Networks

The different modes of grounding for the medium voltage power distribution networks

differ from country to country. The physical characteristics of the networks, such as network

extend, load density, load nature, the quality of the earthing terminals, the network type – air,

underground or mixed - led the operators of the various countries to an independent choice of

grounding in their particular networks. For the choice of the neutral grounding mode, they have

to consider the criteria of tension control during the occurrence of single-phase or multiphase

fault currents, the reliability and the sensitivity of protections, the voltage level – simple line-

to-earth or phase-to-phase during of the network voltage rise during the defect, the quality of

supply as well as the security of goods and people.

Neutrals, however, play a major role in effective grounding. A fault that occurs 16 km from

a substation can cause swells of 1.33 per unit if a broken neutral exists on any part of a system.

Even faults occurring 2.25km away can cause swells up to 1.5 per unit if a broken neutral

exists. The size of the neutral conductor appreciably reduces swells, whereas good grounding

hardly affects the voltage at all. This indicates that the neutral is more important than the

grounding.

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Table 2-3: Summary of Power Quality Problems, their causes and effects

Problems Type Categorization Causes Effects Waveform distortion

DC offset Volts, Amperes Geomagnetic disturbance, rectification Saturation in transformers

Harmonics THD, Harmonic Spectrum ASDs, Nonlinear loads Increased losses, poor power factor

Inter harmonics THD, Harmonic Spectrum ASDs, Nonlinear loads Acoustic noise in power equipment

Notching THD, Harmonic Spectrum Power electronic converters Damage to capacitive components

Noise THD, Harmonic Spectrum Arc furnaces, arc lamps, power converters Capacitor overloading, disturbances to appliances

Transients Impulsive Peak, rise time and duration Lighting strikes, transformer energization, capacitor switching

Power system resonance

oscillatory Peak magnitude and frequency components

Line, capacitor or load switching System resonance

Short duration voltage variation

sag Magnitude, duration Motor starting, single line to ground faults Protection malfunction, Loss of production

swell Magnitude, duration Capacitor switching, large load switching, faults Protection malfunction, stress on computers and home appliances

Interruption duration Temporary faults Loss of production, mal function of fire alarms

Long duration voltage variation

Sustained interruption

duration faults Loss of production

Under voltage Magnitude, duration Switching on loads, capacitor de energization Increased losses, heating

Over voltage Magnitude, duration Switching off loads, capacitor energization Damage to household appliances

Voltage Imbalance Symmetrical components Single phase load, single phasing Heating of motors

Voltage Fliker Frequency of occurrence, Modulating frequency

Arc furnaces, arc lamps Human health, Irritation, Headache, migraine

Voltage Fluctuations Intermittent Load changes Protection malfunction, light intensity changes

Power frequency variations

Faults, disturbances in isolated customer owned systems and islanding operations

Damage to generator and turbine shafts

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2.16 Impact of Power Quality

Until a few years ago, Power quality phenomena were considered just because of their

effects on the electromagnetic behavior of electrical devices, with a focus on fault probability,

components’ loss of life, or overload and so on. Now, increased attention to environmental

protection and energy savings in general drives us to consider Power Quality phenomena also

in the perspective of related energy losses. Poor power quality usually results in various types

of losses resulting due to increase in the rms value of supply current, overheating heating of

equipment, failures of equipment, shutting down of electronic equipment, unwanted circuit

breaker tripping, interference on communication system, flickering of fluorescent lights,

saturation of non-linear devices, reducing the service life of equipment, requirement of higher

size equipment, production loss in process industries etc.

As per a study on poor power quality (section 3.7), it has been observed that industrial

firms do not suffer any shortfall in production due to the erratic supply, because the firms have

adapted themselves to the current power scenario so well that all they suffer is cost escalation

due to use of power backups to support their production; it is estimated that for an average

interruption of say 30 minutes per week to the Industrial load (connected load is approx.170

GW) in India, the average cost escalation accounts to be around Rs. 2.65 Lakh Cr. per year.

(Assuming a very conservative loss of Rs. 10 per minute of interruption per kW of connected

industrial load). In addition, loss occur due to harmonics and poor power factor.

Due to poor power factor transmission capacity gets reduced and it is estimated that

energy worth Rs. 5400 cr. faces a bottleneck in the Grid. This energy could be otherwise served

to the users.

***

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Chapter-3

3 Power Quality Standards Power Quality Standards are needed for all the stakeholders in Power System. How

can utilities deliver and their customers receive the quality of power without Power quality

standards? How can the electronic industries produce sensitive electronic equipment without

power quality standards? How can the Power conditioning industry manufacture devices that

will protect sensitive electronic equipment without power Quality standards? They can’t.

Therefore, stakeholders in the power sector have developed power quality standards in

recent years. They realize that the increased use of sensitive electronic equipment, increased

application of non-linear devices to reduce stress on equipment, losses and improve energy

efficiency, and the increasingly complex and interconnected power system, integration of

renewables etc. all contribute to the need of power quality standards. Utilities need standards

that define limits on the amount of voltage distortion (caused by customer’s pollution), their

power systems can tolerate. End users need standards that set limits not only on the electrical

pollution produced by utility systems, but also similar pollution generated by other end users.

As power systems become more interconnected, contracts based on standards will be needed

to protect the offended party. Standards allow utilities to provide different levels of power

quality services.

As the issue regarding Power Quality started gaining attention worldwide, several

stakeholders like utilities, statutory authorities, regulatory bodies, generators, consumers, grid

operators, equipment manufacturers, solution providers etc. have started to come together for

standardization of power quality parameters. It has resulted in a new direction of research and

development (R&D) activities for the design and development engineers working in the field

of power electronics, power systems, electric drives, digital signal processing, and sensors. It

has changed the scenario of power electronics as most of the equipment using power converters

at the front end need modification in view of these newly visualized requirements. Moreover,

some of the well-developed converters are becoming obsolete and better substitutes are being

looked for. Apart from these issues, a number of standards and benchmarks have already been

developed by various organizations such as IEEE (Institute of Electrical and Electronics

engineers) and IEC (International Electrotechnical Commission), to determine the normal or

acceptable levels, which can be imposed onto the customers, utilities, and manufacturers to

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minimize or to eliminate power quality problem. List of organizations publishing power quality

standards are given in Table 3-1:

Table 3-1: Organizations Publishing Power Quality Standards

S. No. Organization Type of Standard Address

1. ANSI Steady-state voltage ratings (ANSI C84.1)

American National Standards Institute 11 West 42nd St,. 13th Floor New York, NY 10036 e-mail: [email protected]

2. CENELEC Regional standards European union Standards Organization

3. CISPR International Standards International Special Committee on Radio Interferences

4. EPRI Signature newsletter on power quality standards

Electric Power Research Institute 3112 Hillview Ave. Palo Alto, CA 94304

5. IEC International Standards International Electrochemical Commission 31 rue de Verembc P.O. Box 131 CH-1211 Geneva 20 Switzerland

6. IEEE International and United States Standard

Institute of Electrical and Electronics Engineers 445 House Lane Piscataway, NJ 08855-1331 e-mail: [email protected]

7. ITI (Formerly CBEMA)

Equipment Guides Information Technology Industry Council 1250 I St. NW, Suite 200 Washington, DC 20005 Web Address: www.itic.org

8. NEMA Equipment standards National Electrical Manufacturers Association 1300 N 17th St., Suite 1847 Rosslyn, VA 22209 Web Address : www.mema.org

9. NFPA Lighting Protection National Electric Code

National Fire Protection Association 1 Batterymarch Park Quincy, MA 02269-0101 Web Address : www.nfpa.org

10. NIST General Information on all Standards

National Center for Standards and Certification National Institute of Standards and Technology Bldg. 820, Room 164 Gaithersburg, MD 208997 e-mail: [email protected]

11. UL Safety standards for equipment

Underwriters Laboratories, Inc. 333 Pfingsten Rd. Northbrook, IL 60062-2096 e-mail: [email protected]

12. CEA Grid related Standards Ministry of Power, Govt. of India, Central Electricity Authority Web Address : http://www.cea.nic.in

ANSI/IEEE C57.110 Recommended Practice for Establishing Transformer Compatibility

when supplying non-sinusoidal load currents is a useful document for determining how much

a transformer should be derated from its nameplate rating when operating in the presence of

harmonics. There are two parameters typically used, called K-Factor and TDF (Transformer

mailto:[email protected]


http://www.itic.org/

http://www.mema.org/

http://www.nfpa.org/



http://www.cea.nic.in/

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43

Derating Factor). Modern power quality analysers/monitors have the features to automatically

calculate these values.

3.1 Standard related to various PQ phenomena

It was felt by stakeholders that for the purpose of identification, characterization and

reporting of different power quality events and phenomena, standard definitions are necessary.

This was also needed for the measurement and monitoring equipment or power quality

analysers to identify different PQ issues without any ambiguity. Some of the standards that

exist in this regard include the standards provided by working group IEEE 1433 and IEC

61000-1-1. IEEE 1159.2 provides standard for event characterization, IEEE 519-1992[3]

recommended practices and requirements for Harmonic control in Electric Power Systems

provides guidelines from determining the acceptable limits. In order to help the power quality

industry compare the results of power quality measurements from different instruments, the

IEEE developed IEEE standard 1159-1995, Recommended Practice for Monitoring Electric

Power Quality. List of some standards on various issues of power quality are given in Table

3-2.

Table 3-2: Power Quality Standards

Standards Description

IEEE 519-1992 Recommended practices and requirements for harmonic control in

electrical power systems

IEEE standard 1159-

1995

Recommended practice for monitoring electric power quality

IEEE standard 1100-

1999

Recommended practice for powering and grounding sensitive

electronic equipment

IEEE standard 1250-

1995

Guide for service to equipment sensitive to momentary voltage

disturbances

IEEE standard 1366 Electric power distribution reliability indices

IEC 61000-2-2 Compatibility levels for low frequency conducted disturbances and

signaling in public supply systems

IEC 61000-2-4 Compatibility levels in industrial plants for low frequency

conducted disturbances

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Standards Description

IEC 61000-3-2 Limits for harmonic current emissions(Equipment input current up

to and including 16 A per phase)

IEC 61000-4-15 Flicker meter – Functional and design specifications

EN 50160 Voltage characteristics of public distribution systems

Table 3-3 provides the characterization of different PQ phenomena as specified by IEEE 1159-

1995.

Table 3-3: Characterization of different PQ phenomena specified by IEEE 1159-1995

S.

No.

Power Quality

Phenomena

Typical

spectral

Content

Typical

Duration

Typical

Voltage

Magnitude

1.0 Transients

a) Impulsive

Nanosecond 5 ns rise < 50 ns

Microsecond 1 µs rise 50 ns-1 ms

Millisecond 0.1 ms rise >1 ms

b) Oscillatory

Low Frequency <5kHz 0.3 – 50 ms 0 – 4 pu

Medium Frequency 5-500 kHz 20 us 0 – 8 pu

High Frequency 0.5 -5 MHz 5us 0 - 4 pu

2.0 Short duration

variations

a) Instantaneous

Interruption 0.5 – 30 cycles < 0.1 pu

Sag 0.5 – 30 cycles 0.1 -0.9 pu

Swell 0.5 – 30 cycles 1.1 – 1.8 pu

b) Momentary

Interruption 0.5 cycle – 3 s < 0.1 pu

Sag

30 cycles –

3s 0.1 - 0.9 pu

Swell 30 cycles – 3s 1.1 – 1.4 pu

c) Temporary

Interruption 3s – 1min < 0.1 pu

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S.

No.

Power Quality

Phenomena

Typical

spectral

Content

Typical

Duration

Typical

Voltage

Magnitude

Sag 3s – 1min 0.1 - 0.9 pu

Swell 3s – 1min 1.1 – 1.2 pu

3.0 Long duration

variations

a) Interruption, sustained > 1min 0.0 pu

b) Under-voltages > 1min 0.8 – 0.9 pu

c) Over-voltages > 1min 1.1 – 1.2 pu

4.0 Voltage imbalance Steady state 0.5 – 2%

5.0 Waveform distortion

a) DC offset Steady state 0 – 0.1%

b) Harmonics 0 – 100th H Steady state 0 – 20 %

c) Inter-harmonics 0 – 6 kHz Steady state 0 – 2%

d) Notching Steady state

e) Noise Broad - band Steady state 0 – 1 %

6.0 Voltage fluctuation < 25Hz intermittent 0.1 – 7%

7.0 Power Frequency

Variations < 10s

Note: s=seconds, ns=nanosecond, µs=microsecond, ms=millisecond, kHz=kilohertz,

MHz=Megahertz, min=minute, pu=per unit

3.2 Standards for measurement, monitoring and mitigation

Since the measurement, analysis and mitigation of PQ issues is a repetitive work that has

to be carried out at some instant of time at every part of the grid, standards have been provided

in this regard. IEC-61000-5-(1,2,6,7) provide installation and mitigation guidelines.

3.3 Standards for testing procedure and equipment

IEC 61000-4-30[5] provides the standards for power quality measurements. It gives the

range of values that measuring equipment should be capable of capturing and storing.

Similarly, IEEE 1159.1 provides a guide for recorder and data acquisition requirements. These

standards are required for assisting in proper selection of testing equipment based on the type

of measurements that are to be carried out.

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3.4 Standards regarding limitations for different PQ phenomena

These standards are provided as a guide for ensuring compatibility of different power

system elements in places where specific regulations have not been formulated by local

regulatory bodies. Also, these regulations assist the regulators to formulate the standards

applicable to different parts of the grid and to different types of consumers. In, India, Central

Electricity Authority (Grid Standards) Regulation, 2010 provides the limits for some of the PQ

parameters for Indian grid. According to which, all entities, appropriate Load Dispatch Centers

and Regional Power Committees, for the purpose of maintaining the Grid Standards for

operation and maintenance of transmission lines, shall meet the following:

a) Operation of grid at a frequency close to 50 Hz and shall not allow it to go beyond the

range 49.7 to 50.2 Hz or a narrower frequency band specified in the Grid Code, except

during the transient period following tripping.

b) Maintaining the steady state voltage within the limits specified as per Table 3-4

Table 3-4: Voltage limits as per CEA[8]

S.

No.

Nominal System Voltage

(kVrms)

Maximum

(kVrms)

Minimum

(kVrms)

1 765 800 728

2 400 420 380

3 220 245 198

4 132 145 122

5 110 121 99

6 66 72 60

7 33 36 30

c) Ensuring that temporary over voltage due to sudden load rejection remains within the

limits specified in Table 3-5.

Table 3-5: Temporary over voltage limits as per CEA[8]

S.No. Nominal System Voltage

(kVrms)

Phase to Neutral Voltage

(kVpeak)

1 765 914

2 400 514

3 220 283

4 132 170

Temporary over voltage limits for the systems below 132 kV have been decided by the

State Commissions in the respective State Grid Codes.

d) Ensuring that the maximum permissible values of voltage unbalance shall be as

specified in Table 3-6.

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Table 3-6: Permissible voltage unbalance as per CEA[8]

S. No. Nominal System Voltage(kVrms) Voltage Unbalance (%)

1 765 and 400 1.5%

2 220 2%

3 33 to 132 3%

e) Observing permissible limits of voltage fluctuation as following:

(i) The permissible limit of voltage fluctuation for step changes which may

occur repetitively is 1.5 %.

(ii) For occasional fluctuations other than step changes the maximum

permissible limit is 3%.

The transmission licensee shall ensure that the voltage wave-form quality is maintained

at all points in the Grid by observing the limits of voltage harmonics as given in Table

3-7.

Table 3-7: Voltage harmonics limit as per CEA[8]

S. No. System Voltage

(kVrms)

Total Harmonic

Distortion

(%)

Individual Harmonic of any

Particular Frequency

(%)

1 765 1.5 1.0

2 400 2.0 1.5 3 220 2.5 2.0

4 33to132 5.0 3.0

f) Current harmonics limit has been kept similar to standards defined in IEEE 519 as

mentioned in Table 3-8 for different voltage levels. The current harmonic distortion

limits apply to limits of harmonics that loads should draw from the utility at the point

of common coupling. Harmonic limits differ based on the ISC/IL rating at PCC (or how

stiff it is) where ISC is the maximum short circuit current at the point of coupling

(PCC) and IL is the maximum fundamental frequency Average load current of

maximum demand at PCC. It can be observed from Table 3-8 that the limit decreases

at the higher harmonic values, and increases with larger ratios.

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Table 3-8: Current distortion limits for harmonics [3]

Harmonic Current Limits for Non-Linear Load at the Point-of-Common-Coupling with

Other Loads, for voltages120- 69,000 volts

Maximum Odd Harmonic Current Distortion in % of Current at rated load

ISC/IL <11 11<17 17<23 23<35 35 TDD

<20* 4 2 1.5 0.6 0.3 5

20<50 7 3.5 2.5 1 0.5 8

50<100 10 4.5 4 1.5 0.7 12

100<1000 12 5.5 5 2 1 15

>1000 15 7 6 2.5 1.4 20

Harmonic Current Limits for Non-Linear Load at the Point-of-Common-Coupling with Other Loads, for voltages 69,000-161,000volts

Maximum Odd Harmonic Current Distortion in% of Current at rated load

ISC/IL <11 11<17 17<23 23<35 35 TDD

<20* 2 1 0.75 0.3 0.15 2.5

20<50 3.5 1.75 1.25 0.5 0.25 4

50<100 5 2.25 2 0.75 0.35 6

100<1000 6 2.75 2.5 1 0.5 7.5

>1000 7.5 3.5 3 1.25 0.7 10

Harmonic Current Limits for Non-Linear Load at the Point-of-Common-Coupling with Other Loads, for voltages>161,000volts

Maximum Odd Harmonic Current Distortion in% of Fundamental Harmonic Order

ISC/IL <11 11<17 17<23 23<35 35 TDD

<50 2 1 0.75 0.3 0.15 2.5

³50 3 1.5 1.15 0.45 0.22 3.75

Even harmonics are limited to 25% of the odd harmonic limits. For all power generation

equipment, distortion limits are those with ISC/IL<20. Here

ISC is the maximum short circuit current at the point of coupling (PCC)

IL is the maximum fundamental frequency 15-or 30- minutes load current at PCC

TDD is the Total Demand Distortion (THD normalized by IL)

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3.5 Transformer overheating standards

ANSI/IEEE Standard C57 series addresses the problem of harmonics causing transformers

to overheat. It does this by setting so-called K-factor rating of the transformers. Harmonics

major effect on transformers is to increase losses and heating in transformers. They increase

both load and no-load losses by increasing hysteresis losses. IEEE and UL have adopted

standards to either derate regular transformers or to design special transformers that can

withstand the effect of harmonics. These specially designed transformers are called K-factor

transformers.

The typical load “K-factors”, which are derived from ANSI/IEEE standards are the

following: K-4, K-9, K-20, K-30, K-40 and K-50. In theory, a transformer could be designed

for other K-factors in-between those values. Table 3-9 shows K-factor for different types of

loads.

Table 3-9: K-factors for different loads

Loads K –Factors

Incandescent Lighting, Resistance Heating, Motors, Motor – Generators

and Electromagnetic Control Devices

K – 1

UPS with input filtering, HID Lighting, PLCs and Solid State Controls

(Except variable speed drives), Induction Heaters and Welders

K – 4

UPS without input filtering, Telecommunications (e.g. PBX), Multiple

receptacle circuits in general health care facilities, School Facilities and

Production Line Equipment

K – 13

Variable Speed Drives, Critical Care Facilities (Hospital operating room),

Main – Frame Computers and Circuits with exclusive Data Processing

K – 20

Small Main – Frames and Multiwire Receptacle Circuits in commercial,

Industrial, Medical and Educational Laboratories

K – 30

Other Loads identified as producing very high amount of harmonics K – 40

3.6 Trends in Power Quality Standards

Over the years, various standards organizations have developed power quality standards

whenever a particular power quality problem appeared. They started in 1890s, setting limits

for voltage and current followed by frequency in 1900 and subsequently limit on flicker,

interruptions, harmonics and sag/transients etc. illustrates the historical trend.

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Figure 3-1: Power Quality Standards Historical Trend

Now, more standards need to be developed in future as the use of sensitive electronic and

computerized equipment proliferates and deregulation of the utility industry unfolds.

3.7 Power Quality in India

The Electricity Act (EA), 2003, explicitly specifies the responsibility to supply quality

power to end consumers. The relevant provisions are listed below:

In section 24(1) it is indicated that if a licensee fails to deliver quality supply, his license can

be suspended for a period of 1 year.

As per section 29(1), if any dispute arises with respect to the quality of electricity during

regional grid operation, it shall be referred to the Central commission for decision by the

Regional Load Despatch Centre.

Section 33(1) specifies that during state grid operation, if any dispute arise with reference to

the quality of electricity, it shall be referred to the State commission for decision by the State

Load Despatch Centre.

Section 57(1) specifies that appropriate commission may specify standards of performance of

a licensee. It also has indicated the penalty for non-performance and the compensation clause

for the affected parties.

