Partial Discharges in a Cylindrical Void with a Metal Rod Electrode

The distributions of the rate of partial discharge magnitudes, here called the discharge intensities, were studied in artificial voids having configurations proposed earlier for the endurance testing of materials using a multichannel analyzer, while the following parameters were varied: applied voltage, polarity, test duration, void sealing, void gap, ambient gas, rod geometry and treatment of the specimens. The intensity of partial discharges was to some extent affected by all of these factors, but the gas in the void was particularly significant. The differential rate density of discharge intensity is largely controlled by the availability of negative ions for dissocation or the presence of overstressed high field regions. Many of the parameters varied in the present study affected these features. Sporadic discharges were noted where the quantity of charge was greater than the theoretical maximum values by a factor of up to two. This was noted with all geometries. The occurrence of discharges to the wall of the void was the source of the above disparity.