Risk-Based Performance Assessment of a Seismic Retrofit Technique for Medium- and High-Voltage Transformer Bushing Systems

Abstract

High voltage electrical transformers bushing systems have exhibited vulnerability during past earthquakes. The enhanced performance of bushings mounted on rigid base observed during shake table testing does not correlate well with their performance in the field. It is suspected that the seismic performance of high voltage bushings is improved when mounted on a rigid base as opposed to when mounted on more flexible cover plates of transformers. To aid in the protection of these bushing systems, different retrofitting techniques have been researched to protect vital equipment. In this study, the Performance-Based Earthquake Engineering (PBEE) framework developed by the Pacific Earthquake Engineering Research (PEER) center, combined with Monte Carlo Simulation is used to probabilistically evaluate the earthquake-induced economic losses for high and medium voltage transformer bushing systems under various mounting conditions (as-installed and retrofitted with flexural stiffeners) and evaluate the efficiency of the examined seismic retrofit technique in terms of direct and indirect (related to downtime) economic losses.