Value chain · CLM-0786
In plain terms
In December 2025 the UK system operator changed its own connection standard to allow a single large direct-current converter to carry more power, because the old 1320 megawatt cap was forcing offshore wind farms to build extra cables, and it priced the extra frequency support at about 12 million pounds a year.
The claim as recorded
The GB SQSS modification GSR034, final report 16 December 2025, relaxed the offshore DC converter loss-of-infeed clauses 7.7.2.1 and 7.12.2.1 from the Normal to the Infrequent Infeed Loss Risk on the reasoning that the 1320 MW cap "could result in additional and potentially sub-optimal investment" and an increase in the numbers of cables and landing points, assessed the resulting extra frequency response cost as capped at approximately GBP 12 million per annum at a price of GBP 3.7 per MWh, and stated that current HVDC monopole technology availability is limited to 1500 MW; version 2.12 of the SQSS, dated 29 May 2026, carries the changed clauses.
Scope and limits
This is an offshore DC converter modification. It does NOT change the onshore clause 2.6.3 that constrains a rectenna (CLM-0780), and it may not be cited as evidence that an onshore 2 GW single-point connection is now permitted. Its value here is as a documented precedent for how a loss-of-infeed constraint is relaxed in GB, and for the 1500 MW HVDC monopole figure.
What it assumes
That the GBP 12 million per annum and GBP 3.7 per MWh figures are in the money of the report's own year, 2025, which the report does not state explicitly.
Where it comes from
Issue, verbatim: "...(SQSS) restricts the loss of infeed risk for any single offshore DC converter, to the normal loss of infeed risk (1320 MW). This restriction, which aims to limit the consumers' exposure to events where frequency drops below 49.5 Hz, could result in additional and potentially sub-optimal investment being required to meet such criteria. It could also result in an unintended detrimental impact on the environment due to the increase in the numbers of cables and landing points..." Clauses named, verbatim: "Clauses 7.7.2.1 and 7.12.2.1 of the NETS SQSS restrict the loss of power infeed risk associated with a secured event on a single DC converter to the normal loss of infeed risk (1320MW)." Technology ceiling, verbatim: "(Note this is a conservative assessment considering the current technology availability of High Voltage Direct Current (HVDC) monopole systems is limited to 1500MW)." Cost, verbatim: "This cost, based on the analysis presented in Workgroup discussions, is capped at approximately GBP 12m/annum based on a GBP 3.7/MWh price for the relevant frequency response service" (the source prints the pound sign; transcribed here as GBP). In-force text, verbatim from SRC-238 clause 7.7.2.1: "following a planned outage or a fault outage of a single DC converter on the offshore platform, the loss of power infeed shall not exceed the infrequent infeed loss risk;".
Basis: GB SQSS modification process; frequency response cost at a stated GBP 3.7/MWh price, currency and year as printed in the source
Related records
- Answers question
- QST-012 not published in this release
Cite this
energyaperture.com/c/clm-0786
CLM-0786, Energy Aperture, as of 2025-12-16.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-238
- CLM-0780The UK rules for connecting power stations set a hard limit on how much generation one fault may disconnect at once: 1800 MW for a fault on...CLM-0782UK rules limit the overhead line between a generating unit and the grid to 5 km for units producing at least 2000 gigawatt-hours a year and...CLM-1211Britain's main transmission grid runs at 400 kV and 275 kV, and parts of the 132 kV network in Scotland. On the 400 kV network the voltage...CLM-1487In Britain, the amount of fast back-up power kept ready depends mainly on the biggest single block of power that could be lost at once; the...