Mahagenco Harmonic Analysis Report

7/30/2019 Mahagenco Harmonic Analysis Report

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Reg off:Harmony House Office No 10,797/1A Bhandarkar RD Pune-411004,Tel:020-25672901

Customer: Mahagenco, chandrapur

Harmonic Analysis Report

IntroductionInstruments used for Harmonic analysis.Limits for harmonics.Observations.RecommendationsWorks: Electronic Zone Sector-7, Plot no 31,PCNDTA Bhosari Pune-27, [email protected]


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ACKNOWLEDGEMENT

Claritas Power System Solution Pvt Ltd. Pune, places its sincere gratitude, forhaving entrustedon harmonic study conducted at Mahagenco, chandrapur.

Our sincere thanks all staff members of various departments for excellent co-ordination duringfield measurements and providing accurate data required during harmonic study Our specialthanks to the all members of Electrical Maintenance team for their valuable timeextended to thepower quality audit team during the field measurement and providing other technical informationrequired in preparing the harmonic study report.


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INSTRUMENT USED :

Harmonic analysis was conducted using KRYKARD make harmonic analyzer typeALM-30 Consisting of two phase voltage prode max 600volts ,Three phase tonge testerMax 1 to 3000A. analyzer is communicated to computer through RS232 port for Printoutsof captured data.

The following electrical parameters can be measured and viewed in 3simultaneously.

Line to neutral voltageLine to line voltageCurrent on each phaseFrequencyPower factor

KVAKWKVARVoltage Harmonics-THD,L1,L2,L3,N, 1-49thCurrent Harmonics-THD,L1,L2,L3,N,1-49thTransientsInrush current

Unbalance V, I, WPower & EnergySwellsAll the snap shots of above reading are stored in non-volatile memory ofALM-30


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ABBREVIATION

Symbol AbbreviationA AmpereV VoltsKV Kilo voltsKVA Kilo volt ampereKVAR Kilo volt ampere reactiveKW Kilo wattsMD Maximum demand%THD Percentage Total harmonic distortion% THDv Percentage voltage Total harmonic distortion% THDi Percentage current Total harmonic distortion% TIHDv Percentage voltage Total inter harmonicdistortion% TIHDi Percentage current Total inter harmonicdistortionVoltage sag Reduction in RMS voltage from 90% to 10% forthe time period from 10 msec. to 1 min.Voltage swell Increase in RMS voltage from 110% to 180% forthe time period from 10 msec. to 1 min.Transient Sudden non power frequency change in the

voltage or current from steady state.%Vunb Percentage voltage unbalance factor%Iunb Percentage current unbalance factorKF Crest factor%U2,U3,.,U50 Percentage individual voltage harmonics from 2order to 50 order%I2,I3,.,I50 Percentage individual current harmonics from 2order to 50 orderMax.val. Maximum value of the parameter over themeasurement periodAvg. val. Average value of the parameter over themeasurement periodMin.val. Minimum value of the parameter over the

measurement period


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IMPACT OF HARMONICS ON THE OPERATIONS OF VARIOUS EQUIPMENTS:

It is well known that a nonlinear load draws a highly distorted current from thesource, which consists ofharmonics, fundamental active and reactive current components. If the source or/and the load isunbalanced, the source also contains negative sequence currents. The impact of harmonics on variousequipments depends on the phase sequences of harmonics. Table 1.2 shows the impact of harmonic phasesequence.

Table 1.1: Classification and Effect of Harmonic

Harmonic Order 1 2 3 4 5 6 7 8 9 10 11Frequency(Hz) 50 100 150 200 250 300 350 400 450 500 550Phase sequence + -0 + -0 + -0 + -Effect on Equipment * # $ * # $ * # $ * #* Heating # heating plus motor problem $ heating plus add in a neutral of a three phase four wire

Tripplen harmonics become an important issue for grounded wye system with current flowing in the

neutral and cause overloading of neutrals and telephone interferences. Transformer winding connectionshave significant impact on the flow of tripplen harmonic currents from single phase non linear loads. Inthe Wye delta transformer the tripplen harmonic currents enter in the Wye side,since they are in phaseand add in the neutral. The delta winding provides ampere turns balance so theycan flow, but they remaintrapped in delta and do not show up in the line currents on delta side. The distorted supply voltage thusadversely affect the performance of other equipment connected to power system network. The variouseffects of harmonics on the operation of various equipments are tabulated in Tab

le 1.2

Table 1.2: Effect of Harmonics on Equipments

Equipment EffectsCapacitor banks Overheating , Insulation failure, Failure of internal fusesMotors Overheating, Increased noise level, Additional vibrationsTransformers Overheating, Possible resonance between transformer winding and linecapacitance, Insulation stressProtection equipment False tripping , No tripping when requiredMeasuring devices Wrong measurementElectronic devices Wrong pulse on data transmission , Over/under voltage Flicker

ing of screenIncandescent lamps Reduced life time, FlickerCables, bus bar, neutrals OverheatingGenerators Harmonic pairs 5th and 7th have potential for creating mechanical oscillationsin turbine generators


