Abstract

Porcelain bushings are universally employed for power transformers. However, non-condenser bushings are unsuitable for high voltage applications owing to their extreme non-linearity in potential and electric field distribution. High voltage insulated bushings are required to bring out the electrical energy through earthed barrier. Synthetic resin bonded paper condenser bushing (SRBP) and oil impregnated paper (OIP) bushing are commonly used bushings. These bushings have series of dielectric layers with conducting aluminum foils in between each layer to improve the distribution of electric field. The present paper discusses analysis of electric field distribution in a 145 kV OIP bushing with varying number of foils and their thickness using finite element method. Simulation results show that 9 foils, 4mm thickness each and 2mm gap between the foils is optimum for better distribution of the field. The paper also discusses the experimental verification of the field estimated through the simulation.