1. The Wind Solar Storage Division of State Key Lab of Control and Simulation of Power System and Generation Equipment School of Electrical Engineering Xinjiang University Urumqi 830047 China; 2. State Key Lab of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing 100084 China; 3. State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Beijing 102206 China
Abstract：This study aims to explore the effect of the combined thermal-mechanical stress on the insulation performance of the silicone rubber in cable accessories. Specifically, a combined thermal-mechanical aging test of the silicone rubber was designed and conducted; the mechanical properties, electrical properties, and microstructure of silicone rubber before and after thermal aging were compared and analyzed. As aging increases, the tensile strength and elongation at break of the specimen decreases and the hardness increases, respectively. The breakdown strength of the sample first increases and then decreases after thermal aging. Under certain aging time, the breakdown strength decreases with the increasing tensile stress while the relative dielectric constant gradually increases. The test results of cross-linking density and infrared spectroscopy suggest that at the early aging stage, the oxidative cross-linking reaction occurs between the main chains of the silicone rubber, leading to the decreased free volume and carrier mobility and increased breakdown strength; at the later aging stage, the cross-linked system structure and the molecular chain is destroyed, causing the increased free volume and carrier mobility and decreased breakdown strength. Under the action of mechanical stress coupling, the curled molecular chain is stretched along the direction of mechanical stress, and the stretched molecular chain is more likely to break at high temperatures. As a result, the insulation performance of the material further deteriorates. These results lay a theoretical foundation for the assessment of the aging state of silicone rubber for cable accessories.
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2022, Vol. 37 
