⚡ Engineering Tool

Short Circuit Calculator

Calculate prospective short circuit current and verify cable thermal withstand capacity. Ensure cables survive fault conditions without insulation damage or conductor failure.

📐 Standard: IEC 60909 / IEC 60364-4-43 🔥 Thermal: Adiabatic heating model ⚡ Check: I²t ≤ k²S²

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Input Parameters

Calculation Mode

System Voltage (Un)

Source Impedance (Zs) mΩ

Transformer + upstream impedance. Typical LV: 20–80 mΩ

Must be a positive number

Cable Cross-Section mm²

Conductor Material

Insulation Type

Cable Length (L) m

Must be a positive number

Fault Clearance Time (t) s

Typical: 0.1s (HV), 0.4s (LV MCB), 1.0s (LV fuse)

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Calculation Results

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Enter parameters above and click Calculate

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Thermal Withstand by Cable Size

Maximum fault current each cable size can withstand for the specified fault duration.

Size (mm²)	Max I_sc (kA)	k²S² (A²s)	Withstand

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Assumptions & Notes

Input Summary

Voltage—

Source Impedance—

Cable Size—

Conductor—

Length—

Fault Time—

Engineering Notes

⚠️ Thermal withstand condition: I²sc × t ≤ k² × S². Where k is the material constant (143 Cu/XLPE, 115 Cu/PVC, 94 Al/XLPE, 76 Al/PVC).

📌 Short circuit current calculation uses IEC 60909 simplified method: Isc = c × Un / (√3 × Ztotal), where c = 1.05 (LV) or 1.1 (MV).

Related Calculators

→ Cable Sizing Calculator → Ampacity Calculator