Short-Circuit Current at Panel (Point-to-Point)
I_sca at transformer secondary, M-factor, and let-through fault current via the Bussmann point-to-point method.
Example
You enter
- Utility transformer kVA 1500
- Utility transformer %Z 5.75
- Secondary V 480
- Phase three
- Conductor C-value (from shard) 22185
- Run length (ft) 100
- Parallel sets 1
You get
- I_sca at secondary 31379 A
- I_sca at panel 20776 A
Details, formula, and sources
I_sca_secondary = (kVA × 1000) / (V × √phases × Z%/100). f = (√3 × L × I_sca) / (n × C × V) for three-phase (use 2 instead of √3 for single-phase). M = 1 / (1 + f). I_sca_panel = I_sca_secondary × M.
Bussmann Point-to-Point Method (Eaton/Bussmann SPD electrical-safety publication) by name. C-values from Eaton/Bussmann published table.
Bussmann SPD documents free at eaton.com/bussmann-spd. Free read-only access at nfpa.org/freeaccess.
Estimate. AHJ and licensed electrician govern. Verify against the NEC edition adopted in your jurisdiction.
Field names used by the API: utility_kVA, utility_Z_pct, secondary_V, phase, C_value, length_ft, parallel_sets, I_sca_secondary_A, I_sca_panel_A
- C-value table data/electrical/conductor-c-values.json keyed to conductor class / size / racewayEaton/Bussmann SPD
- Three-phase factor √3 (use 2 for single-phase)Bussmann SPD