Ner Reactive Power Management Manual 2012

One Nation. One Grid

REACTIVE POWER MANAGEMENT &

VOLTAGE CONTROL IN

NORTH EASTERN REGION

November 2012

POWER SYSTEM OPERATION CORPORATION LIMITED (A wholly owned subsidiary of Powergrid)

(A GOVT. OF INDIA UNDERTAKING ) NORTH EASTERN REGIONAL LOAD DESPATCH CENTRE

SHILLONG

Edition �

Prepared by: System Operation - I department

REACTIVE POWER MANAGEMENT AND VOLTAGE CONTROL IN NORTH EASTERN REGION

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CONTENTS

EXECUTIVE SUMMARY 5

1 Reactive Power Management and Voltage Control 6 1.1 Introduction 6

1.2 Analogy of Reactive Power 8 1.3 Understanding Vectorially 10 1.4 Voltage Stability 11 1.5 Voltage Collapse 12 1.6 Proximity to Instability 13 1.7 Reactive reserve margin 14 1.8 NER GRID – OVERVIEW 17 1.9 Reliability improvement due to local volt age regulation 20

2 Transmission Lines and Reactive Power Compens ation 21

2.1 Introduction 21 2.2 Surge impedance loading (SIL) 22 2.3 Shunt compensation in line 22 2.4 Line loading as function of line length a nd compensation 23

3 Series and Shunt Capacitor Voltage Control 37

3.1 Introduction 37 3.2 MeSEB capacity building and training document suggestion 38 3.3 THE ASSAM GAZETTE, EXTRAORDINARY, FEBRUARY 10, 2005 38

4 Transformer Load Tap Changer and Voltage Cont rol 41

4.1 Introduction 41 4.2 THE ASSAM GAZETTE, EXTRAORDINARY, FEBRUARY 10, 2005 42

5 HVDC and Voltage Control 53

5.1 Introduction 53 5.2 HVDC Configuration 53 5.3 Reactive power source 56 5.4 ”Inter-regional Transmission system for power e xport from NER to NR/WR” 56

6 FACTS and Voltage Control 57

6.1 Introduction 57 6.2 Static Var Compensator (SVC) 57 6.3 Converter-based Compensator 58 6.4 Series-connected controllers 59


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7 Generator Reactive Power and Voltage Control 60 7.1 Introduction 60 7.2 Synchronous condensers 62

8 CONCLUSION 87

9 SUMMARY 88

10 Statutory Provisions for Reactive Power Manageme nt and Voltage Control 90

10.1 Provision in the Central Electricity Authority (Technical 90 Standard for connectivity to the grid) Regulations 2007 [8]:

10.2 Provision in the Indian Electricity Grid Code (IEGC), 2010 90 10.3 THE ASSAM GAZETTE, EXTRAORDINARY, FEBRUARY 10, 200 5 95

11. Bibliography 99

Details of List

LIST-1: 400 KV LINE DETAILS OF POWERGRID IN NORTH E ASTERN REGION 25 LIST-2: 400 KV LINE (CHARGED AT 220 KV) DETAILS OF POWERGRID IN NORTH

EASTERN REGION 25

LIST-3: 220 KV LINE DETAILS OF POWERGRID IN NORTH EASTERN REGION 25

LIST-4: 132 KV LINE DETAILS OF POWERGRID IN NORTH EASTERN REGION 26

LIST-5: 132 KV LINE DETAILS OF NEEPCO IN NORTH EAS TERN REGION 27

LIST-6: 132 KV LINE DETAILS OF AEGCL IN NORTH EAST ERN REGION 27

LIST-7: 132 KV LINE DETAILS OF MANIPUR IN NORTH EA ST 28

LIST-8: 132 KV LINE DETAILS OF TSECL IN NORTH EAST ERN REGION 29 LIST-9: 132 KV LINE DETAILS OF NAGALAND IN NORTH E ASTERN REGION 29

LIST-10: 132 KV LINE DETAILS OF MIZORAM IN NORTH E ASTERN REGION 30 LIST-11: 132 KV LINE DETAILS OF MeECL IN NORTH EAST 30

LIST-12: 132 KV LINE DETAILS OF ARUNACHAL PRADESH I N NORTH EAST 31 LIST-13: 66 KV LINE DETAILS OF NORTH EASTERN REGION 31 LIST-14: SHUNT COMPENSATED LINES IN NORTH EASTE RN REGION 32

LIST-15: SHUNT COMPENSATED INTER – REGIONAL LIN ES IN NORTH EASTERN REGION 33

LIST-16: INTER-STATE LINE DETAILS OF NORTH EASTERN REGION 34

LIST-17: FIXED, SWITCHABLE AND CONVERTIBLE LINE REACTORS IN NORTH EASTERN REGION 35

LIST-18: BUS REACTORS IN NORTH EASTERN REGION 36

LIST-19: TERTIARY REACTORS ON 33 KV SIDE OF 400 /220/33 KV ICTS IN NORTH EASTERN REGION 36

LIST-20: SUBSTATIONS IN NER 39

LIST-21: SHUNT CAPACITOR DETAILS OF NORTH EASTE RN REGION 40

LIST-22: ICT DETAILS OF POWERGRID IN NORTH EASTERN REGION 43

LIST-23: ICT DETAILS OF NEEPCO IN NORTH EASTERN RE GION 43

LIST-24: ICT DETAILS OF NHPC IN NORTH EASTERN REGI ON 44


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LIST-25: ICT DETAILS OF ARUNACHAL PRADESH IN NO RTH EASTERN REGION 44

LIST-26: ICT DETAILS OF AEGCL IN NORTH EASTERN REG ION 44

LIST-27: ICT DETAILS OF MANIPUR IN NORTH EASTERN REGION 49

LIST-28: ICT DETAILS OF MeECL IN NORTH EASTERN RE GION 49

LIST-29: ICT DETAILS OF MIZORAM IN NORTH EASTERN REGION 50

LIST-30: ICT DETAILS OF NAGALAND IN NORTH EASTERN REGION 51

LIST-31: ICT DETAILS OF TSECL IN NORTH EASTERN RE GION 51

LIST-32: ICT DETAILS OF OTPC IN NORTH EASTERN REG ION 52 LIST-33: TRANSMISSION/TRANSFORMATION/VAR COMPENSAT ION CAPACITY OF NER 52

List of Figures

Fig1. Voltage and Current waveforms 6 Fig2. Power Triangle 7 Fig3. Boat pulled by a Horse 8 Fig4. Direction of pull 8 Fig5. Vector representation of the analogy 8 Fig6. LABYRINTSPEL 9 Fig7. Vector representation 10 Fig8. Time frames for voltage stability phenomena 13 Fig9. PV curve and voltage stability margin under different conditions 14 Fig10. Average cost of reactive power technologies 16 Fig11. NER grid map 17 Fig12. SIL vs. Compensation 23 Fig13. Switching principles of LTC 41 Fig14. HVDC fundamental components 55 Fig15. Static VAR Compensators (SVC) 58 Fig16. STATCOM topologies 58 Fig17. Series-connected FACTS controllers 59 Fig18. D-Curve of a typical Generator 60

Annexure: Capability Curve of generating machines o f NER 1 LTPS UNIT 5, 6 & 7 CAPABILITY CURVE 63 2 NTPS UNIT 1, 2 & 3 CAPABILITY CURVE 64 3 NTPS UNIT 4 CAPABILITY CURVE 65 4 NTPS UNIT 6 CAPABILITY CURVE 66 5 LTPS CAPABILITY CURVE 67 6 NTPS CAPABILITY CURVE 68 7 UMIUM ST I CAPABILITY CURVE 69 8 UMIUM STAGE II CAPABILITY CURVE 70 9 UMIUM STAGE III CAPABILITY CURVE 71 10 UMIUM STAGE IV CAPABILITY CURVE 72 11 AGBPP UNIT 5, 6, 7, 8 & 9 CAPABILITY CURVE 73 12 AGBPP UNIT 1, 2, 3 & 4 CAPABILITY CURVE 74 13 AGTPP CAPABILITY CURVE 75 14 DOYANG HEP UNIT 1 CAPABILITY CURVE 76 15 KHANDONG HEP UNIT 2 CAPABILITY CURVE 77 16 KOPILI HEP UNIT 1 CAPABILITY CURVE 78 17 KOPILI HEP UNIT 2 CAPABILITY CURVE 79 18 KOPILI HEP ST II CAPABILITY CURVE 80 19 RANGANADI HEP CAPABILITY CURVE 81


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20 LOKTAK HEP CAPABILITY CURVE 82 21 ROKHIA UNIT 3, 4 & 6 CAPABILITY CURVE 83 22 ROKHIA & BARAMURA CAPABILITY CURVE 84 23 OTPC PALATANA GTG CAPABILITY CURVE 85

24 OTPC PALATANA STG CAPABILITY CURVE 86

List of Tables

Table 1 Reactive power compensation sources 16 Table 2 Fault level at important sub-stations of N ER 19 Table 3 Line Parameters and Surge Impedance Loadin g of Different Conductor Type 24 Table 4 Equipment preference 37 Table 5 List of units in NER to be normally operat ed with free governor

action and AVR in service 62 Table 6 IEGC Operating Voltage Range 93


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EXECUTIVE SUMMARY

Quality of power to the stakeholders is the question of the hour worldwide. Enactment of several regulations viz. IE act – 2003 , ABT, Open access regulations, IEGC and several other amendments are in the direc tion towards improvement of system reliability and power quality.

It is also significant to mention that due to the ma ssive load growth in the country, the existing power networks are operated under grea ter stress with transmission lines carrying power near their limits. Increase in the complexity of network and being loaded non-uniformly has increased its vulner ability to grid disturbances due to abnormal voltages (High and Low). In the past, r eason for many a black outs across the world have been attributed to this cause .

Three objectives dominate reactive power management. Firstly, maintaining adequate voltage throughout the transmission system under normal and contingency conditions. Secondly, minimizing conges tion of real – power flows. Thirdly, minimizing real – power losses. Also with dynamic ATCs, var compensation, congestion charges, if not seriously thought, it may have serious commercial implications in times to come due to the amount of bulk power transfer across the country.

Highlights of the rolling year vis-à-vis NER grid in cludes commissioning of 400 kV Pallatana – Silchar D/C, 400/220 kV 315 MVA ICT at Misa, 400/132 kV 2x200 MVA ICT at Silchar, 400/132 kV 125 MVA ICT at Palatana, 132 kV Silchar – Badapur D/C, 132 kV Silchar – Srikona D/C, 132 kV Palatana – Ud aipur D/C, 132 kV Palatana – Surajmani nagar D/C; Bus reactors at 400 kV Balipar a(80 MVAR), 400 kV Silchar(2x63 MVAR), 400 kV Palatana(80 MVAR); Line reactors at 400 kV Silchar end(2x50 MVAR), 400 kV Pallatana end(2x63 MVAR) and Myntdu-Leshka (2x42 MW) MeECL Hydro plant has led to reinforcement in the N ER grid elements and greater options of controlling grid parameters. With the in crease in controllability compared to earlier years, grid operation has been smooth and grid parameters were maintained within the prescribed IEGC limits.

This manual is in continuation to the previous editi on to understand the basics of reactive power and its management towards voltage c ontrol, its significance and consequences of inadequate reactive power support. It also includes details of reactive power support available at present and eff orts by planners from future perspective in respect of NER grid.


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1 Reactive Power Management and Voltage

Control

1.1 Introduction

1.1.1 hat is Reactive Power ? Reactive power i s a concept used by engineers to describe the background ene rgy movement in an Alternating Current (AC) system arising from the production of

electric and magnetic fields. These fields store en ergy which changes through each AC cycle. Devices which store energy b y virtue of a magnetic field produced by a flow of current are sa id to absorb reactive power (viz. transformers, Reactors) and those which store energy by virtue of electric fields are said to generate reac tive power (viz. Capacitors) .

1.1.2 Power flows, both actual and potential, must be carefully controlled for a

power system to operate within acceptable voltage l imits. Reactive power flows can give rise to substantial voltage changes across the system, which means that it is necessary to maintain reacti ve power balances between sources of generation and points of demand on a 'zonal basis'. Unlike system frequency, which is consistent throug hout an interconnected system, voltages experienced at poin ts across the system form a "voltage profile" which is uniquely related to local generation and demand at that instant, and is also affected by the prevailing system network arrangements .

1.1.3 In an interconnected AC grid,

the voltages and currents alternate up and down 50 times per second (not necessarily at the same time). In that sense, these are pulsating quantities. Because of this, the power being transmitted down a single line also “pulsates” - although it goes up and down 100 times per second rather than 50.

W

Fig 1. Voltage and Current waveforms


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1.1.4 To distinguish reactive power from real power , we use the reactive power

unit called “VAR” - which stands for Volt-Ampere-Re active (Q). Normally electric power is generated, transported and consum ed in alternating current (AC) networks. Elements of AC systems suppl y (or produce) and consume (or absorb or lose) two kinds of power: rea l power and reactive power.

1.1.5 Real power accomplishes useful work (e.g., runs mot ors and lights

lamps). Reactive power supports the voltages that m ust be controlled for system reliability. In AC power networks, while active power correspond s to useful work, reactive power supports voltage mag nitudes that are controlled for system reliability, voltage stabilit y, and operational acceptability .

1.1.6 VAR Management ? It is defined as the control of generator v oltages,

variable transformer tap settings, compensation, sw itchable shunt capacitor and reactor banks plus allocation of new shunt capacitor and reactor banks in a manner that best achieves a redu ction in system losses and/or voltage control.

1.1.7 Although active power can be transported over long distances, reactive

power is difficult to transmit, since the reactance of transmission lines is often 4 to 10 times higher than the resistance of t he lines. When the transmission system is heavily loaded, the active p ower losses in the transmission system are also high. Reactive power ( vars) is required to maintain the voltage to deliver active power (watts ) through transmission lines. When there is not enough reactive power, the voltage sags down and it is not possible to push the power demanded b y loads through the lines. Reactive power supply is necessary in the re liable operation of AC power systems. Several recent power outages worldwi de may have been a result of an inadequate reactive power supply which subsequently led to voltage collapse.

1.1.8 Voltage and current may not pulsate up and

down at the same time. When the voltage and current do go up and down at the same time, only real power is transmitted. When the voltage and current go up and down at different times, reactive power is also gets transmitted. How much reactive power and

which direction it is flowing on a transmission line depend on how different these two items are.

Fig 2. Power Triangle


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Although AC voltage and current pulsate at the same frequency, they peak at a different time. Power is the algebraic pr oduct of voltage and current. Over a cycle, power has an average value, called real power (P), measured in volt-amperes, or watts. There is also a portion of power with zero average value that is called reactive power (Q ), measured in volt-amperes reactive, or vars. The total power is calle d apparent power or Complex power, measured in volt-amperes, or VA.

1.2 Analogy of Reactive Power

1.2.1 Why an analogy? Reactive Power is an esse ntial aspect of the electricity system, but one that is difficult to comprehend by a lay man. The horse and the boat analogy best describe the Reactive Pow er aspect.

Visualize a boat on a canal, pulled by a horse on t he bank of the canal .

In actual the horse is not in front of the boat to do a meaningful work of pulling it in a straight path. Due to the balancing compensation by the rudder of the boat, the boat is made to move in a s traight manner rather deviating towards the bank. This is in line with th e understanding of the reactive power.

W

Fig 3. Boat pulled by a Horse Fig 4. Direction of p ull

Fig 5. Vector representation of the analogy


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1.2.1 In the horse and boat analogy, the horse’s ob jective (real power) is to

move the boat straightly. The fact that the rope is being pulled from the flank of the horse and not straight behind it, limi ts the horse’s capacity to deliver real work of moving straightly. Therefore, the power required to keep the boat steady in navigating straightly is de livered by the rudder movement (reactive power). Without reactive power t here can be no transfer of real power, likewise without the suppor t of rudder, the boat cannot move in a straight line.

1.2.2 Reactive power is like the bouncing up and do wn that happens when we

walk on a trampoline. Because of the nature of the trampoline, that up-down bouncing is an essential part of our forward m ovement across the trampoline, even though it appears to be movement i n the opposite direction.

1.2.3 Reactive power and real power work together i n the way that’s illustrated

very well by the labyrinth puzzle, LABYRINTSPEL :

The description of the puzzle begins to show why this game represents the relationship between real and reactive power:

The intent is to manipulate a steel ball (1.2cm in diameter) through the maze by rotating the knobs – without letting the ball fall into one of the holes before it reaches the end of the maze. If a ball does fall prematurely into a hole, a slanted floor inside the box returns the ball to the user in the trough on the lower right corner of the box.

1.2.4 The Objective is to twist the two knobs to ad just the angle of the platform in two directions, in order to keep the ball rollin g through the maze without falling into any holes. Those twists are RE ACTIVE POWER, which helps propel the real power through to its ultimate goal, which is delivery to the user. Without reactive power, ball falls int o holes along the way, which are NETWORK failures.

1.2.5 Both of these examples illustrate how importa nt it is to understand the

system and how it works in order to meet our object ives effectively. In the LABYRINTSPEL game, if the structure of the system is not taken into account, winning would be really easy because one k nob would be turned

Fig 6. LABYRINTSPEL


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all the way in one direction, and the other knob al l the way in the other direction, and the ball would merely roll across th e platform. If that’s the model how electricity works, then that would delive r the electrons to the end user in the form of real power. But in the game , on the trampoline, and in the electric power network, the system has m ore going on that means it’s essential to do things that seem counter intuitive, like bouncing up and down on the trampoline or turning the platfo rm in the game towards west to avoid the hole to the east, even th ough we have to go east to win.

