Fault Level (PSCC) Calculator
Estimate the prospective short-circuit current at a board from the transformer (or a known supply fault level), add a downstream cable run, and check it against a protective device's breaking capacity. An indicative first-pass to BS 7671 / IEC 60909 — not a full network study.
Indicative single-source method — verify the transformer impedance and device Icn against real data before issue.
This calculator uses a simplified single-source impedance method (Ip = U/(√3·Z)) and an indicative cable reactance — it is a feasibility aid, not a full IEC 60909 fault study with motor contribution and voltage factors. Confirm the transformer/source impedance and the device breaking capacity before relying on the result.
Why Fault Level Matters
Every protective device has a rated breaking capacity (Icn) — the fault current it can safely interrupt. If the prospective short-circuit current at the board exceeds it, the device can fail catastrophically under fault. This tool gives the quick three-phase estimate at the origin and, with a cable run added, the reduced fault level downstream. For the audited, whole-network fault study to BS EN 60909, see our ProDesign cable & protection service, or read how prospective fault current works.