Transmission Losses data from the Trading Operations Report


The page below details highlighted Transmission Losses data from the previous month. This data is acquired from BSC Agents and inputted to the Trading Operation Monitoring Analysis System (TOMAS) database.

The graphs may take a couple of seconds to load. To expand the graphs, tap the double-headed arrow in the bottom right corner of the graph.

Daily Average Offtaking TLM

The chart below shows the daily average Offtaking Transmission Loss Multiplier (TLM) based on the II Run or later. Following the implementation of BSC Modification P350 ‘Introduction of a seasonal Zonal Transmission Losses scheme’ on 1 April 2018, TLMs vary on a regional basis.

Spikes in TLM can display anomalies in the Settlement data and are investigated on a daily basis.


The spike in TLM values on 17th February was due to an increase in volume through an Interconnector BMU. The issue has now been resolved. 

Average Weekly Transmission Losses

This chart shows the average weekly transmission losses for the current calendar year (to date) and the previous three calendar years.

‟Week 1‟ shown on the x-axis refers to the first week of January; ‟Week 2‟ refers to the second week and so on. The chart uses data from the latest run type available, from Settlement Final (SF) onwards.

This chart shows the trend of transmission losses and enables a comparison against the last three years for identification of any patterns, increases or decreases that may require investigation.


The higher Transmission Losses seen from week 30 onwards in 2019 are linked to an under-accounted energy issue in GSP Group _A. Part of this has been corrected, but we believe other issues remain (please see comments under ADR graph, section 7.01 for further details). There has been 1.27% decrease in the losses for weeks 49 to 52 2020 from the last report.


Click on the X next to any of the icons to replace them with a short-cut link to the page you are currently on or search for a specific page.

List of BSC Insights

Previous Circulars

BSC training services

Market Entry

Charge Codes and Switch Regimes

Add New