1.2.6 In electric power, the counterintuitive thing about reactive power is to use

some power along the path to balance the flow of el ectrons and the circuits. Otherwise, the electricity just flows fro m the generator to the largest consumer (that’s Kirchhoff’s law, basically ). In this sense, reactive power is like water pressure in a water network.

1.2.7 LABYRINTSPEL game and the trampoline are good examples that the y

capture the fact that mathematically, real power an d reactive power are pure conjugates.

1.3 Understanding Vectorially

1.3.1 In practice circuits are invariably combinati ons of resistance, inductance and capacitance. The combined effect of these imped ances to the flow of current is most easily assessed by expressing the p ower flows as vectors that show the angular relationship between the powe rs waveforms associated with each type of impedance. Figure 7 sh ows how the vectors can be resolved to determine the net capacity of th e circuit needed to transfer the power requirements of the connected eq uipment.

1.3.2 The useful power that can be drawn

from the electricity distribution system is represented by the vertical vector in the diagram and is measured in kilowatts (kW).The reactive or wattless power that is a consequence of the inductive load in the circuit is represented by the horizontal vector to the right and the reactive power attributable to the circuit capacitance by the horizontal vector to the left. These are measured in kilovars (kVAr).

Fig 7. Vector representation


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1.3.3 The resolution of these vectors, which is the diagonal vector in the

diagram is the capacity required to transmit the ac tive power, and is measured in kilovolts-ampere (kVA). The ratio of th e kW to kVA is the cosine of the angle in the diagram shown as theta , and is referred to as the “power factor”.

1.3.4 When the net impedance of the circuit is sole ly resistance, so that the

inductance and capacitance exactly cancel each othe r out, then the angle theta becomes zero and the circuit has a power factor of unity. The circuit is now operating at its highest efficiency for tran sferring useful power. However, as a net reactive power emerges the angle theta starts to increase and its cosine falls.

1.3.5 At low power factors the magnitude of the kVA vector is significantly

greater than the real power or kW vector. Since dis tribution assets such as cables, lines and transformers must be sized to meet the kVA requirement, but the useful power drawn by the cust omer is the kW component, a significant cost emerges from having t o over-size the distribution system to accommodate the substantial amount of reactive power that is associated with the active power flow .

1.4 Voltage Stability

1.4.1 Power flows, both actual and potential, must be carefully controlled for a power system to operate within acceptable voltage l imits and vice versa. Not only is reactive power necessary to operate the transmission system reliably, but it can also substantially improve the efficiency with which real power is delivered to customers. Increasing re active power production at certain locations (usually near a loa d center) can sometimes alleviate transmission constraints and al low cheaper real power to be delivered into a load pocket.

1.4.2 Voltage control (keeping voltage within defined lim its) in an electric

power system is Important for proper operation of e lectric power equipment and saving it from imminent damage, to re duce transmission losses and to maintain the ability of the system to withstand disturbances and prevent voltage collapse. In general terms, dec reasing reactive power causes voltages to fall, while increasing reactive power causes voltages to rise. A voltage collapse occurs when the system is trying to serve much more load than the voltage can support .

1.4.3 As voltage drops, current must increase to maintain the power supplied,

causing the lines to consume more reactive power an d the voltage to drop further. If current increases too much, transm ission lines trip, or go off-line, overloading other lines and potentially c ausing cascading


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failures. If voltage drops too low, some generators will auto matically disconnect to protect themselves.

1.4.4 Usually the causes of under – voltages are:

• Overloading of supply transformers • Inadequate short circuit level in the point of supp ly • Excessive voltage drop across a long feeder • Poor power factor of the connected load • Remote system faults , while they are being cleared • Interval in re-closing of an auto-reclosure • Starting of large HP induction motors

1.4.5 If the declines continue, these voltage reductions cause additional

elements to trip, leading to further reduction in v oltage and loss of load. The result is a progressive and uncontrollable decl ine in voltage, all because the power system is unable to provide the r eactive power required to supply the reactive power demand.

1.5 Voltage Collapse 1.5.1 When voltages in an area are significantly lo w or blackout occurs due to

the cascading events accompanying voltage instabili ty, the problem is considered to be a voltage collapse phenomenon. Vol tage collapse normally takes place when a power system is heavily loaded and/or has limited reactive power to support the load. The lim iting factor could be the lack of reactive power (SVC and generators hit limi ts) production or the inability to transmit reactive power through the tr ansmission lines.

1.5.2 The main limitation in the transmission lines is the loss of large amounts

of reactive power and also line outages, which limi t the transfer capacity of reactive power through the system.

1.5.3 In the early stages of analysis, voltage coll apse was viewed as a static

problem but it is now considered to be a non linear dynamic phenomenon. The dynamics in power systems involve t he loads, and voltage stability is directly related to the loads. Hence, voltage stability is also referred to as load stability.

1.5.4 There are other factors which also contribute to voltage collapse, and

are as below: • Increase in load • Action of tap changing transformers • Load recovery dynamics


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All these factors play a significant part in voltag e collapse as they effect the transmission, consumption, and generation of re active power.

Usually voltage stability is categorized into two parts

• Large disturbance voltage stability • Small disturbance voltage stability

1.5.5 When a large disturbance occurs, the ability of the system to maintain acceptable voltages falls due to the impact of the disturbance. Ability to maintain voltages is dependent on the system and lo ad characteristics, and the interactions of both the continuous and the discrete controls and protections. Similarly, the ability of the system t o maintain voltages after a small perturbation i.e. incremental change in loa d is referred to as small disturbance voltage stability. It is influenced by the load characteristics, continuous control and discrete controls at a given instant of time.

1.6 Proximity to Instability 1.6.1 Static voltage instability is mainly associat ed with reactive power

imbalance. Thus, the loadability of a bus in a syst em depends on the reactive power support that the bus can receive fro m the system. As the system approaches the maximum loading point or volt age collapse point, both real and reactive power losses increase rapidl y.

Fig 8. Time frames for voltage stability phenomena


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1.6.2 Therefore, the reactive power supports have t o be locally adequate. With

static voltage stability, slowly developing changes in the power system occur that eventually lead to a shortage of reactiv e power and declining voltage.

1.6.3 This phenomenon can be seen from

a plot of power transferred versus voltage at the receiving end. These plots are popularly referred to as P–V curves or ‘Nose’ curves. As power transfer increases, the voltage at the receiving end decreases. In the fig(9) eventually, a critical (nose) point, the point at which the system reactive power is out of usage, is reached where any further increase in active power transfer will lead to very rapid decrease in voltage magnitude.

1.6.4 Before reaching the critical point, a large v oltage drop due to heavy reactive power losses is observed. The only way to save the system from voltage collapse is to reduce the reactive power lo ad or add additional reactive power prior to reaching the point of volta ge collapse.

• These are curves drawn between V and P of a critica l bus at a

constant load power factor. • These are produced by using a series of power flow

solutions for different load levels. • At the knee point or the nose point of the V-P curv e, the

voltage drops rapidly with an increase in the load demand. • Power flow solution fails to converge beyond this l imit which

indicates the instability.

1.7 Reactive Reserve Margin 1.7.1 The amount of unused available capability of reactive power static as well

as dynamic in the system (at peak load for a utilit y system) as a percentage of total capability is known as Reactive reserve margin.

1.7.2 Voltage collapse normally occurs when sources producing reactive

power reach their limits i.e. generators, SVCs or s hunt reactors, and there is not much reactive power to support the load. As reactive power is

Knee point

∆v

Fig 9. PV curve and Voltage stability margin under different conditions


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directly related to voltage collapse, it can be use d as a measure of voltage stability margin.

1.7.3 The voltage stability margin can be defined as a me asure of how close the

system is to voltage instability, and by monitoring the reactive reserves in the power system, proximity to voltage collapse can be monitored.

1.7.4 In case of reactive reserve criteria, the rea ctive power reserve of an

individual or group of VAr sources must be greater than some specified percentage ( x %) of their reactive power output under all conting encies. The precincts where reactive power reserves were ex hausted would be identified as critical areas.

1.7.5 Reactive power requirements over and above th ose which occur naturally

are provided by an appropriate combination of react ive source/devices which are normally classified as static and dynamic devices.

• STATIC SOURCES: Static sources are typically transm ission

and distribution equipments such as Capacitors and Reactors that are relatively static and can respond to the changes in voltage – support requirements only slow ly and in discrete steps. Devices are inexpensive, but the associated switches, control, and communications, a nd their maintenance, can amount to as much as one third of the total operations and maintenance budget of a distribution system.

• DYNAMIC SOURCES: It includes pure reactive power

compensators like synchronous condensers, Synchrono us generators and solid-state devices such as FACTS, S VC, STATCOM, D-VAR, and SuperVAR which are normally dynamic and can respond within cycles to changing r eactive power requirement. These are typically considered a s transmission service devices.

1.7.6 Static devices typically have lower capital c osts than dynamic devices,

and from a system point of view, they are used to p rovide normal or intact-system voltage support and to adapt to slowl y changing conditions, such as daily load cycles and scheduled transactions. By contrast, dynamic reactive power sources must be de ployed to allow the transmission system to respond to rapidly changing conditions on the transmission system, such as sudden loss of generat ors or transmission facilities. An appropriate combination of both stat ic and dynamic resources is needed to ensure reliable operation of the transmission system at an appropriate level of costs .


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1.7.7 Reactive power absorption occurs when current flows through an

inductance. Inductance is found in transmission lin es, transformers, and induction motors etc. The reactive power absorbed b y a transmission line or transformer is proportional to the square of the current.

Sources of Reactive Power Sinks of Reactive Power

Static: � Shunt Capacitors � Filter banks � Under ground cables � Transmission lines (lightly

loaded) � Fuel cells � PV systems

Dynamic: � Synchronous Generators � Synchronous Condensers � FACTS (e.g.,SVC,STATCOM)

� Transmission lines (Heavily loaded)

� Transformers � Shunt Reactors � Synchronous machines � FACTS (e.g.,SVC,STATCOM) � Induction generators (wind

plants) � Loads • Induction motors (Pumps,

Fans etc) • Inductive loads (Arc furnace

etc)

1.7.8 A transmission line also has capacitance. Whe n a small amount of

current is flowing, the capacitance dominates, and the lines have a net capacitive effect which raises voltage. This happen s at night when current flows/Load is low. During the day, when cur rent flow/load is high, inductive effect is greater than the capacitance, a nd the voltage sags.

Fig 10. Average cost of Reactive power technologies

Table 1. Reactive power compensation sources


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1.8 NER GRID – Overview

1.8.1 NER grid with a maximum peak requirement of a round 1800 MW and installed capacity of 2189 MW caters to the seven n orth eastern states. It is synchronously connected with NEW GRID through 400 kV D/C BONGAIGAON – NEW SILIGURI, 220 kV D/C BIRPARA – SAL AKATI and internationally through 132 kV SALAKATI – GELYPHU(Bhutan). The bottle neck of operating the NER grid arises because of th e brittle back bone network of about 6964 Ckt Kms of 132 KV lines, 1595 Ckt Kms of 400 KV lines and 2704 Ckt Kms of 220 KV lines compared to other regional grids.

1.8.2 Almost 50% of the total NER load is spread ou t in 132 kV pocket of

southern part of NER which were without the direct support of major EHV trunk lines. This part of the network is highly sen sitive and is susceptible to grid disturbance and demands more operational ac umen. Increase in the loading of major 132 kV trunk lines, in particu lar 132 kV DIMAPUR – IMPHAL S/C,132 kV JIRIBAM – LOKTAK S/C and 132 kV BADARPUR – KHLIEHRIAT S/C in peak hours has led to many a grid incidents in the past in the form of cascade tripping accompanied by voltage sag.

Fig 11. NER Grid map


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1.8.3 NER system has been strengthened With the com missioning of 400 kV

Pallatana – Silchar D/C, 400/220 kV 315 MVA ICT at Misa, 400/132 kV 2x200 MVA ICT at Silchar, 400/132 kV 125 MVA ICT at Pala tana, 132 kV Silchar – Badapur D/C, 132 kV Silchar – Srikona D/C, 132 kV Palatana – Udaipur D/C, 132 kV Palatana – Surajmani nagar D/C; Bus rea ctors at 400 kV Balipara(80 MVAR), 400 kV Silchar(2x63 MVAR), 400 k V Palatana(80 MVAR); Line reactors at 400 kV Silchar end(2x50 MVA R), 400 kV Pallatana end(2x63 MVAR) and Myntdu-Leshka (2x42 MW) MeECL Hy dro plant. With the availability of greater options, grid operation has been smooth and grid parameters were maintained within the prescrib e IEGC limits.

1.8.4 Relationship between frequency and voltage is a well known fact. Studies

have revealed that though voltage is a localized fa ctor, it is directly affected by the frequency which is a notional facto r. Any lopsidedness in the demand/generation side leading to fluctuations in NEW grid frequency affects NER grid immensely, in particular the volta ge profile of the grid, leading to sagging and swelling of voltage heavily during such occasions. Ironically, NER was synchronously connected with NE W grid for stretching the transmission capability to reduce th e load – generation mismatch of the country.

1.8.5 NER grid also do not have the luxury of solid state FACT devices such as

FSC’s or TCSC’s as the whole transmission system is still in the nascent stage and without much capacity up gradation. It is needed to be seen how far the +/-800 KV HVDC project in NER which is in the execution stage will help in maintaining a healthy voltage pr ofile in the region with its reactive reserve support in the form of filters and capacitor banks.

1.8.6 Presently NER Grid is supported by 1758 MVAr from shunt reactors and

273 MVAr from shunt capacitors spread across the re gion.

1.8.7 Skewness in the location of hydro stations an d load centers in NER is another obstacle which aggravates the voltage probl em further. Lines are long and pass through difficult terrains to the loa d centers. Northern part of NER grid which is well supported by some strong 400 KV and 220 KV network faces high voltage regime during lean hydro period as the corridor is not fully utilized and is usually light ly loaded. Supports from hydro stations in condenser mode are not available for containing low voltage conditions. D curve optimization is yet to be realized fully due to technical glitches.

1.8.8 Reactive power management and voltage control are two aspects of a

single activity that both supports reliability and facilitates commercial transaction across transmission network. Controllin g reactive power flow can reduce losses and congestion on the transmissio n system.


Page 19 of 100

1.8.9 Operationally in NER, Voltage is normally con trolled by managing

production and absorption of reactive power in real time :

• Switching in and out of Line reactance compensators such as capacitors and shunt reactors (Line/Bus Reactors ) as and when system demands in co-operation with the consti tuents and the CTU.

• Circuit switching: Mostly one circuit of the lightl y loaded d/c line is kept open keeping in mind the n-1 criterion during high voltage and high frequency period. Voltage dif ferences as well as fault level of stations are taken into a ccount before any switching operation of circuits. Fault level of major substation in NER are as below :

Sr. no. Bus Name Fault

MVA 1 Balipara 400 kV 3876 2 Ranganadi 400 kV 3650 3 Bongaigaon 400 kV 3605 4 Misa 220 kV 3469 5 Misa 400 kV 3256 6 Samaguri 220 kV 3221 7 Kopili 220 kV 2746 8 Sarusajai 220 kV 2557 9 Salakati 220 kV 2546

10 Mariani 220 kV 1641 11 Dimapur 220 kV 1613 12 Kahelipara 132 kV 1578 13 Agartala 132 kV 863 14 R C Nagar 132 kV 861 15 Kumarghat 132 kV 647

• The generating units provide the basic means of vol tage

control: The automatic voltage regulators (AVR) con trol field excitation to maintain the scheduled voltage levels at the terminals of the generators. In real time operation , connected generation should never be on reactive generation o r absorption limits.

• By generation re-dispatch/rescheduling. • Regulating voltage with the help of OLTC’s. • By load staggering/shedding.

Table 2. Fault level at important Sub -Stations of NER


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1.9 Reliability Improvement Due to Local Voltage Regu lation

1.9.1 Local voltage regulation to a voltage schedul e supplied by the utility can

have a very beneficial effect on overall system rel iability, reducing the problems caused by voltage dips on distribution cir cuits such as dimming lights, slowing or stalling motors, dropout of contactors and solenoids, and shrinking television pictures.

1.9.2 In past years a voltage drop would inherently reduce load, helping the

situation. Light bulbs would dim and motors would s low down with decreasing voltage. Dimmer lights and slower motors typically draw less power, so the situation was in a certain sense self -correcting. With modern loads, this situation is changing.

1.9.3 Today many incandescent bulbs are being repla ced with compact

fluorescent lights, LED lamps that draw constant po wer as voltage decreases, and motors are being powered with adjust able-speed drives that maintain a constant speed as voltage decreases . In addition, voltage control standards are rather unspecific, and there is a tremendous opportunity for an improvement in efficiency and re liability from better voltage regulation. Capacitors supply reactive powe r to boost voltage, but their effect is dramatically diminished as voltage dips.

1.9.4 Capacitor effectiveness is proportional to t he square of the voltage, so at

80% voltage, capacitors are only 64% as effective a s they are at normal conditions. As voltage continues to drop, the capac itor effect falls off until voltage collapses. The reactive power supplie d by an inverter is dynamic, it can be controlled very rapidly, and it does not drop off with a decrease in voltage. Distribution systems that allo w customers to supply dynamic reactive power to regulate voltage could be a tremendous asset to system reliability and efficiency by expanding t he margin to voltage collapse.


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2 TRANSMISSION LINES AND REACTIVE POWER COMPENSATION

2.1 Introduction 2.1.1 In moving power from generators to loads, the transmission network

introduces both real and reactive losses. Housekeep ing loads at substations (such as security lighting and space co nditioning) and transformer excitation losses are roughly constant (i.e., independent of the power flows on the transmission system). Transm ission-line losses, on the other hand, depend strongly on the amount of power being transmitted.

