Portland State University. Department of Civil & Environmental Engineering
Date of Award
Master of Science (M.S.) in Civil & Environmental Engineering
Civil and Environmental Engineering
Electric insulators and insulation -- Testing, Electric transformers -- Earthquake effects, Gaskets, Damping (Mechanics)
Transformer bushings have shown to have an unsatisfactory performance during earthquakes and have therefore been chosen for further testing. How the bushings fail, and how this failure can be prevented has been analyzed. Two used 196 kV bushings made by General Electric were chosen for seismic testing at the iSTAR laboratory located at Portland State University in Portland, OR. The multiple objectives that brought about these tests were: to determine how the bushings failed due to gasket extrusion at the porcelain-flange connection and to verify that the failure was due to pure tipping and not sliding, to determine the damping introduced when the bushing was supported by a flexible plate with a welded support structure and excited at large amplitudes, determine the natural frequency of the assembly, and to determine the effects of added mass to the top of the bushing. To meet the objectives, the bushings were tested using two different test set-ups: a stiff mounted setup, and a flexible mounted setup. For both test set-ups, the bushings were first mounted inside a turret to simulate an electrical transformer, and the turret was mounted to a flexible or stiff plate, depending on the test. The flexible or stiff plate tests were bolted to a one-direction shake table. The bushings were individually subjected to static and dynamic testing until failure due to oil leakage.
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Shields, Joanne R., "Seismic Evaluation of 196kV Transformer Bushings" (2017). Civil and Environmental Engineering Master's Project Reports. 35.