Direct measurement of space-charge injection from a needle electrode into dielectrics

Abstract

We show that space-charge injection from a needle into a dielectric can be determined with a resolution of 10−15 °C, by using guarded needle electrodes and a charge compensating bridge circuit. The technique is applied to epoxy resin samples. A well-defined homogeneous space-charge cloud formation is observed in quantitative agreement with a field-limiting space-charge concept.