Fault Current (Isc) Calculator
Available fault current at a transformer's secondary terminals by the infinite-bus method, carried downstream to any point by the point-to-point method, then checked against a device's interrupting or withstand rating.
What it calculates
- Secondary fault current (Isca) from transformer kVA, secondary voltage and %Z
- Point-to-point fault current at the end of a conductor run, given the fault current available at its start
- Whether a device's rating is adequate for the available fault current at that point
Typical inputs
- Transformer kVA, secondary voltage, %Z
- Conductor length, size/material (via the C-value), and number of parallel runs
- The device's interrupting or withstand rating to check
Frequently asked
Why does fault current get smaller further from the transformer?
Every foot of conductor adds impedance, which reduces the current a fault can draw — the point-to-point method carries this reduction downstream from a known starting fault current, one conductor run at a time.
Autodesk and Revit are registered trademarks of Autodesk, Inc. SYMATEQ is not affiliated with, endorsed by, or sponsored by Autodesk, Inc. SYMATEQ Electrical Calculators is an independent add-in for Autodesk® Revit®. Calculations are engineering aids and do not replace review by a licensed professional engineer or confirmation with the authority having jurisdiction.