Advanced Search

CT and VT Ratio Valid Set

v 3.0

Current Transformer and Voltage Transformer Ratio Valid Set

Guidance Note

Current Transformer and Voltage Transformer Ratio Valid Set

This document covers:

    • Where to find the list of valid Current Transformer (CT) and Voltage Transformer (VT) Ratios

    • Where to find the process for adding and removing CT and/or VT Ratios

What is the CT and VT Ratio Valid Set?

It is a national valid list of transformer ratios, published on the Elexon Portal for use by Licenced Distribution System Operators (LDSOs) and Supplier Volume Allocation (SVA) Meter Operator Agents (MOAs)1. It will also introduce a process where LDSOs and SVA MOAs submit proposed changes to the list to Elexon.

Where can the CT and VT Ratio Valid Set be found?

The valid set can be found on the CT VT Valid Set page on the Elexon portal (

Where can the process for changing the CT and VT Ratio Valid Set be found?

It can be found in Balancing and Settlement Code Procedure BSCP515 ‘Licensed Distribution’ and defines the process LDSOs need to follow to amend the valid list (add or removal CT/VT ratios).

The same process must be followed by SVA MOAs to amend the valid set list. The following process steps can be followed with a more detailed version found in BSCP5152.

Amending the CT VT Valid Set process

    • Requests to amend the valid set (add or remove) must be sent to the Elexon Metering team (

    • On receipt of a request to amend the valid list, Elexon will check the submitted ratios meet the valid format before adding the CT/VT ratio to the valid list, which will be published on the Elexon Portal.

    • Where there is a request to add or remove a ratio from the valid list, Market Participants will be notified, via a Newscast article, 10 Working Days (WDs) before the valid set is amended and published.

    • If any objections are raised to the request the requester will be notified, asked for an explanation and a hold will be placed on the amendment if required.

    • Where no, or any valid objection, has been raised Elexon will add or remove the relevant ratios and publish them on the Elexon portal 10 WDs after the publication of the Newscast article.

Where a SVA MOA receives an invalid ratio they will be required to select the unknown option from the valid set list. This helps to promote better data quality as all unknown ratios will be reported under one value.

Further Information

Further information on the CT and VT Ratio valid set can be found in BSCP515 of the BSC. If you have a query about the valid set please contact the BSC Service Desk or call 0370 010 6950.

Intellectual Property Rights, Copyright and Disclaimer

The copyright and other intellectual property rights in this document are vested in Elexon or appear with the consent of the copyright owner. These materials are made available for you for the purposes of your participation in the electricity industry. If you have an interest in the electricity industry, you may view, download, copy, distribute, modify, transmit, publish, sell or create derivative works (in whatever format) from this document or in other cases use for personal academic or other non-commercial purposes. All copyright and other proprietary notices contained in the document must be retained on any copy you make.

All other rights of the copyright owner not expressly dealt with above are reserved.

No representation, warranty or guarantee is made that the information in this document is accurate or complete. While care is taken in the collection and provision of this information, Elexon Limited shall not be liable for any errors, omissions, misstatements or mistakes in any information or damages resulting from the use of this information or action taken in reliance on it.

1 Referred to as Metering Equipment Managers (MEM) under the Retail Energy Code Metering Operations Schedule.

2 Where the BSCP515 ‘Submission of the Current Transformer (CT) and/or Voltage Transformer (VT) ratios for inclusion (or removal) in the BSCCo

valid set’ process refers to LDSO this can be read as SVA MOAs for where an SVA MOA wishes to amend the valid set.