Low-frequency dielectric and dynamic mechanical properties of XLPE retired cables

This study analyzes the low-frequency dielectric and dynamic mechanical properties of the cross-linked polyethylene XLPE material from the inner, middle, and outer insulating layers with different operational years. The fourier transform infrared reflectance spectroscopy, thermogravimetric analysis, and differential scanning calorimetry were used to understand the relationship between the low-frequency dielectric and dynamic mechanical properties related to the operating years. Results show that the low-frequency dielectric and dynamic mechanical properties of the middle layer of the high-voltage XLPE insulating cables are better than those of the inner and outer layers. The crystallization peak temperature of the cable insulating material decreases with operating years. In our experiments, the restriction of molecular movement and volatilization of crosslinking byproducts during operation result in the improvement of properties for a set number of years.