reactive power management & voltage control in north ... - NERLDC

One Nation. One Grid

REACTIVE POWER MANAGEMENT & VOLTAGE CONTROL IN NORTH EASTERN REGION

POWER SYSTEM OPERATION CORPORATION LIMITED (A wholly owned subsidiary of Powergrid) (A GOVT. OF INDIA UNDERTAKING)

NORTH EASTERN REGIONAL LOAD DESPATCH CENTRE SHILLONG Edition

November 2012 Prepared by: System Operation - I department

REACTIVE POWER MANAGEMENT AND VOLTAGE CONTROL IN NORTH EASTERN REGION

CONTENTS EXECUTIVE SUMMARY

5

1

6 6 8 10 11 12 13 14 17 20

Reactive Power Management and Voltage Control 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9

2

3

4

5

6

Introduction Analogy of Reactive Power Understanding Vectorially Voltage Stability Voltage Collapse Proximity to Instability Reactive reserve margin NER GRID – OVERVIEW Reliability improvement due to local voltage regulation

Transmission Lines and Reactive Power Compensation

21

2.1 2.2 2.3 2.4

21 22 22 23

Introduction Surge impedance loading (SIL) Shunt compensation in line Line loading as function of line length and compensation

Series and Shunt Capacitor Voltage Control

37

3.1 3.2 3.3

37 38 38

Introduction MeSEB capacity building and training document suggestion THE ASSAM GAZETTE, EXTRAORDINARY, FEBRUARY 10, 2005

Transformer Load Tap Changer and Voltage Control

41

4.1 4.2

41 42

Introduction THE ASSAM GAZETTE, EXTRAORDINARY, FEBRUARY 10, 2005

HVDC and Voltage Control

53

5.1 5.2 5.3 5.4

53 53 56

Introduction HVDC Configuration Reactive power source ”Inter-regional Transmission system for power export from NER to NR/WR”

56

FACTS and Voltage Control

57

6.1 6.2 6.3 6.4

57 57 58 59

Introduction Static Var Compensator (SVC) Converter-based Compensator Series-connected controllers

Page 1 of 100


7

Generator Reactive Power and Voltage Control

60

7.1 7.2

60 62

Introduction Synchronous condensers

8

CONCLUSION

87

9

SUMMARY

88

10

Statutory Provisions for Reactive Power Management and Voltage Control

90

10.1

90

10.2 10.3

11.

Provision in the Central Electricity Authority (Technical Standard for connectivity to the grid) Regulations 2007 [8]: Provision in the Indian Electricity Grid Code (IEGC), 2010 THE ASSAM GAZETTE, EXTRAORDINARY, FEBRUARY 10, 2005

Bibliography

90 95 99

Details of List LIST-1: LIST-2: LIST-3: LIST-4: LIST-5: LIST-6: LIST-7: LIST-8: LIST-9: LIST-10:

400 KV LINE DETAILS OF POWERGRID IN NORTH EASTERN REGION 400 KV LINE (CHARGED AT 220 KV) DETAILS OF POWERGRID IN NORTH EASTERN REGION 220 KV LINE DETAILS OF POWERGRID IN NORTH EASTERN REGION 132 KV LINE DETAILS OF POWERGRID IN NORTH EASTERN REGION 132 KV LINE DETAILS OF NEEPCO IN NORTH EASTERN REGION 132 KV LINE DETAILS OF AEGCL IN NORTH EASTERN REGION 132 KV LINE DETAILS OF MANIPUR IN NORTH EAST 132 KV LINE DETAILS OF TSECL IN NORTH EASTERN REGION 132 KV LINE DETAILS OF NAGALAND IN NORTH EASTERN REGION 132 KV LINE DETAILS OF MIZORAM IN NORTH EASTERN REGION

25 25 26 27 27 28 29 29 30

LIST-11:

132 KV LINE DETAILS OF MeECL IN NORTH EAST

30

LIST-12: LIST-13: LIST-14: LIST-15: LIST-16: LIST-17:

132 KV LINE DETAILS OF ARUNACHAL PRADESH IN NORTH EAST 66 KV LINE DETAILS OF NORTH EASTERN REGION SHUNT COMPENSATED LINES IN NORTH EASTERN REGION SHUNT COMPENSATED INTER – REGIONAL LINES IN NORTH EASTERN REGION INTER-STATE LINE DETAILS OF NORTH EASTERN REGION FIXED, SWITCHABLE AND CONVERTIBLE LINE REACTORS IN NORTH EASTERN REGION BUS REACTORS IN NORTH EASTERN REGION TERTIARY REACTORS ON 33 KV SIDE OF 400/220/33 KV ICTS IN NORTH EASTERN REGION SUBSTATIONS IN NER SHUNT CAPACITOR DETAILS OF NORTH EASTERN REGION ICT DETAILS OF POWERGRID IN NORTH EASTERN REGION ICT DETAILS OF NEEPCO IN NORTH EASTERN REGION ICT DETAILS OF NHPC IN NORTH EASTERN REGION

31 31 32 33 34

LIST-18: LIST-19: LIST-20: LIST-21: LIST-22: LIST-23: LIST-24:

Page 2 of 100

25

35 36 36 39 40 43 43 44

REACTIVE POWER MANAGEMENT AND VOLTAGE CONTROL IN NORTH EASTERN REGION LIST-25: LIST-26: LIST-27: LIST-28: LIST-29: LIST-30: LIST-31: LIST-32: LIST-33:

ICT DETAILS OF ARUNACHAL PRADESH IN NORTH EASTERN REGION ICT DETAILS OF AEGCL IN NORTH EASTERN REGION ICT DETAILS OF MANIPUR IN NORTH EASTERN REGION ICT DETAILS OF MeECL IN NORTH EASTERN REGION ICT DETAILS OF MIZORAM IN NORTH EASTERN REGION ICT DETAILS OF NAGALAND IN NORTH EASTERN REGION ICT DETAILS OF TSECL IN NORTH EASTERN REGION ICT DETAILS OF OTPC IN NORTH EASTERN REGION TRANSMISSION/TRANSFORMATION/VAR COMPENSATION CAPACITY OF NER

44 44 49 49 50 51 51 52 52

List of Figures Fig1. Fig2. Fig3. Fig4. Fig5. Fig6. Fig7. Fig8. Fig9. Fig10. Fig11. Fig12. Fig13. Fig14. Fig15. Fig16. Fig17. Fig18.

Voltage and Current waveforms Power Triangle Boat pulled by a Horse Direction of pull Vector representation of the analogy LABYRINTSPEL Vector representation Time frames for voltage stability phenomena PV curve and voltage stability margin under different conditions Average cost of reactive power technologies NER grid map SIL vs. Compensation Switching principles of LTC HVDC fundamental components Static VAR Compensators (SVC) STATCOM topologies Series-connected FACTS controllers D-Curve of a typical Generator

6 7 8 8 8 9 10 13 14 16 17 23 41 55 58 58 59 60

Annexure: Capability Curve of generating machines of NER 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

LTPS UNIT 5, 6 & 7 CAPABILITY CURVE NTPS UNIT 1, 2 & 3 CAPABILITY CURVE NTPS UNIT 4 CAPABILITY CURVE NTPS UNIT 6 CAPABILITY CURVE LTPS CAPABILITY CURVE NTPS CAPABILITY CURVE UMIUM ST I CAPABILITY CURVE UMIUM STAGE II CAPABILITY CURVE UMIUM STAGE III CAPABILITY CURVE UMIUM STAGE IV CAPABILITY CURVE AGBPP UNIT 5, 6, 7, 8 & 9 CAPABILITY CURVE AGBPP UNIT 1, 2, 3 & 4 CAPABILITY CURVE AGTPP CAPABILITY CURVE DOYANG HEP UNIT 1 CAPABILITY CURVE KHANDONG HEP UNIT 2 CAPABILITY CURVE KOPILI HEP UNIT 1 CAPABILITY CURVE KOPILI HEP UNIT 2 CAPABILITY CURVE KOPILI HEP ST II CAPABILITY CURVE RANGANADI HEP CAPABILITY CURVE

Page 3 of 100

63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81

REACTIVE POWER MANAGEMENT AND VOLTAGE CONTROL IN NORTH EASTERN REGION 20 21 22 23 24

LOKTAK HEP CAPABILITY CURVE ROKHIA UNIT 3, 4 & 6 CAPABILITY CURVE ROKHIA & BARAMURA CAPABILITY CURVE OTPC PALATANA GTG CAPABILITY CURVE OTPC PALATANA STG CAPABILITY CURVE

82 83 84 85 86

List of Tables Table 1 Table 2 Table 3 Table 4 Table 5 Table 6

Reactive power compensation sources Fault level at important sub-stations of NER Line Parameters and Surge Impedance Loading of Different Conductor Type Equipment preference List of units in NER to be normally operated with free governor action and AVR in service IEGC Operating Voltage Range

Page 4 of 100

16 19 24 37 62 93


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 400 kV Pallatana – Silchar D/C, 400/220 kV 315 MVA ICT at Misa, 400/132 kV 2x200 MVA ICT at Silchar, 400/132 kV 125 MVA ICT at Palatana, 132 kV Silchar – Badapur D/C, 132 kV Silchar – Srikona D/C, 132 kV Palatana – Udaipur D/C, 132 kV Palatana – Surajmani nagar D/C; Bus reactors at 400 kV Balipara(80 MVAR), 400 kV Silchar(2x63 MVAR), 400 kV Palatana(80 MVAR); Line reactors at 400 kV Silchar end(2x50 MVAR), 400 kV Pallatana end(2x63 MVAR) and Myntdu-Leshka (2x42 MW) MeECL Hydro plant has led to reinforcement in the 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.

