Evaluation of the seismic performance of isolated electrical transformers under pulse-like excitations

Damage sustained by electrical transformers in past strong earthquakes led to irrecoverable and severe economic losses. The seismic performance evaluation is associated with the loss of proper functioning of transformers. This study deals with modeling existing isolated electrical transformer structures to evaluate the effects of variables that may affect the seismic performance and dynamic characteristics. The results probabilistically determine the seismic performance acceptability of study isolated electrical transformer structures based on the impact of key structural response parameters on the seismic performance of the transformer. Analyses of systems for a wide range of parameters are performed. The effects of horizontal and vertical near-fault pulse-like ground motions, the displacement capacity of the seismic isolation system, limit states of electrical bushings, and details of the isolation system design are considered. Also, the probability of failure of the transformer under the near-fault excitations with pulse-like characteristics is investigated. The results of the research showed that the three-dimensional seismic isolation system has a significant effect on improving the seismic performance of the system for a large number of parameters and can be further effective compared with horizontal-only seismic isolation, offering the lowest probabilities of failure for all cases of transformer and isolation system parameters.