Illuminations to the Interface Polarization Characteristics of Water-Tree Aged Cables Based on Polarization and Depolarization Current Method

In order to achieve effective diagnosis of insulation state of water-tree aged XLPE cables, this paper investigates the variation of conduction current of water-tree aged cables in the polarization process, and analyzes the asymmetrical interface polarization characteristics. The cable samples with different water tree aging time were taken the PDC test. According to the test results, the conduction current of aged cables extracted from the PDC test emerges a peak value, and this value gets more apparent when deterioration of water-tree aged cables are severer. Analysis shows the polarization process of water-tree aged cables is fast and the depolarization process is slow due to the nonlinear variation of relative dielectric constant and conductivity of water tree region, leading to appearance of the conduction current peak. So this paper presents K value to show the asymmetrical interface polarization characteristics of water-tree aged cables, and diagnose insulation performance of cables.