Switchgear and protection mcq
important switchgear and protection mcq (electrical engineering mcq)---
(a) inductive reactance
(b) capactive reactance
(c) a resistance decreasing with voltage rise across the arc
(d) resistance increasing with voltage rise across the arc
Ans:- c
Ans:- write in comment box
important switchgear and protection mcq (electrical engineering mcq)---
1. SF6 gas ---------
(a) has pungent small
(b) is nontoxic
(c) is lighter than air
(d) is yellow in colour
(e) all of the above
Ans:- b
2. The main function of a fuse -----
(a) protect the appliance
(b) prevent excessive currents
(c) open the circuit
(d) protect the line
(e) none of the above
Ans:- b
3. Which of the following medium is employed for extinction
of arc in air circuit breaker
(a) Mineral Oil
(b) Air
(c) SF6
(d) Water
Ans:- b
4. The arcing
contacts in a circuit breaker are made of
(a) Aluminium alloy
(b) copper tungsten alloy
(c) Magnine
(d) Nichrom
Ans:- b
5.With which of the following, a circuit breaker must be
equipped for remote operation----
(a) Time-delay trip
(b) Shunt trip
(c) Inverse time trip
(d) all of the above
(e) none of the above
Ans:-- b
6. Fault diverters are basically ----
(a) Relays
(b) fast switches
(c) contactors
(d) SF6 circuit breakers
Ans:- b
7. Arc in a circuit behaves as ---
(b) capactive reactance
(c) a resistance decreasing with voltage rise across the arc
(d) resistance increasing with voltage rise across the arc
Ans:- c
8. Relays
can be designed to respond to changes in
(a)
voltage and current
(b) resistance, reactance or impedance
(c) light intensity
(d) temperature
(e) all of the above
Ans:-- e
9. A
thermal protection switch can protect against -----
(a) short-circuit
(b) temperature
(c) overload current
(d) over voltage
(a) short-circuit
(b) temperature
(c) overload current
(d) over voltage
(e) none
of the above
Ans:- write in comment box
10. 10. Thermal circuit breaker has Ã
(a) instantaneous trip action
(b) delayed trip action
(c) both (a) and (b)
(d) none of the above
Ans:--b
11.
Overload relays are of ……. type.
(a) electromagnetic
(b) solid state
(c) thermal
(d)
induction
(e) all of the above
Ans: e
12. Thermal overload relays are used to protect
the motor against over current due to
(a) ground
(b) heavy loads
(c) short-circuits
(d) none of the above
Ans:-- b
13. D.C. shunt relays are made of
(a) few turns of thin wire
(b) few turns of thick wire
(c) many turns of thin wire
(d) many turns of thick wire
Ans – c
14. In order that current should flow without
causing excessive heating or voltage drop, the relay contacts should :---
(a) be of
sufficient size and proper shape
(b) be clean and smooth
(c) have low contact resistance
(d) all of
the above properties
Ans:--- d
15. Circuit breakers are essentially ---
(a) current carrying contacts called electrodes
(b) arc extinguishers
(c) circuits to break the system
(d) transformers to isolate the two systems
(e) any of the above
Ans:--- d
16. An efficient arid a well designed protective
relaying should have
(a) good selectivity and reliability
(b) high speed and selectivity
© - economy and simplicity
(d) all of the above
Ans:-- d
17. A differential relay measures the vector
difference between
(a) two
voltages
(b) two currents
(c) two or more similar electrical quantities
(d) all of the above
Ans:-- c
18. Burden of a protective relay is the power
(a) developed by the relay circuit
(b)
required to operate the circuit breaker
(C)
