Multiple Choice Questions in Power Systems - 2

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Important multiple choice questions in Power systems

1.       The good effect of corona on overhead lines is to
A)     Increase the line carrying capacity due to conducting ionized air envelop around the conductor
B)      Increase the power factor due to corona loss
C)      Reduce the radio interference from the conductor
D)     Reduce the steepness of surge fronts

2.       The principal information obtained from load flow studies in a power system are
                                            I.            Magnitude and phase angle of the voltage at each bus
                                          II.            Reactive and real power flows in each of the lines
                                        III.            Total power loss in the network
                                        IV.            Transient stability limit of the system
Select the correct answer using the codes given below:
A)     1 and 2
B)      3 and 4
C)      1,2 and 3
D)     2 and 4

3.       Three generators rated 100 MVA, 11 kV have an impedance of 0.15 pu each. If in the same plant, these generators are being replaced by a single equivalent generator, the effective impedance of equivalent generator will be
A)     0.05 pu
B)      0.15 pu
C)      0.25 pu
D)     0.45 pu

4.       If all the sequence voltages at the fault point in a power system are equal, then the fault is a
A)     Three-phase fault
B)      Line to ground fault
C)      Line to line fault
D)     Double line to ground fault

5.       Which one of the following relays has the capability of anticipating the possible major fault in the transformer?
A)     Overcurrent relay
B)      Differential relay
C)      Buchholz  relay
D)     Overfluxing relay

6.       In a 220kV system, the inductance and capacitance up to the circuit breaker location are 25mH and 0.025µF respectively. The value of resistor required to be connected across the breaker contacts which will give no transient oscillations, is
A)     25Ω
B)      250Ω
C)      500Ω
D)     1000Ω

7.       The speed regulation parameter R of a control area is 0.025 HZ/MW and load frequency constant D is 2 MW/Hz. The area frequency response characteristics (AFRC) is
A)     42 MW/Hz
B)      40 MW/Hz
C)      20 MW/Hz
D)     2 MW/Hz

8.       In the HVDC system, the ac harmonics which gets effectively eliminated with 12 pulse bridge converters, are
A)     Triplen harmonics
B)      Triplen and fifth harmonics
C)      Triplen, fifth and seventh harmonics
D)     Fifth and seventh harmonics

9.       The per-unit impedance of a circuit element of 0.15. if the base kV and base MVA are halved, then the new value of the per-unit impedance of the circuit element will be
A)     0.075
B)      0.15
C)      0.30
D)     0.60

10.   The per-unit impedance of an alternator corresponding to base values 13.2 kV and 30 MVA is 0.2 pu. The p.u. value of the impedance for base values 13.8 kV and 50 MVA in p.u. will be
A)     0.131
B)      0.226
C)      0.305

D)     0.364

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