Influence of impulse voltage waveshape on the flashover of clean and particle-contaminated spacers in SF6 gas-insulated system

The influence of the impulse-voltage waveform on the flashover voltage of an epoxy resin disk spacer in a SF₆-gas-insulated system was studied. The results refer to voltage waveforms for which the two limiting cases are standard lightning impulse and standard switching impulse. It is shown that there is an essential difference between the influence which the impulse waveform has on the flashover voltage of clean and particle-contaminated insulators, respectively. For clean spacers the standard lightning impulse flashover voltage is the highest, while for particle-contaminated spacers it is the lowest. The reduction of the spacer flashover voltage caused by an increase in the particle length is different for impulse voltages of different waveform. For example, for a 14 mm-long particle, the standard lightning impulse flashover voltage is reduced by 70%, while the standard switching flashover voltage is reduced by 35%