Sharing of ISTS Losses

Transcription

1 Procedure for Sharing of ISTS Losses In accordance with Central Electricity Regulatory Commission (Sharing of Inter State Transmission Charges and Losses) Regulations, 2010 July, 2010 ational Load Despatch Centre ew Delhi

2 Contents 1. Outline Scope Methodology for Computation of Point of Connection (POC) Loss allocation factors for each Regional Entity Computation of Actual Loss in the Regional ISTS system 5 5. Moderation of estimated POC losses based on Actual losses 5 6. Application of actual losses in the scheduling Removal of Difficulties.. 9 Procedure for Sharing of ISTS Losses - 2 -

3 1. Outline 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 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 This Procedure will be implemented with effect from the date of approval by the Central Electricity Regulatory Commission herein after called Commission The procedure aims to keep computation and sharing of Loss simple and nonrecursive The % loss would be applied on regional basis in line with the present practice of regional scheduling and regional energy accounting. However, pan caking would not be there Both injection and demand Loss Allocation Factors (LAF) would be computed for each regional entity. 2. Scope 2.1. This procedure will be applicable to the all categories of Designated ISTS Customers who use the ISTS as specified in the Regulation The ISTS losses would be applied on the Regional Entities. The embedded entities would have to share additional losses for using intra-state system as applicable in the respective control area. 3. Methodology for Computation of Point of Connection (POC) Loss allocation factors for each Regional Entity 3.1. The system study carried out as per the regulations would yield: MW Losses of each zone Loss Allocation Factor Weighted average losses (%) for each region which would be then be utilized for the purpose of moderating the % losses applicable in schedules as described in following section of the procedure. Procedure for Sharing of ISTS Losses - 3 -

4 3.2. The PoC loss allocation factors (as a % of All India Loss) and PoC Loss (In MW) for each Injection and Withdrawal node/zone would be determined based on the studies and as per the methodology described in the Regulations The PoC loss allocation factors for each Regional Entity/zone would be computed by taking weighted average (weight on scheduled injection or drawal taken in the base case of the study) POC of all the nodes assigned to that Regional Entity/ zone The loss figures as obtained would then be converted to a percentage of zonal/nodal injection/withdrawal as per Annexure I. % PoC loss = (PoC Loss Allocation Factor * Total Losses [MW] in system as in study base case *100) / (Exchange ie. Generation or drawal [MW] as in base case of study) 3.5. This loss % would then be moderated as per the guidelines set out in the section 5 of this procedure Only one PoC loss % figure for each Regional Entity would be computed for entire day and thus for entire season by taking weighted average of the results for peak and other than peak cases The Regional boundaries would be as given in the para 16 of Annexure -1 of Indian Electricity Grid Code (IEGC). 4. Computation of Actual Loss in the Regional ISTS system: 4.1. The actual losses in the Regional System would be carried out for each 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) 4.2. The SEM data is collected, processed and the injection/drawal of Regional Entities/Inter-regional exchange are computed for each time block for a period of one week stating from 0000 hrs of Monday to 2400 hrs of Sunday say week w-1. This activity is done in following week say week w The actual percentage loss for each region would be computed for each 15 minute time block as per formula given in 4.1 above. Average of all such 15 minutes block Procedure for Sharing of ISTS Losses - 4 -

5 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 The Regional boundaries would be as given in the para 16 of Annexure -1 of Indian Electricity Grid Code (IEGC). 5. Moderation of estimated POC losses based on Actual losses: 5.1. The accurate estimation of transmission losses and their application in scheduling is important for Correct computation of injection and drawal schedule of various utilities Scheduled losses to be closer to actual losses in the system so that system mismatch is avoided Minimizing the mismatch between UI payable and receivable The PoC losses are estimated based on the system studies much in advance based on the representative base case and therefore, may have some degree of difference vis-a-vis actual condition of loading and losses. Thus, the moderation of these estimated losses would be required based on actual losses to meet the objectives at 5.1 and still have the sensitivities as worked out by the PoC loss calculation method as described above Since the accounting of Un-scheduled Interchange (UI) charges, pool balancing, its operation etc is carried out at regional level, the moderation of the above percentage (%) POC losses for each Regional Entity / Control Area shall be carried out at Regional level Moderation would be done based on the actual losses and percentage loss obtained form study as per equation given below : Moderated PoC Loss % = (Percentage PoC loss on Injection / Drawal) (A act /A s ) Where A act = Actual Regional Loss % based on SEM data A s = Regional Loss % based on Study The percentage PoC loss on Injection/Drawal, A act and A s would be calculated as per Annexure I 5.5. The moderated percentage (%) losses would be applicable for each DIC (Regional Entity/Control Area) on its injection/drawal in proceeding week of the computation week say for the (w+1) th week if actual loss figures are taken for (w-1) th week and computation done in w th week. Procedure for Sharing of ISTS Losses - 5 -

