Proposal of Evaluation Test Method for Withstand Performance under Residual DC Charge at GIS Insulator

Abstract

In recent years, compact size gas insulated switchgear (GIS) has been developed from rationalization of specifications. All of the GISs have been checked to pass the AC and lightning impulse (LI) withstand test, however, DC stress that occurs on the AC GIS spacer when switching devices are operated has not investigated enough. Since electrical field strength for inside of GIS tank is more strengthen for compact size GIS than ever, it is more necessary to evaluate the withstand performance for GIS spacer under residual DC voltage. Under the DC stress, the electrification of charges strengthen the electrical field strength at creepage surface (E_t) and withstand performance for GIS spacer depends on the maximum value of E_t (E_tmax). When volume resistivities at surface layer of spacer are uneven, E_t strengthen at the uneven spot. In this paper, E_tmax under DC stress with uneven volume resistivities at surface layer of spacer is investigated, moreover, the evaluation test method for withstand performance under residual DC charge are constructed and proposed.