Effect of the Surface Charge on the Flashover Voltage for GIS Basin Insulator under Switching Impulse

According to the comparative advantages of smaller volume, smaller flooring space, better dielectric performance and so on, Gas Insulated Switchgear (GIS) has been widely used in transformer substations. The basin insulators of GIS will withstand the switching impulse voltage as a result of complex operating conditions. The basin insulators play a critical role in determining the insulating strength of GIS, while the surface charge accumulation on that, which could not only distort the electric field but even lead the surface flashover, is the key factor for insulating properties. In order to study the effect of surface charge accumulation on the flashover voltage of GIS basin insulators in SF6 under switching impulse voltage, this paper established a surface charge measurement system based on the electrostatic capacitance probe method and a set of flashover test platform including an effective experimental model. The experimental results indicate that, the accumulated charges on the surface of basin insulators have a remarkable impact on the surface flashover voltage of that. The more the charge accumulated on the insulator surface, the more the surface flashover voltage of insulator decreased, and the maximum amount of flashover voltage to decrease can reach 13.6%. It should be paid more attention that the accumulated surface charge indeed has influence on the surface flashover of insulators, which could do a harm to the insulating strength of GIS to some extent.