Central Electricity Regulatory Commission

Procedure for

Sharing of ISTSLosses

In accordance with

Central Electricity Regulatory Commission

(Sharing of Inter State Transmission Charges and Losses)

Regulations, 2010

March, 2011

National Load Despatch Centre

New Delhi

Contents

1.Outline and Scope…………………………………………………………….. 3

2.Objective………………………………………………………………………. 3

3.Computation of Generation/Demand Zone loss..……………………….….. 4

4.Computation of ISTS losses with the help of data from Interface Meters.. 5

5.Computation of moderation factor…………………………………………. 5

6.Computation Uniform Loss………………………………………………….. 6

7.Application of losses while scheduling of contracts…………………………..7

Removal of Difficulties…………………………………………………………. 9

Outline and Scope

1.1.This Procedure is issued in compliance with Regulation 6(1) “Central Electricity Regulatory Commission (Sharing of Inter State Transmission Charges and Losses) Regulations, 2010 herein after called “the Regulation”.

1.2.This procedure is issued for bringing in detailed methodology for application of the ISTS transmission losses to different DICs on their scheduled transactions using ISTS.

1.3.This Procedure will be implemented with effect from the date of coming ito force of the Central Electricity Regulatory Commission(Sharing of Inter State Transmission Charges and Losses) Regulations, 2010.

1.4.This procedure describes the application of transmission losses during scheduling of all categories of transactions involving usage of ISTS viz. Long-term, Medium term and Short-term contracts.

1.5.The ISTS losses as arrived through this procedure shall be applied on the Regional Entities in line with Regulation 3 of Central Electricity Regulatory Commission (Sharing of Inter State Transmission Charges and Losses) Regulations, 2010. The entities embedded within the State jurisdiction shall have to share additional losses for using intra-state system as applicable in the respective control area.

Objective

2.1.The procedure aims to keep computation and sharing of Loss simple and non-recursive.

2.2.The % loss shall be applied on regional basis to harmonise with the regional scheduling and regional energy accounting.

2.3.The system studies based on hybrid methodology shall be carried out separately for the truncated network of the NEW grid and the truncated network of the Southern Grid till they are asynchronously connected.

2.4.These studies would yieldPoC charges as well as loss allocation factors for each generation/demand node and the total study losses for the truncated network of the respective grids.

2.5.In line with the philosophy of application of PoC charges on injection as well as withdrawal, loss shall be computed separately for injection and for withdrawal. Thus the percentage loss for injection in a zone would be distinct from the percentage of loss for withdrawal in a zone.

2.6.The MW loss allocated to a generation and demand node for peak and other than peak network conditions for each block of monthswould be obtained from the studies. However for application of losses to each generation and demand zone during scheduling of various transactions, a single set of percentage loss based on the weighted average of peak and other than peak conditions shall be used.

Till such time as the Commission directs, only one set of studies for the year shall be carried out considering average load and generation scenario.

2.7.The studiesare carried out with anticipated network conditions and anticipated load-generation scenario. The actual scenario in the application period may be in variance with the anticipated scenario. Therefore, the losses computed from the studies shall be moderated on a weekly basis with the help of average losses computed from the Special Energy Meter data.

2.8.Losses shall be settled in kind for all types of transactions involving usage of ISTS. The losses shall be applied ex-ante and there shall be no post facto truing up of losses.

Computation of Generation/Demand Zone loss for a block of months

3.1.The system studies based on hybrid methodology shall be carried out for peak as well as for other than peak scenario for respective block of months (seasons).

Till such time as the Commission directs, only one set of studies for the year shall be carried out considering average load and generation scenario.

3.2.These studies would yield inter alia, loss allocation factors for each generation/demand node as well as the total study losses for the respective truncated networks.

3.3.The total study lossesshall be apportioned to each generation/demand node in the synchronous gridby multiplying the total study losses with corresponding loss allocation factors.

3.4.Geographically and electrically contiguous nodes within a synchronous grid shall be clustered as per the Regulation to create demand/generation zone. These zones shall be same as those created for applying the Point of Connection Charges.

3.5.The MW loss for the generation nodes within a zone and the MW loss for the demand node within that zone shall be aggregated separately.

3.6.The percentage loss forinjection in a zone shall be obtained by dividing the aggregate MW loss of each injecting node in that zone by the aggregate injection of the zone.The percentage loss for withdrawalin a zone shall be obtained by dividing the aggregate MW loss of each demand node in that zone by the aggregate demand of the zone.

3.7.A single set of percentage loss for the entire day shall be obtained by computing a weighted average of the percentage loss for injection/withdrawalpertaining to thepeak and off-peak scenario would be computed. The number of hours in the peak (i.e. 8 hours) and other than peak (i.e. 16 hours) shall be used as weights for this purpose.

