Chapter 7: Q11MCQ (page 463)
The inverse of the bus-admittance matrix is called a _____ matrix.
The inverse of the bus-admittance matrix is called a bus impedance matrix.
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Recalculate the sub transient current through the breaker in Problem 7.6 if the generator is initially delivering rated MVA at 0.8 pf lagging and at rated terminal voltage.
For a power system, modelled by its positive-sequence network, both bus admittance matrix and bus-impedance matrix are symmetric.
(a) True
(b) False
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.
A single-line diagram of a four-bus system is shown in Figure 7.20, for whichis given below:
Let a three-phase fault occur at bus 2 of the network.
(a) Calculate the initial symmetrical rms current in the fault.
(b) Determine the voltages during the fault at buses 1, 3, and 4.
(c) Compute the fault currents contributed to bus 2 by the adjacent unfaulted buses 1, 3, and 4.
(d) Find the current flow in the line from bus 3 to bus 1. Assume the prefault voltage at bus 2 to belocalid="1655403112082" and neglect all prefault currents.
Breakers of the 115kV class and higher have a voltage range factor k = _____, such that their symmetrical interrupting current capability remains constant.
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