REACTIVE POWER MANAGEMENT VOLTAGE CONTROL IN · PDF fileREACTIVE POWER MANAGEMENT AND VOLTAGE...

One Nation. One Grid

REACTIVE POWER MANAGEMENT &

VOLTAGE CONTROL IN

NORTH EASTERN REGION

December 2011

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 voltage regulation 20

2 Transmission Lines and Reactive Power Compensation 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 and compensation 23

3 Series and Shunt Capacitor Voltage Control 35

3.1 Introduction 35 3.2 MeSEB capacity building and training document suggestion 36 3.3 THE ASSAM GAZETTE, EXTRAORDINARY, FEBRUARY 10, 2005 36

4 Transformer Load Tap Changer and Voltage Control 38

4.1 Introduction 38 4.2 THE ASSAM GAZETTE, EXTRAORDINARY, FEBRUARY 10, 2005 39

5 HVDC and Voltage Control 50

5.1 Introduction 50 5.2 HVDC Configuration 50 5.3 Reactive power source 53 5.4 ”Inter-regional Transmission system for power export from NER to NR/WR” 53

6 FACTS and Voltage Control 54

6.1 Introduction 54 6.2 Static Var Compensator (SVC) 54 6.3 Converter-based Compensator 55 6.4 Series-connected controllers 56


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7 Generator Reactive Power and Voltage Control 57 7.1 Introduction 57 7.2 Synchronous condensers 59

8 CONCLUSION 82

9 SUMMARY 83

10 Statutory Provisions for Reactive Power Management and Voltage Control 85

10.1 Provision in the Central Electricity Authority (Technical 85 Standard for connectivity to the grid) Regulations 2007 [8]:

10.2 Provision in the Indian Electricity Grid Code (IEGC), 2010 85 10.3 THE ASSAM GAZETTE, EXTRAORDINARY, FEBRUARY 10, 2005 90

11. Bibliography 94

Details of List

LIST-1: 400 KV LINE DETAILS OF POWERGRID IN NORTH EASTERN REGION 25



LIST-4: 132 KV LINE LIST OF NEEPCO IN NORTH EASTERN REGION 27

LIST-5: 132 KV LINE LIST OF AEGCL IN NORTH EASTERN REGION 27

LIST-6: 132 KV LINE LIST OF MANIPUR IN NORTH EAST 28

LIST-7: 132 KV LINE LIST OF TSECL IN NORTH EASTERN REGION 28 LIST-8: 132 KV LINE LIST OF NAGALAND IN NORTH EASTERN REGION 29

LIST-9: 132 KV LINE LIST OF MIZORAM IN NORTH EASTERN REGION 29 LIST-10: 132 KV LINE LIST OF MeECL IN NORTH EAST 29

LIST-11: 66 KV LINE DETAILS OF NORTH EASTERN REGION 30

LIST-12: SHUNT COMPENSATED LINES IN NORTH EASTERN REGION 31

LIST-13: SHUNT COMPESATED INTER – REGIONAL LINES IN NORTH EASTERN REGION 31

LIST-14: INTER-STATE LINE DETAILS OF NORTH EASTERN REGION 32

LIST-15: FIXED, SWITCHABLE AND CONVERTIBLE LINE REACTORS IN NORTH EASTERN REGION 33

LIST-16: BUS REACTORS IN NORTH EASTERN REGION 34

LIST-17: TERTIARY REACTORS ON 33 KV SIDE OF 400/220/33 KV ICTS IN NORTH EASTERN REGION 34

LIST-18: SUBSTATIONS IN NER 37

LIST-19: SHUNT CAPACITOR DETAILS OF NORTH EASTERN REGION 37

LIST-20: ICT DETAILS OF POWERGRID IN NORTH EASTERN REGION 40

LIST-21: ICT DETAILS OF NEEPCO IN NORTH EASTERN REGION 40

LIST-22: ICT DETAILS OF NHPC IN NORTH EASTERN REGION 41

LIST-23: ICT DETAILS OF ARUNACHAL PRADESH IN NORTH EASTERN REGION 41

LIST-24: ICT DETAILS OF AEGCL IN NORTH EASTERN REGION 41

LIST-25: ICT DETAILS OF MANIPUR IN NORTH EASTERN REGION 46


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LIST-26: ICT DETAILS OF MeECL IN NORTH EASTERN REGION 46

LIST-27: ICT DETAILS OF MIZORAM IN NORTH EASTERN REGION 47

LIST-28: ICT DETAILS OF NAGALAND IN NORTH EASTERN REGION 48

LIST-29: ICT DETAILS OF TSECL IN NORTH EASTERN REGION 48

LIST-30: TRANSMISSION/TRANSFOMATION/VAR COMPENSATION CAPACITY OF NER 49

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 38 Fig14. HVDC fundamental components 52 Fig15. Static VAR Compensators (SVC) 55 Fig16. STATCOM topologies 55 Fig17. Series-connected FACTS controllers 56 Fig18. D-Curve of a typical Generator 57

Annexure: Capability Curve of generating machines of NER 1 LTPS UNIT 5, 6 & 7 CAPABILITY CURVE 60 2 NTPS UNIT 1, 2 & 3 CAPABILITY CURVE 61 3 NTPS UNIT 4 CAPABILITY CURVE 62 4 NTPS UNIT 6 CAPABILITY CURVE 63 5 LTPS CAPABILITY CURVE 64 6 NTPS CAPABILITY CURVE 65 7 UMIUM ST I CAPABILITY CURVE 66 8 UMIUM STAGE II CAPABILITY CURVE 67 9 UMIUM STAGE III CAPABILITY CURVE 68 10 UMIUM STAGE IV CAPABILITY CURVE 69 11 AGBPP UNIT 5, 6, 7, 8 & 9 CAPABILITY CURVE 70 12 AGBPP UNIT 1, 2, 3 & 4 CAPABILITY CURVE 71 13 AGTPP CAPABILITY CURVE 72 14 DOYANG HEP UNIT 1 CAPABILITY CURVE 73 15 KHANDONG HEP UNIT 2 CAPABILITY CURVE 74 16 KOPILI HEP UNIT 1 CAPABILITY CURVE 75 17 KOPILI HEP UNIT 2 CAPABILITY CURVE 76 18 KOPILI HEP ST II CAPABILITY CURVE 77 19 RANGANADI HEP CAPABILITY CURVE 78 20 LOKTAK HEP CAPABILITY CURVE 79 21 ROKHIA UNIT 3, 4 & 6 CAPABILITY CURVE 80 22 ROKHIA & BARAMURA CAPABILITY CURVE 81


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List of Tables

Table 1 Reactive power compensation sources 16 Table 2 Fault level at important sub-stations of NER 19 Table 3 Line Parameters and Surge Impedance Loading of Different Conductor Type 24 Table 4 Equipment preference 35 Table 5 List of units in NER to be normally operated with free governor

action and AVR in service 59 Table 6 IEGC Operating Voltage Range 88


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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 direction towards improvement of system reliability and power quality.

It is also significant to mention that due to the massive load growth in the country, the existing power networks are operated under greater stress with transmission lines carrying power near their limits. Increase in the complexity of network and being loaded non-uniformly has increased its vulnerability to grid disturbances due to abnormal voltages (High and Low). In the past, reason 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 congestion 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 includes commissioning of 220 kV Kathalguri – Tinsukia II (AEGCL), 220/132 kV 160 MVA ICT at BTPS (AEGCL), 132 kV Dimapur (PGCIL) – Dimapur II, 132 kV Dimapur – Kohima, 132 kV Rangia (AEGCL) – Motonga (Bhutan) international line and implementation of NGR by - passing scheme of 50 MVAR Line Reactors of 400 kV Balipara – RHEP D/C for convertion as bus reactor at 400 kV Balipara S/S has led to reinforcement in the NER grid elements and greater options of controlling grid parameters. With the increase 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 edition to understand the basics of reactive power and its management towards voltage control, its significance and consequences of inadequate reactive power support. It also includes details of reactive power support available at present and efforts 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 is a concept used by engineers to describe the background energy movement in an Alternating Current (AC) system arising from the production of

electric and magnetic fields. These fields store energy which changes through each AC cycle. Devices which store energy by virtue of a magnetic field produced by a flow of current are said to absorb reactive power (viz. transformers, Reactors) and those which store energy by virtue of electric fields are said to generate reactive 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 limits. Reactive power flows can give rise to substantial voltage changes across the system, which means that it is necessary to maintain reactive power balances between sources of generation and points of demand on a 'zonal basis'. Unlike system frequency, which is consistent throughout an interconnected system, voltages experienced at points 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-Reactive (Q). Normally electric power is generated, transported and consumed in alternating current (AC) networks. Elements of AC systems supply (or produce) and consume (or absorb or lose) two kinds of power: real power and reactive power.

