Characterization and health index assessment of 34.5 kV cross-linked polyethylene (XLPE) power cables

Degradation of the Cross-Linked Polyethylene (XLPE) insulation impacts the performance of the cable that leading to cable failure and instability of the electrical grid. The main objective of this paper is to investigate the characteristics of naturally aged 34.5 kV XLPE-insulated cables served in a high-temperature field using advanced characterization techniques. Then, we used the measured electrical and mechanical properties to assess the cables’ condition using the cable health index (CHI), which was determined using the entropy and the CRITIC methods. Cable samples aged 5 and 10 years were selected and analyzed using characterization techniques such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and 3D X-ray tomography to diagnose changes in structural, chemical, and thermal properties. Additionally, we have tested the electrical parameters (breakdown voltage and flashover voltage) of XLPE cable to evaluate its dielectric performance. Tensile strength and elongation analysis were carried out as well to evaluate the XLPE mechanical performance. Study results demonstrated more surface cracking, elemental variation, and decreased crystallinity in the XLPE insulation at 10 years of age. DSC results demonstrated altered thermal properties in aged samples. The breakdown voltage decreases by 13.6% due to defects in the 5-year aging sample, while the drop was 20.85% in the 10-year aging sample. Among the three approaches, the integrated entropy/CRITIC weighting achieves the highest classification accuracy and ROC–AUC, providing a more reliable and discriminative indicator of cable health. These findings support condition-based maintenance and life extension strategies for high-voltage systems.