Section 73(1): The authority shall perform such functions and duties as the Central Government

may prescribe or direct, and in particular…(b) specify the technical standards for construction

of electrical plants, electric lines and connectivity to the grid;…(d) specify the grid standards

for operation and maintenance of transmission lines.

Section 79(1): The Central Commission shall discharge the following functions, namely, (i) to

specify and enforce the standards with respect to quality, continuity and reliability of service

by licensees.

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Section 86 (1): The State Commission shall discharge the following functions, namely, (i)

specify and enforce standards with respect to quality, continuity and reliability of service by

licensees.

Electricity supply code for distribution utilities has to be specified by the regulator, under

section 50. The technical standards for construction of electrical plants and electric lines and

connectivity to the grid under clause (b) of section 73 and the grid standards specified under

clause (d) of section 73 have to be specified by the Central Electricity Authority(CEA). Grid

code has to be specified by the Central Commission under clause (h) of sub-section (1) of

section 79 and the State Grid Code referred to under clause (h) of sub-section (1) of section 86

has to be specified by the respective State Commission.

Standards & Code: In line with EA 2003, provisions, Central Electricity Authority (Technical Standard for

Grid Connectivity) Regulations, 2007, was notified in the Gazette of India on 17th February

2007. The standard specified include limits of steady-state e, temporary overvoltage due to

sudden load rejection, maximum permissible value of voltage unbalance, maximum fault

clearance times, voltage waveform quality and so on.

Central Electricity Authority (Grid Standard) Regulations, 2010, was notified in the Gazette of

India on 26th June 2010.

Central Electricity Authority (Technical Standard for Construction of Electrical Plants and

Electrical Lines) Regulations, 2010, was notified in the official Gazette on 20th August 2010.

Central Electricity Regulatory Commission (Indian Electricity Grid Code) Regulations, 2010,

was notified on 28th April 2010.

Most of the State Electricity Regulatory Commissions (SERCs) have notified state Grid Code,

supply code and standard of performance regulations, in line with EA 2003 provisions.

Some SERCs have notified distribution codes. Gujarat Electricity Regulatory Commission has

notified ‘Gujarat Electricity Distribution Code’ on 25th August, 2004. Orissa Electricity

Regulatory Commission has constituted a PQ monitoring committee to oversee the quality of

Supply.

Though various standards and codes have specified PQ norms, monitoring mechanism is

missing or not effective. PQ implementation status needs to be reviewed by regulatory bodies.

Distribution utilities shall have to observe the norms mentioned in the standard of performance

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regulation. SERCs may have to evaluate the PQ performance index of licensees; full Return on

Equity (RoE) in the Annual revenue requirement of a licensee can be approved based on

achievement of the stipulated PQ index/norms.

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3.8 Some points to be noted:

TDD Vs. THD

It has been observed that, as the loading in any circuit increases, the individual harmonic

components & THD (Current) w.r.t. fundamental (%f) reduces, while the Total Demand

Distortion (TDD) remains almost constant (Figure 3-2).

This is because the fundamental component of the current wave increases with the load.

THD (Total Harmonic Distortion) in current & individual current harmonics w.r.t. fundamental

current (%f) are load dependent values which can’t depict the severity of current harmonics;

whereas TDD & individual current harmonics w.r.t. rated current (%r) are independent of load

and hence more significant in order to depict the Power Quality. High levels of current

harmonics (w.r.t. fundamental current) have been observed in the HV/EHV system during field

measurement (Refer Vol.-2). These high value w.r.t. fundamental current may not be useful for

harmonics mitigation measures, instead TDD shall be used.

Half Wave Symmetry:

Most electrical loads (except half-wave rectifiers) produce symmetrical current waveforms,

which mean that the positive half of the waveform looks like a mirror image of the negative

half. This leads to presence of only odd harmonics. Even harmonics would disrupt this half-

wave symmetry. The presence of even harmonics should cause the investigator to suspect there

is half-wave rectifier on the circuit. This may also result from a full wave rectifier when one

side of the rectifier has blown or has damaged components. Early detection of this condition in

a UPS system can prevent a complete failure when the load is switched onto back-up power.

Figure 3-2: Typical variation in THD / TDD vs. Load

(MW)

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Neutral conductor loading

Single phase nonlinear electronic loads will draw current only during the peak of the

voltage waveform. These loads combined in a three phase circuit produce triplen harmonics

(multiple of third order harmonics, like third, ninth, fifteenth). Triplen harmonics do not cancel

one other but are additive and return exclusively through the neutral conductor. Thus, the

neutral current may exceed the capacity of the neutral conductor.

***

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Chapter-4

4 International Experiences on

Power Quality Management The availability of sophisticated and sensitive technologies& appliances at consumer end

has led demand for higher levels of power quality across the world. To meet these needs,

various approaches have been followed by utilities. Some utility companies have set up

premium power quality contracts for their customers, whereas some identify the additional

costs involved in providing the services and bill the customer for it. Regulators have also played

their role in fixing standards of power quality. Council of European Energy Regulators

(CEER), in their report titled "Quality of Electricity Supply-Initial Benchmarking on Actual

Levels, Standards, and Regulatory Strategies", provides a regulatory view on power quality

and regulations as below:

“Where market competition replaces monopoly regimes, quality competition should

replace quality regulation; however complete withdrawal of the regulator is not usually

possible because, while some quality factors can be individually negotiated, others cannot”.

Some of the innovative methods and approaches for providing quality power to customer

internationally have been discussed below:

4.1 Power Quality Contracts

The utility companies in some countries around the world have set up a program for power

quality contracts. For customers, who wish premium power, are supplied through dedicated

feeder fulfilling the power quality needs of customers. Some of the programs are described

below:

4.1.1 Power quality contracts by EdF (Électricité de France), France

At the beginning of 1990, the use of increasingly sophisticated and more sensitive

electronic equipment led to EdFs customers requesting higher levels of power quality. In order

to fulfill the customers’ needs, EdF set up a number of electricity quality contracts and services

for large and medium customers. In 1994, EdF began to use the “Emeraude”contract as an

experiment for 6,000 customers. Presently, EdF offer their customers customized contracts

with assigned voltage quality levels (“engagements” or contractual levels). If the customer

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claims for better contractual levels than the normal ones, they can avail the same by paying

extra charges.

The Emeraude contract applies the principle of compensating customers for damage if the

utility company exceeds an agreed upper limit on the number of power disturbances. EdF

guarantees minimum levels of power quality in the contracts and customers must not exceed

maximum levels for emissions to the system. If customers exceed their limits, they may be

required to find a mitigation solution, especially if they impact the power quality delivered to

other customers. Table 4-1 shows some values that EdF guarantees at medium voltage and

required from the customers.

Table 4-1: EdF’s and customers' obligations for medium voltage (basic contract)

Quality parameter EdF’s annual electricity quality obligation

Customers’ electricity quality obligation

Planned interruptions (work on the net)

Number < 2 Duration < 4 hours

No

Long interruptions (>3 min) (Number)

< 10,000 inhabitants :6 10,000 – 100,000 inhabitants :3 > 100,000 inhabitants (except cities): 3 Cities >100,000 inhabitants and Paris suburbs :2

No

Short Interruptions (1s – 3 min) (Number)

< 10,000 inhabitants :30 10,000 – 100,000 inhabitants :10 > 100,000 inhabitants (except cities): 3 Cities >100,000 inhabitants and Paris suburbs :2

No

Voltage variations (R.M.S. ) Voltage is ± 5% of contractual voltage and Uc is ± 5% of nominal voltage

No

Voltage fluctuation and flicker PLT ≤1 (measured as per IEC 1000-4-15)

Voltage changes in stages: < 5% of contractual voltage. (measured according to IEC-61000-2-2)

Unbalance ≤ 2 % ≤ 1% if short circuit power > 40MVA

Frequency 50Hz ±1% 50Hz +4% and -6% (Island systems)

No

Harmonics (temporary clause) Harmonics: 10 minute values according to EN 50160 and IEC 61000-2-2)

Levels are defined as a function of the order number, according to agreement

Customer adjusted agreements. Short interruptions (1s – 3min) Voltage Sags

Customer – adjusted values Not taken in account are: Duration < 600 ms Residual voltage > 70 %

No

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4.1.2 Detroit Edison Company, USA

The Detroit Edison Company (DEC), a subsidiary of DTE Energy, is one of the largest

electricity utility companies in the USA. It serves more than 2.2 million customers in South-

East Michigan, the America industrial heartland. DEC offers a special manufacturing contract

(SMC) with premium power quality for manufacturers (automotive industry) in their region.

On the other hand, DEC also offers special interruptible rates to residential, commercial and

industrial customers. Customers get discounted electricity prices in return for permission to

occasionally interrupt electrical service.

The DEC Special Manufacturing Contract (SMC) was introduced in 1994 for three of

DEC's largest customers: the Chrysler Corporation (after 1998, DaimlerChrysler), the Ford

Motor Company and General Motors Corporation, who wanted to decrease their cost due to

competition in automotive market. .DEC on the other hand was cautious about losing these

companies to other electricity suppliers.

Presently such contracts are offered to many customers covering offices, assembly

factories, processing plants and component delivery departments. The SMC specifies that the

manufacturers are compensated when certain levels of predefined parameters have been

exceeded.

4.1.3 National Electricity Regulator (NER), South Africa

The establishment of an Electricity Regulator in South Africa in 1995 led to the creation of

five national Quality of Supply standards (NRS-048) between 1996 and 1998. In 2004 the

National Energy Regulator Act was passed and in 2005 the National Energy Regulator of South

Africa (NERSA) was established. NERSA enforces Quality of Supply standards within South

Africa.

Regulatory framework for utilities prepared by NER, South Africa embodied power quality

directives. These directives include mechanisms to ensure information to customers about their

rights and obligations regarding power quality, establishment of accessible power quality

complaints resolution mechanisms, identification & development of appropriate standards and

codes of practice on power quality, ensuring the long-term sustainability of the supply industry

with regard to power quality and ensuring appropriate power quality performance information

is made available through measurement, data management, and statistical analysis.

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NER has mandated that utility shall be responsible for the power quality levels delivered

to all of its customers and independent power producers connected to its network. Utility shall

implement suitable contracts with all customers connected in its network as shown in Figure

4-1 for various power quality parameters including voltage quality, voltage dips and harmonics.

The utilities are also bound to declare any capital or refurbishment projects incurred

specifically to improve power quality and details of claims paid for poor power quality

annually.

Figure 4-1: Power quality contracts to be implemented by the distribution company

Quality of Supply regulation applies to all voltage levels, and provides NERSA with a

means of evaluating distribution companies. NRS-048-2 “Electricity Supply – Quality of

Supply Part 2: Voltage characteristics, compatibility levels, limits and assessment methods”,

defines measurement methods, compliance levels and limit levels.

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4.1.4 Norwegian Water Resources and Energy Directorate (NVE), Norway

Regulation of quality of supply began in 1991 with the passing of the Energy Act in

Norway. The NVE regulations apply to all network voltage levels. The regulations provide

definitions and in some cases measurement methods and compliance levels for the following

supply voltage characteristics:

Frequency

Short interruptions

Long interruptions

Flicker Pst

Flicker Plt

Interharmonic voltage

Temporary over voltages

Voltage dips

Voltage variations

Harmonic voltages

Mains signaling voltage

Rapid voltage change

Voltage unbalance

In 1995 mandatory reporting of interruptions greater than three minutes was added and 179

network companies were required to report key figures on voltage quality. On January 1, 2005

Table 4-2: NRS-048 Compliance limits in South Africa

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the Norwegian Water Resources and Energy Directorate (NVE) put into force “Regulations

relating to the quality of supply in the Norwegian power system”.

4.2 Extensive Measurements

United Illuminating Company, Connecticut, USA is one of the electricity companies with

a grid in the USA, which uses extensive measurements of power quality parameters to ensure

quality in power supply. Continuous measurements are made on the medium voltage network

and measurement data are used to set performance benchmarking. Measurement data is not

only used for focusing on customer needs, but also for planning long-term improvements in

the grids. They inform potential customers about the number of voltage dips expected in

different parts of the power network and accordingly sensitive customers choose appropriate

place to setup their establishment.

Jacksonville Electric Authority (JEA) operating in the city of Jacksonville, Florida, USA

has installed a wide area power quality monitoring solutions including of reporting tools to

ensure delivery of clean power.

4.3 Power Quality Services

Duke energy, the DSO in North Carolina, USA provides services for power quality issues

with customers. Any consumer can request utility online for power quality issues related to

Table 4-3: NVE Directorate Compliance Limits

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stray voltages, lightening / surge damage, grounding problems, reliability concerns, flicker etc.

Power Quality department of the utility, visits and identifies the problem and if required, power

quality meters are also installed to have long duration data. After which, it submits the report

to consumer along with recommendations. To make consumers aware towards power quality,

utility also arrange training sessions on Grounding Principles and Practices, Basic Grounding

and Surge Protection, Understanding Power Quality, Understanding Power Quality Monitoring

Equipment, Understanding Power System Harmonics, Power Quality Mitigation Strategies etc.

4.4 Power Quality Labeling

Distribution network operators in the Netherlands have initiated an easy classification

system based on labeling the power quality. While designing this classification format, the grid

operators recognized that power quality is not a subject with which many customers are

familiar and therefore for proper communication to customers, classifications for labels are

made simple and understandable. To keep the labeling meaningful and transparent, aggregation

of large amounts of measured data is done to have single measure of quality.

For each characteristic we can calculate the normalized power quality level using the equation:

Where,

r(v, q, p) = The normalized power quality characteristic q, at site v, for phase p

m(v, q, p) = The actual level of characteristic q, at site v, for phase p

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63

l(q) = The compatibility level of characteristic q

When there is no disturbance, the normalized value will be 1 (m=0).

As mentioned above many innovative activities are being taken in different parts of the world

to ensure power quality up to end consumer. Continuous efforts in this direction will help all

the stakeholders of power sector in providing power to doorstep with all the quality parameters

intact, adhering all standards. For this suitable mitigation devices are to be designed and

installed at strategic locations.

4.5 Cost of Poor Power Quality Survey:

In European Union, it has been surveyed (as per LPQI Survey, November 2008)[23] that

Poor Power Quality costs more than €150 Billion per year to the industrial sector. Voltage dips

or short interruptions have been identified as the most damaging events which mainly affect

the equipment and the Work in Progress; which in-turn, leads to losses in terms of money.

Figure 4-2: Cost of Poor Power Quality in EU

Similarly, as per a survey in the United States (Source: Primen Study: The Cost of Power

Disturbances to Industrial & Digital Economy Companies) [36], the Power Quality problems

cost around $119-$188 Billion per year.

The major problem being Power Outage, which is a very critical issue for digital economy and

the continuous process manufacturing industry. (Source: Primen Study: The Cost of Power

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Disturbances to Industrial & Digital Economy Companies)[36]. Since Voltage Sags &

interruptions are the most economically significant events, the effects of voltages sag &

interruptions in the industries are briefly discussed in the following section.

4.6 Voltage Sags in Process Industry Applications

Process industry equipment can be particularly susceptible to problems with voltage sags

because the equipment is interconnected and a trip of any component in the process can cause

the whole plant to shut down. Examples of these industries include plastics, petrochemicals,

textiles, paper, semiconductor, and rubber. Important loads that can be impacted include the

following [24]:

Motors and other 3-phase loads connected directly to the LV bus.

Adjustable speed drive and other power electronic devices that use 3-phase power

directly from the LV bus.

Lighting connections which utilize single phase (phase-to-neutral) connections.

Control devices such as computers, contactors, and programmable logic controllers

often supplied through a single phase control transformer.

Figure 4-3: Cost of Poor Power Quality in USA

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Figure 4-4: CBEMA Limits

While the CBEMA limits suggest a "standard" sensitivity to voltage sags, actual plant

equipment has a variety of operational characteristics during voltage sags. A few examples are

listed here.

Motor Contactors and Electromechanical Relays: A manufacturer provided data indicates

that their line of motor contactors will drop out at 50% voltage if the condition lasts for longer

than one cycle. This data should be expected to vary among manufacturers, and some

contactors can drop out at 70% normal voltage or even higher.

High-Intensity Discharge (HID) Lamps: Mercury lamps are extinguished at around 80%

normal voltage and require time to restrike. Voltage sag that extinguishes HID lighting is often

mistaken as a longer outage by plant personnel.

Adjustable Speed Motor Drives (ASDs): Some drives are designed to ride through voltage

sags. The ride through time can be anywhere from 0.05 sec to 0.5 sec, obviously depending on

the manufacturer and model. Some models of one manufacturer monitor the ac line and trip

after voltage sag to 90% of normal voltage is detected for 50 ms.

Programmable Logic Controllers (PLC's): This is an important category of equipment for

industrial processes because the entire process is often under the control of these devices. The

sensitivity to voltage sags varies greatly but portions of an overall PLC system have been found

to be very sensitive. The remote I/O units, for instance, have been found to trip for voltages as

high as 90% for a few cycles.

For any MV customer, the major event which leads to equipment disruption, is voltage

sag (or voltage dip). The solution to fix the problems arising due to voltage sags needs a proper

cost vs. benefit analysis.

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Solutions can be

implemented at different levels

of the system for an end user

that has equipment or a process

that is sensitive to voltage sags

and momentary interruptions.

For instance, the individual sensitive equipment can be protected with power conditioning with

ride through support, a whole portion of the facility could be protected, or measures could be

implemented on the utility system to improve performance. The individual solutions must be

identified and a system perspective used to evaluate the economics. The most economical

alternative usually involves protection closest to the sensitive equipment or within the design

of the equipment itself.

The best way to guarantee the compatibility of Process Equipment with its Electrical

Environment is to require the Equipment to Comply with Voltage Sag/Interruption

Standards.

OEMs have to be forced to Incorporate Voltage Sag/Interruption Tolerance into their

Equipment.

The Push has to come from End Users.

EPRI has shown that Machines can be built to Comply with Voltage Sag Standards,

like SEMI F47, with almost no Difference in Cost.

4.7 The costs of Interruptions/Outages

The cost of any Event (Voltage-Sag,

Interruption, Outage etc.) can be

estimated using three approaches:

1. Indirect analytical evaluations

2. Case Studies of actual blackouts

3. Customer Surveys

The Cost vs. event graph may vary

with the industry, location, region,

country and many more parameters.

The Recognized Voltage Sag/ Interruption Standards

are:

SEMI F47-0706 (Semiconductor Equipment and

Materials institute)

IEC 61000-4-11 and 61000-4-34 (International

Electrotechnical Commission)

ITIC (Information Technology Industry Council)

Figure 4-5: A Typical Cost vs. Interruption

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A typical survey conducted in Punjab (considering some odd 300 industrial customers)[17]

revealed a cost-interruption function as shown in Figure 4-5.

As per EPRI, “The Economics of Customer Power”, IEEE T&D show, 2003[34], all the

industries & commercial facilities suffer monetary losses due to Voltage Sags &

Interruptions/Outages, the semiconductor industry is the most vulnerable to Voltage Sags&

momentary Outages/Interruptions; followed by process industry. A single Voltage Sag or

momentary outage may lead to loss of millions of bucks (as shown in Figure 4-7 & Figure 4-6).

Figure 4-6: Cost of Momentary Interruptions and Outages

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A report by TERI, “The Cost of Unserved Energy”, back in 1998-99, had indicated that,

shortages in the availability of power to the manufacturing sector resulted in loss of value added

(GDP) to the extent 1% and 2.2% of the total manufacturing sector value added (GDP) in the

States of Haryana and Karnataka respectively. The Report had also indicated that for the year

1998-99, shortages in the availability of power to the agricultural sector resulted in loss of value

added (GDP) to the extent 3.1% and 13.3% of the total agricultural sector value added (GDP)

in the States of Haryana and Karnataka respectively. This report was prepared by considering

the following three methods:

1. Value of production loss for each unit of power outage (production loss method)

2. Cost of alternative or back-up power generation (captive generation method)

3. Willingness to pay (WTP) for reliable and uninterrupted electricity supply (WTP

method).

The most significant & latest methods of evaluating the cost of poor power quality have

been proposed by CEER (Council of European Energy Regulators) in “Guidelines of Good

Practice on Estimation of Costs due to Electricity Interruptions and Voltage Disturbances,

2010”[16]. It is required in India, that a fresh, nation-wide survey is conducted to evaluate the

various economic impacts of Poor Power Quality& bring awareness about the same.

Figure 4-7: Loss per Voltage Sag in different industries

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For a given industry, there could be several issues related to poor power quality. The

problems may vary with geographical, topological, social or even political scenario. Hence, the

right power quality solution is site and industry specific.

