Rgmo Operation Procedure

TABLE OF CONTENTS

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Page No

1. General………:01

2. Network Security and System Operation……….:05

3. Demand Monitoring & Control Procedure………..………:16

4. Outage Planning……….:20

5. Defence Mechanisms ………...:24

6. Collective Transaction Procedures………..….:27

7. Scheduling & Despatch Procedures………..………:30

8. Grid Disturbances & Revival Procedure………..:34

9. Event Information & Reporting Procedure………...…..:37

ANNEXURES

Page No

I. Frequency Linked Despatch Guidelines……….….:42

II.

FRC-CERC Approved Procedure and Formats………:44

III. Surge Impedance Loading(SIL) of Transmission Lines……....:73

IV. Thermal loading-As per CEA Planning Criteria……….…:74

V.

NLDC Advisory on High capacity 765kV corridors…………...:76

VI. Congestion Formats………..:84

VII. UI Price Vector………..:91

VIII. List of important Grid Elements……….……..:94

IX. Procedure for Outage Planning - Proposed………..……..:115

X.

UFR & df/dt Load Shedding……….:129

XI. System Protection Schemes-All India Level………:136

XII. Islanding Schemes……….….:168

XIII. Multiple Element Outage Circular……… .….:178

XIV. Regional Power Maps………....:179

SERC - State Electricity Regulatory Commission

IEGC - Indian Electricity Grid Code

NLDC - National Load Despatch Centre

RLDC - Regional Load Despatch Centre

SLDC - State Load Despatch Centre

TTC

- Total Transfer Capability

ATC - Available Transfer Capability

TRM - Transmission Reliability Margin

ISGS - Inter State Generating Stations

ISTS - Inter State Transmission System

CEA - Central Electricity Authority

STU

- State Transmission Utilities

CTU - Central Transmission Utility

RPC

- Regional Power Committee

STOA - Short-term Open Access

MTOA - Medium-term Open Access

OCC - Operation Coordination Committee

IPP

- Independent Power Producer

DR

- Disturbance Recorder

AVR - Automatic Voltage Regulator

SVC - Static VAR Compensator

UI

- Unscheduled Interchange

NER - North Eastern Region

RGMO - Restricted Governor Mode of Operation

FGMO - Free Governor Mode of Operation

HVDC - High Voltage Direct Current

MCR - Maximum Continuous Rating (MCR)

UFR - Under Frequency Relay

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1.1

Objective:-1.1.1 Operating Procedures of National Load Despatch Centre (NLDC) document has been developed

by NLDC as per Cl. 5.1(e) of Indian Electricity Grid Code (IEGC) in consultation with the RLDCs for the guidance of the staff of NLDC. This document is brought out in line with IEGC, 2010. After that Hon’ble CERC issued amendment to IEGC principal regulation (2010) on 05/03/12.

The revision/updation of this procedure is based on amendment in various regulations, recent Orders/Regulations issued by Hon’ble Central Electricity Regulatory Commission (CERC) and recent changes in the power sector. CERC amended IEGC, UI Regulations, Grant of Connectivity, LTA & MTOA in ISTS and related matters Regulations, Terms & Conditions of Tariff Regulations, Procedure, Terms and Conditions for Grant of Trading Licence and other related matters Regulations. Also the procedure for relieving congestion in real time operation has also been revised by NLDC and approved by CERC vide its order dated 22.04.2013, Procedure for assessment of Frequency Response Characteristic (FRC) of Control Areas was approved by CERC and Manual on Transmission Planning Criteria was revised by CEA in Jan 2013. CERC has approved the detailed "Procedure for the Implementation of the Mechanism of Renewable Regulatory Fund" under Regulation 6.1 (d) of Central Electricity Regulatory Commission (Indian Electricity Grid Code), Regulations 2010 vide its order dt 09-07-13.

This procedure supersedes the earlier procedure issued by NLDC in June, 2012.

1.1.2 The real time operation of National Grid is one of the important functions of NLDC. As more and

more inter regional links are coming up and more number of 765kV lines are coming, demand rising rapidly, the task of real time grid operation is becoming more and more complex. The Indian Grid has interconnections with neighbouring countries like Bhutan and Nepal also. In India, two power exchanges are in operation as per the regulations of CERC for collective transactions and the approved procedure prepared by NLDC. The need was felt to develop the written document for the guidance of real time operator of National Grid and to develop the reference manual for day to day operation.

1.1.3 Objective of this document is to clearly spell out the procedures adopted for the integrated system

operation and roles of each agency and their responsibilities in grid operation in compliance of IEGC. This document aims at operation and development of national power system in the most efficient, economic, secure and reliable manner. This document also aims to facilitate beneficial trading opportunities to harness bottled up power.

These procedures are to be read in conjunction with the Central Electricity Regulatory Commission (Indian Electricity Grid Code) Regulations, 2010 IEGC and its first amendment-2012, CEA (Grid Standards) regulation, 2010 and respective RLDCs Operating Procedures. If any ambiguity arises in interpretation of this operating procedure, the meaning, intent and the purpose of clauses as provided in IEGC and CEA (Grid Standards) shall prevail.

1.2

Role of NLDC:-

1.2.1 National Load Despatch Centre (NLDC) has been constituted as per Ministry of Power (MOP)

notification, Government of India, under section 26(2) of the Act, dated 2nd March 2005 and is the apex body to ensure integrated operation of the national power system.

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standards specified by the Authority and Grid Code specified by Central Commission in coordination with Regional Load Despatch Centres.

c) Coordination with Regional Load Despatch Centres for achieving maximum economy and efficiency in the operation of National Grid.

d) Monitoring of operations and grid security of the National Grid.

e) Supervision and control over the inter-regional links as shall be required for ensuring stability of the power system under its control.

f) Coordination with Regional Power Committees for regional outage schedule in the national perspective to ensure optimal utilization of power resources.

g) Coordination with Regional Load Despatch Centres for the energy accounting of inter- regional exchange of power.

h) Coordination for restoration of synchronous operation of national grid with Regional Load Despatch Centres.

i) Coordination for trans-national exchange of power.

j) Providing operational feedback for national grid planning to the Authority and Central Transmission Utility.

k) Levy and collection of such fee and charges from the generating companies or licensees involved in the power system, as may be specified by the Central Commission.

l) Dissemination of information relating to operations of transmission system in accordance with directions or regulations issued by Central Government from time to time.

