Power System - II (3150911) MCQs

MCQs of Symmetrical Components

Showing 11 to 20 out of 33 Questions
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11.
The reactance of a generator designated X" is given as 0.25 pu based on the generator’s name plate rating of 18 kV, 500 MVA. If the base for calculations is changed to 20 kV, 100 MVA, the generator reactance X" on new base will be
(a) 1.025 pu
(b) 0.05 pu
(c) 0.0405 pu
(d) 0.25 pu
Answer:

Option (c)

12.
For a given base voltage and base volt amperes, the per unit impedance value of an element is X. The per unit impedance value of this element when the voltage and volt amperes bases are both doubled will be
(a) 0.5X
(b) X
(c) 2X
(d) 4X
Answer:

Option (a)

13.
For the fault analysis in power system, symmetrical components are used because
(a) Results are required in terms of symmetrical components
(b) Number of equations becomes smaller
(c) Sequence network do not have mutual coupling
(d) All of above
Answer:

Option (c)

14.
For a power transformer
(a) Positive sequence impedance is more than negative sequence and zero sequence impedance
(b) Positive, negative and zero sequence impedances are equal
(c) Positive and negative sequence impedances are equal
(d) Positive sequence impedance is less
Answer:

Option (b)

15.
For measuring positive, negative and zero sequence voltages in a system, the reference is taken as
(a) Neutral of the system only
(b) Ground only
(c) For zero sequence neutral and for positive and negative the ground
(d) None of the above
Answer:

Option (d)

16.
The positive sequence component of voltage at the point of fault is zero when it is a
(a) 3-phase fault
(b) L-L fault
(c) L-L-G fault
(d) L-G fault
Answer:

Option (a)

17.
Zero sequence currents can flow from a line into a transformer bank if the windings are in
(a) Grounded star/delta
(b) Delta/star
(c) Star/grounded star
(d) Delta/delta
Answer:

Option (a)

18.
Which of the following faults occurs most frequently
(a) 3-phase fault
(b) L-L-G fault
(c) L-L fault
(d) L-G fault
Answer:

Option (d)

19.
If Xs is self-reactance of each line and Xm is mutual reactance of any line pair then positive sequence impedance of transmission line is equal to
(a) j(Xs + Xm)
(b) j(Xs - Xm)
(c) jXs
(d) -jXm
Answer:

Option (b)

20.
For fully transposed transmission line
(a) Equal positive and negative sequence impedance
(b) Zero sequence impedance much larger than positive sequence impedance
(c) Both (a) and (b)
(d) None of the above
Answer:

Option (c)

Showing 11 to 20 out of 33 Questions
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