4.8 A Case Study in India:

A case study, “Lack Of Affordable & Quality Power: Shackling India’s Growth Story

(2012)”,by FICCI[12], was carried out at all-India level, spreading across major industrial (25

cities) cities, to understand the frequent power cuts being faced by Indian Industries. A total of

650 firms representing both the manufacturing as well as service group were canvassed with a

structured questionnaire. The main outcomes of this report are as follows:

a) High Average Monthly Electricity Cost

The Average Cost of electricity to the industries varies between Rs. 5.16 to as high as

Rs. 8.48 per Unit. (Figure 4-8)

b) High Industrial Power Shortage

The results showed that about 37 percent of firms across India face less than 1 hour of

power shortage a week. At the same time 21 percent suffer more than 30 hours per

week! (Figure 4-9).

Figure 4-8: Avg. cost of electricity per Unit (left) & Avg. Monthly Electricity cost (right)

Source: “Lack of Affordable & Quality Power: Shackling India’s Growth Story (2012)”, FICCI[12]

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c) Shortfall in Production (due to interruptions in Power Supply)

The survey revealed that firms generally do not suffer any shortfall in production due

to the erratic power supply. This is because the firms in India have adapted themselves

to the current power scenario so well that all that they suffer is cost escalation due to

the use of power backups to support their production activity. However, it was

considered important to ask the industrial groups about any shortfall that they might

incur due to the intermittent power supply, in case they do not use power backups to

support their operations. The survey revealed that 14 percent, majorly medium

enterprises, suffer less than 2 percent shortfall in production. This was majorly

constituted by firms from Maharashtra, Gujarat and Karnataka where majority of the

firms faced power shortage for less than 1 hour a week. This category was majorly

constituted by firms from textiles and apparels, diamond processing, automobiles and

components, trading units and others. 32 percent of the firms suffered more than 20

Figure 4-10: Shortfall in Production due to Power Outages


Figure 4-9: Distribution of Industrial Power Shortage (hours per week)


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percent production losses due to intermittent power supply. The majority of the

companies that constituted this share were large companies, with some small and

medium companies as well.

d) Cost Escalation

About 30% of the firms suffer more than 20 percent of cost escalations due to

intermittent power supply. The majority of the companies that constitute this share are

large and medium industries (like Iron and Steel, Aluminium, Fertilizer, Cement, paper

& pulp, Automobiles and Components etc.), with a significant number of small

companies as well.

e) Willingness to pay more for reliable supply

The analysis revealed that 61 percent of the firms were willing to pay more for reliable

and uninterrupted power supply while 39 percent were not willing to pay an additional

amount for a reliable and quality access power supply. Table 4-4 gives the state wise

responses of the various categories of firms.

Figure 4-11: Cost Escalation due to Interruptions in Power Supply


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Table 4-4: View of Industrial Firms on willingness to pay for reliable supply[12]

4.9 Cost of poor Power Quality in India

The Cost of low power factor

Due to poor power factor transmission capacity gets reduced and it is estimated that energy

worth Rs. 5400 cr. faces a bottleneck in the Grid. This much energy could otherwise be served

to the users, if the average power factor would have been 0.9.

Assuming network is designed to operate at pf = 0.9

Actual operating pf = 0.8

Total Technical losses = 10% of power flow

Generation tariff = 2.5 Rs./unit

Energy consumption in fiscal year (2014-15) = 1030 BU (source: CEA Report)

Unserved Energy (using above formulae) = 21.6 BU

Value of unserved energy due to poor power factor = 5400 Crore

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The Cost of Interruptions in Industries

As per a study on poor power quality (section 3.7), it has been observed that industrial

firms do not suffer any shortfall in production due to the erratic supply, because the firms have

adapted themselves to the current power scenario so well that all they suffer is cost escalation

due to use of power backups to support their production. From Figure 4-9, it can be seen that

the industrial sector is witnessing weekly interruptions ranging from less than one hour to more

than 40 hours. Assuming an average interruption of say 30 minutes per week to the Industrial

load (connected load is approx.170 GW) in India, the average cost escalation accounts to be

around Rs. 2.65 Lakh Cr. per year! (Assuming a very conservative cost escalation of Rs. 10

per minute per kW of connected industrial load).

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Figure 4-12: Power Quality Solutions

Improving the network performance to eliminate dips, interruptions, transients etc. is

very expensive and probably impossible, because these events generally occur due to some

faults which can’t be controlled. In special cases, where the need justifies the expense, it may

be possible to arrange for dual supplies that are derived from sufficiently separated parts of the

grid as to be considered independent. For most operations some form of dip mitigation

equipment is required and there is a wide range to choose from, depending on the type of load

that is being supported. The cheapest solution is to specify equipment with the necessary

resilience to dips but this option is not yet well supported by manufacturers. Hence, various

changes need to be incorporated by all the players in the Power Sector to accomplish the task

of getting a healthy Power System for the nation.

***

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Chapter-5

5 Power Quality Monitoring 5.1 Where to look for Power Quality Issues?

Wherever non-linear devices such as Switched Mode Power Supplies (SMPS), Variable

Frequency Drives (VFDs), Adjustable Speed Drives (ASDs), metal reduction operations like

electric arc furnaces, and HVDC etc. are used, one can suspect that harmonics are present. The

search can begin at the equipment effected by the problem or at the point-of-common-coupling

(PCC) as shown in Figure 5-1, where the utility service feeds the building/ industrial premises

distribution system. If only one piece of equipment is effected (or suspected as being the

producer), then it is often easier to start the monitoring process there. If the source is suspected

from the utility service side (such is the case when there is a neighboring factory that is known

to generate harmonics/unbalance and other problems), then monitoring usually begins at the

PCC.

Figure 5-1: Point of Common Coupling

5.2 Power Quality Measurement Tools

There are many power quality measurement tools available today. These include

instruments that measure and display the basic electrical parameters of voltage, current,

frequency and impedance of an electrical distribution system. These tools include ammeter,

voltmeters, multimeters, oscilloscopes, flicker meters, electro static voltmeters, infrared

detectors, radio-frequency interference and electromagnetic interference meters, harmonic and

spectrum analysers, and various types of wiring and grounding testers. These instruments

measure, display and store electrical parameters for the purpose of helping solve power quality

problems.

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The power quality monitoring system has evolved significantly. The old Watt-hour meter

has changed from analog to digital meter. It has acquired the features of a power quality

monitor to provide not only energy consumption information but power quality data as well.

Using microprocessors to record and store power and power quality measurements, some

manufacturers have combined the features of a wattmeter and power quality meter into one

meter. This allows the utility and utility’s customers to monitor the power use requirements of

the customer’s facilities not only for revenue purpose but for power quality measurement and

analysis purposes as well. These meters record both real and reactive power use as well. They

capture power quality parameters, like harmonics, sags and swells, power factor, waveforms,

crest factor etc. However, there are several portable power quality analyser (fixed and portable

both)also available now a days which can capture power quality parameters & also monitor

real and reactive power along with energy consumption over a period. They can perform spot

monitoring as well as record it over a period at specified interval.

5.3 Monitoring Power Quality

Hand held harmonic meters can be useful tools for making spot checks for known harmonic

problems. However, harmonic values will often change during the day, as different loads are

turned on and off within the facility or in other facilities on the same electric utility distribution

system. This requires the use of a harmonic monitor or power quality monitor with harmonic

measurement capabilities, which can record various power quality parameters over a period of

time. The phase voltages and currents, as well as the neutral-to-ground voltage and the neutral

current should be monitored. This will aid in pinpointing problems.

Measurement Cycle: Typically, power quality monitoring shall be carried out for one business

cycle. A business cycle is how long it takes for the normal operation of the plant to repeat itself.

For example, if a plant runs three identical shifts, seven days a week, then a business would be

eight hours. More typically, a business cycle is one week, as different operations take place on

different days of the week, such as on a Monday, when the plant equipment is restarted after

being off over the weekend, then on a Wednesday, or a Saturday, when only a skeleton crew

may be working.

Power Quality Analyzers: Usually, Power quality parameters are measured recorded and

analyzed using Power Quality analyzers. There are many variants available in power quality

analyzer which measure r.m.s. value of voltage/current, power, frequency, power factor,

harmonics, sag/swell, transients, THD, flicker, etc. Typically, power quality analyzers contain

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a meter with a waveform display screen, voltage leads, and current probes. Power quality

measurement instruments provide either a snapshot of the waveform and harmonic distortion

pertaining to the instant during which the measurement is made or capable of recording

snapshots as well as a continuous record of harmonic distortion over time.

Harmonic analyzers from various manufacturers tend to have different, upper-harmonic-

frequency measurement capability. Harmonic distortion levels diminish substantially with the

harmonic number. In order to accurately determine the frequency content, the sampling

frequency of the measuring instrument must be greater than twice the frequency of the highest

harmonic of interest. This rule is called the Nyquist frequency criteria. According to Nyquist

criteria, to accurately determine the frequency content of a 50-Hz fundamental frequency

waveform up to the 50th harmonic number, the harmonic measuring instrument must have a

minimum sampling rate of 5000 (50 × 50 × 2) samples per second. Of course, higher sampling

rates reflect the actual waveform more accurately.

Measurement of voltage harmonic data requires leads (probes) that can be attached to the points

at which the distortion measurements are needed. Typical voltage leads are 4 to 6 ft long. At

these lengths, cable inductance and capacitance are not a concern, as the highest frequency of

interest is in the range of 1500 to 3000 Hz (25th to 50th harmonic); therefore, no significant

attenuation or distortion should be introduced by the leads in the voltage distortion data.

Typically, a 5.0% loss in accuracy might be expected, if the waveform contains significant

levels of higher order harmonics.

Measuring current harmonic distortion data requires some special considerations. Most current

probes use an iron core transformer designed to fit around the conductors in which harmonic

measurements are needed. Iron-core current probes are susceptible to increased error at high

frequencies and saturation at currents higher than the rated values.

Power Quality Measurement Device can be broadly classified into two categories.

1. Single Phase Power Quality Analyser: Used for measurement of power quality

parameters for single phase quantity.

2. Three Phase Power Quality Analyser: Used for measurement of power quality

parameters on all the three phase simultaneously.

Continuous power quality monitoring detects, records, and leads to the prevention of power

quality problems.

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5.4 Typical Harmonic Spectrum Signatures

Different types of loads generate typical harmonic spectrum signatures, which can point

the investigator towards the source. This is related to number of pulses, or paths of conduction.

The general equation is harmonic number (h) = n * P ±1, where ‘n’ is any integer (1,2,3,…)

and ‘p’ is the number of pulses in the circuit. Harmonic content of some typical rectifier circuit

is shown in

Table 5-1: Typical Harmonics Found in Different Converters

Type of Device Number of Pulses Harmonics Present

Single Phase Half Wave Rectifier

1 2,3,4,5,6,7,…

Single Phase Full Wave Rectifier

2 3,5,7,9,…

Three Phase Full Wave Rectifier

6 5,7,11,13,17,19,…

2 - Three Phase Full Wave Rectifier

12 11,13,23,25,35,37,…

When the transformers are first energised, the current drawn is different from the steady

state condition. This is caused by the inrush of magnetizing current. The harmonics during this

period varies over time. Some harmonics have a negligible value for part of the time, and then

increase for a while before returning to basically zero. An unbalanced transformer (where either

the output current, winding impedance or input voltage on each leg are not equal) will cause

harmonics, as will overvoltage saturation of a transformer.

Fluorescent lights can be the source of harmonics, as the ballasts are non-linear inductors. The

third harmonic is the predominant harmonic in this case. The third harmonic current from each

phase in a four-wire wye or star system will be additive in the neutral, instead of cancelling

out.

The process of melting metal in an electric arc furnace can result in large currents that are

comprised of the fundamental, inter-harmonic, and sub-harmonic frequencies being drawn

from the electric power grid. The level can be quite high during the melt-down phase, and

usually effect the voltage waveform.

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Table 5-2 Summary of power quality measurements on common appliances

Device

THD

(Current) %

Most

Dominant

harmonic

order

Other harmonics

Supply

Voltage

(volt)

Current

Drawn

(amp)

Frequency

(Hz)

Output

Power

(Watt)

Input

Power

(Volt-

amp)

Reactive

Power

(Var)

Power Factor

Laptop 179.1 3 5, 7, 9, 11 228.3 V 0.293 A 50 Hz 36.4W 77.5 VA 5.7 VAR 0.47 Leading

Mobile Charger 172.1 3 5, 7, 9, 11, 13 234.4V 0.053 A 50 Hz 6.1W 12.4 VA 1 VAR 0.49 Leading

LED Bulb (12W) 164.0 3 5, 7, 9, 11, 13 238V 0.09A 50.05Hz 10.6 W 21.1 VA 2.8VAR 0.5 Leading

Desktop Monitor (TFT) 161.9 3 5, 7, 9, 11, 13 234V 0.104 49.92Hz 10.1W 24.5 7.8VAR 0.41 Leading

Small Tube light 129.8 3 5, 7, 9, 11, 13 234.6V 0.049 A 50 Hz 6.6W 11.6 VA 2.4 VAR 0.57 Leading

Computer with TFT Monitor

91.2 3 5, 7, 9, 11, 13 223.9V 0.861A 49.8 Hz 157.2W 204.2VA 130.5 VAR 0.76 Lagging

Computer with CRT Monitor

75.4 3 5, 7, 9, 11, 13 230.6V 0.616A 49.8 Hz 103W 138.2VA 92 VAR 0.75 Lagging

Printer under idle condition

40.2 3 5, 7, 9, 11, 13 238.6V 0.454A 50 Hz 76.9W 108.6VA 65.1 VAR 0.71 Leading

Printer (during warm-up)

40.0 3 5, 7, 9, 11, 13 235V Upto 5A 49.99Hz Upto

1.17kW

Upto

1.14kVA

Upto 0.4

kVAR

0.3 to

1 Leading

Oven 32.0 3 5,7,9 220.9V 6.68A 50.3Hz 1377.5W 1470VA 510KVAR 0.99 Lagging

LED Bulb (2.5W) 31.3 3 5, 7, 9, 11, 13 225.3V 0.047A 49.8 Hz 2.5W 10.5VA 10.25VAR 0.24 Leading

LED Bulb (7W) 16.1 3 5, 7, 9, 11 228.6V 0.31A 50Hz 7.1W 7.5VA 2VAR 0.95 Leading

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Device

THD

(Current) %

Most

Dominant

harmonic

order

Other harmonics

Supply

Voltage

(volt)

Current

Drawn

(amp)

Frequency

(Hz)

Output

Power

(Watt)

Input

Power

(Volt-

amp)

Reactive

Power

(Var)

Power Factor

Refrigerator Conventional Type

8.8 3 7,9 228.6V 1.065A 50.4 Hz 146W 243VA 194.25VAR 0.6 Lagging

Fan rotating at max. speed

6.0 3 5 228.5V 0.33A 49.7 Hz 75.25W 76VA 9.75VAR 0.99 Leading

Fan rotating at slow speed

5.2 3 NIL 230V 0.165A 49.8 Hz 14.75W 37.75VA 34.75VAR 0.39 Leading

Table Fan 3.0 3 NIL 234V 0.263 A 50 Hz 61.5W 61.7 VA 5.1 VAR 0.995 Lagging

Note: Above Mentioned Observations are typical & indicative in nature

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5.5 Planning Power Quality Field Measurement

Importance of Power Quality is been well understood internationally and appropriate

methods have been developed and employed to ensure quality power. In India, regulatory

agencies have notified required standards and regulation. In the implementation arena, how it

is performing is yet to be assessed. In this direction, to establish base line date about Power

Quality parameters in the Indian Power system, Power quality measurement were taken up by

POWERGRID at the Grid level starting from its own sub-stations across all the five regions in

the country covering all the states and union territories. In this endeavour Power Quality

measurement of various household appliances, typical office building, and distribution

substations were also carried out. Results are presented in the following section. A brief

description of measurement procedure and necessary set-up is given in following section.

5.5.1 Measurement Procedure

In the low tension (415 Volt AC) network, to measure various power quality parameters

such as phase wise currents, voltages, harmonics, sag / swell, interruptions etc. suitable

voltages and currents probe shall be connected directly in the electrical circuits carrying load

current. However, in the high voltage (above 11 kV) network, to measure various power quality

parameters such as phase wise currents, voltages, harmonics, sag / swell, interruptions etc.

suitable voltage and current probes (according to the magnitude of current) shall be connected

in the secondary circuit i.e. to the measurement core output of CTs and PTs used for local

measurement purposes.

5.5.2 Set up

Setting up the instruments to collect power quality data is probably the most critical aspect

of measurement. Utmost care must be taken while setting up the analyser. The first step is to

make sure that all the safety rules are being followed. In the majority of cases, power to

electrical equipment cannot be turned off to allow for the instrument setup. The facility users

cannot allow any interruption. Opening the covers of electrical switchboards and distribution

panels requires diligence and patience. While removing panel covers and setting up instrument

probes it is important to have someone else present in the room. The second person may not be

trained in power quality measurement but should have some ‘know-how’ about electrical

systems and the hazards associated with it.

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When connecting voltage probes, the connections must be secure. Loose connections are prone

to intermittent contact, which can produce false indications of power quality problems. Voltage

and current probe leads should be periodically inspected. Leads with damaged insulation or

those that look suspect must be promptly replaced to avoid dangerous conditions. While

making current measurements, one of the main causes of errors is improper closing of the jaws

of the probe. Substantial errors in current measurements and phase angles can be produced due

to air gaps across the jaws of the current probes. While carrying out power quality

measurements, suitable current probes shall be selected depending upon the magnitude of

current. Power Quality Measurement can be carried out in two modes, i.e. either for real time

snapshot monitoring (spot measurement) or for recording purpose. When Power Quality

Measurement is done in recording mode, desired power quality parameters such as voltage

sag/swell, transients, percentage over / under voltage, flicker, power factor, harmonics, voltage

unbalance, inrush current shall be selected. Care must be taken to select triggers for event

detection. Also interval time for sampling and duration of measurements are to be selected.

While in the monitoring mode, voltage and current wave forms, harmonics, etc. can be directly

viewed on the PQA screen.

It is important to note that the user of the instrument must be well trained in the use and care

of the instrumentation. The engineer should be knowledgeable in the field of power quality

measurement. Most importantly, the engineer should be safety conscious. All these factors are

equally important in solving power quality problems.

5.5.3 Power Quality Data Management

The Power-Quality measurements have been done at more than 175 different cities/towns

covering all the states of India which in turn has measured the Power Quality of more than 500

different feeders/points and archived a Database of more than 100 GB. Portable Power Quality

Analysers (Class-A) were used in all these measurements. The data collected from such

measurements has been archived in the form of csv files (one file for each measurement). The

integrity of the Data has been maintained by using proper naming conventions for the csv files.

Automated Reporting template has been developed in MS-Excel to automatically pull

the data from csv files and generate a report for a given substation/location. The same Database

is also being used by Power Quality Dashboard which shows the various Power-Quality

parameters in the form of graphs, charts, maps etc. These graphs, charts, maps etc. have been

used in this report to depict the Quality of Power across India.

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This model of Analytics and reporting can be further be used to develop online dashboard

which would show the status of Power Quality in India on real time basis. This can be done by

simply putting the latest measurements in the form of new csv files and treating older files as

historical data. A huge amount of information can be extracted from such a volume of data

which would help the Utilities/DISCOMs in various decision making activities like installation

of PQ-Interface devices, capacity addition, system strengthening etc.

IEEE Std 1159.3-2003, “IEEE Recommended Practice for the Transfer of Power Quality

Data”[37] provides the power quality industry with the specification for PQDIF (Power Quality

Data Interchange Format), which is an open and accepted data format standard for the transfer

of power quality data between instruments and computers.

This transfer standard allows the processing and analysis of power quality measurements

using multi-vendor and multi-device data. Wider acceptance of PQDIF as a power quality data

transfer format will significantly add to the value of power quality monitoring and open new

Figure 5-2: PQ Data Management, Reporting & Analytics (Power Quality Dashboard)

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opportunities for the resolution, planning, and understanding of power quality activities. Being

able to exchange data between software systems will allow other functions needed in a power

quality monitoring campaign, including validation, trending, comparison, overlay, and more.

The IEEE 1159.3 Task Force is revising IEEE Std 1159.3-2003, IEEE Recommended Practice

for the Transfer of Power Quality Data (PQDIF). It has been planned to complete the majority

of the revision work in 2015 and 2016 and to begin balloting in 2017.

‘Electrotech Concepts’ & ‘EPRI’ have jointly developed a multi-component software

system, named PQView for building and analysing databases of power, power quality, and

energy measurements. It integrates data from digital relays, digital fault recorders, power

quality monitors, smart meters, and SCADA historians into an open relational database. It can

build databases with billions of measurements from thousands of monitoring points taken by

many different types of meters, including power quality monitors, voltage recorders, in-plant

monitors, and digital fault recorders.

It can store and analyse information with the measurements about cause and source of

triggered events, as well as evaluate the financial impact of events to the Utilities/DISCOMs

as well as the End-Users. The major components of this package are: 1) Fault Analysis

Modules, 2) Report Writing Modules & 3) Answer Modules.

