Long-Term Voltage Withstand Characteristics of the Interface of SF6-epoxy Resin Impregnated Paper Under AC/DC Superimposed Voltage and DC Voltage

In recent years, there have been several flashover failures along the surface of the SF6-epoxy gas-solid interface of the epoxy resin impregnated paper (ERIP) bushing, resulting in huge economic losses. Therefore, it is urgent to study its surface flashover characteristics under actual working conditions. In this paper, an experimental platform for surface flashover of epoxy resin impregnated paper under actual working conditions has been built to study the surface flashover characteristics of epoxy resin under AC/DC superimposed voltage and DC voltage from the perspective of short-term and long-term voltage withstand. The results show that the flashover voltage of pure DC is 1.3 times of the AC/DC superimposed flashover voltage, and under the action of long-term voltage, the flashover voltage will decrease by 10%-20%. The threshold voltage of DC is 83% of the short-time flashover voltage, while the threshold voltage of AC/DC superimposed is 85% of its corresponding short-time flashover voltage. The analysis shows that the DC voltage aggravate the charge accumulation effect, which leads to a large decrease in the surface flashover voltage under long-term withstand voltage. The conclusions can provide a theoretical basis for the fault diagnosis of resin impregnated paper bushing casing.