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

lamps). Reactive power supports the voltages that must be controlled for system reliability. In AC power networks, while active power corresponds to useful work, reactive power supports voltage magnitudes that are controlled for system reliability, voltage stability, and operational acceptability.

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

variable transformer tap settings, compensation, switchable shunt capacitor and reactor banks plus allocation of new shunt capacitor and reactor banks in a manner that best achieves a reduction 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 the lines. When the transmission system is heavily loaded, the active power 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 by loads through the lines. Reactive power supply is necessary in the reliable operation of AC power systems. Several recent power outages worldwide 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


Although AC voltage and current pulsate at the same frequency, they peak at a different time. Power is the algebraic product 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 called 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 essential 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 Power aspect.

Visualize a boat on a canal, pulled by a horse on the 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 straight manner rather deviating towards the bank. This is in line with the understanding of the reactive power.

Fig 3. Boat pulled by a Horse Fig 4. Direction of pull

Fig 5. Ve

ctor representation of the analogy

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1.2.1 In the horse and boat analogy, the horse’s objective (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, limits the horse’s capacity to deliver real work of moving straightly. Therefore, the power required to keep the boat steady in navigating straightly is delivered by the rudder movement (reactive power). Without reactive power there can be no transfer of real power, likewise without the support of rudder, the boat cannot move in a straight line.

1.2.2 Reactive power is like the bouncing up and down 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 movement across the trampoline, even though it appears to be movement in the opposite direction.

1.2.3 Reactive power and real power work together in 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 adjust the angle of the platin two directions, in order to keep the ball rolling through the mwithout falling into any holes. Those twists are REACTIVE POWER, whelps propel the real power through to its ultimate goal, which is delito the user. Without reactive power, ball falls into holes along the which are NETWORK failures.

1.2.5 Both of these examples illustrate how important it is to understand

system and how it works in order to meet our objectives effectively. InLABYRINTSPEL game, if the structure of the system is not taken account, winning would be really easy because one knob would be tu

Fig 6. LABYRINTSPEL

form aze

hich very way,

the the into

rned

http://gamesmuseum.uwaterloo.ca/puzzles/maze/


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all the way in one direction, and the other knob all the way in the other direction, and the ball would merely roll across the platform. If that’s the model how electricity works, then that would deliver 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 more going on that means it’s essential to do things that seem counterintuitive, like bouncing up and down on the trampoline or turning the platform in the game towards west to avoid the hole to the east, even though 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 electrons and the circuits. Otherwise, the electricity just flows from 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 they

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

1.3 Understanding Vectorially

1.3.1 In practice circuits are invariably combinations of resistance, inductance and capacitance. The combined effect of these impedances to the flow of current is most easily assessed by expressing the power flows as vectors that show the angular relationship between the powers waveforms associated with each type of impedance. Figure 7 shows how the vectors can be resolved to determine the net capacity of the circuit needed to transfer the power requirements of the connected equipment.

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 re

presentation


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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 active power, and is measured in kilovolts-ampere (kVA). The ratio of the 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 solely resistance, so that the

inductance and capacitance exactly cancel each other 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 transferring 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 distribution assets such as cables, lines and transformers must be sized to meet the kVA requirement, but the useful power drawn by the customer is the kW component, a significant cost emerges from having to 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 limits 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 reactive power production at certain locations (usually near a load center) can sometimes alleviate transmission constraints and allow cheaper real power to be delivered into a load pocket.

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

power system is Important for proper operation of electric power equipment and saving it from imminent damage, to reduce transmission losses and to maintain the ability of the system to withstand disturbances and prevent voltage collapse. In general terms, decreasing 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 and the voltage to drop further. If current increases too much, transmission lines trip, or go off-line, overloading other lines and potentially causing cascading


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failures. If voltage drops too low, some generators will automatically 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 supply • 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 voltage and loss of load. The result is a progressive and uncontrollable decline in voltage, all because the power system is unable to provide the reactive power required to supply the reactive power demand.

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

the cascading events accompanying voltage instability, the problem is considered to be a voltage collapse phenomenon. Voltage collapse normally takes place when a power system is heavily loaded and/or has limited reactive power to support the load. The limiting factor could be the lack of reactive power (SVC and generators hit limits) production or the inability to transmit reactive power through the transmission 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 limit the transfer capacity of reactive power through the system.

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

problem but it is now considered to be a non linear dynamic phenomenon. The dynamics in power systems involve the 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


All these factors play a significant part in voltage collapse as they effect the transmission, consumption, and generation of reactive power.

Usually voltage stability is categorized into two parts

• Large disturbance voltage stability • Small disturbance voltage stability

1.5.5 When a large acceptable volmaintain voltaand the interacprotections. Sa small perturbdisturbance vocontinuous co

1.6 Proximity to 1.6.1 Static voltage

imbalance. Threactive powersystem approaboth real and r

Fig 8. Time frames for voltage stability phenomena

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disturbance occurs, the ability of the system to maintain tages falls due to the impact of the disturbance. Ability to ges is dependent on the system and load characteristics, tions of both the continuous and the discrete controls and

imilarly, the ability of the system to maintain voltages after ation i.e. incremental change in load is referred to as small ltage stability. It is influenced by the load characteristics,

ntrol and discrete controls at a given instant of time.

Instability

instability is mainly associated with reactive power us, the loadability of a bus in a system depends on the support that the bus can receive from the system. As the ches the maximum loading point or voltage collapse point, eactive power losses increase rapidly.


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

static voltage stability, slowly developing changes in the power system occur that eventually lead to a shortage of reactive 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 voltage dreactive power losses is observed. The only way to savvoltage collapse is to reduce the reactive power loadreactive power prior to reaching the point of voltage col

• These are curves drawn between V and P o

constant load power factor. • These are produced by using a serie

solutions for different load levels. • At the knee point or the nose point of t

voltage drops rapidly with an increase in th• Power flow solution fails to converge beyo

indicates the instability.

1.7 Reactive Reserve Margin 1.7.1 The amount of unused available capability of reactive p

as dynamic in the system (at peak load for a utility systepercentage of total capability is known as Reactive rese

1.7.2 Voltage collapse normally occurs when sources p

power reach their limits i.e. generators, SVCs or shunt ris not much reactive power to support the load. As reac

Knee point

∆v

Fig 9. PV curve and under differ

Voltage stability margin ent conditions

rop due to heavy e the system from or add additional lapse.

f a critical bus at a

s of power flow

he V-P curve, the e load demand. nd this limit which

ower static as well m) as a rve margin.

roducing reactive eactors, and there tive power is


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

1.7.3 The voltage stability margin can be defined as a measure 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 reactive 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 contingencies. The precincts where reactive power reserves were exhausted would be identified as critical areas.

1.7.5 Reactive power requirements over and above those which occur naturally

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

• STATIC SOURCES: Static sources are typically transmission

and distribution equipments such as Capacitors and Reactors that are relatively static and can respond to the changes in voltage – support requirements only slowly and in discrete steps. Devices are inexpensive, but the associated switches, control, and communications, and 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, Synchronous generators and solid-state devices such as FACTS, SVC, STATCOM, D-VAR, and SuperVAR which are normally dynamic and can respond within cycles to changing reactive power requirement. These are typically considered as transmission service devices.

