Simulation Study of Interfacial Pressure Evolution of Cable Joints Considering Stress Relaxation of Silicone Rubber

The electrical properties of high-voltage cable joints are closely related to the interface pressure between silicone rubber and cross-linked polyethylene (XLPE). In order to explore the evolution of the interface pressure of the actual cable joint, a simulation study of the interface pressure of the 220 kV cable joint was carried out considering the stress relaxation phenomenon of silicone rubber during the aging process in this paper. First, the finite element model was established based on the characteristics of the physical field of the cable joint, and the initial pressure distribution of the silicone rubber-XLPE interface of the cable intermediate joint was determined. Second, the finite element analysis results were verified by the analytical solution of the mechanical theory calculation and the measured results of the preset pressure sensor. Then, combined with the results of thermo-mechanical aging experiments of silicone rubber, a method was proposed to convert the stress relaxation of silicone rubber into the change of interference during the aging process, and a multi-parameter finite element analysis method considering the stress relaxation and elastic modulus changes in the aging process was obtained. This method was successfully applied to analyze the interfacial pressure between insulating silicone rubber and XLPE in cable joints. According to the analysis, the aging of silicone rubber leads to stress relaxation and increase in elastic modulus at the same time. The simulation results considering the elastic modulus and stress relaxation show that the interface pressure decreases from 0.156 MPa to 0.129 MPa, 0.125 MPa and 0.107 MPa after thermo-mechanical aging at 100 ℃, 125 ℃ and 150 ℃ for 2040 h, 1680 h and 1200 h, respectively. It is shown that the effect of stress relaxation on the interface pressure is more significant, the interface pressure decreases with the increase of aging time, and the increase of temperature will significantly accelerate the attenuation process of the interface pressure of the intermediate joint. The results of this paper can provide a theoretical basis for improving the design and operation reliability of cable intermediate joints.