IN Brief:
- National Grid has completed the main building hall at the new 400kV Wallend substation on the Isle of Grain.
- The hall will house Hitachi Energy’s EconiQ 420kV SF6-free gas-insulated switchgear ahead of installation and testing.
- Once energised, Wallend will support the 1.4GW NeuConnect interconnector and form part of National Grid’s wider South East reinforcement programme.
National Grid has reached a key construction milestone at its new Wallend substation in Kent with completion of the main building structure that will house the site’s gas-insulated switchgear. The 400kV substation is being built within the industrial area of the Isle of Grain and is intended to strengthen the resilience, flexibility, and capacity of the transmission network in the South East.
The completed hall will contain Hitachi Energy’s EconiQ 420kV gas-insulated switchgear, a sulphur hexafluoride-free design that National Grid says aligns with its target of cutting SF6 emissions by 50% by 2030. Main construction began in 2025, with Balfour Beatty acting as principal contractor on the design-and-build package. The latest phase covers foundations, steelwork, and external cladding, with factory acceptance testing for the GIS already completed and installation work now able to proceed.
The cladding provides the weather protection and insulation needed before electrical systems are installed, and it is also intended to help reduce operational noise once the substation is energised. From here, the project moves into GIS installation, testing, and final connection works.
Wallend is being delivered to support NeuConnect, the planned 1.4GW high-voltage direct current interconnector between the UK and Germany. Once operational, the new substation will sit alongside existing strategic assets including Grain LNG and the BritNed interconnector, further concentrating transmission infrastructure on the Isle of Grain. National Grid has said the project forms part of a broader £2.7 billion investment programme to maintain, upgrade, and expand the electricity network in the South East.
The project also includes a local community grant programme for areas affected by construction, with details available here. More general project information is available on the Wallend project page.
