Discharges in air from point electrodes in the presence of dielectric plates-experimental results

The effect of a dielectric plate on characteristics of discharges in air from a point electrode was investigated experimentally. Experiments have been carried out with either 250/2500 mu s switching impulse, or DC voltage applied to the point electrode in the presence of a Plexiglas, (PMMA) dielectric plate. The dielectric plate was charged positively, irrespective of the polarity of the applied impulse voltage. The breakdown probability was measured for different crest voltages. The spatial distribution of the accumulated charge was measured for positive and negative impulse voltages. With DC applied voltages, the charge accumulated on the dielectric plate had the same polarity as the corona ions migrating from the point electrode. The repetition rate and charge content of Trichel pulse corona was measured for points stressed by negative DC voltage. The repetition rate and charge content were measured for positive onset streamer pulses. All measurements are discussed in the light of gas-discharge physics.>