Prospective short-circuit current in Australia
How PSCC is read in Australian protection work, including source impedance, transformer data, kA values and breaking-capacity checks.
What PSCC Means
Prospective short-circuit current, often shortened to PSCC, is the current that could flow under a short-circuit condition at a point in an electrical system. In Australian low-voltage work it is usually handled in kA, with the location and source basis kept beside the value.
The value can come from DNSP information, project models, transformer data, source impedance or an engineering calculation. A PSCC value is not portable across a site unless the supply path and calculation point are the same.
Source Impedance And Transformer Inputs
Two common calculator inputs are source impedance and transformer percent impedance.
- Source-impedance mode uses
I = V / Zfor single-phase, orI = V / (sqrt(3) x Z)for a balanced three-phase line-to-line basis. - Transformer mode estimates full-load current from
kVA x 1000 / (sqrt(3) x V), then multiplies by100 / transformer %Z. - The result is converted from amps to kA for breaking-capacity and switchboard comparisons.
| Input | Typical use | Why it matters |
|---|---|---|
| Calculation point | Main switchboard, distribution board, equipment terminals or incoming supply location in the project model. | Fault current changes with location and upstream impedance. |
| Source impedance | Entered ohm value for the selected voltage and phase basis. | Lower impedance gives higher prospective current. |
| Transformer kVA and %Z | Common shortcut when transformer data is the source. | Full-load current and percent impedance drive the estimate. |
| Voltage basis | 230 V single-phase or 400 V three-phase where appropriate. | The formula changes with phase arrangement. |
| Device comparison | Entered breaking capacity in kA. | This is a screening comparison, not a device approval. |
Worked 400 V Example
A three-phase 400 V source-impedance estimate with Z = 0.02 ohm gives:
I = 400 / (sqrt(3) x 0.02) = 11547 A, or about 11.55 kA.
If the entered device breaking capacity is 25 kA, the worksheet margin is about 13.45 kA and the utilisation is about 46%. That comparison still needs the actual switchboard location, product data and project review.
| Field | Example entry | Reading |
|---|---|---|
| Location | Main switchboard incoming section. | PSCC belongs to the point being reviewed. |
| Source basis | 400 V three-phase, 0.02 ohm source impedance. | The calculation can be reviewed later. |
| Result | 11.55 kA prospective short-circuit current. | Downstream comparisons use kA. |
| Device comparison | 25 kA entered breaking capacity. | Product data and conditions still control the real suitability question. |
Where PSCC Is Used
PSCC feeds breaking-capacity checks, switchboard fault-level notes, coordination discussions and cable withstand review. The same value can also sit near fault-loop or earth-fault work, but those are not the same calculation.
Keep the DNSP, transformer label, project model, source impedance or manufacturer source close to the value. When the value moves into a protective-device comparison, the location and source basis should move with it.
Next checks
- Use the short-circuit current calculator when the source impedance or transformer kVA and %Z are known.
- Use the breaking-capacity page or protection device terms when the next question is device fault-interruption rating.
- Use I2t cable withstand only after the fault-current point, clearing time and conductor data are ready.
Boundaries
- This page does not select a protective device or approve coordination.
- It does not replace DNSP data, transformer data, manufacturer ratings or switchboard documentation.
- Current standards context, supply data, equipment ratings, project requirements and competent engineering review remain controlling inputs.
Prospective short-circuit current in Australia in Australian work
Explain prospective short-circuit current so source data, location, kA units and downstream protection checks stay connected. The useful record is not just the final number or definition; it is the combination of the entered value, the supply arrangement, the equipment or circuit reference and the decision that still needs project review.
Help users understand prospective short-circuit current in Australian protection work before comparing fault level, breaking capacity and cable withstand data. Keep the wording in Australian English, use metric units, and treat 230/400 V a.c. at 50 Hz as the ordinary low-voltage context unless the project information states a different value.
Checks that belong beside this page
- Regional scopeAustralia; public protection calculator terminology.
- Standards contextAustralian protection and Wiring Rules context; current project, supply data, equipment data and engineering review remain controlling sources.
- Review timingReview cadence: Annual protection wording review or sooner if short-circuit calculator or guide wording changes.. Update trigger: Update when short-circuit calculator inputs, fault-current chart rows or protection guide wording changes.
Practical use sequence
For Prospective short-circuit current in Australia, begin with the circuit, board, load, cable route, equipment item or measurement record named by this topic. Record the value basis, such as current, voltage, kW, kVA, route length, test value, product rating, tariff value or worksheet field, then note the review boundary so another person can see what this page explained and what still needs a project decision.
The strongest Prospective short-circuit current in Australia record is specific enough to be reviewed later. It names the Australian context, keeps the entered assumptions visible, separates calculation support from compliance decisions and shows where a calculator, table, chart or term definition should be opened next.
Record detail to capture
Keep the Prospective short-circuit current in Australia note attached to Australia; public protection calculator terminology.. When the page is used during design, estimating, testing, review or study work, write the entered assumption, the source that supplied it, the circuit or equipment label and the person or role that must review the following action.
For Prospective short-circuit current in Australia, the review cadence is Annual protection wording review or sooner if short-circuit calculator or guide wording changes. and the update trigger is Update when short-circuit calculator inputs, fault-current chart rows or protection guide wording changes.. If the topic connects to Protection device terms, open that page after the current definition, input basis or boundary has been recorded, so the next calculation inherits the right Australian context.
A complete Prospective short-circuit current in Australia record leaves four facts visible: why the page was opened, which Australian supply or equipment context applies, which value remains user-entered and what later change would alter the result. That makes the page useful as a working note instead of a loose reference copied away from the project evidence.
- InputsWrite down the entered values and their units before comparing results across calculators or reference pages.
- LocationKeep the value tied to the board, circuit, cable run, equipment terminal, supply point or worksheet row it describes.
- Authority checkCompare the record with current Australian requirements, DNSP or local authority conditions and product information.
- Review trailRetain the date, edition context and reason for the calculation so later changes can be traced.
Connected AUWiring pages
Use the related pages for Prospective short-circuit current in Australia when the topic needs a calculator input, lookup table, formula chart or supporting term before the project record is complete. Open Protection device terms first when that page owns the next value or definition.
- Protection device termsDevice terms used beside fault-current checks.
- Testing record fieldsFields for measured and entered protection worksheets.
- Fault-current relationshipVoltage, impedance and fault-current relationship chart.
- Short-circuit currentReview entered source impedance or transformer data.