Partial Discharge Phenomena Due to Electrical Treeing in XLPE

Increased electrical stress due to cable joints was simulated by point-plane electrode configuration. Electrical tree formed in XLPE insulation sliced from 220 kV rated cable was diagnosed by partial discharge and dielectrometry measurements and optical observation. With increasing voltage at the rate of 1 kV/10 min, various analyses for PD pulses distribution in 20 ms and single pulses were carried out to compare the effects of applied voltage. Two types of electrical trees have been found out based on PD analysis and optical recording. Observed light emission supported the theory of emission by protons due to high-energy electrons. The analysis was supported with dielectrometry measurements on the sample before and after tree formation. And also, typical models were developed to study the mechanism of treeing