National Grid and GE Energy Connections will soon start energising equipment at the National Grid’s Sellindge substation, near Folkestone, that uses for the first time anywhere in the world a new kind of gas insulation. Known as ‘green gas’ or g3 the recently developed alternative to SF6 is being field trialled as an alternative to SF6 in the 420 kV gas-insulated busbar. The GIB has been constructed and tested and will be energised during April. Work on the project started two years ago and in lab testing g3 achieved a significant reduction in environmental impact. The work was partly funded by an innovation grant from the regulatory Office of Gas and Electricity Markets (OFGEM).

g3 is a newly created gas, combining 3M Novec 4710 dielectric fluid (4%) and carbon dioxide (96%) and has been developed by GE in conjunction with 3M. The g3 mixture reduces the global warming potential of the gas insulation by more than 98% compared to the SF6 that has been used in similar applications for many years.

National Grid is the first transmission system operator to implement an SF6-free high voltage gas-insulated system. The intention, if it proves successful, is to roll it out across the country in National Grid substations.

Award winning

The project was selected as a finalist in the IET Awards Sustainability category in November last year. Four other TSOs now intend to use g3 in gas-insulated lines and gas insulated substations from 2017 onwards, affirming its viability as a safe alternative to SF6.

Giuseppe Sottero, general manager, Gas Insulated Substations at Grid Solutions said, “We are very pleased to collaborate with National Grid on this project, the first in the world to use the g3 solution. Utilities wanting to take the step to reduce their greenhouse gas potential now have an alternative to SF6. g3 is an important tool in the quest to reduce the electrical industry’s impact on the environment.”