Seismic qualification and fragility testing of porcelain transformer bushings

Seismic qualification and fragility testing of two 196kV porcelain transformer bushings is discussed. The importance of power transformers in electric substations combined with electric utility experience with past performance of porcelain bushings during earthquakes provided the impetus for performing this work. A new standard for the seismic qualification of electric substation equipment, IEEE 693-1997, has been under development for the past several years, was used as the basis for the testing protocol. This paper describes the mechanisms of structural resistance and failure modes of porcelain bushings, and discusses the random input motion shake table tests performed. Key results and responses are summarized, for shake table testing at levels up to about 2g peak ground acceleration.