Electrical–Thermal–Mechanical Matching Properties of the Interface Between Main Insulation of High-Voltage Cables and Accessory Silicone Rubber Insulation

The cable accessory structure involves a double-layer composite insulation interface and exists the problem of interface matching between the main insulation and the accessory insulation. In this article, the electrical-thermal-mechanical properties of two combined interfaces, crosslinked polyethylene (XLPE)/silicone rubber (SiR) and polypropylene (PP)/SiR, are tested. Also, the interface matching properties of the two combined interfaces are compared and analyzed. For electrical properties matching, the results show that the interface of PP/SiR accumulates more space charge than that of XLPE/SiR. The maximum interfacial charge accumulation is $- 4.35\times 10^{-{4}}$ C/m2 for XLPE/SiR and $- 6.01\times 10^{-{4}}$ C/m2 for PP/SiR. In terms of thermal properties matching, the thermal expansion coefficient of XLPE is the highest. As for mechanical properties matching, the interfacial pressure of XLPE/SiR and PP/SiR dropped below 0.1 MPa at 23 and 96 h. The molecular simulation results show that the molecular chains of PP have strong dynamic ability, and the free volume change and trap depth are largest for SiR. The experimental results show that XLPE/SiR is better matched in electrical properties, while PP/SiR is better matched in thermal and mechanical properties. This work is an important reference for improving the safety of cable accessories and promoting the development of environmentally friendly PP cables.