Research on the Assessment of the Insulation Status of 110 kV XLPE Cables Based on the PDC Method

To accurately assess the insulation condition of 110 kV XLPE cables, a polarization/depolarization current (PDC) testing platform was established for non-destructive testing on cable samples that had not been put into service and those that had been in service for 3 and 10 years, respectively, with three parameter types extracted: DC conductivity, id(t)t-log(t) curve characteristics, and aging factors. The results show that the DC conductivity of in-service cables increases with age but stays at the 10−17 S/m level without significant rise; the id(t)t-log(t) curve shifts upward overall with aging, and the peak amplitude of aging defects increases significantly while the peak position shifts right; the aging factor enables quantitative assessment of in-service cable aging, and unused cables are classified as “severely degraded,” attributed to deep trap interference from residual production cross-linking byproducts. The study confirms the PDC method effectively characterizes cable aging, but requires multi-parameter joint diagnosis to achieve comprehensive and precise insulation aging assessment.