2.1.2 Real-power losses arise because aluminum and copper (the materials

most often used for transmission lines) are not per fect conductors; they have resistance. The consumption of reactive power by transmission lines increases with the square of current i.e., th e transmission of reactive power requires an additional demand for reactive po wer in the system components.

2.1.3 The reactive-power nature of transmission lin es is associated with the

geometry of the conductors themselves (primarily th e radius of the conductor) and the geometry of the conductor config uration (the distances between each conductor and ground and the distances among conductors).

2.1.4 The reactive-power behavior of transmission l ines is complicated by their

inductive and capacitive characteristics. At low li ne loadings, the capacitive effect dominates, and generators and tra nsmission-related reactive equipment must absorb reactive power to ma intain line voltages within their appropriate limits. On the other hand, at high line loadings, the inductive effect dominates, and generators, cap acitors, and other reactive devices must produce reactive power

2.1.5 The thermal limit is the loading point (in MV A) above which real power

losses in the equipment will overheat and damage th e equipment. Most transmission elements (e.g., conductors and transfo rmers) have normal thermal limits below which the equipment can operat e indefinitely without any damage. These types of equipment also have one or more emergency limits to which the equipment can be loaded for sev eral hours with minimal reduction in the life of the equipment .


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2.1.6 If uncompensated, these line losses reduce th e amount of real power that

can be transmitted from generators to loads. Transm ission-line capacity decreases as the line length increases if there is no voltage su pport (injection or absorption of reactive power) on the line. At short distances, the line’s capacity is limited by thermal considera tions; at intermediate distances the limits are related to voltage drop; a nd beyond roughly 300 to 350 miles, stability limits dominate.

2.2 Surge Impedance Loading (SIL) 2.2.1 Transmission lines and cables generate and co nsume reactive power at

the same time. The reactive power generation is alm ost constant, because the voltage of the line is usually constant , and the line’s reactive power consumption depends on the current or load co nnected to the line that is variable. So at the heavy load conditions t ransmission lines consume reactive power, decreasing the line voltage , and in the low load conditions – generate, increasing line voltage.

2.2.2 The case when line’s reactive power produced by the line capacitance is

equal to the reactive power consumed by the line in ductance is called natural loading or surge impedance loading (SIL) , meaning that the line provides exactly the amount of MVAr needed to suppo rt its voltage. The balance point at which the inductive and capacitive effects cancel each other is typically about 40% of the line’s thermal capacity. Lines loaded above SIL consume reactive power, while lines loade d below SIL supply reactive power.

2.2.3 A 400 kV, line generates approximately 55 MVA R per 100 km/Ckt, when it

is idle charged due to line charging susceptance. T his implies a 300 km line generates about 165 MVAR when it is idle charg ed.

2.3 Shunt Compensation in Line 2.3.1 Normally there are two types of shunt reactor s – Line reactor and bus

reactor. Line reactor’s functionality is to avoid t he switching and load rejection over voltages where as Bus reactors are u sed to avoid the steady state over voltage during light load conditi ons.

2.3.2 The degree of compensation is decided by an e conomic point of view

between the capitalized cost of compensator and the capitalized cost of reactive power from supply system over a period of time. In practice a compensator such as a bank of capacitors (or induct ors) can be divided into parallel sections, each Switched separately, s o that discrete changes


Page 23 of 100

in the compensating reactive power may be made, acc ording to the requirements of the load.

2.3.3 Reasons for the application of shunt capacito r units are :

• Increase voltage level at the load • Improves voltage regulation if the capacitor units are

properly switched. • Reduces I2R power loss in the system because of red uction

in current. • Increases power factor of the source generator. • Decrease kVA loading on the source generators and c ircuits

to relieve an overloaded condition or release capac ity for additional load growth.

• By reducing kVA loading on the source generators ad ditional kilowatt loading may be placed on the generation if turbine capacity is available.

2.4 Line loading as function of Line Length and Compens ation 2.4.1 The operating limits

for transmission lines may be taken as minimum of thermal rating of conductors and the maximum permissible line loadings derived from St. Clair’s curve. SIL given in table above is for uncompensated line. If k is the compensation then:

• For a shunt compensated line:

SIL modified =SIL x √ (1-k) • For a series

compensated line: SIL modified=SIL/ √ (1- k)

Further to take into account the line length one ne eds to multiple the

modified SIL with the multiplying factor derived from St. Clair's curve.The derived steady state limit for a line wou ld be = SIL modified x factor from St. Clair's curve.

Fig 12. SIL VS Compensation


Page 24 of 100


Page 25 of 100

LIST-1: 400 KV LINE DETAILS OF NORTH EASTERN REGION SR. NO. FROM TO UTILITY KM CKT CONDUCTOR

1 BONGAIGAON BALIPARA POWERGRID 289.8 1 ACSR MOOSE 2 BONGAIGAON BALIPARA POWERGRID 289.8 2 ACSR MOOSE 3 BALIPARA RANAGANADI POWERGRID 166.3 1 ACSR MOOSE 4 BALIPARA RANAGANADI POWERGRID 166.3 2 ACSR MOOSE

5 BALIPARA MISA POWERGRID 95.4 1 ACSR MOOSE/AACSR

6 BALIPARA MISA POWERGRID 95.4 2 ACSR MOOSE/AACSR

7 BONGAIGAON BINAGURI(ER) POWERGRID 218.0 1 TWIN MO OSE 8 BONGAIGAON BINAGURI(ER) POWERGRID 218.0 2 TWIN MO OSE 9 PALLATANA SILCHAR NETCL 246 1 ACSR MOOSE 10 PALLATANA SILCHAR NETCL 246 2 ACSR MOOSE

LIST-2: 400 KV LINE (CHARGED AT 220 KV) DETAILS OF NORTH EASTERN REGION SR. NO. FROM TO UTILITY KM CKT CONDUCTOR

1 MISA KATHALGURI POWERGRID 382.8 1 ACSR MOOSE 2 MARIANI KATHALGURI POWERGRID 162.9 1 TWIN MOOSE 3 MISA MARIANI POWERGRID 220.0 1 TWIN MOOSE

LIST-3: 220 KV LINE DETAILS OF NORTH EASTERN REGION SR. NO. FROM TO UTILITY KM CKT CONDUCTOR

1 AGIA BTPS AEGCL 67.0 1 SINGLE ZEBRA 2 AGIA SARUSAJAI AEGCL 131.0 1 SINGLE ZEBRA 3 BOKO SARUSAJAI AEGCL 65.0 1 SINGLE ZEBRA 4 BOKO AGIA AEGCL 70.0 1 SINGLE ZEBRA 5 SARUSAJAI LANGPI AEGCL 108.0 1 SINGLE ZEBRA 6 SARUSAJAI LANGPI AEGCL 108.0 2 SINGLE ZEBRA 7 SARUSAJAI SAMAGURI AEGCL 124.0 1 SINGLE ZEBRA 8 SARUSAJAI SAMAGURI AEGCL 124.0 2 SINGLE ZEBRA 9 SAMAGURI MARIANI AEGCL 164.0 1 SINGLE ZEBRA

10 DEOMALI KATHALGURI ARUNACHAL PRADESH 19.0 1 SINGLE ZEBRA

11 BONGAIGAON SALAKATI POWERGRID 10.0 1 SINGLE ZEBRA

12 SALAKATI BIRPARA (ER) POWERGRID 160.0 1 SINGLE ZEBRA

13 SALAKATI BIRPARA (ER) POWERGRID 160.0 2 SINGLE ZEBRA

14 BALIPARA SAMAGURI AEGCL 55.0 1 SINGLE ZEBRA 15 SALAKATI BTPS AEGCL 2.7 1 ACSR ZEBRA


Page 26 of 100

16 SALAKATI BTPS POWERGRID 2.7 2 ACSR ZEBRA 17 SAMAGURI MISA POWERGRID 34.4 1 ACSR ZEBRA 18 SAMAGURI MISA POWERGRID 34.4 2 ACSR ZEBRA 19 MISA DIMAPUR POWERGRID 121.9 1 ACSR ZEBRA 20 MISA DIMAPUR POWERGRID 121.9 2 ACSR ZEBRA 21 MISA KOPILI POWERGRID 72.8 1 ACSR ZEBRA 22 MISA KOPILI POWERGRID 72.8 2 ACSR ZEBRA 23 MISA KOPILI POWERGRID 75.9 3 AAAC ZEBRA 24 MISA BYRNIHAT MeECL 115.0 1 SINGLE ZEBRA 25 MISA BYRNIHAT MeECL 115.0 2 SINGLE ZEBRA 26 KATHALGURI TINSUKIA AEGCL 22.0 1 SINGLE ZEBRA 27 KATHALGURI TINSUKIA AEGCL 22.0 2 SINGLE ZEBRA 28 NTPS TINSUKIA AEGCL 40.0 1 SINGLE ZEBRA 29 NTPS TINSUKIA AEGCL 40.0 2 SINGLE ZEBRA

LIST-4: 132 KV LINE DETAILS OF POWERGRID IN NORTH E ASTERN REGION SR. NO. FROM TO UTILITY KM CKT CONDUCTOR

1 SALAKATI GELYPHU (BHUTAN) POWERGRID 49.2 1 ACSR PANTHER

2 NIRJULI RANGANADI POWERGRID 22.3 1 ACSR PANTHER 3 NIRJULI GOHPUR POWERGRID 42.5 1 ACSR PANTHER 4 RANGANADI ZIRO POWERGRID 44.5 1 AAAC

5 KHLEIHRIAT MeECL KHLEIHRIAT POWERGRID 5.5 1 ACSR PANTHER

6 KHLEIHRIAT KHANDONG POWERGRID 42.5 1 ACSR PANTHE R 7 KHLEIHRIAT KHANDONG POWERGRID 40.9 2 AAAC 8 KHANDONG HAFLONG POWERGRID 64.0 1 ACSR PANTHER 9 HAFLONG JIRIBAM POWERGRID 100.0 1 ACSR PANTHER

10 KHLEIHRIAT BADARPUR POWERGRID 76.6 1 AAAC 11 BADARPUR JIRIBAM POWERGRID 67.2 1 AAAC 12 JIRIBAM AIZWAL POWERGRID 170.0 1 ACSR PANTHER 13 AIZWAL KOLASIB POWERGRID 66.1 1 AAAC 14 KOLASIB BADARPUR POWERGRID 172.3 1 AAAC 15 BADARPUR KUMARGHAT POWERGRID 118.5 1 AAAC 16 KUMARGHAT AIZWAL POWERGRID 131.0 1 ACSR PANTHER 17 PANCHGRAM BADARPUR POWERGRID 1.0 1 AAAC 18 KUMARGHAT R C NAGAR POWERGRID 104.0 1 AAAC 19 BADARPUR PANCHGRAM POWERGRID 1.0 1 AAAC 20 AIZWAL ZEMABAWK POWERGRID 7.0 1 ACSR PANTHER 21 JIRIBAM LOKTAK POWERGRID 82.4 2 ACSR PANTHER 22 LOKTAK IMPHAL POWERGRID 35.0 1 PANTHER

23 IMPHAL IMPHAL (MANIPUR) POWERGRID 1.5 1 PANTHER

24 IMPHAL DIMAPUR POWERGRID 168.9 1 ACSR PANTHER 25 DIMAPUR DOYANG POWERGRID 92.5 1 ACSR PANTHER 26 DIMAPUR DOYANG POWERGRID 92.5 2 ACSR PANTHER


Page 27 of 100

27 R C NAGAR AGARTALA POWERGRID 8.4 1 ACSR PANTHER

28 R C NAGAR AGARTALA POWERGRID 8.4 2 ACSR PANTHER

29 KHANDONG KOPILI POWERGRID 10.9 1 ACSR PANTHER

30 KHANDONG KOPILI POWERGRID 10.9 2 ACSR PANTHER

31 SILCHAR BADARPUR POWERGRID 19 1 AAAC

32 SILCHAR BADARPUR POWERGRID 19 2 AAAC

33 SILCHAR SRIKONA POWERGRID 1 1 AAAC

34 SILCHAR SRIKONA POWERGRID 1 2 AAAC

35 PALLATANA SURAJMANI NGR POWERGRID 37 1 AAAC

36 PALLATANA SURAJMANI NGR POWERGRID 37 2 AAAC

37 PALLATANA UDAIPUR POWERGRID 6 1 AAAC

38 PALLATANA UDAIPUR POWERGRID 6 2 AAAC

LIST-5: 132 KV LINE DETAILS OF NEEPCO IN NORTH EAST ERN REGION SR. NO. FROM TO UTILITY KM CKT CONDUCTOR

1 BALIPARA KHUPI NEEPCO 67.2 1 PANTHER 2 KHUPI KIMI NEEPCO 8.0 1 PANTHER

LIST-6: 132 KV LINE DETAILS OF AEGCL IN NORTH EASTE RN REGION

SR. NO. FROM TO UTILITY KM CKT CONDUCTOR

1 GOSAIGAON DHALIGAON AEGCL 65.0 1 PANTHER 2 GOSAIGAON GAURIPUR AEGCL 62.0 1 PANTHER 3 DHALIGAON BTPS AEGCL 22.0 1 PANTHER 4 DHALIGAON BTPS AEGCL 22.0 2 PANTHER 5 DHALIGAON NALBARI AEGCL 106.0 1 PANTHER 6 NALBARI RANGIA AEGCL 22.0 1 PANTHER 7 DHALIGAON BORNAGAR AEGCL 41.0 1 PANTHER

8 DHALIGAON ASHOK PAPER MILL AEGCL 37.0 1 PANTHER

9 BORNAGAR RANGIA AEGCL 86.0 1 PANTHER 10 RANGIA SISUGRAM AEGCL 33.0 1 PANTHER 11 RANGIA SIPAJHAR AEGCL 38.0 1 PANTHER 12 SIPAJHAR ROWTA AEGCL 44.0 1 PANTHER 13 SISUGRAM KAHELIPARA AEGCL 12.0 1 PANTHER 14 RANGIA KAHELIPARA AEGCL 46.0 1 PANTHER 15 KAHELIPARA NARENGI AEGCL 12.0 1 PANTHER 16 KAHELIPARA SARUSAJAI AEGCL 4.0 1 PANTHER 17 KAHELIPARA SARUSAJAI AEGCL 4.0 2 PANTHER 18 KAHELIPARA SARUSAJAI AEGCL 4.0 3 PANTHER 19 KAHELIPARA SARUSAJAI AEGCL 4.0 4 PANTHER 20 KAHELIPARA DISPUR AEGCL 3.0 1 PANTHER 21 NARENGI CTPS AEGCL 20.0 1 PANTHER


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LIST-7: 132 KV LINE DETAILS OF MANIPUR IN NORTH EAS TERN REGION SR. NO. FROM TO UTILITY KM CKT CONDUCTOR

1 LOKTAK NINGTHOUKONG MANIPUR 20.0 1 PANTHER 2 NINGTHOUKONG CHURACHANDPUR MANIPUR 23.0 1 PANTHER 3 NINGTHOUKONG CHURACHANDPUR MANIPUR 23.0 2 PANTHER

22 DISPUR CTPS AEGCL 29.0 1 PANTHER 23 CTPS JAGIROAD AEGCL 35.0 1 PANTHER 24 RANGIA ROWTA AEGCL 108.0 1 PANTHER 25 ROWTA DEPOTA AEGCL 72.0 1 PANTHER 26 ROWTA DEPOTA AEGCL 64.0 2 PANTHER 27 DEPOTA B CHARIALI AEGCL 57.0 1 PANTHER 28 DEPOTA SAMAGURI AEGCL 45.0 1 PANTHER 29 SAMAGURI SANKARDEV NGR AEGCL 61.0 1 PANTHER 30 DIPHU SANKARDEV NGR AEGCL 72.0 1 PANTHER 31 B CHARIALI GOHPUR AEGCL 51.0 1 PANTHER 32 GOHPUR N LAKHIMPUR AEGCL 77.0 1 PANTHER 33 GOHPUR N LAKHIMPUR AEGCL 77.0 1 PANTHER 34 N LAKHIMPUR DHEMAJI AEGCL 63.0 1 PANTHER 35 TINSUKIA LEDO AEGCL 53.0 1 PANTHER 36 TINSUKIA DIBRUGARH AEGCL 53.0 1 PANTHER 37 DHALIGAON BRPL AEGCL 1.0 1 PANTHER 38 DIBRUGARH MORAN AEGCL 36.0 1 PANTHER 39 MORAN LTPS AEGCL 39.0 1 PANTHER 40 LTPS NTPS AEGCL 60.0 1 PANTHER 41 LTPS NTPS AEGCL 60.0 2 PANTHER 42 TINSUKIA NTPS AEGCL 43.0 1 PANTHER 43 LTPS NAZIRA AEGCL 22.0 1 PANTHER 44 LTPS NAZIRA AEGCL 22.0 2 PANTHER 45 LTPS MARIANI AEGCL 80.0 1 PANTHER 46 NAZIRA SIBSAGAR AEGCL 13.0 1 PANTHER 47 SRIKONA PAILAPOOL AEGCL 35.0 1 PANTHER 48 MARIANI JORHAT AEGCL 20.0 1 PANTHER 49 MARIANI JORHAT AEGCL 20.0 2 PANTHER 50 JORHAT BOKAKHAT AEGCL 89.0 1 PANTHER 51 MOKOKCHUNG MARIANI AEGCL 19.0 1 PANTHER 52 MARIANI GOLAGHAT AEGCL 45.0 1 PANTHER 53 GOLAGHAT BOKAJAN AEGCL 65.0 1 PANTHER 54 BOKAJAN DIMAPUR AEGCL 5.0 1 PANTHER 55 BALIPARA DEPOTA AEGCL 28.0 1 ACSR PANTHER 56 PANCHGRAM SRIKONA AEGCL 19.0 1 PANTHER 57 PANCHGRAM SILCHAR AEGCL 30.0 1 PANTHER 58 SILCHAR DULLAVCHERRA AEGCL 50.0 1 PANTHER 59 JIRIBAM PAILAPOOL AEGCL 15.0 1 PANTHER 60 BALIPARA GOHPUR AEGCL 106.0 1 SINGLE ZEBRA 61 HAFLONG HAFLONG AEGCL 1.0 1 PANTHER 62 JAGIROAD HPC AEGCL 5.0 1 PANTHER


