Single Phase Transformer bolted fault

[Plinko]

I'm looking at several different fault current tables for single phase XFRs and I see several different values for similar sizes and %Z. Three phase calcs seem straight forward (i.e. 3P bolted fault for a 500kVA 277/480 5%Z is about 12,028 amps). I have a table in front of me saying that a 1P XFR 15kVA 120/240 1.6%Z is 5456 amps L-G fault...My calculation shows to be 7813 Amps...I've seen table that show my calculation to be right as well....
WHAT AM I MISSING HERE?

Thanks in advance.

 

[dpc]

A three-wire 120/240 V single-phase transformer is not a straightforward fault calculation. 120 V impedance is different than 240 V impedance, but not in a simple way.

I believe there was a fairly involved discussion on this here a couple of years ago.

Conrad St. Pierre's book on Fault Calculations has a lengthy explanation.

 

[tem1234]

Don't forget, for a 1 phase transformer, you must consider the length of the cable for the return of the current to the transformer.

 

[burnt2x]

tem1234,
You are correct! The line length and the fault current available from the utility also counts much in the calculation of the fault current at the sec of transformers.
Plinko,
Try this spreadsheet (attached)