Study on charge dynamics in water-tree XLPE insulation for deterioration diagnosis

Water tree is one of the most significant mode of degradation of XLPE insulation cables which leads to the failure. We have successfully proposed pulse method to detect and locate water tree degradation by applying bias (poling) and probing pulse voltage. Based on the proposed method, the degraded water-tree XLPE cable was detected. We studied on the mechanism of residual charge related to water tree degradation by using the XLPE film sample contained water tree. The decay process of charge under application of pulse voltage was explained by Pool-Frenkel emission process. The result of the numerical simulation was demonstrated. Assuming trapping and de-trapping process, the differences in pulse response was explained depending on the degree of water tree degradation.