Effect of Crosslinking Temperature on the Insulation Performance of XLPE Secondary Crosslinking Insulation Interface Layer

To investigate the impact of temperature variations during the secondary crosslinking of cross-linked polyethylene (XLPE) on the insulation performance of the interface layer, commercial XLPE cable pellets were subjected to flat hot pressing at 140 °C, 160 °C, 180 °C, and 200 °C. XLPE insulation interface layers were prepared at different secondary crosslinking temperatures. The samples were characterized by gel content, differential scanning calorimetry (DSC), thermal elongation test, power frequency breakdown voltage, and scanning electron microscope (SEM). Key parameters, including crosslinking degree, crystallinity, thermal elongation, and characteristic breakdown voltage of the samples, were obtained. The results indicate that as the secondary crosslinking temperature increases, the crosslinking degree of the samples rises, while thermal elongation initially decreases and then increases. Crystallinity shows a decreasing trend overall. The characteristic breakdown voltage shows a trend of increasing first and then decreasing. When the temperature is 180 °C, the characteristic breakdown voltage reaches its maximum value. Therefore, increasing the secondary crosslinking temperature can help improve the mechanical and electrical properties of the XLPE insulation interface layer. However, crystallinity decreases at excessively high temperatures, which has a negative impact on insulation performance.