I've read several posts regarding single phase systems. I hate to beat the subject to death but need opinions on how to handle them. The customer wants an arc flash analysis done. The utility feed is 12kv single phase to a 75kva transformer. The secondary side is 240, single phase 3 wire. The system presently can't be modeled in Etap because you can't define a single phase utility feed. Is the answer to do all manual calculations?

I've seen recommendations to model the system as 3 phase but how do you start when provided with single phase fault current from the utility? How do you handle the request from the customer?

Thanks for your help.