Electroquasistatic Simulations of Wet-Dry Band Polymeric Insulator with Different Field Grading ZnO Microvaristor Designs

Various field grading materials (FGM) have successfully reduced electric stress in different high voltage applications. This work investigates the performance of Silver- coated zinc oxide (Ag-ZnO) microvaristor characterized by non-linear field-dependent conductivity as an FGM for outdoor polymeric insulators. Electroquasistatic finite element method (FEM) based simulations are carried out on an 11 kV, 2-D, uniformly, and non-uniformly wet insulator with dry bands in the presence of Ag-ZnO microvaristor using COMSOL Multiphysics. Microvaristors of cylindrical and conical shapes are considered, and an optimum design is selected among them. Also, the suitable placement of the microvaristor at the FRP core and silicon rubber interface is evaluated. Simulation studies show that an appropriate microvaristor having the right design and electrical property can significantly reduce the electric stress in the critical region and improve the field distribution.