3.8.The percentage loss for injection in a zone and the percentage loss for withdrawal in a zone shall be moderated prior to their application in scheduling of contracts. The computation of moderation factor is elaborated in sections ahead.

Computation of ISTSlosses with the help of data from Interface Meters

4.1.The injection and drawal in the ISTS by the Regional Entities is metered with the help of Special Energy Meters (SEMs) installed at their interface boundary with ISTS.The SEM data is collected and processed weekly for the previous week stating from 0000 hrs of Monday to 2400 hrs of Sunday.

4.2.The actual losses in the NEW grid/ SR System would be computed from the 15 minute time block based on data of Injection/drawl of Regional entities and Inter-regional exchanges as computed from Special Energy Meters (SEMs) data installed at various Regional Entities boundary. The actual losses would as per the following formula:

Actual Transmission losses (in MWh) in Regional ISTS, L =

(∑Injection of Regional Entities G + ∑Interregional injection I) - (∑Regional Entity drawals +∑Inter-regional drawals)

Actual Percentage Regional losses, l = L*100/ (G+I)

4.3.The actual percentage loss for NEW grid/ SR would be computed for the entire week as per formula given in 4.1 above. Average of all such 15 minutes block in a week would give percentage (%) actual loss of the region for that week say week w-1 and would be used for moderation of PoC Losses.

4.4.The Regional boundaries would be as given in the para 16 of Annexure -1 of Indian Electricity Grid Code (IEGC).

Computation of moderation factor

5.1.It is desirable that the estimated transmission losses to be applied for scheduling various contracts be as near to the actual transmission losses as far as possible for the following reasons:

a)For providing reasonable certainty to the DICs.

b)To minimize the mismatch in load and generation in real-time operation

c)To minimize the mismatch between payables and receivable in the Unscheduled Interchange pool.

5.2.The total study lossin a region shall be divided by aggregate of the MW injection at all nodes in the region to arrive at the percentage study loss (As) of the regional system.

5.3.Percentage ISTS losses in a regionalsystemcomputed with the help of data from Interface Meters shall be obtained by dividing the Actual Transmission Losses (La, in MWHr) in ISTS by aggregate of Injection by Regional Entities (G) in the synchronous system and Injection from inter-regional links (I),

Aact = La*100/ (G+I)

5.4.The moderation factor shall be computed by dividing the percentage actual loss (Aact) of the regional system by the percentage study loss (As).

Moderation factor = Aact /As

where

Aact = Actual Loss % in the synchronous system based on SEM data

As =Regional Loss % based on Study

5.5.The moderation factor computed for week ‘w-1’ shall be used for scheduling in week ‘w+1’

5.6.The moderation of losses and its application in scheduling shall be done by Regional Load Despatch Centre (RLDC) and the applicable percentage loss for generation/demand zone of each Designated ISTS Customer (DIC) shall be published on the website of NLDC/RLDCs.

5.7.The moderatedpercentage loss for injection/withdrawal in a zone shall be obtained by multiplying the percentage loss for injection/withdrawal with the moderation factor. These figures shall be known ex ante.

Computation Uniform Loss

6.1.The Uniform loss is the percentage loss applied uniformly to all DICs in a region irrespective of their location in the grid.

Uniform Losses (UL) = Aact

Aact is actual loss percentage as computed in section 4.

Application of losses while scheduling of contracts

7.1.As per the Regulation 7 (s), for the first two years, while allocating losses to the DICs in scheduling Moderated Loss (%) shall be used to allocate 50% of losses and Uniform Loss shall be used for allocating the balance 50% losses.

Effective PoC Loss = 0.5 *Moderated % loss for injection or withdrawal + 0.5*UL

7.2.Scheduling of Long term Transactions

The effective PoC loss is applicable on injection as well as on withdrawals separately. However application to the long term contracts would require amendment to the Long term Power Purchase Agreements. Till such time, as an adhoc arrangement, the effective PoC loss applicable to the injection by inter-state generating stations shall be borne by the drawee regional entity having entitlement in such generating stations. This is also in line with Regulation 8 (6), wherein it has been specified that the long term customers availing supplies from inter-state generating stations, the charges payable by such generators for such Long term supply shall be billed directly to the respective Long Term customers based on their share of capacity in such generating stations.

The Net drawal schedule of a drawee Regional Entity from a injecting Regional Entity (generator) shall be computed by deducting the moderated % loss applicable to respective Injecting (generator) Regional Entity as well as its own moderated % loss from the corresponding ex-power plant scheduled of that drawee Regional Entity from the injecting Regional Entity as illustrated below:

Explanation:Say X, Y, Z are the injecting Regional Entities (Installed Capacity of 100 MW) with corresponding effectivePoC lossfor injection in the respective zones as x, y & z. Let A, B, C and D be drawee Regional Entites with a, b, c & effectivePoC loss for withdrawal in the respective zones. If each drawee Regional Entity has a 25% share in each injecting Regional Entity and has requisitioned full power from each generator then the ex-PP schedule of A in any time block of the day would be 25+25+25 =75 MW. The net drawal schedule of A at its periphery with ISTS in same block would be 25*[(1-x/100)* (1-a/100)] + 25*[(1-y/100)* (1-a/100)] + 25*[(1-z/100)* (1-a/100)].

