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National Grid Electricity Transmission has revealed plans to install an SF6-free 400kV substation in Lambeth as part of the London Power Tunnels project.
Sulphur hexafluoride (SF6) is used to insulate substation equipment but is the most powerful greenhouse gas known to humanity, with a global warming potential 23,500 times greater than carbon dioxide.
The first phase of National Grid’s London Power Tunnels project, costing £1 billion, saw 32km of underground tunnels constructed east to west from Hackney to Willesden and north to south from Kensal Green to Wimbledon to house ten new high-voltage transmission circuits.
Engineers installed 192km of 400kV cable and 30km of 132kV cable in the 3-metre-wide tunnels, which were dug at depths of between 20 and 60 metres to pass under tube lines, canals and rivers. The first phase began in 2011 and was completed in 2018, increasing transmission capacity in the capital by 20%.
Another 32.5km of tunnels are now being constructed east to west from Wimblesdon to Crayford for the second phase of the project, which will likewise cost £1 billion. Work began in 2020 and is due to be completed in 2027.
As part of this phase, National Grid is installing an access shaft, substation and headhouse at UK Power Network’s existing substation site at Bengeworth Road in Lambeth to connect the new transmission lines to the local distribution network.
National Grid has contracted Linxon to build the substation, which will be the first in the UK to use Hitachi Energy’s new SF6-free EconiQ 400kV gas-insulated switchgear and lines. Installation is expected to begin in 2023, subject to approval by Lambeth Council.
London Power Tunnels project director Onur Aydemir said: “We’re delighted that Bengeworth Road substation, at the heart of London Power Tunnels, will be SF6-free. This key power project will deliver a secure energy supply to the capital, and by using sustainable technology we are minimising the environmental impact of our operations and using transformational engineering to support the transition to net zero.”
National Grid is aiming to completely eliminate SF6 from all of its substations by 2050. The company has previously worked on a pilot project with Hitachi Energy to replace SF6 in existing busbars at its Richborough substation in Kent with the alternative fluoronitrile-based gas mixture on which the EconiQ range is based.
Scottish and Southern Electricity Networks (SSEN) is currently installing SF6-free switchgear at its new 400kV Kintore substation in Aberdeenshire. The switchgear was developed by GE Renewable Energy, which also provided SF6-free busbars for the New Deer substation in Aberdeenshire energised by SSEN in May last year.
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