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Observation:

Sr. No Location Voltage V THD A THD1. 11 kv incomer(Filter bank off)Filter rating : 1500kvar,13 kv AHPFC panelRef : annexure 111.39 KV 1.4 % Total = 7.5 %3rd = 2.3%5th = 6.1%7th = 1.3 %9th = 0.2%11th = 0.6 %13th = 0.3 %2. 11 kv incomer(Filter bank on)Filter rating : 1500 kvar,13 kv AHPFC panelRef : annexure 211.54 KV 0.8 % Total = 5.2 %3rd = 1 %

5th = 4.4%7th = 1.2%9th = 0.0%11th = 0.4 %13th = 0.3 %

Abbreviations:

KV: Kilo Volts

V: VoltsA: AmpereV THD: Total Harmonic Distortion Voltage

A THD: Total Harmonic Distortion Current


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Annexure 1

KRYKARD ALM 30Location: 11 KV Incomer side (Filter bank off)

Voltage

Voltage Harmonics


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Current Harmonics (A THD% )3rd :

Current Harmonics (A THD% )5th:


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Annexure 2

KRYKARD ALM 30Location: 11 KV Incomer side (Filter bank on)

Voltage

Voltage Harmonics


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Current Harmonics (A THD% )3rd :



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Recommendations:

CPSSPL, Pune had proposed to add 1500 kvar, 13 kv AHPFC panel to boost up existing Power Factor tocompensate additional load, so as to have uniform Power Factor at 33KV bus alongwith Harmonicsuppression.

Comments:

Implemented and working satisfactorily

Conclusion:

There is a improvement in following parameters as under;

Power factor =0.996 (lag) to unityTHD (I) =5%THD (V) =1%


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HarmonicDistortionLimitIEEE-519,1992

IEEErecommendedpracticesandrequirementsforharmoniccontrolinelectricalpowersystemrepresentsastandardlevelof

acceptableharmonicdistortioninapowersystem

A.CurrentDistortionLimits

(120Vto69KV)-UsersResponsibilityISC/IL


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2.51.00.58.050


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ofOddharmonicslimitsISCMaximumShortcircuitatthepointofcommoncoupling(PCC)correspondingtosystemMVAlevelIL-MaximumdemandLoad

Current(FundamentalFrequency)atcommoncouplingh-HarmonicnumberIn-nthHarmoniccurrent*(like

I5is5THharmonicCurrentetc)

11


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B.VoltageDistortionLimits-Utilitys&SystemsResponsibilityBusVoltageatIndividualVoltageTHDRemarksPCCDistortion=161KV3.01.55.0

2.5HVsystemcanhaveupto2.0%THDwherethecauseisan

HVDC>161KV1.01.5terminalthatwillattenuatebythetimeit

istappedforauser


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Detect and eliminate harmonics: why?

From Electrical Installation Guide

Disturbances caused by harmonics

Harmonics flowing in distribution networks downgrade the quality of electrical power. This can have anumber of negative effects:

Overloads on distribution networks due to the increase in rms currentOverloads in neutral conductors due to the cumulative increase in third-order harmonics created bysingle-phase loadsOverloads, vibration and premature ageing of generators, transformers and motorsas well as increasedtransformer humOverloads and premature ageing of power-factor correction capacitors

Distortion of the supply voltage that can disturb sensitive loadsDisturbances in communication networks and on telephone linesEconomic impact of disturbances

Harmonics have a major economic impact:

Premature ageing of equipment means it must be replaced sooner unless oversizedright from the startOverloads on the distribution network can require higher subscribed power levelsand increase losses

Distortion of current waveforms provokes nuisance tripping that can stop productionIncreasingly serious consequences

Only ten years ago, harmonics were not yet considered a real problem because their effects on distributionnetworks were generally minor. However, the massive introduction of power electronics in equipment hasmade the phenomenon far more serious in all sectors of economic activity.

In addition, the equipment causing the harmonics is often vital to the company or organisation.

Which harmonics must be measured and eliminated?

The most frequently encountered harmonics in three-phase distribution networks are the odd orders.Harmonic amplitudes normally decrease as the frequency increases. Above order 50, harmonics arenegligible and measurements are no longer meaningful. Sufficiently accurate measurements are obtainedby measuring harmonics up to order 30.