Page 5 of 100


1 1.1

Reactive Power Management and Voltage Control Introduction

1.1.1

W

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.

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).

Page 6 of 100

Fig 1. Voltage and Current waveforms


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.

Page 7 of 100

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 voltamperes 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.

Fig 3. Boat pulled by a Horse

Fig 4. Direction of pull

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 5. Vector representation of the analogy

Page 8 of 100

W


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 updown 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. Fig 6. LABYRINTSPEL

1.2.4

The Objective is to twist the two knobs to adjust the angle of the platform in two directions, in order to keep the ball rolling through the maze without falling into any holes. Those twists are REACTIVE POWER, which helps propel the real power through to its ultimate goal, which is delivery to the user. Without reactive power, ball falls into holes along the way, which are NETWORK failures.

1.2.5

Both of these examples illustrate how important it is to understand the system and how it works in order to meet our objectives effectively. In the LABYRINTSPEL game, if the structure of the system is not taken into account, winning would be really easy because one knob would be turned Page 9 of 100


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 representation

Page 10 of 100


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 Page 11 of 100


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 Page 12 of 100


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

Fig 8. Time frames for voltage stability phenomena

1.5.5

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

1.6

Proximity to Instability

1.6.1

Static voltage instability is mainly associated with reactive power imbalance. Thus, the loadability of a bus in a system depends on the reactive power support that the bus can receive from the system. As the system approaches the maximum loading point or voltage collapse point, both real and reactive power losses increase rapidly. Page 13 of 100


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.

Knee point

∆v

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

1.6.4

Before reaching the critical point, a large voltage drop due to heavy reactive power losses is observed. The only way to save the system from voltage collapse is to reduce the reactive power load or add additional reactive power prior to reaching the point of voltage collapse. • • • •

These are curves drawn between V and P of a critical bus at a constant load power factor. These are produced by using a series of power flow solutions for different load levels. At the knee point or the nose point of the V-P curve, the voltage drops rapidly with an increase in the load demand. Power flow solution fails to converge beyond this limit which indicates the instability.

1.7

Reactive Reserve Margin

1.7.1

The amount of unused available capability of reactive power static as well as dynamic in the system (at peak load for a utility system) as a percentage of total capability is known as Reactive reserve margin.

1.7.2

Voltage collapse normally occurs when sources producing reactive power reach their limits i.e. generators, SVCs or shunt reactors, and there is not much reactive power to support the load. As reactive power is Page 14 of 100


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.

1.7.6

•

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.

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. Page 15 of 100


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 Static:

Sinks of Reactive Power

Shunt Capacitors Filter banks Under ground cables Transmission lines (lightly loaded) Fuel cells PV systems

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

• •

Transmission lines (Heavily loaded) Transformers Shunt Reactors Synchronous machines FACTS (e.g.,SVC,STATCOM) Induction generators (wind plants) Loads Induction motors (Pumps, Fans etc) Inductive loads (Arc furnace etc)

Table 1. Reactive power compensation sources

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.

Fig 10. Average cost of Reactive power technologies

Page 16 of 100


1.8

NER GRID – Overview

1.8.1

NER grid with a maximum peak requirement of around 1800 MW and installed capacity of 2189 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 6964 Ckt Kms of 132 KV lines, 1595 Ckt Kms of 400 KV lines and 2704 Ckt Kms of 220 KV lines compared to other regional grids.

Fig 11. NER Grid map

1.8.2

Almost 50% of the total NER load is spread out in 132 kV pocket of southern part of NER which were without the direct support of major EHV trunk lines. This part of the network is highly sensitive and is susceptible to grid disturbance and demands more operational acumen. Increase in the loading of major 132 kV trunk lines, in particular 132 kV DIMAPUR – IMPHAL S/C,132 kV JIRIBAM – LOKTAK S/C and 132 kV BADARPUR – KHLIEHRIAT S/C in peak hours has led to many a grid incidents in the past in the form of cascade tripping accompanied by voltage sag. Page 17 of 100


1.8.3

NER system has been strengthened With the commissioning of 400 kV Pallatana – Silchar D/C, 400/220 kV 315 MVA ICT at Misa, 400/132 kV 2x200 MVA ICT at Silchar, 400/132 kV 125 MVA ICT at Palatana, 132 kV Silchar – Badapur D/C, 132 kV Silchar – Srikona D/C, 132 kV Palatana – Udaipur D/C, 132 kV Palatana – Surajmani nagar D/C; Bus reactors at 400 kV Balipara(80 MVAR), 400 kV Silchar(2x63 MVAR), 400 kV Palatana(80 MVAR); Line reactors at 400 kV Silchar end(2x50 MVAR), 400 kV Pallatana end(2x63 MVAR) and Myntdu-Leshka (2x42 MW) MeECL Hydro plant. With the availability of greater options, 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 1758 MVAr from shunt reactors and 273 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 to technical glitches.

1.8.8

Reactive power management and voltage control are two aspects of a single activity that both supports reliability and facilitates commercial transaction across transmission network. Controlling reactive power flow can reduce losses and congestion on the transmission system. Page 18 of 100

REACTIVE POWER MANAGEMENT AND VOLTAGE CONTROL IN NORTH EASTERN REGION 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. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Bus Name Balipara 400 kV Ranganadi 400 kV Bongaigaon 400 kV Misa 220 kV Misa 400 kV Samaguri 220 kV Kopili 220 kV Sarusajai 220 kV Salakati 220 kV Mariani 220 kV Dimapur 220 kV Kahelipara 132 kV Agartala 132 kV R C Nagar 132 kV Kumarghat 132 kV

Fault MVA 3876 3650 3605 3469 3256 3221 2746 2557 2546 1641 1613 1578 863 861 647

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

•

• • •

The generating units provide the basic means of voltage control: The automatic voltage regulators (AVR) control field excitation to maintain the scheduled voltage levels at the terminals of the generators. In real time operation, connected generation should never be on reactive generation or absorption limits. By generation re-dispatch/rescheduling. Regulating voltage with the help of OLTC’s. By load staggering/shedding. Page 19 of 100


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 20 of 100


2 2.1

TRANSMISSION LINES AND REACTIVE POWER COMPENSATION 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 21 of 100


2.1.6

2.2

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.

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 22 of 100


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 : • • • • • •

2.4 2.4.1

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.

Line loading as function of Line Length and Compensation 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)

Fig 12. SIL VS Compensation

Further to take into account the line length one needs to multiple the modified SIL with the multiplying factor derived from St. Clair's curve.The derived steady state limit for a line would be = SIL modified x factor from St. Clair's curve. Page 23 of 100


Page 24 of 100


LIST-1: 400 KV LINE DETAILS OF NORTH EASTERN REGION SR. NO.

FROM

TO

UTILITY

KM

CKT

CONDUCTOR

1 2 3 4

BONGAIGAON BONGAIGAON BALIPARA BALIPARA

BALIPARA BALIPARA RANAGANADI RANAGANADI

POWERGRID POWERGRID POWERGRID POWERGRID

289.8 289.8 166.3 166.3

1 2 1 2

5

BALIPARA

MISA

POWERGRID

95.4

1

6

BALIPARA

MISA

POWERGRID

95.4

2

7 8 9 10

BONGAIGAON BONGAIGAON PALLATANA PALLATANA

BINAGURI(ER) BINAGURI(ER) SILCHAR SILCHAR

POWERGRID POWERGRID NETCL NETCL

218.0 218.0 246 246

1 2 1 2

ACSR MOOSE ACSR MOOSE ACSR MOOSE ACSR MOOSE ACSR MOOSE/AACSR ACSR MOOSE/AACSR TWIN MOOSE TWIN MOOSE ACSR MOOSE ACSR MOOSE

LIST-2: 400 KV LINE (CHARGED AT 220 KV) DETAILS OF NORTH EASTERN REGION SR. NO.

FROM

TO

UTILITY

KM

CKT

CONDUCTOR

1 2 3

MISA MARIANI MISA

KATHALGURI KATHALGURI

POWERGRID POWERGRID POWERGRID

382.8 162.9 220.0

1 1 1

ACSR MOOSE TWIN MOOSE TWIN MOOSE

MARIANI


FROM

TO

UTILITY

KM

CKT

CONDUCTOR

1 2 3 4 5 6 7 8 9

AGIA AGIA BOKO BOKO SARUSAJAI SARUSAJAI SARUSAJAI SARUSAJAI SAMAGURI

BTPS SARUSAJAI SARUSAJAI AGIA LANGPI LANGPI SAMAGURI SAMAGURI MARIANI

67.0 131.0 65.0 70.0 108.0 108.0 124.0 124.0 164.0

1 1 1 1 1 2 1 2 1

SINGLE ZEBRA SINGLE ZEBRA SINGLE ZEBRA SINGLE ZEBRA SINGLE ZEBRA SINGLE ZEBRA SINGLE ZEBRA SINGLE ZEBRA SINGLE ZEBRA

10

DEOMALI

KATHALGURI

19.0

1

SINGLE ZEBRA

11

BONGAIGAON

10.0

1

SINGLE ZEBRA

12

SALAKATI

POWERGRID

160.0

1

SINGLE ZEBRA

13

SALAKATI

POWERGRID

160.0

2

SINGLE ZEBRA

14 15

BALIPARA SALAKATI

SALAKATI BIRPARA (ER) BIRPARA (ER) SAMAGURI BTPS

AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL ARUNACHAL PRADESH POWERGRID

AEGCL AEGCL

55.0 2.7

1 1

SINGLE ZEBRA ACSR ZEBRA

Page 25 of 100

REACTIVE POWER MANAGEMENT AND VOLTAGE CONTROL IN NORTH EASTERN REGION 16 17 18 19 20 21 22 23 24 25 26 27 28 29

SALAKATI SAMAGURI SAMAGURI MISA MISA MISA MISA MISA MISA MISA KATHALGURI KATHALGURI NTPS NTPS

BTPS MISA MISA DIMAPUR DIMAPUR KOPILI KOPILI KOPILI BYRNIHAT BYRNIHAT TINSUKIA TINSUKIA TINSUKIA TINSUKIA

POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID MeECL MeECL AEGCL AEGCL AEGCL AEGCL

2.7 34.4 34.4 121.9 121.9 72.8 72.8 75.9 115.0 115.0 22.0 22.0 40.0 40.0

2 1 2 1 2 1 2 3 1 2 1 2 1 2

ACSR ZEBRA ACSR ZEBRA ACSR ZEBRA ACSR ZEBRA ACSR ZEBRA ACSR ZEBRA ACSR ZEBRA AAAC ZEBRA SINGLE ZEBRA SINGLE ZEBRA SINGLE ZEBRA SINGLE ZEBRA SINGLE ZEBRA SINGLE ZEBRA

LIST-4: 132 KV LINE DETAILS OF POWERGRID IN NORTH EASTERN REGION SR. NO.

