Electro-Thermal Coupling for Simulation of 52 kV Polymeric Bushing with Nonlinear ZnO Microvaristor Under Different Environmental Conditions

Bushings are considered as one of the main components of power transformers, a key element of the transmission network. Recently, bushings with composite housings have been adopted because of their advantages over ceramic bushing, e.g., reduced weight, reduced explosive hazard and better performance under polluted conditions and under seismic activity. However, excessive electric field intensity can originate tracking and erosion effects on the insulating material affecting the withstand capabilities of the bushing. This paper investigates the electric field distribution coupled with temperature distribution on a 52 kV polymeric bushing to determine any vulnerable areas. The simulation evaluates the electrical and thermal stress reduction in these identified areas by introducing ZnO-microvaristor material, as a possible solution to mitigate these damages. A suitable bushing design using this field grading material is proposed for effective stress control near the flange ground terminal to offer the manufacturers additional confidence for applying novel insulating materials.