Admissible let-through energy of the cable(K²S²)

Conductor *

Wire size *

Type *

Insulation *

Description

This tool calculates the maximum admissible let-through energy (I²t) that a cable can withstand under short-circuit conditions, based on IEC 60364-4-43 and IEC 60364-5-54 standards. It ensures that protective devices (e.g., circuit breakers or fuses) interrupt fault currents before the conductor overheats and damages insulation.

Input Parameters

Conductor Type: Phase conductor, single-core protective conductor (PE), or multi-core cable's protective conductor (PE)
Wire Size (mm²): Cross-sectional area of the conductor, affecting thermal capacity
Conductor Material: Copper (Cu) or Aluminum (Al), influencing resistivity and heat generation
Insulation Type:
- Thermoplastic (PVC)
- Thermosetting (XLPE or EPR)
- Mineral thermoplastic (PVC) covered
- Mineral bare sheath or bare conductor (not exposed to touch, restricted area)
- Mineral bare sheath or bare conductor (exposed to touch, normal conditions)
- Mineral bare sheath or bare conductor (fire risk environment)
- Mineral with metallic sheath used as protective conductor

Output Results

Admissible let-through energy (kA²s) — maximum tolerable I²t value
Reference standard clauses: IEC 60364-4-43 and IEC 60364-5-54
Compliance check: whether the calculated I²t is less than the protection device’s I²t characteristic

Designed for electrical designers and installers to verify short-circuit thermal stability of cables and ensure safe operation during faults.

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