Leakage current and partial discharge characteristics of epoxy resin material of distribution current transformer in salt fog pollutant condition

Outdoor Distribution Transformer is frequently used for 20 kV Medium Voltage Overhead Line. The main material for the isolator is the epoxy resin mixed with white cement (talk haichen). In outdoor use, resin epoxy material experiences isolation aging due to influences from various environment condition (pollutant and humidity). In this paper, results of partial discharge (PD) measurement testing of the epoxy resin material is presented. The ability of pollutant to absorb humidity very much affect PD maximum content. In wet condition (95% RH), the best white cement filler is 75% of the weight for 4.6 mS and 36 mS/cm conductivity, while for 24 mS/cm conductivity, the best white cement filler composition is 25% of the weight. The results of the epoxy resin material current leakage testing show that the increase in current leakage is very much affected by the environmental condition (humidity and pollutant). In wet condition (95% RH), the dry band phenomenon is seen in the surface leakage current increase fluctuation. The flash over condition frequently happens in 30 kV testing voltage for 36 mS/cm conductivity.