Performance of flashover on the resin spacer surface in N2/SF6 and SF6/air gas mixture under AC power frequency

With the development of the electric power and railway industry, more and more SF₆ gas-insulated equipments have been applied. However the greenhouse effect and environmental pollution that caused by SF₆ gas has been paid attention in recent years. Therefore looking for the SF₆ alternative gas without reducing its insulation performance becomes one of the research hotspots. Epoxy resin has been widely used as the preferred material of post insulator in cubicle type gas insulated switchgear (C-GIS) for its excellent dielectric performance and mechanical properties. In this paper, the power frequency surface flashover characteristics tests are done on the epoxy resin insulator which is in the SF₆-N₂ and SF₆-air gas mixtures with lower pressure range, nonuniform electric field. The test results show that the insulator's power frequency surface flashover voltage increases linearly with the increasing pressure, the proportion of SF₆ in the gas mixture influences the insulator's power frequency surface flashover voltage greatly, and adding a small amount of SF₆ to the pure N2 or the pure Air can significantly improve the insulator's power frequency surface flashover voltage. With the proportion of SF₆ in the gas mixture increasing, the insulator's power frequency surface flashover voltage increases with a saturation trend.