MDD changes initiated by Ofgem Review


Large scale changes to Market Domain Data (MDD) based on Ofgem’s Targeted Charging Review (TCR).

This page contains details about the planned increase of MDD sets in response to Ofgem’s TCR and how this will impact BSC Parties. You can also find out information about why these changes are happening, what has already happened and what the next steps are.

Latest update

12 April 2021
As part of our continuing work to progress large scale change to Market Domain Data (MDD) sets for Ofgem’s Targeted Charging Review (TCR), we provided an update to the Supplier Volume Allocation Group (SVG) on 6 April 2021 on the outcomes of industry and BSC Central System testing.

It was anticipated that the unprecedented growth in the size of the MDD and Line Loss Factor (LLF) datasets needed for Ofgem’s Targeted Charging Review could present challenges for Elexon’s Central Systems and Parties’ systems, therefore we have been carrying out testing to identify and mitigate any potential risk to industry processes relating to balancing and settlement.  

The industry testing that took place in February provided Elexon with the assurance that our Parties’ systems can cope with the expected increased volume of data in the LLF and MDD data files.

We also completed testing of the BSC Central Systems, which was carried out in order to verify how they would operate with the additional LLF and MDD data. We are now progressing the recommended system improvements to ensure that the Central Systems can handle the expected data increase volumes. These changes will be tested and implemented before we progress any further Change Requests relating to the Targeted Charging Review. We expect the improvements to take around 17 weeks to complete, at which time we will progress the remaining Change Requests, which relate to Independent Distribution Network Operators (IDNOs).

How it relates to you

Ofgem’s TCR means major changes to how network charges are set. It will see the numbers of LLFCs in MDD increasing on a large scale, as well as the number of valid set combinations.

BSC Parties who load MDD and LLF files may be impacted, as they will have to load significantly larger numbers of new LLFCs and valid set combinations.

Such a large increase in data could impact your network systems. If you notice any such impact, please contact the MDD Coordinator or LLF Coordinator.

What’s already happened

Industry Testing

Test plans will incorporate testing for Participants, the BSC Central Systems, and subsequent Settlement processes as they will be using the increased volumes of LLFCs. We will provide you with a further update on the test plan as soon as we can.

We will make sure that the participants are kept informed with regards to testing and are provided with sufficient notice prior to TCR submission dates.

Reasons for testing

As this is a major change to MDD data, Elexon has been leading work to carry out central system testing and participant testing. Overall we will need to provide assurances to the SVG, the BSC Panel and BSC Parties that adding such a large amount of new data will not pose risks to Settlement.

Software development

Automatically loading MDD

Software is being developed that will automatically load MDD, as this is currently a manual process. This should reduce the risks around the publication and data quality of MDD for participants.

Publishing data

  • 13 January 2021: MDD data set was published. The data set includes the TCR changes for the remaining Host Distributed Network Operators DNOs and includes 13 out of 14 Grid Supply Point (GSP) Groups. This went live on 20 January 2021.

  • 9 December 2020: MDD data set was published, but the set did not contain any TCR changes. This went live on 16 December 2020.
  • 11 November 2020: 1,638 new LLFCs and 37,000 new valid set combinations added to MDD. This went live on 18 November 2020. 
  • 14 October 2020: 2,122 new LLFCs and 24,287 new valid set combinations added to MDD. This went live on 21 October 2020.

This new published data impacts D0269/D0270 (MDD) and D0265 (LLFC) flows.

Previous news

Why these changes are happening

Ofgem’s TCR addressed concerns that the current framework for residual network charges could lead to inefficient use of the network. This means there will be major changes to how network charges are set.

This will result in the numbers of LLFCs in MDD increasing from 16,000 to approximately 35,000. The number of valid set combinations will also increase from around 208,000 to approximately 470,000.

The distribution charge aspects of Ofgem’s reforms will be introduced from April 2022.


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