Line-to-ground fault occurs:

Due to the breakdown of insulation between two phases and simultaneous breakdown of insulation between the third phase and earth

Due to short circuit between two conductors

Due to insulation breakdown between one of the phase and earth

Due to the breakdown of insulation between two phases and simultaneous breakdown of insulation between the third phase and earth

Due to fault breakdowns of insulation between two phases and earth occur

In case of single line to ground fault

Positive and negative sequence networks are connected in parallel

All sequence networks are connected in parallel

All sequence networks are connected in series

Positive and negative sequence networks are connected in parallel

Zero and negative sequence networks are connected in series

Explore topic-wise MCQs in Power Systems.

This section includes 8 Mcqs, each offering curated multiple-choice questions to sharpen your Power Systems knowledge and support exam preparation. Choose a topic below to get started.

1.	Five alternators, each of which is rated for 10 MVA, 11 KV with 25% reactance, operate in parallel order. What will be the short circuit level in the bus bar?
A.	200 MVA
B.	50 MVA
C.	300 MVA
D.	100 MVA
Answer» B. 50 MVA

Discussion

2.	For a fault at the terminals of the synchronous generator, the fault current is maximum for a
A.	Three phase fault
B.	Three phase to ground fault
C.	Line to ground fault
D.	Line to line fault
Answer» D. Line to line fault

Discussion

3.	A 50 Hz, 4 Pole, 500 MVA, 22 kV turbo generator is delivering rated MVA at a power factor of 0.8. Suddenly a fault occurs reducing the electric power output by 40%. Neglect the losses and assume constant power input to the shaft. The accelerating torque in the generator at the time of fault is
A.	1.528 MNm
B.	1.018 MNm
C.	0.848 MNm
D.	0.509 MNm
Answer» C. 0.848 MNm

Discussion

4.	A lossless transmission line with 0.2 pu reactance per phase uniformly distributed along the length of the line, connecting a generator bus to a load bus, is protected up to 80 % of its length by a distance relay placed at the generator bus. The generator terminal voltage is 1 pu. There is no generation at the load bus. The threshold pu current for operation of the distance relay for a solid three phase-to-ground fault on the transmission line is closest to:
A.	1
B.	3.61
C.	5
D.	6.25
Answer» E.

Discussion

5.	Line-to-ground fault occurs:
A.	Due to short circuit between two conductors
B.	Due to insulation breakdown between one of the phase and earth
C.	Due to the breakdown of insulation between two phases and simultaneous breakdown of insulation between the third phase and earth
D.	Due to fault breakdowns of insulation between two phases and earth occur
Answer» C. Due to the breakdown of insulation between two phases and simultaneous breakdown of insulation between the third phase and earth

Discussion

6.	In case of single line to ground fault
A.	All sequence networks are connected in parallel
B.	All sequence networks are connected in series
C.	Positive and negative sequence networks are connected in parallel
D.	Zero and negative sequence networks are connected in series
Answer» C. Positive and negative sequence networks are connected in parallel

Discussion

7.	A sustained three phase fault occurs in the power system shown in the figure. The current and voltage phasors during the fault (on a common reference), after the natural transients have died down, are also shown. Where is the fault located?
A.	Point P
B.	Point Q
C.	Point R
D.	Point S
Answer» C. Point R

Discussion

8.	At the terminal of a 3ϕ, 6.6 kV, 10 MVA alternator, a load R = 200 Ω is connected between two phases, and other phase is kept open. The sequence impedance of the alternator is Z1 = Z2 = j 5Ω and Z0 = j2Ω. What is the current through the load resistance?
A.	50 A
B.	60 A
C.	75 A
D.	32 A
Answer» E.

Discussion

Explore topic-wise MCQs in Power Systems.

Five alternators, each of which is rated for 10 MVA, 11 KV with 25% reactance, operate in parallel order. What will be the short circuit level in the bus bar?

For a fault at the terminals of the synchronous generator, the fault current is maximum for a

A 50 Hz, 4 Pole, 500 MVA, 22 kV turbo generator is delivering rated MVA at a power factor of 0.8. Suddenly a fault occurs reducing the electric power output by 40%. Neglect the losses and assume constant power input to the shaft. The accelerating torque in the generator at the time of fault is

Line-to-ground fault occurs:

In case of single line to ground fault

A sustained three phase fault occurs in the power system shown in the figure. The current and voltage phasors during the fault (on a common reference), after the natural transients have died down, are also shown. Where is the fault located?

At the terminal of a 3ϕ, 6.6 kV, 10 MVA alternator, a load R = 200 Ω is connected between two phases, and other phase is kept open. The sequence impedance of the alternator is Z1 = Z2 = j 5Ω and Z0 = j2Ω. What is the current through the load resistance?