Predicting Power-Transformer Bushings' Seismic Vulnerability Mounting Stiffness and Coupling

Large power transformers are both expensive and vulnerable to seismic failure. Excessive amplification of earthquake loading to power-transformer bushings beyond the bushings' rated strength can occur if the system's structural dynamics produce unpredictable and unfavorable resonance behavior. Determining the degree of vulnerability to large seismic amplifications is not straightforward, and general design recommendations do not always resolve problems that can potentially arise. This paper considers a number of case studies in an attempt to postulate a set of critical factors that might facilitate better prediction of bushing amplification. Furthermore, several additional case studies are summarized in order to add to the evaluated data set and provide more validity for drawing broader conclusions.