Maximum short-circuit current
Description
This tool calculates the maximum short-circuit current (kA) at the end of a low-voltage circuit, which is essential for selecting protective devices, coordinating protection schemes, and assessing arc flash hazards.
Applications
- Circuit breaker selection: Ensure breaking capacity ≥ end-of-line short-circuit current
- Protection coordination: Prevent nuisance tripping between upstream and downstream devices
- Arc flash risk assessment: Determine if arc-resistant equipment is required
- Conductor thermal stability: Verify cables can withstand short-circuit heating
Calculation Principles
The maximum short-circuit current depends on:
- Available short-circuit current at source (kA)
- System voltage (V)
- Line length (m/ft/yd)
- Conductor material (Copper/Aluminum)
- Conductor cross-section (mm² or AWG)
- Cable type (Unipolar/Multicore)
- Type of fault (3-phase, phase-to-phase, phase-to-earth)
Longer lines, smaller cross-sections, or higher resistivity materials result in lower short-circuit currents at the load end.
Typical Input Values
- Source short-circuit current: 10 kA
- System voltage: 220 V / 400 V
- Conductor: Copper, 1.5 mm²
- Line length: 10 meters
- Fault type: Phase-to-earth
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