Partial discharge properties in spherical void in epoxy resins

Partial discharge properties of spherical voids artificially made in unfilled epoxy resin are described. In deterring the partial discharge (PD) inception voltage, it was found that at much higher voltage than the calculated inception voltage, discharges didn´t occur immediately but initiated after long time lags. The inception time-lag is discussed. Though the inception voltage can not be determined because of its randomness, the extinction voltage is fairly stable and repeatable. This value is found to be almost equal to one-half of the inception voltage obtained from theoretical equation. Hence, it is offered that in order to evaluate damaging discharges the extinction voltage should be used.