If a Power Transformer Fails and the transformer
manufacturer suggest that "Do all electrical test on the
transformer?".
What are the test to be conducted in this condition?

Answer Posted / k.prakashchandra

Let me cite an example.We have one 220/110 KV 100 MVA Auto
transformer.After 5 years of service ,it tripped with a
sound, on the following relay
indications.Diff,OS,Bucholtz,OC -R ph and EF (REFR not
provided).On meggering without test charging ,the results
were OK with LT R -body being higher.Then we resorted to
continuity test ,which indicated that LT R phase bushing
has been open circuited.On examination it was found that
the joint in the lead from R-phase winding to bushing was
severed due to bad workmanship.We did not conduct any other
tests.

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