1.2.3

NLDC shall also carry out the following functions as per directions issued

from time to time.

a) NLDC is the nodal agency for collective transactions as per CL.5 of CERC (Open Access in Inter-State Transmission) Regulations, 2008.

b) NLDC is the implementing agency for (Sharing of Inter-State Transmission Charges and Losses) Regulations as per Cl 18.1 of the above regulation.

c) NLDC is the Central Agency for Renewable Energy Certificate(REC) mechanism vide CERC Order dated 29.01.2010.

d) NLDC would act as the Central control room in case of natural & man made

Emergency/disaster where it affects the power system operation vide MOP letter dt 27-05- 2009.

e) Any other function as may be assigned by the Commission by order or regulations from time to time.

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a) The Regional Load Despatch Centre shall be the apex body to ensure integrated operation of the power system in the concerned region.

b) The Regional Load Despatch Centre shall comply with such principles, guidelines and methodologies in respect of wheeling and optimum scheduling and despatch of electricity as may be specified in the Grid Code.

c) The Regional Load Despatch Centre shall –

a. be responsible for optimum scheduling and despatch of electricity within the

region, in accordance with the contracts entered into with the licensees or the generating companies operating in the region;

b. monitor grid operations;

c. keep accounts of quantity of electricity transmitted through the regional grid; d. exercise supervision and control over the Inter State Transmission System ; and e. be responsible for carrying out real time operations for grid control and

despatch of electricity within the region through secure and economic

operation of the regional grid in accordance with the Grid Standards and the Grid Code.

d) The Regional Load Despatch Centre may give such directions and exercise such supervision and control as may be required for ensuring stability of grid operations and for achieving the maximum economy and efficiency in the operation of the power system in the region under its control.

e) Every licensee, generating company, generating station, sub-station and any other

person connected with the operation of the power system shall comply with the directions issued by the Regional Load Despatch Centers.

f) All directions issued by the Regional Load Despatch Centers to any transmission licensee of state transmission lines or any other licensee of the state or generating company (other than those connected to interstate transmission system) or substation in the state shall be issued through the State Load Despatch Centre and the State Load Despatch Centers shall ensure that such directions are duly complied with by the licensee or generating company or sub-station. g) If any dispute arises with reference to the quality of electricity or safe, secure and integrated

operation of the regional grid or in relation to any direction given by the Regional Load Despatch Centre, it shall be referred to Central Commission for decision. However, pending the decision of the Central Commission, the directions of the Regional Load Despatch Centre shall be complied with by the State Load Despatch Centre or the licensee or the generating company, as the case may be.

The following are contemplated as exclusive functions of RLDCs

1) System operation and control including interstate transfer of power, covering contingency analysis and operational planning on real time basis;

2) Scheduling / re-scheduling of generation; 3) System restoration following grid disturbances; 4) Meter Data Processing;

5) Compiling and furnishing data pertaining to system operation;

6) Operation of regional UI pool account, regional reactive energy account and Congestion Charge Account, provided that such functions will be undertaken by any entity(ies) other than RLDCs if the Commission so directs.

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nodal agency for the short-term open access. The procedure and modalities in regard to short-term Open Access shall be in accordance with the Central Electricity Regulatory Commission (Open Access in Inter State Transmission)\Regulations, 2008, as amended from time to time.

1.4 Role of SLDC:-

In accordance with section 32 of Electricity Act, 2003, the State Load Despatch Centre

a) The State Load Despatch Centre shall be the apex body to ensure integrated operation of the power system in a State.

b) The State Load Despatch Centre shall -

a. be responsible for optimum scheduling and despatch of electricity within a State, in

accordance with the contracts entered into with the licensees or the generating companies operating in that State;

b. monitor grid operations;

c. keep accounts of the quantity of electricity transmitted through the State grid; d. exercise supervision and control over the intra-State transmission system; and

e. be responsible for carrying out real time operations for grid control and despatch of electricity within the State through secure and economic operation of the State grid in accordance with the Grid Standards and the State Grid Code.

In accordance with section 33 of the Electricity Act 2003, the State Load Despatch Centre in a State may give such directions and exercise such supervision and control as may be required for ensuring the integrated grid operations and for achieving the maximum economy and efficiency in the operation of power system in that State. Every licensee, generating company, generating station, sub-station and any other person connected with the operation of the power system shall comply with the directions issued by the State Load Depatch Centre under subsection (1) of Section 33 of the Electricity Act,2003. The State Load Despatch Centre shall comply with the directions of the Regional Load Despatch Centre.

In case of inter-state bilateral and collective short-term open access transactions having a state utility or an intra-state entity as a buyer or a seller, SLDC shall accord concurrence or no objection or a prior standing clearance, as the case may be, in accordance with the Central Electricity Regulatory Commission (Open Access in Inter-State Transmission) Regulations, 2008, amended from time to time.

1.5 Maintenance of Operating Procedures:-

These procedures shall be maintained and reviewed periodically. However, in case of urgent need arising due to operating problems, the procedures can be reviewed / revised expeditiously. NLDC will be the coordinating agency for updating/review of Operating Procedures.

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This chapter highlights the actions required to be undertaken by system operators to keep the network secured at all times against contingencies arising in the grid due to outage of critical lines, bus, generating units or other important elements of the grid. It also describes the actions required to maintain system parameters close to nominal values in day-to-day operation.

2.2 Network Security

2.2.1

Background

i) At present, the Indian power system has two asynchronous grids i.e., NEW grid comprising Northern, Eastern, North-Eastern & Western regions and SR (Southern region) grid. The NEW grid and SR Grid together caters about 120 GW of demand with a peak shortage in the range of 6000 to 10000 MW with about 2700 MU energy consumption. The NEW grid has already yielded various benefits by taking advantage of diversity of time, surplus/deficit management due to demand forecast errors/ weather variations, increased economic transactions, improvement in overall system security and efficiency due to increase in stability margin and a stiffness of about 3500 MW/Hz. The stiffness of SR grid is of the order of 2000 MW/Hz.

ii) However, synchronisation of regional grids has also resulted in evolution of different contingencies of critical nature in the grid, which has a potential to snowball in to credible contingency in the grid In addition, system may operate at times beyond the assumptions of the planner in line with various transmission security standards and associated criteria mentioned in section 3.5 of IEGC due to following reasons:

a. Planned maintenance programme of the generators and transmission lines/elements. It is imperative to ensure that such maintenance programmes are properly coordinated and do not result in reduced redundancy not envisaged during planning.

b. The events beyond the control of operators such as extreme weather conditions affecting the reliability of transmission system, uneven demand growth or delay in commissioning of generators/transmission elements.