1.7.6 Static devices typically have lower capital costs than dynamic devices,

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


1.7.7 Reactive power absorption occurs when current flows through an

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

Sources of Reactive Power Sinks of Reactive Power

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

loaded) Ø Fuel cells Ø PV systems

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

Ø Transmission lines (Heavily loaded)

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

plants) Ø Loads • Induction motors (Pumps,

Fans etc) • Inductive loads (Arc furnace

etc)

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

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

Table 1. Reactive power compensation sources

Fig 10. Average cost of Reactive power technologies

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Pag

1.8 NER GRID – Overview

1.8.1 NER grid with a maximum peak requirement of around 1800 MW and installed capacity of 2091 MW caters to the seven north eastern states. It is synchronously connected with NEW GRID through 400 kV D/C BONGAIGAON – NEW SILIGURI, 220 kV D/C BIRPARA – SALAKATI and internationally through 132 kV SALAKATI – GELYPHU(Bhutan). The bottle neck of operating the NER grid arises because of the brittle back bone network of about 6798 Ckt Kms of 132 KV lines, 1102 Ckt Kms of 400 KV lines and 2858 Ckt Kms of 220 KV lines compared to other regional grids.

1.8.2 Almost 50% of the tot

southern part of NER wtrunk lines. This part of to grid disturbance andthe loading of major 13IMPHAL S/C,132 kV JIRIat KOPILI in peak hoursform of cascade tripping

Fig 11. NER Grid map

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al NER load is spread out in 132 kV pocket of hich is without the direct support of major EHV the network is highly sensitive and is susceptible demands more operational acumen. Increase in 2 kV trunk lines, in particular 132 kV DIMAPUR – BAM – LOKTAK S/C and 220/132 kV, 160 MVA ICT has led to many a grid incidents in the past in the accompanied by voltage sag.


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1.8.3 NER system has been strengthened With the commissioning of 220 kV

KATHALGURI – TINSUKIA II (AEGCL), 220/132 kV, 160 MVA ICT at BTPS, 132 kV DIMAPUR – DIMAPUR (NAGALAND), 132 kV DIMAPUR – KOHIMA and 132 kV RANGIA – MOTONGA (AEGCL) in the concluded year. Commissioning of above elements has led to reinforcement in the NER grid elements and furthering the regions interest with the neighbouring country like Bhutan. With the availability of greater options compared to earlier years, grid operation has been smooth and grid parameters were maintained within the prescribe IEGC limits.

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

have revealed that though voltage is a localized factor, it is directly affected by the frequency which is a notional factor. Any lopsidedness in the demand/generation side leading to fluctuations in NEW grid frequency affects NER grid immensely, in particular the voltage profile of the grid, leading to sagging and swelling of voltage heavily during such occasions. Ironically, NER was synchronously connected with NEW grid for stretching the transmission capability to reduce the 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 profile 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 1196 MVAr from shunt reactors and

160 MVAr from shunt capacitors spread across the region.

1.8.7 Skewness in the location of hydro stations and load centers in NER is another obstacle which aggravates the voltage problem further. Lines are long and pass through difficult terrains to the load 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 lightly 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 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. Controlling reactive power flow can reduce losses and congestion on the transmission system.


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1.8.9 Operationally in NER, Voltage is normally controlled 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 constituents and the CTU.

• Circuit switching: Mostly one circuit of the lightly loaded d/c line is kept open keeping in mind the n-1 criterion during high voltage and high frequency period. Voltage differences as well as fault level of stations are taken into account 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 th

control: The automatic voltage reexcitation to maintain the schedterminals of the generators. In reageneration should never be oabsorption limits.

• By generation re-dispatch/resche• Regulating voltage with the help o• By load staggering/shedding.

Table 2. Fault level at importa
nt Sub-Stations of NER
e basic means of voltage gulators (AVR) control field uled voltage levels at the l time operation, connected n reactive generation or

duling. f OLTC’s.


Page 20 of 97

1.9 Reliability Improvement Due to Local Voltage Regulation

1.9.1 Local voltage regulation to a voltage schedule supplied by the utility can

have a very beneficial effect on overall system reliability, reducing the problems caused by voltage dips on distribution circuits 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 slow 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 replaced with compact

fluorescent lights, LED lamps that draw constant power as voltage decreases, and motors are being powered with adjustable-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 reliability from better voltage regulation. Capacitors supply reactive power to boost voltage, but their effect is dramatically diminished as voltage dips.

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

80% voltage, capacitors are only 64% as effective as they are at normal conditions. As voltage continues to drop, the capacitor effect falls off until voltage collapses. The reactive power supplied 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 allow customers to supply dynamic reactive power to regulate voltage could be a tremendous asset to system reliability and efficiency by expanding the margin to voltage collapse.


Page 21 of 97

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. Housekeeping loads at substations (such as security lighting and space conditioning) and transformer excitation losses are roughly constant (i.e., independent of the power flows on the transmission system). Transmission-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 perfect conductors; they have resistance. The consumption of reactive power by transmission lines increases with the square of current i.e., the transmission of reactive power requires an additional demand for reactive power in the system components.

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

geometry of the conductors themselves (primarily the radius of the conductor) and the geometry of the conductor configuration (the distances between each conductor and ground and the distances among conductors).

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

inductive and capacitive characteristics. At low line loadings, the capacitive effect dominates, and generators and transmission-related reactive equipment must absorb reactive power to maintain line voltages within their appropriate limits. On the other hand, at high line loadings, the inductive effect dominates, and generators, capacitors, and other reactive devices must produce reactive power

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

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


Page 22 of 97

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

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

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

the same time. The reactive power generation is almost constant, because the voltage of the line is usually constant, and the line’s reactive power consumption depends on the current or load connected to the line that is variable. So at the heavy load conditions transmission 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 inductance is called natural loading or surge impedance loading (SIL) , meaning that the line provides exactly the amount of MVAr needed to support 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 loaded below SIL supply reactive power.

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

is idle charged due to line charging susceptance. This implies a 300 km line generates about 165 MVAR when it is idle charged.

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

reactor. Line reactor’s functionality is to avoid the switching and load rejection over voltages where as Bus reactors are used to avoid the steady state over voltage during light load conditions.

2.3.2 The degree of compensation is decided by an economic 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 inductors) can be divided into parallel sections, each Switched separately, so that discrete changes


Page 23 of 97

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

2.3.3 Reasons for the application of shunt capacitor 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 reduction

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

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

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

2.4 Line loading as function of Line Length and Compensation 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 nee

modified SIL with the multiplying factor derivcurve.The derived steady state limit for a line woufactor from St. Clair's curve.

Fig 12. SIL V
S Compensation
ds to multiple the ed from St. Clair's ld be = SIL modified x

REACTIVE POWER MANAGEM

ENT AND VOLTAGE CON

TROL IN NORTH EASTERN REGION

Page 24 of 97


Page 25 of 97

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 POWERGRID 218.0 1 TWIN MOOSE 8 BONGAIGAON BINAGURI POWERGRID 218.0 2 TWIN MOOSE

LIST-2: 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 SARUSAJAI LANGPI AEGCL 108.0 1 SINGLE ZEBRA 5 SARUSAJAI LANGPI AEGCL 108.0 2 SINGLE ZEBRA 6 SARUSAJAI SAMAGURI AEGCL 124.0 1 SINGLE ZEBRA 7 SARUSAJAI SAMAGURI AEGCL 124.0 2 SINGLE ZEBRA 8 SAMAGURI MARIANI AEGCL 164.0 1 SINGLE ZEBRA

