As energy is transported from the point of production to the end user, some of it is lost. Under the BSC arrangements there are two ways in which these losses are accounted for:

  • Losses on the Distribution Networks are allocated through the use of Line Loss Factors (LLFs).
  • Losses on the Transmission System are allocated across BSC Parties through the use of Transmission Loss Multipliers (TLMs).
  • Line Loss Factors (LLFs)

    Line Loss Factors are multipliers which are used to scale energy consumed or generated to account for losses on the UK’s Distribution Networks. LLFs are applied in both Central Volume Allocation (CVA) LLF and Supplier Volume Allocation (SVA) LLF. 

    • Supplier Volume Allocation
      SVA LLFs are used in aggregation by the Half Hourly Data Aggregator (HHDA) for Half Hourly (HH) Metering Systems and Supplier Volume Allocation Agent (SVAA) for Non Half Hourly (NHH) Metering Systems. There are roughly 30 million Metering Systems registered in the Supplier Meter Registration Service (SMRS) – the SVA sector of the electricity industry. Many of these are banded together into Line Loss Factor Classes (LLFCs). The Licenced Distribution System Operators (LDSOs) use these for assigning Metering Systems to a given tariff, for the purpose of Distribution Use of System (DUoS) charges. All Metering Systems in a LLFC will have the same LLF value. The LDSOs need to submit SVA LLF values for all LLFCs on an annual basis, and also for a new LLFC when it is being registered.
    • Central Volume Allocation 
      CVA LLFs are multipliers used to scale Meter readings taken at an Embedded site to an equivalent value at the Transmission System Boundary and also to the LLFs account for the losses on the Distribution System. They are applied at a Metering System ID (MSID) level via site Aggregation Rules. A full list of current site names, along with their MSID and GSP Group, can be found in our MSID Site Names list. LDSOs need to submit values for each site which requires CVA LLFs on an annual basis. They will also need to submit LLFs for any new sites registered within CVA that use LLFs in their Aggregation Rules.

    Processing of CVA and SVA LLFs

    All LLFs submitted by LDSOs will be processed in accordance with BSCP128 ‘Production, Submission, Audit and Approval of Line Loss Factors’.

    The LDSOs provide a LLF methodology statement that explains how they calculate the LLFs. The statements are reviewed against the principles in BSCP128. If the methodology meets the principles, we present it to the ISG and SVG for approval. The LDSOs then calculate LLFs which need to be audited by ELEXON and approved by the ISG and SVG before being used in Settlement.

    Where can I find the methodologies and Line Loss Factor Data?

    The latest approved methodology statements and LLFs are available on the ELEXON Portal.

    For more information on Line Loss Factors, please contact Paulina Stelmach on 0207 380 4372.

  • Transmission Losses (TLMs)

    Under the BSC arrangements, TLMs are applied to non-Interconnector Balancing Mechanism (BM) Unit Metered Volumes as a means of scaling to account for losses on the Transmission System. The formulas for calculating TLMs are set out in BSC Section T, Paragraph 2.3.1.

    There are only two values for TLM per Settlement Period: one for BM Units belonging to Trading Units that are off-taking in the Settlement Period, and one for BM Units belonging to Trading Units that are delivering in the Settlement Period. The Transmission Loss Factor (TLFij), used in the calculation of TLM, is zero for all BM Units.

    Historic Transmission Loss Multipliers data can be downloaded from the ELEXON Portal, as well as historic Estimated Transmission Loss Adjustment (ETLMOs), which are indicative parameters set for the purposes of  Balancing Mechanism Reporting Service (BMRS) reporting. These parameters are the estimated values of the ‘Delivering Transmission Losses Adjustment’ (TLMOj+), and the ‘Off taking Transmission Losses Adjustment’ (TLMOj-). The ISG reviews the ETLMO values annually on behalf of the BSC Panel.

    The BMRS is used to display near real-time information relating to the operation of the BM.

    For more information on Transmission Losses, please contact Riccardo Lampini on 0207 380 4172.