Synergistic Promotion of Electrical, Mechanical and Thermal Properties for Silicone Rubber-based Field Grading Material via Compound Modification

Use of nonlinear conductive SiC/silicone rubber (SR) field grading material (FGM) can improve the local field concentration of composite insulators. Adding large volume fraction and large-size SiC particles (SiCp) into SR can obtain a good field grading effect, but it is accompanied by the deterioration of mechanical properties. Compounding SiC with different shapes can solve this contradiction. By incorporating one-dimensional SiC whiskers (SiCw) to synergize with granular SiCp, SiC/SR FGM with better field-dependent conductivity, mechanical properties and thermal conductivity than large-size SiCp and large volume fraction filling case can be obtained by using smaller size SiCp and lower filling contents. The simulations of 500 k V line insulators show that the modified SiC/SR FGM can reduce the maximum field strength along the insulator surface and at sheath-core rod interfaces by 55% and 71.4%, respectively. The combined application of FGM and grading ring can achieve a complementary effect. Using FGM to partially replace the role of the grading rings, the field strength indicators can still meet the operational requirements after the tube radius and shielding depth of the grading rings at both ends are reduced by 36.2% and 40% separately, which is a benefit to alleviating the problems of high weight and large volume faced by traditional field grading methods.