A Space Charge Measurement Method of XLPE Based on Polarization and Depolarization Current

To characterize the aging degree of XLPE through the de-trapping progress of space charges, this paper presents a method to extract the de-trapping current from the Polarization and Depolarization Current (PDC) of the insulating medium and a method to calculate the trapped charge density and trap depth. After changing the polarization voltages in PDC tests and charge injection durations and the thermal aging degree of samples, trapped charge density and trap depth in samples are calculated. The results show that higher voltage in PDC tests can promote the charge escaping in deep traps; as the space charge injection duration increases, medium depth traps are more likely to accumulate charges than shallow traps and deep traps; with the aging of XLPE, thermal aging of XLPE first undergoes the recrystallization progress and then enters the thermal destruction period and the change of crystallinity leads to the number of traps in XLPE first increase and then decreases while traps gradually deepen during the whole thermal aging process.