Page 29 of 100

4 CHURACHANDPUR KAKCHING MANIPUR 38.0 1 PANTHER 5 KAKCHING KONGBA MANIPUR 45.0 1 PANTHER 6 KONGBA YAINGANGPOKPI MANIPUR 33.0 1 PANTHER 7 YAINGANGPOKPI IMPHAL MANIPUR MANIPUR 42.0 1 PANTH ER 8 NINGTHOUKONG IMPHAL MANIPUR MANIPUR 28.0 1 PANTHE R 9 IMPHAL MANIPUR KARONG MANIPUR 60.0 1 PANTHER 10 LOKTAK RENGPANG MANIPUR 42.0 1 PANTHER 11 RENGPANG JIRIBAM MANIPUR 40.4 1 PANTHER

LIST-8: 132 KV LINE DETAILS OF TSECL IN NORTH

LIST-9: 132 KV LINE DETAILS OF NAGALAND IN NORTH EA STERN REGION


1 P K BARI KAILASHOR TSECL 18.0 1 PANTHER 2 P K BARI KUMARGHAT TSECL 1.0 1 PANTHER 3 P K BARI AMBASA TSECL 45.0 1 PANTHER 4 AGARTALA BODHJ NGR TSECL 8.0 1 PANTHER 5 BARAMURA GAMAITILLA TSECL 14.0 1 PANTHER 6 P K BARI KAMALPUR TSECL 31.0 1 PANTHER 7 KAMALPUR DHALABIL TSECL 32.0 1 PANTHER 8 DHALABIL AGARTALA TSECL 45.0 1 PANTHER 9 AGARTALA ROKHIA TSECL 35.0 1 PANTHER 10 AGARTALA ROKHIA TSECL 35.0 2 PANTHER 11 P K BARI DHARMA NAGAR TSECL 35.0 1 PANTHER 12 BODHJ NGR JIRANIA TSECL 7.0 1 PANTHER 13 JIRANIA BARAMURA TSECL 15.0 1 PANTHER 14 GAMAITILLA AMBASA TSECL 25.0 1 PANTHER 15 ROKHIA UDAIPUR TSECL 40.0 1 PANTHER


1 KOHIMA MELURI NAGALAND 74 1 PANTHER 2 MELURI KIPHIRI NAGALAND 42 1 PANTHER 3 KOHIMA DIMAPUR (PGCIL) NAGALAND 58 1 PANTHER 4 KOHIMA WOKHA NAGALAND 58 1 PANTHER 5 WOKHA DOYANG NAGALAND 13 1 PANTHER 6 DOYANG MOKOKCHUNG NAGALAND 30 1 PANTHER 7 DIMAPUR DIMAPUR (PGCIL) NAGALAND 1 1 PANTHER 8 DIMAPUR DIMAPUR (PGCIL) NAGALAND 1 2 PANTHER


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LIST-10: 132 KV LINE DETAILS OF MIZORAM IN NORTH EA STERN REGION SR. NO. FROM TO UTILITY KM CKT CONDUCTOR

1 ZUANGTUI SAITUAL MIZORAM 50.0 1 PANTHER 2 SERCHIP ZUANGTUI MIZORAM 54.0 1 PANTHER 3 LUNGLEI SERCHIP MIZORAM 69.0 1 PANTHER

4 AIZWAL LUANGMUAL MIZORAM 6.7 1 ACSR PANTHER

5 BHAIRABI KOLASIB MIZORAM 30.0 1 PANTHER

LIST-11: 132 KV LINE DETAILS OF MeECL IN NORTH EAST ERN REGION


1 UMIUM ST IV UMIUM ST III MeECL 8.0 1 PANTHER 2 UMIUM ST IV UMIUM ST III MeECL 8.0 2 PANTHER 3 UMTRU UMIUM ST III MeECL 41.2 1 PANTHER 4 UMTRU UMIUM ST III MeECL 41.2 2 PANTHER 5 UMTRU UMIUM ST IV MeECL 37.6 1 PANTHER 6 UMTRU UMIUM ST IV MeECL 37.6 2 PANTHER 7 UMTRU EPIP II MeECL 0.7 1 PANTHER 8 UMTRU EPIP II MeECL 0.7 2 PANTHER 9 EPIP II EPIP I MeECL 2.5 1 PANTHER

10 EPIP II EPIP I MeECL 2.5 2 PANTHER 11 EPIP II KILLING MeECL 10.0 1 PANTHER 12 EPIP II KILLING MeECL 10.0 2 PANTHER 13 UMIUM ST III UMIUM ST I MeECL 17.5 1 PANTHER 14 UMIUM ST III UMIUM ST I MeECL 17.5 2 PANTHER 15 UMIUM ST I UMIUM ST II MeECL 3.0 1 PANTHER 16 UMIUM ST I MAWLAI MeECL 12.0 1 PANTHER 17 UMIUM ST I UMIUM MeECL 5.0 1 PANTHER 18 MAWLAI CHEERAPUNJI MeECL 41.0 1 PANTHER 19 MAWLAI NONGSTOIN MeECL 71.3 1 PANTHER 20 NONGSTOIN NANGALBIBRA MeECL 56.0 1 PANTHER 21 NANGALBIBRA TURA MeECL 68.7 1 PANTHER 22 UMIUM NEHU MeECL 7.0 1 PANTHER 23 MAWLAI NEHU MeECL 9.2 1 PANTHER 24 NEHU NEIGHRIMS MeECL 7.0 1 PANTHER

25 NEHU KHLEIHRIAT MeECL MeECL 52.6 1 PANTHER

26 NEIGHRIMS KHLEIHRIAT MeECL MeECL 64.8 1 PANTHER

27 KHLEIHRIAT MeECL LUMSHNONG MeECL 24.0 1 PANTHER


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LIST-12: 132 KV LINE DETAILS OF AP IN NORTH EASTERN REGION SR. NO. FROM TO UTILITY KM CKT CONDUCTOR

1 ZIRO DAPORIJO AP 87.2 1 PANTHER

2 DAPORIJO ALONG AP 81.7 1 PANTHER

LIST-13: 66 KV LINE DETAILS OF NORTH EASTERN REGION


1 MARIANI GOLAGHAT AEGCL 40.0 1 WOLF 2 MARIANI GOLAGHAT AEGCL 40.0 2 WOLF 3 MARIANI NAZIRA AEGCL 54.0 1 WOLF 4 MARIANI NAZIRA AEGCL 54.0 2 WOLF 5 NAZIRA NTPS AEGCL 74.0 1 WOLF 6 NAZIRA NTPS AEGCL 74.0 2 WOLF 7 GOLAGHAT BOKAJAN AEGCL 64.0 1 WOLF 8 GOLAGHAT BOKAJAN AEGCL 64.0 2 WOLF 9 BOKAJAN DIPHU AEGCL 39.0 1 WOLF 10 TINSUKIA RUPAI AEGCL 25.0 1 WOLF 11 AGIA LAKHIPUR AEGCL 34.0 1 WOLF 12 TINSUKIA NTPS AEGCL 36.0 1 WOLF 13 TINSUKIA NTPS AEGCL 36.0 2 WOLF 14 FCI NTPS AEGCL 3.0 1 WOLF 15 FCI NTPS AEGCL 3.0 2 WOLF

28 KHLEIHRIAT MeECL LESHKA MeECL 26.0 1 PANTHER

29 KHLEIHRIAT MeECL LESHKA MeECL 26.0 2 PANTHER

30 KHLEIHRIAT MeECL KHLEIHRIAT MeECL 5.0 2 ACSR P ANTHER

31 UMIUM ST I MAWNGAP MeECL 33 1 ACSR PANTHER 32 UMIUM ST I MAWNGAP MeECL 33 2 ACSR PANTHER 33 EPIP II TRISHUL MeECL 0.2 1 ACSR PANTHER 34 EPIP II NALARI MeECL 0.2 1 ACSR PANTHER 35 EPIP I SHYAM CENTURY MeECL 0.15 1 ACSR PANTHER 36 EPIP I MAITHAN MeECL 0.2 1 ACSR PANTHER 37 EPIP I SAI PRAKASH MeECL 4.0 1 ACSR PANTHER 38 EPIP I GREYSTONE MeECL 0.7 1 ACSR PANTHER 39 LUMSHNONG CMCL MeECL 0.16 1 ACSR PANTHER 40 LUMSHNONG MCL MeECL 3.0 1 ACSR PANTHER

41 LUMSHNONG ADHUNIK CEMENT

MeECL 8.0 1 ACSR PANTHER

42 LUMSHNONG HILL CEMENT MeECL 8.0 1 ACSR PANTHER 43 LUMSHNONG JUD CEMENT MeECL 2.0 1 ACSR PANTHER 44 LUMSHNONG GVIL CEMENT MeECL 2.0 1 ACSR PANTHER


Page 32 of 100

16 DULLAVCHERRA PATHARKANDI AEGCL .... 1 WOLF 17 PATHARKANDI ADAMTILLA AEGCL .... 1 WOLF

18 DIMAPUR POWER HOUSE NAGALAND 4.0 1 WOLF

19 POWER HOUSE DAIRY FARM NAGALAND 5.0 1 WOLF 20 NITO FARM DAIRY FARM NAGALAND 12.0 1 WOLF 21 DIMAPUR SINGRIJAN NAGALAND 5.4 1 WOLF 22 DIMAPUR SINGRIJAN NAGALAND 5.4 2 WOLF

23 SINGRIJAN GANESH NAGAR NAGALAND 21.4 1 WOLF

24 SINGRIJAN CHUMUKIDIMA NAGALAND 7.9 1 WOLF 25 MOKOKCHUNG ZUNHEBOTO NAGALAND 46.0 1 WOLF 26 MOKOKCHUNG TULI NAGALAND 56.3 1 WOLF 27 TULI NAGINIMORA NAGALAND 33.0 1 WOLF 28 NAGINIMORA TIZIT NAGALAND 44.0 1 WOLF 29 TIZIT MON NAGALAND 31.0 1 WOLF 30 MOKOKCHUNG TUENSANG NAGALAND 50.4 1 WOLF 31 TUENSANG KHIPHIRE NAGALAND 55.7 1 WOLF 32 KHIPHIRE LIKHIMRO NAGALAND 35.0 1 WOLF 33 KHIPHIRE LIKHIMRO NAGALAND 35.0 2 WOLF

34 ROKHIA RABINDRA NAGAR TSECL 23.0 1 WOLF

35 RABINDRA NAGAR BELONIA TSECL 38.0 1 WOLF

36 BELONIA BAGAFA TSECL 15.0 1 WOLF 37 BAGAFA SATCHAND TSECL 36.0 1 WOLF 38 SATCHAND SABROOM TSECL 15.0 1 WOLF 39 BAGAFA UDAIPUR TSECL 29.0 1 WOLF 40 UDAIPUR GOKULNAGAR TSECL 31.0 1 WOLF 41 GUMTI UDAIPUR TSECL 45.0 1 WOLF 42 GOKULNAGAR BADARGHAT TSECL 12.0 1 WOLF 43 BADARGHAT ROKHIA TSECL 24.0 1 WOLF 44 BADARGHAT AGARTALA TSECL 8.0 1 WOLF 45 AMARPUR GUMTI TSECL 30.0 1 WOLF 46 TELIAMURA AMARPUR TSECL 35.0 1 WOLF 47 BARAMURA TELIAMURA TSECL 8.0 1 WOLF 48 KOLASIB VAIRENGTE MIZORAM 35.0 1 WOLF

LIST-14: SHUNT COMPENSATED LINES IN NORTH EASTERN REGION

SR. NO. FROM TO UTILITY KM CKT

SENDING END LINE REACTOR

RECEIVING END LINE REACTOR

1 RANGANADI BALIPARA POWERGRID 166.3 1 50 50 2 RANGANADI BALIPARA POWERGRID 166.3 2 50 50 3 BONGAIGAON BALIPARA POWERGRID 289.9 1 50 63 4 BONGAIGAON BALIPARA POWERGRID 289.9 2 50 63


Page 33 of 100

5 MISA KATHALGURI POWERGRID 382.9 1 50 NIL 6 MISA MARIANI POWERGRID 220 1 50 NIL

7 PALLATANA SILCHAR NETCL 247 1 63 50

8 PALLATANA SILCHAR NETCL 247 2 63 50

LIST-15: SHUNT COMPENSATED INTER – REGIONAL LINES IN NORTH EASTERN REGION

SR. NO. FROM TO UTILITY KM CKT

SENDING END LINE REACTOR

RECEIVING END LINE REACTOR

1 BONGAIGAON BINAGURI (ER) POWERGRID 218 1 63 NIL

2 BONGAIGAON BINAGURI (ER) POWERGRID 218 2 63 NIL


Page 34 of 100

LIST-16: INTER-STATE LINE DETAILS OF NORTH EASTERN REGION SR. NO.

CONNECTING STATES OWNED BY FROM TO KV KM CKTS CONDUCTOR

POWERGRID RANGANADI BALIPARA 400 166.3 D/C TWIN MOO SE ARUNACHAL PRADESH DEOMALI KATHALGURI 220 19.0 S/C Z EBRA

NEEPCO KHUPI BALIPARA 132 67.2 S/C PANTHER 1 ARUNACHAL -

ASSAM POWERGRID NIRJULI GOHPUR 132 42.5 S/C PANTHER POWERGRID BADARPUR KHLIEHRIET 132 76.6 S/C PANTHER POWERGRID KHANDONG KHLIEHRIET 132 42.5 D/C PANTHER

AEGCL & MeECL PANCHGRAM LUMSHNONG 132 23.4 S/C PANT HER AEGCL & MeECL SARASUJAI UMTRU 132 37.0 D/C PANTHER

2 ASSAM - MEGHALAYA

AEGCL & MeECL KAHILIPARA UMTRU 132 9.0 D/C PANTHER POWERGRID MISA DIMAPUR 220 123.5 D/C ZEBRA

AEGCL & NAGALAND MARIANI MOKOKCHUNG 132 50.0 S/C PA NTHER AEGCL BOKAJAN DIMAPUR 132 5.0 S/C PANTHER

ASSAM - NAGALAND

AEGCL & NAGALAND BOKAJAN DIMAPUR 66 8.0 S/C WOLF

AEGCL & TRIPURA DULLAVCHERRA DHARMANAGAR 132 29.0 S /C PANTHER

3

ASSAM - TRIPURA

POWERGRID BADARPUR KUMARAGHAT 132 118.5 S/C PANTHER POWERGRID BADARPUR JIRIBAM 132 67.2 S/C PANTHER POWERGRID HAFLONG JIRIBAM 132 100.6 S/C PANTHER 4 ASSAM -

MANIPUR AEGCL PAILAPOOL JIRIBAM 132 15.0 S/C PANTHER

5 ASSAM - MIZORAM POWERGRID BADARPUR KOLASIB 132 107.2 S/C PANTHER

6 MIZORAM - MANIPUR POWERGRID AIZWAL JIRIBAM 132 172.3 S/C PANTHER

7 MIZORAM - TRIPURA POWERGRID AIZWAL KUMARAGHAT 132 131.0 S/C PANTHER

POWERGRID DIMAPUR IMPHAL 132 168.9 S/C PANTHER 8 NAGALAND - MANIPUR MANIPUR & NAGALAND KOHIMA KARONG 132 50.0 S/C PANTH ER


Page 35 of 100

LIST-17: FIXED, SWITCHABLE AND CONVERTIBLE LINE RE ACTORS IN NORTH EASTERN REGION.

PROVISION TO USE AS B/R SR. NO. UTILITY FROM TO INSTALLED

AT (STATION) KV MVAR KM SWITCHABLE CONVERTIBLE

FIXED

1 POWERGRID RANGANADI BALIPARA RANGANADI 400 50 166 .3 .... …. TRUE 2 POWERGRID RANGANADI BALIPARA RANGANADI 400 50 166 .3 .... …. TRUE 3 POWERGRID RANGANADI BALIPARA BALIPARA 400 50 166. 3 TRUE …. .... 4 POWERGRID RANGANADI BALIPARA BALIPARA 400 50 166. 3 TRUE …. .... 5 POWERGRID BONGAIGAON BALIPARA BONGAIGAON 400 50 289.9 .... .... TRUE 6 POWERGRID BONGAIGAON BALIPARA BONGAIGAON 400 50 289.9 .... .... TRUE 7 POWERGRID BONGAIGAON BALIPARA BALIPARA 400 63 289 .9 .... .... TRUE 8 POWERGRID BONGAIGAON BALIPARA BALIPARA 400 63 289 .9 .... .... TRUE 9 POWERGRID BALIPARA MISA MISA 400 50 95.4 .... …. TRUE 10 POWERGRID MISA KATHALGURI MISA 220 50 382.9 .... .... TRUE 11 POWERGRID MISA MARIANI MISA 220 50 220.0 .... …. TRUE 12 POWERGRID BONGAIGAON BINAGURI(ER) BONGAIGAON 400 63 218.0 .... .... TRUE 13 POWERGRID BONGAIGAON BINAGURI(ER) BONGAIGAON 400 63 218.0 .... .... TRUE 14 POWERGRID PALLATANA SILCHAR SILCHAR 400 50 247 T RUE …. …. 15 POWERGRID PALLATANA SILCHAR SILCHAR 400 50 247 T RUE …. …. 16 POWERGRID PALLATANA SILCHAR PALLATANA 400 63 247 …. …. …. 17 POWERGRID PALLATANA SILCHAR PALLATANA 400 63 247 …. …. ….

