National Grid’s new Wallend substation in Kent has reached a key construction milestone, with the completion of the main building structure that will house the site’s electrical equipment.
The 400kV substation, being built on the Isle of Grain, is designed to increase the resilience, flexibility and capacity of the electricity transmission network in the South East. Once operational, it will support the connection of several major energy projects, including NeuConnect, the 1.4GW high-voltage direct current interconnector linking the UK and Germany for the first time.
The completion of the building hall marks the end of an important phase in the programme, with work now set to move on to the installation and testing of the gas-insulated switchgear and associated electrical equipment before the substation is connected to the wider network.
Wallend forms part of National Grid’s wider £2.7 billion investment programme to maintain, upgrade and develop the electricity network across the South East. The project is also expected to support grid stability and system flexibility, while helping the UK meet its Clean Power 2030 ambitions.
Main construction began in 2025, with Balfour Beatty acting as principal contractor. The next phase will include the installation of Hitachi Energy’s EconiQ 420 kV SF6-free gas-insulated switchgear technology. National Grid said factory acceptance testing has already been completed, allowing installation work to begin.
The use of SF6-free switchgear is notable given wider efforts to reduce reliance on sulphur hexafluoride, a potent greenhouse gas used in electrical equipment. National Grid has previously committed to cutting SF6 emissions by 50% by 2030.
Alongside the construction update, National Grid has opened applications to its Community Grant Programme for organisations in areas directly affected by the Wallend project. Grants of up to £20,000 are available for initiatives delivering social, economic or environmental benefits.
Hannah Ward, EPC Project Manager at National Grid Electricity Transmission, noted, “The Wallend Substation represents a key investment in strengthening the UK’s electricity network and enabling cleaner, more secure power for the future. Completion of the main building structure is an important milestone in the construction programme and a clear sign of the progress being made on site.
“We are proud to be delivering this critical infrastructure while working closely with our partners and the local community to ensure it brings lasting benefits to the Isle of Grain.”
Tony Wilson, Managing Director of Balfour Beatty’s Power Transmission & Distribution business, added, “Completion of the main building structure at the new 400kV Wallend Substation marks an important milestone in this nationally significant project.
“Working in close partnership with National Grid, we are proud to be strengthening the electricity network and enabling the delivery of cleaner, more secure energy. We now turn our focus to the next phase of the programme, installing the critical equipment that will connect the substation to the wider network and support the UK’s long-term energy needs.”
