Temperature Responses to Step Changes in the Load Current of Power Transformers

Comprehensive load/thermal testing was performed on a 400/400/125 MVA, ONAF-cooled transformer. It was shown that the local hot-spots in the windings, core, and structural parts rise much faster at load increase than what an exponential function based on the time constant of top oil would predict. This paper analyzes these fast rises more in detail for hot… (More)