Radial feeder fault current
Estimate a downstream three-phase fault using explicit source and conductor impedances.
Enable JavaScript for live calculations. Read the method and default example below.
Method and assumptions
- Rt = Rs + r × one-way length / 1000; Xt = Xs + x × one-way length / 1000.
- Isc = line voltage / (√3 × √(Rt² + Xt²)).
Before using the result
- Radial three-phase model only. Motor, generator and parallel-source contributions are excluded. Check source data and conductor temperature.
- Earth faults, peak withstand, minimum fault operation and protection coordination require separate verification.
Worked example
Illustrative default inputs. Enter your project values above.
- Line-to-line voltage
- 415 V
- Source resistance per phase
- 0.002 Ω
- Source reactance per phase
- 0.01 Ω
- One-way feeder length
- 100 m
- Conductor resistance at assessment temperature
- 0.2 Ω/km
- Conductor reactance
- 0.08 Ω/km
Default results
- Total resistance per phase
- 0.022 Ω
- Total reactance per phase
- 0.018 Ω
- Three-phase fault current
- 8.429 kA
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Technical references
These references support planning. The exact model documentation and a project-specific engineering review govern the final specification.