Thermal distribution analysis and suppression mechanism of carbonized tracking and erosion in silicone rubber/SiO2 nanocomposites

For high voltage outdoor silicone rubber insulators, carbonized tracking growth and erosion of the material are the major failure modes and it can adversely influence the reliability of power delivery networks. Thermal accumulation in the dry band arcing region is a key factor for temperature build-up and it causes thermal depolymerization and promotes tracking on the insulator surface. This work investigates the effect of nano-SiO2 doping on the thermal accumulation induced tracking growth and erosion of silicone rubber. A tracking-erosion model is presented to explain how doping directly affects such mechanisms. Experimental results show excellent enhancement in the performance of silicone rubber with higher doping contents in terms of physical tracking growth, erosion, leakage current and thermal accumulation in the arcing region. These favorable findings could be attributed to the better thermal conductivity which allows the high energy thermal flux to dissipate away more efficiently. Moreover, thermogravimetric analysis results indicate that nano doping enhances the physical and chemical cross-linking points which restrict the segmental motion at the particle matrix interface. It can promote thermal stability of the nanocomposites which is clearly witnessed in the physical results. The proposed tracking-erosion model suggests that colliding scattering of nano-SiO2 particles reduces the secondary electron collapse which impedes the release of high energy and restricts thermal degradation.