Fault loop impedance

Fault-loop impedance in records

Fault loop impedance is the impedance of the fault path used when an Australian protection or testing record needs to relate a voltage basis to an estimated fault current. The record usually needs the circuit, board, earthing path and measurement or source basis kept together.

In AUWiring pages the term appears near MEN, earthing, protective conductor and RCD/RCBO testing context. It describes a value in the record, not a complete verification result by itself.

Measurement or source context

Fault-loop records become useful only when the source of the value is visible. A measured value, a design value and a copied assumption do not carry the same weight.

Relationship to fault current

Fault loop impedance is often used with the voltage basis to estimate fault current. A lower loop impedance can produce a higher calculated current, but the interpretation still depends on the circuit, protective device, conditions and entered criteria.

That is why the term should not be shortened to a simple pass or fail label. AS/NZS 3017-style verification context, project requirements and qualified testing remain outside this glossary definition.

Using loop impedance values

Use the fault-loop impedance calculator for entered impedance and voltage values. Use testing record fields when the job needs the measurement context, device reference and review basis recorded before the result is carried into another protection page.