Improved Modelling of Electrical Substation Equipment for Seismic Loads

Abstract

This chapter discusses the improvement in modeling of electrical substation equipment for seismic loads. Improvements in the methods used for modeling electric substation equipment through a combination of experimental and analytical studies are explored. The experimental studies were a combination of in-situ field measurements of this equipment at four sites selected from Pacific Gas & Electric facilities and laboratory experimental modal analyses. The in-situ tests considered the transmissibility of the ambient and forced vibration ground motion to the support locations of the equipment, as well as the low level response of the equipment itself due to force-calibrated hammer excitation. The experimental modal analyses considered the linear response of the equipment under low level, force-calibrated hammer excitation. The analytical studies interpreted the vibration data using commercially available software in order to define the frequency, mode shape and damping characteristics of the equipment. Multiple degree-of-freedom, lumped parameter modal models were developed for the equipment. Simple analytical models were developed that closely matched the experimental data in order to predict the transformer's dynamic response under dynamic loading. These modal models can be integrated with standard finite elements to model structural response modifications due to mass or stiffness changes resulting from support structures. The analytical studies recommend improved methods for modeling equipment and major components.