Influence of Flange on Seismic Performance of 1,100-kV Ultra-High Voltage Transformer Bushing

Abstract

Failures of the metal flange were observed in transformer bushings in previous earthquakes. In order to evaluate the influence of the flange on the seismic responses of 1,100-kV ultra-high voltage (UHV) bushing, two types of flanges were selected, which used different materials and layouts. The finite element (FE) and theoretical analyses were first carried out. The results indicate that there is an out-of-plane rocking effect at the flange bottom plate, and the flange will be damaged if the stiffeners are improperly designed. Then two identical bushings using different flanges were tested on the shaking table. The bottom plate of the cast aluminum flange cracked along the stiffeners accompanied by oil leakage. However, the UHV bushing with stainless steel flange survived in the test. It is concluded that the properly designed flange could improve seismic performance of UHV transformer bushings.