From Handbook of Electric Power Calculations, Third Edition

Omar S.Mazzoni, Ph.D., P.E.

President
Systems Research International, Inc.

Marco W.Migliaro, P.E., Fellow IEEE

Chief Electrical and I&C Engineer
Florida Power & Light
Nuclear Division

PER-UNIT BASE QUANTITIES

Calculate the per-unit (p.u.) base quantities for a 150-MVA, 13.8-kV, 60-Hz, three-phase, two-pole synchronous, machine that has the following constants: d-axis mutual inductance between rotor and stator, L ad=0.0056 H; d-axis mutual inductance between stator winding a and rotor, L afd=0.0138 H; mutual inductance between stator winding a and d-axis amortisseur, L akd=0.0054 H; q-axis mutual inductance between rotor and stator, L aq=0.0058 H; and mutual inductance between stator winding a and q-axis amortisseur, amortisseur, L akq=0.0063 H. The per-unit system used should be the reciprocal mutual per-unit system. This denotes a per-unit system where the per-unit mutual inductances between the rotor and stator circuits are reciprocal. This also implies that ( Note: The bar over symbol denotes a per-unit value.)

Calculation Procedure

1. Select Base Values

Select VA base=150 MVA, V base=13.8 kV, and base=60 Hz. From these values, other base quantities may be derived.

2. Calculate rms Stator Phase Current Base, I s(base)

3. Calculate Peak Stator Phase Current Base, i s(base)

The current is

4. Calculate Stator Base Impedance, Z s(base)

5. Calculate Stator Base Inductance, L s(base)

L s(base)= Z s(base)/ ? base=1.270/377=3.37 10 ?3 H.

6. Calculate Field Base Current, i d(base)

The current is

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