The UK’s National Grid has reached a milestone in its programme to eliminate sulphur hexafluoride (SF6) from its network with the arrival of the first of two 178 tonne supergrid transformers and Hitachi Econiq SF6-free switchgear, at a new electricity substation being built in the UK capital.
National Grid’s construction partner in the 400kV Bengeworth Road substation is Linxon. The project is a part of the £1 billion London Power Tunnels 2 project.
The company regards Bengeworth Road as a “key milestone”, as it is said to be the first UK substation where SF6 has been eliminated from new.
This piece of power infrastructure is located at the heart of National Grid’s 32.5 km London Power Tunnels 2 route between Wimbledon and Crayford.
It will provide a 132kV connection for local grid operator UK Power Networks to distribute electricity on to homes and businesses in the area.
A second transformer is planned to arrive at Bengeworth Road imminently (1 or 2 February).
Two further transformers are planned for delivery to National Grid’s New Cross substation – also part of the London Power Tunnels 2 project – during the month and in the spring.
SF6, the most pernicious of all greenhouse gases, is synthetic, virtually indestructible and commonly used in high-voltage electrical equipment worldwide owing to its chemical stability and superior insulating/anti-arcing properties.
National Grid says the installation of SF6-free EconiQ equipment at Bengeworth Road represents a “crucial step” towards the company’s drive to eliminate the gas from its infrastructure by 2050.
The interim global target is 50% by 2030 from a 2019 baseline. The company says it has slashed its SF6 emissions by more than 80% since 2000.
What the company has done is declare all-out war on SF6, although the approach is best described as progressive.
In its latest strategic plan, National Grid says: “We decided not to follow accelerated removal of SF6 from our network as this would prevent us being able to expand the grid to help decarbonise the economy.
“This is essentially a sequencing choice as we remain committed to 2050 targets. We will increase our use of other fluorinated gases (F gases), that have excellent electrical insulation capabilities, but substantially lower global warming potential than SF6.”
Under EU rules, the use of SF6 by the power industry is being progressively eliminated. It is, however, unclear whether the post-Brexit UK will fall into line.
SF6-free technology has been trialled on National Grid’s transmission network before, notably at the 400kV Richborough substation in Kent where engineers successfully removed it from an existing gas-insulated busbar and replaced it with a greener alternative.
The recently commissioned 400kV Littlebrook substation in Kent is also partially SF6-free, utilising GE Vernova’s g3 gas-insulated busbar equipment.
It, alone, is claimed to enable the company to rid 5.6 tonnes of from its network.
Retrofilling
Since 2023, an SF6 leak-sealing solution has been rolled out and is said to have saved 7,500 tonnes of CO2 equivalent leaking into the atmosphere since deployment.
Substations and their technologies play a vital role in helping to ensure safe and reliable electricity supply, with transformers and switchgear changing voltage levels up or down and switching electricity flows to ensure power can be transmitted and distributed safely around the country.
They are ubiquitous and come in all shapes and sizes.
Meanwhile, National Grid and the University of Manchester are approaching the half-way stage with their four-year collaboration to develop a full-scale demonstrator at the Deeside Centre for Innovation, North Wales, designed to test at scale how the UK can retrofill SF6 across its network of high-voltage equipment.
The £1.9 million project is all about whether a retrofill solution can replace SF6 with an environmentally responsible alternative without having to replace or otherwise modify the existing equipment.
In a separate pilot project, in 2022 National Grid and Hitachi Energy worked up the Richborough project noted above.
The Deeside Centre is said to be the first of its kind in Europe, where electricity network assets can be tested under real-life conditions – 24 hours a day, seven days a week.
The facility provides a controlled test and demonstration environment to collect data, including a high-voltage substation and overhead line test area simulating real network conditions.
Finally, in its latest business plan the company has mooted the rebuild of Sizewell substation with an SF6-free solution to support the connection of the proposed Sizewell C nuclear power station, improve the reliability and resilience of the network and reduce greenhouse gas emissions.
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