Power System - II (3150911) MCQs

MCQs of Transients in Power Systems

Showing 11 to 20 out of 106 Questions
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11.
A traveling wave 400 ∕ 1 ∕ 50 means crest value of
(a) 400 V with rise time of 1∕ 50 s
(b) 400 kV with rise time 1 s and fall time 50 s
(c) 400 kV with rise time 1 μs and fall time 50 μs
(d) 400 MV with rise time 1 μs and fall time 50 μs
Answer:

Option (c)

12.
A rectangular voltage wave is impressed on a loss-free overhead line, with the far end of the line being short-circuited. On reaching the end of this line
(a) The current wave is reflected back with positive sign, but the voltage wave with negative sign
(b) The current wave is reflected back with negative sign, but the voltage wave with positive sign
(c) Both the current and the voltage waves are reflected with positive sign
(d) Both the current and the voltage waves are reflected with negative sign
Answer:

Option (a)

13.
A short length of cable is connected between dead-end tower and sub-station at the end of a transmission line. Which of the following will decrease, when voltage wave is entering from overhead line to cable?
1. Velocity of propagation of voltage wave
2. Steepness of voltage wave
3. Magnitude of voltage wave
Select the correct answer using the codes given below
(a) 1 and 2
(b) 2 and 3
(c) 3 and 1
(d) 1, 2 and 3
Answer:

Option (d)

14.
Transient phenomenon last in a power system for a period ranging from
(a) Few ms to 1 second
(b) 1 second to 2 second
(c) 2 second to 3 second
(d) Greater than 3 second
Answer:

Option (a)

15.
Main cause of momentary excessive voltages and current are
1. Lightning
2. Switching
3. Short circuit
4. Resonance
Out of these the most common and most severe causes are
(a) 1 and 3
(b) 1 and 2
(c) 4 and 2
(d) 3 and 4
Answer:

Option (b)

16.
The reflection of surges at open ends leads to voltage build up, which may eventually damage the high voltage equipment
(a) True
(b) False
(c) Can not say anything
Answer:

Option (a)

17.
A major part of short circuit takes place on exposed overhead lines, due to the insulator failure caused by the surge phenomenon
(a) True
(b) False
(c) Can not say anything
Answer:

Option (a)

18.
Lightening arrester should be located
(a) Near the circuit breaker
(b) Away from the circuit breaker
(c) Near the transformer
(d) Away from the transformer
Answer:

Option (c)

19.
In a power system lightning arresters are used to protect the electrical equipment against
(a) Power frequency of over voltage
(b) Direct stroke of lightning
(c) Over current due to lightening stroke
(d) Over voltage due to indirect lightening stroke
Answer:

Option (d)

20.
In an extra high voltage overhead transmission line earth wire is provided to protect the line against
(a) Switching surges
(b) Lightening surges
(c) Corona effect
(d) Ensure fault voltages
Answer:

Option (b)

Showing 11 to 20 out of 106 Questions
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