Improvement in non-linear electrical conductivity of silicone rubber by incorporating zinc oxide fillers and grafting small polar molecules

Abstract

Silicone rubber (SiR) is commonly used in reinforced insulation parts for high-voltage direct current (HVDC) cable accessories due to its excellent insulation, elasticity, and high-temperature resistance. HVDC cable accessories always suffer from the local electric field concentration due to the electrical conductivity mismatch between reinforced insulation and main insulation, which can ultimately lead to electric breakdown. The non-linear conductive composites based on SiR have the ability to adaptively adjust the distribution of the electric field in cable accessories. This is expected to solve the problem of localised electric field concentration. The zinc oxide (ZnO) and glycidyl methacrylate (GMA) are used as fillers and grafted modifier respectively to improve the non-linear electrical conductivity of ZnO/SiR-GMA composites. The results indicate that grafting GMA can increase electrical conductivity of SiR, while doping ZnO filler enables SiR to have non-linear conductivity characteristics. The combination of doping and grafting modification of the composites achieves excellent non-linear conductive properties at lower ZnO filler content. Additionally, the mechanical properties of the modified composites are enhanced. The simulation results indicate that ZnO/SiR-GMA is the most effective material for homogenising the electric field when used as reinforced insulation for cable intermediate joints.