Alstom signs contract with National Grid to test a more environmentally-friendly gas solution in UK

Alstom has signed a contract with National Grid to trial, as part of an innovation project, a revolutionary environmentally-friendly insulating system for the UK’s high voltage power network. The contract will see National Grid use Alstom’s g3 (green gas for grid), a gas mixture that can replace SF6 for high voltage Air Insulated (AIS) or Gas Insulated switchgear (GIS) applications, for a 300 meter gas-insulated busbar¹ in Sellindge, in Kent. The Alstom g3 being used in the 420 kV gas-insulated busbar will be able to operate to temperatures as low as -25°C, with the system due to be commissioned by mid-2016.

The Sellindge project is an integral part of National Grid’s intended network reinforcement plans and so the g3 system will be deployed in an operationally critical part of the UK’s transmission network. The Sellindge converter station joins Interconnexion France-Angleterre to the 2,000 MW HVDC interconnector which links the British and French electricity transmission systems. The converter stations on both sides of the English Channel were built by Alstom, with the link capable of supplying around three million homes.

In August 2014, Alstom became the first company in the world to offer the electrical industry a technically and economically viable alternative to SF6. Alstom’s SF6-free solution, g3, has a global warming effect 98% lower than that of SF6 gas. It is non-toxic and non-flammable, and is safe to handle with no impact or degradation on the ozone layer. With technical performances comparable to SF6, g3 is a suitable technology for the development of a new generation of cleaner high- and ultra-high voltage equipment.

National Grid has a strong commitment to managing its environmental impact and actively promotes initiatives, such as g3, to identify ways to reduce SF6 usage across its network. The company aims to reduce its emissions of greenhouse gases by 45% by 2020 and by 80% by 2050, and to continually improve its environmental management systems.

Alstom has supplied 250 bays of 420 kV GIS to National Grid over the course of a 35-year working relationship between the two companies. The g3 equipment will be engineered, manufactured and tested at Alstom Grid’s factory in France.

1 A gas-insulated busbar is essentially a concentric system of cylindrical enclosures and conductors, insulated with a pressurized gas


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