In case the Injecting Regional Entity say X is located in a region other than that of drawee Regional entity say A,the inter-regional boundary schedule for this transaction would be 25* (1-x/100) MW. If this transaction involves a wheeling region also, then the schedule at both exporting to wheeling and wheeling to importing region boundary would be same as above.

The total losses attributable (including that of Injecting Regional Entities corresponding to its share in them) shall be shown in one separate column along with different ex-PP schedule from each Injecting Regional Entity for each 15 minute block to compute the net drawal schedule of the drawee Regional Entity in that block.

The total losses attributable to a injecting or generator Regional Entity Control Area shall also be shown in separate column alongwith its Declared Capability (in case of two part tariff stations) and ex-PP scheduled MW for each 15 minute time block.

7.3.Scheduling of Medium term transactions

Example: Let contracted quantum is P. EffectivePoC lossof the injecting entity be ‘a’ and that of drawee entity be ‘b’, then the Injecting entity has to inject P/(1-a/100) and drawee entity will be scheduled to draw P*(1-b/100).

In case the entity is embedded within a State Control Area, loss in that State control Area loss shall be in addition to the above ISTS losses for each embedded entity i.e. the schedule of injecting utility shall be further scaled up by the applicable losses of the state and the schedule of the drawee entity shall be further scaled down by the applicable losses of the state.

7.4.Scheduling of Bilateral and Collective STOAtransactions

For all transactions under this category, both the Injecting entity and drawee entity have to share the losses. Accordingly the injecting utility will have to inject contracted quantum of power and additionally its applicable losses. Similarly the drawee entity has to draw contracted quantum of power after deducting its applicable losses. The State control Area loss shall be in addition to the above ISTS losses for each embedded entity i.e. the schedule of injecting utility shall be further scaled up by the applicable losses of the state and the schedule of the drawee entity shall be further scaled down by the applicable losses of the state.

7.5.Computation of Inter-Regional Schedules

The losses applicable to an injecting entity shall be determined by the percentage injection loss for the zone where the injecting node is located. Likewise the losses applicable to a withdrawing entity shall be determined by the percentage withdrawal loss for the zone where the withdrawing node is located. Thus there shall be no pan caking. However the computation of schedule at the inter-regional boundaries is illustrated below:

Example: Let the Injecting Entity is located in Region-1 and the power is wheeled through Region-2 and the Drawee entity is located in Region-3.

Let contracted quantum be P.

Effective PoC Loss percentage of the injecting entity in Region-1 be ‘a’ and that of drawee entity in Region-3be ‘b’.

Then the Injecting entity has to inject P/(1-a/100)

The Schedule at the Inter-Regional boundary between Region-1 and Region-2 shall be P and that between Region-2 and Region-3 shall also be P. That means there is no separate loss for Region-1, Region-2 and Region-3.

The schedule of drawee entity will be P*(1-b/100).

8.Removal of Difficulties

8.1.In case of any difficulty in implementation of this procedure is experienced, this procedure shall be reviewed or revised by NLDC with prior approval from the Commission.

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Annexure-I

Total losses [MW] in the All India Network in Study = L

Region/
Control Area / Loss Allocation Factor
(LAF) / MW Losses / Control Area Injection (G) / Drawal (D)
In Study
(MW) / Percentage POC loss on Injection / Drawal
Zone 1 / LAF1 / LAF1 * L / D1 / ((LAF1 * L)*100)/ D1
Zone 2 / LAF2 / LAF2* L / D2 / ((LAF2* L)*100)/ D2
Zone 3 / LAF3 / LAF3* L / G1 / ((LAF3* L)*100)/G1
Zone 4 / LAF4 / LAF4* L / G2 / ((LAF4* L)*100)/G2
………….
Total / Total regional Losses
(L) / As = L *100/
(∑G± ∑IIR)

Note:

∑G = Summation of all Injections in the region

∑IIR = Summation of Exchange on inter-regional links

Effective PoC % Loss for Injection = 0.5 *(Moderated Percentage PoC loss on Injection)

+ 0.5* UL

Effective PoC % Loss for Drawal = 0.5 *(Moderated Percentage PoC loss on Drawal)

+ 0.5* UL

Where

Aact = ISTSLoss % in a synchronous system based on SEM data

As =ISTS Loss % based on Study

UL = Uniform Loss (%)

Procedure for Sharing of ISTS Losses- 1 -