Line against phase, wye against delta, the power triangle, per unit, and symmetrical fault current, each checked against a published worked example.
Educational. Not for field use. This reproduces published worked
examples so they can be explored interactively. It does not tell you whether your gear is rated for a
fault, and it is not a substitute for an engineered study, the manufacturer's instructions, or a
qualified person on site.
Why this exists. A field tech who can reproduce the book's numbers
by hand, and show the work, reads a one-line and a short-circuit study differently. Every
number below traces to a page, and the tool refuses to compute the things the book does not publish.
1 Line vs phase, and the power triangle
Balanced load
Presets reproduce the book with its own root three (1.73). Free-form entry computes
at full precision.
DOE-HDBK-1011/3-92, ES-09 “Basic AC Power”, Rev 0
(public domain, U.S. Department of Energy, read at energy.gov). Eqs 9-5 through 9-11, Examples 1 and 2.
2 Per unit and symmetrical fault current
Fault = I_base ÷ Z_pu
What this will not do. It will not reduce a one-line to that
Z_pu. Combining a network of impedances to one Thevenin per-unit value is the engineered
short-circuit study, and a wrong Z_pu makes the fault current wrong. Supply a Z_pu from a study,
or use the published example's reduced values.
TM 5-811-14, Appendix G, Example 5
Base 2000 kVA; base kV 12.47 / 4.16 / 0.480. Per-unit conversion
lines (published input → published pu):
TM 5-811-14, “Coordinated Power Systems Protection” (US Army),
App G, Example 5, G-27 to G-29. Read at a mirror; App G is outside the manual's
one IEEE-242 reprint (p4-3) and is U.S. Army Corps of Engineers public-domain content. See
sources/SOURCES.md.
Source of truth for this tool's status is
PROGRESS.log. Verify with node verify/verify.js.