FROM

1

SALAKATI

2 3 4

6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

NIRJULI NIRJULI RANGANADI KHLEIHRIAT MeECL KHLEIHRIAT KHLEIHRIAT KHANDONG HAFLONG KHLEIHRIAT BADARPUR JIRIBAM AIZWAL KOLASIB BADARPUR KUMARGHAT PANCHGRAM KUMARGHAT BADARPUR AIZWAL JIRIBAM LOKTAK

23

IMPHAL

24 25 26

IMPHAL DIMAPUR DIMAPUR

5

TO

UTILITY

KM

CKT

CONDUCTOR

POWERGRID

49.2

1

ACSR PANTHER


22.3 42.5 44.5

1 1 1

ACSR PANTHER ACSR PANTHER AAAC

KHLEIHRIAT

POWERGRID

5.5

1

ACSR PANTHER

KHANDONG KHANDONG HAFLONG JIRIBAM BADARPUR JIRIBAM AIZWAL KOLASIB BADARPUR KUMARGHAT AIZWAL BADARPUR R C NAGAR PANCHGRAM ZEMABAWK LOKTAK IMPHAL IMPHAL (MANIPUR) DIMAPUR DOYANG DOYANG

POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID

42.5 40.9 64.0 100.0 76.6 67.2 170.0 66.1 172.3 118.5 131.0 1.0 104.0 1.0 7.0 82.4 35.0

1 2 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1

ACSR PANTHER AAAC ACSR PANTHER ACSR PANTHER AAAC AAAC ACSR PANTHER AAAC AAAC AAAC ACSR PANTHER AAAC AAAC AAAC ACSR PANTHER ACSR PANTHER PANTHER

POWERGRID

1.5

1

PANTHER


168.9 92.5 92.5

1 1 2

ACSR PANTHER ACSR PANTHER ACSR PANTHER

GELYPHU (BHUTAN) RANGANADI GOHPUR ZIRO

Page 26 of 100

REACTIVE POWER MANAGEMENT AND VOLTAGE CONTROL IN NORTH EASTERN REGION 27

R C NAGAR

AGARTALA

POWERGRID

8.4

1

ACSR PANTHER

28

R C NAGAR

AGARTALA

POWERGRID

8.4

2

ACSR PANTHER

29

KHANDONG

KOPILI

POWERGRID

10.9

1

ACSR PANTHER

30

KHANDONG

KOPILI

POWERGRID

10.9

2

ACSR PANTHER

31

SILCHAR

BADARPUR

POWERGRID

19

1

AAAC

32

SILCHAR

BADARPUR

POWERGRID

19

2

AAAC

33

SILCHAR

SRIKONA

POWERGRID

1

1

AAAC

34

SILCHAR

SRIKONA

POWERGRID

1

2

AAAC

35

PALLATANA

SURAJMANI NGR

POWERGRID

37

1

AAAC

36

PALLATANA

SURAJMANI NGR

POWERGRID

37

2

AAAC

37

PALLATANA

UDAIPUR

POWERGRID

6

1

AAAC

38

PALLATANA

UDAIPUR

POWERGRID

6

2

AAAC

LIST-5: 132 KV LINE DETAILS OF NEEPCO IN NORTH EASTERN REGION SR. NO.

FROM

TO

UTILITY

KM

CKT

CONDUCTOR

1 2

BALIPARA KHUPI

KHUPI KIMI

NEEPCO NEEPCO

67.2 8.0

1 1

PANTHER PANTHER

LIST-6: 132 KV LINE DETAILS OF AEGCL IN NORTH EASTERN REGION SR. NO.

FROM

TO

UTILITY

KM

CKT

CONDUCTOR

1 2 3 4 5 6 7

GOSAIGAON GOSAIGAON DHALIGAON DHALIGAON DHALIGAON NALBARI DHALIGAON

AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL

65.0 62.0 22.0 22.0 106.0 22.0 41.0

1 1 1 2 1 1 1

PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER

8

DHALIGAON

AEGCL

37.0

1

PANTHER

9 10 11 12 13 14 15 16 17 18 19 20 21

BORNAGAR RANGIA RANGIA SIPAJHAR SISUGRAM RANGIA KAHELIPARA KAHELIPARA KAHELIPARA KAHELIPARA KAHELIPARA KAHELIPARA NARENGI

DHALIGAON GAURIPUR BTPS BTPS NALBARI RANGIA BORNAGAR ASHOK PAPER MILL RANGIA SISUGRAM SIPAJHAR ROWTA KAHELIPARA KAHELIPARA NARENGI SARUSAJAI SARUSAJAI SARUSAJAI SARUSAJAI DISPUR CTPS

AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL

86.0 33.0 38.0 44.0 12.0 46.0 12.0 4.0 4.0 4.0 4.0 3.0 20.0

1 1 1 1 1 1 1 1 2 3 4 1 1

PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER

Page 27 of 100

REACTIVE POWER MANAGEMENT AND VOLTAGE CONTROL IN NORTH EASTERN REGION 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62

DISPUR CTPS RANGIA ROWTA ROWTA DEPOTA DEPOTA SAMAGURI DIPHU B CHARIALI GOHPUR GOHPUR N LAKHIMPUR TINSUKIA TINSUKIA DHALIGAON DIBRUGARH MORAN LTPS LTPS TINSUKIA LTPS LTPS LTPS NAZIRA SRIKONA MARIANI MARIANI JORHAT MOKOKCHUNG MARIANI GOLAGHAT BOKAJAN BALIPARA PANCHGRAM PANCHGRAM SILCHAR JIRIBAM BALIPARA HAFLONG JAGIROAD

CTPS JAGIROAD ROWTA DEPOTA DEPOTA B CHARIALI SAMAGURI SANKARDEV NGR SANKARDEV NGR GOHPUR N LAKHIMPUR N LAKHIMPUR DHEMAJI LEDO DIBRUGARH BRPL MORAN LTPS NTPS NTPS NTPS NAZIRA NAZIRA MARIANI SIBSAGAR PAILAPOOL JORHAT JORHAT BOKAKHAT MARIANI GOLAGHAT BOKAJAN DIMAPUR DEPOTA SRIKONA SILCHAR DULLAVCHERRA PAILAPOOL GOHPUR HAFLONG HPC

AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL

29.0 35.0 108.0 72.0 64.0 57.0 45.0 61.0 72.0 51.0 77.0 77.0 63.0 53.0 53.0 1.0 36.0 39.0 60.0 60.0 43.0 22.0 22.0 80.0 13.0 35.0 20.0 20.0 89.0 19.0 45.0 65.0 5.0 28.0 19.0 30.0 50.0 15.0 106.0 1.0 5.0

1 1 1 1 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 1 2 1 1 1 1 2 1 1 1 1 1 1 1 1 1 1 1 1 1

PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER ACSR PANTHER PANTHER PANTHER PANTHER PANTHER SINGLE ZEBRA PANTHER PANTHER

LIST-7: 132 KV LINE DETAILS OF MANIPUR IN NORTH EASTERN REGION SR. NO.

FROM

TO

UTILITY

KM

CKT

CONDUCTOR

1 2 3

LOKTAK NINGTHOUKONG NINGTHOUKONG

NINGTHOUKONG CHURACHANDPUR CHURACHANDPUR

MANIPUR MANIPUR MANIPUR

20.0 23.0 23.0

1 1 2

PANTHER PANTHER PANTHER

Page 28 of 100

REACTIVE POWER MANAGEMENT AND VOLTAGE CONTROL IN NORTH EASTERN REGION 4 5 6 7 8 9 10 11

CHURACHANDPUR KAKCHING KONGBA YAINGANGPOKPI NINGTHOUKONG IMPHAL MANIPUR LOKTAK RENGPANG

KAKCHING KONGBA YAINGANGPOKPI IMPHAL MANIPUR IMPHAL MANIPUR KARONG RENGPANG JIRIBAM

MANIPUR MANIPUR MANIPUR MANIPUR MANIPUR MANIPUR MANIPUR MANIPUR

38.0 45.0 33.0 42.0 28.0 60.0 42.0 40.4

1 1 1 1 1 1 1 1

PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER

LIST-8: 132 KV LINE DETAILS OF TSECL IN NORTH SR. NO.

