Bipolar corona discharge from a floating filamentary particle between parallel plate electrodes

A small metal particle would extremely reduce the dielectric strength of insulating gas in a pressurized gas-insulated switchgear (GIS). We know that the filamentary particle shows several modes of its motion. When the particle was “standing” or in precession motion on the electrode, light emission due to corona discharge was observed from both ends of a particle. From these evidences it was concluded that both negative and positive discharges occur simultaneously from the particle. In order to clarify this bipolar discharge, a filamentary particle is held between the parallel electrodes. The peculiar characteristics of bipolar corona is the sudden jump of current at threshold voltage. Since this threshold voltage deviates in measurements, average and standard deviation are obtained. The corona onset voltage of the bipolar discharge shows almost no dependence on the distance between the particle and the electrode. Other interesting features of bipolar discharge are the hysteresis of threshold voltage and the dependency of edge shape on the corona current