Electric–Thermal Field Analysis for EPR On-Board Cable Terminal Using Stress Tube Modified by ZnO Nonlinear Material

The terminations of 25-kV ethylene–propylene rubber (EPR) cables are prone to temperature distortion points due to their structural characteristics and the uneven distribution of the internal electric–thermal field. Scratch defects that occur during the installation of the cable terminal increase the severity of the problem, accelerate the aging of insulation materials around the defects, and greatly reduce the insulation performance. Herein, to solve this problem, a kind of nonlinear stress tube material whose conductivity was related to the electric field and temperature was proposed. COMSOL simulations were performed, and comparative analysis was conducted of the electric–thermal field distributions of the cable terminal under normal conditions, with internal scratch and metal particle defects when the stress tube was made of high-dielectric-constant materials and nonlinear materials. The results showed that the distortion degree of the electric and thermal field distributions could be effectively alleviated after the modification. At the same time, partial discharge tests, infrared thermography tests, and voltage breakdown tests were used to test the electrothermal performances of cable terminals under various conditions. The results verified that the distortion of the electric–thermal field at the cable terminal was improved.