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Calculate fault at transformer with MVA method...

Calculate fault at transformer with MVA method...

Calculate fault at transformer with MVA method...

(OP)
Can I use the MVA method instead the pu method?
Question is from Complex Imaginary Test 2 Question 79:

3 phase generator serves a 5/25kV transformer rated 6MVA. The generator's subtransient impedance is j0.39pu and the transformer rated impedance is 6%. If the generator is rated 11MVA, its contribution (MVA) under fault condition at the transformer's secondary terminal is nearly?


11/0.39 = 28.2MVA
6/0.06=100MVA

Since in series: 100(28.2)/(100+28.2) = 21.997 MVA

If= 21.997MVA/1.73(25kV)

Can I do this? or I am completely off??

RE: Calculate fault at transformer with MVA method...

Looks good to me. (Unless the undefined transformer secondary is the 5 KV side).
The MVA method provides answers that are close enough for most design questions. I use it for sanity checks on ETAP and Easy Power results. It helps me find the data entry errors.

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