volume 10, issue 4, P1757-1763 1995
DOI: 10.1109/61.473383
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Abstract: A relatively high failure rate of the internal insulation of EHV power transformers has been reported by public utilities. This prompted a study of the safety margin of EHV transformers in service and under test. In this project, a number of transient overvoltages were digitally recorded in EHV substations and the transient voltage distribution along the HV winding was measured digitally on many untanked transformers.With this information, a transient induced at (and across) every disc of the winding by a sys…

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