How do you perform a short circuit calculation for an electrical system?

Short circuit calculations determine maximum fault current at various points in the system. Start with utility available fault current at service entrance, then calculate impedance contributions from transformers (using %Z rating), cables (resistance and reactance per length), and other equipment. Total impedance determines fault current: Isc = V/(sqrt(3) x Z). This value ensures equipment (breakers, bus bars, cables) has adequate interrupting rating and withstand capability.