Wiring and Protection
Short-Circuit Current Calculator
Use Short-Circuit Current Calculator to calculate prospective fault current from source voltage and total fault impedance. Keep the entered conditions with the answer so later comparisons are fair.
Model Short-Circuit Current
The defaults only show how Short-Circuit Current works; replace them with values for the actual equipment or period.
The Short-Circuit Current equation
Read the Short-Circuit Current equation from the units on this page. A familiar symbol can shift meaning between DC, AC, energy, component, or billing work.
A clean Short-Circuit Current result confirms the arithmetic for prospective fault current; it does not prove the equipment rating or source data is the right one.
Only the entries shown on Short-Circuit Current feed prospective fault current. If another correction factor matters, keep it in the notes or make a separate run.
Sample Short-Circuit Current run
Using the sample values, Source voltage = 230 V; Total fault impedance = 0.35 Ω, the primary result is 657.14 A.
This Short-Circuit Current one-input test is a scale check, showing direction and sensitivity without turning the changed case into a recommendation.
If the changed source voltage comes from a real measurement, keep the original Short-Circuit Current run so the source of the difference remains clear.
Source notes for Short-Circuit Current
Treat the Short-Circuit Current input panel like a short measurement log. If source voltage is assumed rather than measured, label it before copying prospective fault current.
| Entry | Example | Check before use |
|---|---|---|
| Source voltage | 230 V | Enter source voltage in V. |
| Total fault impedance | 0.35 Ω | Enter total fault impedance in Ω. |
Use Fault Loop Impedance for that neighboring calculation rather than adding unstated assumptions here.
What not to assume from Short-Circuit Current
The protective device interrupting rating must exceed prospective current.
- Fault-current availability
- Bundling
- Voltage drop
When prospective fault current is close to a rating, use the stricter review path instead of relying on the extra decimals shown by Short-Circuit Current.
When your notes point to Continuous Load Capacity, open it after saving this baseline so the two cases do not get mixed.
Reading prospective fault current
If prospective fault current is near a limit, preserve the calculated value from Short-Circuit Current and apply required margin after the calculation.
Short-Circuit Current must stay connected to conductor material, installation method, ambient temperature, and code review.
Audit trail for prospective fault current
Keep conductor material, insulation temperature, raceway method, ambient temperature, and protective device type with Short-Circuit Current.
If a later Short-Circuit Current run changes only source voltage, label it as sensitivity work. Several changed conditions deserve a new baseline.
If the next step shifts toward Grounding Voltage Rise, keep that as a separate worksheet instead of forcing the numbers into Short-Circuit Current.