A comparison between PSA plots of partial discharges in needle voids and electrical trees

The aim of this study was to investigate the difference in the pulse sequence analysis (PSA) plots of partial discharge (PD) data obtained from electrode-bound voids and electrical trees in epoxy resin samples. Electrical discharge tests were performed on a set of epoxy resin samples containing needle voids, which were obtained by a partial extraction of tungsten needle electrode. Two epoxy resin systems were used in this study, Araldite CY1301 and Araldite CY1311. The two resins have different dielectric properties, which allowed the effect of material conductivity on the discharge activity in the void to be investigated. Complementary electrical tree growth experiments were performed on a set of samples with a conventional needle-plane electrode configuration. The effects of the material properties, temperature and moisture absorbed in the dielectric samples were also investigated. The results show that additional material characterization is needed to supplement the PSA plots in order to achieve a reliable diagnostic tool.