Thermal Test Performance of a Modern Apparatus Bushing

As part of an overall program for establishing thermal loading capability of substation electrical equipment, it was necessary to investigate the inherent thermal capabilities of typical oil impregnated paper bushings used in power transformers and circuit breakers. The investigation described in this paper included developing and implementing a test program to determine actual bushing temperature levels for load currents over rated nameplate value, tabulating and analyzing test results, performing an accelerated thermal life test, and finally, evaluating the physical condition of the bushing insulation to determine the effect of elevated temperatures on its integrity.