9 DEOMALI KATHALGURI ARUNACHAL

PRADESH 19.0 1 SINGLE ZEBRA

10 BONGAIGAON SALAKATI POWERGRID 10.0 1 SINGLE ZEBRA 11 SALAKATI BIRPARA POWERGRID 160.0 1 SINGLE ZEBRA 12 SALAKATI BIRPARA POWERGRID 160.0 2 SINGLE ZEBRA 13 BALIPARA SAMAGURI AEGCL 55.0 1 SINGLE ZEBRA 14 SALAKATI BTPS AEGCL 2.7 1 ACSR ZEBRA 15 SALAKATI BTPS POWERGRID 2.7 2 ACSR ZEBRA 16 MISA KATHALGURI POWERGRID 382.8 1 ACSR MOOSE 17 MARIANI KATHALGURI POWERGRID 162.9 1 TWIN MOOSE 18 SAMAGURI MISA POWERGRID 34.4 1 ACSR ZEBRA 19 SAMAGURI MISA POWERGRID 34.4 2 ACSR ZEBRA 20 MISA MARIANI POWERGRID 220.0 1 TWIN MOOSE 21 MISA DIMAPUR POWERGRID 121.9 1 ACSR ZEBRA 22 MISA DIMAPUR POWERGRID 121.9 2 ACSR ZEBRA 23 MISA KOPILI POWERGRID 72.8 1 ACSR ZEBRA 24 MISA KOPILI POWERGRID 72.8 2 ACSR ZEBRA 25 MISA KOPILI POWERGRID 75.9 3 AAAC ZEBRA 26 MISA BYRNIHAT MeECL 115.0 1 SINGLE ZEBRA 27 MISA BYRNIHAT MeECL 115.0 2 SINGLE ZEBRA 28 KATHALGURI TINSUKIA AEGCL 22.0 1 SINGLE ZEBRA 29 KATHALGURI TINSUKIA AEGCL 22.0 2 SINGLE ZEBRA


Page 26 of 97

LIST-3: 132 KV LINE DETAILS OF POWERGRID IN NORTH EASTERN REGION SR. NO. FROM TO UTILITY KM CKT CONDUCTOR

1 SALAKATI GELYPHU 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 ZIRO DAPORIJO POWERGRID 87.2 1 PANTHER 6 DAPORIJO ALONG POWERGRID 81.7 1 PANTHER

7 KHLEIHRIAT MeECL KHLEIHRIAT MeECL /

POWERGRID 5.5 1 ACSR PANTHER

8 KHLEIHRIAT MeECL KHLEIHRIAT MeECL /

POWERGRID 7.8 2 ACSR PANTHER

9 KHLEIHRIAT KHANDONG POWERGRID 42.5 1 ACSR PANTHER 10 KHLEIHRIAT KHANDONG POWERGRID 40.9 2 AAAC 11 KHANDONG HAFLONG POWERGRID 64.0 1 ACSR PANTHER 12 HAFLONG JIRIBAM POWERGRID 100.0 1 ACSR PANTHER 13 KHLEIHRIAT BADARPUR POWERGRID 76.6 1 AAAC 14 BADARPUR JIRIBAM POWERGRID 67.2 1 AAAC 15 JIRIBAM PAILAPOOL POWERGRID 15.0 1 PANTHER 16 JIRIBAM AIZWAL POWERGRID 170.0 1 ACSR PANTHER 17 AIZWAL KOLASIB POWERGRID 66.1 1 AAAC 18 KOLASIB BADARPUR POWERGRID 172.3 1 AAAC 19 BADARPUR KUMARGHAT POWERGRID 118.5 1 AAAC 20 KUMARGHAT AIZWAL POWERGRID 131.0 1 ACSR PANTHER 21 PANCHGRAM BADARPUR POWERGRID 1.0 1 AAAC 22 KUMARGHAT R C NAGAR POWERGRID 104.0 1 AAAC

23 AIZWAL AIZWAL ZUANGTUI POWERGRID 6.7 1 ACSR PANTHER

24 AIZWAL AIZWAL LUANGMUAL POWERGRID 7.0 1 ACSR PANTHER

25 JIRIBAM LOKTAK POWERGRID 82.4 2 ACSR PANTHER 26 LOKTAK IMPHAL POWERGRID 35.0 1 PANTHER

27 IMPHAL IMPHAL (MANIPUR) POWERGRID 1.5 1 PANTHER

28 IMPHAL DIMAPUR POWERGRID 168.9 1 ACSR PANTHER 29 DIMAPUR DOYANG POWERGRID 92.5 1 ACSR PANTHER 30 DIMAPUR DOYANG POWERGRID 92.5 2 ACSR PANTHER

31 BALIPARA GOHPUR (AEGCL) POWERGRID 100.0 1 SINGLE ZEBRA

32 R C NAGAR AGARTALA POWERGRID 8.4 1 ACSR PANTHER

33 R C NAGAR AGARTALA POWERGRID 8.4 2 ACSR PANTHER

34 KHANDONG KOPILI POWERGRID 10.9 1 ACSR PANTHER

35 KHANDONG KOPILI POWERGRID 10.9 2 ACSR PANTHER


Page 27 of 97

LIST-4: 132 KV LINE DETAILS OF NEEPCO IN NORTH EASTERN 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-5: 132 KV LINE DETAILS OF AEGCL IN NORTH EASTERN 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 10.0 1 PANTHER 4 DHALIGAON BTPS AEGCL 10.0 2 PANTHER 5 DHALIGAON NALBARI AEGCL 124.0 1 PANTHER 6 NALBARI RANGIA AEGCL 75.0 1 PANTHER 7 DHALIGAON BORNAGAR AEGCL 66.0 1 PANTHER

8 DHALIGAON ASHOK PAPER MILL AEGCL .... 1 PANTHER

9 BORNAGAR RANGIA AEGCL 75.0 1 PANTHER 10 RANGIA SISUGRAM AEGCL 33.0 1 PANTHER 11 RANGIA SIPAJHAR AEGCL …. 1 PANTHER 12 SIPAJHAR ROWTA AEGCL …. 1 PANTHER 13 SISUGRAM KAHELIPARA AEGCL 15.0 1 PANTHER 14 RANGIA KAHELIPARA AEGCL 43.0 1 PANTHER 15 KAHELIPARA NARENGI AEGCL 31.5 1 PANTHER 16 KAHELIPARA SARUSAJAI AEGCL 3.5 1 PANTHER 17 KAHELIPARA SARUSAJAI AEGCL 3.5 2 PANTHER 18 KAHELIPARA DISPUR AEGCL …. 1 PANTHER 19 NARENGI CTPS AEGCL …. 1 PANTHER 20 DISPUR CTPS AEGCL …. 1 PANTHER 21 CTPS BAGHJAP AEGCL …. 1 PANTHER 22 RANGIA ROWTA AEGCL 90.0 1 PANTHER 23 ROWTA DEPOTA AEGCL 60.0 1 PANTHER 24 DEPOTA B CHARIALI AEGCL 55.0 1 PANTHER 25 DEPOTA SAMAGURI AEGCL 35.0 1 PANTHER 26 SAMAGURI SANKARDEV NGR AEGCL 61.0 1 PANTHER 27 DIPHU SANKARDEV NGR AEGCL .... 1 PANTHER 28 B CHARIALI GOHPUR AEGCL 55.0 1 PANTHER 29 GOHPUR N LAKHIMPUR AEGCL 80.0 1 PANTHER 30 N LAKHIMPUR DHEMAJI AEGCL 80.0 1 PANTHER 31 TINSUKIA LEDO AEGCL 53.0 1 PANTHER 32 TINSUKIA DIBRUGARH AEGCL 53.0 1 PANTHER 33 DIBRUGARH NTPS AEGCL 67.0 1 PANTHER 34 DIBRUGARH MARAN AEGCL .... 1 PANTHER


Page 28 of 97

LIST-6: 132 KV LINE DETAILS OF MANIPUR IN NORTH EASTERN REGION SR. NO. FROM TO UTILITY KM CKT CONDUCTOR

1 LOKTAK NINGTHOUKONG MANIPUR 20.0 1 PANTHER 2 NINGTHOUKONG CHURACHANDPUR MANIPUR 60.0 1 PANTHER 3 KAKCHING YANGANGPOKPI MANIPUR 40.0 1 PANTHER 4 YANGANGPOKPI IMPHAL MANIPUR MANIPUR 45.0 1 PANTHER 5 NINGTHOUKONG IMPHAL MANIPUR MANIPUR 30.0 1 PANTHER 6 IMPHAL MANIPUR KARONG MANIPUR 60.0 1 PANTHER 7 LOKTAK RENGPANG MANIPUR 42.0 1 PANTHER 8 RENGPANG JIRIBAM MANIPUR 40.4 1 PANTHER LIST-7: 132 KV LINE DETAILS OF TSECL IN NORTH

