Seismic performance assessment and reliability verification of molded transformers based on shaking table tests

In this study, shaking table tests were conducted to assess and analyze the seismic performance of the molded transformers used in actual hydropower plants. The test method was executed by adjusting the acceleration magnitude through the generation of artificial earthquakes that comply with the seismic performance criteria outlined in the ICC-ES AC 156 procedure. Additionally, a performance assessment for earthquakes with a magnitude of 5.0 or greater, recorded domestically in recent times, was concurrently conducted to analyze the dynamic behavioral characteristics. The test results indicated that there was no functional damage to the test specimen in all shaking table test procedures. However, structural damage began to be visually confirmed through a visual inspection when the artificial seismic intensity exceeded 100%, and at 150%, cumulative deformation was measured at the lower part. This is attributed to the nonlinear behavior caused by the structural characteristics of the heavy upper structure, its high centre of gravity, and the relatively small load and high flexibility of the lower frame. The excessive relative displacement between the upper and lower parts resulting from this phenomenon is anticipated to lead to potential damage, such as collisions with surrounding equipment or impact on adjacent facilities.