Electrical Fault Current Calculator
ANA›Life Services Authority›National Calculator Authority›Electrical Fault Current Calculator
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Electrical Fault Current Calculator
Calculate symmetrical three-phase and single-phase-to-ground fault currents based on system voltage and source impedance.
System Voltage (V)
Source Resistance R (Ω)
Source Reactance X (Ω)
Fault Type
Three-Phase Symmetrical (3Φ) Single-Phase-to-Ground (1Φ-G)
Calculate
function eleCalc() { var resultDiv = document.getElementById('ele-result'); var V = parseFloat(document.getElementById('ele-voltage').value); var R = parseFloat(document.getElementById('ele-resistance').value); var X = parseFloat(document.getElementById('ele-reactance').value); var faultType = document.getElementById('ele-fault-type').value;
if (isNaN(V) || isNaN(R) || isNaN(X)) { resultDiv.innerHTML = 'Please enter valid numbers for all fields.'; return; } if (V System voltage must be greater than zero.'; return; } if (R Resistance and reactance must be non-negative.'; return; } var Z = Math.sqrt(R * R + X * X); if (Z === 0) { resultDiv.innerHTML = 'Impedance cannot be zero (infinite fault current is not physically realizable).'; return; }
var Isc, label, voltageUsed;
if (faultType === '3phase') { // I_sc3 = V_LL / (√3 × Z) var Vln = V / Math.sqrt(3); Isc = Vln / Z; label = 'Three-Phase Symmetrical Fault Current (Isc3)'; voltageUsed = 'VLN = VLL / √3 = ' + Vln.toFixed(2) + ' V'; } else { // I_sc1 = V_LN / Z (simplified, assumes zero-sequence Z equals positive-sequence Z) var Vln1 = V / Math.sqrt(3); Isc = Vln1 / Z; label = 'Single-Phase-to-Ground Fault Current (Isc1)'; voltageUsed = 'VLN = VLL / √3 = ' + Vln1.toFixed(2) + ' V'; }
var IscKA = Isc / 1000; var pf = (Z > 0) ? (R / Z) : 0; var angleRad = Math.atan2(X, R); var angleDeg = angleRad * (180 / Math.PI);
resultDiv.innerHTML = '' + label + '' + ' ' + voltageUsed + '' + ' Z = √(R² + X²) = √(' + R.toFixed(4) + '² + ' + X.toFixed(4) + '²) = ' + Z.toFixed(6) + ' Ω' + ' Power Factor (R/Z) = ' + pf.toFixed(4) + '' + ' Impedance Angle = ' + angleDeg.toFixed(2) + '°' + 'Isc = ' + Isc.toFixed(2) + ' A (' + IscKA.toFixed(3) + ' kA)'; }
#### Formulas
Three-Phase Symmetrical Fault: Isc3 = VLN / Z = (VLL / √3) / √(R² + X²)
Single-Phase-to-Ground Fault (simplified): Isc1 = VLN / Z = (VLL / √3) / √(R² + X²)
Total Impedance Magnitude: Z = √(R² + X²)
Where: VLL = line-to-line voltage (V), R = resistance (Ω), X = reactance (Ω)
#### Assumptions & References
- The three-phase fault formula uses the Thevenin equivalent: Isc = VLN / Z (IEEE Std 141 / Red Book).
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