National Grid secures approval for three 400kV substations

In Brief

National Grid has secured planning permission for three new 400kV substations across South Yorkshire and the East Midlands.

The substations will enable existing transmission routes between Brinsworth, Chesterfield and High Marnham to be up-rated from 275kV to 400kV.

National Grid says the two reinforcement projects will provide an additional 3GW of capability across the B8 transmission boundary.

Ofgem says consumers could face up to £222 million in constraint costs if the wider EDEU reinforcement is not delivered by its intended date in 2029.

In Review

National Grid has secured planning permission for all three substations required to progress a major transmission reinforcement between South Yorkshire and the East Midlands.

The projects are intended to extract substantially more capability from an existing transmission corridor. The overhead lines were originally consented in the 1960s to operate at 400kV but have so far operated at 275kV, meaning National Grid can uprate the route without seeking fresh planning permission for the lines themselves.

National Grid's March 2026 strategic analysis says the Brinsworth–Chesterfield and Chesterfield–High Marnham projects will together provide an additional 3 GW of capability across the B8 transmission boundary, which is used to transfer electricity between northern England and the Midlands.

The reinforcement forms part of a wider expansion of National Grid's transmission system. In June, the network operator submitted proposals to Ofgem that could unlock around £4.5 billion of investment across 25 transmission projects. The new Chesterfield and High Marnham infrastructure is also intended to interface with further planned 400kV routes as that network build-out progresses.

That’s not the only benefit of the upgrade, however. Delivering it on time could also help reduce the cost of managing congestion on the transmission network. In February, Ofgem approved National Grid’s full Early Construction Funding request for the project, known as EDEU under the Accelerated Strategic Transmission Investment programme.

NESO calculated that consumers could face up to £222 million in constraint costs if the project is not delivered on schedule. Ofgem also allowed the funding to exceed the normal 20% Early Construction Funding cap, citing the project's wider system impact and the potential savings from timely delivery. Its current ASTI delivery date is December 31, 2029.

The planning approvals do not remove every remaining consent requirement. National Grid says work to connect the existing overhead lines into the new substations will still require consent under Section 37 of the Electricity Act 1989.

James Leeming, National Grid Project Director, commented, “We are pleased the substations have secured planning approval. This is an important milestone for energy resilience across England and reflects the detailed work that has gone into developing the proposals.”