35 LTPS NTPS AEGCL 30.0 1 PANTHER 36 LTPS NTPS AEGCL 30.0 2 PANTHER 37 TINSUKIA NTPS AEGCL 37.0 1 PANTHER 38 LTPS NAZIRA AEGCL .... 1 PANTHER 39 LTPS MARAN AEGCL .... 1 PANTHER 40 NAZIRA SIBSAGAR AEGCL .... 1 PANTHER 41 MARIANI LTPS AEGCL 70.0 1 PANTHER 42 MARIANI JORHAT AEGCL .... 1 PANTHER 43 MARIANI JORHAT AEGCL .... 2 PANTHER 44 JORHAT BOKAKHAT AEGCL .... 1 PANTHER 45 MOKOKCHUNG MARIANI AEGCL 50.0 1 PANTHER 46 MARIANI GOLAGHAT AEGCL 40.0 1 PANTHER 47 GOLAGHAT DIMAPUR AEGCL 80.0 1 PANTHER 48 BALIPARA DEPOTA AEGCL 25.0 1 ACSR PANTHER

49 RANGIA MOTONGA (BHUTAN) AEGCL 44.0 1 PANTHER


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 BARAMURA TSECL 25.0 1 PANTHER 5 BARAMURA AMBASA TSECL 36.0 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


Page 29 of 97

LIST-8: 132 KV LINE DETAILS OF NAGALAND IN NORTH EASTERN REGION

LIST-9: 132 KV LINE DETAILS OF MIZORAM IN NORTH EASTERN 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

LIST-10: 132 KV LINE DETAILS OF MeECL IN NORTH EASTERN REGION


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


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 0.25 1 PANTHER 12 EPIP II KILLING MeECL 0.25 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


Page 30 of 97

LIST-11: 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 40.0 2 WOLF 4 NAZIRA NTPS AEGCL .... 1 WOLF 5 NAZIRA NTPS AEGCL .... 2 WOLF 6 GOLAGHAT BOKAJAN AEGCL 64.0 1 WOLF 7 BOKAJAN DIPHU AEGCL 39.0 1 WOLF 8 DULLAVCHERRA PATHARKANDI AEGCL .... 1 WOLF 9 PATHARKANDI ADAMTILLA AEGCL .... 1 WOLF

10 DIMAPUR PURANA BAZAR NAGALAND 4.0 1 WOLF

11 DIMAPUR SINGRIJAN NAGALAND 5.4 1 WOLF 12 DIMAPUR GANESH

NAGAR NAGALAND 21.4 1 WOLF 13 DIMAPUR CHUMUKIDIMA NAGALAND 7.9 1 WOLF 14 MOKOKCHUNG ZUNHEBOTO NAGALAND 42.2 1 WOLF 15 MOKOKCHUNG TULI NAGALAND 56.3 1 WOLF 16 TULI NAGINIMORA NAGALAND 33.0 1 WOLF 17 NAGINIMORA TIZIT NAGALAND 30.0 1 WOLF 18 TIZIT MON NAGALAND 40.0 1 WOLF 19 MOKOKCHUNG TUENSANG NAGALAND 50.4 1 WOLF 20 TUENSANG KHIPHIRE NAGALAND 55.7 1 WOLF 21 KHIPHIRE LIKHIMRO NAGALAND 35.0 1 WOLF

22 ROKHIA RABINDRA NAGAR TSECL 23.0 1 WOLF

17 UMIUM ST I UMIUM MeECL 13.0 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 8.9 1 PANTHER

25 NEHU KHLEIHRIAT MeECL MeECL 52.6 1 PANTHER

26 NEIGHRIMS KHLEIHRIAT MeECL MeECL 64.8 1 PANTHER

27 KHLEIHRIAT MeECL LUMSNONG MeECL 25.3 1 PANTHER

28 KHLEIHRIAT MeECL LESHKA MeECL 23.0 1 PANTHER

29 KHLEIHRIAT MeECL LESHKA MeECL 23.0 2 PANTHER


Page 31 of 97

23 RABINDRA NAGAR BELONIA TSECL 38.0 1 WOLF

24 BELONIA BAGAFA TSECL 15.0 1 WOLF 25 BAGAFA SATCHAND TSECL 36.0 1 WOLF 26 SATCHAND SABROOM TSECL 15.0 1 WOLF 27 BAGAFA UDAIPUR TSECL 29.0 1 WOLF 28 UDAIPUR GOKULNAGAR TSECL 31.0 1 WOLF 29 GUMTI UDAIPUR TSECL 45.0 1 WOLF 30 GOKULNAGAR BADARGHAT TSECL 12.0 1 WOLF 31 BADARGHAT ROKHIA TSECL 24.0 1 WOLF 32 BADARGHAT AGARTALA TSECL 8.0 1 WOLF 33 AMARPUR GUMTI TSECL 30.0 1 WOLF 34 TELIAMURA AMARPUR TSECL 35.0 1 WOLF 35 BARAMURA TELIAMURA TSECL 8.0 1 WOLF 36 KOLASIB VAIRENGTE MIZORAM 35.0 1 WOLF

LIST-12: 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 5 MISA KATHALGURI POWERGRID 382.9 1 50 NIL 6 MISA MARIANI POWERGRID 220 1 50 NIL

LIST-13: 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 POWERGRID 218 1 63 63 2 BONGAIGAON BINAGURI POWERGRID 218 2 63 63


ENT AND VOLTAGE CON


Page 32 of 97

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Page 33 of 97

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NOTE: S

WITCHABLE: LINE REACTORS W

HICH CAN BE OPERATED ON LINE AS A BUS REACTOR.

CONVERTIBLE: LINE REACTORS W

HICH CAN BE OPERATED UPON ONLY W

HEN LINE IS

IN OUT CONDITION.

FIXED : LINE REACTORS W

HICH ARE FIXED AND CANNOT BE OPERATED UPON AS A BUS REACTOR


Page 34 of 97

LIST-16: BUS REACTORS IN NORTH EASTERN REGION

SR. NO. UTILITY INSTALLED AT (STATION) KV RATING STATUS

MVAR MAKE 1 POWERGRID BALIPARA 400 50 BHEL IN SERVICE 2 POWERGRID BONGAIGAON 400 2 X 50 BHEL IN SERVICE 3 POWERGRID MISA 400 50 BHEL IN SERVICE 4 ASSAM MARIANI 220 2 X 12.5 .... IN SERVICE 5 ASSAM SAMAGURI 220 2 X 12.5 .... IN SERVICE 6 POWERGRID AIZWAL 132 20 .... IN SERVICE 7 POWERGRID KUMARGHAT 132 20 .... IN SERVICE 8 TRIPURA DHARMANAGAR 132 2 X 2 .... IN SERVICE

LIST-17: TERTIARY REACTORS ON 33 KV SIDE OF 400/220/33 KV ICTS IN NORTH EASTERN REGION

SR. NO. UTILITY INSTALLED AT (STATION)

INSTALLED ON

RATING STATUS

MVAR MAKE

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 35 of 97

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 generate 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 proportional to the square of the

load current, thus generating reactive power when it is most needed whereas in shunt capacitors it is proportional to the square of the voltage. Series capacitors compensation is usually applied for long transmission lines and transient stability improvement. Series compensation reduces net transmission line inductive reactance. The reactive generation I2XC compensates for the reactive consumption I2X of the transmission line. This is a self-regulating nature of series capacitors. 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 36 of 97

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

capacitors are widely used in distribution systems. For the same voltage improvement, the rating of a shunt capacitor will be higher than that of a series capacitor. Thus a series capacitor stiffens the system, which is especially beneficial for starting large motors from 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 for reduction of technical losses. The agricultural load mainly consists of irrigation pump motors. The PF of pump motors are generally below 0.6, which means the total reactive power demand of the system is high. The reactive power demand can be reduced by installation of suitable capacitors. However, proper maintenance has to be adopted to keep the system in order. In view of the maintenance problem, reactive compensation technique could be installed at the distribution transformer centers. Care has to be taken that it does not lead to over voltage problems during the off peak hours. To avoid this there should be switch off arrangement in the capacitor bank. The optimum allocation of LT capacitors at distribution substation by minimizing a cost function, which includes loss cost in the beneficiary system and the annual cost of the capacitor bank. The reactive compensation can also be carried out at the primary distribution feeders (11 KV) lines. The optimum number, size and location 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 adjusting transformer


Page 37 of 97

taps to the extent available and switching of circuits/ capacitors/ reactors and other operational steps. SLDC will instruct generating stations to regulate MVAr generation within their declared parameters. SLDC shall also instruct Distribution Licensees to regulate demand, if necessary.

