Role of Very Fast Transients in HV Transformer Bushing Failures and Their Remedial Measures

Abstract

Without HV Bushings, large transformers are unthinkable and failure in any of the bushing results in transformer failure as well. Bushing failures are rarely analyzed separately from the transformer failure. The approach laid out in this paper is to expand bushing failure research so that besides terminal transformer failures, incipient failures (non-transformer-damaging) are also looked up to. Bushing failure mechanism in the presence of very fast transients (VFT) during AIS bus bar switching lead to certain failure scenario, that is been described and supported by a case study. Mitigation measures for such failure mechanism are also suggested.