A study of electrical stress grading of composite bushings by means of a resistive silicone rubber coating

Local discharges in the vicinity of the mounting flange of composite bushings due to the electric field enhancement can cause insulating material degradation and finally lead to failure. In this paper, a proposed solution to this problem by employing a resistive silicone rubber coating on composite HV bushings was investigated. Finite Element Method (FEM) analysis of the electric field distribution along the surface of bushings by FEMLAB® simulation and potential measurements by an electrostatic probe (ESP) technique confirmed that the stress grading effect of a 100 MΩ resistive coating results in a linear potential distribution and the tangential field is significantly reduced in the region of the mounting flange.