2.2.2

Measures to ensure Network Security and Reliability

For safe and secure grid operation, it is imperative that system parameters i.e. frequency, voltage etc., remain close to nominal values. This section highlights the measures to be adopted by the System Operators at NLDC/ RLDCs / State Load Despatch Centres (SLDCs) / Inter State Generating Stations (ISGS) / substations for frequency and voltage control.

2.2.3

Frequency Control

2.2.3.1

Frequency Band:-

grid frequency within the normal IEGC band that is 49.7 Hz to 50.2 Hz currently as per IEGC Clause. 5.2(m) and as specified by the IEGC from time to time. The nominal frequency of operation in Indian grid is 50.0 Hz.

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schedule drawl whenever frequency is above 50.1 Hz and has rising trend.

ii) Each regional entity shall maintain generation under its control such that it may not generate more than its schedule whenever the system frequency is above 50.1 Hz and has rising trend and less than its schedule whenever frequency is below 49.8 Hz.

iii) In no case, entities in a region would resort to over drawl at a frequency of 49.7 Hz and below. Similarly, entities in the region should not under draw / generate more than schedule at frequency above 50.2 Hz.

iv) PRIMARY RESPONSE :- All regional entities shall ensure that the generating units synchronised with the grid provide primary response in line with sections 5.2 (f), 5.2 (g), and 5.2 (h) of IEGC.

v) SUPPLEMENTARY CONTROL:- All regional entities shall provide supplementary control in line with regulation 5.2 (i) of IEGC. Whenever frequency falls below 49.8 Hz, all partly loaded generating units, particularly of overdrawing regional entities shall pick up additional generation to control declining system frequency. The Frequency Linked Despatch Guidelines is attached as Annexure I.

vi) Sudden reduction in generator output by any entity by more than 100 MW (20 MW in case of North Eastern Region (NER)) shall be avoided particularly when frequency is falling or is below 49.7 Hz unless, under an emergency condition or, to prevent an imminent damage to the equipment.

vii) Sudden increase/decrease in load by any regional entity by more than 100 MW shall be avoided to minimize frequency fluctuation. Sudden increase in load by more than 100 MW by any regional entity, particularly when frequency is falling below 49.7 Hz. and reduction in load by such quantum when frequency is rising above 50.2 Hz. shall be avoided.

2.2.3.2. NLDC shall exchange the power between the NEW and SR grid to minimise the frequency differential between the grids in consultation with the concerned Regional Load Despatch Centre (RLDC) on opportunity basis in real-time in addition to the Inter-regional scheduled power.

2.2.3.3

Measures during high frequency conditions

Based on the scheduled load shedding programme, hydro pick up, change in STOA schedules and load ramp ups, NLDC shall anticipate possible frequency rises at the beginning of each hour and initiate advance actions.

When the system frequency is above 50.1 Hz and in the rising trend:-

i) NLDC will co-ordinate with WR, ER to export the power to SR region in case the NEW grid frequency is above 50.1 Hz and margin is available in the inter regional links and associated lines of the regions & vice versa in case the SR grid frequency is above 50.1Hz.

ii) NLDC will coordinate with all the regions to maximize the load in case of under drawl and minimise the generation based on merit order after ensuring that all pumped storage schemes are in operation in pumping mode.

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a. Instruct SLDCs to Phase out scheduled load shedding

b. Advise constituents to surrender relatively high cost entitled power from ISGS through revision of schedules.

c. Follow merit order and conserve fuel by reducing or shutting down high cost generators including IPPs.

d. Explore additional export through Short-term Open Access (STOA).

v) All regions shall stagger their rostering pattern in a manner so as to arrest stiff high frequency excursions during load changeover period.

vi) In case of persistent (based on merit order) high frequency, all regions may resort to shutting down/ backing down of generators in the event of threat to grid security as per directions of NLDC.

2.2.3.4 Measures during low frequency conditions

All regions shall carry out day ahead operational planning by balancing availability from all sources and expected demand.

When the system frequency is below 49.8 Hz and in the decaying trend:

i) All regions shall endeavour to ensure the actual net injection of ISGS generation as per their scheduled dispatch.

ii) All the regions shall ensure that their drawl from the grid is not more than their schedule by maximizing generation in line with frequency linked dispatch guidelines.

iii) NLDC would advise RLDC’s for further instructing to SLDC to restrict the over drawl at 49.8 Hz, within its schedule as per the Clause 5.4.2(a) IEGC-2010.

iv) If frequency further deteriorates and goes below 49.7 Hz and the over drawl of the region continues then NLDC shall advise the RLDCs to make arrangements that will enable manual demand disconnection to take place as instructed by RLDC/ SLDCs.

v) The measures undertaken to reduce the drawl from the grid shall not be withdrawn as long as the frequency / voltage remain at a low level unless specifically permitted by NLDC/RLDC. vi) In case of certain contingencies and / or threat to system security, NLDC may direct RLDCs

to ensure reduction of drawl by particular regional entity by a certain quantum. Such directions shall immediately be acted upon.

vii) NLDC will co-ordinate with WR, ER to import the power from SR region in case the NEW grid frequency is below 49.8 Hz and margin is available in the inter regional links and associated lines of the regions & vice versa in case the SR grid frequency is below 49.8Hz.

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200 MW and above and all hydro units of 10 MW and above (except those with upto three hours pondage), which are synchronized with the grid, irrespective of their ownership, shall have restricted governor mode of operation (RGMO) with effect from 01.08.2010.

b) The restricted governor mode of operation shall essentially have the following features. i There should not be any reduction in generation in case of improvement in grid frequency

below 50.2 Hz. ( for example if grid frequency changes from 49.3 to 49.4 Hz. then there shall not be any reduction in generation). Whereas for any fall in grid frequency, generation from the unit should increase by 5% limited to 105 % of the Maximum Continuous Rating (MCR) of the unit subject to machine capability.

ii Ripple filter of +/- 0.03 Hz. shall be provided so that small changes in frequency are ignored for load correction, in order to prevent governor hunting.

iii If any of these generating units is required to be operated without its governor in operation as specified above, the RLDC shall be immediately advised about the reason and duration of such operation. All governors shall have a droop setting of between 3% and 6%.

iv Provided that if a generating unit cannot be operated under restricted governor mode operation, then it shall be operated in free governor mode operation with manual intervention to operate in the manner required under restricted governor mode operation.

v All thermal generating units of 200 MW and above and all hydro units of 10 MW and above operating at or up to 100% of their Maximum Continuous Rating (MCR) shall normally be capable of (and shall not in any way be prevented from) instantaneously picking up to 105% and 110% of their MCR, respectively, when frequency falls suddenly. After an increase in generation as above, a generating unit may ramp back to the original level at a rate of about one percent (1%) per minute, in case continued operation at the increased level is not

sustainable. Any generating unit not complying with the above requirements, shall be kept in operation (synchronized with the Regional grid) only after obtaining the permission of RLDC.

