Earth fault loop impedance workflow
How to prepare loop impedance, voltage and entered review thresholds before using the Australian fault-loop impedance calculator.
Record purpose
Earth fault loop impedance work should leave a traceable test or design record. The calculator can convert entered loop impedance and voltage into a fault-current estimate, but it cannot know the protective-device curve, test conditions or final verification requirement unless the reviewer supplies them.
The record should show where the impedance came from, which voltage basis was used and what entered threshold was being compared.
Workflow
- Identify the board, circuit, device and test point.
- Record whether the impedance is measured, designed or assumed.
- Enter the voltage basis used for the calculation.
- Enter the loop impedance value and any reviewer threshold.
- Keep the protective-device data source and instrument record with the result.
- Use the result as a worksheet value before final verification.
Loop impedance record
| Field | Strong record | Weak record |
|---|---|---|
| Test point | Board, circuit and device label | Unnamed point |
| Loop impedance | Measured value or reviewed design value | Copied value with no source |
| Voltage basis | Entered voltage used for the formula | Hidden nominal assumption |
| Device context | Protective device type and data source | Generic breaker label |
| Instrument record | Instrument, date and condition note | No test source |
| Threshold basis | Reviewer-entered criterion | Hard-coded pass language |
Reading the result
The calculated current is a relationship value. If the review state is weak, look first at the impedance source, voltage basis, device data and threshold basis. Do not repair the result by changing only one input without checking the record.
When device data matters, move to manufacturer information or engineering review rather than treating the public calculator as a final verification tool.
Boundaries
- Do not publish fixed universal pass/fail thresholds.
- Do not ignore protective-device data.
- Do not separate measured values from instrument records.
- Do not treat calculated fault current as a complete verification result.