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Utilities monitor harmonic orders 3, 5, 7, 11 and 13. Generally speaking, harmonic conditioning of thelowest orders (up to 13) is sufficient. More comprehensive conditioning takes into account harmonicorders up to 25.


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Effects of harmonics -Resonance


The simultaneous use of capacitive and inductive devices in distribution networks results in parallel orseries resonance manifested by very high or very low impedance values respectively. The variations inimpedance modify the current and voltage in the distribution network. Here, onlyparallel resonancephenomena, the most common, will be discussed.Consider the following simplified diagram (see Fig. M6) representing an installation made up of:

A supply transformerLinear loadsNon-linear loads drawing harmonic currentsPower factor correction capacitorsFig. M6: Diagram of an installation

For harmonic analysis, the equivalent diagram (see Fig. M7) is shown below.Impedance Z is calculated by:

Neglecting R and where:Ls = Supply inductance (upstream network + transformer + line)C = Capacitance of the power factor correction capacitorsR = Resistance of the linear loadsIh = Harmonic currentResonance occurs when the denominator 1-LsCw2 tends toward zero. The corresponding frequency is


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called the resonance frequency of the circuit. At that frequency, impedance is at its maximum and highamounts of harmonic voltages appear with the resulting major distortion in the voltage. The voltagedistortion is accompanied, in the Ls+C circuit, by the flow of harmonic currentsgreater than those drawnby the loads.The distribution network and the power factor correction capacitors are subjected to high harmoniccurrents and the resulting risk of overloads. To avoid resonance, anti-harmoniccoils can be installed inseries with the capacitors.

Fig. M7: Equivalent diagram of the installation shown in Figure M6


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Effects of harmonics -Increased losses

From Electrical Installation GuideContents

1 Losses in conductors2 Losses in asynchronousmachines3 Losses in transformersLosses in conductors

The active power transmitted to a load is a function of the fundamental component I1 of the current.When the current drawn by the load contains harmonics, the rms value of the current, Irms, is greater thanthe fundamental I1.The definition of THD being:

it may be deduced that :

Figure M8 shows, as a function of the harmonic distortion:

The increase in the rms current Irms for a load drawing a given fundamental currentThe increase in Joule losses, not taking into account the skin effectFig. M8: Increase in rms current and Joule losses as a function of the THD

(The reference point in the graph is 1 for Irms and Joules losses, the case whenthere are no harmonics)The harmonic currents provoke an increase in the Joule losses in all conductorsin which they flow and additionatemperature rise in transformers, devices, cables, etc.


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Losses in asynchronous machines

The harmonic voltages (order h) supplied to asynchronous machines provoke in therotor the flow ofcurrents with frequencies higher than 50 Hz that are the cause of additional losses.

Orders of magnitude

A virtually rectangular supply voltage provokes a 20% increase in losses

A supply voltage with harmonics u5 = 8% (of U1, the fundamental voltage),u7 = 5%, u11 = 3%, u13 = 1%, i.e. total harmonic distortion THDu equal to 10%, results in additionallosses of 6%

Losses in transformers

Harmonic currents flowing in transformers provoke an increase in the copper lossesdue to the Jouleeffect and increased iron losses due to eddy currents. The harmonic voltages are responsible for iron

losses due to hysteresis.It is generally considered that losses in windings increase as the square of theTHDi and that core lossesincrease linearly with the THDu.In utility-distribution transformers, where distortion levels are limited, losses increase between 10 and15%.Losses in capacitorsThe harmonic voltages applied to capacitors provoke the flow of currents proportional to the frequency ofthe harmonics. These currents cause additional losses.

Example

A supply voltage has the following harmonics:Fundamental voltage U1, harmonic voltages u5 = 8% (of U1), u7 = 5%, u11 = 3%, u13 = 1%, i.e. totalharmonic distortion THDu equal to 10%. The amperage of the current is multipliedby 1.19. Joule lossesare multiplied by 1.192, i.e. 1.4.


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Effects of harmonics -Overloads on equipment


Generators

Generators supplying non-linear loads must be derated due to the additional losses caused by harmoniccurrents.The level of derating is approximately 10% for a generator where the overall load is made up of 30% ofnon-linear loads. It is therefore necessary to oversize the generator.

Uninterruptible power systems (UPS)

The current drawn by computer systems has a very high crest factor. A UPS sizedtaking into accountexclusively the RMS current may not be capable of supplying the necessary peak current and may beoverloaded.

