Calculate generator short circuit fault currents — sub-transient, transient, and steady-state for protection coordination and equipment rating.
This calculator follows IEC 60909 and IEEE Std 141 standards for generator fault current calculations. All currents are symmetrical RMS values unless otherwise noted.
| Step | Formula | Description |
|---|---|---|
| 1 | Ibase = S / (√3 × V) |
Base three-phase current (A). S = generator rating (VA), V = voltage (V) |
| 2 | xd_sub_pu = X"d / 100 |
Convert sub-transient reactance to per-unit |
| 3 | I"k = Ibase / xd_sub_pu |
Sub-transient fault current (A) |
| 4 | I'k = Ibase / (X'd / 100) |
Transient fault current (A) |
| 5 | Ik = Ibase / (Xd / 100) |
Steady-state fault current (A) |
| 6 | κ = 1.02 + 0.98 × e^(-3/X:R) |
Decay factor for asymmetrical current (X/R = X/R ratio) |
| 7 | Ip = √2 × κ × I"k |
Peak (asymmetrical) fault current (A) |
| 8 | Irated = S / (√3 × V × pf) |
Generator rated current (A), pf = power factor |