Transformer outlet short circuit caused by insulation breakdown of bushing through cabinet happens frequently.In this paper

insulation breakdown of the bushing cabinet is classified as air insulation breakdown and epoxy insulation breakdown.To clarify the causes of two kinds of breakdown

the insulation breakdown faults of bushing through cabinet happened in a certain province in the third quarter are analyzed

and the bushings with suspended shield or air gap are simulated on electric field.According to the results

the air insulation breakdown was caused in most cases by internal equipotential suspended shield

and the epoxy insulation breakdown generally resulted from the insulation deterioration due to air-gap discharge or breakdown.The results are in line with the case analysis.In order to study the effect of shielding improvement on air gap discharge

considering the shield-skirt treatment measures to improve the fringe effect of 800 kV gas insulated switchgear

the shield of the bushing with air gap is improved

and the electric field of the bushing is simulated.It is shown that shield-skirt improvement exerts little effect on suppressing air-gap discharge.Thereby

conclusion is drawn that only shield optimization is not available to prevent insulation breakdown of the bushing through cabinet.The obtained simulation and analysis results may provide a reference for design and installation of the bushing through cabinet.Simulation and analysis results for the cabinet bushing has certain guiding significance to the design and installation.