FROM

TO

UTILITY

KM

CKT

CONDUCTOR

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

P K BARI P K BARI P K BARI AGARTALA BARAMURA P K BARI KAMALPUR DHALABIL AGARTALA AGARTALA P K BARI BODHJ NGR JIRANIA GAMAITILLA ROKHIA

KAILASHOR KUMARGHAT AMBASA BODHJ NGR GAMAITILLA KAMALPUR DHALABIL AGARTALA ROKHIA ROKHIA DHARMA NAGAR JIRANIA BARAMURA AMBASA UDAIPUR

TSECL TSECL TSECL TSECL TSECL TSECL TSECL TSECL TSECL TSECL TSECL TSECL TSECL TSECL TSECL

18.0 1.0 45.0 8.0 14.0 31.0 32.0 45.0 35.0 35.0 35.0 7.0 15.0 25.0 40.0

1 1 1 1 1 1 1 1 1 2 1 1 1 1 1

PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER

LIST-9: 132 KV LINE DETAILS OF NAGALAND IN NORTH EASTERN REGION SR. NO.

FROM

TO

UTILITY

KM

CKT

CONDUCTOR

1 2 3 4 5 6 7 8

KOHIMA MELURI KOHIMA KOHIMA WOKHA DOYANG DIMAPUR DIMAPUR

MELURI KIPHIRI DIMAPUR (PGCIL) WOKHA DOYANG MOKOKCHUNG DIMAPUR (PGCIL) DIMAPUR (PGCIL)

NAGALAND NAGALAND NAGALAND NAGALAND NAGALAND NAGALAND NAGALAND NAGALAND

74 42 58 58 13 30 1 1

1 1 1 1 1 1 1 2

PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER

Page 29 of 100


LIST-10: 132 KV LINE DETAILS OF MIZORAM IN NORTH EASTERN REGION SR. NO.

FROM

TO

UTILITY

KM

CKT

CONDUCTOR

1 2 3

ZUANGTUI SERCHIP LUNGLEI

MIZORAM MIZORAM MIZORAM

50.0 54.0 69.0

1 1 1

PANTHER PANTHER PANTHER

4

AIZWAL

MIZORAM

6.7

1

ACSR PANTHER

5

BHAIRABI

SAITUAL ZUANGTUI SERCHIP LUANGMU AL KOLASIB

MIZORAM

30.0

1

PANTHER

LIST-11: 132 KV LINE DETAILS OF MeECL IN NORTH EASTERN REGION SR. NO. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

FROM

TO

UTILITY

KM

CKT

CONDUCTOR

UMIUM ST IV UMIUM ST IV UMTRU UMTRU UMTRU UMTRU UMTRU UMTRU EPIP II EPIP II EPIP II EPIP II UMIUM ST III UMIUM ST III UMIUM ST I UMIUM ST I UMIUM ST I MAWLAI MAWLAI NONGSTOIN NANGALBIBRA UMIUM MAWLAI NEHU

MeECL MeECL MeECL MeECL MeECL MeECL MeECL MeECL MeECL MeECL MeECL MeECL MeECL MeECL MeECL MeECL MeECL MeECL MeECL MeECL MeECL MeECL MeECL MeECL

8.0 8.0 41.2 41.2 37.6 37.6 0.7 0.7 2.5 2.5 10.0 10.0 17.5 17.5 3.0 12.0 5.0 41.0 71.3 56.0 68.7 7.0 9.2 7.0

1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 1 1 1 1 1 1 1 1 1

PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER

25

NEHU

MeECL

52.6

1

PANTHER

26

NEIGHRIMS

MeECL

64.8

1

PANTHER

27

KHLEIHRIAT MeECL

UMIUM ST III UMIUM ST III UMIUM ST III UMIUM ST III UMIUM ST IV UMIUM ST IV EPIP II EPIP II EPIP I EPIP I KILLING KILLING UMIUM ST I UMIUM ST I UMIUM ST II MAWLAI UMIUM CHEERAPUNJI NONGSTOIN NANGALBIBRA TURA NEHU NEHU NEIGHRIMS KHLEIHRIAT MeECL KHLEIHRIAT MeECL LUMSHNONG

MeECL

24.0

1

PANTHER

Page 30 of 100

REACTIVE POWER MANAGEMENT AND VOLTAGE CONTROL IN NORTH EASTERN REGION KHLEIHRIAT MeECL

28

LESHKA

MeECL

26.0

1

PANTHER

29

KHLEIHRIAT MeECL

LESHKA

MeECL

26.0

2

PANTHER

30

KHLEIHRIAT MeECL

KHLEIHRIAT

5.0

2

31

UMIUM ST I

MAWNGAP

MeECL MeECL

33

1

ACSR PANTHER ACSR PANTHER

32

UMIUM ST I

MAWNGAP

MeECL

33

2

ACSR PANTHER

33

EPIP II

TRISHUL

MeECL

0.2

1

ACSR PANTHER

34

EPIP II

NALARI

MeECL

0.2

1

ACSR PANTHER

0.15

1

ACSR PANTHER

35

EPIP I

SHYAM CENTURY

MeECL

36

EPIP I

MAITHAN

MeECL

0.2

1

ACSR PANTHER

4.0

1

ACSR PANTHER

37

EPIP I

SAI PRAKASH

MeECL

38

EPIP I

GREYSTONE

MeECL

0.7

1

ACSR PANTHER

MeECL

0.16

1

ACSR PANTHER

MeECL

3.0

1

ACSR PANTHER

8.0

1

39

LUMSHNONG

CMCL

40

LUMSHNONG

41

LUMSHNONG

42

LUMSHNONG

MCL ADHUNIK CEMENT HILL CEMENT

MeECL

8.0

1

ACSR PANTHER

43

LUMSHNONG

JUD CEMENT

MeECL

2.0

1

ACSR PANTHER

44

LUMSHNONG

GVIL CEMENT

MeECL

2.0

1

ACSR PANTHER

MeECL

ACSR PANTHER

LIST-12: 132 KV LINE DETAILS OF AP IN NORTH EASTERN REGION SR. NO. 1 2

FROM

TO

UTILITY

KM

CKT

CONDUCTOR

ZIRO

DAPORIJO

AP

87.2

1

PANTHER

DAPORIJO

ALONG

AP

81.7

1

PANTHER


FROM

TO

UTILITY

KM

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

MARIANI MARIANI MARIANI MARIANI NAZIRA NAZIRA GOLAGHAT GOLAGHAT BOKAJAN TINSUKIA AGIA TINSUKIA TINSUKIA FCI FCI

GOLAGHAT GOLAGHAT NAZIRA NAZIRA NTPS NTPS BOKAJAN BOKAJAN DIPHU RUPAI LAKHIPUR NTPS NTPS NTPS NTPS

AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL

40.0 40.0 54.0 54.0 74.0 74.0 64.0 64.0 39.0 25.0 34.0 36.0 36.0 3.0 3.0

Page 31 of 100

CKT CONDUCTOR 1 2 1 2 1 2 1 2 1 1 1 1 2 1 2

WOLF WOLF WOLF WOLF WOLF WOLF WOLF WOLF WOLF WOLF WOLF WOLF WOLF WOLF WOLF

REACTIVE POWER MANAGEMENT AND VOLTAGE CONTROL IN NORTH EASTERN REGION 16 17

DULLAVCHERRA PATHARKANDI

PATHARKANDI ADAMTILLA

AEGCL AEGCL

.... ....

1 1

WOLF WOLF

18

DIMAPUR

POWER HOUSE

NAGALAND

4.0

1

WOLF

19 20 21 22

POWER HOUSE NITO FARM DIMAPUR DIMAPUR

NAGALAND NAGALAND NAGALAND NAGALAND

5.0 12.0 5.4 5.4

1 1 1 2

WOLF WOLF WOLF WOLF

23

SINGRIJAN

NAGALAND

21.4

1

WOLF

24 25 26 27 28 29 30 31 32 33

SINGRIJAN MOKOKCHUNG MOKOKCHUNG TULI NAGINIMORA TIZIT MOKOKCHUNG TUENSANG KHIPHIRE KHIPHIRE

NAGALAND NAGALAND NAGALAND NAGALAND NAGALAND NAGALAND NAGALAND NAGALAND NAGALAND NAGALAND

7.9 46.0 56.3 33.0 44.0 31.0 50.4 55.7 35.0 35.0

1 1 1 1 1 1 1 1 1 2

WOLF WOLF WOLF WOLF WOLF WOLF WOLF WOLF WOLF WOLF

34

ROKHIA

DAIRY FARM DAIRY FARM SINGRIJAN SINGRIJAN GANESH NAGAR CHUMUKIDIMA ZUNHEBOTO TULI NAGINIMORA TIZIT MON TUENSANG KHIPHIRE LIKHIMRO LIKHIMRO RABINDRA NAGAR

TSECL

23.0

1

WOLF

BELONIA

TSECL

38.0

1

WOLF

BAGAFA SATCHAND SABROOM UDAIPUR GOKULNAGAR UDAIPUR BADARGHAT ROKHIA AGARTALA GUMTI AMARPUR TELIAMURA VAIRENGTE

TSECL TSECL TSECL TSECL TSECL TSECL TSECL TSECL TSECL TSECL TSECL TSECL MIZORAM

15.0 36.0 15.0 29.0 31.0 45.0 12.0 24.0 8.0 30.0 35.0 8.0 35.0

1 1 1 1 1 1 1 1 1 1 1 1 1

WOLF WOLF WOLF WOLF WOLF WOLF WOLF WOLF WOLF WOLF WOLF WOLF WOLF

35 36 37 38 39 40 41 42 43 44 45 46 47 48

RABINDRA NAGAR BELONIA BAGAFA SATCHAND BAGAFA UDAIPUR GUMTI GOKULNAGAR BADARGHAT BADARGHAT AMARPUR TELIAMURA BARAMURA KOLASIB

LIST-14: SHUNT COMPENSATED LINES IN NORTH EASTERN REGION

SR. NO.

