Calculator — Available Fault Current

Cable impedance reduces AFC to ≈ 9.2 kA at the panelboard.

Long cables reduce AFC. Subtract voltage drop impedance from available current. ⚠️ Manual calculations are error‑prone for complex systems. Use a dedicated calculator or software (e.g., EasyPower, SKM, ETAP, or web tools like Copper Bussmann FC2). Example Scenario Transformer: 500 kVA, 480V secondary, 5.75% Z FLA secondary = 500,000 / (480 × 1.732) ≈ 601 A I_fault (transformer terminals) = 601 / (0.0575) ≈ 10,452 A (10.45 kA) available fault current calculator

Get from utility: Fault MVA or Short-circuit current at transformer primary . Cable impedance reduces AFC to ≈ 9