vi The recommended rate for changing the governor setting, i.e., supplementary control for increasing or decreasing the output (generation level) for all generating units, irrespective of their type and size, would be one (1.0) per cent per minute or as per manufacturer’s limits. However, if frequency falls below 49.7Hz, all partly loaded generating units shall pick up additional load at a faster rate, according to their capability.

c) If any of the generating units are required to be operated without its governor in operation as specified above, the RLDC shall be immediately advised about the reason and duration of such operation.

d) Procedure to monitor primary response through Frequency Response Characteristic (FRC) from different control areas was submitted by NLDC and it is approved by the Hon’ble CERC through its order dt.03-05-2013. The detailed procedure is attached as Annexure II

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As defined in the IEGC Section 5.2(s), the operating range of the voltages at various voltage levels of the grid is as follows:

Voltage (kV-rms)

Nominal Minimum Maximum

765 728 800 400 380 420 220 198 245 132 122 145 110 99 121 66 60 72 33 30 36

The maximum and minimum values in the above table are the outer limits and all the regions shall endeavour to maintain the voltage level within the above limits. NLDC operators should monitor the above voltage limits across all inter regional links& important nodes and should interact with RLDCs for keeping the system voltage within the above specified limit.

As defined in the IEGC Section 5.2(J), all users and SEBs shall ensure that temporary over voltage due to sudden load rejection and the maximum permissible values of voltage unbalance shallremain within limits specified under Central Electricity Authority (Grid Standards) Regulations, 2010.

Reactive Power manual of NLDC may be referred for detailed Reactive power management and voltage control procedures.

2.2.4.2

AVRs of Generators

Generating units of all the region shall keep their Automatic Voltage Regulators (AVRs) in operation and power system stabilizers (PSS) in AVRs shall be tuned in line with clause 5.2(k) of IEGC.

2.2.4.3 VAR Exchange by regional constituents for Voltage and Reactive Control

Each constituent shall provide for the supply of its reactive requirements including appropriate reactive reserves, and its share of the reactive requirements to support safe and secure power transfer on interconnecting transmission circuits. The RLDC and constituent states shall take action in regard to VAR exchange with the grid looking at the topology and voltage profile of the exchange point. In general, the beneficiaries shall endeavour to minimize the VAR drawl at interchange point when the voltage at that point is below the nominal value and shall not inject VARs when the voltage is above the nominal value. In fact, the beneficiaries are expected to provide local VAR compensation so that they do not draw any VARs from the grid during low voltage conditions and do not inject any VARs to the grid during high voltage conditions.

2.2.4.4 VAR generation / absorption by generating units

In order to improve the overall voltage profile, the generators shall run in a manner so as to have counter balancing action corresponding to low/high backbone grid voltage and to bring it towards the

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2.2.4.5 Transformer Taps

In line with IEGC clause 6.6.5 & 6.6.4, the transformer tap positions on different 765kV, 400kV, 220kV & 132kV class ICTs shall be changed as per requirements in order to improve the grid voltage. RLDCs shall coordinate and advise the settings of different tap position and any change in their positions shall be carried out after consultation with RLDC. The modified tap position shall be informed to NLDC by RLDCs. The tap settings shall be reviewed and changed before the start of monsoon and winter and based on system requirement.

NLDC shall review and advise RLDCs on the tap position of 765/400kV ICTs periodically.

Fig:- Typical Transformer

2.2.4.6 Control of Voltage at grid substations/generating stations

Following corrective measures shall be taken in the event of voltage going high / low:-

i) In the event of high voltage (when the bus voltage going above 410 kV), following specific steps would be taken by the respective grid substation/generating station at their own, unless specifically mentioned by NLDC/RLDC/SLDCs.

a. The bus reactor be switched in

b. The manually switchable capacitor banks be taken out c. The switchable line/tertiary reactor are taken in

d. Optimize the filter banks at HVDC terminal

e. All the generating units on bar shall absorb reactive power within the capability curve f. Operate synchronous condensers wherever available for VAR absorption

g. Operate hydro generator / gas turbine as synchronous condenser for VAR absorption wherever such facilities are available

h. Bring down power flow on HVDC terminals so that loading on parallel EHV network goes up resulting in drop in voltage.

i. Open lightly loaded lines in consultation with RLDC/SLDC for ensuring security of the balanced network.

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a.Close the lines which were opened to control high voltage in consultation with RLDC/SLDC.

b. The bus reactor be switched out

c. The manually switchable capacitor banks are switched in. d. The switchable line/tertiary reactor are taken out

e. Optimize the filter banks at HVDC terminal

f. All the generating units on bar shall generate reactive power within capability curve. g. Operate synchronous condenser for VAR generation

h. Operate hydro generator / gas turbine as synchronous condenser for VAR generation wherever such facilities are available

i. Increase power flow on HVDC terminals so that loading on parallel Extra High Voltage (EHV) network goes down resulting in rise in voltage.

2.2.4.7

Load Management for controlling the Voltage

All the regions shall identify the radial feeders in their areas in consultation with SLDCs which have significant reactive drawls and which can be disconnected in order to improve the voltage conditions in the event of voltage dropping to low levels.

The details of all such feeders shall be kept ready in the respective control rooms of RLDC/SLDC and standing instruction would be given to the operating personnel to ensure the relief in the hour of crisis by disconnecting such feeders. Automatic under voltage load shedding shall commence at 380kV.

2.2.4.8

Switching off the line reactors in case of low voltage

In the event of persistent low voltage conditions, some of the line reactors are to be selected on the basis of line length, grid conditions, network topology etc. by each region which can be switched off in order to improve the system voltage profile. The switching off of such line reactors and reviving them back would be carried out as per the instructions issued by RLDCs/SLDCs.

2.2.4.9

Switching off of the lines in case of high voltage

In the event of persistent high voltage conditions when all other reactive control measures as mentioned earlier including opening of redundant HT lines with in the state system by the concerned SLDCs have been exhausted, selected 765 / 400 / 230 / 220 / 132 / 110 KV lines shall be opened for voltage control measures. The opening of lines and reviving them back in such an event would be carried out as per the instructions issued by RLDC/NLDC in real time and as per the standing instructions issued from time to time. While taking such action, RLDC/NLDC would duly consider that to the extent possible the same does not result in affecting ISGS generation as well as the system security & reliability is not affected.