NOTE: SWITCHABLE: LINE REACTORS WHICH CAN BE OPERATED ON LINE AS A BUS REACTOR. CONVERTIBLE: LINE REACTORS WHICH CAN BE OPERATED U PON ONLY WHEN LINE IS IN OUT CONDITION. FIXED : LINE REACTORS WHICH ARE FIXE D AND CANNOT BE OPERATED UPON AS A BUS REACTOR


Page 36 of 100

LIST-18: BUS REACTORS IN NORTH EASTERN REGION

RATING SR. NO. UTILITY INSTALLED AT

(STATION) KV MVAR MAKE

STATUS

1 POWERGRID BALIPARA 400 50 BHEL IN SERVICE 2 POWERGRID BALIPARA 400 80 BHEL IN SERVICE 3 POWERGRID BONGAIGAON 400 2 X 50 BHEL IN SERVICE 4 POWERGRID MISA 400 50 BHEL IN SERVICE 5 POWERGRID SILCHAR 400 2 X 63 CGL IN SERVICE 7 OTPC PALATANA 400 80 BHEL IN SERVICE 8 ASSAM MARIANI 220 2 X 12.5 .... IN SERVICE 9 ASSAM SAMAGURI 220 2 X 12.5 .... IN SERVICE 10 POWERGRID AIZWAL 132 20 .... IN SERVICE 11 POWERGRID KUMARGHAT 132 20 .... IN SERVICE 12 TRIPURA DHARMANAGAR 132 2 X 2 .... IN SERVICE

LIST-19: TERTIARY REACTORS ON 33 KV SIDE OF 400/22 0/33 KV ICTS IN NORTH EASTERN REGION

RATING SR. NO. UTILITY INSTALLED

AT (STATION) INSTALLED

ON MVAR MAKE STATUS

1 POWERGRID BALIPARA 33 KV SIDE OF ICT I 4 X 25 BHEL IN SERVICE

2 POWERGRID BONGAIGAON 33 KV SIDE OF ICT I 2 X 25 BHEL IN SERVICE

3 POWERGRID MISA 33 KV SIDE OF ICT I 4 X 25 BHEL IN SERVICE


Page 37 of 100

3 SERIES AND SHUNT CAPACITOR VOLTAGE CONTROL

3.1 INTRODUCTION 3.1.1 Capacitors aid in minimizing operating expenses and allow the utilities to

serve new loads and consumers with a minimum system investment. Series and shunt capacitors in a power system gener ate reactive power to improve power factor and voltage, thereby enhancing the system capacity and reducing the losses.

3.1.2 In series capacitors the reactive power is pr oportional to the square of the

load current, thus generating reactive power when i t is most needed whereas in shunt capacitors it is proportional to t he square of the voltage. Series capacitors compensation is usually applied f or long transmission lines and transient stability improvement. Series c ompensation reduces net transmission line inductive reactance. The reac tive generation I2XC compensates for the reactive consumption I2X of the transmission line. This is a self-regulating nature of series capacito rs. At light loads series capacitors have little effect.

3.1.3 There are certain

unfavorable aspects of series capacitors. Generally the cost of installing series capacitors is higher than that of a corresponding installation of a shunt capacitor.

3.1.4 This is because the

protective equipment for a series capacitor is often more complicated. The factors which influence the choice between the shunt and series capacitors are summarized in Table 3.

Table 4. Equipment preference


Page 38 of 100

3.1.5 Due to various limitations in the use of seri es capacitors, shunt

capacitors are widely used in distribution systems. For the same voltage improvement, the rating of a shunt capacitor will b e higher than that of a series capacitor. Thus a series capacitor stiffens the system, which is especially beneficial for starting large motors fro m an otherwise weak power system, for reducing light flicker caused by large fluctuating load, etc.

3.2 MeSEB CAPACITY BUILDING AND TRAINING DOCUMENT SUGGEST (Sub title as given in the PFC document for corporatization of MeSEB):

3.2.1 Installation of Shunt-capacitors:

Installation of capacitors is a low cost process fo r reduction of technical losses. The agricultural load mainly consists of ir rigation pump motors. The PF of pump motors are generally below 0.6, whic h means the total reactive power demand of the system is high. The re active power demand can be reduced by installation of suitable capacito rs. However, proper maintenance has to be adopted to keep the system in order. In view of the maintenance problem, reactive compensation techniqu e could be installed at the distribution transformer centers. Care has to be taken that it does not lead to over voltage problems during th e off peak hours. To avoid this there should be switch off arrangement i n the capacitor bank. The optimum allocation of LT capacitors at distribu tion substation by minimizing a cost function, which includes loss cos t in the beneficiary system and the annual cost of the capacitor bank. T he reactive compensation can also be carried out at the primary distribution feeders (11 KV) lines. The optimum number, size and locatio n of online capacitors will depend on the following factors:

• Type of load. • Quantum of load. • Load factor. • Annual load cycle. • Power factor.

3.3 AS PER THE ASSAM GAZETTE, EXTRAORDINARY, FEBRUARY 10, 2005

IN CHAPTER 9: FREQUENCY AND VOLTAGE MANAGEMENT Sec 9.1 (d) System voltages levels can be affected by Regional operation. The SLDC shall optimise voltage management by adjus ting transformer


Page 39 of 100

taps to the extent available and switching of circu its/ capacitors/ reactors and other operational steps. SLDC will instruct gen erating stations to regulate MVAr generation within their declared para meters. SLDC shall also instruct Distribution Licensees to regulate de mand, if necessary.

LIST-20: SUBSTATIONS IN NER

AGENCY 400KV 220 KV 132 KV & 66 KV TOTAL POWER GRID 4 2 9 15 ARUNACHAL

PRADESH NIL 1 6 7

AEGCL NIL 6 22 28

MANIPUR NIL NIL 6 6

MeECL NIL NIL 9 9

MIZORAM NIL NIL 4 4

NAGALAND NIL NIL 5 5

TSECL NIL NIL 9 9

OTPC 1 NIL NIL 1

TOTAL 5 9 70 84


Page 40 of 100

LIST-21: SHUNT CAPACITOR DETAILS OF NORTH EASTERN R EGION

SR. NO. UTILITY SUBSTATION INSTALLED ON CAPACITY (MVAR)

1 MeECL MAWLAI 132 KV BUS BAR 12.5 2 MeECL EPIP I 132 KV BUS BAR 20 3 MeECL EPIP II 132 KV BUS BAR 20 4 MeECL EPIP II 33 KV BUS BAR 15 5 MeECL EPIP II 33 KV BUS BAR 15 6 AEGCL BAGHJAB 33 KV BUS BAR 2X5 7 AEGCL KAHELIPARA 33 KV BUS BAR 3X5 8 AEGCL BARNAGAR 33 KV BUS BAR 2X5 9 AEGCL GOSAIGAON 33 KV BUS BAR 1X5 10 AEGCL GAURIPUR 33 KV BUS BAR 1X10 11 AEGCL RANGIA 33 KV BUS BAR 2X10 12 AEGCL MARGHERITA 33 KV BUS BAR 2X5 13 AEGCL N LAKHIMPUR 33 KV BUS BAR 1X5 14 AEGCL DULLAVCHERRA 33 KV BUS BAR 1X5 15 AEGCL DEPOTA 33 KV BUS BAR 2X5 16 AEGCL SARUSAJAI 33 KV BUS BAR 2X10 17 AEGCL ROWTA 33 KV BUS BAR 2X5 18 AEGCL DIPHU 33 KV BUS BAR 2X5 19 AEGCL DIBRUGARH 33 KV BUS BAR 2X10

20 AEGCL SHANKARDEV NAGAR 33 KV BUS BAR 2X5

21 AEGCL RUPAI 33 KV BUS BAR 2X5 22 AEGCL SRIKONA 33 KV BUS BAR 2X5

Total Capacity of NER

273


Page 41 of 100

4 TRANSFORMER LOAD TAP CHANGER AND VOLTAGE CONTROL

4.1 INTRODUCTION 4.1.1 Transformers provide the capability to raise alternating-current

generation voltages to levels that make long-distan ce power transfers practical and then lowering voltages back to levels that can be distributed and used. The ratio of the number of turns in the p rimary to the number of turns in the secondary coil determines the ratio of the primary voltage to the secondary voltage. By tapping the primary or se condary coil at various points, the ratio between the primary and s econdary voltage can be adjusted. Transformer taps can be either fixed o r adjustable under load through the use of a load-tap changer (LTC). T ap capability is selected for each application during transformer de sign.

4.1.2 The OLTC alters the power

transformer turns ratio in a number of pre defined steps and in that way changes the secondary side voltage.

4.1.3 Each step usually represents

a change in LV side no-load voltage of approximately 0.5-1.7%. Standard tap changers offer between ± 9 to ± 17 steps (i.e. 19 to 35 positions). The automatic voltage regulator (AVR) is designed to control a power transformer with a motor driven on-load tap-changer.

4.1.4 Typically the AVR regulates voltage at the se condary side of the power transformer. The control method is based on a step- by-step principle which means that a control pulse, one at a time, will be issued to the on-load tap-changer mechanism to move it up or down by one position.

4.1.5 The pulse is generated by the AVR whenever th e measured voltage, for a

given time, deviates from the set reference value b y more than the preset dead band (i.e. degree of insensitivity). Time dela y is used to avoid

Fig 13. Switching principle of LTC


Page 42 of 100

unnecessary operation during short voltage deviatio ns from the pre-set value.

4.1.6 Transformer-tap changers can be used for volt age control, but the control

differs from that provided by reactive sources. Tra nsformer taps can force voltage up (or down) on one side of a transfo rmer, but it is at the expense of reducing (or raising) the voltage on the other side. The reactive power required to raise (or lower) voltage on a bus is forced to flow through the transformer from the bus on the ot her side.

4.1.7 The reactive power consumption of a transform er at rated current is

within the range 0.05 to 0.2 p.u. based on the tran sformer ratings. Fixed taps are useful when compensating for load growth a nd other long-term shifts in system use. LTCs are used for more-rapid adjustments, such as compensating for the voltage fluctuations associate d with the daily load cycle. While LTCs could potentially provide rapid v oltage control, their performance is normally intentionally degraded. Wit h an LTC, tap changing is accomplished by opening and closing con tacts within the transformer’s tap changing mechanism.

4.2 AS PER THE ASSAM GAZETTE, EXTRAORDINARY, FEBRUARY 10, 2005 IN CHAPTER 9: FREQUENCY AND VOLTAGE MANAGEMENT Sec 9.1(d) System voltages levels can be affected b y Regional operation. The SLDC shall optimise voltage management by adjus ting transformer taps to the extent available and switching of circu its/ capacitors/ reactors and other operational steps. SLDC will instruct gen erating stations to regulate MVAr generation within their declared para meters. SLDC shall also instruct Distribution Licensees to regulate de mand, if necessary .


Page 43 of 100

LIST-22: ICT DETAILS OF POWERGRID IN NORTH EASTERN REGION

LIST-23: ICT DETAILS OF NEEPCO IN NORTH EASTERN REG ION

STEP SL. NO. SUBSTATION AGENCY ICT

NO. MVA KV RATIO MAKE TT NT

%AGE KV PT

1 RHEP NEEPCO 01 7.5 132/33 KV …. …. …. …. …. 02

2 RHEP NEEPCO 02 7.5 132/33 KV …. …. …. …. …. 03

3 BALIPARA NEEPCO 01 50 220/132 KV …. …. …. …. …. 09

4 KOPILI NEEPCO 01 60 220/132 KV …. …. …. …. …. 09

5 RHEP NEEPCO 01 360 400/132 KV …. …. …. …. …. 10



%AGE KV PT

1 BALIPARA POWERGRID 01 315 400/220 /33 kV TELK 17 9 1.25 5 10

2 BONGAIGAON POWERGRID 01 315 400/220 /33 kV TELK 17 9 1.25 5 12

3 SILCHAR POWERGRID 01 200 400/132 kV CGL 17 9 1.25 5 9B

4 SILCHAR POWERGRID 01 200 400/132 kV CGL 17 9 1.25 5 9B

5 MISA POWERGRID 01 315 400/220 /33 kV TELK 17 9 1.25 5 05

6 MISA POWERGRID 02 315 400/220 kV CGL 17 9 1.25 5 05

7 DIMAPUR POWERGRID 01 100 220/132 kV TELK 17 13 1.25 2.75 12

8 DIMAPUR POWERGRID 02 100 220/132 kV ALSTOM 17 13 1.25 2.75 12

9 NIRJULI POWERGRID 01 10 132 /33 kV

KANOHAR ELECT. 17 9 1.25 1.65 09

10 NIRJULI POWERGRID 01 10 132 /33 kV BBL 5 3 1.25 1.65 03

11 SALAKATI POWERGRID 01 50 220/132 kV NGEF 17 13 1.25 2.75 16

12 SALAKATI POWERGRID 02 50 220/132 kV EMCO 17 13 1.25 2.75 16

13 ZIRO POWERGRID 01 15 132 /33 kV

AREVA /ALSTOM 17 9 1.25 1.65 02

14 KOPILI POWERGRID 01 160 220/132 KV …. …. …. …. …. 13


Page 44 of 100

6 RHEP NEEPCO 02 360 400/132 KV …. …. …. …. …. 09

LIST-24: ICT DETAILS OF NHPC IN NORTH EASTERN REGIO N

STEP SL.

NO. SUBSTATION AGENCY ICT NO. MVA KV

RATIO MAKE TT NT %AGE KV

PT

1 LOKTAK NHPC 01 5 132/33 KV …. …. …. …. …. 02

LIST-25: ICT DETAILS OF ARUNACHAL PRADESH IN NORTH EASTERN REGION

LIST-26: ICT DETAILS OF AEGCL IN NORTH EASTERN REGI ON

STEP SL.



