ESO saves £80m with early start to constraint management scheme

National Grid Electricity System Operator (ESO) says it has saved £80 million by allowing renewable generators to begin providing a new constraint management service ahead of schedule.

The Constraint Management Pathfinder will give more flexibility to the ESO’s control room by enabling renewable generators to continue operating, rather than being pre-emptively curtailed to avoid overloading the transmission network in the event of a fault.

The scheme is due go fully live in October 2023 but the ESO has allowed six units, most of them wind farms with battery storage systems, to begin providing the service early to manage constraints across the B6 boundary between the transmission networks in England and Scotland.

When the control room identifies a constraint, the participating units are armed to be ready to reduce their output in the event of a fault. If a fault occurs, the units are tripped off within 150 milliseconds using the transmission owners’ circuit breakers. The ESO will then reconnect the units once the fault has been safely resolved.

Participating generators receive a payment for each settlement period in which the service is armed, as well as a tripping fee whenever they are disconnected following a fault. However, the ESO said the service will save money for consumers by reducing constraint payments that would otherwise need to be made to generators in exchange for curtailing their output.

By commencing the service early, the ESO said it has already saved £80 million between April 2022 and January 2023. The first contracts for regular operation of the service will run from October 2023 to September 2024. Further contracts have also been awarded for the following year.

Julian Leslie, head of networks at the ESO, said: “The Constraint Management Pathfinder is fundamental towards solving a heavily constrained area of the grid, and we have taken the initiative to drive forward innovative solutions to manage constraints on the system, whilst maximising renewable generation to ensure 100% zero-carbon operation.

“This builds on our wide-ranging five-point plan which will demonstrate how we resolve constraints on the network for years to come, and reduce balancing costs, ultimately saving consumers millions of pounds.”