I have a 50kVA dry type transformer which had failed, with rating:
1. Input (LV, primary winding): 400V, 72.17A
2. Output (HV, secondary winding): 21.5kV, 1.34A
The failed area was found to be the HV winding, where short circuit of winding and sign of local overheating was observed . Calculations showed no overload to input or output.
What would have cause the overheating? probable cause of the failure?