Charge accumulation on spacers in non-uniform field SF/sub 6/ gaps under DC and lightning impulse voltages

Charge densities on cylindrical spacers placed in a rod-plane gap geometry were measured using a capacitive probe in an SF/sub 6/ environment. Corona discharge occurring at the tip of the rod electrode was found to be a main source of charge accumulation for DC and lightning impulse voltages. Microdischarges occurring at asperities, or other locations with high electric fields, on the plane electrode can explain the nature of spacer charge accumulation under positive polarity voltage application. For DC voltages lower than the corona inception, the charge accumulation can be explained by the drift of charge carriers present in the gas; this mechanism is not effective under impulse voltages.<>