Interface Pressure Calculation Based on Finite Element Simulation for 525 kV DC Prefabricated Composite Cable Terminations

Accurate calculation of interfacial pressure in extra-high-voltage direct current (EHVDC) cable accessories holds significant engineering value. The mechanical structure of EHVDC prefabricated composite cable terminations is complex, with no available analytical solutions, and experimental measurements pose considerable challenges. In this study, the hyperelastic mechanical behavior of the ethylene–propylene–diene monomer (EPDM) material widely used as reinforced insulation of EHVDC cable accessories was first analyzed, with the Yeoh model selected and its parameters obtained via uniaxial tensile testing to serve as input for the simulations. Subsequently, a finite element (FE) model of a 525 kV DC prefabricated composite cable termination was constructed, and the corresponding mechanical boundary conditions were applied. The installation process of the rubber components—including EPDM insulation and stress cone structures—was simulated. Both the interference fit between cross-linked polyethylene (XLPE) and EPDM and the application of mechanical thrust loads were considered, and the resulting interfacial pressures were calculated. The results indicated that the interfacial pressure generated by the interference fit was relatively small, with a maximum value of only 0.108 MPa. After the mechanical load was applied, the minimum interfacial pressure exceeded 0.1 MPa, and the maximum reached 0.35 MPa, meeting practical requirements. Two stress concentration points appeared at the XLPE–EPDM interface: one near the base of the stress cone and the other at the top of the reinforced insulation. These were related to mechanical compression effects induced by the applied thrust load between components. Notably, during installation, apex extrusion of the reinforced insulation was observed due to compression, and warping at the base of the stress cone caused by bracket rod pressure was visually evident.