FROM

TO

UTILITY

KM

CKT

1 2 3 4

RANGANADI RANGANADI BONGAIGAON BONGAIGAON

BALIPARA BALIPARA BALIPARA BALIPARA

POWERGRID POWERGRID POWERGRID POWERGRID

166.3 166.3 289.9 289.9

1 2 1 2

Page 32 of 100

SENDING RECEIVING END LINE END LINE REACTOR REACTOR 50 50 50 50

50 50 63 63

REACTIVE POWER MANAGEMENT AND VOLTAGE CONTROL IN NORTH EASTERN REGION 5 6 7 8

MISA MISA PALLATANA PALLATANA

KATHALGURI MARIANI SILCHAR SILCHAR

POWERGRID POWERGRID NETCL NETCL

382.9 220 247 247

1 1 1 2

50 50 63 63

NIL NIL 50 50

LIST-15: SHUNT COMPENSATED INTER – REGIONAL LINES IN NORTH EASTERN REGION SR. NO.

FROM

1

BONGAIGAON

2

BONGAIGAON

TO BINAGURI (ER) BINAGURI (ER)

UTILITY

KM

CKT

SENDING END LINE REACTOR

RECEIVING END LINE REACTOR

POWERGRID

218

1

63

NIL

POWERGRID

218

2

63

NIL

Page 33 of 100


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

CONNECTING STATES

1

ARUNACHAL ASSAM

2

ASSAM MEGHALAYA

ASSAM NAGALAND 3 ASSAM TRIPURA 4 5 6 7 8

ASSAM MANIPUR ASSAM MIZORAM MIZORAM MANIPUR MIZORAM TRIPURA NAGALAND MANIPUR

OWNED BY

FROM

TO

KV

KM

CKTS

CONDUCTOR

POWERGRID ARUNACHAL PRADESH NEEPCO POWERGRID POWERGRID POWERGRID AEGCL & MeECL AEGCL & MeECL AEGCL & MeECL POWERGRID AEGCL & NAGALAND AEGCL AEGCL & NAGALAND

RANGANADI DEOMALI KHUPI NIRJULI BADARPUR KHANDONG PANCHGRAM SARASUJAI KAHILIPARA MISA MARIANI BOKAJAN BOKAJAN

BALIPARA KATHALGURI BALIPARA GOHPUR KHLIEHRIET KHLIEHRIET LUMSHNONG UMTRU UMTRU DIMAPUR MOKOKCHUNG DIMAPUR DIMAPUR

400 220 132 132 132 132 132 132 132 220 132 132 66

166.3 19.0 67.2 42.5 76.6 42.5 23.4 37.0 9.0 123.5 50.0 5.0 8.0

D/C S/C S/C S/C S/C D/C S/C D/C D/C D/C S/C S/C S/C

TWIN MOOSE ZEBRA PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER PANTHER ZEBRA PANTHER PANTHER WOLF

AEGCL & TRIPURA

DULLAVCHERRA

DHARMANAGAR

132

29.0

S/C

PANTHER

POWERGRID POWERGRID POWERGRID AEGCL

BADARPUR BADARPUR HAFLONG PAILAPOOL

KUMARAGHAT JIRIBAM JIRIBAM JIRIBAM

132 132 132 132

118.5 67.2 100.6 15.0

S/C S/C S/C S/C

PANTHER PANTHER PANTHER PANTHER

POWERGRID

BADARPUR

KOLASIB

132

107.2

S/C

PANTHER

POWERGRID

AIZWAL

JIRIBAM

132

172.3

S/C

PANTHER

POWERGRID

AIZWAL

KUMARAGHAT

132

131.0

S/C

PANTHER

POWERGRID MANIPUR & NAGALAND

DIMAPUR KOHIMA

IMPHAL KARONG

132 132

168.9 50.0

S/C S/C

PANTHER PANTHER

Page 34 of 100


LIST-17: FIXED, SWITCHABLE AND CONVERTIBLE LINE REACTORS IN NORTH EASTERN REGION. SR. NO. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

UTILITY

FROM

TO

POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID

RANGANADI RANGANADI RANGANADI RANGANADI BONGAIGAON BONGAIGAON BONGAIGAON BONGAIGAON BALIPARA MISA MISA BONGAIGAON BONGAIGAON PALLATANA PALLATANA PALLATANA PALLATANA

BALIPARA BALIPARA BALIPARA BALIPARA BALIPARA BALIPARA BALIPARA BALIPARA MISA KATHALGURI MARIANI BINAGURI(ER) BINAGURI(ER) SILCHAR SILCHAR SILCHAR SILCHAR

INSTALLED AT (STATION) RANGANADI RANGANADI BALIPARA BALIPARA BONGAIGAON BONGAIGAON BALIPARA BALIPARA MISA MISA MISA BONGAIGAON BONGAIGAON SILCHAR SILCHAR PALLATANA PALLATANA

KV

MVAR

KM

400 400 400 400 400 400 400 400 400 220 220 400 400 400 400 400 400

50 50 50 50 50 50 63 63 50 50 50 63 63 50 50 63 63

166.3 166.3 166.3 166.3 289.9 289.9 289.9 289.9 95.4 382.9 220.0 218.0 218.0 247 247 247 247

PROVISION TO USE AS B/R SWITCHABLE CONVERTIBLE .... …. .... …. TRUE …. TRUE …. .... .... .... .... .... .... .... .... .... …. .... .... .... …. .... .... .... .... TRUE …. TRUE …. …. …. …. ….

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

Page 35 of 100

FIXED TRUE TRUE .... .... TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE …. …. …. ….


LIST-18: BUS REACTORS IN NORTH EASTERN REGION SR. NO.

UTILITY

INSTALLED AT (STATION)

KV

RATING MVAR MAKE

1 2 3 4 5 7 8 9 10 11 12

POWERGRID POWERGRID POWERGRID POWERGRID POWERGRID OTPC ASSAM ASSAM POWERGRID POWERGRID TRIPURA

BALIPARA BALIPARA BONGAIGAON MISA SILCHAR PALATANA MARIANI SAMAGURI AIZWAL KUMARGHAT DHARMANAGAR

400 400 400 400 400 400 220 220 132 132 132

50 80 2 X 50 50 2 X 63 80 2 X 12.5 2 X 12.5 20 20 2X2

BHEL BHEL BHEL BHEL CGL BHEL .... .... .... .... ....

STATUS IN SERVICE IN SERVICE IN SERVICE IN SERVICE IN SERVICE IN SERVICE IN SERVICE IN SERVICE IN SERVICE IN SERVICE IN SERVICE

LIST-19: TERTIARY REACTORS ON 33 KV SIDE OF 400/220/33 KV ICTS IN NORTH EASTERN REGION SR. NO.

UTILITY

INSTALLED AT (STATION)

1

POWERGRID

BALIPARA

2

POWERGRID

BONGAIGAON

3

POWERGRID

MISA

INSTALLED ON 33 KV SIDE OF ICT I 33 KV SIDE OF ICT I 33 KV SIDE OF ICT I

Page 36 of 100

RATING MVAR MAKE

STATUS

4 X 25

BHEL

IN SERVICE

2 X 25

BHEL

IN SERVICE

4 X 25

BHEL

IN SERVICE


3 3.1

SERIES AND SHUNT CAPACITOR VOLTAGE CONTROL 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 37 of 100


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 38 of 100


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-20: SUBSTATIONS IN NER AGENCY POWER GRID ARUNACHAL PRADESH AEGCL MANIPUR MeECL MIZORAM NAGALAND

400KV 4

220 KV 2

132 KV & 66 KV 9

TOTAL 15

NIL

1

6

7

NIL NIL NIL NIL NIL

6 NIL NIL NIL NIL

22 6 9 4 5

28 6 9 4 5

TSECL

NIL

NIL

9

9

OTPC TOTAL

1 5

NIL 9

NIL 70

1 84

Page 39 of 100


LIST-21: SHUNT CAPACITOR DETAILS OF NORTH EASTERN REGION SR. NO.

UTILITY

SUBSTATION

INSTALLED ON

CAPACITY (MVAR)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

MeECL MeECL MeECL MeECL MeECL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL AEGCL

132 KV BUS BAR 132 KV BUS BAR 132 KV BUS BAR 33 KV BUS BAR 33 KV BUS BAR 33 KV BUS BAR 33 KV BUS BAR 33 KV BUS BAR 33 KV BUS BAR 33 KV BUS BAR 33 KV BUS BAR 33 KV BUS BAR 33 KV BUS BAR 33 KV BUS BAR 33 KV BUS BAR 33 KV BUS BAR 33 KV BUS BAR 33 KV BUS BAR 33 KV BUS BAR

12.5 20 20 15 15 2X5 3X5 2X5 1X5 1X10 2X10 2X5 1X5 1X5 2X5 2X10 2X5 2X5 2X10

20

AEGCL

33 KV BUS BAR

2X5

21 22

AEGCL AEGCL

MAWLAI EPIP I EPIP II EPIP II EPIP II BAGHJAB KAHELIPARA BARNAGAR GOSAIGAON GAURIPUR RANGIA MARGHERITA N LAKHIMPUR DULLAVCHERRA DEPOTA SARUSAJAI ROWTA DIPHU DIBRUGARH SHANKARDEV NAGAR RUPAI SRIKONA

33 KV BUS BAR 33 KV BUS BAR

2X5 2X5

Total Capacity of NER

Page 40 of 100

273


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 0.51.7%. 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. Fig 13. Switching principle of LTC

4.1.4

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

4.1.5

The pulse is generated by the AVR whenever the measured voltage, for a given time, deviates from the set reference value by more than the preset dead band (i.e. degree of insensitivity). Time delay is used to avoid Page 41 of 100


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 42 of 100


LIST-22: ICT DETAILS OF POWERGRID IN NORTH EASTERN REGION SL. NO.

