Ground Fault Current Calculator
Estimate ground fault current magnitude from system voltage and ground path impedance.
277 V for 480Y/277, 120 V for 208Y/120
Total impedance of fault path
Ground Fault Current
461.7 A
Ground Fault Current vs System Voltage (Phase-to-Ground)
Ground Fault Current Estimation
Ground fault current flows when a live conductor contacts grounded metal. Its magnitude determines how quickly protection devices clear the fault.
Formula
I_gf = V_phase / (Z_ground + Z_source)
Touch Voltage = V_phase x Z_ground / (Z_ground + Z_source)
Low ground-path impedance ensures high fault current, which trips protective devices quickly. High impedance (poor grounding) results in low fault current that may not trip the breaker, leaving a dangerous condition.
Example Calculation
277 V phase-to-ground, 0.5 ohm ground path, 0.1 ohm source impedance.
- 01Ground fault current: 277 / (0.5 + 0.1) = 461.7 A
- 02Fault power: 277^2 / 0.6 = 127,882 W
- 03Touch voltage: 277 x 0.5 / 0.6 = 230.8 V (dangerous)
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