Failure analysis of dry type power transformer

This paper provides the failure analysis of three phase, dry type, silicone resin vacuum pressure encapsulated, 750/1000 kVA, AA/FA, 34.5 kV-480 Y/277 V, delta-wye, power transformer. Transient overvoltage switching surge propagation through the transformer winding and protection margin is discussed. An arbitrary sensitivity of 10 pico-coulombs (pc) at 120% rated voltage generally used for the partial discharge tests at the factory may be inadequate for the design of the failed transformer.