Research on Insulation State Evaluation of Water Tree Aging XLPE Cable Based on PDC Multi feature Weight

Research on the preparation and insulation state evaluation of XLPE(Cross-Linked Polyethylene) water tree aged cables was conducted using $64 / 110 \mathrm{kV}$ cable samples subjected to needle punching and salt injection treatment followed by highfrequency high-voltage accelerated aging. Time-frequency domain features of polarization/depolarization current were extracted based on the PDC (Polarization and Depolarization Current) method, including DC(Direct Current Conductivity) conductivity, unit depolarization charge, and Fourier transform dielectric loss factor. By integrating subjective weights (ordered binary comparison method) and objective weights (principal component analysis) through DS(Dempster-Shafer) evidence theory, a combined weight system was constructed, and fuzzy comprehensive evaluation was applied to address the fuzziness of aging levels. Verification experiments showed that the infrared spectrum of the water tree aged cable exhibited carbon-based absorption peaks similar to those of the returned cable. Analysis of the electric field distribution revealed that the opening and closing of the water tree channel caused dynamic changes in electric field strength, and the phenomenon of electric field concentration in the microporous area confirmed the reversible mechanism of insulation performance changes.