First Advisor

Peter Dusicka

Date of Award


Document Type


Degree Name

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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A research project report submitted in partial fulfillment of the requirement for the degree of Master of Science in Civil and Environmental Engineering.

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