SUBSTATION

AGENCY

ICT NO.

MVA

KV RATIO

MAKE

TT

NT

1

BALIPARA

POWERGRID

01

315

400/220 /33 kV

TELK

17

9

1.25

5

10

2

BONGAIGAON

POWERGRID

01

315

400/220 /33 kV

TELK

17

9

1.25

5

12

3

SILCHAR

POWERGRID

01

200

CGL

17

9

1.25

5

9B

4

SILCHAR

POWERGRID

01

200

CGL

17

9

1.25

5

9B

5

MISA

POWERGRID

01

315

TELK

17

9

1.25

5

05

6

MISA

POWERGRID

02

315

CGL

17

9

1.25

5

05

7

DIMAPUR

POWERGRID

01

100

TELK

17

13

1.25

2.75

12

8

DIMAPUR

POWERGRID

02

100

ALSTOM

17

13

1.25

2.75

12

9

NIRJULI

POWERGRID

01

10

132 /33 kV

KANOHAR ELECT.

17

9

1.25

1.65

09

10

NIRJULI

POWERGRID

01

10

132 /33 kV

BBL

5

3

1.25

1.65

03

11

SALAKATI

POWERGRID

01

50

NGEF

17

13

1.25

2.75

16

12

SALAKATI

POWERGRID

02

50

EMCO

17

13

1.25

2.75

16

13

ZIRO

POWERGRID

01

15

132 /33 kV

AREVA /ALSTOM

17

9

1.25

1.65

02

14

KOPILI

POWERGRID

01

160

220/132 KV

….

….

….

….

….

13

400/132 kV 400/132 kV 400/220 /33 kV 400/220 kV 220/132 kV 220/132 kV

220/132 kV 220/132 kV

STEP %AGE KV

LIST-23: ICT DETAILS OF NEEPCO IN NORTH EASTERN REGION SL. NO.

SUBSTATION

AGENCY

ICT NO.

MVA

1

RHEP

NEEPCO

01

7.5

2

RHEP

NEEPCO

02

7.5

3

BALIPARA

NEEPCO

01

50

4

KOPILI

NEEPCO

01

60

5

RHEP

NEEPCO

01

360

Page 43 of 100

KV RATIO 132/33 KV 132/33 KV 220/132 KV 220/132 KV 400/132 KV

STEP %AGE KV

MAKE

TT

NT

PT

….

….

….

….

….

02

….

….

….

….

….

03

….

….

….

….

….

09

….

….

….

….

….

09

….

….

….

….

….

10

PT


RHEP

NEEPCO

02

400/132 KV

360

….

….

….

….

….

09

STEP %AGE KV

PT

LIST-24: ICT DETAILS OF NHPC IN NORTH EASTERN REGION SL. NO.

SUBSTATION

AGENCY

ICT NO.

MVA

1

LOKTAK

NHPC

01

5

KV RATIO 132/33 KV

MAKE

TT

NT

….

….

….

….

….

02

STEP %AGE KV

PT

LIST-25: ICT DETAILS OF ARUNACHAL PRADESH IN NORTH EASTERN REGION SL. NO.

SUBSTATION

1

ALONG

2

DAPORIJO

3

DAPORIJO

4

DEOMALI

5

DEOMALI

6

LEKHI

7

LEKHI

AGENCY ARUNACHAL PRADESH ARUNACHAL PRADESH ARUNACHAL PRADESH ARUNACHAL PRADESH ARUNACHAL PRADESH ARUNACHAL PRADESH ARUNACHAL PRADESH

ICT NO.

MVA

01

15

01

5

02

5

01

100

01

16

01

15

01

20

KV RATIO 132/33 KV 132/33 KV 132/33 KV 220/ 132 kV 132/33 KV 132/33 KV 132/33 KV

MAKE

TT

NT

….

….

….

….

….

03

….

….

….

….

….

02

….

….

….

….

….

02

….

….

….

….

….

09

….

….

….

….

….

04

….

….

….

….

….

05

….

….

….

….

….

05

STEP %AGE KV

PT

LIST-26: ICT DETAILS OF AEGCL IN NORTH EASTERN REGION SL. NO.

SUBSTATION

AGENCY

ICT NO.

MVA

1

AGIA

AEGCL

01

50

2

AGIA

AEGCL

01

16

3

AGIA

AEGCL

01

12.5

AEGCL

01

12.5

AEGCL

01

16

4 5

ASHOK PAPER MILL ASHOK PAPER MILL

6

BAGHJHAP

AEGCL

01

16

7

BAGHJHAP

AEGCL

02

16

Page 44 of 100

KV RATIO 220/132 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV

MAKE

TT

NT

….

….

….

….

….

14

….

….

….

….

….

05

….

….

….

….

….

05

….

….

….

….

….

05

….

….

….

….

….

05

….

….

….

….

….

05

….

….

….

….

….

05


BALIPARA

AEGCL

01

50

9

BOKO

AEGCL

01

10

10

BOKO

AEGCL

02

10

11

B CHARIALI

AEGCL

01

16

12

B CHARIALI

AEGCL

02

16

13

BORNAGAR

AEGCL

01

25

14

BORNAGAR

AEGCL

02

25

15

BOKAKHAT

AEGCL

01

16

16

BOKAKHAT

AEGCL

02

16

17

BOKAJAN

AEGCL

01

16

18

BTPS

AEGCL

01

10

19

BTPS

AEGCL

02

10

20

BTPS

AEGCL

01

80

21

BTPS

AEGCL

02

80

22

BTPS

AEGCL

03

160

23

CTPS

AEGCL

01

16

24

CTPS

AEGCL

01

30

25

DEPOTA

AEGCL

01

31.5

26

DEPOTA

AEGCL

02

31.5

27

DHALIGAON

AEGCL

01

25

28

DHALIGAON

AEGCL

02

25

29

DHEMAJI

AEGCL

01

16

30

DIPHU

AEGCL

01

16

31

DIPHU

AEGCL

02

16

32

DIBRUGARH

AEGCL

01

31.5

33

DIBRUGARH

AEGCL

01

20

34

DIBRUGARH

AEGCL

02

20

Page 45 of 100

220 /132 kV 220/132 KV 220/132 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 220/132 kV 220/132 kV 220/132 kV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/66 KV 132/66 KV 132/33 KV 132/33 KV 132/33 KV

….

….

….

….

….

09

….

….

….

….

….

05

….

….

….

….

….

05

….

….

….

….

….

17

….

….

….

….

….

17

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

05

….

….

….

….

….

05

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

08

….

….

….

….

….

08

….

….

….

….

….

08


DISPUR

AEGCL

01

16

36

DISPUR

AEGCL

02

16

37

DULLAVCHERRA

AEGCL

01

3.5

38

DULLAVCHERRA

AEGCL

02

3.5

39

DULLAVCHERRA

AEGCL

03

3.5

40

DULLAVCHERRA

AEGCL

04

3.5

41

DULLAVCHERRA

AEGCL

05

3.5

42

DULLAVCHERRA

AEGCL

06

3.5

43

GAURIPUR

AEGCL

01

10

44

GAURIPUR

AEGCL

02

10

45

GOHPUR

AEGCL

01

16

46

GOHPUR

AEGCL

01

10

47

GOSSAIGAON

AEGCL

01

16

48

GOLAGHAT

AEGCL

01

25

49

GOLAGHAT

AEGCL

02

25

50

HAFLONG

AEGCL

01

10

51

HAFLONG

AEGCL

02

10

52

JORHAT

AEGCL

01

25

53

JORHAT

AEGCL

01

16

54

KAHELIPARA

AEGCL

01

30

55

KAHELIPARA

AEGCL

02

30

56

KAHELIPARA

AEGCL

03

30

57

KAHELIPARA

AEGCL

01

10

58

KAHELIPARA

AEGCL

02

10

59

LEDO

AEGCL

01

10

60

LEDO

AEGCL

02

10

61

LTPS

AEGCL

01

7.5

62

LTPS

AEGCL

02

7.5

Page 46 of 100

132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33/11 KV 132/33/11 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

05

….

….

….

….

….

03

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

05

….

….

….

….

….

05

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

05

….

….

….

….

….

05

….

….

….

….

….

06

….

….

….

….

….

02

….

….

….

….

….

02

….

….

….

….

….

06

….

….

….

….

….

06

….

….

….

….

….

….

….

….

….

….

….

….


