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Fault-loop max length calculator
Maximum circuit length for B, C and D curve breakers.
Fault-loop maximum length
- Maximum circuit length
- 51.1 m
- With a 90% design margin
- 46 m
Method
- Lmax = 0.8 × Uo × Sph × Spe ÷ (ρ × Ia × (Sph + Spe))
- Uo = 230 V, ρ = 0.0225 Ω·mm²/m, Ia = 10 × 20 A (C curve)
- Sph = 2.5 mm², Spe = 2.5 mm² (earth in standard TPS / multicore)
Reference
- AS/NZS 3000 Appendix B, Table B1 method (0.4 s disconnection)
Notes
- Assumes the earth size in standard cable shown above. Test Zs at the far end of the circuit.
Verify against the current standard before relying on this.
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