Optimization of Electric Field Distribution for 33kV Polymeric Insulator Using Non-linear Field Grading Composites

Abstract

This study investigates non-linear resistive field grading composites based on Zinc Oxide microvaristors to optimize the distribution of the electric field along a 33 kV composite insulator. In this study, the effect of different switching parameters of field grading composites such as field switching threshold, non-linearity coefficient, and the initial conductivity on the field distribution is presented. A suitable design of field grading composites is proposed for effective stress control near end-fittings and along the insulator surface. The proposed graded insulator is evaluated with the optimized switching parameters using COMSOL Multiphysics 5.5 and 2D axisymmetric models. Electric field enhancements at the triple junction points at both terminals are successfully suppressed. This consequently decreases the probability of corona and electric surface discharges, reduces the possibility of dry bands formation, raises the flashover voltage, and improves the long-term operation of the polymeric insulators in service.