Fault Loop Impedance Calculator

How Fault Loop Impedance works

For this case, apply Zloop = V ÷ Itrip. Fault Loop Impedance uses Nominal voltage, Required trip current to report Maximum loop impedance.

With the loaded values, maximum loop impedance evaluates to 1.44 Ω. Compare low and high values without overwriting the starting case. Use Ground Electrode Resistance Calculator as the follow-up for estimated ground resistance.

Inputs for Fault Loop Impedance

Nominal voltage and Required trip current belong to Fault Loop Impedance. Keep source units with nominal voltage.

Defaults make the page immediately testable, but they do not describe a universal installation.

Nominal voltage

Example entry: 230 V.

Required trip current

Example entry: 160 A.

Reading the Fault Loop Impedance result

This output represents Fault Loop Impedance.

Apply required margins only after identifying the correct equipment standard.

Measurement and units

Treat these results as planning arithmetic; conductor and protective-device selection must follow the applicable electrical code and equipment instructions. Check prefixes on nominal voltage.

Record conversion choices so comparisons stay traceable.

Limits of this calculation

Verify disconnection requirements with the applicable protection standard.

Only variables shown in the equation affect the numerical output. Unentered effects remain outside Fault Loop Impedance.

A useful Fault Loop Impedance comparison

Record maximum loop impedance before testing a different nominal voltage value. If the next question concerns current per conductor, open Parallel Conductor Sharing Calculator.

Document the alternate nominal voltage source.

Questions about Fault Loop Impedance