Effect of surface charge accumulation on flashover voltage of GIS insulator in SF6 under DC and AC voltages

Attributed to the high reliability and high safety, gas insulated switchgear (GIS) is playing an important role in the power transmission system, its reliability is exerting more influence on the entire power grid. Under different operation conditions, the surface charges can accumulate on the surface of insulators of GIS, which is one of the main factors causing surface flashover. Surface charges not only enhance the local electric field intensity but also provide charges for creeping discharge, which finally leads to flashover. In order to study the effect of surface charge accumulation on flashover voltage of GIS insulator in SF6 under DC and AC voltage, this paper establishes a surface charge measurement system which is based on electrostatic capacitance probe method and a set of flashover test platform. It can be seen from the experimental results that no matter under DC or AC voltage, the more charge accumulated on the insulator surface, the more surface flashover voltage of insulator decreased, and under DC voltage the surface flashover could decreased by 23% maximum, and that under AC voltage is 10.2%.