AVAILABLE FAULT CURRENT CALCULATOR QUESTION

[florida-sparkey]

Does anyone know if the great free calc by John S. for available fault current is applicable when the transformer (L-N) 120V fault is greater than the (L-L) 240V? I am using (Ver 2017.) If so, do I just insert the larger current as given by Power Co whether it be the L-N or the L-L? In this case, 50 KVA xformer has 13,900A L-L and 20,800A available L-N. Thank you in advance!

 

[florida-sparkey]

So I did the math on a point to point using the exact Bussman formulas. I have answered my question. For his calc, you input the L-L fault as he does the 1.5 * L-L for the center tapped xfmr to get M. However, I think I found a fault in the program. I think the L-N in the version I have uses the wrong value for the final L-N fault. It should use 1.5 * I L-L * M. Or at least that is how is is preformed in the Bussman calc example given. Anyone know which is correct?

 

[WA_Sparky]

I've always been instructed to use the worst case scenario out of the two numbers. If the SCCR values are within 5-10% of the OCP rated KAIC, ive just went to the next level of protection.