Mechanism of prebreakdown spacer charging in non-uniform fields under unidirectional 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. The 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. Further, microdischarges occurring at asperities or other locations with high electric fields on the plane electrode may explain the nature of spacer charge accumulation under positive polarity voltage application. For DC voltages that are lower than the corona inception, the charge accumulation may be explained by the drift of charge carriers present in the gas; this mechanism is not effective under impulse voltages.<
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