PT

1 AGIA AEGCL 01 50 220/132 KV …. …. …. …. …. 14

2 AGIA AEGCL 01 16 132/33 KV …. …. …. …. …. 05

3 AGIA AEGCL 01 12.5 132/33 KV …. …. …. …. …. 05

4 ASHOK PAPER MILL AEGCL 01 12.5 132/33

KV …. …. …. …. …. 05

5 ASHOK PAPER MILL AEGCL 01 16 132/33

KV …. …. …. …. …. 05

6 BAGHJHAP AEGCL 01 16 132/33 KV …. …. …. …. …. 05

7 BAGHJHAP AEGCL 02 16 132/33 KV …. …. …. …. …. 05



%AGE KV PT

1 ALONG ARUNACHAL PRADESH 01 15 132/33

KV …. …. …. …. …. 03

2 DAPORIJO ARUNACHAL PRADESH 01 5 132/33

KV …. …. …. …. …. 02

3 DAPORIJO ARUNACHAL PRADESH 02 5 132/33

KV …. …. …. …. …. 02

4 DEOMALI ARUNACHAL PRADESH 01 100 220/

132 kV …. …. …. …. …. 09

5 DEOMALI ARUNACHAL PRADESH 01 16 132/33

KV …. …. …. …. …. 04

6 LEKHI ARUNACHAL PRADESH 01 15 132/33

KV …. …. …. …. …. 05

7 LEKHI ARUNACHAL PRADESH 01 20 132/33

KV …. …. …. …. …. 05


Page 45 of 100

8 BALIPARA AEGCL 01 50 220 /132 kV …. …. …. …. …. 09

9 BOKO AEGCL 01 10 220/132 KV …. …. …. …. …. 05

10 BOKO AEGCL 02 10 220/132 KV …. …. …. …. …. 05

11 B CHARIALI AEGCL 01 16 132/33 KV …. …. …. …. …. 17

12 B CHARIALI AEGCL 02 16 132/33 KV …. …. …. …. …. 17

13 BORNAGAR AEGCL 01 25 132/33 KV …. …. …. …. …. ….

14 BORNAGAR AEGCL 02 25 132/33 KV …. …. …. …. …. ….

15 BOKAKHAT AEGCL 01 16 132/33 KV …. …. …. …. …. ….

16 BOKAKHAT AEGCL 02 16 132/33 KV …. …. …. …. …. ….

17 BOKAJAN AEGCL 01 16 132/33 KV …. …. …. …. …. ….

18 BTPS AEGCL 01 10 132/33 KV …. …. …. …. …. ….

19 BTPS AEGCL 02 10 132/33 KV …. …. …. …. …. ….

20 BTPS AEGCL 01 80 220/132 kV …. …. …. …. …. ….

21 BTPS AEGCL 02 80 220/132 kV …. …. …. …. …. ….

22 BTPS AEGCL 03 160 220/132 kV …. …. …. …. …. ….

23 CTPS AEGCL 01 16 132/33 KV …. …. …. …. …. ….

24 CTPS AEGCL 01 30 132/33 KV …. …. …. …. …. ….

25 DEPOTA AEGCL 01 31.5 132/33 KV …. …. …. …. …. 05

26 DEPOTA AEGCL 02 31.5 132/33 KV …. …. …. …. …. 05

27 DHALIGAON AEGCL 01 25 132/33 KV …. …. …. …. …. ….

28 DHALIGAON AEGCL 02 25 132/33 KV …. …. …. …. …. ….

29 DHEMAJI AEGCL 01 16 132/33 KV …. …. …. …. …. ….

30 DIPHU AEGCL 01 16 132/66 KV …. …. …. …. …. ….

31 DIPHU AEGCL 02 16 132/66 KV …. …. …. …. …. ….

32 DIBRUGARH AEGCL 01 31.5 132/33 KV …. …. …. …. …. 08

33 DIBRUGARH AEGCL 01 20 132/33 KV …. …. …. …. …. 08

34 DIBRUGARH AEGCL 02 20 132/33 KV …. …. …. …. …. 08


Page 46 of 100

35 DISPUR AEGCL 01 16 132/33 KV …. …. …. …. …. ….

36 DISPUR AEGCL 02 16 132/33 KV …. …. …. …. …. ….

37 DULLAVCHERRA AEGCL 01 3.5 132/33 KV …. …. …. …. …. ….






43 GAURIPUR AEGCL 01 10 132/33 KV …. …. …. …. …. ….

44 GAURIPUR AEGCL 02 10 132/33 KV …. …. …. …. …. ….

45 GOHPUR AEGCL 01 16 132/33 KV …. …. …. …. …. 05

46 GOHPUR AEGCL 01 10 132/33 KV …. …. …. …. …. 03

47 GOSSAIGAON AEGCL 01 16 132/33 KV …. …. …. …. …. ….

48 GOLAGHAT AEGCL 01 25 132/33 KV …. …. …. …. …. ….

49 GOLAGHAT AEGCL 02 25 132/33 KV …. …. …. …. …. ….

50 HAFLONG AEGCL 01 10 132/33 KV …. …. …. …. …. 05

51 HAFLONG AEGCL 02 10 132/33 KV …. …. …. …. …. 05

52 JORHAT AEGCL 01 25 132/33 KV …. …. …. …. …. ….

53 JORHAT AEGCL 01 16 132/33 KV …. …. …. …. …. ….

54 KAHELIPARA AEGCL 01 30 132/33 KV …. …. …. …. …. 05



57 KAHELIPARA AEGCL 01 10 132/33/11 KV …. …. …. …. …. 02

58 KAHELIPARA AEGCL 02 10 132/33/11 KV …. …. …. …. …. 02

59 LEDO AEGCL 01 10 132/33 KV …. …. …. …. …. 06

60 LEDO AEGCL 02 10 132/33 KV …. …. …. …. …. 06

61 LTPS AEGCL 01 7.5 132/33 KV …. …. …. …. …. ….

62 LTPS AEGCL 02 7.5 132/33 KV …. …. …. …. …. ….


Page 47 of 100

63 MAJULI AEGCL 01 5.5 132/33 KV …. …. …. …. …. ….

64 MARIANI AEGCL 01 20 132/66 KV …. …. …. …. …. 06

65 MARIANI AEGCL 02 20 132/66 KV …. …. …. …. …. 06

66 MARIANI AEGCL 01 100 220/132 kV …. …. …. …. …. 13

67 MARIANI AEGCL 02 100 220/132 kV …. …. …. …. …. 13

68 MORAN AEGCL 01 16 132/33 KV …. …. …. …. …. ….

69 MORAN AEGCL 02 16 132/33 KV …. …. …. …. …. ….

70 NALBARI AEGCL 01 16 132/33 KV …. …. …. …. …. ….

71 NALBARI AEGCL 02 16 132/33 KV …. …. …. …. …. ….

72 NALKATA (NORTH

LAKHIMPUR) AEGCL 01 10 132/33

KV …. …. …. …. …. ….

73 NALKATA (NORTH

LAKHIMPUR) AEGCL 02 10 132/33

KV …. …. …. …. …. ….

74 NARENGI AEGCL 01 25 132/33 KV …. …. …. …. …. ….

75 NARENGI AEGCL 02 25 132/33 KV …. …. …. …. …. ….

76 NAZIRA AEGCL 01 25 132/33 KV …. …. …. …. …. 06

77 NTPS AEGCL 01 25 132/66 KV …. …. …. …. …. ….

78 NTPS AEGCL 02 25 132/66 KV …. …. …. …. …. ….

79 PAILAPOOL AEGCL 01 10 132/33 KV …. …. …. …. …. 05



82 PANCHGRAM AEGCL 01 16 132/33 KV …. …. …. …. …. 08




86 PAVOI AEGCL 01 16 132/33 KV …. …. …. …. …. ….

87 PAVOI AEGCL 02 16 132/33 KV …. …. …. …. …. ….

88 RANGIA AEGCL 01 25 132/33 KV …. …. …. …. …. 03

89 RANGIA AEGCL 02 25 132/33 KV …. …. …. …. …. 03


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90 ROWTA AEGCL 01 25 132/33 KV …. …. …. …. …. 03

91 ROWTA AEGCL 02 25 132/33 KV …. …. …. …. …. 03

92 S NAGAR AEGCL 01 16 132/33 KV …. …. …. …. …. 04

93 S NAGAR AEGCL 02 16 132/33 KV …. …. …. …. …. 05

94 SAMAGURI AEGCL 01 50 220/132 kV …. …. …. …. …. 12



97 SAMAGURI AEGCL 01 25 132/33 KV …. …. …. …. …. 06

98 SAMAGURI AEGCL 02 25 132/33 KV …. …. …. …. …. 06

99 SARUSAJAI AEGCL 01 31.5 132/33 KV …. …. …. …. …. 06

100 SARUSAJAI AEGCL 02 31.5 132/33 KV …. …. …. …. …. 06

101 SARUSAJAI AEGCL 01 100 220/132 KV …. …. …. …. …. 10

102 SARUSAJAI AEGCL 02 100 220/132 kV …. …. …. …. …. 12

103 SARUSAJAI AEGCL 03 100 220/132 kV …. …. …. …. …. 11

104 SISUGRAM AEGCL 01 31.5 132/33 KV …. …. …. …. …. 06

105 SISUGRAM AEGCL 02 31.5 132/33 KV …. …. …. …. …. 06

106 SIBSAGAR AEGCL 01 16 132/33 KV …. …. …. …. …. ….

107 SIBSAGAR AEGCL 02 16 132/33 KV …. …. …. …. …. ….

108 SIPAJHAR AEGCL 01 16 132/33 KV …. …. …. …. …. ….

109 SIPAJHAR AEGCL 02 16 132/33 KV …. …. …. …. …. ….

110 SRIKONA AEGCL 01 25 132/33 KV …. …. …. …. …. 05

111 SRIKONA AEGCL 02 25 132/33 KV …. …. …. …. …. 05

112 TINSUKIA AEGCL 01 20 132/66 KV …. …. …. …. …. 02



115 TINSUKIA AEGCL 01 50 220/132 kV …. …. …. …. …. 16

116 TINSUKIA AEGCL 02 50 220/132 kV …. …. …. …. …. 16


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LIST-27: ICT DETAILS OF MANIPUR IN NORTH EASTERN R EGION



%AGE KV PT

1 CHURACHANDPUR MANIPUR 01 20 132/33 KV …. …. …. …. …. ….

2 IMPHAL MANIPUR 01 20 132/33 KV …. …. …. …. …. ….



5 KAKCHING MANIPUR 01 20 132/33 KV …. …. …. …. …. ….

6 KARONG MANIPUR 01 20 132/33 KV …. …. …. …. …. ….

7 NINGTHOUKHONG MANIPUR 01 12.5 132/33 KV …. …. …. …. …. ….

8 NINGTHOUKHONG MANIPUR 02 12.5 132/33 KV …. …. …. …. …. ….

9 YANGANGPOKPI MANIPUR 01 20 132/33 KV …. …. …. …. …. ….

10 YANGANGPOKPI MANIPUR 02 20 132/33 KV …. …. …. …. …. ….

11 JIRIBAM MANIPUR 01 6.3 132/33 KV …. …. …. …. …. ….

LIST-28: ICT DETAILS OF MEGHALAYA IN NORTH EASTE RN REGION

STEP SL.



PT

1 CHERAPUNJEE MeECL 01 12.5 132/33 KV …. …. …. …. …. 06

2 EPIP I MeECL 01 20 132/33 KV …. …. …. …. …. 03

3 EPIP I MeECL 02 20 132/33 KV …. …. …. …. …. 03

4 EPIP II MeECL 01 50 132/33 KV …. …. …. …. …. 08

5 KHLIEHRIAT MeECL 01 20 132/33 KV …. …. …. …. …. 05

6 KHLIEHRIAT MeECL 02 20 132/33 KV …. …. …. …. …. 06

7 MAWLAI MeECL 01 20 132/33 KV …. …. …. …. …. 04

8 MAWLAI MeECL 02 20 132/33 KV …. …. …. …. …. 08

9 MAWLAI MeECL 01 10 132/33 KV …. …. …. …. …. 03

10 MAWLAI MeECL 01 12.5 132/33 KV …. …. …. …. …. 07

11 NANGALBIBRA MeECL 01 10 132/33 KV …. …. …. …. …. 07


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12 NANGALBIBRA MeECL 01 12.5 132/33 KV …. …. …. …. …. 06

13 NEHU MeECL 01 20 132/33 KV …. …. …. …. …. 06

14 NEHU MeECL 02 20 132/33 KV …. …. …. …. …. 06

15 NEIGRIHMS MeECL 01 10 132/33 KV …. …. …. …. …. 05

16 NEIGRIHMS MeECL 02 10 132/33 KV …. …. …. …. …. 04

17 NONGSTOIN MeECL 01 12.5 132/33 KV …. …. …. …. …. 04

18 UMIUM ST III MeECL 01 10 132/33 KV …. …. …. …. …. 08

19 TURA MeECL 01 20 132/33 KV …. …. …. …. …. 15

20 TURA MeECL 01 15 132/33 KV …. …. …. …. …. 15

21 TURA MeECL 02 15 132/33 KV …. …. …. …. …. 15

22 TURA MeECL 03 15 132/33 KV …. …. …. …. …. 15

23 LUMSHNONG MeECL 01 10 132/33 KV …. …. …. …. …. ….

24 UMTRU MeECL 01 20 132/33 KV …. …. …. …. …. 02

LIST-29: ICT DETAILS OF MIZORAM IN NORTH EASTERN R EGION



%AGE KV PT

1 AIZAWL LUANGMUAL MIZORAM 01 12.5 132/33

KV …. …. …. …. …. 05

2 AIZAWL LUANGMUAL MIZORAM 02 12.5 132/33

KV …. …. …. …. …. 05

3 AIZAWL ZUANGTUI MIZORAM 01 12.5 132/33

KV …. …. …. …. …. 05

4 AIZAWL ZUANGTUI MIZORAM 02 12.5 132/33

KV …. …. …. …. …. 05

5 KOLASIB MIZORAM 01 12.5 132/66 KV …. …. …. …. …. 10

6 KOLASIB MIZORAM 02 12.5 132/66 KV …. …. …. …. …. 09

7 LUNGLEI MIZORAM 01 12.5 132/33 KV …. …. …. …. …. 05

8 LUNGLEI MIZORAM 02 12.5 132/33 KV …. …. …. …. …. 09

9 SERCHHIP MIZORAM 01 12.5 132/33 KV …. …. …. …. …. 02

10 SERCHHIP MIZORAM 02 6.3 132/33 KV …. …. …. …. …. 03

11 SAITUAL MIZORAM 01 6.3 132/33 KV …. …. …. …. …. 06


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LIST-30: ICT DETAILS OF NAGALAND IN NORTH EASTERN REGION



%AGE KV PT

1 DIMAPUR NAGALAND 01 20 132/66 KV …. …. …. …. …. 05



4 KIPHIRE NAGALAND 01 6.5 132/66 KV …. …. …. …. …. 04



7 KOHIMA NAGALAND 01 8 132/33 KV …. …. …. …. …. 03



10 MELURI NAGALAND 01 5 132/33 KV …. …. …. …. …. 01

11 MOKOKCHUNG NAGALAND 01 12.5 132/66 KV …. …. …. …. …. 04

12 MOKOKCHUNG NAGALAND 02 12.5 132/66 KV …. …. …. …. …. 04

13 WOKHA NAGALAND 01 5 132/33 KV …. …. …. …. …. 03

LIST-31: ICT DETAILS OF TSECL IN NORTH EASTERN REG ION

STEP SL.



PT

1 AGARTALA TSECL 01 15 132/66 KV …. …. …. …. …. 09








9 AMBASA TSECL 01 7.5 132/33 KV …. …. …. …. …. 08


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10 AMBASA TSECL 02 7.5 132/33 KV …. …. …. …. …. 08

11 BARAMURA TSECL 01 30 132/66 KV …. …. …. …. …. 05

12 DHALABIL TSECL 01 7.5 132/33 KV …. …. …. …. …. 04

13 DHARMANAGAR TSECL 01 7.5 132/33 KV …. …. …. …. …. 07



16 KAILASHOR TSECL 01 7.5 132/33 KV …. …. …. …. …. 08

17 KAMALPUR TSECL 01 7.5 132/11 KV …. …. …. …. …. 08

18 P K BARI TSECL 01 15 132/33 KV …. …. …. …. …. 05

19 P K BARI TSECL 01 10 132/11 KV …. …. …. …. …. 05

20 ROKHIA TSECL 01 30 132/66 KV …. …. …. …. …. 05

21 UDAIPUR TSECL 01 10 132/66 KV …. …. …. …. …. 05

22 UDAIPUR TSECL 01 15 132/11 KV …. …. …. …. …. 05

LIST-32: ICT DETAILS OF OTPC IN NORTH EASTERN REGI ON



%AGE KV PT

1 PALLATANA OTPC 01 125 400/132 kV BHEL …. …. …. …. ….

LIST-33: TRANSMISSION/TRANSFOMATION/VAR COMPENSATIO N

CAPACITY OF NER

TRANSMISSION LINE (CKT KM) AGENCY 400 KV 220 KV 132 KV

POWERGRID 1595 1312 1964 STATES 0 1392 5000 TOTAL 1595 2704 6964

TRANSFORMATION CAPACITY (MVA) POWERGRID/NEEPCO/OTPC/NHPC 2155/845/125/5 MVA

STATES 4265 MVA REACTIVE COMPENSATION (MVAR)

POWERGRID/NEEPCO/OTPC 1398/100/206 MVAR STATES 54 MVAR

CAPACITIVE COMPENSATION – 273 MVAR


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5 HVDC AND VOLTAGE CONTROL

5.1 INTRODUCTION 5.1.1 Basically for transferring power over a long distance or submarine power

transmission, High voltage DC transmission lines (HVDC) are preferred which transmits power via DC (direct current). They normally consist of two converter terminals connected by a DC transmiss ion line and in some applications, multi-terminal HVDC with interconnect ed DC transmission lines. Back-to-Back DC and HVDC Light are specific types o f HVDC systems. HVDC Light uses new cable and converter te chnologies and is economical at lower power levels than traditional H VDC.

5.2 HVDC CONFIGURATION

5.2.1 Bipolar

In bipolar transmission a pair of conductors is use d, each at a high potential with respect to ground, in opposite polar ity. Since these conductors must be insulated for the full voltage, transmission line cost is higher than a monopole with a return conductor. However, there are a number of advantages to bipolar transmission which can make it the attractive option.

• Under normal load, negligible earth-current flows, as in the case of monopolar transmission with a metallic eart h-return. This reduces earth return loss and environmental ef fects.

• When a fault develops in a line, with earth return electrodes installed at each end of the line, approximately ha lf the rated power can continue to flow using the earth as a ret urn path, operating in monopolar mode.

• Since for a given total power rating each conductor of a bipolar line carries only half the current of monop olar lines, the cost of the second conductor is reduced compare d to a monopolar line of the same rating.

• In very adverse terrain, the second conductor may b e carried on an independent set of transmission towers, so th at some power may continue to be transmitted even if one li ne is damaged.


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A bipolar system may also be installed with a metal lic earth return conductor. Bipolar systems may carry as much as 3,2 00 MW at voltages of +/-600 kV (viz., 2500 MW +/- 500 KV TALCHER – KO LAR HVDC link in INDIA connecting NEW GRID to SR GRID ) Submarine cable installations initially commissioned as a monopole may be upgrade d with additional cables and operated as a bipole.

5.2.2 Back to back

A back-to-back station (or B2B for short) is a plan t in which both static inverters and rectifiers are in the same area, usua lly in the same building. The length of the direct current line is kept as sh ort as possible. HVDC back-to-back stations are used for

• Coupling of electricity mains of different frequenc y (as in INDIA; the interconnection between NEW GRID and SR GRID through 1000 MW HVDC BHADRAVATI and 1000 MW HVDC GAZUWAKA)

• Coupling two networks of the same nominal frequency but no fixed phase relationship (viz., HVDC SASARAM, HV DC VINDHYACHAL).

• Different frequency and phase number (for example, as a replacement for traction current converter plants)

The DC voltage in the intermediate circuit can be s elected freely at HVDC back-to-back stations because of the short conducto r length. The DC voltage is as low as possible, in order to build a small valve hall and to avoid series connections of valves. For this reason at HVDC back-to-back stations valves with the highest available current rating are used.

5.2.3 A high voltage direct current (HVDC) link con sists of a rectifier and an inverter. The rectifier side of the HVDC link is eq uivalent to a load consuming positive real and reactive power and the inverter side of the HVDC link as a generator providing positive real po wer and negative reactive power (i.e. absorbing positive reactive po wer).

5.2.4 Thyristor based HVDC converters always consum e reactive power when

in operation. A DC line itself does not require rea ctive power and voltage drop on the line is only the IR drop where I is the DC current. The converters at the both ends of the line, however, d raw reactive power from the AC system. The reactive power consumption of the HVDC converter/inverter is 50-60 % of the active power converted. It is independent of the length of the line.


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5.2.5 The reactive power requirements of the conver ter and system have to be

met by providing appropriate reactive power in the station. For those reason reactive power compensations devices are use d together with reactive power control from the ac side in the form of filter and capacitor banks.

