Earthquake simulator testing of base-isolated power transformers

This paper presents a comprehensive study involving triaxial earthquake simulator testing on seismic isolation of electric power transformers. In this study, two isolation systems were developed: one using sliding bearings combined with rubber bearings and the other segmented high-damping rubber bearings. Triaxial earthquake simulator testing was performed using a large-scale transformer model equipped with a real bushing. The effectiveness of the base isolation system in reducing the response acceleration of power transformer systems was demonstrated. Important observations were made on the seismic responses of the transformer and bushing. In particular, the vertical component of the ground motion induced a high-frequency response of the bushing when the transformer was isolated with the sliding isolation system. This is because the vertical motion changes the friction forces in the sliding bearings that excite high modes in the transformer-bushing system. Furthermore, the effect of the interaction with the bushing connecting cables on the response of the bushing in the base-isolated system was experimentally evaluated. In conclusion, the base isolation technology, when properly designed, is a highly effective measure for seismic protection of power transformers.