How do you calculate the short circuit current of a power transformer?

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Suppose Transformer Rating is 15 MVA & voltage ratio 33/11 KV .
So current rating ration 262.43/787.37.
if percentage impedance=7.5%
Then during the short ckt of Test its required 7.5% of voltage to follow full load current. So if supply 2.417 kV to follow the current 262.43 A .
In Practically we supply 415 V i.e 0.1717% of 2.417kV.
so during supply short ckt current follow is =262.43*0.1717= Approx 45A.

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