Effect of surface charge on flashover voltage for Cross-linked Polystyrene (XPS) insulator under nanosecond pulse voltage in vacuum

The surface flashover voltage of the insulator in vacuum is much lower than that of both insulators and the vacuum gap in the same dimension. The critical factor that effects surface flashover voltage is the accumulation of surface charge which can severely restrict the performance of the vacuum devices. Owing to the excellent electrical properties and mechanical properties, Cross-linked Polystyrene (XPS) is applied more and more widely as insulator material in military and aerospace industry. In order to study the characteristics of surface charge and its effect on surface flashover voltage on the XPS insulator under nanosecond pulse voltage in vacuum, a set of insulator surface charge measurement system and surface flashover voltage test platform under nanosecond pulse in vacuum have been set up in this paper. This paper adopts the electrostatic capacitance probe method to acquire the distribution of surface charge on XPS insulator, studies the effect of amplitude and pulse number of voltage on the characteristics of surface charge accumulation, and analyzes the effect of surface charge on surface flashover voltage under nanosecond pulse voltage in vacuum. The experimental results indicate that, with the increase of voltage amplitude and pulse number, there is an obvious increase on the amount of surface charge accumulation. The accumulated charges on the surface have marked effect on surface flashover voltage, and the maximum amount of flashover voltage to decrease is 15.5%. Under the same conditions, the amount of surface charge accumulation of XPS insulator is much less than that of ceramic insulator.