Prospective Fault Current (Ipf)
Compute Ipf in kA from nominal voltage and earth fault loop impedance. Used to verify OCPD breaking capacity per BS 7671 Section 434.
Enter voltage and Zs to calculate Ipf.
The PDF is a calculation record, not a certificate — it carries no declaration and no signature.
Method and standard
Formula
Ipf (kA) = (V ÷ Zs) ÷ 1000. For UK single-phase, nominal voltage defaults to 230 V.
Why it matters
The protective device must have a rated breaking capacity equal to or greater than the prospective fault current at its terminals. A 6 kA MCB on a circuit with 8 kA Ipf can fail catastrophically under fault. BS 7671 Section 434 requires this check.
Used in
Method
Ipf (kA) = (V ÷ Zs) ÷ 1000
Reference
BS 7671:2018+A2:2022, Section 434
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