Fragility Testing of a Power Transformer Bushing; Demonstration of CERL Equipment Fragility and Protection Procedure

Abstract : This report presents a demonstration of the CERL Equipment Fragility and Protection Procedure (CEFAPP) as used in the testing of a large power transformer bushing. CEFAPP defines the capacity of critical equipment by tests conducted on a shake table. Equipment capacity is defined in terms of amplitude of motions with respect to frequency that cause equipment failure. These spectral amplitudes can be defined in terms of either response spectrum or support motion spectral amplitude, both plotted with respect to frequency. Equipment failure may comprise loss of function, physical damage, or some measured response that is determined by the test engineer to be unacceptably high. The bushing failure mode defined in this application was leaking and slippage at the porcelain flange interface. The equipment capacity as defined by this failure envelope is later compared with the demand as defined by the user design spectra. This demand may be site specific or code based response spectra, or spectral motions at equipment installation location based on a detailed numerical analysis of the building in which the equipment is to be installed. For the bushing presented here, capacity is defined in terms of response spectrum of the shake table support motions that can be compared with site specific response spectra or design response spectra based on IEEE 693. Technical details of CEFAPP may be found in a companion report, USACERL Technical Report 97/58.