Breakdown Characteristics of SF6in Different State and Bubble Movements under AC High-Voltage

Abstract

In this paper the experiments of breakdown characteristics by temperature change of <TEX>$SF_6$</TEX> gas(<TEX>$GSF_6$</TEX>), and <TEX>$SF_6$</TEX> liquid (<TEX>$LSF_6$</TEX>) in model GIS (Gas Insulated Switchgear) are described. From the experiment's results, the breakdown characteristics classify the vapor stage of <TEX>$SF_6$</TEX> according to Paschen's law, in which the gas & liquid coexisted stage of voltage value increases, resulting in much deviation and the breakdown of voltage (<TEX>$V_B$</TEX>) low stage as the interior of the chamber gets filled with a mixture of <TEX>$SF_6$</TEX> that is not liquefacted and remaining air that cannot be ventilated. The ability of <TEX>$LSF_6$</TEX> insulation is higher than the high-pressurized <TEX>$SF_6$</TEX> gas. The breakdown characteristics of <TEX>$LSF_6$</TEX> were produced by bubble formed evaporation of <TEX>$LSF_6$</TEX> and bubbles caused by high electric emission. It is considered in this paper that the results are fundamental data for electric insulation design of superconductor and cryogenic equipments machinery that will be studied and developed in the future.