Spacer Flashover in SF6 under Steep-fronted Impulse Voltages

Very fast transient overvoltages (VFTO) might result from flashover of the particle-contaminated spacer in gas-insulated switchgear (GIS). To get a better understanding of the effects of voltage wavefront steepness and oscillation frequency on the flashover voltage, experiments were carried out on a simple cylindrical spacer with a metallic protrusion under different voltage waveforms. The results show that the flashover voltage-time (V-t) characteristics are dependent on oscillation frequency and rise time of impulses. The space charge accumulation produced by corona discharge of the metallic particle on the spacer is the main reason that causes the insulation failure of GIS.