NESO will use day-ahead restrictions more regularly on four electricity interconnectors, as it tightens its management of power flows into and out of Great Britain.
The change applies to North Sea Link, Viking Link, NEMO Link and ElecLink, NESO said restrictions may be needed where intraday options do not provide enough certainty to protect system security.
Interconnectors allow electricity to be traded between Great Britain and neighbouring markets, helping balance supply and demand while giving consumers access to lower-cost power when it is available.
However, NESO can limit the capacity offered to the market through Net Transfer Capacity restrictions if planned imports or exports could create operational risks.
The system operator said restrictions will be calculated using day-ahead forecasts and its expected picture of conditions across the British electricity system. Any capacity that is no longer needed for security purposes can be released back to the market during intraday trading if conditions change.
NESO said restrictions will be spread equitably across the interconnectors capable of addressing the identified risk, based on the capacity each one declares two days ahead.
Further controls become available closer to real time on IFA, IFA2 and BritNed. NESO will then recalculate the restricted volume across all available links to ensure the intervention remains fairly distributed.
The move could reduce electricity imports during periods of system stress, potentially increasing reliance on domestic generators and affecting wholesale prices.
It comes as NESO faces scrutiny over its management of the grid during the extreme heat in June, although the system operator has not said the new approach is directly linked to that event.
Ofgem has commissioned a post-event review into incidents of system stress during the week beginning 22 June. A separate external investigation is examining whistleblowing allegations concerning operational decision making and record keeping.
NESO said all day-ahead restrictions will be published through its data portal. Compensation will be paid under existing commercial arrangements governing interconnector capacity restrictions.
June balancing costs reached £302 million, up £64 million from May, as higher temperatures and increased wind curtailment raised the cost of operating the system.
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