Cooper Busmann has/had a bulletin EPR-1 called "Electrical Plan Review Short-Circuit Currents, Interupting Ratings, and Current Limitation" which goes through a simplified method. Mike Holt also has/had an excel spreadsheet that used the same or similar method.
Neither of these methods is great but will get you ballpark often and if you are well within the rating of the equipment you are likely OK. Neither are good for ArcFault studies. The Rocket Scientist method also takes into account the inductance of the source each step of the way (not just the inductance of that point your are studying)and results in higher levels of fault current available. To learn about this bettter method you could take a course from
www.brainfiller.com. Another option is purchasing expensive software, which I have neve bothered with due to budget.
Shane
