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Protective Earth Size from Active Conductor and Fault Duty

Combine a user-entered active-to-earth sizing ratio with an adiabatic fault-duty minimum for a protective conductor.

Inputs

Project inputs and assumptions

Range: 0.01–100,000 mm²

Enter the active conductor area used by the selected sizing method and installation arrangement.

Range: 0–1,000 %

Enter the ratio selected from the applicable method; this is user-supplied and no Australian ratio table is embedded.

Range: 0–100,000,000 A

Enter the RMS fault current basis for the PE duty and fault path under review.

Range: 0.0001–100,000 s

Enter total protective-device clearing time for the fault case, including the selected protection basis.

Range: 0.01–100,000 A√s/mm²

Enter the k value for the actual conductor, insulation, initial/final temperature and installation basis.

Range: 0.01–100,000 mm²

Enter the proposed PE area to compare with the governing entered minimum.

Range: 0–100,000 mm²

Enter the applicable mechanical minimum, or zero only when that requirement is handled separately.

Result

Adiabatic minimum (mm²)
38.89
Ratio-based minimum (mm²)
8.00
Governing entered minimum (mm²)
38.89
Selected PE margin (mm²)
-28.89
Result
The selected PE area is below the largest entered ratio, adiabatic or mechanical minimum. Review the fault duty, k basis and conductor selection.

Formula

Calculation logic

Formula definitions and substituted values.

Before relying on the result

  • Screen a PE size against active-conductor ratio and fault energy
  • Show which of two minimums governs the selected PE
  • Use the applicable AS/NZS 3000 sizing method, mechanical minimums and verified k coefficient; this calculator exposes entered assumptions only.

Related calculators

Use the applicable AS/NZS 3000 sizing method, mechanical minimums and verified k coefficient; this calculator exposes entered assumptions only.