Fault analysis and structure optimization of 40.5kV wall bushing

Based on the explosion fault of wall bushing used in a 35kV substation, analyzing operation environment, appearance inspection of bushing and electrical test on other bushings operating well, the key causes which lead to this failure were found: design defects and high non-uniform electrical field distribution, simultaneously, heavy operation condition and high humidity are the exterior factors resulting in the explosion fault. For improving the electrical performance of bushing and electrical field distribution, the new design with shield ring was presented. At the same time, improvement solutions, adding the heater and fan in busbar compartment, used to reducing the humidity inside busbar compartment of switchgear were presented in this paper. After these improvement measures were carried out, the switchgears operate very well in safe condition.