Introduction: Sulphur hexafluoride (SF6) is widely used in electric power transmission equipment on account of its excellent properties both as an insulating material and as an arc-interrupting medium. It has become the only commercially available technology for circuit-breakers at transmission voltages. However, it has a high global warming potential approximately 23,000 times that of CO2, and its use raises concerns on environmental grounds.

Against this background, it is essential that the electricity supply industry should actively consider environmentally more compatible alternatives to SF6. The proposed work is intended to allow National Grid to identify and evaluate candidate alternative technologies to SF6 for further development, to drive improvements in containment of SF6 in equipment, to maintain an awareness of research and development into potential alternatives to SF6 and to collaborate where appropriate.

Objectives: The key objective of the proposed work is to enable National Grid to achieve the targets set out in its Climate change Strategy by means of the following:

• To identify environmentally acceptable alternatives to SF6 gas

• To participate in collaborative efforts to develop alternatives to SF6 gas.