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permitted from stability considerations for each line listed under important elements. RLDC would endeavour to keep the line/ ICT loadings within limits and inform NLDC in case of overloading of any element. Special emphasis would be paid by each system operator in identifying credible system contingencies & continuously evaluating the system under his control against these contingencies.

In addition to monitoring the loading of critical individual elements, the power flow across the identified flow gates shall also to be monitored and controlled with in the value specified based on the study results. All the regions hence would extend the necessary cooperation in maintaining network reliability and security.

Surge Impedance Loading of the transmission lines is given in Annexure III.

Thermal Loading limits of different conductors is given in Manual on Transmission Planning Criteria- Jan 2013’. It is attached as Annexure IV.

The advisory issued by NLDC for secure operation of the grid consequent to commissioning of the high capacity 765 kV corridors in the NEW grid is enclosed as Annexure V

2.2.6 System Protection Scheme

As per IEGC, System Protection schemes are required to take care of some special contingencies like tripping of important corridor/flow gates etc to avoid the voltage collapse, cascade tripping, load generation mismatch and finally blackouts in the system.

It will have pre identified load shedding, generation backing down/tripping of generators and inter tripping features. To ensure the healthiness of SPS, necessary checking / testing will be done by RPC secretariat periodically.

Several SPS schemes have been implemented in different regions and several schemes are being planned. It is explained in Chapter on Defense Mechanisms.

2.2.7 Islanding Scheme

In order to isolate the healthy subsystems following a large-scale disturbance, islanding schemes have been implemented by few generating stations/Users and State Utilities. This is a system requirement under contingency conditions according to which the power network may be split

into healthy and self-sustaining zones so that cascade tripping of all generating stations in the entire region is avoided. It is explained in Chapter on Defense Mechanisms.

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2.2.8

Security of Grid

In line with Central Electricity Authority (Technical Standards for Connectivity to Grid) Regulations 2007, the utilities shall make arrangements for integration of the controls and telemetering features of their system in to the automatic generation control, automatic load shedding, system protection scheme, energy management system and supervisory control & data Acquisition System of the respective State or the region.

2.2.9 Congestion Management in real time operation

Congestion management in real time operation is tackled as per CERC Regulation dated 22nd December 2009 on “Measures to relieve congestion in real time operation”. The revised

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2.2.9.1 Transfer Capability

i) Total Transfer Capability (TTC) means the amount of electric power that can be transferred reliably over the inter-control area transmission system under a given set of operating conditions considering the effect of occurrence of the worst credible contingency.

ii) Transmission Reliability Margin (TRM) means the amount of margin kept in the total transfer

capability necessary to ensure that the interconnected transmission network is secure under a reasonable range of uncertainties in system conditions.

iii) Available Transfer Capability (ATC) means the transfer capability of the inter-control area transmission system available for scheduling commercial transaction (through long term access, medium term open access and short term open access) in a specific direction, taking into account the network security. Mathematically ATC is the Total Transfer Capability less Transmission Reliability Margin

The updated ATC, TRM & ATC of all inter regional corridors and Intra Regional corridors shall be available to NLDC operator for facilitating optimum utilization.

Sample format for declaration of TTC/TRM/ATC is enclosed as Format-I is given in Annexure VI .

a) SLDCs/ RLDCs/ NLDC shall have a display available in their web-sites showing TTC, TRM, ATC declared in advance. Real time power flow in the corridor for which TTC has been declared shall be displayed alongside for comparison. The voltage of the important nodes in the grid downstream/ upstream of the corridor shall also be displayed. The display is available in the NLDC SCADA system. The same is attached as Format II in Annexure VI

A corridor shall be considered congested under the following circumstances:

i) Grid voltage in the important nodes downstream/ upstream of the corridor is beyond the operating range specified in the IEGC and/or

ii) The real time power flow along a corridor is such that n-1 criteria may not be satisfied.

iii) One or more transmission lines in the corridor are loaded beyond the normal limit specified in CEA Manual on Transmission Planning Criteria.

Whenever actual flow on inter/ intra regional link/ corridor exceeds ATC and security criteria as mentioned above are violated NLDC, RLDC may issue a warning notice. In case SLDC observes congestion within the intra State grid it shall inform the respective RLDC which in turn shall inform the NLDC. The notice for congestion shall be communicated to all the Regional entities telephonically or through fax/ voice message/ e-mail and through postings on website and making the same available on the common screen at NLDC/ RLDCs/ SLDCs. The format III of the notice is enclosed in Annexure VI

b) If the power flow on the corridor is as per the schedule, but the congestion has been caused by forced outages of a transmission line in the corridor, which occurs after the drawal schedule has

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c) If the power flow on the corridor is as per the schedule and the corridor is congested due to either of the circumstances mentioned in clauses 2.2.9.2 (a) i & iii, then TTC, TRM and ATC shall be revised accordingly.

d) If violation of TTC limits persists for 2 time-blocks not counting the time-block in which warning notice was issued by RLDC and no affirmative action by the defaulting agency is taken, NLDC/ RLDC(s) shall issue a notice for application of congestion charge. This notice shall be communicated to all the concerned Regional entities telephonically or through fax message and through postings on website and making available the same at the common screen at NLDC/ RLDCs/ SLDCs. The format IV is enclosed as Annexure VI

2.2.9.3 Applicability of Congestion Charge

a) Congestion Charge shall be applicable to Regional entities as per the CERC (Measures to relieve congestion in real time operation) Regulations and orders on rate of congestion charge as applicable from time to time.

b) At Congestion charge would be levied for

a) over drawal or under-injection in the importing control area and b) under drawal or over-injection in the exporting control area.

c) Congestion charges may also become applicable for an intra-regional corridor of one region, if the congestion is attributable to other regional entities of other region. Congestion charge shall be applicable only after two time blocks from the time of issuing the notice, not counting the time block in which notice is issued.

c) Congestion charge shall be withdrawn after the power flow on the affected transmission link/ corridor has come down to the ATC and remains at this level for one time block. NLDC/ RLDC shall communicate to all concerned Regional entities telephonically or through fax message/ e-mail and through postings on website and making available the same on the common screen available at NLDC/ RLDCs/ SLDCs for lifting of congestion charge. The format V of the notice is enclosed as Annexure VI. The various formats may be referred in the “Detailed procedure for relieving congestion in real time operation” also.

e) As per CERC notification, the congestion charge is currently at Rs.5.45 per kwh which will be applicable to all regions. The Commission may, from time to time, by order specify the rate of congestion charge applicable to whole or a part of the region.

