XLPE Electric Field Reversal Caused by Temperature Rise of Oil-Filled DC Cable Terminal

With the global energy structure evolving, high-capacity, long-distance power transmission will increasingly employ dc systems. Accurate modeling and analysis of the dc cable terminal (CT)—a power device with insulating dielectrics in solid, liquid, and gas states—are crucial for preventing fault formation. Based on the thermal-assisted/variable-range hopping conductance model of cross-linked polyethylene (XLPE), this study identifies the electric field reversal phenomenon in the radial section of XLPE under various conditions. By using different position parameters and operating parameters as independent variables for electric field intensity fitting, we enhance the efficiency of accurately obtaining the internal electric field intensity during the dc CT operation. The analytical results show that the internal electric field is most uniform when an appropriate load is applied to the conductor, representing the healthiest operating mode for the dc CT. This study provides a reference for determining the internal insulation state of the CT under different operating conditions, enabling early detection of potential issues and the adoption of corresponding countermeasures.