5.2.6 Both AC and DC harmonics are generated in HVD C converters. AC

harmonics are injected into the AC system and DC ha rmonics are injected into the DC line. These harmonics have the followin g harmful effects:

• Interference in communication system. • Extra power losses in machines and capacitors conne cted in

the system. • Some harmonics may produce resonance in AC circuits

resulting in over voltages. • Instability of converter controls.

5.2.7 Harmonics are normally minimized by using fil ters. The following types of filters are used:

• AC filters. • DC filters. • High frequency filters.

AC Filter

DC Filter

DC FilterAC Filter

DC Filter

DC Filter

Converter Xmers

Valve Halls

-Thyristors

-Firing ckts

-Cooling ckt

Smoothing Reactor

Electrode station

Basic Components of HVDC TerminalBasic Components of HVDC Terminal

400 kV

DC Line

Control Room

-Control & Protection

-Telecommunication

AC PLC

Fig 14. HVDC Fundamental components


Page 56 of 100

AC Filters AC filters are RLC circuits connected between phase and earth. They offer low impedance to harmonic frequencies. Thus, AC harmonic currents are passed to earth. Both tuned and damped filter arrangements are used. The AC harmonic filters also provide reac tive power required for satisfactory operation of converters and also p artly injects reactive power into the system.

DC Filters DC filters are similar to AC filters. A DC filter i s connected between pole bus and neutral bus. It diverts DC harmonics to ear th and prevents them from entering DC lines. Such a filter does not supp ly reactive power as DC line does not require reactive power.

HIGH FREQUENCY FILTERS HVDC converters may produce electrical noise in the carrier frequency band from 20 Khz to 490 Khz. They also generate rad io interference noise in the mega hertz range of frequencies. High freque ncy (PLC-RI) filters are used to minimize noise and interference with PLCC. Such filters are connected between the converter transformer and the station AC bus.

5.3 REACTIVE POWER SOURCE Reactive power is required for satisfactory operati on of converters and also to boost the AC side voltages. AC harmonic fil ters which help in minimizing harmonics also provide reactive power pa rtly. Additional supply may be obtained from shunt (switched) capaci tor banks usually installed in AC side.

5.4 800 KV HVDC BI-POLE The first 800kV HVDC bi-pole line in INDIA has been planned from a pooling substation at Bishwanath Chariali in North- eastern Region to Agra in Northern region. This is being programmed f or commissioning matching with Subansiri Lower HEP in 2013-14. The t ransmission line would be for 6000 MW capacity and HVDC terminal cap acity would be 3000 MW between Bishwanath Chariali and Agra. In th e second phase, for transmission of power from hydro projects at Sikkim and Bhutan pooled at Alipurduar, another 3000 MW terminal modules wou ld be added between Siliguri and Agra. It is envisaged to take- up the proposed 800kV, 6000MW HVDC bi-pole line from Bishwanath Chariali t o Agra under a scheme titled ” Inter-regional Transmission system for power export from NER to NR/WR ” which is under execution.


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6 FACTS AND VOLTAGE CONTROL

6.1 INTRODUCTION 6.1.1 The demands of lower power losses, faster res ponse to system parameter

change, and higher stability of system have stimula ted the development of the Flexible AC Transmission systems (FACTS). Ba sed on the success of research in power electronics switching devices and advanced control technology, FACTS has become the technology of choi ce in voltage control, reactive/active power flow control, transi ent and steady-state stabilization that improves the operation and funct ionality of existing power transmission and distribution system.

6.1.2 The achievement of these studies enlarge the efficiency of the existing

generator units, reduce the overall generation capa city and fuel consumption, and minimize the operation cost. The p ower electronics-based switches in the functional blocks of FACTS ca n usually be operated repeatedly and the switching time is a por tion of a periodic cycle, which is much shorter than the conventional mechanical switches.

6.1.3 The advance of semiconductors increases the s witching frequency and

voltage-ampere ratings of the solid switches and fa cilitates the applications. For example, the switching frequencie s of Insulated Gate Bipolar Transistors (IGBTs) are from 3 kHz to 10 kH z which is several hundred times the utility frequency of power system (50~60Hz). Gate turn-off thyristors (GTOs) have a switching frequency lo wer than 1 kHz, but the voltage and current rating can reach 5-8 kV and 6 k A respectively.

6.2 Static Var Compensator (SVC) 6.2.1 Static Var Compensator is “a shunt-connected static Var generator or

absorber whose output is adjusted to exchange capac itive or inductive current so as to maintain or control specific param eters of the electrical power system (typically bus voltage)” .SVC is based on thyristors without gate turn-off capability.

6.2.2 The operating principal and characteristics of thy ristors realize SVC

variable reactive impedance. SVC includes two main components and their combination: (1) Thyristor-controlled and Thy ristor-switched Reactor (TCR and TSR); and (2) Thyristor-switched c apacitor (TSC). Figure 15 shows the diagram of SVC.


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6.2.3 TCR and TSR are both composed of a shunt-conn ected reactor controlled

by two parallel, reverse-connected thyristors. TCR is controlled with proper firing angle input to operate in a continuou s manner, while TSR is controlled without firing angle control which resul ts in a step change in reactance.

6.2.4 TSC shares similar

composition and same operational mode as TSR, but the reactor is replaced by a capacitor. The reactance can only be either fully connected or fully disconnected zero due to the characteristic of capacitor. With different combinations of TCR/TSR, TSC and fixed capacitors, a SVC can meet various requirements to absorb/supply reactive power from/to the transmission line.

6.3 Converter-based Compensator

6.3.1 Static Synchronous Compensator (STATCOM) is o ne of the key

Converter-based Compensators which are usually base d on the voltage source inverter (VSI) or current source inverter (CSI), as shown in Figure 16 (a). Unlike SVC, STATCOM controls the output current independently of the AC system voltage, while the DC side voltage is automatically maintained to serve as a voltage source. Mostly, STATCOM is designed based on the VSI (VOLTAGE SOURCE INVERTER).

Fig 16. STATCOM topologies: (a) STATCOM based on VSI and CSI (b) STATCOM with storage

Fig 15. Static VAR Compensators (SVC): TCR/TSR, TSC, FC and Mechanically Switched Resistor


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6.3.2 Compared with SVC, the topology of a STATCO M is more complicated.

The switching device of a VSI is usually a gate tur n-off device paralleled by a reverse diode; this function endows the VSI ad vanced controllability.

6.3.3 Various combinations of the switching devices and appropriate topology

make it possible for a STATCOM to vary the AC outpu t voltage in both magnitude and phase. Also, the combination of STATC OM with a different storage device or power source (as shown in Figure 16b) endows the STATCOM the ability to control the real power outpu t.

6.3.4 STATCOM has much better dynamic performance t han conventional

reactive power compensators like SVC. The gate turn -off ability shortens the dynamic response time from several utility peri od cycles to a portion of a period cycle. STATCOM is also much faster in i mproving the transient response than a SVC. This advantage also brings higher reliability and larger operating range.

6.4 Series-connected controllers

6.4.1 As shunt-connected controllers, series- conne cted FACTS controllers can also be divided into either impeda nce type or converter type.

6.4.2 The former includes

Thyristor-Switched Series Capacitor (TSSC), Thyristor-Controlled Series Capacitor (TCSC), Thyristor- Switched Series Reactor, and Thyristor-Controlled Series Reactor.

6.4.3 The latter, based on VSI, is

usually in the Compensator (SSSC). The composition and operation of different types are similar to the operation of the shunt connected peers. Figure shows the diagrams of various series-connected controllers.

Fig 17. Series -connected FACTS controllers: (a) TCSR and TSSR; (b) TSSC; (c) SSSC


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7 GENERATOR REACTIVE POWER AND VOLTAGE CONTROL

7.1 INTRODUCTION 7.1.2 An electric-power generator’s primary functio n is to convert fuel (or other

energy resource) into electric power. Almost all ge nerators also have considerable control over their terminal voltage an d reactive-power output.

7.1.3 The ability of a generator

to provide reactive support depends on its real-power production which is represented in the form of generator capability curve or D - curve. Figure 18 shows the combined limits on real and reactive production for a typical generator. Like most electric equipment, generators are limited by their current-carrying capability. Near rated voltage, this capability becomes an MVA limit for the armature of the generator rather than a MW limitation, shown as the armature heating limit in the Figure.

7.1.4 Production of reactive power involves incre asing the magnetic field to

raise the generator’s terminal voltage. Increasing the magnetic field requires increasing the current in the rotating fie ld winding. This too is current limited, resulting in the field-heating lim it shown in the figure. Absorption of reactive power is limited by the magn etic-flux pattern in the stator, which results in excessive heating of the s tator-end iron, the core-end heating limit. The synchronizing torque is also reduced when absorbing large amounts of reactive power, which ca n also limit

Fig 18. D-Curve of a typical Generator


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generator capability to reduce the chance of losing synchronism with the system.

7.1.5 The generator prime mover (e.g., the steam tu rbine) is usually designed

with less capacity than the electric generator, res ulting in the prime-mover limit in Fig. 18. The designers recognize tha t the generator will be producing reactive power and supporting system volt age most of the time. Providing a prime mover capable of delivering all the mechanical power the generator can convert to electricity when it is neither producing nor absorbing reactive power would result in underutilization of the prime mover.

7.1.6 To produce or absorb additional VARs beyond t hese limits would require

a reduction in the real-power output of the unit. Capacitors supply reactive power and have leading power factors, whil e inductors consume reactive power and have lagging power factors. The convention for generators is the reverse. When the generator is su pplying reactive power, it has a lagging power factor and its mode o f operation is referred to as overexcited. When a generator consumes reacti ve power, it has a leading power factor region and is under excited.

7.1.7 Control over the reactive output and the term inal voltage of the generator

is provided by adjusting the DC current in the gene rator’s rotating field. Control can be automatic, continuous, and fast. The inherent characteristics of the generator help maintain syst em voltage.

7.1.8 At any given field setting, the generator has a specific terminal voltage it

is attempting to hold. If the system voltage declin es, the generator will inject reactive power into the power system, tendin g to raise system voltage. If the system voltage rises, the reactive output of the generator will drop, and ultimately reactive power will flow into the generator, tending to lower system voltage.

7.1.9 The voltage regulator will accentuate this be havior by driving the field

current in the appropriate direction to obtain the desired system voltage. Because most of the reactive limits are thermal lim its associated with large pieces of equipment, significant short-term e xtra reactive-power capability usually exists. Power-system stabilizers also control generator field current and reactive-power output in response to oscillations on the power system. This function is a part of the networ k-stability ancillary service.


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7.2 SYNCHRONOUS CONDENSERS

7.2.1 Every synchronous machine (motor or generator ) has the reactive power

capability. Synchronous motors are occasionally use d to provide voltage support to the power system as they provide mechani cal power to their load. Some combustion turbines and hydro units are designed to allow the generator to operate without its mechanical pow er source simply to provide the reactive-power capability to the power system when the real power generation is unavailable or not needed.

7.2.2 Synchronous machines that are designed exclus ively to provide reactive

support are called synchronous condensers. Synchron ous condensers have all of the response speed and controllability advantages of generators without the need to construct the rest o f the power plant (e.g., fuel-handling equipment and boilers). Because they are rotating machines with moving parts and auxiliary systems, they may r equire significantly more maintenance than static alternatives. They als o consume real power equal to about 3% of the machine’s reactive-power r ating. That is, a 50-MVAR synchronous condenser requires about 1.5 MW of real power.

7.2.3 As per planning philosophy and general guidelines i n the Manual on

Transmission planning criteria issued by CEA (MOP, India), Thermal / Nuclear Generating Units shall normally not run at leading power factor. However for the purpose of charging unit may be all owed to operate at leading power factor as per the respective capabili ty curve.

7.2.4 Generator capability may depend significantly on the type and amount of

cooling. This is particularly true of hydrogen cool ed generators where cooling gas pressure affects both the real and reac tive power capability

Table 5. List of units in NER required to be normal ly operated with free governor action and AVR in service.

SL. NO. STATION UTILITY UNIT NO. UNIT

CAPACITY (MW)

TYPE

1 KOPILI HEP NEEPCO 1,2,3 & 4* 50 HYDEL

2 RANGANADI HEP NEEPCO 1,2 & 3 135 HYDEL

*Units running in 132 KV pocket is exempt from FGMO.


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1. LTPS UNIT 5, 6 & 7 CAPABILITY CURVE


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2. NTPS UNIT 1, 2 & 3 CAPABILITY CURVE


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3. NTPS UNIT 4 CAPABILITY CURVE


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4. NTPS UNIT 6 CAPABILITY CURVE


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5. LTPS CAPABILITY CURVE


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6. NTPS CAPABILITY CURVE


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7. UMIUM ST I CAPABILITY CURVE


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8. UMIUM STAGE II CAPABILITY CURVE


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9. UMIUM STAGE III CAPABILITY CURVE


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10. UMIUM STAGE IV CAPABILITY CURVE


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11. AGBPP UNIT 5, 6, 7, 8 & 9 CAPABILITY CURVE


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12. AGBPP UNIT 1, 2, 3 & 4 CAPABILITY CURVE


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13. AGTPP CAPABILITY CURVE


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14. DOYANG HEP UNIT 1 CAPABILITY CURVE


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15. KHANDONG HEP UNIT 2 CAPABILITY CURVE


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16. KOPILI HEP UNIT 1 CAPABILITY CURVE


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17. KOPILI HEP UNIT 2 CAPABILITY CURVE


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18. KOPILI HEP ST II CAPABILITY CURVE


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19. RANGANADI HEP CAPABILITY CURVE


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20. LOKTAK HEP CAPABILITY CURVE


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21. ROKHIA UNIT 3, 4 & 6 CAPABILITY CURVE


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22. ROKHIA & BARAMURA CAPABILITY CURVE


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23. OTPC PALATANA GTG CAPABILITY CURVE


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23. OTPC PALATANA STG CAPABILITY CURVE


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8 CONCLUSION 8.1 Generators, synchronous condensers, SVCs, and S TATCOMs all provide

fast, continuously controllable reactive support an d voltage control. LTC transformers provide nearly continuous voltage cont rol but they are slow because the transformer moves reactive power from o ne bus to another, the control gained at one bus is at the expense of the other. Capacitors and inductors are not variable and offer control on ly in large steps.

8.2 An unfortunate characteristic of capacitors and capacitor-based SVCs is

that output drops dramatically when voltage is low and support is needed most. The output of a capacitor, and the capacity o f an SVC, is proportional to the square of the terminal voltage. STATCOMs provide more support under low-voltage conditions than capa citors or SVCs do because they are current-limited devices and their output drops linearly with voltage.

8.3 The output of rotating machinery (i.e., generat ors and synchronous

condensers) rises with dropping voltage unless the field current is actively reduced. Generators and synchronous conden sers generally have additional emergency capacity that can be used for a limited time. Voltage-control characteristics favour the use of g enerators and synchronous condensers. Costs, on the other hand, f avor capacitors.

8.4 Generators have extremely high capital costs be cause they are designed

to produce real power, not reactive power. Even the incremental cost of obtaining reactive support from generators is high, although it is difficult to unambiguously separate reactive-power costs from real-power costs. Operating costs for generators are high as well bec ause they involve real-power losses. Finally, because generators have othe r uses, they experience opportunity costs when called upon to si multaneously provide high levels of both reactive and real power .

8.5 Synchronous condensers have the same costs as g enerators but,

because they are built solely to provide reactive s upport, their capital costs do not include the prime mover or the balance of plant and they incur no opportunity costs. SVCs and STATCOMs are h igh-cost devices, as well, although their operating costs are lower t han those for synchronous condensers and generators.


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9 SUMMARY 9.1 The process of controlling voltages and managin g reactive power on

interconnected transmission systems is well underst ood from a technical perspective. Three objectives dominate reactive-pow er management. First, maintain adequate voltages throughout the tr ansmission system under current and contingency conditions. Second, m inimize congestion of real-power flows. Third, minimize real-power los ses.

9.2 This process must be performed centrally becaus e it requires a

comprehensive view of the power system to assure th at control is coordinated. System operators and planners use soph isticated computer models to design and operate the power system relia bly and economically. Central control by rule works well bu t may not be the most technically and economically effective means.

9.3 The economic impact of control actions can be q uite different in a

restructured/regulated industry than for vertically integrated utilities. While it may be sufficient to measure only the resp onse of the system in aggregate for a vertically integrated utility, dete rmining individual generator performance will be critical in a competi tive environment.

9.4 While it reduces or eliminates opportunity cost s by providing sufficient

capacity, it can waste capital. When an investor is considering construction of new generation, the amount of react ive capability that the generator can provide without curtailing real-power production should depend on system requirements and the economics of alternatives, not on a fixed rule.

9.5 The introduction of advanced devices, such as STATCOMs and SVCs,

further complicates the split between transmission- and generation based voltage control. The fast response of these devices often allows them to substitute for generation-based voltage control. Bu t their high capital costs limit their use. If these devices could parti cipate in a competitive voltage-control market, efficient investment would be encouraged.

9.6 In areas with high concentrations of generation , sufficient interaction

among generators is likely to allow operation of a competitive market. In other locations, introduction of a small amount of controllable reactive support on the transmission system might enable mar ket provision of the bulk of the reactive support. In other locations, e xisting generation would be able to exercise market power and would continue to require economic regulation for this service.


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9.7 A determination of the extent of each type with in each region would be a

useful contribution to restructuring. System planne rs and operators need to work closely together during the design of new f acilities and modification of existing facilities. Planners must design adequate reactive support into the system to provide satisfactory vol tage profiles during normal and contingency operating conditions. Of par ticular importance is sufficient dynamic support, such as the reactive ou tput of generators, which can supply additional reactive power during c ontingencies.