5.6 Field Measurement of Power Quality Parameters at EHV Grid

Substations

To establish the base line data about Power Quality at high voltage level in India, Power

Quality parameters such as THD & individual harmonics, Unbalance, DC off set, Sag/swell,

interruptions etc. were measured at 175 cities/towns at EHV level grid substations of all the

five regions in India from April 2014 to May 2015. Harmonics content in the voltage and

current waveforms at bus voltages were measured and recorded. In general it is observed that

even order harmonics are either absent or negligible at EHV grid stations.

5.6.1 Power Quality Observation at 765 kV:

At 765 kV level Power Quality measurement was carried out at 26 cities/towns. Based

on measurement, it can be seen that average THD observed in voltage waveform at 765 kV

voltage level varies from 0.44% to 1.17% against the limit of 1.5%.

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Figure 5-3: Average Voltage Harmonic Spectrum at 765 kV across India

Figure 5-4: Duration curve of Voltage THD at 765kV across India

Average voltage Harmonic spectrum at 765kV and its duration curve is shown Figure 5-3 and

Figure 5-4 respectively. It can be observed that most dominant voltage harmonic observed at

765 kV is 5th harmonic and for a very short duration i.e. 0.63% of time THD goes beyond

1.5% as shown in duration curve at Figure 5-4. High THD level were observed at Gaya, Moga,

Solapur, Raichur, Jabalpur substations.

Total Harmonic Distortion and Individual Harmonics observed at 765kV level are

summarised in Table 5-3 (only top 20 locations). A geographic representation of average THD

at 765 kV across India is shown in Figure 5-5.

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Figure 5-5: Average Voltage THD at 765kV Level

It can be seen that THD observed in voltage waveform at 765 kV voltage level varies

from 0.44% to 1.03%. It can also be seen that THD as well as individual harmonics of any

particular order in the voltage waveform at 765 kV is within the limit set by CEA[8].

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Table 5-3: THD & Individual Harmonics in Voltage at 765 kV

S. No.

Substation

(765 kV

Label)

Voltage Harmonic Content (% of Fundamental)

THD 3rd 5th 7th 11th 13th

Limit as per CEA

Tech. Standard for

Grid Connectivity

2007[8]

1.5 1.0

1. Solapur 1.03 0.6 0.7 0.1 0.0 0.1

2. Sasaram 0.99 0.3 0.6 0.1 0.4 0.2

3. Raichur 0.99 0.6 0.7 0.0 0.0 0.0

4. Jabalpur Pool 0.99 0.1 0.8 0.2 0.0 0.1

5. Gaya 0.96 0.5 0.4 0.2 0.3 0.1

6. Bhiwani 0.92 0.2 0.7 0.2 0.2 0.1

7. New Ranchi 0.84 0.5 0.5 0.1 0.0 0.0

8. Nellore P 0.80 0.2 0.6 0.2 0.0 0.1

9. Sundergarh 0.78 0.4 0.4 0.2 0.1 0.1

10. Agra 0.75 0.3 0.5 0.0 0.2 0.2

11. Indore 0.72 0.0 0.4 0.3 0.1 0.3

12. Kurnool 0.69 0.4 0.2 0.1 0.2 0.2

13. Fatehpur 0.64 0.3 0.3 0.2 0.1 0.1

14. Wardha 0.63 0.5 0.1 0.0 0.0 0.0

15. Jhatikara 0.62 0.2 0.2 0.1 0.4 0.1

16. Bilaspur 0.60 0.3 0.3 0.0 0.2 0.1

17. Kotra 0.57 0.3 0.3 0.1 0.1 0.1

18. Tamnar 0.55 0.2 0.3 0.0 0.1 0.0

19. Meerut 0.50 0.1 0.2 0.2 0.1 0.1

20. Gwalior 0.50 0.3 0.2 0.0 0.0 0.1

Typical daily trend in average variation of Voltage harmonics observed at 765 kV across

the country, based on power Quality measurement made at POWERGRID substations is shown

in Figure 5-6. It can be observed that most dominant voltage harmonic observed at 765 kV is

5th harmonic.

Figure 5-6: Typical Average Voltage Harmonics daily Trend at 765 kV across the country

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At 400 kV level Power Quality measurement was carried out at 144 locations. An overview

of THD observed in voltage waveform at 400 kV POWERGRID sub-stations in India is shown

in Figure 5-7.

Figure 5-7: Average THD in Phase Voltages at 400 kV Level

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Figure 5-8: Duration Curve-400kV Voltage THD


It was found that average THD in the voltage at 400 kV locations varies from 0.11% to

3.3% against the limit of 2%. It can be seen from the duration curve of THD in voltage at 400

kV that only 3.6% of time THD was beyond the specified limit as shown in Figure 5-8. High

THD was mainly observed at Kala, Vapi, Nausari, Magarwara, Udupi, Chamba, Panchkula,

Meerut, Arasur, Bhadrawati, Agra, Keonjhar, Rengali out of the 144 locations where Power

Quality Measurement were done. Average voltage Harmonic spectrum of 400 kV level shown

in Figure 5-9 and Typical Average Voltage Harmonics daily Trend shown in Figure 5-10

indicates that most dominant harmonics at this voltage level are 3rd & 5th.

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It has been observed that voltage harmonic distortion in the Grid is generally more at weak

nodes & less at stronger nodes. The nodes which are more meshed up with multiple connections

are comparatively stronger (e.g. central India) and hence show less distortion in voltage

waveform. It can be said that the nodes where current harmonics are injected in the grid need

not necessarily have high values of harmonics in the voltage. The effect of these current

harmonics is seen on the comparatively weaker nodes in the grid.

Summary of Total Harmonic Distortion and Individual Harmonics observed at 400kV level

are given in Table 5-4 (only top 20 locations).

Table 5-4: Max THD & Individual Harmonics observed in Voltage at 400 kV

S. No. Substation

(400 kV Level)



Limit as per CEA Tech. Standard for Grid

Connectivity 2007[8]

2.0 1.5

1 Magarwada 3.30 0.3 3.2 0.3 0.1 0.2

2 Jalandhar 2.63 1.3 0.5 0.5 0.2 0.4

3 Kala 2.56 0.2 2.4 0.1 0.3 0.3

4 Kaithal 2.41 0.8 0.5 1.7 0.4 0.3

5 Navsari 2.34 0.4 2.2 0.2 0.1 0.0

6 Vapi 2.28 0.5 2.1 0.4 0.2 0.0

7 Keonjhar 2.08 0.5 0.2 0.1 1.8 0.6

8 Kotputli 1.91 0.1 0.4 0.2 1.7 0.2

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S. No. Substation

(400 kV Level)



Limit as per CEA Tech. Standard for Grid


2.0 1.5

9 Talcher 1.73 0.2 0.5 0.1 0.9 1.2

10 Abdullapur 1.72 1.4 0.6 0.3 0.1 0.0

11 New Purnea 1.62 1.2 0.6 0.5 0.1 0.1

12 Kolar 1.56 0.6 0.8 0.2 0.4 0.5

13 Thrissur 1.56 0.5 1.3 0.3 0.0 0.0

14 Pirana 1.53 0.4 1.2 0.6 0.1 0.0

15 Vizag 1.52 0.4 1.1 0.5 0.3 0.2

16 Hyderabad 1.50 0.6 0.9 0.6 0.1 0.0

17 Nallagarh 1.45 0.9 1.0 0.4 0.0 0.0

18 Cochin 1.41 0.4 1.2 0.5 0.0 0.0

19 Amritsar 1.41 0.6 0.8 0.6 0.2 0.0

20 Vindhyachal HVDC 1.41 0.2 0.4 1.2 0.1 0.1

Voltage Unbalance:

Voltage unbalance observed in the

voltages at 400 kV varies from 0.04% to

5.00% against the permissible limit of 1.5%

set by CEA for 400 kV & 765kV [8].

Overview of unbalance in 400 kV voltage

level is shown in Figure 5-11. It is to be

noted that a small Voltage unbalance can

create a large current unbalance, 6 to 10

times the magnitude of voltage unbalance.

Figure 5-11: Average Voltage Unbalance at

400 kV

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Harmonics in Current:

Overview of THD observed in three phase and neutral currents of various feeders at 400

kV substations are shown in Figure 5-12. It was found that at most of the locations THD in

phase and neutral currents are very high. Literature survey shows that current THD may be

misleading in case of light load. Loads on the lines varies over a wide range, due to diurnal

variation in the load and on several occasion transmission lines are lightly loaded during lean

period.

Figure 5-12: Average THD in Phase and Neutral currents at 400 kV Substations across India

The most common harmonic index, which relates to the voltage waveform, is the THD,

which is defined as the root mean square (r.m.s.) of the harmonics expressed as a percentage

of the fundamental component, i.e.

𝑇𝐻𝐷 = √∑ 𝑉𝑛2𝑁

𝑛=2

𝑉1

Where Vn is the single frequency r.m.s. voltage at harmonic n, N is the maximum harmonic

order to be considered and V1 is the fundamental line to neutral r.m.s. voltage. In general N is

taken up to the 50th harmonic.

Although, current harmonic may also be represented as THD, it might be misleading in

case of light load. A high THD value for current may not be of significant concern if current

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value is low, since the magnitude of harmonic current is less although the ratio of this taken to

the fundamental component might be high. To avoid such ambiguity, a different index, Total

Demand Distortion (TDD), which is more commonly used for representing current harmonic

level is defined as:

𝑇𝐷𝐷 = √∑ 𝐼𝑛2𝑁

𝑛=2

𝐼𝑅

Here the distortion is represented as a percentage of the rated or maximum load current,

instead of the fundamental current. Since electrical power system is designed to withstand the

rated or maximum load current, the impact of current distortion on the system will be more

realistic if the assessment is based on the designed values, rather than on a reference that

fluctuates with the load levels.

Due to these reasons, TDD is used instead of THD for expressing current harmonics. The

limits provided in the standard IEEE-519 also gives the current harmonic values in terms of

TDD. In this view, TDD was calculated for voltage current waveform for all the current

measurements made during our field visit. Calculated value of TDD with respect to current

THD measurement is given in volume 2 of this report.


At 220/230 kV level Power Quality measurement was carried out at 111 locations. An

overview of THD observed in voltage waveform at 220 kV POWERGRID sub-stations in India

is shown at Figure 5-13. Summary of Total Harmonic Distortion and Individual Harmonics

observed at 400kV level are given in Table 5-5. It can be seen that THD observed in voltage

waveform at 220kV voltage level mostly lies within the limit set by CEA except for few

locations.

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Figure 5-13: THD in Phase Voltages at 220 kV Level

Figure 5-14: Duration Curve-220kV Voltage THD

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It was found that average THD in the voltage at 220 kV locations varies from 0.1% to 2.9%.

Refer Table 5-5. It can be seen from the duration curve of THD in voltage at 220 kV that only

1.56% of time THD was beyond the specified limit as shown in Figure 5-14. Average voltage

Harmonic spectrum of 220 kV level shown in Figure 5-15 and Typical Average Voltage

Harmonics daily Trend shown in Figure 5-16 indicates that most dominant harmonics at this

voltage level are 3rd & 5th.


Table 5-5: Max THD & Individual Harmonics in Voltage at 220 kV

Sl No.

Substation (400 kV Label)



Limit as per CEA Tech.

Standard for Grid


2.0 1.0

1 Hassan 2.93 3.0 2.8 2.8 2.7 2.7

2 Khammam 2.86 2.5 1.1 0.3 0.0 0.0

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Sl No.

Substation (400 kV Label)



Limit as per CEA Tech.

Standard for Grid


2.0 1.0

3 Abdullapur 2.46 2.0 1.0 0.6 0.1 0.1

4 Satna 2.22 1.6 1.3 0.4 0.0 0.0

5 Mapusa 2.22 2.0 0.6 0.2 0.1 0.0

6 Navsari 2.12 1.1 1.7 0.1 0.0 0.0

7 Vapi 1.94 0.5 1.7 0.3 0.2 0.0

8 Baripada 1.82 0.5 1.3 0.7 0.3 0.1

9 Nallagarh 1.78 0.6 1.4 0.6 0.1 0.0

10 Ara 1.77 0.9 1.0 0.8 0.2 0.1

11 Bhachau 1.76 0.5 1.6 0.1 0.1 0.0

12 Raebareli 1.74 0.2 0.4 1.6 0.3 0.0

13 Palakkad 1.64 1.2 0.9 0.2 0.0 0.0

14 Muzaffarpur 1.62 1.0 0.9 0.3 0.1 0.1

15 Hyderabad 1.61 0.7 0.9 0.8 0.0 0.0

Voltage Unbalance:

Voltage Unbalance observed in the voltages at 220 kV varies from 0.06% to 3.18% against

the permissible limit of 2% set by CEA for 220kV [8]. Overview of unbalance in 220 kV voltage

level is shown in Figure 5-17.

Figure 5-17: Voltage Unbalance at 220 kV

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5.7 Region-Wise Summary of Power Quality Measurements in India

5.7.1 Summary of Power Quality Measurement in Eastern Region

Power Quality measurements have been carried out at 33 different cities/towns covering all

states in Eastern Region. An overview of voltage harmonics, current harmonics, power factor,

voltage unbalance and other events observed at different voltage levels in the Eastern region is

presented in the following section. Detailed observation is given in Volume-2 of this report.

Power Quality in 765kV Network:

VOLTAGE HARMONICS

Figure 5-18: Average Voltage Harmonics measured in Eastern Region (at 765kV)

CURRENT HARMONICS

Figure 5-19: Average Current Harmonics measured in Eastern Region (at 765kV)

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POWER FACTOR

Power Factor at 765 kV feeders remains below 0.8 for about 84% of the time as depicted

in Figure 5-20.

Figure 5-20: Overall power factor duration curve (At 765 kV level)

UNBALANCE

There is negligible voltage unbalance at 765 kV level. Voltage unbalance remains below

1.5% for almost all the time.

Figure 5-21: Voltage unbalance duration curve (At 765 kV level)

EVENTS

No of Voltage Sags captured during measurement= 3

No of Swell captured during measurement = 0

No of Interruption captured during measurement = 0

No of Voltage Transients captured during measurement = 0

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It may be deduced from the above, that the Quality of Power at 765kV (in the Eastern Region)

is well within the prescribed norms/standards. The low power-factor is not an issue as such

because the 765kV lines have very high capacities & large lengths which generate reactive

power of their own and moreover the lines are lightly loaded as compared to the ratings of the

lines, all these factors lead to low power factor.


VOLTAGE HARMONICS

Figure 5-22: Average Voltage Harmonics measured in Eastern Region (400kV)

CURRENT HARMONICS

Figure 5-23: Average Current Harmonics measured in Eastern Region (400kV)

POWER FACTOR

Power Factor at 400 kV level remains more than 0.8 for 60% of the time as depicted in Figure

5-24.

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Figure 5-24: Avg. power factor duration curve

UNBALANCE

The Voltage Unbalance is found to be less than 1.5% (CEA limit) for more than 99% of

the time (Figure 5-25). It shows that there is negligible unbalance in 400 kV network.

Figure 5-25: Voltage unbalance duration curve (At 400kV)

EVENTS

No of Sag captured = 6

No of Swell captured = 0

No of Interruption captured = 1

No of Transients captured = 0

As per all the field measurements, it can be deduced that the Quality of Power (at 400kV)

is well within prescribed norms/standards. The Voltage Sags and 5th Harmonic component

in current need to be addressed.

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VOLTAGE HARMONICS

Figure 5-26: Average Voltage Harmonics measured in Eastern Region (at 220kV)

CURRENT HARMONICS

Figure 5-27: Average Current Harmonics measured in Eastern Region (at 220kV)

POWER FACTOR

Overall Power Factor at 220 kV network is good. It is observed to be above 0.8 for nearly

75% of the time as depicted in Figure 5-28.

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Figure 5-28: Overall power factor duration curve at 220 kV level

UNBALANCE

Overall Voltage unbalance at 220 kV network is on the higher side. As per the duration

curve of Figure 5-29 unbalance is greater than 2% for nearly 10% of the time.

Figure 5-29: Overall voltage unbalance duration curve at 220 kV level

EVENTS





As per all the field measurements, it can be deduced that the Quality of Power (at 220kV)

is well within prescribed norms/standards. The events like Voltage Sag& Voltage Swell are

very frequent, which need to be addressed. The 5th Harmonic component in current also

needs some mitigation.

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VOLTAGE HARMONICS

Figure 5-30: Average Voltage Harmonics measured in Eastern Region (132kV)

CURRENT HARMONICS

Figure 5-31: Average Current Harmonics measured in Eastern Region (132kV)

POWER FACTOR

Overall Power Factor at 132 kV network is good. It is observed to be above 0.8 for nearly

78% of the time as depicted in Figure 5-32.

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Figure 5-32: Overall power factor duration curve at 132 kV level

UNBALANCE

Overall voltage unbalance in 132 kV network keeps below limit (2%) for about 19% of the

times which can be clearly seen in Figure 5-33.

Figure 5-33: Voltage unbalance duration curve at 132 kV level

EVENTS





As per all the field measurements, it can be deduced that the Quality of Power (at 132kV) is

well within prescribed norms/standards. The Voltage Sags and 5th Harmonic component in

current need to be addressed.

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Power Quality in 415V Network:

VOLTAGE HARMONICS

Figure 5-34: Average Voltage Harmonics measured in Eastern Region (415V)

5.7.2 Summary of Power Quality Measurement in Northern Region

Power Quality Measurements have been carried out at 53 different locations in various

cities/towns of Northern Region covering all the states.

5.7.2.1 Power Quality in 765kV Network:

VOLTAGE HARMONICS

Figure 5-35: Average Voltage Harmonics at 765 kV

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CURRENT HARMONICS

Figure 5-36: Average Current Harmonics at 765 kV

POWER FACTOR

Power Factor at 765 kV feeders remains below 0.8 for about 84% of the time as depicted in

Figure 5-37.

Figure 5-37: Power Factor duration curve (At 765kV)

UNBALANCE

There is negligible voltage unbalance at 765 kV level. Voltage unbalance remains below

0.8% for almost all the time.

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Figure 5-38: Unbalance Duration Curve (At 400kV)

EVENTS






VOLTAGE HARMONICS

Figure 5-39: Average Voltage Harmonics (at 400kV)

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CURRENT HARMONICS

Figure 5-40: Average Current Harmonics (at 400kV)

POWER FACTOR

The Power Factor at 400kV is found to be above 0.8 for about 60% of the times as depicted

in Figure 5-41.

Figure 5-41 : Power Factor Duration Curve (At 400kV)

UNBALANCE

Voltage unbalance exceeds the Unbalance-Limit “1.5%” for about 2.5% of times (Figure

5-42).

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Figure 5-42 : Unbalance Duration Curve (At 400kV)

EVENTS






VOLTAGE HARMONICS

Figure 5-43 : Average Voltage Harmonics measured (at 220kV)

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CURRENT HARMONICS

Figure 5-44 : Average Current Harmonics measured (at 220kV)

POWER FACTOR

The power factor in 220kV keeps above 0.8 for about 81% of the times (Figure 5-45).

Figure 5-45 : Power Factor duration Curve (At 220kV)

UNBALANCE

As shown in the duration curve (Figure 5-46) unbalance is within the limit for almost all

the time.

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Figure 5-46 : Avg. Voltage Unbalance Duration Curve (At 220kV)

EVENTS





5.7.2.4 Power Quality in 415V LT Supply:

VOLTAGE HARMONICS

Figure -5-47 : Average voltage harmonics in 415V LT supply

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5.7.3 Summary of Power Quality Measurement in Western Region

Power Quality Measurements were carried out at POWERGRID substations in 33 cities/towns

in the Western Region.


VOLTAGE HARMONICS

Figure 5-48 : Average Voltage Harmonics (at 765kV)

CURRENT HARMONICS

Figure 5-49 : Average Current Harmonics (at 765kV)

POWER FACTOR

Power Factor at 765 kV feeders remains above 0.8 for 85% of the time.

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Figure 5-50: Overall power factor duration curve (At 765 kV)

UNBALANCE

The Voltage Unbalance is found to be well within limits at 765 kV level (Figure 5-51).

Figure 5-51: Voltage unbalance duration curve (At 765 kV)

EVENTS






VOLTAGE HARMONICS


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CURRENT HARMONICS

Figure 5-53 : Average Current harmonics (at 400kV)

POWER FACTOR

Power Factor at 400 kV level remains more than 0.8 for 70% of the time as depicted in

Figure 5-54.

Figure 5-54 : Power Factor duration curve (At 400 kV)

UNBALANCE

The measurements at 400kV show that the voltage unbalance exceeds the value “1%” for

about 1.6% of times.

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Figure 5-55: Unbalance Duration Curve (At 400kV)

EVENTS






VOLTAGE HARMONICS


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CURRENT HARMONICS

Figure 5-57 : Average Current Harmonics (at 220kV)

POWER FACTOR

The power factor in 220kV remains above 0.8 for about 83% of the times

Figure 5-58 : Power Factor duration Curve (at 220kV)

UNBALANCE

The Unbalance at 220kV is well within limits as shown in Figure 5-59.

