Polarization and Depolarization Current Measurement of Aged HVDC XLPE Model Cable

XLPE (Cross Linking-Polyethylene) is widely used as an insulating material for HVDC (High Voltage Direct Current) transmission cables, and it is important to evaluate the aged state of XLPE due to long-term operation. The purpose of this paper is to evaluate the conduction characteristics of XLPE model cables before and after aging using PDC (Polarization and Depolarization Current) technique. The test sample is a model cable for research with an insulation thickness of 2.5 mm in which the inner semiconductor, XLPE insulation and outer semiconductor are incorporated. The model cable was aged at 35 kV / mm for the applied average electric field and the conductor temperature of 90 °C for 30 days. In order to evaluate the conduction characteristics of the test samples before and after aging, the conductivity of XLPE was measured under the conductor temperatures of 30 °C, 60 °C and 90 °C and applied average electric fields of 10 kV / mm, 15 kV / mm, 20 kV / mm and 25 kV / mm respectively. After 30 days of aging, the increasing tendency of XLPE conductivity with respect to electric field turned out to be decreased compared with that of unaged model cable sample.