Partial discharge performances under non- uniform electric field in gas mixtures with small fluorocarbons

This paper describes the partial discharge (PD) performances of gas mixtures with small fluorocarbons because their global warming potential (GWP) is smaller than that of SF₆ gas, which was regulated as one of six restricted gases. It is difficult to apply pure fluorocarbon gases as insulating medium directly in gas insulated switchgear (GIS) and gas circuit breakers (GCB), because their liquefying temperature is high. Thus, the mixtures have various contents and ratios. The PD inception voltages of gas mixtures containing fluorocarbon and N₂ are measured and analyzed as a function of gas pressure, electrode distance and the ratio of the fluorocarbon. The PD performances of fluorocarbon gas and its mixtures are compared with those of SF₆ gas, which is now widely used as the insulating medium in GIS and GCB. The results show that gas mixtures containing special fluorocarbon have a possibility to substitute for SF₆ gas.