Modeling and Seismic Performance Evaluation of High Voltage Transformers and Bushings

Keywords: Seismic performance evaluations.  High voltage transformers.  Bushings.  Simplified models.  Lifelines.  Boundary conditions.  Dynamic behaviors.  Global amplification.  Damage.  Failure.

Abstract: This study deals with the modeling of existing transformers and bushings to evaluate the effects of modeling variations and possible structural modifications that may affect their dynamic characteristics, and the significant interactions between various components and the high voltage bushings.  Detailed techniques for the modeling of the bushings are presented in this report along with a discussion on the sensitivity of interactions.  Additional investigations were conducted to explore feasibility and approximations in analyzing simplified models in which the tank cover and the bushings are separated from the transformer.  The report presents the sensitivity study on modeling various boundary conditions in the simplified model in an effort to match the response of the bushings with the response obtained from the full model.  The report also presents the global amplification effects of the tank construction on the response of the tank cover at base of bushings, and the effects on the apparent dynamic properties of bushings.  Recommendations for guidelines on modeling transformers and bushings can be derived from this work.