L-L
Isc = (0.8 * U * SL) / (1.5 * ρ * 2 * L)
L-N
Isc = (0.8 * U * SL) / (√3 * 1.5 * ρ * (SL/SN + 1) * L)
Where：
Isc = Minimum short – circuit current (A)
U = Concatenated voltage [L – L] (V)
S = Wire size (mm²)
ρ = Resistivity(Ω mm²/m)
L = Length (m)
Calculates the minimum short-circuit current at the end of a low-voltage circuit, used to verify protective device sensitivity.
Supports:
Single-phase, two-phase, three-phase systems
Copper/Aluminum conductors
mm²/AWG units
m/ft/yd length units
Parallel conductors
Isc,min = U / (√3 × (RL + XL))
Where:
U: System voltage
RL: Line resistance
XL: Line reactance
Current type: Three-phase
Voltage: 400 V
Length: 50 m
Conductor: Copper, 16 mm²
→ Minimum short-circuit current ≈ 8.5 kA
Copper has a lower resistivity than aluminum, resulting in lower resistance for the same cross-sectional area and length, and therefore lower I²R losses.
This electrical design tool is engineered for power systems professionals and students, including:
Electrical Protection & Design Engineers: For verifying protective device selectivity, tripping sensitivity, and cable lengths in industrial and commercial projects.
Commissioning & Maintenance Technicians: To investigate persistent breaker trip failures, verify thermal safety during field retrofits, and conduct fault audits.
MEP Consultants & Code Compliance Auditors: To ensure electrical designs comply with IEC 60364, NFPA 70 (NEC), and local electrical safety regulations.
Electrical Engineering Students: For understanding loop impedance concepts, short-circuit temperature dependency, and protective coordination math.
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