Prospective short-circuit current workflow
A guide to preparing source impedance, transformer and breaking-capacity inputs before using the Australian short-circuit current calculator.
Source-current purpose
Prospective short-circuit current describes available current under entered source assumptions. It is useful for comparing source impedance, transformer shortcuts and breaking-capacity context, but it is not a device-selection service.
The calculator result should be stored with the source data that produced it.
Workflow
- Identify whether source impedance or transformer data is the stronger input path.
- Record the voltage basis and source location.
- Enter source impedance or transformer kVA and percent impedance.
- Record any entered comparison rating separately.
- Carry the result into device, cable withstand or engineering review.
Source-data record
| Field | Record | Review concern |
|---|---|---|
| Source location | Point in the installation being assessed | Current changes by location |
| Voltage basis | Entered system voltage | Percent and current depend on voltage |
| Impedance source | Utility, design, transformer or measured basis | Weak source weakens result |
| Transformer data | kVA and percent impedance where used | Must match the transformer reviewed |
| Device comparison | Entered breaking-capacity context | Does not replace manufacturer review |
Reading the result
If the calculated current approaches an entered device rating, stop and review source data, device rating, installation location and manufacturer information. Do not treat a margin value as proof of suitability.
If the result is unexpectedly high or low, check whether source impedance, transformer percent impedance or voltage basis was entered for the correct location.
Boundaries
- Do not use prospective current alone to select protective devices.
- Do not mix transformer data from another source.
- Do not hide the location where the current applies.
- Do not skip manufacturer data when ratings, let-through or coordination matter.