Question { Alstom, 21897 }

I HAVE A 1 MVA TRANSFORMER, I WANT TO KNOW THE FAULT LEVEL OF
THE SYSTEM ( WHAT IS FAULT LEVEL PLEASE EXPLAIN WITH EXAMPLE)

Answer

FAULT LEVEL MEANS SHORT CIRCUIT CAPACITY OF TRANSFORMER.YOU
HAVE NOT MENTIONED THE VALUE OF TRANSFORMER RATIO & % OF
IMPEDENCE.ASSUMED VOLTAGE RATIO= 11KV/415 V & % OF
IMPEDENCE=6%.
RATED FULL LOAD AMP OUTPUT =1MVA/(415 X 1.732)=1391.25A
SO SHORT CIRCUIT CAPACITY OF TRANSFORMER= 1391.25/6%
=23187.44 A
IF ANY FAULT OCCURED THEN THE ABOVE TRANSFORMER WITHSTAND
THE SHORT CIRCUIT CURRENT OF 23187 A.