2.2.10

Inter-regional Exchanges

NLDC shall endeavour to exchange power between the regions on opportunity basis in real-time in addition to the Inter-regional scheduled power. NLDC shall exchange power with the neighboring region on Unscheduled Interchange (UI) basis for the following.

i) In case of Grid disturbance / Grid Incidents

ii) Network contingent conditions in either of NEW and SR regions iii) Wheeling of other regions power during contingencies

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2.2.11

Contingency Evaluation

In addition to frequency and voltage control measures outlined above, each system operator at NLDC/RLDCs/ SLDCs would continuously run the Real Time Contingency Analysis (RTCA) application to identify credible contingencies, evaluate the system under his control against these contingencies and ensure immediate remedial measures for revival. All the constituents of each region should implement network applications under EMS at the earliest to facilitate the contingency evaluation. Pre-requisite for this is however the updation of network of models alongwith availability of real-time data from all the sub-stations / generating stations. Intense efforts are required from all SLDCs/RLDCs/NLDC in this direction.

2.2.12

Requirements for Solar & Wind generator

System operator(RLDC/SLDC) shall make all efforts to evacuate the available power from solar and wind and treat as a must run station. SLDC/RLDC may direct solar/wind generator to back down its generation for system security purpose or safety of personnel/equipments.

SLDC/RLDC may direct a wind farm to curtail its VAr drawal/Injection on consideration of system security or safety of personnel/equipments.

2.2.13

HVDC SET points

NLDC shall inform to all RLDCs the optimum setting of the HVDC set points of all inter- regional HVDC system.

Ramping up/down of all intra-regional Bipole and Back-Back HVDC has to be done with prior intimation of NLDC/RLDCs. .

2.2.14 Operating Manpower

The Control Rooms of NLDC, RLDCs, SLDCs, Power plants, Grid Substations shall be manned / monitored round the clock by qualified and adequately trained manpower who would remain vigilant and cooperative at all the times so as to maintain safe and secure grid operation.

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3.1 Objective

This chapter describes the procedures / responsibilities of the SLDCs for all India demand monitoring and also the steps to be taken by SLDCs for reduction of demand in the event of inadequate generating capacity and in the event of breakdown or operating problems (such as frequency, voltage levels or network elements overloading) on any part of the grid.

3.2

Overview

Demand monitoring plays a very important role in grid operation. Long term demand data (five years and beyond) is an important input for generation / transmission planning. Medium term demand data (one year and below) constitutes an important input for outage planning of generating units and transmission lines. The short term demand forecast (spanning from one week to next time block) facilitates an important input for generation scheduling. Variation in demand in real time operation from the estimated values should be within +-2% limits to ensure that the grid is not affected adversely.

Demand estimation and control is essentially the responsibility of SLDCs and RLDC/NLDC would generally not have a major role in this area except for integrating the demand value from the regions and projecting the same as national demand. NLDC however, would give instructions to RLDCs on demand control whenever the same has a bearing on the security of the national grid and such instructions would have to be complied by the SLDC’s through their respective RLDCs.

3.3

Demand estimation

3.3.1 The SLDCs would forecast demand on an annual, quarterly, monthly, weekly and ultimately on daily basis which would be used in the day ahead scheduling.

3.3.2 In line with the clause 5.3(c & d) of IEGC-2010, each SLDC shall maintain a historical database and develop methodologies / mechanism for demand estimation. The data for the estimation shall also include load shedding, power cuts etc. Similar database should be available at RLDCs and NLDC level.

3.3.3 Each State / SLDCs shall utilize the forecasting modules suitable for their system and compatible for transfer of forecasted data in the form required by RLDCs.

3.3.4 The historical database to be maintained by SLDCs/RLDCs shall also include major events vis-à-vis effect of weather forecast on the actual demand, grid disturbances and loss of major generation. Effect of weekends and other basis of historical data.

3.3.5 The annual, quarterly and monthly demand forecast would be finalized in the respective sub-committee meetings of RPCs and used in the outage plan prepared by respective RPC Secretariats in consultation with all the constituents.

3.3.6 Attention would also be paid by SLDCs in demand forecasting for special days such as important festival and national holidays having different crest and troughs in the daily load curve as compared to normal days.

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3.3.8 In the PBF technique, historical demand profile contains hourly demand data for 96 profiles consisting of recent past seven days of every calendar month and 12 special days (holidays like 15th August, 26th January etc.). In the WBF technique, a composite weather parameter representing temperature, atmospheric pressure, wind speed, wind direction, rainfall and relative humidity and corresponding demand data are stored on hourly basis in history as profile.

3.3.9 Presently, the SDF technique based on PBF is in vogue in all the region which calls for each SLDC to upload the demand forecast data for the next day by 15 hours on daily basis. It also facilitates SLDCs to incorporate changes on online basis and upload.

3.3.10 The SLDC shall take into account the wind and other renewable energy forecasting to meet active and reactive power requirement.

3.3.11It is also important that, the reactive power / Mvar requirements are forecasted right from substation level by each SLDC. The reactive power planning exercise and program for installation of reactive compensation equipments should take care of these requirements also.

3.4 Demand Control

3.4.1 The need for demand control arises on account of following conditions:

a) Variation in demand from the estimated value (by more than 2%) which can not be absorbed by the grid.

b) Unforeseen generation / transmission outages resulting in reduced power availability.

c) Heavy reactive power demand, particularly during Rabi crop season (agricultural load) / high industrial activity causing low voltages

d) Critical loading on inter-regional corridors/flow gates e) Sudden variations in Wind power generation

f) Commercial reasons such as payment default leading to regulation of power supply by generating companies

3.4.2 In line with section 5.3.(c) of IEGC, the SLDCs would regularly carry out the necessary exercises to estimate short term and long term demand to facilitate planning so as to ensure that they meet their load without overdrawing from the grid. The deviations of drawl from the schedule have to be controlled by the SLDCs in the following cases:

a) Overdrawl at frequency below 49.7 Hz b) Underdrawal at frequency above 50.2 Hz

c) Over/under drawl in line with real time advice from NLDC/RLDCs during critical contingencies in inter-regional corridors / flow gates

d) Reactive power drawls / injections causing low voltage / high voltage.

3.4.3 The constituents shall endeavour to restrict their net drawl from the grid to within their respective drawl schedule whenever the system frequency is below 49.8 Hz in line with section 5.4.2(a) of

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for helping optimum utilization of regional hydro resources so as to ensure maximum availability during peak hours.

