Important MCQ on Power systems -8
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
Comments
Impedance relay is moderately affected by Arc resistance