Ground-Fault Loop Current Estimator
Estimate current from source voltage and the total resistance and reactance of a supported grounded fault loop.
Enter source and return-path impedance
Include the outgoing path and grounded return path through the fault point.
Ground-fault loop current
About this estimator
Enter source voltage to ground and the resistance and reactance for both the source and complete fault-loop path. The estimator reports a symmetrical current magnitude based on the entered series impedance.
Use source and conductor values for the actual system state and fault location.
Method and assumptions
Total resistance and reactance are the respective sums of source and loop values. Impedance magnitude = √(R² + X²). Estimated current = source voltage to ground ÷ impedance magnitude.
The model assumes a single series loop and does not calculate parallel return paths, arcing faults, protective-device time, or transient current.
FAQs
What belongs in fault-loop impedance?
Include source impedance and the complete outgoing and grounded return paths through the fault point. Use values that represent the same system configuration.
Does the result show that a breaker will trip?
No. Protective-device operation depends on its time-current characteristics and actual fault conditions. This calculator only estimates current from entered impedance.
Sources
Use a qualified short-circuit or grounding study and conductor/manufacturer data for the system and fault location being evaluated.