GIEE Per-Unit Calculator – GIEE – The Global Institute of Electrical Engineering

Per-Unit Calculator

Base quantities · R / X / Z base conversion · quick fault level

System

Base apparent power S_base

MVA

Base voltage V_base (line-to-line)

Base current, I_base—

Base impedance, Z_base—

What are you converting?

Resistance R

Reactance X

Values are given in

Given base — S_given

MVA

Given base — V_given

New base — S_new

MVA

New base — V_new

On new base	pu	%	Ω
R	—	—	—
X	—	—	—
\|Z\|	—	—	—

X / R ratio—

Impedance angle—

Total reactance to fault, X_total

Total resistance R_total (optional)

Prefault voltage

Base apparent power S_base

MVA

Base voltage V_base (line-to-line)

Fault current—

Fault level (MVA)—

Fault current (actual)—

X / R ratio—

Assumes a balanced three-phase system with V_base line-to-line. Base conversion scales R and X by the same factor. Quick fault level uses a Thevenin impedance for planning-level estimates; X/R drives the asymmetric peak, while the figures shown are symmetric rms.

Disclaimer. This calculator is provided by GIEE for educational and preliminary planning purposes only. Results are estimates based on simplified assumptions and are not a substitute for a complete engineering study. Verify all values against the applicable standards (IEEE, IEC, ANSI) and your specific project conditions before relying on them in design or operational decisions. GIEE accepts no liability for actions taken on the basis of these results.

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