Modification P350 ‘Introduction of a seasonal Zonal Transmission Losses scheme’ goes live on 1 April 2018

On 1 April 2018 BSC Modification P350 ‘Introduction of a seasonal Zonal Transmission Losses scheme’ will come into effect. P350 will introduce a Transmission Loss Factor (TLF) for each TLF Zone for each BSC Season in order to allocate transmission losses on a geographical basis. TLFs will first be used in the Initial Information Settlement Run for April 2018 Settlement Day 1 on 9 April 2018. Please see the P350 Implementation page of our website for further information.

To further support our customers, we have added a new file, ‘BM Unit Specific TLF Values for Year 2018-19 Spring Part A V1.0’, to the TLFs Determination page of the ELEXON Portal. This file provides the Transmission Loss Factor (TLF) for each BM Unit that is registered to be active during the period 1 April 2018 to 31 May 2018. The file will be updated as a result of any subsequent BM Unit registrations and/or de-registrations that will be effective during this period. We will change the version number in the file name whenever the content changes in the file.

We will add ‘BM Unit Specific TLF Value’ files for subsequent BSC Seasons and BSC Years to this page before the start of the relevant BSC Season.

For further information please email For an overview of BSC Modification P350 and the introduction of a seasonal Zonal Transmission Losses scheme, watch the webinar on our YouTube channel.


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