Chapter 7: Q10MCQ (page 463)
Before proceeding with per-unit fault current calculations, based on the single-line diagram of the power system, a positive-sequence equivalent circuit is set up on a chosen base system.
(a) True
(b) False
Therefore, the correct option is (a) True.
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The reactance that plays a role under steady-state operation of a synchronous machine is called _____.
Solve Example 7.3 parts (a) and (c) without using the superposition principle. First calculate the internal machine voltages and localid="1656758482853" using the prefault load current. Then determine the subtransient fault, generator, and motor currents directly from Figure 7.4(a). Compare your answers with those of Example 7.3.
The amplitude of the sinusoidal symmetrical ac component of the three-phase short-circuit current of an unloaded synchronous machine decreases from a high initial value to a lower steady-state value, going through the stages of _____ and _____ periods.
As shown in Figure 7.21, a, synchronous generator with is connected through a transformer to a bus that supplies four identical motors. The rating of the three-phase transformer is with a leakage reactance of. Each motor has a sub-transient reactance on a base of .A three-phase fault occurs at point P, when the bus voltage at the motors is.
(a) the sub-transient fault current,
(b) the sub-transient current through breaker A, and
(c) the symmetrical short-circuit interrupting current (as defined for circuit breaker applications) in the fault and in breaker A.
For a power system, modelled by its positive-sequence network, both bus admittance matrix and bus-impedance matrix are symmetric.
(a) True
(b) False
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