Research — Illustrative (draft, unvalidated)
Fault current along a feeder
Pick how strong the utility source is, then drag the fault point out along the feeder. The function adds the source and line impedance for each sequence network and returns the bolted fault current for all three fault types. Single line-to-ground starts as high as three-phase at the bus and falls fastest, because the line's zero-sequence impedance is several times its positive-sequence.
Feeder one-line and fault current bars (illustrative feeder, not site data)
Utility source strength · three-phase fault duty
Fault location
Fault type shown in the panel
Fault current status
Fault current
Loop impedance
X/R ratio
How the check read it
Client-side port:the logic and table in this page are a TypeScript port of the harness function, checked against values exported from the Python tests. Not a live API call. Module maturity, quoted from the domain page: “Draft; outputs should not feed compliance decisions until reviewed. Only conductor ampacity and the transformer hottest-spot function are anchored to an independent published reference; the grounding decrement and surface-layer factors each match one published point. Everything else is tested for internal self-consistency only.” Fault current is in the second group: the harness tests it for internal self-consistency against hand-derived symmetrical-components arithmetic only, with no independent published benchmark. The port here is checked against values exported from the Python function, which proves the port matches the Python, not that either matches a real system. Results are symmetrical RMS with no DC-offset factor.Real functions this maps to:
calculate_available_fault_current, source_impedance_from_fault_mva, calculate_line_constants.Not modeled: double line-to-ground faults (not implemented in the harness), fault resistance (all faults are bolted), motor contribution, transformers or other apparatus in the path, load, and X/R-dependent asymmetry. Illustrative choices made by this page, not harness defaults: the source zero-sequence impedance is set equal to its positive-sequence impedance (the harness has no default for Z0) and the source X/R is 10, the value the harness test uses. Feeder impedance per mile comes from the harness's calculate_line_constants for one conductor geometry (GMR 0.0244 ft, 0.306 Ω/mi, 4 ft spacing) and is not a particular utility's line.See also:Fault current, auto sweep · Conductor ampacity