P350 TLFA process: Consultation on Methodology for LP and SSP 2024-2025
This consultation details the proposed methodology for setting Load Periods and Sample Settlement Periods used in the derivation of Zonal Transmission Loss Factors (TLFs), as required by the Balancing and Settlement Code (BSC). New values are set each year, and views are sought from the Transmission Company and BSC Parties on continuing to use the same method as for previous years.
Status
Who will this impact?
Modification P350 ‘Introduction of a seasonal Zonal Transmission Losses scheme’ introduced a Transmission Loss Factor (TLF) for each TLF Zone and BSC Season, so transmission losses can be allocated on a geographical basis. P350 went live on 1 April 2018.
Transmission Loss Factors (TLFs) are set by Elexon for each TLF Zone and BSC Season . The TLF Zones are aligned with the existing Grid Supply Point (GSP) Groups so transmission losses can be allocated on a geographical basis, as part of modification P350 (implemented on 1 April 2018).
This Consultation details the proposed methodology for setting Load Periods and Sample Settlement Periods to be used in the derivation of Zonal TLFs, as required by the Balancing and Settlement Code (BSC).
What is proposed?
Elexon proposes that ISG use the same methodology as previous years. The methodology instructs Elexon to:
- Divide the BSC Year into Electricity Forward Agreement (EFA) Days (23.00 – 23.00), and group the EFA Days within each week into blocks of consecutive Working and Non-Working Days. This divides the BSC Year into circa 104 blocks of consecutive EFA Days, with each week having a block with five Working Days and a block with two non-Working Days (except where there are Bank Holidays).
- Split each of these blocks into six time bands, corresponding to the six four-hour blocks within the EFA Day. Each time band, within each block of days, is a LP, so there will be circa 624 LPs within the Reference Year.
- SSPs are then randomly selected from each LP, with one SP taken from EFA Block 1, one from EFA Block 2, but two SPs from each of the remaining four EFA Blocks (The variability in demand is less in EFA Band 1 – 2 compared to the values in Bands from 3 to 6). This means the total number of SSPs in the Reference Year will be circa 1040.
The sample (1,040 Settlement Periods from 17,520) will be large enough to be statistically representative, and increasing it further would require a change to the TLFA contract.