Study on Nonuniform Thermal Aging State of XLPE Based on Dissado–Hill Model

Under actual working conditions, the cable is subjected to electrical, thermal, and mechanical stresses, and its aging is nonuniform along the radial direction. To fully dig out the rich information hidden in the frequency-domain spectroscopy (FDS) to evaluate the nonuniform thermal aging state of cross-linked polyethylene (XLPE), based on the Dissado–Hill (D–H) model, the relationship between the D–H model parameters and the thermal aging state of XLPE nonuniform aging samples was analyzed, and an evaluation method was proposed. Findings proved that with continuous thermal aging, the carrier density in nonuniform samples increases, the force between microparticles in clusters decreases, the charge carrier migration between clusters becomes smooth, and the intercluster motion is strengthened. The parameter $\omega _{c}$ has a strong correlation with the elongation at break rate (EB%) of the most severely aged part of the nonuniform sample, and it is a potential tool to mine the hot spot information of XLPE. Finally, XLPE samples with different aging temperatures are used to verify the proposed evaluation method, and the error is 2.89%, which shows its effectiveness.