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Figure 5-59: Unbalance Duration Curve (at 220 kV)

EVENTS





5.7.3.4 Power Quality in LT Network:

Average voltage harmonics in LT network is as shown in Figure 5-60.

Figure 5-60: Average Voltage Harmonics in LT Network

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5.7.4 Summary of Power Quality Measurement in Southern Region

Power Quality Measurements were carried out at 38 POWERGRID substations in of

cities/towns in the Southern Region.


VOLTAGE HARMONICS

Figure 5-61: Average Voltage Harmonics measured (at 765kV)

CURRENT HARMONICS

Figure 5-62: Average current harmonics measured at 765 kV

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POWER FACTOR

The average Power Factor at 765kV level lines/Equipment in south region is found to be

above 0.8 for about 63% of the measured time

Figure 5-63: Average Power Factor duration curve (at 765 kV)

UNBALANCE

Unbalance observed to be within limit for almost all the times.

EVENTS






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VOLTAGE HARMONICS

Figure 5-64: Average Voltage Harmonics measured at 400 kV

CURRENT HARMONICS

Figure 5-65: Average Current Harmonics measured at 400 kV

POWER FACTOR

The Average power factor in 400kV voltage level in south region is above 0.8 for about

60% of the measurement time.

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Figure 5-66: Average Power Factor in 400 kV

UNBALANCE

Unbalance in the 400 kV level network in south region is within the limits.

Figure 5-67: Average Voltage Unbalance (Vn%) in 400 kV

EVENTS






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VOLTAGE HARMONICS

Figure 5-68: Average Voltage Harmonics Measured at 220/230KV

CURRENT HARMONICS

Figure 5-69: Average current harmonics at 220 kV

POWER FACTOR

The power factor in 220kV remains above 0.8 for about 83% of the times

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Figure 5-70: Power Factor duration Curve (at 220kV)

UNBALANCE

The Unbalance at 220kV is well within limits as shown in Figure 5-71.

Figure 5-71: Unbalance Duration Curve (at 220 kV)

EVENTS





5.7.4.4 Power Quality in Low Tension Network:

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VOLTAGE HARMONICS

Figure 5-72: Average Voltage Harmonics Measured at LT Network

5.7.5 Summary of Power Quality Measurement in North-Eastern Region

Power Quality measurements have been carried out at 14 different cities/towns covering all

states in North-East Region.


VOLTAGE HARMONICS

Figure 5-73: Individual Voltage harmonics at 400kV

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CURRENT HARMONICS

Figure 5-74: Individual Current harmonics at 400kV

POWER FACTOR

The Power Factor at 400kV is found to be above 0.8 for about 42.6% of the times

Figure 5-75: Power factor duration curve at 400 KV

UNBALANCE

Unbalance observed was within limit for all the times which can be clearly seen in Figure 5-76.

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Figure 5-76: Unbalance duration curve at 400kV

EVENTS






VOLTAGE HARMONICS

Figure 5-77: Individual Voltage Harmonics measured at 220kV

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CURRENT HARMONICS

Figure 5-78: Individual current harmonics at 220kV level

POWER FACTOR

Figure 5-79: Power factor duration curve at 220kV

The power factor in 220kV keeps above 0.8 for about 67.9% of the times.

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UNBALANCE

Figure 5-80: Voltage unbalance duration curve at 220kV

Unbalance observed was within limit for all the time as shown in Figure 5-80.

EVENTS






VOLTAGE HARMONICS

Figure 5-81: Individual voltage harmonics at 132kV level

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CURRENT HARMONICS

Figure 5-82: Individual current harmonics at 132kV

POWER FACTOR

Power factor is observed to be more than 0.8 for more than 66% of the times.

Figure 5-83 : Power factor duration curve at 132kV

UNBALANCE

Unbalance observed to be less than 2% for about 97% of the times.

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Figure 5-84 : Unbalance duration curve at 132kV

EVENTS





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5.8 Power Quality Measurement in Typical Buildings

Power Quality Measurements were carried out on LT feeders of a typical office building &

two different residential complexes. It is observed that voltage & current in all the three (3)

phases of these feeders’ contain odd harmonics of the order of 3rd, 5th, 7th, 11thand so on. To

get the profile of Power quality parameters variation over a period, say whole day, power

quality measurement / recording was carried out for 24 hours or more. It is observed that PQ

parameters such as harmonics, unbalance etc. varies over a wide range depending on the loads

connected. Various events like sag, swell, transients, interruptions, flicker etc. were also

observed during the measurement period. Among the various harmonics present 3rd harmonics

was most dominant followed by 5th, 7th, 9th, 11th etc. Even harmonics were mostly absent, even

if it was there the content was negligible. Large neutral current and high unbalance in the phase

currents were also observed. Sometimes, DC component were also observed in the phase and

neutral current. Voltage Harmonics within the various feeders of a typical office building is

given in Table 5-6and current harmonics in Table 5-7.

Table 5-6: Voltage Harmonics distribution in a Typical Office Building Power Supply

Feeder

Voltage Harmonics (%)

Phase THD DC Component 3rd 5th 7th 11th

Ground Floor

Lighting feeder

R phase 0.84 0.04 0.32 0.98 0.42 0.16

Y phase 0.89 0.09 0.45 0.38 0.42 0.13

B phase 0.89 0.08 0.37 0.35 0.47 0.17

Neutral 71.31 10.68 41.79 14.80 28.41 15.20

UPS feeder

R phase 0.95 0.06 0.38 0.37 0.46 0.12

Y phase 1.01 0.13 0.51 0.41 0.47 0.12

B phase 1.03 0.12 0.43 0.40 0.53 0.15

Neutral 67.68 16.58 25.83 13.37 28.07 22.54

Air Conditioning plant feeder

R phase 0.94 0.04 0.31 0.42 0.43 0.09

Y phase 1.02 0.08 0.50 0.46 0.47 0.11

B phase 0.98 0.07 0.34 0.46 0.50 0.12

Neutral 46.39 3.73 20.40 13.66 22.72 13.22

Table 5-7: Current Harmonics distribution in a Typical Office Building Power Supply

Feeder

Current harmonics (%)


Ground Floor

R phase 9.66 1.66 7.96 1.11 2.08 0.91

Y phase 11.26 2.47 10.39 0.94 2.05 0.64

B phase 12.40 3.24 9.71 1.45 3.39 1.22

Neutral 85.88 5.04 83.81 2.41 2.75 3.08

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Feeder



UPS

R phase 15.35 4.82 3.70 6.09 11.69 4.29

Y phase 16.10 5.01 3.75 6.05 12.68 3.97

B phase 16.23 5.04 3.12 7.26 12.18 3.98

Neutral 17.04 122.01 10.15 4.99 3.60 1.84

AC

R phase 5.04 9.95 1.91 3.00 1.82 0.99

Y phase 8.36 31.29 3.54 3.59 2.14 1.20

B phase 1.92 138.91 12.62 9.41 6.20 3.77

Neutral 32.65 108.93 19.84 13.79 8.73 5.91

It can be observed that although harmonic content (THD as well as individual harmonic)

in the phase voltages are low, but neutral voltage has a very high content of THD as well as

individual Harmonics (3rd, 5th, 7th, 11th etc.) indicating the presence of large volume of non-

linear loads in the office. Harmonic Spectrum of Voltage at the point of common coupling

(PCC) i.e. LT Bus of distribution supply of the Office Building is shown in Figure 5-85. High

content of odd harmonics (3,5,7, 9,11, …) in the phase and neutral currents further indicates

the presence of large volume of non-linear devices in the office building. In the voltage

waveform DC offset as well as even harmonics are negligible.

Figure 5-85: Harmonic Spectrum of Voltage at PCC of the Office Building

High content of DC component is also present in the office loads (lights, UPS & AC)

supply. Harmonic Spectrum of currents in the lighting, UPS and Air Conditioning plant feeders

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are shown in Figure 5-87 & Figure 5-88 respectively. In the lighting feeder it can be observed

that in all the phase currents 3rd harmonics of the order of 8-10% is present and in the neutral

current 3rd harmonic content is very high of the order of 80%. Other odd harmonics of the order

of 5th, 7th, 17th, 19th, 23rd, 25th & so on can also be observed in the office building light currents.

Traces of DC component and even harmonics can also be observed in the current harmonic

spectrum of lighting feeder.

Figure 5-87: Harmonic Spectrum in lighting current of a Typical Office building containing

CFL, Fluorescent & LED lamps

Figure 5-86: Harmonic Spectrum in UPS supply feeder of a Typical Office building

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Harmonic Spectrum of the on UPS feeder of the office building, supplying mainly to

the Personal Computers, Printers, Laptops, network switches and other IT appliances, shows

dominant 5th& 7th Harmonics, other higher harmonics, like 11th, 13th, 23rd, 25th, etc. can also

be seen besides 3rd harmonic in the input supply feeder of UPS supply. The DC component

observed in the phase currents were relatively higher than that observed in the lighting circuit,

in the neutral current the percentage of DC component is very high, refer figure-4-5.

Figure 5-88: Harmonic Profile &Spectrum in the current of Air Conditioning plant feeder of

a Typical Office building

Harmonic spectrum of the current supplying Air-conditioner plant contains mainly 3rd

harmonic and a very high component of DC content.

5.9 Power Quality Measurement at a 132/33 kV Distribution substation

Power Quality measurements were also carried out at a typical 132/33kV substation of a

state utility in rural area. Summary of power quality measurement at 33 kV side is shown in

Table 5-8, Table 5-9 and Figure 5-89.

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Table 5-8: Voltage Harmonics distribution at a Typical 132/33 kV S/Stn on 33 kV Side

Feeder



33 kV Bus

Voltage

R phase 1.04 0.09 0.48 0.42 0.73 0.19

Y phase 0.82 0.07 0.29 0.60 0.39 0.14

B phase 0.88 0.06 0.12 0.79 0.23 0.13

Neutral 81.84 327.67 13.35 13.01 13.09 0.20

Table 5-9: Current Harmonics distribution at a Typical 132/33 kV S/Stn on 33 kV Side

Feeder Current harmonics (%)


33 kV KurungKumey

(Ziro S/S)

R phase 1.45 0.98 0.53 1.03 0.51 0.2

Y phase 1.46 0.94 0.47 0.75 0.96 0.31

B phase 1.19 0.81 0.19 0.63 0.71 0.28

Neutral 41.77 327.67 10.83 7.21 6.48 6.48

Figure 5-89: Voltage & Current Harmonic Spectrum on a 33 kV Feeder.

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Harmonic current observed in this rural feeder, indicates very low percentage (1-2 %) of

harmonic content in voltage and less than 1.5% in phase currents. However, the Voltage and

current waveform shows relatively higher content of 3rd, 5th, 7th, 11th& 13th Harmonics.

5.10 Power Quality Measurement on LT supply at various substations

Power Quality measurements were also carried out in the LT supply of various sub-stations,

where team visited for power quality measurement at High voltage level. Voltage & current

harmonics observed at one of the 132/33 kV sub-station in the north-eastern area is given in

Table 5-10 and Table 5-11 respectively.

Table 5-10: Voltage Harmonics in LT Supply of Substation

Feeder



LT (Ziro S/S)

R phase 1.15 0.10 0.56 0.46 0.81 0.13

Y phase 0.88 0.06 0.35 0.60 0.45 0.10

B phase 0.94 0.05 0.12 0.85 0.27 0.14

Neutral 86.30 247.80 14.09 13.60 13.84 13.91

Table 5-11: Current Harmonics in LT Supply of Substation

Feeder



LT (Ziro S/S)

R phase 10.73 0.44 2.34 9.48 3.80 0.20

Y phase 13.64 0.39 3.03 12.01 5.01 0.35

B phase 10.70 10.73 5.38 7.56 3.35 0.52

Neutral 14.77 55.45 4.18 2.29 2.26 2.29

Figure 5-90: Voltage Harmonic spectrum in LT Supply of Substation

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Figure 5-91: Overall Duration Curve for Total Harmonic Distortion at 415V

The measurements have been taken at LT/Auxiliary supply at more than 90 different

substations. The overall Total Harmonic Distortion (%f) exceeds the IEEE 519 std. limit for

about 5% of the times Figure 5-91. The values of Total Harmonic Distortion (THD), Short

Term Flicker (Pst) & Long Term Flicker (Plt) are shown in Table 5-12. In some of the

measurements THD has been recorded as high as 10%. Similarly Flicker (Pst & Plt) values

have been observed to be more than 2 while the limits for Pst & Plt are 1 and 0.65 respectively.

Table 5-12: THD, Pst & Plt measured in LT/Auxiliary Supply at various substations

Regio

n

Substatio

n

Average THD

(%f)

Average Short Term

Flicker (Pst)

Average Long Term

Flicker (Plt)

ER Muzaffarpur 3.92 NA NA

ER Jamshedpur 1.97 2.28 0.00

ER Ara 1.64 0.78 1.09

ER Purnea 1.46 0.76 2.22

ER Lakhisarai 1.38 1.57 2.67

ER New Purnea 0.87 0.12 0.11

ER Sasaram 0.85 0.27 0.00

ER New Ranchi 0.79 1.09 4.96

ER Ranchi 0.68 0.10 0.13

ER Jeypore 2.23 NA NA

ER Sundergarh 1.68 0.15 0.00

ER Keonjhar 1.58 NA NA

ER Rengali 0.82 NA NA

ER Baripada 0.64 NA NA

NER Srikona 1.82 0.71 NA

NER Aizawl 1.28 0.56 NA

NER Kumarghat 1.22 0.33 0.85

NER Jiribam 1.20 0.65 0.43

NER Badarpur 1.06 0.71 1.41

NER Misa 0.93 0.15 0.00

NER Khliehriat 0.89 0.55 0.25

NER Haflong 0.70 0.00 0.00

NR Kotputli 2.23 NA NA

NR Jaipur South 1.57 NA NA

THD limit as per IEEE 519 std. = 5%

5%

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Regio

n

Substatio

n

Average THD

(%f)

Average Short Term

Flicker (Pst)

Average Long Term

Flicker (Plt)

NR Gorakhpur 1.34 0.09 0.03

NR Sitarganj 1.26 0.42 0.56

NR Neemrana 1.10 0.17 0.00

NR Shahjahapur 0.98 0.32 0.78

NR Raebareli 0.98 0.39 0.00

NR Allahabad 0.86 0.25 0.32

NR Sohawal 0.69 0.07 0.04

NR Rihand HVDC 0.60 0.08 0.00

NR Bassi 0.59 0.09 0.12

NR Vindhyachal HVDC 0.58 0.23 0.00

NR Sikar 0.56 NA NA

NR Fatehpur 0.55 0.04 0.00

NR Bhinmal 0.55 0.04 0.00

NR Kankroli 0.54 0.03 0.00

NR Hamirpur 2.44 NA NA

NR Ludhiana 1.72 NA NA

NR Chamba 1.69 NA NA

NR Patiala 1.31 0.26 0.37

NR Banala 1.27 0.18 0.22

NR Jalandhar 1.26 NA NA

NR Mani Majra 1.18 0.12 0.21

NR Amritsar 1.03 0.21 0.21

NR Kishenpur 0.94 NA NA

NR Malerkotla 0.86 0.19 0.30

SR Munirabad 9.59 0.65 2.45

SR Vijayawada 3.14 0.08 0.04

SR Vizag 2.83 0.11 0.09

SR Nellore 2.21 0.30 0.28

SR Nellore Pool 2.03 0.13 0.12

SR Hyderabad 1.65 0.25 0.30

SR Kadapa 1.58 0.15 0.11

SR Warangal 1.53 0.15 0.13

SR Khammam 1.49 0.19 0.11

SR Gooty 1.41 0.20 0.29

SR Kurnool 1.31 0.34 0.18

SR Nagarjunasagar 1.11 0.27 0.24

SR Raichur 0.78 0.08 0.11

SR Arasur 2.74 0.11 0.10

SR Somanahalli 2.29 0.47 0.37

SR Madurai 2.01 0.23 0.17

SR Hosur 1.33 0.25 0.10

SR Thrissur 1.16 0.13 0.16

SR Tirunelveli 1.10 0.34 0.26

SR Kalivanthapattu 1.02 NA NA

SR Kolar 1.00 0.09 0.08

SR Bidadi 0.83 0.11 0.05

SR Mysore 0.81 0.12 0.09

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Regio

n

Substatio

n

Average THD

(%f)

Average Short Term

Flicker (Pst)

Average Long Term

Flicker (Plt)

SR Karaikudi 0.80 0.26 0.26

SR Salem 0.70 0.15 0.18

WR Raipur 10.78 0.21 0.16

WR Mapusa 1.39 0.35 0.41

WR Bhatapara 1.05 0.26 0.51

WR Shujalpur 9.15 NA NA

WR Satna 4.39 0.43 0.24

WR Navsari 4.39 0.21 0.21

WR Magarwada 3.24 0.16 0.14

WR Jabalpurpool 2.51 0.33 0.21

WR Jabalpur 2.09 0.14 0.13

WR Kala 1.85 0.22 0.16

WR Bhachau 1.78 0.25 0.27

WR Vapi 1.73 0.14 0.11

WR Bina 1.70 NA NA

WR Pirana 1.60 0.88 1.17

WR Dehgam 1.02 0.16 0.13

WR Itarasi 1.01 0.15 0.12

WR Damoh 0.88 0.11 0.22

WR Indore 0.75 0.12 0.13

5.11 Power Quality Measurement of various household appliances

To understand the contribution of consumer appliances in the prevailing electrical pollution

observed in the grid i.e. Power Quality parameters were measured for various commonly used

household & office use appliances. It can be observed that most of the commonly used

Information Technology (IT) related appliances, such as Laptop, Mobile charger, Desktop and

other household appliances like LED light, micro wave oven, etc. draw discontinuous current

from the supply only for a fraction of each half cycle. Voltage and Current wave form of a

typical such appliance is shown in Figure 5-92.

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Figure 5-92: Typical Voltage and current wave form of a non-linear single phase appliance

and harmonic content of the current drawn.

The main source of such type of harmonic current are at present the phase angle controlled

rectifiers and inverters, often called static power converters. These converters take AC power

and convert it to another form, sometimes back to AC power at the same or different frequency,

based on the firing scheme. The firing scheme refers to the controlling mechanism that

determines how and when current conducted. One major variation is the phase angle at which

conduction begins and ends. A typical such converter is the switching type power supplies

found in most the commonly used Information Technology (IT) related appliances, such as

Laptop, Mobile charger, Desktop and other household appliances like LED light, micro wave

oven, etc. Despite causing power quality problems, the use of non-linear loads, especially those

employing solid-state controllers, is increasing day by day owing to benefits of the low cost

and small size, remarkable energy conservation, simplicity in control, reduced wear and tear,

and low maintenance requirements in the new and automated electric appliances, leading to

high productivity. Although these electronically automated energy efficient loads are most

sensitive to the power quality problems, they themselves cause power quality problems to the

supply system.

On the other hand conventional household appliances like Fan with resistive regulator,

refrigerator (old, non-inverter type), incandescent lamps etc. draw continuous sinusoidal

waveform with very little distortion. Voltage and current wave form of a typical such appliance

is shown in Figure 5-93.

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Figure 5-93: Typical Voltage and current wave form of a linear single phase appliance and

harmonic content of the current drawn

Summary of these measurements are as given in Table 5-2 and associated voltage & current

waveforms, Phasor diagram, harmonics etc. are elaborately given in Exhibit-A.

5.12 Broad Observation

Power quality measurement in 175 cities/towns at various voltage levels indicate the

presence of high content of voltage harmonics at 65 cities/towns, for a duration ranging up to

4% of time. Transmission system voltages and current were found to be rich in 5th & 7th

harmonics. Whereas LT level was found to have high content of 3rd harmonics.

Table 5-13: Overview of Power Quality Parameters observed across the country

Sl No.

Power Quality Parameters

Northern Region

Southern Region

Western Region

Eastern Region

North Eastern Region

No. Of Locations Exceeding Permissible Limits

1 Voltage Sag 29 7 12 13 12 73

2 Voltage Harmonic 17 18 18 12 0 65

3 Unbalance 27 14 16 9 13 79

4 Current Harmonics 11 6 10 11 0 38

4 Voltage Swell 4 2 4 1 0 11

5 DC offset 4 3 2 1 0 10

6 Interruptions 0 3 3 2 0 8

Voltage unbalance exceeding permissible limit (for short durations) were observed at

79 cities/towns during the field measurement. Many instances of voltage sag/dip were also

observed in the transmission network. Higher value of Flicker that gives an impression of

instability in the visual sensation were observed mainly in the LT supply almost all the

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cities/town across the country. Flicker observed in the transmission system at 400 kV & 765kV

level was of very low magnitude.