9.8 System operators must have sufficient metering and analytical tools to be

able to tell when and if the operational reactive r esources are sufficient. Operators must remain cognizant of any equipment ou tages or problems that could reduce the system’s static or dynamic re active support below desirable levels. Ensuring that sufficient reactive resources are available in the grid to control voltages may be increasingly difficult because of the disintegration of the electricity industry.

9.9 Traditional vertically integrated utilities con tained, within the same entity,

generator reactive resources, transmission reactive resources, and the control center that determined what resources were needed when. Presently, these resources and functions are placed within three different entities. In addition, these entities have differen t, perhaps conflicting, goals. In particular, the owners of generating reso urces will be driven, in competitive generation markets, to maximize the ear nings from their resources. They will not be willing to sacrifice re venues from the sale of real power to produce reactive power unless appropr iately compensated.

9.10 Similarly, transmission owners will want to be sure that any costs they

incur to expand the reactive capabilities on their system (e.g., additional capacitors) will be reflected fully in the transmis sion rates that they are allowed to charge.

9.11 Failure to appropriately compensate those enti ties that provide voltage-

control services could lead to serious reliability problems and severe constraints on inter regional links and other conge sted areas as TTC (Total Transfer Capability) has a voltage limit fun ction as a baggage with it which is directly linked to var compensation. Wi th dynamic ATC’s (Available Transfer capability), Var compensation i f not seriously thought of may have serious commercial implications in time to come due to the amount of bulk power trading happening across the c ountry in today’s context.


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10 Statutory Provisions for Reactive Power Management and voltage Control

10.1 Provision in the Central Electricity Authority (Tec hnical Standard for connectivity to the grid) Regulations 2007 [8]:

Extracts from this standard is as reproduced below for ready reference.

Part II : Grid Connectivity Standards applicable to the Generating Units The units at a generating station proposed to be co nnected to the grid shall comply with the following requirements beside s the general connectivity conditions given in the regulations an d general requirements given in part-I of the Schedule:-

1. New Generating Units

Hydro generating units having rated capacity of 50 MW and above shall be capable of operation in synchronous condenser mode, where ever feasible.

2. Existing Units

For thermal generating unit having rated capacity o f 200 MW and above and hydro units having rated capacity of 100 MW and above, the following facilities would be pro vided at the time of renovation and modernization.

(1) Every generating unit shall have Automatic Vol tage

Regulator. Generators having rated capacity of 100 MW and above shall have Automatic Voltage Regulator with two separate with two separate channels having independent inputs and automatic changeover.

10.2 Provision in The Indian Electricity Grid Code (IEGC ), 2010:

10.2.1 As per sec 3.5 of IEGC planning criterion ge neral policy

(a) The planning criterion are based on the securit y philosophy

on which the ISTS has been planned. The security philosophy may be as per the Transmission Planning Criteria and other guidelines as given by CEA. The general policy shall be as detailed below:

i) As a general rule, the ISTS shall be capable o f

withstanding and be secured against the following contingency outages


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a. without necessitating load shedding or reschedu ling

of generation during Steady State Operation: - Outage of a 132 kV D/C line or, - Outage of a 220 kV D/C line or, - Outage of a 400 kV S/C line or, - Outage of single Interconnecting

Transformer, or - Outage of one pole of HVDC Bipole line , or

one pole of HVDC back to back Station or - Outage of 765 kV S/C line.

b. without necessitating load shedding but could b e with rescheduling of generation during steady state operation- - Outage of a 400 kV S/C line with TCSC, or - Outage of a 400kV D/C line, or - Outage of both pole of HVDC Bipole line or

both poles of HVDC back to back Station or - Outage of a 765kV S/C line with series

compensation.

ii) The above contingencies shall be considered as suming a pre-contingency system depletion (Planned outage) of another 220 kV D/C line or 400 kV S/C line in anoth er corridor and not emanating from the same substation . The planning study would assume that all the Generating Units may operate within their reactive capability curves and the network voltage profile s hall also be maintained within voltage limits specified

(e) CTU shall carry out planning studies for React ive Power

compensation of ISTS including reactive power compensation requirement at the generator’s /bulk consumer’s switchyard and for connectivity of new generator/ bulk consumer to the ISTS in accordance with Central Electricity Regulatory Commission ( Grant o f Connectivity, Long-term Access and Medium-term Open Access in inter-state Transmission and related matt ers) Regulations, 2009.

10.2.2 As per Sec 4.6.1 of IEGC, Important Technica l Requirements for

Connectivity to the Grid:

Reactive Power Compensation

a) Reactive Power compensation and/or other facil ities, shall be provided by STUs, and Users connected to ISTS as far as possible in the low voltage systems close to the load


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points thereby avoiding the need for exchange of Reactive

Power to/from ISTS and to maintain ISTS voltage wit hin the specified range.

b) The person already connected to the grid shall a lso provide

additional reactive compensation as per the quantum and time frame decided by respective RPC in consultatio n with RLDC. The Users and STUs shall provide information to RPC and RLDC regarding the installation and healthi ness of the reactive compensation equipment on regular b asis. RPC shall regularly monitor the status in this rega rd.

10.2.3 In chapter 5 of IEGC operating code for regi onal grids:

5.2(k) All generating units shall normally have th eir automatic

voltage regulators (AVRs) in operation. In particul ar, if a generating unit of over fifty (50) MW size is requi red to be operated without its AVR in service, the RLDC shall be immediately intimated about the reason and duration , and its permission obtained. Power System Stabilizers ( PSS) in AVRs of generating units (wherever provided), shall be got properly tuned by the respective generating unit ow ner as per a plan prepared for the purpose by the CTU/RPC from time to time. CTU /RPC will be allowed to carry out checking of PSS and further tuning it, wherever con sidered necessary.

5.2(o) All Users, STU/SLDC , CTU/RLDC and NLDC, sha ll also

facilitate identification, installation and commiss ioning of System Protection Schemes (SPS) (including inter-tr ipping and run-back) in the power system to operate the transmission system closer to their limits and to p rotect against situations such as voltage collapse and cas cade tripping, tripping of important corridors/flow-gate s etc.. Such schemes would be finalized by the concerned RP C forum, and shall always be kept in service. If any SPS is to be taken out of service, permission of RLDC shall b e obtained indicating reason and duration of anticipa ted outage from service.

5.2(s) All Users, RLDC, SLDC STUs , CTU and NLDC sh all take all

possible measures to ensure that the grid voltage a lways remains within the following operating range.


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Table 6: IEGC operating voltage range

5.2(u) (ii) During the wind generator start-up, the wind generator

shall ensure that the reactive power drawl (inrush currents incase of induction generators) shall not affect the grid performance.

10.2.4 In chapter 6 of IEGC Section-6.6 Reactive Po wer & Voltage Control:

1. Reactive power compensation should ideally be p rovided

locally, by generating reactive power as close to t he reactive power consumption as possible. The Regiona l Entities except Generating Stations are therefore e xpected to provide local VAr compensation/generation such t hat they do not draw VArs from the EHV grid, particular ly under low-voltage condition. To discourage VAr drawals by Regional Entities except Generating Stations, VAr exchanges with ISTS shall be priced as follows:

- The Regional Entity except Generating Stations pays

for VAr drawal when voltage at the metering point i s below 97%

- The Regional Entity except Generating Stations gets

paid for VAr return when voltage is below 97% - The Regional Entity except Generating Stations gets

paid for VAr drawal when voltage is above103%

Voltage – (KV rms)

Nominal Maximum Minimum

765 800 728

400 420 380

220 245 198

132 145 122

110 121 99

66 72 60

33 36 30


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The Regional Entity except Generating Stations pays for VAr return when voltage is above 103% Provided that there shall be no charge/payment for VAr drawal/return by a regional Entity except Generating Stations on its o wn line emanating directly from an ISGS.

2. The charge for VArh shall be at the rate of 10 paise/kVArh

w.e.f. 1.4.2010, and this will be applicable betwee n the Regional Entity, except Generating Stations, and th e regional pool account for VAr interchanges. This ra te shall be escalated at 0.5paise/kVArh per year thereafter, unless otherwise revised by the Commission.

3 Notwithstanding the above, RLDC may direct a Reg ional

Entity except Generating Stations to curtail its VA r drawal/injection in case the security of grid or sa fety of any equipment is endangered.

4. In general, the Regional Entities except Genera ting Stations

shall endeavor to minimize the VAr drawal at an interchange point when the voltage at that point is below 95% of rated, and shall not return VAr when the vol tage is above 105%. ICT taps at the respective drawal point s may be changed to control the VAr interchange as per a Regional Entity except Generating Stations’s reques t to the RLDC, but only at reasonable intervals.

5. Switching in/out of all 400 kV bus and line Reac tors

throughout the grid shall be carried out as per ins tructions of RLDC. Tap changing on all 400/220 kV ICTs shall also be done as per RLDCs instructions only.

6. The ISGS and other generating stations connecte d to

regional grid shall generate/absorb reactive power as per instructions of RLDC, within capability limits of t he respective generating units, that is without sacrif icing on the active generation required at that time. No pay ments shall be made to the generating companies for such VAr generation/absorption.

7. VAr exchange directly between two Regional Enti ties

except Generating Stations on the interconnecting l ines owned by them (singly or jointly) generally address or cause a local voltage problem, and generally do not have an impact on the voltage profile of the regional gr id. Accordingly, the management/control and commercial handling of the VAr exchanges on such lines shall b e as per following provisions, on case-by-case basis:


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i) The two concerned Regional Entities except Gene rating

Stations may mutually agree not to have any charge/payment for VAr exchanges between them on an interconnecting line.

ii) The two concerned Regional Entities except Gen erating

Stations may mutually agree to adopt a payment rate/scheme for VAr exchanges between them identica l to or at variance from that specified by CERC for V Ar exchanges with ISTS. If the agreed scheme requires any additional metering, the same shall be arranged by the concerned Beneficiaries.

iii) In case of a disagreement between the concerne d

Regional Entities except Generating Stations (e.g. one party wanting to have the charge/payment for VAr exchanges, and the other party refusing to have the scheme), the scheme as specified in Annexure-2 shal l be applied. The per kVArh rate shall be as specifie d by CERC for VAr exchanges with ISTS.

iv) The computation and payments for such VAr excha nges

shall be effected as mutually agreed between the tw o Beneficiaries.

10.3 THE AEGCL GAZETTE, EXTRAORDINARY, FEBRUARY 10, 2005

10.3.1 IN CHAPTER 9: FREQUENCY AND VOLTAGE MANAGEME NT 10.3.1.1 (9.1) Introduction

(a) This section describes the method by which all Users of the State Grid shall cooperate with SLDC in contributin g towards effective control of the system frequency and manag ing the grid voltage.

(b) State Grid normally operates in synchronism wi th the North-

Eastern Regional Grid and NERLDC has the overall responsibility of the integrated operation of the N orth-Eastern Regional Power System. The constituents of the Region are required to follow the instructions of N ERLDC for the backing down generation, regulating loads, MVAR drawal etc. to maintain the system frequency and the grid voltage.

(c) SLDC shall instruct SSGS to regulate Generatio n/Export and

hold reserves of active and reactive power within t heir


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respective declared parameters. SLDC shall also reg ulate the load as may be necessary to meet the objective.

(d) System voltages levels can be affected by Regi onal

operation. The SLDC shall optimise voltage manageme nt by adjusting transformer taps to the extent available and switching of circuits/ capacitors/ reactors and oth er operational steps. SLDC will instruct generating st ations to regulate MVAr generation within their declared para meters. SLDC shall also instruct Distribution Licensees to regulate demand, if necessary.

10.3.1.2 (9.2) Objective

The objectives of this section are as follows: (a) To define the responsibilities of all Users in contributing to

frequency and voltage management.

(b) To define the actions required to enable SLDC to maintain System voltages and frequency within acceptable lev els in accordance Planning and Security Standards of IEGC.

10.3.1.3 (9.3) Frequency Management

The rated frequency of the system shall be 50 Hz an d shall normally be regulated within the limits prescribed in IEGC C lause 4.6(b). As a constituent of North-Eastern Region, the SLDC shall make all possible efforts to ensure that grid frequency rema in within normal band of 49.5 – 50.2Hz (Presently IEGC band is 49.5- 50.2 Hz).

10.3.1.4 (9.4) Basic philosophy of control Frequency being essentially the index of load-gener ation balance conditions of the system, matching of available gen eration with load, is the only option for maintaining frequency within the desired limits. Basically, two situations arise, viz., a surplus si tuation and a deficit situation. The automatic mechanisms available for a djustment of load/generation are (i) Free governor action; (ii) Maintenance of spinning reserves and (iii) Under-frequency relay a ctuated shedding. These measures are essential elements of system sec urity. SLDC shall ensure that Users of the State Grid comply wi th provisions of clause 6.2 of the IEGC so far as they apply to them . The SLDC in coordination with Users shall exercise the manual m echanism for frequency control under following situations:

10.3.1.5 (9.5) Falling frequency:

Under falling frequency conditions, SLDC shall take appropriate action to issue instructions, in coordination with NERLDC to arrest


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the falling frequency and restore it to be within p ermissible range. Such instructions may include dispatch instruction to SSGS and/or instruction to Distribution Licensees and Open acce ss customers to reduce load demand by appropriate manual and/or aut omatic load shedding.

10.3.1.6 (9.6) Rising Frequency

Under rising frequency conditions, SLDC shall take appropriate action to issue instructions to SSGS in co-ordinati on with NERLDC, to arrest the rising frequency and restore frequenc y within permissible range through backing down hydel genera tion and thermal generation to the level not requiring oil s upport. SLDC shall also issue instructions to Distribution Licensees a nd Open access customers in coordination with NERLDC to lift Load shedding (if exists) in order to take additional load.

10.3.1.7 (9.7) Responsibilities

SLDC shall monitor actual Drawal against scheduled Drawal and regulate internal generation/demand to maintain thi s schedule. SLDC shall also monitor reactive power drawal and availa bility of capacitor banks. Generating Stations within AEGCL shall follo w the dispatch instructions issued by SLDC.Distribution Licensees and Open access customers shall co-operate with SLDC in mana ging load & reactive power drawal on instruction from SLDC as r equired.

10.3.1.8 (9.8) Voltage Management

(a) Users using the Intra State transmission syste m shall make all possible efforts to ensure that the grid voltag e always remains within the limits specified in IEGC at clau se 6.2(q) and produced below:

(b) AEGCL Gridco and/or SLDC shall carry out load flow studies

based on operational data from time to time to pred ict where voltage problems may be encountered and to identify appropriate measures to ensure that voltages remain within the defined limits. On the basis of these studies S LDC shall

Nominal Maximum Minimum

400 420 380

220 245 198

132 145 122


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instruct SSGS to maintain specified voltage level a t interconnecting points. SLDC and AEGCL Gridco shall co-ordinate with the Distribution Licensees to determi ne voltage level at the interconnection points. SLDC shall con tinuously monitor 400/220/132kV voltage levels at strategic s ub-stations to control System voltages.

(c) SLDC in close coordination with NERLDC shall t ake

appropriate measures to control System voltages whi ch may include but not be limited to transformer tap chang ing, capacitor / reactor switching including capacitor s witching by Distribution Licensees at 33 kV substations, ope ration of Hydro unit as synchronous condenser and use of MVAr reserves with SSGS within technical limits agreed t o between AEGCL Gridco and Generators. Generators shall infor m SLDC of their reactive reserve capability promptly on request.

(d) APGCL and IPPs shall make available to SLDC th e up to date

capability curves for all Generating Units, as deta iled in Chapter 5.indicating any restrictions, to allow acc urate system studies and effective operation of the Intra State transmission system. CPPs shall similarly furnish t he net reactive capability that will be available for Expo rt to / Import from Intra State transmission system.

(e) Distribution Licensees and Open access custome rs shall

participate in voltage management by providing Loca l VAR compensation (as far as possible in low voltage sys tem close to load points) such that they do not depend upon E HV grid for reactive support.

10.3.1.9 (9.9) General

Close co-ordination between Users and SLDC, AEGCL G ridco and NERLDC shall exist at all times for the purposes of effective frequency and voltage management.


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11. Bibliography:

1. Best practice manual of transformer for BEE and IR EDA by Devki energy

consultancy pvt. ltd. 2. NERPC progress report August, 2010. 3. Document on MeSEB capacity building and training d ocument 4. Manual on Transmission Planning Criteria, CEA, Gov t. of India, June 1994 5. Indian Electricity Grid Code, CERC, India, 2010 6. The Central Electricity Authority (Technical Stand ard for connectivity to the grid)

Regulations 2007. 7. Operation procedure for NER January 2010. 8. Document on Metering code for AEGCL grid. 9. Principles of efficient and reliable reactive powe r supply and consumption, staff

report, FERC, Docket No. AD05-1-000, February 4, 20 05 10. Proceedings of workshop on grid security & managem ent 28 th and 29 th April,

2008 Bangalore. 11. Extra High Voltage AC transmission Engineering – R D Begamudre. 12. Electrical Engineering Handbook – SIEMENS. 13. C. W. Taylor, “Power System Voltage Stability”, Mc Graw-Hill, 1994 . 14. THE AEGCL GAZETTE, EXTRAORDINARY, FEBRUARY 10, 200 5


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POWER SYSTEM OPERATION CORPORATION LIMITED (A wholly owned subsidiary of Powergrid)

(A GOVT. OF INDIA UNDERTAKING )

NORTH EASTERN REGIONAL LOAD DESPATCH CENTRE DONGTIEH-LOWER NONGRAH,

LAPALANG, SHILLONG – 793 006

MEGHALAYA

Ner Reactive Power Management Manual 2012

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