3.4.5. All regions shall ensure the availability of the defence mechanism in place .

3.4.6. Demand control would have to be exercised under low frequency conditions by taking the following actions by regions.

a) Scheduled load shedding as decided in OCCM/Board meetings.

b) Un-scheduled load shedding for the load generation balancing exercise which is

planned for the following day. Unscheduled load shedding accounts for fluctuations in availability due to forced outages, transmission outages, fuel related problems, demand fluctuations due to weather related factors and other important events

c) Distress load shedding due to load generation imbalance in real time leading to

frequency going below 49.7 Hz. This will be carried out through already identified radial feeders. Loads may be shed under any System Protection Schemes, UFR and df/dt relays. 3.4.7. During the demand control by scheduled load shedding as well as unscheduled load shedding by

staggering in different groups, the changeover from one group to another shall be carried out in a gradual & scientific manner so as to ensure that the change in load at any point of time does not exceed 100 MW so as to avoid excursions in system parameters.

3.4.8 In the case of low voltage pockets, RLDC/SLDCs would disconnect the preidentified radial feeders drawing heavy quantum of reactive power which are not feeding the important loads like Traction, Hospital, Defence etc. when voltage goes below 380kV.

3.4.9 Each User/STU/SLDC shall formulate contingency procedures and make arrangements that will enable demand disconnection to take place, as instructed by the RLDC/SLDC, under normal and/or contingent conditions. These contingency procedures and arrangements shall regularly be / updated by User/STU and monitored by RLDC/SLDC. RLDC/SLDC may direct any User/STU to modify the above procedures/arrangement, if required, in the interest of grid security and the concerned User/STU shall abide by these directions.

3.4.10 The SLDC through respective State Electricity Boards/Distribution Licensees shall also formulate and implement state-of-the-art demand management schemes for automatic demand management like rotational load shedding, demand response (which may include lower tariff for interruptible loads) etc. before 01.01.2011, to reduce overdrawl in order to comply para 5.4.2 (a) and (b) . A Report detailing the scheme and periodic reports on progress of implementation of the schemes shall be sent to the Central Commission by the concerned SLDC.

3.4.11 In order to maintain the frequency within the stipulated band and maintaining the network security, the interruptible loads shall be arranged in four groups of loads, for scheduled power cuts/load shedding, loads for unscheduled load shedding, loads to be shed through under frequency relays/ df/dt relays and loads to be shed under any System Protection Scheme identified at the RPC level. These loads shall be grouped in such a manner , that there is no overlapping between different Groups of loads. In case of certain contingencies and/or threat to system security, the RLDC may direct any SLDC/ SEB/distribution licensee or bulk consumer connected to the ISTS to decrease drawal of its control area by a certain quantum. Such

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3.5

Operational planning on day ahead basis

3.5.1 In line with clause 6.5 of IEGC under the head of ‘Scheduling & Despatch Procedure’,plant-wise requisitions from the States are compiled a t e a c h R L D C s to draw up scheduled for each ISGS. The day ahead operational planning exercise helps the state with large deficit to opt for un-requisitioned power in some of the ISGS plants within or outside the region.

3.5.2 The state utilities bridge the anticipated shortfall by day-ahead Short Term Open Access transactions/collective transactions (PX trades).

3.6

Day Ahead Balancing

3.6.1 The day ahead power balance cann ot be obtained without planning for load shedding in case of deficient power region. Out of the total deficits for the following day, the scheduled load shedding takes care of a major portion of the deficits and is planned and frozen atleast a month in advance and announced to public. The balance part of the deficit is taken care of through planning of unscheduled load shedding.

3.6.2 Unscheduled load shedding accounts for fluctuations in a v a i l a b i l i t y due to forced outages, transmission outages, fuel related problems, demand fluctuations due to weather related factors and other important events

3.7

Same Day Operational Planning

3.7.1 On the day of operation, due to errors in demand forecast, forced outage of units, some of the States or Central Sector Plants, sellers/buyers of Short Term Open Access transactions (advance reservations and first-cum-first serve basis only) may revise their schedules – one and half hour ahead for planned deviations and one hour ahead for unforeseen problems.

3.7.2 The deviations from schedules in any region may require purchase/sell of balancing power from the other power surplus regional to power deficit regional pool at a rate determined by UI price vector. This price vector is given in Annexure VII.

3.8 Load Crash

In the event of load crash in the system due to weather disturbance or other reasons, the situation would be controlled by SLDCs / ISGS by the following methods:-

a) Lifting the load restrictions, if any.

b) Exporting the power to neighbouring regions by STOA c) Phasing out hydro

d) Backing down or closing down of generating units

Further in case of hydro generation linked with irrigation requirements, the actual backing down or closing down of units shall be subject to limitations on such account.

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a) This section brings out the process for preparation of outage schedules for generators and transmission lines at the national level subject to network security, constraints and reliability. The general guidelines shall be as per section 5.7 of the IEGC. NLDC operator should be familiar with all important transmission lines given in Annexure VIII and generation units covering the entire national grid and effecting the operation of the national grid concerning its security, integrity and economy facilitating optimum utilization of all national resources. While planning for generation outages and transmission line outages due consideration shall have to be made for long term commitments, medium and short term commitments including transactions that are settled through multiple Power Exchanges.

b) Outages effecting network security on a Pan-India scale shall have to be planned meticulously and Power System Studies have to be carried out for this purpose.

c) Annual outage plan shall be prepared in advance for the financial year by the RPC Secretariat in consultation with NLDC and RLDC and reviewed during the year on quarterly and Monthly basis. All users, CTU, STU etc shall follow these annual outage plans. If any deviation is required the same shall be with prior permission of concerned RPC and RLDC. The outage planning of run-of-the-river hydro plant, wind and solar power plant and its associated evacuation network shall be planned to extract maximum power from these renewable sources of energy. Outage of wind generator should be planned during lean wind season, outage of solar, if required during the rainy season and outage of run-of-the river hydro power plant in the lean water season.

4. 2 Objective

a) To produce a coordinated generation and transmission outage programme for the National/Regional grid, considering all the available resources and taking into account transmission constraints, as well as, irrigational requirements.

b) To minimise surplus or deficits, if any, in the system requirement of power and energy and help operate system within Security Standards.

c) To optimize the transmission outages of the elements of the National/Regional grid without adversely affecting the grid operation but taking into account the Generation Outage Schedule, outages of User/STU/CTU systems and maintaining system security standards.

4.3 Scope

This section is applicable to NLDC, RLDC, SLDCs, CTU, STU, RPCs and all Users

4.4 Outage Planning Process

a) The RPC Secretariat shall be primarily responsible for finalization of the annual outage plan for the following financial year by 31st January of each year.

b) All SEBs/STUs, transmission licensees, CTU, ISGS IPPs, MPPs and other generating stations shall provide RPC Secretariat their proposed outage programmes in writing for the next financial year by 30th November of each year. These shall contain identification of each generating unit/line/ICT, the preferred date for each outage and its duration and where there is flexibility, the earliest start date and latest finishing date.

