Insulation condition assessment of XLPE cables based on polarization and depolarization current method

The degradation of cable insulation poses a potential risk to the safe operation of power systems. Non-destructive and effective detection techniques are therefore essential. The Polarization and Depolarization Current (PDC) method, as a time-domain dielectric response technique, can reflect deep polarization processes in insulation materials and shows high sensitivity to the aging condition of cross-linked polyethylene (XLPE) cables. In this paper, a systematic study was carried out using both laboratory-aged XLPE samples under various thermal aging states and in-service cables from field sites, including those affected by moisture. The analysis focuses on the depolarization current curves and their characteristic changes at different aging stages. The results show that as the aging level increases, the depolarization current becomes larger and decays more slowly, with some curves exhibiting a distinct “hump-shaped” feature. Moreover, localized defects such as moisture ingress at joints were also effectively detected by the PDC method, demonstrating its potential for real-world applications. The findings confirm the effectiveness and applicability of the PDC technique for insulation condition assessment.