Transformers

The curve presented below (see Fig. M9) shows the typical derating required fora transformersupplying electronic loadsFig. M9: Derating required for a transformer supplying electronic loads


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Example

If the transformer supplies an overall load comprising 40% of electronic loads,it must be deratedby 40%.Standard UTE C15-112 provides a derating factor for transformers as a function of the harmoniccurrents.Typical values:

Current with a rectangular waveform (1/h spectrum (1)): k = 0.86Frequency-converter current (THD 50%): k = 0.80(1) In fact, the current waveform is similar to a rectangular waveform. This isthe case for all current rectifiers (threctifiers, induction furnaces).Asynchronous machines

Standard IEC 60892 defines a weighted harmonic factor (Harmonic voltage factor)

for which the equationand maximum value are provided below.

Example

A supply voltage has a fundamental voltage U1 and harmonic voltages u3 = 2% of U1, u5 = 3%, u7 = 1%.The THDu is 3.7% and the MVF is 0.018. The MVF value is very close to the maximum value abovewhich the machine must be derated. Practically speaking, for supply to the machine, a THDu of 10% mustnot be exceeded.

Capacitors

According to IEC 60831-1 standard, the rms current flowing in the capacitors must not exceed 1.3 timesthe rated current.Using the example mentioned above, the fundamental voltage U1, harmonic voltagesu5 = 8% (of U1), u7= 5%, u11 = 3%, u13 = 1%, i.e. total harmonic

distortion THDu equal to 10%, the result is

, at the rated voltage. For a voltage equal to

1.1 times the rated voltage, the current limit is reached and it is necessary toresize thecapacitors.


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Neutral conductors

Consider a system made up of a balanced three-phase source and three identical single-phase loadsconnected between the phases and the neutral (see Fig. M10).

Fig. M10: Flow of currents in the various conductors connected to a three-phasesource

Figure M11 shows an example of the currents flowing in the three phases and theresulting current in theneutral conductor.In this example, the current in the neutral conductor has an rms value that is higher than the rms value ofthe current in a phase by a factor equal to the square root of 3. The neutral conductor must therefore besized accordingly.

Fig. M11: Example of the currents flowing in the various conductors connected toa three-phase load (In

= Ir + Is + It)


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Effects of harmonics -Disturbances affecting sensitive loads


Contents

1 Effects of distortion in the supply voltage2 Distortion of telephone signalsEffects of distortion in the supply voltage

Distortion of the supply voltage can disturb the operation of sensitive devices:

Regulation devices (temperature)Computer hardwareControl and monitoring devices (protection relays)Distortion of telephone signals

Harmonics cause disturbances in control circuits (low current levels). The levelof distortion depends onthe distance that the power and control cables run in parallel, the distance between the cables and thefrequency of the harmonics


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Effects of harmonics -Economic impact


Contents

1 Energy losses2 Higher subscription costs3 Oversizing of equipment4 Reduced service life of equipment5 Nuisance tripping and installationshutdown6 ExamplesEnergy losses

Harmonics cause additional losses (Joule effect) in conductors and equipment.

Higher subscription costs

The presence of harmonic currents can require a higher subscribed power level and consequently highercosts.What is more, utilities will be increasingly inclined to charge customers for major sources of harmonics.

Oversizing of equipment

Derating of power sources (generators, transformers and UPSs) means they must beoversized

Conductors must be sized taking into account the flow of harmonic currents. In addition, due the theskin effect, the resistance of these conductors increases with frequency. To avoid excessive losses dueto the Joule effect, it is necessary to oversize conductorsFlow of harmonics in the neutral conductor means that it must be oversized as wellReduced service life of equipment

When the level of distortion in the supply voltage approaches 10%, the duration

of the service life ofequipment is significantly reduced. The reduction has been estimated at:

32.5% for single-phase machines18% for three-phase machines5% for transformersTo maintain the service lives corresponding to the rated load, equipment must be


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oversized.


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Nuisance tripping and installation shutdown

Circuit-breakers in the installation are subjected to current peaks caused by harmonics.These current peaks cause nuisance tripping with the resulting production losses, as well as the costscorresponding to the time required to start the installation up again.

Examples

Given the economic consequences for the installations mentioned below, it was necessary to installharmonic filters.

Computer centre for an insurance company

In this centre, nuisance tripping of a circuit-breaker was calculated to have cost 100 k per hour of downtime.

Pharmaceutical laboratory

Harmonics caused the failure of a generator set and the interruption of a long-duration test on a newmedication. The consequences were a loss estimated at 17 M.

Metallurgy factory

A set of induction furnaces caused the overload and destruction of three transformers ranging from 1500to 2500 kVA over a single year. The cost of the interruptions in production wereestimated at 20 k perhour.

Factory producing garden furniture

The failure of variable-speed drives resulted in production shutdowns estimatedat 10 k per hour.


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Mahagenco Harmonic Analysis Report

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