An overview of power quality parameters observed across different regions of the

country is shown in Table 5-13 & Figure 5-94, which indicates that critical Power Quality

Parameters are voltage sag, harmonics, voltage unbalance apart from flicker and power factor.

On the other hand, at end consumers’ level, Power quality parameters measured on

commonly used appliances used in the offices and homes show their non-linear nature, which

in turn reflects in the form of high content of current harmonics. It has been observed that these

appliances draw current rich in odd harmonics such as 3rd, 5th, 7th, and so on in the diminishing

order of magnitude. Further, high content of harmonics were also observed in the

current/voltage of the supply feeder of offices and apartments (at 415V) along with large values

of neutral current. Other Power Quality events like, Voltage Sag/Swell, Unbalance, flicker etc.

were also observed at the point of common coupling in the LT supply.

Figure 5-94: Region-wise Power Quality Parameters observed across the country

Figure 5-94 shows the status of various power quality parameters in different regions.

The critical power quality parameters in the various regions are as listed in Table 5-14 below:

Table 5-14: Summary of Critical Power Quality Parameters

Sl. No. Region Name Critical Power Quality Parameter

1 Northern Sag, Voltage Unbalance

2 Western Harmonics

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3 Southern Harmonics

4 Eastern Sag, Harmonics

5 North Eastern Voltage Unbalance, Sag

CEA has defined power quality standards for Harmonics, Unbalance and Voltage

limits. Therefore, these three parameters out of the various power quality parameters measured,

have been considered to classify power quality in various states of India. Power quality levels

have been analyzed for above parameters by considering equal weightage for each parameter

and based on the results, states have been classified into two categories; critical and non-critical

as shown in the Power Quality map in Figure 5-95. States where monitored power quality

parameters exceeded the limits, have been marked as critical areas, whereas states with less

severity have been marked as non-critical as shown in Table 5-15.

Table 5-15: State wise Power Quality Severity Level


1 Himachal Pradesh 0.667 Critical

2 J&K 0.667 Critical

3 Maharashtra 0.619 Critical

4 Punjab 0.611 Critical

5 Assam 0.611 Critical

6 Gujarat 0.571 Critical

7 Chhattisgarh 0.556 Critical

8 Orissa 0.542 Critical

9 Telangana 0.500 Critical

10 New Delhi 0.500 Critical

11 Haryana 0.485 Non-Critical

12 Uttar Pradesh 0.422 Non-Critical

13 Bihar 0.407 Non-Critical

14 West Bengal 0.370 Non-Critical

15 Rajasthan 0.370 Non-Critical

16 Madhya Pradesh 0.361 Non-Critical

17 Tamil Nadu 0.333 Non-Critical

18 Goa 0.333 Non-Critical

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19 Mizoram 0.333 Non-Critical

20 Nagaland 0.333 Non-Critical

21 Manipur 0.333 Non-Critical

22 Meghalaya 0.333 Non-Critical

23 Tripura 0.333 Non-Critical

24 Uttrakhand 0.333 Non-Critical

25 Andhra Pradesh 0.333 Non-Critical

26 Arunachal Pradesh 0.333 Non-Critical

27 Karnataka 0.278 Non-Critical

28 Kerala 0.250 Non-Critical

29 Jharkhand 0.083 Non-Critical

30 Sikkim 0.000 Non-Critical

Note:

Power Quality Severity Index: Number of Power Quality Parameters exceeding the limits at

different voltage level at a location, normalized over total number of power quality parameters

measured and then, averaging all normalized measurements across the state. For Example, the

calculation of Power Quality Severity Index for Gujarat is shown below:

Table 5-16: Power Quality Severity Index calculation

Location Voltage Level Voltage Sag Voltage Harmonic Unbalance Average Ranking

Bachau 400/220 0 1 1 0.67

Dehgam 400/220 0 1 1 0.67

Kala 400/220 1 1 0 0.67

Magarwada 400/220 0 1 0 0.33

Navasari 400/220 0 1 0 0.33

Pirana 400/220 1 1 1 1

Vapi 400/220 0 1 0 0.33

Power Quality Severity Index= 𝑠𝑢𝑚 𝑜𝑓 𝑟𝑎𝑡𝑖𝑛𝑔𝑠 𝑓𝑜𝑟 𝑖𝑛𝑑𝑖𝑣𝑖𝑑𝑢𝑎𝑙 𝑙𝑜𝑐𝑎𝑡𝑖𝑜𝑛𝑠

𝑁𝑜.𝑜𝑓 𝑙𝑜𝑐𝑎𝑡𝑖𝑜𝑛𝑠

=0.67+0.67+0.67+0.33+0.33+1+0.33

7

=0.571

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Here each location has been given one point against each parameter of Power Quality if the

parameter is found to be exceeding limits/standards. Thereafter, average is calculated for each

location. The overall average of rankings for all the locations in a given state is considered to

be the ‘Power Quality Severity Index’ for that state.

Figure 5-95 : Power Quality Map of India

***

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Chapter-6

6 Solutions for Power Quality

Problems 6.1 Mitigation of Power Quality Problems

A number of techniques have evolved for mitigation of Power Quality problems either

in the existing systems or in equipment to be developed in the near future. The techniques

employed for power quality improvements in existing system facing power quality problems

are classified in a different manner from those used in newly designed and developed

equipment. These mitigation techniques are further sub-classified for the electrical loads and

supply system, since both of them have somewhat different kind of power quality problems.

In existing nonlinear loads, having the power quality problem of poor power factor,

harmonic currents, unbalanced currents, and an excessive neutral current, a series of power

filters of various types such as passive, active, and hybrid in shunt, series, or a combination of

both configurations are used externally depending upon the nature of loads such as voltage-fed

loads, current-fed loads, or a combination of both to mitigate PQ problems.

Power Quality Issues has resulted in a new direction of research and development

(R&D) activities for the design and development engineers working in the field of power

electronics, power systems, electric drives, digital signal processing, and sensors. It has

changed the scenario of power electronics as most of the equipment using power converters at

the front end need modification in view of these newly visualized requirements. Moreover,

some of the well-developed converters are becoming obsolete and better substitutes are

required.

A brief description of mitigating measures for various types of power quality problems are

discussed in following section.

6.1.1 Power Factor Improvement

Power factor may be improved by compensating reactive power requirement at the load. If

power factor is lagging then compensation is done in the form of capacitive reactive power by

installing capacitors banks, minimizing operation of lightly loaded induction motors, avoiding

operation of equipment above their rated voltage etc. Whereas leading power factor situations

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are taken care by installation of reactors, avoidance of operation of lightly loaded long lines

etc. Proper compensation allows reactive power in opposite direction of the existing reactive

power flow / demand and neutralizes it resulting into improved power factor. Figure 6-1shows

effect of power factor improvement. Due to absorption (compensation), reactive power

requirement is reduced, whereas active power demand is not affected, resulting into less

apparent power demand and improved power factor.

Figure 6-1: Power factor improvement

Loss reduction in the system due to improved power factor is shown below:

% 𝑙𝑜𝑠𝑠 𝑟𝑒𝑑𝑢𝑐𝑡𝑖𝑜𝑛 = 100 [1 − (𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑝𝑓

𝑖𝑚𝑝𝑟𝑜𝑣𝑒𝑑 𝑝𝑓)2]

If the power factor of a facility is known (PFold) and an improved power factor is targeted

(PFnew), the reactive power required by installation of capacitors (kVARcap) is calculated as

below:

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6.1.2 Mitigation of Voltage Sag / Swell

Modifications in the process equipment itself are the cheapest solution to mitigate voltage

sag/swell. Modifying the grid for immunization for voltage sag/swell is also an option but is

expensive. Voltage sag/swell may be mitigated by providing sources / devices in the power

system which shall be capable of providing stability in system through higher current /

maintaining voltage. Protective devices installed between the sensitive process and the grid,

are other solutions which include energy storage devices, dynamic voltage regulators / dynamic

voltage restorars, superconducting energy storage devices, flywheels, UPS, STATCOM,

ferroresonant, i.e., constant voltage transformers etc.

6.1.3 Mitigation of Over / Under Voltage Conditions

Over / under voltage may be mitigated by using shunt capacitors, shunt reactors, SVC,

STATCOM etc., which provide compensating reactive power in the system to maintain

voltage. Correctly setting the transformer taps also helps in controlling the over/under voltage

conditions. In the power system network under-voltages can be prevented by adding more

generation and transmission lines.

6.1.4 Reduction of Voltage Interruptions

Many of the causes of interruptions like faults can be mitigated by monitoring &

maintaining the power system stable so that probability of occurrence of faults is reduced. An

end user may install energy storage system, UPS etc. to prevent interruptions by providing

emergency power supply while a utility may provide an off-site source that includes two

feeders with a high speed switch that switches to the alternate feeder when one feeder fails.

6.1.5 Mitigation of Transients

To control transients, transient voltage surge suppressors (TVSS) are used. These are non-

linear resistances, which offer low resistance at voltages higher than threshold limit and

transient is directed to the ground. Surge arrestor, voltage stabilizers, voltage regulators etc. are

used for transient control.

6.1.6 Remedy for Voltage Notching

Solution for voltage notching typically involves isolation of the critical and sensitive

equipment from the source (i.e. rectifiers) of voltage notching. Other methods for reducing

notches includes provision of impedance reactor in series with source of notches, which results

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into distribution of notch voltage across the new impedance (reactance) and the pre-existing

line to source impedance.

6.1.7 Mitigation of Voltage Fluctuation and Flicker

The effects of voltage fluctuations depend on their amplitude / rate of occurrence, which

are influenced by the characteristics of the power system and type of load &its operation.

Therefore mitigation measures are targeted at actions focused on limiting the amplitude of the

voltage fluctuations. Voltage fluctuation and flicker may be reduced by:

Increasing the short circuit power (with respect to the load power) at the point of

coupling to which a fluctuating load is connected. It is done by connecting the load at

a higher nominal voltage level, supplying this category of loads from dedicated lines,

separating supplies for fluctuating loads from steady loads by using separate windings

of a three-winding transformer, increasing the rated power of the transformer supplying

the fluctuating load and installing series capacitors.

Reducing the changes of reactive power in the supply system by installing dynamic

compensators.

Dynamic voltage regulators, synchronous machines, STATCOM etc. are the devices which can

be installed in the power system to control voltage fluctuations and flicker.

6.1.8 Mitigation of Harmonic / Inter Harmonic Distortions

Harmonics may be removed from the system in two ways; Passive and Active

arrangements. In passive techniques, the undesirable harmonic currents are prevented from

flowing into the system by either installing a high series impedance to block their flow or

diverting the flow of harmonic currents by means of a low-impedance parallel path. Passive

techniques are series line reactors, tuned harmonic filters, series induction filters, parallel /

series connected resonant filters, neutral current filter, zigzag grounding filter and the use of

higher pulse number converter circuits such as 12-pulse, 18-pulse, 24-pulse rectifiers etc.

Principle of passive harmonic filter is shown in Figure 6-2, where pre-identified harmonic

current for which filter is designed is absorbed by the passive harmonic filter.

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Figure 6-2: Principle of passive harmonic filters

Active methods inject equal-but-opposite current or voltage distortion into the network,

thereby canceling the original distortion. Active methods use parallel / series / hybrid active

filters for mitigation of harmonics[1]. Figure 6-3 shows principle for operation of active

harmonic filter, where equal-but-opposite harmonic currents injected by active filter neutralizes

effect of harmonic current and resultant current is made clean.

Presence of 3rd harmonic in variable frequency drive

installation operating at 10% efficiency can cause the

temperature of the motor to rise by 6° C.

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Figure 6-3: Principle of active harmonic filters

6.2 Planning for mitigation of Power Quality Issues

Comprehensive knowledge of power quality issues is important in today’s electrical

power system operating environment with ultimate purpose to solve power quality problems.

To address the issue surveys and mapping of consumer sites, different voltage levels for PQ

parameters are required to be done meticulously so that designing & installation of mitigating

devices can be carried out. Similarly base-line data is required for the regulatory / statutory

bodies to formulate standards, incentives and penalties to ensure a healthy grid with acceptable

quality of power.

Information regarding the amount of disturbances in the supply system is needed to

estimate the losses being incurred and hence carrying out the cost-benefit analysis for the

installation of mitigation equipment/ solutions. From utility perspective, PQ measurement

helps in identification of faulty equipment or consumers affecting the system. Thus

rectifications can be made to abide by the norms or standards of power quality in the respective

systems.

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Figure 6-4: Cost of power quality solution

Solving power quality problems depends on acquiring meaningful data at the optimum

location(s) and within an expedient time frame, which are then analyzed to obtain a solution to

the problem. Power quality problems do not have a single solution but a combination of

solutions to obtain the desired results. As shown in Figure 6-4, usually a power quality solution

may be implemented at equipment level, control & protection level, feeder or group level and

utility source level depending upon causes of quality issue. Cost of the solution increases as we

go from equipment level to utility source level.

Figure 6-5: Basic steps involved in power quality problem evaluation. (Courtesy of EPRI.)

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Prevention of problem is always better than cure. Therefore, designing equipment and

electrical systems carefully to prevent generation of power quality problems is the best way to

maintain power quality.

If power quality problem exist in the system, it can be solved in five steps (refer Figure 6-5) as

highlighted below:

1. Identify the category of problem. Categories may be defined based on symptoms, damages

or severity of the problems.

2. Carry out measurements and data collection at suitable locations to characterize problem,

its causes and impacts. Accurate data and measurements shall be key for identification of

exact problem.

3. Identify range of solutions for mitigation of power quality problem identified. No single

solution is applicable for power quality issues. Multi solutions help to select appropriate

one particular case.

4. Evaluate identified solutions for technical and economic benefits. Different solutions have

their own merits & demerits, which should be compared and evaluated.

5. Finalize and implement optimum solution.

Power quality problems exist in every part of the power supply chain and therefore

solutions are also deployed across the chain. Mitigation methods vary in different segments of

transmission, distribution and at the end-use equipment as shown in Figure 6-6.

Figure 6-6: Solutions for power quality problem

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6.3 Enhanced Interface Devices

Using proper interface devices, power quality issues at the load end may be minimized.

Solutions are generally defined in two (2) categories; corrective solutions and preventive

solutions.

Corrective solutions are the techniques to overcome the existing problems. Use of active

and passive filters and reconfiguration of the feeders or reallocation of capacitor banks etc. are

some examples. Whereas Preventive solutions aim to avoid power quality issues from the

installation of the equipment itself. Proper design of the equipment and control system protect

the equipment from power quality problems and also eliminate disturbance generated within

the equipment.

Some of the devices have been described below:

6.3.1 Series Capacitor

Series Capacitors are generally applied to compensate the inductance of long transmission

lines, in order to reduce the line voltage drop, improve its voltage regulation, minimize losses

by optimizing load distribution between parallel transmission lines, and to increase the power

transfer capability. Series capacitors are also installed in electrical power systems to improve

its voltage stability.

Series capacitors positively affect the voltage and reactive power balance. When the load

current passes through the capacitor, the voltage drop over the capacitor varies in proportion to

the current. The voltage drop is capacitive, such that it offsets the inductive voltage drop, which

also varies with the load current. The result is an automatic stabilizing effect on the voltage in

the network. Figure 6-7 shows voltage rise due to series capacitors.

Figure 6-7: Voltage rise due to series capacitors

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Series capacitors generate capacitive power, which improves the system power factor

resulting in reduced line current, reduced line losses and the increase of load capacity.

6.3.2 Shunt Capacitors

Shunt capacitors are usually called “power factor correction capacitors”. Shunt capacitors

are used either at the customer location for power factor correction or on the distribution system

for voltage control. Utilities use shunt capacitors at distribution and utilization levels to provide

reactive power near the inductive loads that require it. This reduces the total current flowing

on the distribution feeder, which improves the voltage profile along the feeder, release

additional feeder capacity, and reduces losses. In fact, substation transformers experience lower

loadings when utilities install sufficient capacitors on the distribution system. The reduced

loadings not only improve contingency switching options on the distribution system, but also

extend equipment life and defer expensive additions to the system.

At the transmission and sub-transmission levels (66 kV and above), shunt capacitors

increase the power transfer capability of a transmission system without requiring new lines or

larger conductors. Shunt capacitors also increase transmission bus operating voltages. As the

transmission voltage increases, less current is necessary to supply a typical load, so

transmission losses decreases.

6.3.3 Static Var Compensator (SVC)

Static Var Compensator (SVC) provides fast reactive power compensation in power system

using combination of capacitors and reactors to regulate the voltage. These are primarily used

to mitigate voltage fluctuation, as well as the resulting flicker. In addition, these are installed

at suitable points in the electric power system to augment its transfer capability by improving

voltage stability, while keeping a smooth voltage profile under different system conditions.

SVCs can also mitigate active power oscillations through voltage amplitude modulation.

Moreover, as an automated impedance matching device, they have the added benefit of

bringing the system power factor close to unity. Therefore, SVC is usually installed near high

and rapidly varying loads, such as electric arc furnaces, welding plants and other industries

prone to voltage fluctuations and flicker. Figure 6-8 and Figure 6-9 shows an installation of

SVC and effect of SVC on voltage respectively.

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Figure 6-8: Static Var Compensator (SVC)

Figure 6-9: Effect of Static Var Compensation

SVCs are basically of two types as described below:

6.3.3.1 Thyristor-controlled Reactors with Fixed Capacitors (TCRFC)

This SVC design consists of two parallel branches connected on the secondary side of a

coupling transformer. One of the branches is composed of reactors that are controlled by AC

thyristor switches. The other branch could either be fixed capacitor banks or shunt filters. The

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variation of reactive power is accomplished by controlling the thyristor’s firing instants and,

accordingly, the current that flows by the reactance. A schematic diagram of TCRFC is shown

in Figure 6-10.

Figure 6-10: Thyrsitor-controlled Reactors with Fixed Capacitors (or Shunt Filters)

6.3.3.2 Thyristor switched capacitors (TSC)

In this static var compensator design, the capacitor banks are connected phase-to-phase,

with each section switched by thyristors. By providing a suitably large number of small

sections, the required resolution of reactive power variation for a single step is achieved. Figure

6-11 shows a schematic diagram for TSC.

Figure 6-11: Thyristor-switched Capacitors (TSC)

6.3.4 STATCOM

STATCOM or Static Synchronous Compensator is a shunt device, which uses force-

commutated power electronics (i.e. GTO, IGBT) to control power flow and improve transient

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stability on electrical power networks. It is also a member of the so-called Flexible AC

Transmission System (FACTS) devices. The STATCOM basically performs the same function

as the Static Var Compensators but with some advantages.

Figure 6-12: STATCOM (Static Synchronous Compensator)

The term Static Synchronous Compensator is derived from its capabilities and operating

principle, which are similar to those of rotating synchronous compensators (i.e. generators),

but with relatively faster operation. Figure 6-12 shows an installation of STATCOM. A

STATCOM is composed of the following components:

i. Voltage-Source Converter (VSC): The voltage-source converter transforms the

DC input voltage to an AC output voltage. Two of the most common VSC types

are described below. Square-wave Inverters using Gate Turn-Off Thyristors:

Generally, four, three-level inverters are utilized to make a 48-step voltage

waveform. Subsequently, it controls reactive power flow by changing the DC

capacitor input voltage, as fundamental component of the converter output

voltage is proportional to the DC voltage.

ii. PWM Inverters using Insulated Gate Bipolar Transistors (IGBT): It uses

Pulse-Width Modulation (PWM) technique to create a sinusoidal waveform from

a DC voltage source with a typical chopping frequency of a few kHz. In contrast

to the GTO-based type, the IGBT-based VSC utilizes a fixed DC voltage and

varies its output AC voltage by changing the modulation index of the PWM

modulator.

A. DC Capacitor: This component provides the DC voltage for the inverter.

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B. Inductive Reactance (X): It connects the inverter output to the power system. This is

usually the leakage inductance of a coupling transformer.

C. Harmonic Filters: Mitigate harmonics and other high frequency components due to the

inverters.

STATCOM works of the principle that when two AC sources having same frequency and

connected through a series reactance, active or real power flows from the leading source to the

lagging source and reactive power flows from the higher to the lower voltage magnitude source.

STATCOM regulate the reactive power flow by changing the output voltage of the voltage-

source converter with respect to the system voltage. It operates in two modes:

i. Voltage Regulation: In this mode, STATCOM regulates voltage at its connection point

by controlling the amount of reactive power that is absorbed from or injected into the

power system through a voltage-source converter.

ii. Var Control: In this mode, the STATCOM reactive power output is kept constant

independent of other system parameter. Figure 6-13 shows V-I characteristics of

STATCOM. For the control of reactive power output of STATCOM the voltage

magnitude of the inverter output is controlled by taking the grid voltage (Vref) as

reference. When STATCOM voltage is kept in phase with the grid voltage and

magnitude of voltage is increased such that V>Vref, then inductive power is injected

into the grid. Similarly for V<Vref, capacitive power is provided by the STATCOM.

