Power System - II (3150911) MCQs

MCQs of Unsymmetrical Fault Analysis

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1.
The positive, negative and zero sequence impedances of a solidly grounded system under steady state condition always follow the relations
(a) Z1 > Z2 > Z0
(b) Z1 < Z2 < Z0
(c) Z0 < Z1 < Z2
(d) None of the above
Answer:

Option (a)

2.
A shunt fault is characterized by
(a) Increase in current, frequency and power factor
(b) Increase in current reduction in frequency and power factor
(c) Increase in current and frequency but reduction in power factor
(d) None of the above
Answer:

Option (b)

3.
If Ia1 is the positive sequence current of an alternator and Z1, Z2 and Z0 are the sequence impedances of the alternator. The drop produced by the current Ia1 will be
(a) Ia1Z1
(b) Ia1 (Z1 + Z2)
(c) Ia1(Z1 + Z2 + Z0)
(d) Ia1(Z2 + Z0)
Answer:

Option (a)

4.
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)

5.
Tick out the correct statement
(a) The negative and zero Sequence voltages are maximum at the fault point and decrease towards the neutral
(b) The negative and zero sequence voltages are Minimum at the fault point and increase towards the neutral
(c) The negative sequence is maximum and zero sequence minimum at the fault point and decrease and increase respectively towards the neutral
(d) None of the above
Answer:

Option (a)

6.
If one phase of supply goes off in the case of 3-phase induction motor, the motor
(a) Comes to a stop
(b) Draws double the initial current and continues to run
(c) Draws 1 ∕√3 times the initial current and continues to run
(d) None of the above
Answer:

Option (d)

7.
A single line to ground fault occurs on an unloaded generator in phase a. If Xd = X2 = 0.25 pu, X0= 0.15 pu, reactance connected in the neutral, XN = 0.05 pu and the initial prefault voltage is 1.0 pu, then the magnitude of the fault current will be
(a) 3.75 pu
(b) 1.54 pu
(c) 1.43 pu
(d) 1.25 pu
Answer:

Option (a)

8.
When a line-to-ground fault occurs, the current in a faulted phase is 100 A. The zero sequence current in this case will be
(a) Zero
(b) 33.3 A
(c) 66.6 A
(d) 100 A
Answer:

Option (b)

9.
The following sequence currents were recorded in a power system under a fault condition Ipositive = j1.653 pu, Inegative = – j 0.5 pu, Izero = – j1.153 pu.The fault is
(a) Line to ground
(b) Three-phase
(c) Line to line to ground
(d) Line to line
Answer:

Option (c)

10.
A power system is subjected to a fault which makes the zero sequence component of current equal to zero. The nature of fault is
(a) Double line to ground fault
(b) Double line fault
(c) Line of ground fault
(d) Three-phase to ground fault
Answer:

Option (b)

Showing 1 to 10 out of 31 Questions
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