Failure Analysis of Transformers under Impulse Test

Transformers are the most critical and costly components in AC power systems. Insulation is weakest link transformers, design quality of a transformer's insulation system shall be confirmed by performingdielectric tests according to National or International standards. The impulse test more among dielectric tests, as it verifies integrity whole transformer. However, concluding result difficult when minor discrepancies exist earth's current waveforms. This paper presents two such case studieswith distribution class transformers.