SF6 is non-flammable and takes up less volume than oil alternatives, but it is also a greenhouse gas with a much higher global warming potential than CO2 and, if leaked, remains in the atmosphere for several thousand years. According to GE, which worked with National Grid on the project, there has been no viable alternative to SF6 as an insulation medium in high voltage switchgear since the 1970s.
Working with 3M and GE Grid Solutions, National Grid has commissioned an alternative at its Sellindge 400,000 V substation in southeast England. The project uses a ‘green gas’ solution instead of SF6 and National Grid said it reduces the equipment’s global warming potential by 98 per cent.
The substitution is expected to save over 11,000 tonnes of CO2 equivalent during the service life of the 300-metre gas-insulated circuits which connect the Sellindge substation to the bushings and overhead lines.
The project was commissioned in April under National Grid’s drive to reduce greenhouse gas emissions across its UK and US businesses by 45 per cent by 2020.