LIST-18: SUBSTATIONS IN NER

AGENCY 400KV 220 KV 132 KV & 66 KV TOTAL POWER GRID 3 2 9 14 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

TOTAL 3 9 70 82

LIST-19: SHUNT CAPACITOR DETAILS OF NORTH EASTERN REGION

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

1 MeECL MAWLAI 33 KV BUS BAR 10 2 AEGCL BAGHJAB 33 KV BUS BAR 2X5 3 AEGCL KAHELIPARA 33 KV BUS BAR 3X5 4 AEGCL BARANAGAR 33 KV BUS BAR 2X5 5 AEGCL GOSAIGAON 33 KV BUS BAR 1X10 6 AEGCL GAURIPUR 33 KV BUS BAR 1X5 7 AEGCL RUPAI 33 KV BUS BAR 1X5 8 AEGCL MARGHERITA 33 KV BUS BAR 2X5 9 AEGCL N LAKHIMPUR 33 KV BUS BAR 1X5 10 AEGCL DULLAVCHERRA 33 KV BUS BAR 1X5 11 AEGCL DEPOTA 33 KV BUS BAR 2X5 12 AEGCL SARUSAJAI 33 KV BUS BAR 2X10 13 AEGCL ROWTA 33 KV BUS BAR 1X15 14 AEGCL DIPHU 33 KV BUS BAR 2X5 15 AEGCL DIBRUGARH 33 KV BUS BAR 2X5 16 AEGCL S NAGAR 33 KV BUS BAR 2X5

Total Capacity of NER

160


Page 38 of 97

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-distance 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 primary 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 secondary coil at various points, the ratio between the primary and secondary voltage can be adjusted. Transformer taps can be either fixed or adjustable under load through the use of a load-tap changer (LTC). Tap capability is selected for each application during transformer design.

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 secontransformer. The control method is based on a which means that a control pulse, one at a time, wload tap-changer mechanism to move it up or down

4.1.5 The pulse is generated by the AVR whenever the m

given time, deviates from the set reference value bdead band (i.e. degree of insensitivity). Time delay

Fig 13. Switching p
rinciple of LTC
dary side of the power step-by-step principle ill be issued to the on- by one position.

easured voltage, for a y more than the preset is used to avoid


Page 39 of 97

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

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

differs from that provided by reactive sources. Transformer taps can force voltage up (or down) on one side of a transformer, 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 other side.

4.1.7 The reactive power consumption of a transformer at rated current is

within the range 0.05 to 0.2 p.u. based on the transformer ratings. Fixed taps are useful when compensating for load growth and other long-term shifts in system use. LTCs are used for more-rapid adjustments, such as compensating for the voltage fluctuations associated with the daily load cycle. While LTCs could potentially provide rapid voltage control, their performance is normally intentionally degraded. With an LTC, tap changing is accomplished by opening and closing contacts 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 by Regional operation. The SLDC shall optimise voltage management by adjusting transformer taps to the extent available and switching of circuits/ capacitors/ reactors and other operational steps. SLDC will instruct generating stations to regulate MVAr generation within their declared parameters. SLDC shall also instruct Distribution Licensees to regulate demand, if necessary.


Page 40 of 97

LIST-20: ICT DETAILS OF POWERGRID IN NORTH EASTERN REGION

LIST-21: ICT DETAILS OF NEEPCO IN NORTH EASTERN REGION

SL. NO. SUBSTATION AGENCY ICT

NO. MVA KV RATIO MAKE TT NT

STEP PT

%AGE KV

1 DOYANG NEEPCO 01 5 132/33 KV …. …. …. …. …. 02

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

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

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

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

6 KOPILI NEEPCO 01 160 220/132 KV …. …. …. …. …. 13

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

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



STEP PT

%AGE KV

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

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

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

6 NIRJULI POWERGRID 01 16 132 /33 kV

KANOHAR ELECT. 17 9 1.25 1.65 09

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

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

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

10 ZIRO POWERGRID 01 15 132 /33 kV

AREVA /ALSTOM 17 9 1.25 1.65 02


Page 41 of 97

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



STEP PT

%AGE KV

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

LIST-23: ICT DETAILS OF ARUNACHAL PRADESH IN NORTH EASTERN REGION

LIST-24: ICT DETAILS OF AEGCL IN NORTH EASTERN REGION



STEP PT

%AGE KV

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

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

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



STEP PT

%AGE KV

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 01 100 220/13

2 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 42 of 97

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

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

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


Page 43 of 97

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 …. …. …. …. …. ….

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

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


Page 44 of 97

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

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

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


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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-25: ICT DETAILS OF MANIPUR IN NORTH EASTERN REGION



STEP PT

%AGE KV

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-26: ICT DETAILS OF MEGHALAYA IN NORTH EASTERN REGION



STEP PT

%AGE KV

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

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

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

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

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

6 KHLIERIAT 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-27: ICT DETAILS OF MIZORAM IN NORTH EASTERN REGION



STEP PT

%AGE KV

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-28: ICT DETAILS OF NAGALAND IN NORTH EASTERN REGION



STEP PT

%AGE KV

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-29: ICT DETAILS OF TSECL IN NORTH EASTERN REGION



STEP PT

%AGE KV

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-30: TRANSMISSION/TRANSFOMATION/VAR COMPENSATION

CAPACITY OF NER

TRANSMISSION LINE (CKT KM) AGENCY 440 KV 220 KV 132 KV

POWERGRID 1102 1315 1774 STATES 0 1264 3961 TOTAL 1102 2579 5735

TRANSFORMATION CAPACITY (MVA) POWERGRID/NEEPCO 1344.99/780 MVA

STATES 2589 MVA REACTIVE COMPENSATION (MVAR)

POWERGRID/NEEPCO 1042/100 MVAR STATES 54 MVAR

CAPACITIVE COMPENSATION – 175 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 transmission line and in some applications, multi-terminal HVDC with interconnected DC transmission lines. Back-to-Back DC and HVDC Light are specific types of HVDC systems. HVDC Light uses new cable and converter technologies and is economical at lower power levels than traditional HVDC.

5.2 HVDC CONFIGURATION

5.2.1 Bipolar

In bipolar transmission a pair of conductors is used, each at a high potential with respect to ground, in opposite polarity. 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 earth-return. This reduces earth return loss and environmental effects.

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

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

• In very adverse terrain, the second conductor may be carried on an independent set of transmission towers, so that some power may continue to be transmitted even if one line is damaged.


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A bipolar system may also be installed with a metallic earth return conductor. Bipolar systems may carry as much as 3,200 MW at voltages of +/-600 kV (viz., 2500 MW +/- 500 KV TALCHER – KOLAR HVDC link in INDIA connecting NEW GRID to SR GRID ) Submarine cable installations initially commissioned as a monopole may be upgraded 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 plant in which both static inverters and rectifiers are in the same area, usually in the same building. The length of the direct current line is kept as short as possible. HVDC back-to-back stations are used for

• Coupling of electricity mains of different frequency (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, HVDC 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 selected freely at HVDC back-to-back stations because of the short conductor 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 consists of a rectifier and an inverter. The rectifier side of the HVDC link is equivalent to a load consuming positive real and reactive power and the inverter side of the HVDC link as a generator providing positive real power and negative reactive power (i.e. absorbing positive reactive power).