MAJULI

AEGCL

01

5.5

64

MARIANI

AEGCL

01

20

65

MARIANI

AEGCL

02

20

66

MARIANI

AEGCL

01

100

67

MARIANI

AEGCL

02

100

68

MORAN

AEGCL

01

16

69

MORAN

AEGCL

02

16

70

NALBARI

AEGCL

01

16

71

NALBARI

AEGCL

02

16

AEGCL

01

10

AEGCL

02

10

72

73

NALKATA (NORTH LAKHIMPUR) NALKATA (NORTH LAKHIMPUR)

74

NARENGI

AEGCL

01

25

75

NARENGI

AEGCL

02

25

76

NAZIRA

AEGCL

01

25

77

NTPS

AEGCL

01

25

78

NTPS

AEGCL

02

25

79

PAILAPOOL

AEGCL

01

10

80

PAILAPOOL

AEGCL

02

10

81

PAILAPOOL

AEGCL

03

10

82

PANCHGRAM

AEGCL

01

16

83

PANCHGRAM

AEGCL

02

16

84

PANCHGRAM

AEGCL

01

10

85

PANCHGRAM

AEGCL

02

10

86

PAVOI

AEGCL

01

16

87

PAVOI

AEGCL

02

16

88

RANGIA

AEGCL

01

25

89

RANGIA

AEGCL

02

25

Page 47 of 100

132/33 KV 132/66 KV 132/66 KV 220/132 kV 220/132 kV 132/33 KV 132/33 KV 132/33 KV 132/33 KV

….

….

….

….

….

….

….

….

….

….

….

06

….

….

….

….

….

06

….

….

….

….

….

13

….

….

….

….

….

13

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

132/33 KV

….

….

….

….

….

….

132/33 KV

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

06

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

05

….

….

….

….

….

05

….

….

….

….

….

05

….

….

….

….

….

08

….

….

….

….

….

08

….

….

….

….

….

01

….

….

….

….

….

03

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

03

….

….

….

….

….

03

132/33 KV 132/33 KV 132/33 KV 132/66 KV 132/66 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV


ROWTA

AEGCL

01

25

91

ROWTA

AEGCL

02

25

92

S NAGAR

AEGCL

01

16

93

S NAGAR

AEGCL

02

16

94

SAMAGURI

AEGCL

01

50

95

SAMAGURI

AEGCL

02

50

96

SAMAGURI

AEGCL

03

50

97

SAMAGURI

AEGCL

01

25

98

SAMAGURI

AEGCL

02

25

99

SARUSAJAI

AEGCL

01

31.5

100

SARUSAJAI

AEGCL

02

31.5

101

SARUSAJAI

AEGCL

01

100

102

SARUSAJAI

AEGCL

02

100

103

SARUSAJAI

AEGCL

03

100

104

SISUGRAM

AEGCL

01

31.5

105

SISUGRAM

AEGCL

02

31.5

106

SIBSAGAR

AEGCL

01

16

107

SIBSAGAR

AEGCL

02

16

108

SIPAJHAR

AEGCL

01

16

109

SIPAJHAR

AEGCL

02

16

110

SRIKONA

AEGCL

01

25

111

SRIKONA

AEGCL

02

25

112

TINSUKIA

AEGCL

01

20

113

TINSUKIA

AEGCL

02

20

114

TINSUKIA

AEGCL

03

20

115

TINSUKIA

AEGCL

01

50

116

TINSUKIA

AEGCL

02

50

Page 48 of 100

132/33 KV 132/33 KV 132/33 KV 132/33 KV 220/132 kV 220/132 kV 220/132 kV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 220/132 KV 220/132 kV 220/132 kV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/66 KV 132/66 KV 132/66 KV 220/132 kV 220/132 kV

….

….

….

….

….

03

….

….

….

….

….

03

….

….

….

….

….

04

….

….

….

….

….

05

….

….

….

….

….

12

….

….

….

….

….

12

….

….

….

….

….

12

….

….

….

….

….

06

….

….

….

….

….

06

….

….

….

….

….

06

….

….

….

….

….

06

….

….

….

….

….

10

….

….

….

….

….

12

….

….

….

….

….

11

….

….

….

….

….

06

….

….

….

….

….

06

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

05

….

….

….

….

….

05

….

….

….

….

….

02

….

….

….

….

….

04

….

….

….

….

….

03

….

….

….

….

….

16

….

….

….

….

….

16


LIST-27: ICT DETAILS OF MANIPUR IN NORTH EASTERN REGION SL. NO.

SUBSTATION

AGENCY

ICT NO.

MVA

1

CHURACHANDPUR

MANIPUR

01

20

2

IMPHAL

MANIPUR

01

20

3

IMPHAL

MANIPUR

02

20

4

IMPHAL

MANIPUR

03

20

5

KAKCHING

MANIPUR

01

20

6

KARONG

MANIPUR

01

20

7

NINGTHOUKHONG

MANIPUR

01

12.5

8

NINGTHOUKHONG

MANIPUR

02

12.5

9

YANGANGPOKPI

MANIPUR

01

20

10

YANGANGPOKPI

MANIPUR

02

20

11

JIRIBAM

MANIPUR

01

6.3

KV RATIO 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV

STEP %AGE KV

MAKE

TT

NT

PT

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

….

LIST-28: ICT DETAILS OF MEGHALAYA IN NORTH EASTERN REGION SL. NO.

SUBSTATION

AGENCY

ICT NO.

MVA

1

CHERAPUNJEE

MeECL

01

12.5

2

EPIP I

MeECL

01

20

3

EPIP I

MeECL

02

20

4

EPIP II

MeECL

01

50

5

KHLIEHRIAT

MeECL

01

20

6

KHLIEHRIAT

MeECL

02

20

7

MAWLAI

MeECL

01

20

8

MAWLAI

MeECL

02

20

9

MAWLAI

MeECL

01

10

10

MAWLAI

MeECL

01

12.5

11

NANGALBIBRA

MeECL

01

10

Page 49 of 100


STEP %AGE KV

MAKE

TT

NT

PT

….

….

….

….

….

06

….

….

….

….

….

03

….

….

….

….

….

03

….

….

….

….

….

08

….

….

….

….

….

05

….

….

….

….

….

06

….

….

….

….

….

04

….

….

….

….

….

08

….

….

….

….

….

03

….

….

….

….

….

07

….

….

….

….

….

07


NANGALBIBRA

MeECL

01

12.5

13

NEHU

MeECL

01

20

14

NEHU

MeECL

02

20

15

NEIGRIHMS

MeECL

01

10

16

NEIGRIHMS

MeECL

02

10

17

NONGSTOIN

MeECL

01

12.5

18

UMIUM ST III

MeECL

01

10

19

TURA

MeECL

01

20

20

TURA

MeECL

01

15

21

TURA

MeECL

02

15

22

TURA

MeECL

03

15

23

LUMSHNONG

MeECL

01

10

24

UMTRU

MeECL

01

20

132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV

….

….

….

….

….

06

….

….

….

….

….

06

….

….

….

….

….

06

….

….

….

….

….

05

….

….

….

….

….

04

….

….

….

….

….

04

….

….

….

….

….

08

….

….

….

….

….

15

….

….

….

….

….

15

….

….

….

….

….

15

….

….

….

….

….

15

….

….

….

….

….

….

….

….

….

….

….

02

LIST-29: ICT DETAILS OF MIZORAM IN NORTH EASTERN REGION SL. NO. 1 2 3 4

SUBSTATION AIZAWL LUANGMUAL AIZAWL LUANGMUAL AIZAWL ZUANGTUI AIZAWL ZUANGTUI

AGENCY

ICT NO.

MVA

MIZORAM

01

12.5

MIZORAM

02

12.5

MIZORAM

01

12.5

MIZORAM

02

12.5

5

KOLASIB

MIZORAM

01

12.5

6

KOLASIB

MIZORAM

02

12.5

7

LUNGLEI

MIZORAM

01

12.5

8

LUNGLEI

MIZORAM

02

12.5

9

SERCHHIP

MIZORAM

01

12.5

10

SERCHHIP

MIZORAM

02

6.3

11

SAITUAL

MIZORAM

01

6.3

Page 50 of 100


STEP %AGE KV

MAKE

TT

NT

PT

….

….

….

….

….

05

….

….

….

….

….

05

….

….

….

….

….

05

….

….

….

….

….

05

….

….

….

….

….

10

….

….

….

….

….

09

….

….

….

….

….

05

….

….

….

….

….

09

….

….

….

….

….

02

….

….

….

….

….

03

….

….

….

….

….

06


LIST-30: ICT DETAILS OF NAGALAND IN NORTH EASTERN REGION SL. NO.

SUBSTATION

AGENCY

ICT NO.

MVA

1

DIMAPUR

NAGALAND

01

20

2

DIMAPUR

NAGALAND

02

20

3

DIMAPUR

NAGALAND

03

20

4

KIPHIRE

NAGALAND

01

6.5

5

KIPHIRE

NAGALAND

02

6.5

6

KIPHIRE

NAGALAND

03

6.5

7

KOHIMA

NAGALAND

01

8

8

KOHIMA

NAGALAND

02

8

9

KOHIMA

NAGALAND

03

8

10

MELURI

NAGALAND

01

5

11

MOKOKCHUNG

NAGALAND

01

12.5

12

MOKOKCHUNG

NAGALAND

02

12.5

13

WOKHA

NAGALAND

01

5

KV RATIO 132/66 KV 132/66 KV 132/66 KV 132/66 KV 132/66 KV 132/66 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/66 KV 132/66 KV 132/33 KV

STEP %AGE KV

MAKE

TT

NT

PT

….

….

….

….

….

05

….

….

….

….

….

05

….

….

….

….

….

03

….

….

….

….

….

04

….

….

….

….

….

04

….

….

….

….

….

04

….

….

….

….

….

03

….

….

….

….

….

03

….

….

….

….

….

03

….

….

….

….

….

01

….

….

….

….

….

04

….

….

….

….

….

04

….

….

….

….

….

03

LIST-31: ICT DETAILS OF TSECL IN NORTH EASTERN REGION SL. NO.

SUBSTATION

AGENCY

ICT NO.

