Analysis of Higher Partial Discharge Values in 36 kV Resin Cast Epoxy Bushings: A Case Study

After studying almost 20 years in past operational data, it was found that partial discharge leading to insulation failure in resin epoxy cast bushings is very frequent. The main cause for these failures is bad design which lead to high electrical stress causing insulation breakdown. Flaws in the manufacturing process under the influence of continuous operation cause insulation failure. Severe operating environment in the field lead to catastrophic failure. In this paper, to understand the root cause of above problems special techniques are discussed including simulation using 3D Electric Field Modelling by Finite Element Method. A case study is showcased where dissection analysis on bushings was implemented on the bushings having high PD values. Finally, partial discharge test on full scale prototypes are validated with 3D field computation results.