An Investigation on Surface Flashover Characteristics of FRP in Several Insulation Gases for the Spacer of Cryogenic Bushing

Abstract

Superconducting equipment has been actively investigated for securing the environment and energy technology (ET) in various parts of the world. Despite these movements, a high voltage cryogenic bushing, which plays an important role of interconnection between the electric power systems and superconducting devices, has not been fully developed due to severe insulation requirements. A gas insulated cryogenic bushing has been investigated as one of our projects since 2010. As a basic step to obtain the design parameters for cryogenic bushing, we focused on the surface flashover characteristics of glass fiber reinforced plastic (FRP) in several insulation gases. For the surface flashover tests, several insulation gases including SF6, $CF_4$ and N₂ gas were prepared. Various length of FRP specimens were fabricated in order to obtain the fundamental data for creepage distance of FRP. The first specimen group was from 2 mm to 10 mm with 2 mm intervals and the second specimen group was from 20 mm to 100 mm with 20 mm intervals. And the gas pressure was varied from 1 bar to 4 bar. An AC overvoltage test and a lightning impulse test were performed. Then the experimental results of surface flashover were obtained and analyzed. Based on these results, it would be possible to design the optimum creepage distance of FRP in a cryogenic bushing.