MVA

1

AGARTALA

TSECL

01

15

2

AGARTALA

TSECL

01

15

3

AGARTALA

TSECL

02

15

4

AGARTALA

TSECL

03

15

5

AGARTALA

TSECL

04

15

6

AGARTALA

TSECL

01

20

7

AGARTALA

TSECL

02

20

8

AGARTALA

TSECL

01

15

9

AMBASA

TSECL

01

7.5

Page 51 of 100

KV RATIO 132/66 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/11 KV 132/33 KV

STEP %AGE KV

MAKE

TT

NT

PT

….

….

….

….

….

09

….

….

….

….

….

13

….

….

….

….

….

13

….

….

….

….

….

13

….

….

….

….

….

13

….

….

….

….

….

13

….

….

….

….

….

13

….

….

….

….

….

13

….

….

….

….

….

08


AMBASA

TSECL

02

7.5

11

BARAMURA

TSECL

01

30

12

DHALABIL

TSECL

01

7.5

13

DHARMANAGAR

TSECL

01

7.5

14

DHARMANAGAR

TSECL

02

7.5

15

DHARMANAGAR

TSECL

03

7.5

16

KAILASHOR

TSECL

01

7.5

17

KAMALPUR

TSECL

01

7.5

18

P K BARI

TSECL

01

15

19

P K BARI

TSECL

01

10

20

ROKHIA

TSECL

01

30

21

UDAIPUR

TSECL

01

10

22

UDAIPUR

TSECL

01

15

132/33 KV 132/66 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/33 KV 132/11 KV 132/33 KV 132/11 KV 132/66 KV 132/66 KV 132/11 KV

….

….

….

….

….

08

….

….

….

….

….

05

….

….

….

….

….

04

….

….

….

….

….

07

….

….

….

….

….

07

….

….

….

….

….

07

….

….

….

….

….

08

….

….

….

….

….

08

….

….

….

….

….

05

….

….

….

….

….

05

….

….

….

….

….

05

….

….

….

….

….

05

….

….

….

….

….

05

LIST-32: ICT DETAILS OF OTPC IN NORTH EASTERN REGION SL. NO.

SUBSTATION

AGENCY

ICT NO.

MVA

1

PALLATANA

OTPC

01

125

LIST-33:

KV RATIO 400/132 kV

MAKE

TT

NT

BHEL

….

….

TRANSMISSION/TRANSFOMATION/VAR CAPACITY OF NER

STEP %AGE KV ….

….

COMPENSATION

TRANSMISSION LINE (CKT KM) AGENCY

400 KV

220 KV

132 KV

POWERGRID STATES TOTAL

1595 0 1595

1312 1392 2704

1964 5000 6964

TRANSFORMATION CAPACITY (MVA) POWERGRID/NEEPCO/OTPC/NHPC STATES

2155/845/125/5 MVA 4265 MVA

REACTIVE COMPENSATION (MVAR) POWERGRID/NEEPCO/OTPC STATES

1398/100/206 MVAR 54 MVAR

CAPACITIVE COMPENSATION – 273 MVAR Page 52 of 100

PT ….


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.

Page 53 of 100

REACTIVE POWER MANAGEMENT AND VOLTAGE CONTROL IN NORTH EASTERN REGION 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.

Page 54 of 100


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.

Basic Components of HVDC Terminal Converter Xmers

DC Line

Smoothing Reactor

400 kV

AC PLC DC Filter

DC Filter

DC Filter

DC Filter

AC Filter

AC Filter

Valve Halls

Electrode station

-Thyristors

-Control & Protection

-Firing ckts

-Telecommunication

-Cooling ckt

Control Room

Fig 14. HVDC Fundamental components

5.2.7

Harmonics are normally minimized by using filters. The following types of filters are used: • • •

AC filters. DC filters. High frequency filters. Page 55 of 100

REACTIVE POWER MANAGEMENT AND VOLTAGE CONTROL IN NORTH EASTERN REGION 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 2013-14. 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.

Page 56 of 100


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 electronicsbased 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 turnoff 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.

Page 57 of 100


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

6.3

Converter-based Compensator

6.3.1

Static Synchronous Compensator (STATCOM) is one of the key Converter-based Compensators which are usually based on the voltage source inverter (VSI) or current source inverter (CSI), as shown in Figure 16 (a). Unlike SVC, STATCOM controls the output current independently of the AC system voltage, while the DC side voltage is automatically maintained to serve as a voltage source. Mostly, STATCOM is designed based on the VSI (VOLTAGE SOURCE INVERTER). Fig 16. STATCOM topologies: (a) STATCOM based on VSI and CSI (b) STATCOM with storage

Page 58 of 100


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, seriescontrollers can also be divided into converter type.

6.4.2

The former includes Thyristor-Switched Series Capacitor (TSSC), Thyristor-Controlled Series Capacitor (TCSC), ThyristorSwitched 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.

connected either impedance

FACTS type or

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

Page 59 of 100


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

Fig 18. D-Curve of a typical Generator

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 coreend heating limit. The synchronizing torque is also reduced when absorbing large amounts of reactive power, which can also limit Page 60 of 100


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 primemover 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.

Page 61 of 100


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 50MVAR 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.

Page 62 of 100


1.

LTPS UNIT 5, 6 & 7 CAPABILITY CURVE

Page 63 of 100


2.

NTPS UNIT 1, 2 & 3 CAPABILITY CURVE Page 64 of 100


3.

NTPS UNIT 4 CAPABILITY CURVE Page 65 of 100


4.

NTPS UNIT 6 CAPABILITY CURVE

Page 66 of 100


5.

LTPS CAPABILITY CURVE

Page 67 of 100


6.

NTPS CAPABILITY CURVE

Page 68 of 100


7.

UMIUM ST I CAPABILITY CURVE

Page 69 of 100


8.

UMIUM STAGE II CAPABILITY CURVE Page 70 of 100


9.

UMIUM STAGE III CAPABILITY CURVE

Page 71 of 100


10.

UMIUM STAGE IV CAPABILITY CURVE Page 72 of 100


11.

AGBPP UNIT 5, 6, 7, 8 & 9 CAPABILITY CURVE Page 73 of 100


12.

AGBPP UNIT 1, 2, 3 & 4 CAPABILITY CURVE Page 74 of 100


13.

AGTPP CAPABILITY CURVE

Page 75 of 100


14.

DOYANG HEP UNIT 1 CAPABILITY CURVE Page 76 of 100


15.

KHANDONG HEP UNIT 2 CAPABILITY CURVE Page 77 of 100


16.

KOPILI HEP UNIT 1 CAPABILITY CURVE Page 78 of 100


17.

KOPILI HEP UNIT 2 CAPABILITY CURVE Page 79 of 100


18.

KOPILI HEP ST II CAPABILITY CURVE

Page 80 of 100


19.

RANGANADI HEP CAPABILITY CURVE Page 81 of 100


20.

LOKTAK HEP CAPABILITY CURVE Page 82 of 100


21.

ROKHIA UNIT 3, 4 & 6 CAPABILITY CURVE Page 83 of 100


22.

ROKHIA & BARAMURA CAPABILITY CURVE Page 84 of 100


23.

OTPC PALATANA GTG CAPABILITY CURVE Page 85 of 100


23.

OTPC PALATANA STG CAPABILITY CURVE Page 86 of 100


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 realpower 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.

Page 87 of 100


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.

Page 88 of 100


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 voltagecontrol 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.

Page 89 of 100


10 10.1

Statutory Provisions for Reactive Management and voltage Control

Power

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 Page 90 of 100


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 operationOutage 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)

10.2.2

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.

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 Page 91 of 100


points thereby avoiding the need for exchange of Reactive Power to/from ISTS and to maintain ISTS voltage within the specified range. b)

10.2.3

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.

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.

Page 92 of 100


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 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%

Page 93 of 100


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: Page 94 of 100

REACTIVE POWER MANAGEMENT AND VOLTAGE CONTROL IN NORTH EASTERN REGION 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 NorthEastern Regional Grid and NERLDC has the overall responsibility of the integrated operation of the NorthEastern 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 Page 95 of 100


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 Page 96 of 100


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:

Nominal

Maximum

Minimum

400

420

380

220

245

198

132

145

122

(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 Page 97 of 100


instruct SSGS to maintain specified voltage level at interconnecting points. SLDC and AEGCL Gridco shall coordinate with the Distribution Licensees to determine voltage level at the interconnection points. SLDC shall continuously monitor 400/220/132kV voltage levels at strategic substations 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.

Page 98 of 100


11.

Bibliography: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.

Best practice manual of transformer for BEE and IREDA by Devki energy consultancy pvt. ltd. NERPC progress report August, 2010. Document on MeSEB capacity building and training document Manual on Transmission Planning Criteria, CEA, Govt. of India, June 1994 Indian Electricity Grid Code, CERC, India, 2010 The Central Electricity Authority (Technical Standard for connectivity to the grid) Regulations 2007. Operation procedure for NER January 2010. Document on Metering code for AEGCL grid. Principles of efficient and reliable reactive power supply and consumption, staff report, FERC, Docket No. AD05-1-000, February 4, 2005 th th Proceedings of workshop on grid security & management 28 and 29 April, 2008 Bangalore. Extra High Voltage AC transmission Engineering – R D Begamudre. Electrical Engineering Handbook – SIEMENS. C. W. Taylor, “Power System Voltage Stability”, McGraw-Hill, 1994. THE AEGCL GAZETTE, EXTRAORDINARY, FEBRUARY 10, 2005

Page 99 of 100


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 Page 100 of 100 MEGHALAYA