François Biquez

SF 6 alternative development for high voltage switchgears

The modern transmission and distribution network relies on SF6 technology because of its remarkable arc quenching properties and dielectric insulation (approximately 3 times greater than air). However, even if SF6 Switchgears are safe for the environment, the SF6 insulating gas has potential significant environmental impacts if it leaks into the atmosphere. Indeed SF6 is one of the six gases listed in the Kyoto Protocol, with a global warming potential that is 23500 times greater than CO2. Alternative solutions to SF6 have been researched for a long time. Up to now, no significant success has been achieved in solutions for the transmission network. This paper presents the research conducted with fluorinated compounds to qualify a new gas to be used into high voltage equipment as SF6 alternatives with properties significantly improved with respect to typical SF6/N2 mixtures or others already in use. Potential applications of SF6-free gas mixture, called g3 and based on 3M™ NovecTM 4710 Dielectric Fluid for dielectric insulation and arc switching into high voltage apparatuses are reported with the aim to be low in toxicity and to reduce the global warming potential of the new mixture to typically less than 2% of the SF6 equivalent with no or minor design modification by respect to typical SF6 design. Research in progress on arc interrupting capability of this new gas mixture has shown promising results that are not described in this publication. We expect this new gas mixture to allow a major move towards a new generation of environmentally friendly switchgears.