6 5.6. The moderated percentage transmission losses will be known in advance to all Regional Entity Control Area/DICs on a weekly basis for easy understanding by all stakeholders. This will be available on the website of implementing agency The moderated percentage loss (%) would be used by RLDCs to arrive at the injection/drawal schedules of the Regional Entities for the next day. 6. Application of actual losses in the scheduling: 6.1. Moderated Loss(%) would be used to allocate 50% of losses and balance 50% losses shall be applied to the DICs based on the Uniform Loss Allocation Mechanism Long term Transactions: The transmission losses are borne only by the drawee Regional Entities in the pre PoC charge regime for all transactions except in case of collective transactions through Power Exchanges. The scheduled energy charges for long-term transactions are also being paid at ex-power plant. Therefore in order to maintain continuity, with the pre-poc mechanism, the losses so computed would still continued to be borne in kind by the drawee Regional Entities. However, this could be changed in the future with specific approval of the commission The Net drawal schedule of a drawee Regional Entity from a injecting Regional Entity (generator) would 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. Explanation: say A, B, C and D are drawee Regional Entites with a, b, c & d moderated percentage loss. X, Y, Z are the injecting Regional Entities with 100 MW entitlement and with corresponding x, y & z moderated percentage transmission loss. Each drawee Regional Entity has a 25% share in each injecting Regional Entity and has requisitioned full power from each generator. The ex-pp schedule of A in any time block of the day would be =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 of country 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) would be shown in one separate column along with different ex-pp schedule from each Injecting Regional Entity for each 15 Procedure for Sharing of ISTS Losses - 6 -

7 minute block to the 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 would 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 Injection loss % would be applied on sale transactions and withdrawal % loss would be applied on buy transactions of a Regional Entity / Control Area Bilateral Short Term Open Access (STOA) Transactions: The procedure would be similar to the existing procedure for Collective Transactions. The drawee utility as well as injecting utility would bear the losses. For the injecting utility, scheduled injection would be transacted quantum increased by the loss quantum and for drawee utiliy it would be calculated by reducing transaction quantum by loss quantum as per its moderated percentage loss Collective Transactions The schedule in 15 minute time block of the injecting Regional Entity would equal to the transaction quantum increased by the loss quantum as per its moderated percentage loss. Similarly schedule of a drawee Regional Entity would be calculated by reducing transaction quantum by loss quantum as per its moderated percentage loss The State control Area loss would be in addition to the above ISTS losses for each embedded entity. 7. Removal of Difficulties 7.1. 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. Xxxxxxxxxx Procedure for Sharing of ISTS Losses - 7 -

8 Annexure I Total losses [MW] in the All India Network in Study = L Region / Control Area Loss Allocation Factor (%) (LAF) Control Area Injection (G) / Drawal (D) In Study (MW) MW Losses Percentage POC loss on Injection / Drawal Zone 1 LAF 1 D 1 LAF 1 * L ((LAF 1 * L)*100)/ D 1 Zone 2 LAF 2 D 2 LAF 2 * L ((LAF 2 * L)*100)/ D 2 Zone 3 LAF 3 G 1 LAF 3 * L ((LAF 3 * L)*100)/ G 1 Zone 4 LAF 4 G 2 LAF 4 * L ((LAF 4 * L)*100)/ G 2. Total Total Regional Losses (T l ) The computation would be carried out for each region A s = T l *100/ ( G ± I IR ) Note: G = Summation of all Injections in the region I IR = Summation of Inter regional Exchange of the region et PoC Loss = [0.5 * (Percentage PoC loss on Injection / Drawal) (A act /A s )] + [0.5* A act ] Where A act = Actual Regional Loss % based on SEM data A s = Regional Loss % based on Study Procedure for Sharing of ISTS Losses - 8 -