5.2.4 Thyristor based HVDC converters always consume reactive power when

in operation. A DC line itself does not require reactive 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, draw 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.

http://en.wikipedia.org/wiki/Traction_current_converter_plant


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

met by providing appropriate reactive power in the station. For those reason reactive power compensations devices are used 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 HVDC converters. AC

harmonics are injected into the AC system and DC harmonics are injected into the DC line. These harmonics have the following harmful effects:

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

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

resulting in over voltages. • Instability of converter controls.

5.2.7 Harmonics arefilters are used

• AC• DC• Hi

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

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normally minimized by using filters. The following types of :

filters. filters.

gh frequency filters.


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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 reactive power required for satisfactory operation of converters and also partly injects reactive power into the system.

DC Filters DC filters are similar to AC filters. A DC filter is connected between pole bus and neutral bus. It diverts DC harmonics to earth and prevents them from entering DC lines. Such a filter does not supply 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 radio interference noise in the mega hertz range of frequencies. High frequency (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 operation of converters and also to boost the AC side voltages. AC harmonic filters which help in minimizing harmonics also provide reactive power partly. Additional supply may be obtained from shunt (switched) capacitor 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 for commissioning matching with Subansiri Lower HEP in 2012-13. The transmission line would be for 6000 MW capacity and HVDC terminal capacity would be 3000 MW between Bishwanath Chariali and Agra. In the second phase, for transmission of power from hydro projects at Sikkim and Bhutan pooled at Alipurduar, another 3000 MW terminal modules would be added between Siliguri and Agra. It is envisaged to take-up the proposed 800kV, 6000MW HVDC bi-pole line from Bishwanath Chariali to 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 response to system parameter

change, and higher stability of system have stimulated the development of the Flexible AC Transmission systems (FACTS). Based on the success of research in power electronics switching devices and advanced control technology, FACTS has become the technology of choice in voltage control, reactive/active power flow control, transient and steady-state stabilization that improves the operation and functionality 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 capacity and fuel consumption, and minimize the operation cost. The power electronics-based switches in the functional blocks of FACTS can usually be operated repeatedly and the switching time is a portion of a periodic cycle, which is much shorter than the conventional mechanical switches.

6.1.3 The advance of semiconductors increases the switching frequency and

voltage-ampere ratings of the solid switches and facilitates the applications. For example, the switching frequencies of Insulated Gate Bipolar Transistors (IGBTs) are from 3 kHz to 10 kHz which is several hundred times the utility frequency of power system (50~60Hz). Gate turn-off thyristors (GTOs) have a switching frequency lower than 1 kHz, but the voltage and current rating can reach 5-8 kV and 6 kA 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 capacitive or inductive current so as to maintain or control specific parameters 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 thyristors realize SVC

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


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

by two parallel, reverse-connected thyristors. TCR is controlled with proper firing angle input to operate in a continuous manner, while TSR is controlled without firing angle control which results 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)

Converter-based Compensators which are usuallysource 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 topobased on VSI and CSI (b)

Fig 15. Static VAR CTCR/TSR, TSC, FC aResistor

ompensators (SVC): nd Mechanically Switched

is one of the key based on the voltage

logies: (a) STATCOM STATCOM with storage


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

The switching device of a VSI is usually a gate turn-off device paralleled by a reverse diode; this function endows the VSI advanced controllability.

6.3.3 Various combinations of the switching devices and appropriate topology

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

6.3.4 STATCOM has much better dynamic performance than conventional

reactive power compensators like SVC. The gate turn-off ability shortens the dynamic response time from several utility period cycles to a portion of a period cycle. STATCOM is also much faster in improving 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- connected FACTS controllers can also be divided into either impedance 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 function is to convert fuel (or other

energy resource) into electric power. Almost all generators also have considerable control over their terminal voltage and 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 increasing the magnetic field to

raise the generator’s terminal voltage. Increasing the magnetic field requires increasing the current in the rotating field winding. This too is current limited, resulting in the field-heating limit shown in the figure. Absorption of reactive power is limited by the magnetic-flux pattern in the stator, which results in excessive heating of the stator-end iron, the core-end heating limit. The synchronizing torque is also reduced when absorbing large amounts of reactive power, which can 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 turbine) is usually designed

with less capacity than the electric generator, resulting in the prime-mover limit in Fig. 18. The designers recognize that the generator will be producing reactive power and supporting system voltage 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 these limits would require

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

7.1.7 Control over the reactive output and the terminal voltage of the generator

is provided by adjusting the DC current in the generator’s rotating field. Control can be automatic, continuous, and fast. The inherent characteristics of the generator help maintain system 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 declines, the generator will inject reactive power into the power system, tending 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 behavior by driving the field

current in the appropriate direction to obtain the desired system voltage. Because most of the reactive limits are thermal limits associated with large pieces of equipment, significant short-term extra 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 network-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 used to provide voltage support to the power system as they provide mechanical power to their load. Some combustion turbines and hydro units are designed to allow the generator to operate without its mechanical power 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 exclusively to provide reactive

support are called synchronous condensers. Synchronous condensers have all of the response speed and controllability advantages of generators without the need to construct the rest of the power plant (e.g., fuel-handling equipment and boilers). Because they are rotating machines with moving parts and auxiliary systems, they may require significantly more maintenance than static alternatives. They also consume real power equal to about 3% of the machine’s reactive-power rating. 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 in 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 allowed to operate at leading power factor as per the respective capability curve.

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

cooling. This is particularly true of hydrogen cooled generators where cooling gas pressure affects both the real and reactive power capability

Table 5. List of units in NER required to be normally 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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8 CONCLUSION 8.1 Generators, synchronous condensers, SVCs, and STATCOMs all provide

fast, continuously controllable reactive support and voltage control. LTC transformers provide nearly continuous voltage control but they are slow because the transformer moves reactive power from one 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 only 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 of an SVC, is proportional to the square of the terminal voltage. STATCOMs provide more support under low-voltage conditions than capacitors 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., generators and synchronous

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

8.4 Generators have extremely high capital costs because 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 because they involve real-power losses. Finally, because generators have other uses, they experience opportunity costs when called upon to simultaneously provide high levels of both reactive and real power.

8.5 Synchronous condensers have the same costs as generators but,

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


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

interconnected transmission systems is well understood from a technical perspective. Three objectives dominate reactive-power management. First, maintain adequate voltages throughout the transmission system under current and contingency conditions. Second, minimize congestion of real-power flows. Third, minimize real-power losses.

9.2 This process must be performed centrally because it requires a

comprehensive view of the power system to assure that control is coordinated. System operators and planners use sophisticated computer models to design and operate the power system reliably and economically. Central control by rule works well but may not be the most technically and economically effective means.

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

restructured/regulated industry than for vertically integrated utilities. While it may be sufficient to measure only the response of the system in aggregate for a vertically integrated utility, determining individual generator performance will be critical in a competitive environment.

9.4 While it reduces or eliminates opportunity costs by providing sufficient

capacity, it can waste capital. When an investor is considering construction of new generation, the amount of reactive 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. But their high capital costs limit their use. If these devices could participate 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 market provision of the bulk of the reactive support. In other locations, existing 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 within each region would be a

useful contribution to restructuring. System planners and operators need to work closely together during the design of new facilities and modification of existing facilities. Planners must design adequate reactive support into the system to provide satisfactory voltage profiles during normal and contingency operating conditions. Of particular importance is sufficient dynamic support, such as the reactive output of generators, which can supply additional reactive power during contingencies.

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

able to tell when and if the operational reactive resources are sufficient. Operators must remain cognizant of any equipment outages or problems that could reduce the system’s static or dynamic reactive 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 contained, 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 different, perhaps conflicting, goals. In particular, the owners of generating resources will be driven, in competitive generation markets, to maximize the earnings from their resources. They will not be willing to sacrifice revenues from the sale of real power to produce reactive power unless appropriately 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 transmission rates that they are allowed to charge.