Figure 6-13: V-I characteristics of STATCOM

STATCOMs are typically applied in long distance transmission systems, power substations

and heavy industries where voltage stability is the primary concern. In addition, static

synchronous compensators are installed in select points in the power system to perform the

following:

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Voltage support and control

Voltage fluctuation and flicker mitigation

Unsymmetrical load balancing

Power factor correction

Active harmonics cancellation

Improve transient stability of the power system

6.3.5 D-STATCOM

A DSTATCOM (Distribution Static Compensators) is a fast-response, solid-state power

controller that provides power quality improvements at the point of connection to the utility

distribution feeder. It is the most important power quality controller for the distribution

networks. It has been widely used for precisely regulate the system voltage and /or for load

compensation. It can exchange both active and reactive power with the distribution system by

varying the amplitude and phase angle of the voltage of the VSC (Voltage Source Converter)

with respect to the PCC voltage, if an energy storage system is included into the DC bus.

However, a capacitor supported DSTATCOM is preferred for power quality improvement in

the currents, such as reactive power compensation for unity power factor or voltage regulation

at PCC, load balancing and neutral current compensation. These compensating devices are also

used to regulate the terminal voltage, suppress voltage flicker, and improve voltage balance in

three phase systems. One of the major factors in advancing the DSTATCOM technology is the

advent of fast, self-commutating solid-state devices.

Figure 6-14: D-STATCOM schematic representation

With the introduction of IGBT (insulated gate bipolar transistor), the DSTATCOM

technology has got a real boost. DSTATCOM is connected in parallel with transmission lines.

DSTATCOM can provide cost effective solution for the compensation of reactive power and

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unbalance loading in distribution system. A Schematic representation of D-STATCOM is

given in Figure 6-14.

6.3.6 Dynamic Voltage Restorer (DVR)

To mitigate the voltage based power quality problems such as spikes, surges, flickers,

sags, swells, notches, fluctuations, voltage imbalance, waveform distortion, etc. in the

distribution system solid-state series compensators (SSC) and dynamic voltage restorer are

commonly used. These active series compensators are recently reported with some

modifications as cost-effective filters with series active power filters to eliminate harmonic

currents in voltage-fed nonlinear loads and with shunt passive filters to eliminate harmonic

currents in current fed non-linear loads. These compensators are based on the principle of

injecting a voltage in series with the supply. This compensator inserts a voltage of required

waveform so that it can protect the sensitive consumer loads from supply disturbances such as

sag, swell, spikes, notches, unbalance, harmonics, and so on in supply voltage. It is one of the

most effective PQ devices in solving voltage sag problems. The basic principle of the dynamic

voltage restorer is to inject a voltage of required magnitude and frequency, so that it can restore

the load side voltage to the desired amplitude and waveform even when the source voltage is

unbalanced or distorted. DVR can generate or absorb independently controllable real and

reactive power at the load side. In other words, the DVR is made of a solid state DC to AC

switching power converter that injects a set of three phase AC output voltages in series and

synchronism with the distribution and transmission line voltages. Figure 6-15 shows schematic

diagram for DVR.

Figure 6-15: Dynamic voltage restorer (DVR) schematic diagram

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6.3.7 Unified Power Quality Conditioner (UPQC)

The unified power quality conditioner (UPQC) is a custom power device, which mitigates

voltage and current-related PQ issues in the power distribution systems. A UPQC, which is a

combination of shunt and series compensators, is proposed as a single solution for mitigating

multiple power quality problems.

Figure 6-16: Typical Hardware structure of UPQC

The power circuit of a UPQC consists of two VSCs connected back to back by a common

DC link. The shunt devices known as DSTATCOM provides reactive power compensation

along with load balancing, neutral current compensation, and elimination of harmonics (if

required) and is positioned parallel to consumer load. The series device known as DVR keeps

the load end voltage insensitive to supply voltage quality problems such as voltage sag/swell,

surge spikes, notches, or unbalance. The DVR injects a compensating voltage between the

supply and the consumer load, and restores the load voltage to its reference value. Figure 6-16

shows schematic diagram for UPQC.

6.3.8 Harmonic Filters

Harmonic Filters are used to mitigate the power quality problem known as harmonic

waveform distortion. Consequently, they minimize the thermal and electrical stress on the

electrical infrastructure, eliminate the risk of harmonics-related reliability issues and allow for

long-term energy efficiency and cost savings. Harmonic filters are classified as following:

a) Passive Harmonic filters: Passive harmonic filters provide low impedance path to the

harmonic frequencies to be attenuated using passive components (inductors, capacitors

and resistors). It absorbs the harmonic current to which it is tuned and filters it out of

the system.

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b) Active harmonic filters: Active Harmonic Filters (AHF) monitor the non-linear load

and dynamically provide controlled current injection, which cancels out the harmonic

currents in the electrical system. They also correct poor displacement power

factor (DPF) by compensating the system’s reactive current.

c) Hybrid harmonic filter: It is combination of both passive & active harmonic filters.

A harmonic filter provides the following benefits and performs these functions:

Supplies connected loads with non-destructive current and voltage waveforms.

Increases equipment capacity by reducing losses caused by harmonics on lines and

transformers.

Reduces triplen harmonics, which increase the current flowing through the neutral.

Protects the electrical system by reducing overheating of equipment and/or fire hazards.

Improves phase current and voltage balance.

Improves the power factor of non-linear loads.

Harmonic Filters are appropriate for electrical power distribution systems that supply

significant amount of harmonic-producing loads. Some of the places where harmonic filters

are deployed are as below:

Industrial - Adjustable Speed Drives, Arc Furnaces, Arc Welders and HVAC

Commercial - SMPS, Medical Devices ,UPS Systems and Data Centers

Residential – Computer equipment, electronic devices and other appliances.

6.3.9 K-Factor Transformer

“K-Factor” (K-rated) Transformer is designed for non-linear or harmonic generating loads

that a standard transformer could not adequately handle due to overheating. K-factor

transformers are specially assembled with a double sized neutral conductor, heavier gauge

copper and either change the geometry of their conductors or use multiple conductors for the

coils. These properties allow them to endure the additional heat caused by harmonic currents

much better than a standard transformer.

A K-factor transformer has certain features that allow it to handle the extra heating of

harmonic currents. It may have a static shield between the high and low voltage windings to

reduce electrostatic noise caused by harmonics. It may use smaller than normal, transposed,

and individually insulated conductors to reduce the skin-effect and eddy-current losses. It may

also have a neutral conductor in the secondary winding large enough to carry the third harmonic

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neutral currents. It may also have a neutral conductor in the secondary winding large enough

to carry the third-harmonic neutral currents. It may have core laminations that are individually

insulated to reduce eddy currents in the core. It may have a larger core with special steel to

reduce hysteresis losses and reduce the possibility of the transformer saturating because of high

voltage peaks on the distorted bus voltage waveform. This special steel has less resistance to

the changing magnetic fields. A larger core increases the area of steel and thus reduces the flux

density and resistance to the changing magnetic fields. The K-factor transformers flux density

can also be reduced by increasing the no. of turns in the winding. These transformers may have

larger conductors than a standard transformer with the same name plate rating to reduce eddy-

current losses and decrease the flux density.

Note: A K-factor transformer may cost approximately twice as much as a standard

transformer and weigh 115 percent more than a standard transformer. It is recommended that

purchasers of transformers use K-factor transformers rather than derate a standard transformer.

This is to avoid unforeseen hotspots. A derated transformer may still contain hot spots due to

harmonics that could result in overheating and transformer loss of life. Harmonics not only

cause transformers and other equipment to overheat but also can cause cables to overheat as

well. The neutral conductor in the cable is especially susceptible to overloading due to

harmonics.

6.3.10 Transient Voltage Surge suppressors (TVSS)

TVSS devices are used to protect other equipment from dangers of potentially harmful

voltage surges caused by lightning and switching of inductive or capacitive devices. Transient

voltage surge suppressors are used as interface between the power source and sensitive loads,

so that the transient voltage is clamped by the TVSS before it reaches the load. TVSSs usually

contain a component with a non-linear resistance (a metal oxide varistor or a zener diode) that

limits excessive line voltage and conduct any excess impulse energy to ground.

6.3.11 Isolation transformer

Isolation Transformer is a special type of transformer, wherein the primary and secondary

windings are physically separated through double insulation. The leakage inductance of

isolation transformers is the primary feature that electrically isolates people and equipment

from the hazards of power quality problems such as transients and high-frequency noise. In

addition, isolation transformers can prevent transfer of DC signals from one circuit to the other,

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as well as block interference due to ground loops. However, they permit AC power or signals

to pass. Figure 6-17 shows a schematic view of isolation transformer.

Figure 6-17: Isolation transformer

Benefits of an isolation transformer are:

Capacitor-switching and lightning transients can be attenuated, thus preventing

nuisance tripping of adjustable-speed drives and other equipment.

Improve power quality by reducing high-frequency noise currents.

Complete isolation from the input AC line.

Combined with surge protective devices, it offers continuous filtering of power line

noise in all modes.

Active transformer filtering provides common-mode noise rejection with no wearable

parts, exceptionally reducing surges in the worst of power environments to harmless

levels.

Limit voltage notching due to power electronic switching.

6.4 Make End-use Devices Less Sensitive

Another way to deal with power quality problems is to have equipment & devices which

are less sensitive to power quality issues and provide stable performance in large range of

electrical parameters. Designing the equipment to be less sensitive to disturbances is usually

the most cost effective measure to prevent PQ problems. Some end-use equipment

manufacturers are now recognizing this problem. Adding a capacitor with a larger capacity to

power supplies, using cables with larger neutral conductors, derating transformers and

adjusting under voltage relays, are measures that could be taken by manufacturers to reduce

the sensitivity of equipment to PQ problems.

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Both producers and consumers should feel “Power Quality” seriously. Every possible effort

should be tried to solve the problems by all individuals. Basically the distribution companies

should enhance the load end distribution networks and its designs to solve the possible

problems. To avoid the huge losses related to PQ problems, the most demanding consumers

must take action to prevent problems. Among the various measures, selection of less sensitive

equipment can play an important role. When the most robust equipment is affected, then other

measures must be taken, such as installation of restoring technologies, distributed generation

or an interface device to prevent PQ problems.

To summarize interface devices available for power quality mitigation Table 6-1, shows

use of different equipment for mitigation of common power quality problems.

Table 6-1: Summary of power quality problem and solutions

Example wave

shape or R.M.S.

variation

Causes Sources Effects Examples of

Power

conditioning

solutions

Impulsive

transients

(Transient

disturbance)

- Lightning

-Electrostatic

discharge

-Load

switching

-Capacitor

switching

-Destroys

computer

chips and TV

regulators

-Surge arresters

- Filters

- Isolation

transformers

-TVSS

-CVT

Oscillatory

transients

(Transient

disturbance)

-Line/cable

switching

-Capacitor

switching

-Load

switching

-Destroys

computer

chips and TV

regulators

-Surge arresters

- Filters

-Isolation

transformers

-TVSS

-CVT

Sags/swells

(RMS

disturbance)

-Remote

system

faults

-Motors

stalling and

overheating

-Computer

failures

-ASDs shutting

down

-Dynamic

voltage

restorer(DVR)

-Energy storage

technologies

- UPS

Interruptions

(RMS

disturbance)

-System

protection

- Breakers

- Fuses

- Maintenance

-Loss

production

-Shutting down

of

Equipment

-Energy storage

technologies

- UPS

- Backup

Generators

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Example wave

shape or R.M.S.

variation

Causes Sources Effects Examples of

Power

conditioning

solutions

Under

voltages/

Over voltages

(steady-state

variation)

- Motor starting

-Load

variations

-Load dropping

-Shorten lives

of motors and

lightning

filaments

-Voltage

regulators

-constant

voltage

transformer

Harmonic

distortion

(steady-state

variation)

Non-linear

loads

-System

resonance

- Overheating

transformers

and motors

- Fuses blow

- Relays trip

-Meters

malfunction

-Active or

passive filters

-K factor

Transformers

Voltage flicker

(steady-state

variation)

-Intermittent

loads

- Motor starting

- Arc furnaces

- Lights flicker

- Irritation

-Static VAR

Systems

- STATCOM

Voltage

unbalance

-Large and/or

unequal single

phase loads

-Blown fuses

on capacitor

banks;

-Unequal

impedances of

the 3ph

transmission

and distribution

lines.

-Increased

motor losses

and running

costs, reduced

efficiency.

- heating and

loss of motor

insulation life;

-Effective

torque and

speed will be

reduced

-Dynamic

voltage

restorer(DVR)

-STATCOM

-SVC

----x---

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Chapter-7

7 Investments for Power Quality 7.1 Estimated Investments required in next 5 years

An estimate of investments required to improve the Quality of Power Supply by installing

Power-Quality interface devices in the distribution network, is proposed in the following

section. As mentioned in section 5.12, ten (10) different states (shown in Table 7-1) have been

identified as critical with respect to Power Quality in India. The total connected load across

different categories of consumers in these states is shown in Table 7-1. Assuming that all these

loads are not equally sensitive to Power Quality issues; hence, considering a certain proportion

of loads, as shown in Table 7-2, being relatively more sensitive to Power Quality; deployment

of mitigating measures can be planned in phased manner for these loads. Initially, 50% of

connected loads in Industrial, Commercial & Domestic domains may be selected for Power

Quality mitigating measures.

Table 7-1: State-Wise connected loads identified for Power Quality Improvement*

State Industrial Load

(GW) Domestic Load

(GW) Commercial Load

(GW) Total (GW)

Himachal Pradesh 1.79 2.63 0.56 4.98

Jammu & Kashmir 0.58 1.06 0.24 1.88

Punjab 7.73 10.14 3.13 21.00

Delhi 1.91 10.68 7.41 20.00

Gujarat 13.55 12.09 5.29 30.93

Chhattisgarh 2.27 1.63 0.94 4.85

Maharashtra 23.81 25.30 10.46 59.56

Andhra Pradesh 34.95 36.26 12.50 83.71

Odisha 2.61 4.37 0.82 7.80

Assam 0.99 2.14 0.53 3.65

Total 90.2 106.3 41.8 238.3

Table 7-2: Total connected load identified for Power Quality Improvement*

(*Source: CEA Report) Note: All the investments calculated hereafter are based on the above segregation

Type of Load Various Types of

Connected

Load* (GW)

Proportion assumed to

be sensitive towards

Power Quality

Quantum of connected

Load considered for PQ

improvement

Industrial 90.2 50% 45 GW

Domestic 106.3 50% 53 GW

Commercial 41.8 50% 20 GW

Total 238.3 GW 118 GW

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Studies show that sags and interruptions are the most significant events from economical

point of view in industries. Its mitigation requires strengthening of distribution system network,

besides deployment of power quality improvement devices as described above. System

strengthening will not only help in improving Power Quality parameters but it will also help in

ensuring reliable supply. Based on one of the studies, is has been observed that the average

interruption duration is of the order of few hours per week & average interruption frequency is

of the order of few hundreds per year. Therefore, strengthening the distribution network will

go a long way in improving Power Quality parameters such as interruption, voltage sag,

outages etc.

However, installing Power-Quality interface devices at the load ends has been proposed in

the following sections, because it is most economical to mitigate the VAR compensation,

Harmonic mitigation & Unbalance correction at the load end instead of the far-off Grid points.

Power Quality interface devices as described in previous chapters can be broadly classified

under following two major categories:

1. Voltage sag & Interruption protection devices such as dynamic Voltage Restorer

(DVR), Voltage Sag Corrector [21], etc.

2. Reactive Power & Harmonic compensation devices (PQ conditioning devices), Active

Power Filters (APF), Automatic Power Factor Controller (APFC), SVG (Static Var

Generator), D-STATCOM, etc.

The cost of these Power Quality improvement devices usually depends on load requirement in

terms of kW or MW. It may vary from Rs. 4,000/Amp to Rs.17,000/Amp. Market survey also

reveals that there are very limited domestic manufacturers of Power Quality mitigating /

monitoring devices. Even if some types of mitigating / monitoring devices are available its size

(Rating) and features are limited. However, there are several international manufacturers in this

field. Above mentioned cost is a rough estimate of such typical devices. Estimated expenditure

has been worked out assuming that the PQ conditioning device would cost around Rs.10,000

per Amp. The investment required for PQ conditioning per kW of connected load would be

around Rs. 2,100 as calculated in Table 7-3.

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Table 7-3: Cost of Power Conditioning device for a typical DT of 500kVA1

Cost of Installing Power Conditioning device at LT Level (415V)

Reference DT Rating (kVA): 500

Power Factor Improvement

Average Loading 70.00%

Power Factor Improvement 0.8 to 0.9

kVAr requirement 46.0

PF Correction Amps 63.9

Harmonic Mitigation

Harmonic Current Amps 20.0

Total Amp Rating of PQ Conditioning Device 83.9 A

Considering Rs. 10000 per Amp

Net Investment (Rs. Lac) per 500kV DT 8.4

Connected Load is assumed to be 400kW with 0.8 pf

Investment per kW of Connected Load Rs. 2098/kW

Other than the typical Power Conditioning at the load ends in general, it is also proposed

to install Hybrid Filters in the Industries where the Adjustable Speed Drives (ASDs) or

Variable Frequency Drives (VFDs) are used. There are about 15 lakh total industrial drives of

various sizes operating in the country. The VFDs/ASDs used in industries inject distortions in

the Grid, which lead to voltage distortions, sags/swells, Unbalance etc. Breakup of these drives

is given in Table 7-4. It is proposed to install Hybrid Active Filters (Active Power Filter + 5%

Line Reactor) to mitigate Harmonics at the VFDs/ASDs in industries. A line reactor along with

the Harmonic mitigating device reduces the rating requirement of the Harmonic mitigating

device for a given load.

Table 7-4: Industrial VFDs/ASDs in India

Approximate number of motors associated with Industrial VFDs/ASDs in India

Number of LT Motors 1.5 Million approx.

0.7 to 7.5 kW (1HP to 10 HP) 1.3 Million

11 to 37.5kW (14HP to 50HP) 0.2 Million

(Source: AFF Estimates, IEEMA statistics, Primary Survey)[33]

Considering all the investments mentioned above, the total estimated investment required

in initial phase for Power Quality improvement for the loads identified in Table 7-2 is about

1 (Typical Power Conditioning Devices with ratings of 100kVAr, 140kVAr, 180kVAr, 50 A, 100A etc. are available

in the market)

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Rs. 24,840 Cr. A Breakup of this estimation is given in Table 7-5. Here, we have considered

installation of Power Conditioning devices at the LT level. The cost of installing Power

Condition Device per kW of connected load is shown in Table 7-3, this cost has been taken as

reference for the investments required to install Power Quality Conditioning devices. It has

been assumed that the ‘Power-Conditioning’ device would improve the power-factor from 0.8

to 0.9 and also mitigate the current harmonics of the order of 20 Amps at LT level (It has been

observed that the net current harmonic current is of the order of few tens of Amp in LT supply

at 415V).

Along with the Power conditioning devices, it is also necessary to install Power Quality

monitoring devices, which are available in the market with the names like Power-Quality

Analyzer, Power Quality Logger, Power Quality Monitor etc. It is proposed here to install one

monitoring device for every 50MW of connected load.

Table 7-5: Initial Investments for Power Quality Improvement

Sl No. Load Category Load Considered for

PQ Improvement

(GW)

Rate

Rs per KW


(Rs. Cr.)

A. Power Conditioning Device (Such as DSTATCOM, SVG, APF, DVR, Active Harmonic Filter, etc.)

1 Industrial 45 2,100

9,450 2 Domestic 53 11,130 3 Commercial 20 4,200

Sub-Total 24,780

Sl

No.

Number of Power Quality Monitoring

devices required

Rate

Rs per Device


(Rs. Cr.)

A. Power Quality Monitoring Device (Such as power Quality Analyzer, Power Quality Logger etc.)

1 1180 5,00,000 59 Sub-Total 59

Total Investment (A+B+C) Rs. 24,840 Cr.

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7.2 Proposed Roles & Responsibilities of Statutory Bodies/Authorities

towards ensuring Quality Supply in the Indian Power System:

Ensuring Quality Power requires contribution of various players in the entire Power Supply

value chain. Roles & Responsibility of various agencies in providing Quality Power is

proposed in Table 7-6.

Table 7-6: Roles & Responsibility of various agencies

S.No

. Activities Roles/ Responsibilities

1. Development of Power Quality Standards for Utilities and

the End-Users.

CEA/MoP/

NITI Aayog/BIS

2.

Specify electrical/electronic equipment with the necessary

resilience to Power Quality related events (e.g., Voltage

Sag, Interruptions etc.)

BIS

3. Ensure Reliable & Quality Supply Genco/CTU/STU/

DISCOM /Utilities

4. Provision of special tariff/penalty for companies/utilities/

individuals contributing to power quality. CERC/SERC

5. Regulations for periodic measurement of PQ parameters at

different voltage level by each utility CERC/SERC

6.

