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Prospective Fault Current Calculator

Calculate prospective fault current from supply voltage and external earth fault loop impedance Ze.

Estimator only. Verify measured values, supply characteristics and local requirements before using results on real electrical work.

Notes and next steps

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How it works

Calculate prospective fault current from nominal voltage and Ze.

Formula used: PFC = voltage ÷ Ze. kA = amps ÷ 1000.

Worked example

230 V ÷ 0.35 Ω = 657 A, or 0.66 kA.

Common mistakes
  • Using an assumed Ze without checking.
  • Confusing PSCC, PEFC and the highest prospective fault current.
  • Recording an estimate where a measured value is required.
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