9.11 Failure to appropriately compensate those entities that provide voltage-

control services could lead to serious reliability problems and severe constraints on inter regional links and other congested areas as TTC (Total Transfer Capability) has a voltage limit function as a baggage with it which is directly linked to var compensation. With dynamic ATC’s (Available Transfer capability), Var compensation if not seriously thought of may have serious commercial implications in time to come due to the amount of bulk power trading happening across the country 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 (Technical 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 connected to the grid shall comply with the following requirements besides the general connectivity conditions given in the regulations and 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 of 200 MW and above and hydro units having rated capacity of 100 MW and above, the following facilities would be provided at the time of renovation and modernization.

(1) Every generating unit shall have Automatic Voltage

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 general policy

(a) The planning criterion are based on the security 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 of

withstanding and be secured against the following contingency outages


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a. without necessitating load shedding or rescheduling

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 be 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 assuming a pre-contingency system depletion (Planned outage) of another 220 kV D/C line or 400 kV S/C line in another 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 shall also be maintained within voltage limits specified

(e) CTU shall carry out planning studies for Reactive 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 of Connectivity, Long-term Access and Medium-term Open Access in inter-state Transmission and related matters) Regulations, 2009.

10.2.2 As per Sec 4.6.1 of IEGC, Important Technical Requirements for

Connectivity to the Grid:

Reactive Power Compensation

a) Reactive Power compensation and/or other facilities, 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 within the specified range.

b) The person already connected to the grid shall also provide

additional reactive compensation as per the quantum and time frame decided by respective RPC in consultation with RLDC. The Users and STUs shall provide information to RPC and RLDC regarding the installation and healthiness of the reactive compensation equipment on regular basis. RPC shall regularly monitor the status in this regard.

10.2.3 In chapter 5 of IEGC operating code for regional grids:

5.2(k) All generating units shall normally have their automatic

voltage regulators (AVRs) in operation. In particular, if a generating unit of over fifty (50) MW size is required 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 owner 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 considered necessary.

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

facilitate identification, installation and commissioning of System Protection Schemes (SPS) (including inter-tripping and run-back) in the power system to operate the transmission system closer to their limits and to protect against situations such as voltage collapse and cascade tripping, tripping of important corridors/flow-gates etc.. Such schemes would be finalized by the concerned RPC forum, and shall always be kept in service. If any SPS is to be taken out of service, permission of RLDC shall be obtained indicating reason and duration of anticipated outage from service.

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

possible measures to ensure that the grid voltage always 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 Power & Voltage Control:

1. Reactive power compensation should ideally be provided

locally, by generating reactive power as close to the reactive power consumption as possible. The Regional Entities except Generating Stations are therefore expected to provide local VAr compensation/generation such that they do not draw VArs from the EHV grid, particularly 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 is 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 own 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 between the Regional Entity, except Generating Stations, and the regional pool account for VAr interchanges. This rate shall be escalated at 0.5paise/kVArh per year thereafter, unless otherwise revised by the Commission.

3 Notwithstanding the above, RLDC may direct a Regional

Entity except Generating Stations to curtail its VAr drawal/injection in case the security of grid or safety of any equipment is endangered.

4. In general, the Regional Entities except Generating 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 voltage is above 105%. ICT taps at the respective drawal points may be changed to control the VAr interchange as per a Regional Entity except Generating Stations’s request to the RLDC, but only at reasonable intervals.

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

throughout the grid shall be carried out as per instructions 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 connected to

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

7. VAr exchange directly between two Regional Entities

except Generating Stations on the interconnecting lines 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 grid. Accordingly, the management/control and commercial handling of the VAr exchanges on such lines shall be as per following provisions, on case-by-case basis:


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i) The two concerned Regional Entities except Generating

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 Generating

Stations may mutually agree to adopt a payment rate/scheme for VAr exchanges between them identical to or at variance from that specified by CERC for VAr 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 concerned

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 shall be applied. The per kVArh rate shall be as specified by CERC for VAr exchanges with ISTS.

iv) The computation and payments for such VAr exchanges

shall be effected as mutually agreed between the two Beneficiaries.

10.3 THE AEGCL GAZETTE, EXTRAORDINARY, FEBRUARY 10, 2005

10.3.1 IN CHAPTER 9: FREQUENCY AND VOLTAGE MANAGEMENT 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 contributing towards effective control of the system frequency and managing the grid voltage.

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

Eastern Regional Grid and NERLDC has the overall responsibility of the integrated operation of the North-Eastern Regional Power System. The constituents of the Region are required to follow the instructions of NERLDC 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 Generation/Export and

hold reserves of active and reactive power within their


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

(d) System voltages levels can be affected by Regional

operation. The SLDC shall optimise voltage management by adjusting transformer taps to the extent available and switching of circuits/ capacitors/ reactors and other operational steps. SLDC will instruct generating stations to regulate MVAr generation within their declared parameters. 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 levels 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 and shall normally be regulated within the limits prescribed in IEGC Clause 4.6(b). As a constituent of North-Eastern Region, the SLDC shall make all possible efforts to ensure that grid frequency remain 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-generation balance conditions of the system, matching of available generation with load, is the only option for maintaining frequency within the desired limits. Basically, two situations arise, viz., a surplus situation and a deficit situation. The automatic mechanisms available for adjustment of load/generation are (i) Free governor action; (ii) Maintenance of spinning reserves and (iii) Under-frequency relay actuated shedding. These measures are essential elements of system security. SLDC shall ensure that Users of the State Grid comply with 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 mechanism 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 permissible range. Such instructions may include dispatch instruction to SSGS and/or instruction to Distribution Licensees and Open access customers to reduce load demand by appropriate manual and/or automatic 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-ordination with NERLDC, to arrest the rising frequency and restore frequency within permissible range through backing down hydel generation and thermal generation to the level not requiring oil support. SLDC shall also issue instructions to Distribution Licensees and 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 this schedule. SLDC shall also monitor reactive power drawal and availability of capacitor banks. Generating Stations within AEGCL shall follow the dispatch instructions issued by SLDC.Distribution Licensees and Open access customers shall co-operate with SLDC in managing load & reactive power drawal on instruction from SLDC as required.

10.3.1.8 (9.8) Voltage Management

(a) Users using the Intra State transmission system shall make all possible efforts to ensure that the grid voltage always remains within the limits specified in IEGC at clause 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 predict 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 SLDC shall

Nominal Maximum Minimum

400 420 380

220 245 198

132 145 122


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instruct SSGS to maintain specified voltage level at interconnecting points. SLDC and AEGCL Gridco shall co-ordinate with the Distribution Licensees to determine voltage level at the interconnection points. SLDC shall continuously monitor 400/220/132kV voltage levels at strategic sub-stations to control System voltages.

(c) SLDC in close coordination with NERLDC shall take

appropriate measures to control System voltages which may include but not be limited to transformer tap changing, capacitor / reactor switching including capacitor switching by Distribution Licensees at 33 kV substations, operation of Hydro unit as synchronous condenser and use of MVAr reserves with SSGS within technical limits agreed to between AEGCL Gridco and Generators. Generators shall inform SLDC of their reactive reserve capability promptly on request.

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

capability curves for all Generating Units, as detailed in Chapter 5.indicating any restrictions, to allow accurate system studies and effective operation of the Intra State transmission system. CPPs shall similarly furnish the net reactive capability that will be available for Export to / Import from Intra State transmission system.

(e) Distribution Licensees and Open access customers shall

participate in voltage management by providing Local VAR compensation (as far as possible in low voltage system close to load points) such that they do not depend upon EHV grid for reactive support.

10.3.1.9 (9.9) General

Close co-ordination between Users and SLDC, AEGCL Gridco 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 IREDA by Devki energy

consultancy pvt. ltd. 2. NERPC progress report August, 2010. 3. Document on MeSEB capacity building and training document 4. Manual on Transmission Planning Criteria, CEA, Govt. of India, June 1994 5. Indian Electricity Grid Code, CERC, India, 2010 6. The Central Electricity Authority (Technical Standard 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 power supply and consumption, staff

report, FERC, Docket No. AD05-1-000, February 4, 2005 10. Proceedings of workshop on grid security & management 28th and 29th 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”, McGraw-Hill, 1994. 14. THE AEGCL GAZETTE, EXTRAORDINARY, FEBRUARY 10, 2005


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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

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