Effect of Mechanical Stretching on Nonlinear Conductivity and Dielectrics Breakdown Strength of SiR/SiC Composites

Abstract

This paper focuses on the effects of mechanical stretching on nonlinear conductivity and dielectrics breakdown in silicone rubber (SiR)/SiC composites for HVDC prefabricated cable joints. The DC conductivity and breakdown strength of SiR/SiC composites are measured with stretching ratios of 0 to 60%. The results show that when the SiC volume fraction is 17.1 vol%., the conductivity of the composites decreases with the increasing stretching ratio. For the 29.2 and 38.2 vol” composites, the conductivity increases with the increasing stretching ratio, but decreases as the stretching ratio exceeds 10 and 20%, respectively. The breakdown strength is proportional to the stretching ratio in the 17.1 and 29.2 vol% composites, but inversely proportional when the SiC volume fraction is 38.2 vol%. The effect of mechanical stretching on the nonlinear conductivity in the composites can be contributed to conducting paths varying with transverse stretching and longitudinal compression. The electric field distribution and decohesion of weak interface will be affected by mechanical tension, thereby affecting the breakdown strength of the composites. This study herein provides a recommendation that SiR/SiC composites with a SiC volume fraction of 29.2 vol% have potential application prospects for regulating electric field in prefabricated cable joints.