Multipulse lightning currents and metal-oxide arresters

Multiple stroke lightning ground flashes can impose surges of exceptional severity on exposed distribution surge arresters. This paper describes a series of tests on metal-oxide (MO) arresters and varistors to study surface flashover mechanisms. The results show that the more likely causes of surface flashover were plasma generation, manufacturing defects of the varistor surface coating, dielectric properties of the surface coating and the electrode contact system. For multipulses, plasma enhancement and varistor surface coating were found to play a dominant role in surface flashover.