Moving to SF6-free technology with g3 gas, a new era for GIS
Our ancestor, Delle-Alsthom, pioneered one of the very first SF6 GIS in 1966. Because of its outstanding dielectric and physical properties, this SF6 gas has become the norm over the last 50 years. However, SF6 was identified as a very potent greenhouse gas, being 23,500 more potent than CO2 and lasting over 3,200 years if released in the atmosphere. Due to its potential environmental impact, SF6 was listed has been listed on the Kyoto protocol since 1997. At that time, there wasn’t any alternative to SF6 they concluded. In 2008 GE’s Grid Solutions R&D experts in Villeurbanne, France, started working on an alternative in collaboration with 3MTM. In 2014, at the Cigré technical conference in Paris, France, they announced g3 (pronounced g-cubed), a game changing gas mixture based on 3M™ Novec™ 4710 Dielectric Fluid from the fluoronitrile family developed by 3MTM and used as an additive to carbon dioxide and oxygen. Time has come for the experts in Villeurbanne, Aix-les-Bains in France, Oberentfelden in Switzerland, and in Charleroi, PA, to develop the associated products. The first SF6-free products based on g3 where the gas-insulated lines and busbars are passive components of the GIS. g3 was used here as the insulating medium. “The first 420 kV g3 GIL installation was at National Grid’s Sellindge substation in the UK in April 2017,” explains Bertrand Portal, g3 Product Manager at GE’s Grid Solutions. “The g3-gas insulated line has been in successful operation since then”. In parallel the experts were working on the development of the first 145 kV g3 GIS. This new g3-GIS was introduced during Cigré in Paris in 2016 and subsequently energized in Switzerland at Axpo’s Etzel substation in 2018. Since then, more than 100 bays have been installed in Europe and the g3 experts continue to develop new solutions utilizing this alternative insulation and switching gas. In particular, development efforts are focused on a 420 kV g3 gas-insulated substation and consequently the development of a 420 kV interrupter using g3 for arc quenching. Named as the LifeGRID project, this current development effort is being co-funding by the EU Commission’s LIFE Programme. The LIFE Programme is the EU’s funding instrument for the environment and climate action. In parallel with the circuit breaker development, they will finalize the 420 kV g3 GIS. This will be a major milestone to build an SF6-free European grid.
Last, but not least, on April 21st, 2021 GE’s Grid Solutions announced a non-exclusive, cross-licensing agreement with Hitachi ABB Power Grids Ltd., granting them use of the g3 technology to develop a part of their high voltage SF6-free switchgear portfolio.
“The future of GIS is GE’s g3 fluoronitrile based gas mixture,” concludes Portal.”