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system studies and, if necessary, the outage programmes shall be rescheduled. Adequate balance between generation and load requirement shall be ensured while finalising outage programmes. The same shall be uploaded by the RPCs on their website.

d) The outage plan shall be finalized in consultation with NLDC, RLDCs and SLDCs. The final outage plan shall be intimated to NLDC, Users, STUs, CTU, other generating stations connected to ISTS and the RLDC for implementation by 31st January of each year.

e) The above annual outage plan shall be reviewed by RPC Secretariat on quarterly (March, June, September & December) and monthly basis in coordination with all parties concerned, and adjustments made wherever found to be necessary. Monthly review of the outage plan for the current month and consecutive month would be done in the Operation Coordination Committee (OCC) of RPC meeting and RPC would issue the revised outage plan to all constituents and RLDC/NLDC/SLDC.

f) In case of emergency in the system, viz., loss of generation, break down of transmission line affecting the system, grid disturbances, system isolation, RLDC may conduct studies again before clearance of the planned outage.

g) The NLDC/RLDC shall be authorized to defer/ cancel any planned outage involving lines/elements in case of any of the following taking into account statutory requirements:

i. Grid disturbances ii. System isolation

iii. Partial Black out in a state

iv. Any other event in the system that may have an adverse impact on the system security by the proposed outage.

h) The detailed generation and transmission outage programmes shall be based on the latest annual outage plan (with all adjustments made to date).

i) Each User, CTU and STU shall obtain the final approval from RLDC/NLDC prior to availing an outage.

j) RPCs shall submit quarterly, half-yearly reports to the Commission indicating deviation in outages from the plan along with reasons. These reports shall also be put up on the RPC website.

k) A Draft procedure for coordinated transmission element outage planning is proposed by NLDC to all RPCs through letter dt. 28th February 2013. Subsequently, a letter dt 05-07-2013 also sent to RPCs. It is given in Annexure IX. And after getting approval from all the RPCs, it should be implemented. The draft procedure aims to streamline the process of outage coordination between SLDCs, RLDCs, NLDC, RPCs and Indenting Agencies.

4.5

Availing Outage

a) NLDC/RLDC would review the outage schedule on daily basis and in case of any contingency or any conditions described under IEGC clause 5.7.4(g), defer any planned outage as deemed fit. The revised dates in such case would be finalized in consultation with the concerned constituents or OCC meetings.

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c) Before availing any planned or unforeseen outage of any important elements as per Annexure VIII the indenting utility shall request for a code on real-time from NLDC through respective RLDC under whose supervisory area the utility remains. NLDC shall issue a common code to concerned RLDC’s involving regional grids on either end of the line. Respective RLDC’s may convey their final code to NLDC as well as their respective utilities involved on either ends of the transmission line/equipment. All preparatory works for availing outage must be done in advance before actually availing code. In the same manner code must be obtained in real-time from NLDC by concerned utility through it’s RLDC before restoration/revival of the line/element. Respective RLDC’s shall convey their final code to NLDC for confirmatory exchange with other RLDC’s involved. RLDC would ensure that the outage availed should come into service as per the scheduled time. Delays with reasons thereof if any should be immediately reported to NLDC in advance. During shutdown RLDC may concur for extension of such shutdown after reviewing the grid conditions and status of shutdown.

d) The code issued by NLDC / RLDC’s for opening / restoration of line / element is consent from operational point of view notwithstanding anything contained in respect of safety measures and switching operations that may be carried out locally. All safety measures related to sub-station and/or transmission lines shall be the responsibility of the personnel authorized to execute the work.

e) During the approved shutdown of line/ICT, any other opportunity based maintenance work by the concerned agencies to be carried out only after getting the consent of RLDC/NLDC.

4.6

Outage Planning Procedures for NLDC Important elements

i) In order to maintain the security of the Integrated power system, it is important that the planned outage of generation and transmission system particularly in the important flow-gates, Important grid elements and inter regional transmission links are properly coordinated.

ii) Reliable operation of the All India grid is important from the view point of Quality Of Service (QoS) to the customers and other stakeholders. Proper co-ordination of transmission outages in the system is one of the key aspects to ensuring reliability. Outages in the transmission network could either be on account of planned maintenance activities or construction related activities or any emergency conditions arising in the field. Since these may have an impact across two or more regions and hence needs to be planned by the concerned regions in consultation with NLDC. Proper coordination of the same is important mainly due to the following factors:

a. Reliability of operation of the All India grid b. Certainty to the electricity markets.

c. Proper crew resource mobilization at the work sites to ensure that outage time is minimized. iii) In order to ensure the same, the following procedures may kindly be followed by all

RLDCs/NLDC.

1) Following outages might be approved only after concurrence of NLDC. This is enclosed as Annexure VIII

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 Trans National Links

2) At the RPC level, outages are finalized in the Operation Coordination sub Committee (OCC). A list of the shutdowns approved by OCC may be forwarded by each RLDC to the Reliability Coordinators of each RLDC and NLDC by email immediately after OCC approval.

3) On a daily basis (say day D), by 1030 hours each RLDC would forward a list of outages planned for their respective regions for the D + 3rd day by email to the Reliability Coordinators of each RLDC/NLDC along with the study results.

4) The NLDC Reliability Coordinators would further assess the impact of these outages on the overall reliability of the all India grid and concurrence of outages under categories listed at (1) above would be conveyed by NLDC within a day.

5) All planned shutdowns on the next day would be reviewed a day in advance of the shutdown. RLDCs would try to ensure that no new element gets added to the list provided three days in advance at Sl. no. 3 above as far as possible, unless the outage is of an emergency nature.

6) A list of all the outages approved for the next day would be readily available at each RLDC/NLDC control room along with simulation results, if any and the precautions required to be taken.

7) In real time if any emergency requirement of outage occurs in real time, RLDCs would inform NLDC and actions taken accordingly in real time. RLDCs/NLDC might devise separate internal procedures for fast co-ordination between their respective Control Rooms and Reliability Co-ordinators in real time.

8) Any deviation in the outage from the schedule can affect other planned outages as well as affect reliability and also the electricity markets. RLDCs may impress on the agencies intending for an outage to strictly adhere to the shutdown timings.

9) A record may be kept of outage overshooting the approved time of return to bring in seriousness and to avoid market distortion.

10) It is therefore necessary to carry out operational studies in order to assess the grid security and network stability while finalizing the annual outage plan of these important elements.