Important MCQ on Power systems -8

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Important multiple choice questions in Power systems
1.       To limit current chopping in vacuum circuit breakers, the contact material used has
a)      High vapour pressure and low conductivity properties
b)      High vapour pressure and high conductivity properties
c)       Low vapour pressure and high conductivity properties
d)      Low vapour pressure and low conductivity properties
2.       For the same rupturing capacity, the actual current to be interrupted by an HRC fuse is
a)      Much less than any circuit breaker
b)      Much more than any circuit breaker
c)       Equal to the circuit breaker
d)      None of these
3.       For protection of parallel feeders fed from one end, the relays required are
a)      Non-directional relays at the source end and directional relays at the load end
b)      Non-directional relays at both the ends
c)       Directional relays at the source end and non-directional at the load end
d)      Directional relays at both the ends
4.       A reactance relay is
a)      Voltage restrained directional relay
b)      Directional restrained over-current relay
c)       Voltage restrained over-current relay
d)      None of these
5.       The ratio of reset to pickup current for an induction cup relay is approximately
a)      0.99
b)      1.0
c)       0.75
d)      None of these
6.       Mho relay is normally used for the protection of
a)      Long transmission lines
b)      Medium transmission lines
c)       Small transmission lines
d)      No length criterion
7.       The operation of the relay which is most affected due to arc resistance is
a)      Mho relay
b)      Reactance relay
c)       Impedance relay
d)      All are equally affected
8.       Precautions are essential for ensuring that the secondary of a CT is not open circuited when the primary circuit carries a current because
a)      Dangerously high voltage might develop across the secondary
b)      The ferromagnetic core may develop residential magnetism
c)       The reflected impedance may prevent the flow of current in the primary circuit
d)      None of the above
9.       In the protection of transformers, harmonic restraint is used to guard against
a)      Magnetizing inrush current
b)      Unbalanced operation
c)       Lightning
d)      Switching over voltages
10.   The use of high-speed circuit-breakers
a)      Reduces the short circuit current
b)      Improves system stability
c)       Decreases system stability
d)      Increases the short circuit current

Comments

Anonymous said…
The most affected relay due to arc resistance is Mho relay not impedance relay.
15 February 2016 at 05:32
Unknown said…
U were wrong... it is impedance relay only.... What he has given is 💯% right...
18 August 2017 at 11:32
Manikanta said…
it is mho relay only .....refer cl Wadhwa textbook pg no. 392 .....new edition.
7 January 2018 at 22:38
Unknown said…
Yes Mho relay is most affected
Impedance relay is moderately affected by Arc resistance
30 June 2018 at 04:56
Arun k said…
Harmonic restraint relay is used in Transformers for the protection of Magnetic In rush currents
16 May 2019 at 10:17
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