absorbed by the circuit of relay
(d) all of the above
Ans:--c
19. Directional relays are based on flow of ---
(a) voltage
(b) current
(c) power
(d) none
of the above
Ans:Ã C
20. ionization in circuit breaker is facilitated
by ---
(a) high temperature
(b) increase of mean free path
(c) increasing field strength
(d) all of the above
Ans: d
21. Shunt capacitance is neglected while
considering ->
(a) Long transmission line
(b) medium transmission line
(c) short transmission line
(d) medium and long transmission lines
Ans:----c
22. Overheating of relay contacts or contact born
out is due to -->
(a) too
low contact pressure
(b) foreign matter on the contact surface
(c) slow
making and breaking of load circuit contacts
(d) all of the above
Ans:- d
23. In a circuit breaker the basic problem is to Ã
(a) emit the ionizing electrons
(b) maintain the arc
(c) extinguish the arc
(d) transmit large power
Ans: --d
24. H.R.C. fuses provide best protection against
(a) short-circuits
(b) reverse current
(C) short-circuits
(d) overload
Ans:--c
25. The ground wire should not be smaller than No
_______ copper.
(a) 7
(b) 8
(c) 9
(d) 10
Ans:--- d
26. insulation resistance of high voltage circuit
breakers is more than
(a) 10 mega ohms
(b) 50 mega ohms
(c) 70 mega ohms
(d) 100 mega ohms
Ans:- d
27. The time of closing the cycle, in modern
circuit breakers is
(a) 0.001 sec
(b) 0.003 sec
(c) 0.010 sec
(d) 0.10 sec
(e) none of the above
Ans:--b
28. The delay fuses are used for the
protection of Ã
(a) light
circuits
(b) fluorescent lamps
(c) power outlet circuits
(d) motors
Ans:---d
29. Resistance grounding is used for voltage
between
(a) 11V to 33kV
(b) 3.3kV to 11kV
(c)
33kVto66kV
(d) none of the above
Ans: - write ans in comment box
30. The contacts of high voltage switches used in
power system are submerged in oil. The main purpose of the oil is to _->
(a) extinguish the arc
(b) insulate the contacts from switch body
(c) lubricate the contacts
(d) none of the above
(e) all of the above
Ans:-- a
31. undergrounded neutral transmission system is
not recommended because of system ->
(a) insulation being overstressed due to over
voltages
(b) insulation overstress may lead to failure and
subsequent phase to phase faults
(c) being inadequately protected against ground
fault
(d) all of the
above
Ans:-- d
32. The
reflection co-efficient at the open circuited end of a transmission lineÃ
(a) unity
(b) infinity
(c) zero
(d) none of the above
Ans:-- a
33. For
the protection of power station buildings against direct strokes the
requirements are
(a)
interception and conduction
(b)
interception
(c)
interception, conduction and dissipation
(d)
interception, conduction, dissipation and reflection
(e) all of
the above
Ans:-- c
34. The interaction between a transmission line
and communication line is minimized by
(a) increasing the height of the trans-mission
line tower
(b) transposing transmission as well as
communication lines
(c)
increasing the distance between the two lines
(d) All of the above
Ans:-- d
35. Discrimination between main and back up
protection is provided by the use of relays which are
(a) slow
(b) fast
(c) sensitive
(d) none of the above
Ans:- a
36. When a wave propagates on a transmission
line, it suffers reflection several
times at
(a) sending end
(b) load end
(c) tapping
(d) sending and receiving end
(e) all of the above
Ans: d
37. Induction cup relay is operated due to
changes in-->
(a) impedance
(b) voltage
(c) current
(d)alI of the above
(e) none of the above
Ans:- d
38. Which of the following statements is
incorrect-->
(a) Shunt reactors are used as compensation
reactors
(b) Lightning arrestors are used before the
switchgear
(c) The peak short current is (1.8 xV2) times the
A.C. component
(d) The MVA at fault is equal to base MVA divided
by per unit equivalent fault reactance
Ans:--b
39. A.C. network analyser is used to solve
problems of
(a) load flow
(b) load
flow, short-circuit and stability
(c) load flow and stability
(d) load flow and short-circuit
(e) none of the above
Ans:--b
40. To reduce short circuit fault currents are
used
(a) capacitors
(b) reactors
(c) resistors
(d) none of the above
Ans:-- a
41. For cost and safety, the outdoor substations
are installed for voltages above
(a) 11 kV
(b) 33 kV
(c) 66 kV
(d) 132 kv
Ans:- b
42. relays are used for phase faults on long
line.
(a) Reactance
(b) impedance
(c) both (a) and (b)
(d) None of the above
Ans:-- b
43. For which of the following protection from
negative sequence currents is provided
(a) Transformer
(b) Motors
(c) Transmission line
(d)
Generator
Ans-->
d
44. Distance relays are generally--
(a)
impedance relays
(b)
reactance relays
(c)
split-phase relays
(d) none of the above
Ans:- d
45. which of these used to measure the stator % winding
temperature of the generator.
(a) thermocouple
(b) pyrometer
(c) thermometer
(d) resistance thermometer
Ans:- d
46. . The single phasing relays are used for the
protection of
(a) two phase motors only
(b) two single phase motors running in parallel
(c) three
phase motors
(d) single phase motors only
Ans:- c
47. Series reactors must have --
(a) low resistance
(b) high reatance
(c) low impedance
(d) high impedance
Ans:- a
48. Which
of the following circuit breakers has high reliability and minimum maintenance
(a) Oil circuit breakers
(b) Vacuum circuit breakers
(c )
Circuit breaker with SF6 gas
(d) Air blast circuit breakers
Ans:- c
49. Arc in
a circuit breaker is interrupted at Ã
(a) zero current
(b) maximum current
(c) minimum voltage
(d) maximum voltage
Ans:-- a
50. Series capacitors are used to Ã
(a) compensate for line capacitive reactance
(b) compensate for line inductive reactance
(c) improve line current
(d) none of the above
Ans:- b
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