A new method for testing organic materials´ resistance to partial discharges

This investigation deals with samples of unfilled cured epoxy resin, with each sample containing one naturally-formed gas-filled spherical void with a high enough AC-stress applied to produce partial discharges. Two different types of epoxy were used for these tests, and each of the voids contained one of two different gases commonly used as a high voltage insulation- air, and sulphur hexafluoride (SF6). By using different curing agents, different curing temperatures and different void gases, an attempt to find the influence of these material parameters on the pulse repetition rate of the partial discharges, and on the position of pulses relative to the phase of the applied voltage, as a function of the time under stress was made. It was demonstrated that some of the above mentioned material parameters had a distinct influence on both the pulse repetition rate and the location of pulses relative to the applied voltage curve, as a function of the time elapsed since voltage application. Of the two methods us ed for measuring pulse repetition rate, A: multi-channel pulse analysis and B: integrating bridge measurements, A has been found to be superior.