Design, development & installation of Power Conditioning

devices like harmonic filters, DVRs, D-STATCOMs,

APFC etc. at strategically identified nodes in the Grid (MV

and LV nodes)

Transco/ DISCOM /

Manufacturer

7. Bring awareness about power quality amongst the

stakeholders.

BEE/State Govts./

Discom/MoP/STUs/

CTU

8.

Conduct a nation-wide Power Quality Survey to reveal the

impacts of Poor Power Quality (e.g., Cost of Interruptions,

Sags, Harmonics etc.) to various stakeholders especially

Industries).

BEE/MoP/ DISCOMs

9. Use of Power Quality complied/conditioning equipment

(especially in industries/ domestic areas).

SERC/Discom/

End Users

10. Setting up PQ institutes at National Level for knowledge

dissemination, awareness and R&D activities

MoP/ State Govt/

NITI Aayog

11. Capacity Building MoP/State/DISCOM

Utilities/Genco/Transco

Discom

***

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Way Forward

This report has highlighted the importance of power quality while building an insight upon

power quality standards, pan India power quality status based on primary measurement, the ill

effects of poor power quality and possible mitigating measures required for the same. Power

Quality Measurements have been done on various voltage levels ranging from distribution (415

V) to EHV (765 kV) throughout India.

These measurements were done for 6 to 24 hours on each feeder in a non-simultaneous manner.

From the measurements, it was observed (Figure 1) that voltage harmonics are high in certain

pockets of northern India, Gujarat, Odisha, Tamil Nadu and Kerala. The higher magnitude of

Voltage Harmonics in these pockets necessitates the need for corrective measures to be taken.

High current distortions have been observed invariably at all voltage levels. Various challenges

and threats posed by poor power quality including harmonics have been discussed in this report.

Prudent mitigating measures to address these challenges, viz. STATCOM, passive harmonic

filters, active power filters, DVR, power factor conditioners etc. have been discussed and

suggested.

Installation of these devices is to be done at locations which may be decided by extensive

system studies. Sizing of these power quality devices also need to be carried out through

meticulous data analysis and simulation studies. Further course of action imperative to ensure

a good quality power at the national level is as follows:

Identification of critical nodes with threatening level of electrical pollution.

Detailed measurement of power quality for longer duration and further analysis of data.

Development of infrastructure to periodically monitor the Power-Quality parameters

across the Grid at all the Voltage Levels, including distribution network.

Assessment of various power quality improvement devices depending upon issue,

ratings, voltage level, economic considerations etc.

Development of regulatory framework and economic model to necessitate and

facilitate deployment of mitigating solutions.

Enforcement of regulations for power quality parameters for maintaining various stake

holders.

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Simulation based study for further improvement at varying voltage level.

To ensure Quality Supply in the entire Power System, any single stakeholder can’t be made

responsible. Since Power-Quality has a very broad spectrum, all the stakeholders in the Power

Supply Value chain are expected to contribute in a collaborative manner to ensure high quality

of power to end consumers. Various actions that need to be taken by different stakeholders are

enlisted below:

1. Necessary standards shall be formulated / updated under the emerging scenario of large

penetration of non-linear loads, volatile renewable generation capacity addition,

increasing inverter penetration & stringent quality requirements by various categories

of load.

2. Utilities need to strengthen/upgrade their network to ensure high quality of power.

3. Manufacturers need to produce electrical / electronic appliances/ gadgets meeting the

standards and end consumer needs.

4. Power conditioning equipment manufacturer need to produce devices that would

facilitate maintaining required power quality.

5. Adequate compensation to utilities for ensuring high quality power through special

tariff /penalty schemes.

6. Awareness about Power Quality among various stakeholders.

7. Capacity building and training program need to be conducted among various

stakeholders.

8. Monitoring / control of Power Quality at various stages of power supply value chain.

9. Establishment of National and State level Organization for certifying Power Quality.

10. Use of Power Quality complied / conditioning equipment by the end consumers.

11. Research, development& demonstration work in Power quality industries and academic

institutions.

12. Regulations for measurement of PQ parameters at different voltage level by each utility/

major establishment periodically.

Note: This report is an attempt to study and analyze the impact of various power quality

parameters in the power system at various voltage levels in different towns and cities across

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the country. It includes the baseline data about power quality parameters in different places.

However, this needs to be periodically updated and reviewed. Inputs / feedback from all

stakeholders would help in further improvement and making this report more pragmatic.

***

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Exhibit A

Power Quality Characteristics of

Household Equipment Power quality measurement was carried out on various commonly used appliances in day

to day life. Summary of observation made during measurement is shown below. Waveform /

harmonics presented here correspond to a particular appliance only. Therefore, these are

indicative in nature and should not be generalised for all such appliances.

1. Laptop

Voltage Current Frequency Output

Power

Input

Power

Reactive

Power

Power

Factor

THD TDD

228.3 V 0.293 A 50 Hz 36.4W 77.5 VA -5.7 VAR 0.47 179.08% 27.8%

Figure 1: Voltage and current waveform of laptop

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Figure 2: Phasor Analysis of Laptop

Figure 3: Harmonics analysis of laptop

The Current waveform contains spikes in phase with the voltage waveform, but still the

overall power-factor is 0.47 because of the Harmonics. Actual Power-factor is about

half of displacement power factor (DPF=cosΦ1=0.987) indicating the harmonics in

current waveform have strong impact on power-quality

The odd Harmonics are dominant in current waveform.

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Total current Harmonic distortion is very High (=179%), mainly because of 3rd, 5th,

7th and 9th Harmonics

2. Computer with TFT Monitor


Power

Input

Power

Reactive

Power

Power

Factor

THD

223.9V 0.861A 49.8 Hz 157.2W 204.2VA 130.5

VAR

0.76 91.2%

Figure 4: Voltage and Current Waveforms of a LCD Desktop

Figure 5: Harmonics analysis of a LCD Desktop

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Current waveform is contains spikes due to the presence of all odd harmonics. 3rd and 5th

harmonic currents are the most dominant and contribute to very high total harmonic

distortion

LCD computer monitor draws a large amount of reactive power and its power factor is poor

Even harmonics are absent

3. Computer with CRT Monitor


Power

Input

Power

Reactive

Power

Power

Factor

THD

230.6V 0.616A 49.8 Hz 103W 138.2VA 92 VAR 0.75 75.4%

Figure 6: Voltage and current waveforms of a CRT computer monitor

The Current Waveform is exhibits spikes.

CRT monitor draws a large amount of reactive power and its THD is 75.4% which is very

high

Its current waveform is highly distorted due to the presence of all major odd harmonics.

Third harmonic component is the most dominating current harmonics

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Figure 7: Harmonics analysis of a CRT computer monitor

4. Desktop Monitor (TFT)


Power

Input

Power

Reactive

Power

Power

Factor

THD

(Current)

234V 0.104 49.92Hz 10.1 24.5 7.8VAR 0.41

(Leading)

161.85

Figure 8: Phasor diagram for a Desktop Monitor

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Figure 9: Current harmonics in a Desktop Monitor

Figure 10: Voltage and current waveforms for a Desktop Monitor

Current waveform contains spikes, with primary component of current leading the

primary component of Voltage waveform by 38 degree.

Overall THD in current is very high in this case (~=162%).

All the modern electronic loads with BJTs, MOSFETs etc, in their chips generally

draw distorted current spikes with leading pf.

5. Table Fan


Power

Input

Power

Reactive

Power

Power

Factor

THD

234V 0.263 A 50 Hz 61.5W 61.7 VA 5.1 VAR 0.995 3%

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Figure 11: Voltage and current waveforms of a table fan

Figure 12: Phasor diagram for a table fan

Current waveform is perfect sinusoidal, with primary component of current lagging

the primary component of Voltage waveform by 6 degree.

Current waveform is perfect sinusoidal because of the resistive regulator in the fan.

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Figure 13: Current harmonics in a table fan

Overall THD is very low in this case (~3%).

Table fan being an inductive load is consuming reactive power from the supply.

6. Small Tube light


Power

Input

Power

Reactive

Power

Power

Factor

THD

234.6V 0.049 A 50 Hz 6.6W 11.6 VA 2.4 VAR 0.57 129.8%

Figure 14: Voltage and current waveforms of a tube light

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Figure 15: Phasor diagram for a tube light

The Current waveform contains spikes in phase with the voltage waveform, but still

the overall power-factor is very low (=0.57) because of the Harmonics.

The odd Harmonics are dominant.

Total Harmonic distortion is very High (=129.8%), mainly because of 3rd, 5th, 7th and

9th Harmonics.

Figure 16: Harmonics analysis of a tube light

7. Mobile Charger

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Power

Input

Power

Reactive

Power

Power

Factor

THD

234.4V 0.053 A 50 Hz 6.1W 12.4 VA -1 VAR 0.49 172.1%

Figure 17: Voltage and current waveforms of a mobile charger

Figure 18: Phasor diagram for a mobile charger

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Figure 19: Harmonics analysis of a mobile charger

The Current waveform contains spikes in phase with the voltage waveform, but still

the overall power-factor is very low (=0.49) because of the Harmonics.

To odd current harmonics are dominant.

Total current Harmonic distortion is very High (=172.1%), mainly because of 3rd, 5th,

7th and 9th Harmonics.

8. Printer under idle condition:


Power

Input

Power

Reactive

Power

Power

Factor

THD TDD

238.6V 0.454A 50 Hz 76.9W 108.6VA 65.1 VAR 0.71 40.2% 11.35%

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Figure 20: Voltage and current waveforms of a printer

Figure 21: Phasor diagram for a printer

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Figure 22: Harmonics analysis of a printer

Current waveform is distorted.

Under idle condition the current drawn by the printer is very less i.e. 0.454A. But the

waveform is highly distorted and consists of odd harmonics.

The most predominant of them is the third harmonic.

Fundamental current leads the fundamental voltage by 40° which is the cause of poor power

factor (0.71).

9. Printer (during warm-up)


Power

Input

Power

Reactive

Power

Power

Factor

THD

235V Upto 5A 49.99Hz Upto

1.17kW Upto

1.14kVA Upto 0.4

kVAR 0.3 to 1 40%

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Figure 23: Voltage (r.m.s. ) and current (r.m.s. ) during warm-up for a printer

During initial warm-up process a normal printer draws upto 5.1 Amps of current&

1.2kW Power!

This inrush of current causes multiple sags in the Voltage profile (as shown in the figure

above).

Multiple Transients in the Voltage & Current waves occur during start-up process of a

printer.

Figure 24: Current (instantaneous) spikes during starting of a printer

10. Fan rotating at slow speed


Power

Input

Power

Reactive

Power

Power

Factor

THD

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230V 0.165A 49.8 Hz 14.75W 37.75VA 34.75VAR 0.39 5.2%

Figure 25: Voltage and current waveforms of a fan rotating at less speed

Figure 26: Harmonics analysis of a fan rotating at less speed

Current Waveform is almost sinusoidal

THD at less speed was found to be 5.2 %

Only odd harmonics are present

3rd Harmonic is the most dominant (=5.2%).

All other harmonics are less than 0.5%

11. Fan rotating at max.speed

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Power

Input

Power

Reactive

Power

Power

Factor

THD

228.5V 0.33A 49.7 Hz 75.25W 76VA 9.75VAR 0.99 6%

Figure 27: Voltage and current waveforms of a fan rotating at max speed

Figure 28: Harmonics analysis of a fan rotating at max speed

THD at max speed was found to be 6 %

Presence of both even (4th,6th) and odd harmonics(3rd ,5th ) and existence of 3rd harmonic

is around 5%

Dominant harmonics – 3rd (5.9%) and 5th (0.9%)

All other harmonics are less than 0.2%

Power factor increases with increase in speed

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12. LED Bulb (2.5W)


Power

Input

Power

Reactive

Power

Power

Factor

THD

225.3V 0.047A 49.8 Hz 2.5W 10.5VA 10.25VAR 0.24 31.3%

Figure 29: Voltage and current waveforms of LED bulb

Figure 30: Harmonics analysis of LED bulb

The current waveform is distorted, while voltage is sinusoidal

Presence of both even and odd harmonics and THD was found to be 31.3 % which is high

enough

Dominant harmonics – 3rd, 5th, 7th, 9th, 1th and 13th

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Existence of 3rd harmonic is around 23 %

13. LED Bulb (7W)


Power

Input

Power

Reactive

Power

Power

Factor

THD

228.6V 0.31A 50Hz 7.1W 7.5VA 2VAR 0.95 16.1%

Figure 31: Voltage and current waveforms of a 7W LED Bulb

Figure 32 Current harmonics drawn by a 7W LED bulb

The LED bulb under test draws mostly 3rd and 7th Harmonic Current which to about

16% of Total Harmonic Distortion in Current.

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Figure 33: Phasor diagram for a 7W LED bulb

Power Factor is very good.

Fundamental current leads the fundamental voltage by 15 degrees.

14. LED Bulb (12W)


Power

Input

Power

Reactive

Power

Power

Factor

THD

238V 0.09A 50.05Hz 10.6 W 21.1 VA 2.8VAR 0.5 164 %

Figure 34: Voltage and current waveforms of a 12W LED Bulb

The current wave exhibits spikes with peak value as high as 0.32 A while the r.m.s.

value is only 0.09 A.

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Figure 35: Current harmonics drawn by a 12W LED bulb

Figure 36: Phasor diagram for a 12W LED bulb

Effective power factor is very low (0.5) which causes excessive heating.

15. Refrigerator


Power

Input

Power

Reactive

Power

Power

Factor

THD

228.6V 1.065A 50.4 Hz 146W 243VA 194.25VAR 0.6 8.8%

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Figure 37: Voltage and current waveforms of Refrigerator

Figure 38: Harmonics analysis of Refrigerator

Current Waveform is almost sinusoidal

THD very low as compared to other household appliances (=8.8 %)

3rd Harmonic is the most dominant (=5.2%) followed by 2nd Harmonic

All other harmonics are negligible

16. Oven

Voltage Current: Frequency Output

Power

Input

Power

Reactive

Power

Power

Factor

THD

220.9V 6.68A 50.3Hz 1377.5W 1470VA 510KVAR 0.99 32%

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Figure 39: Voltage and current waveforms of oven

Figure 40: Harmonics analysis of Oven

Current waveform is slightly distorted in nature due to the domination of 3rd harmonic. 3rd

and 5th harmonic currents are the most dominant and contribute to very high total harmonic

distortion

Oven draws a large amount of reactive power

Even harmonics are absent

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References 1. Bhim Singh, Kamal Al-Haddad, Ambrish Chandra, “A review of active filters for power

quality improvement”, IEEE Trans. on industrial electronics, Vol.46, No. 5, pp. 960-

971, October 1999.

2. “Economic Framework For Power Quality”, CIGRE/CIRED, Joint Working Group

C4.107.

3. IEEE, “IEEE Recommended Practices and Requirements for Harmonic Control in

Electrical Power Systems,” IEEE Std. 519-1992, revision of IEEE Std. 519-1981.

4. “Consequences of Poor Power Quality – An Overview”, Sharmistha Bhattacharyya and

Sjef Cobben, Technical University of Eindhoven, The Netherlands

5. Draft IEC 61000-4-30 Ed. 1.0): “Electromagnetic compatibility (EMC) – Part 4-30:

Testing and measurement techniques -- Power quality measurement methods”

(77A/356/CDV)

6. A. de Almeida, L. Moreira. J. Delgado ,“Power Quality Problems and New Solutions”,

ISR – Department of Electrical and Computer Engineering, University of Coimbra,

Pólo II 3030-290 Coimbra

7. “The Cost of Poor Power Quality”, David Chapman Copper Development Association

March 2001 (Version 0b November 2001)

8. Central Electricity Authority (Grid Standards) Regulations, 2006.

9. “The importance of good power quality”, Dr. Kurt Schipman, Dr. François Delincé,

ABB Power Quality Products, Belgium

10. S.Khalid, Bharti Dwivedi, “Power quality issues, problems, standards and their effects

in industry with corrective means”, International Journal of Advances in Engineering

& Technology, May 2011, Vol. 1,Issue 2,pp.1-11

11. The “The WTO, harmonization of international standards, and electric utilities”, Naoki

Kobayashi, USJP Occasional Paper 08-05, Harvard University

12. “Lack of affordable & quality power: Shackling India’s growth story”, FICCI, New

Delhi

13. Sagar Kondaveeti, M. Jaya Bharata Reddy, D. K. Mohanta, “Power Quality Analysis

on EHV Transmission line Using Modified S-Transform”

14. “A Review of Harmonic Mitigation Techniques”, Gonzalo Sandoval & John Houdek,

2005.

15. “Study on estimation of costs due to electricity interruptions and voltage disturbance”,

Matthias Hofmann, Helge Seljeseth, Gro Holst Volden, Gerd H. Kjalle, Sintef energy

research, December, 2010

16. “Guidelines of good practices on estimation of cost due to electricity interruptions and

voltage disturbances”, Council of European Energy Regulators, December 2010

17. Navjot Kaur, Gurdip Singh, M. S. Bedi, Tejpal Bhatti, “Customer interruption cost

assessment: an Indian commercial survey”, IEEE, 2002

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202

18. Daniel J Carnovale, Thomas J Dionise, Thomas M Blooming, “Price and performance

considerations for harmonic solutions”

19. Brahm Segal, “Costs and benefits of harmonic current and power factor reduction for

variable speed drives in an industry facility”

20. “Power quality standards: CBEMA, ITIC, SEMI F47, IEC 61000-4-11/34”, EPRI

21. William E Brumsickle, Robert S Schneider, Glen A. Luckjiff, Deepak M divan, Mark

F McGranaghan, “Dynamic sag correctors: Cost-effective industrial power line

conditioning”, IEEE, 20001, Vol 37, No 1

22. Kristina Hamachi, LaCommare, Joesph H Eto, “Cost of power interruptions to

electricity consumers in the United States”, Ernest Orlando Lawrence Berkeley national

laboratory, February, 2006

23. Jonathan Manson, Roman Targosz, “European power quality survey report”, Leonardo

Energy, November, 2008

24. Mark Mcgranaghan, Dave Mueller, “Effects of voltage sags in process industry

applications”, Electrotek Concepts.

25. Kurt Schipman, Francios Delince, “The importance of good power quality”, ABB,

Belgium

26. Bill Dabbs, Jeff Lamoree & Bob Zavadil, Marek Samotyj, “The power quality

database: software tool for utility engineers to solve problems”, IEEE

27. Liu Yu-quan, Hua Huang-Sheng, WU Guo-pei, Wang Li, “Research for the effects of

high speed electrified railway traction load on power quality”, IEEE, 2011

28. B E Khshare, A A Ghatol, T N Date, “Power quality survey of 33 kV Indian industrial:

results and remedial actions”

29. Jose Gutierrez Iglesias, Detmar Arlt et al,“Economic frame work power quality” JWG

CIGRE-CIRED C4.107, 2011.

30. Sara Nourollah, Mehdi Moallem, “A data mining method for obtaining global power

quality index” 2nd International Conference on Electric Power and Energy Conversion

Systems (EPECS), 2011.

31. Fayyaz Akram M, Mumtaz Bajwa S, “A sample power quality survey for emerging

competitive electricity market in Pakistan” Technology for the 21st Century

Proceedings, Multi Topic Conference, IEEE INMIC ,2001.

32. Ding Zejun, Zhu Yongqiang, Chen Caihong, “Comprehensive evaluation of power

quality based on meaningful classification 5th International Conference on .

33. AFF Estimates, IEEMA Statistics, Primary Survey.

34. EPRI, “The Economics of Customer Power”, IEEE T&D show, 2003.

35. B.E. Kushare, A.A. Ghatol, T.N. Date, “Power Quality Survey of 33 kV Industrial

Supply System: Results and Remedial Actions”, RPS 2007.

36. Primen Study, “The Cost of Power Disturbances to Industrial & Digital Economy

Companies”, 2001.

37. IEEE, “IEEE Recommended Practice for the Transfer of Power Quality Data”, IEEE

Std 1159.3-2003

http://ieeexplore.ieee.org/xpl/mostRecentIssue.jsp?punumber=7812

http://ieeexplore.ieee.org/xpl/mostRecentIssue.jsp?punumber=5605056

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Books:

1. Mohan, Undeland and Robbins, Power Electronics, John Wiley and Sons, 1995.

2. R. C. Dugan, M. F. McGranaghan, S. Santosa, and H. W. Beaty, Electrical Power

Systems Quality, 2nd edition, McGraw-Hill, 2002.

3. IEC, Electromagnetic Compatibility, Part 3: Limits- Sect.2: Limits for Harmonic

Current Emission,” IEC 1000-3-2, 1st ed., 1995.

4. Mohan, Underland and Robbins, Power Electronics, John Wiley and Sons, 1995.

5. Alexander Kusko, Marc T. Thompson, “Power Quality in Electrical Systems, McGraw-

Hill, New York, 2007.

6. PQ in Switzerland. M. Levet, UCS, 1998

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