22524 Switchgear & Protection Mcqs for MSBTE Online Exams With Answer & MSBTE Solution
22524 SAP Switchgear & Protection Mcqs for Electrical Engineering
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Program: Diploma in Electrical engineering Program Code:- EE
Scheme:-I Semester:- 5
Course:- Switchgear and Protection Course Code:- 22524
{tocify} $title={Unit Wise MCQs}
Question Bank for Multiple Choice Questions
01 – Basic of Protection Marks:-10
Content of Chapter:-
1.1 Necessity, functions of protective system
1.2 Normal and abnormal conditions.
1.3 Types of faults and their causes.
1.4 Protection zones and backup protection
1.5 Short circuit fault calculations in lines fed by generators through transformers
1.6 Need of current limiting reactors their arrangements.
1. The factors influencing the faults are
(A) Supply voltage
(B) Demand
(C) Current
(D) Loss
Answer: -Option C
Explanation: - magnitude of current affects the fault condition
2. In which portion of the power system is the occurrence of the fault more common?
(A) Alternator
(B) Transformer
(C) Transmission line
(D) Underground cable
Answer: -Option C
Explanation: -transmission line conductor is bare and overhead conductor
3. Which of following are used to reduce short circuit fault currents?
(A) Reactors
(B) Resistors
(C) Capacitors
(D) Parallel combination of all these
Answer: - Option A
Explanation: -reactor performs function of inductor which opposes to change in current
4. Shunt reactors are connected with transmission lines for?
(A) Limiting fault current
(B) Absorbing reactive power
(C) Absorbing high voltage surges
(D) Limiting fault current
Answer: - Option B
Explanation: -To limit flow of reactive power in transmission line
5. Minimum faults occur in which of the following power system equipment?
(A) Transformer
(B) Switchgear
(C) CT
(D) Alternator
Answer: - Option D
Explanation: -alternator are connected in generating station and it is not directly connected to feeder
6. Signals circuit breaker in case of fault:
(A) Fuse
(B) Isolator
(C) Ct
(D) Relay
Answer: - Option D
Explanation: - relay acts as a sensing device which transfers signal to circuit breaker
7. Which of thermal protection switch is provided in power line system to protect against?
(A) Over voltage
(B) Short circuit
(C) Temperature rise
(D) Overload
Answer: - Option D
Explanation: -in overload condition large amount of heat is developed to protect from it thermal protection switch is provided
8. Series reactors are used to
A) Improve transmission efficiency
B) Improve power factor
C) improve voltage regulation
D) Bring down fault level
Answer: - Option D
Explanation: - reactors are use to minimize fault current
9. The voltage of domestic supply is 220 V. This figure represents
(A) Mean value
(B) r.m.s. value
(C) Peak value
(D) Average value
Answer: - Option A
10. On which among the following factors does the magnitude of the fault current depend?
(A) Total impedance upto the fault.
(B) Voltage at the fault point
(C) Both (a) and (b)
(D) None of these
Answer: Option A
11. Which of the following fault results into a three phase faults?
(A) Single line to ground fault.
(B) Double line to ground fault
(C) Line to line fault
(D) Fault due to all the three phases to earth.
Answer: - Option D
Explanation: all three phases involved in this fault
12. Fault diverters are basically
(A) Circuit breaker
(B) Fast switches
(C) Relay
(D) Fuses
Answer: - Option B
Explanation: - fast switches are used to divert the fault
13. Lightening arrestor should be located
(A) Away from the circuit breaker
(B) Near the transformer
(C) Away from the transformer
(D) Near the circuit breaker
Answer: - Option B
Explanation: -to protect from lightning stroke lightning stroke are used
14. Secondary protection called as
(A) Primary protection
(B) Double protection
(C) Tertiary protection
(D) Back up protection
Answer: - Option D
15. Series reactors are used to
(A) Improve transmission efficiency
(B) Improve power factor
(C) Improve voltage regulation
(D) Bring down fault level
Answer: - Option D
Explanation: - reactor are used to minimize magnitude of fault current
16. Effect of fault of fault
(A) Magnification of fault current
(B) Damaged to equipment
(C) Safety
(D) All of above
Answer: - Option D
Explanation: -fault current always produces heat ultimately damage to system
17. Percentage of overhead faults are
(A) 50%
(B) 80%
(C) 70%
(D) 09 %
Answer: Option A
18. Percentage of underground line fault is
(A) 50%
(B) 80%
(C) 70%
(D) 09 %
Answer: Option D
19. Percentage of generator fault
(A) 50%
(B) 80%
(C) 70%
(D) 07 %
Answer: -Option D
20. Percentage of transformer fault
(A) 50%
(B) 80%
(C) 70%
(D) 10 %
Answer: -Option D
20. Percentage of switchgear fault
(A) 50%
(B) 80%
(C) 70%
(D) 12 %
Answer: -Option D
21. Percentage of fault occurs on ct, pt
(A) 50%
(B) 80%
(C) 70%
(D) 12 %
Answer: -Option D
22. Requirement of protective system
(A) Selectivity
(B) Speed
(C) Sensitivity
(D) All of above
Answer: -Option D
Explanation: - all are characteristic required for protective system
23. Qualities of protective system
(A) Selectivity
(B) Simplicity
(C) Economy
(D) all of above
Answer: -Option D
Explanation: - all are characteristic required for protective system
24. The main function of a fuse is to
(A) Protect the line
(B) Open the circuit
(C) Protect the appliance
(D) Prevent excessive currents
Answer: -Option D
25. On which of the following routine tests are conducted?
(A) Oil circuit breakers
(B) Air blast circuit breakers
(C) Minimum oil circuit breakers
(D) All of the above
Answer: -Option D
26. SF6 gas
(A) is yellow in colour
(B) is lighter than air
(C) is nontoxic
(D) Has pungent small
Answer: -Option C
27. The arcing contacts in a circuit breaker are made of
(A) Copper tungsten alloy
(B) Porcelain
(C) Electrolytic copper
(D) Aluminum alloy
Answer: -Option A
28. With which of the following, a circuit breaker must be equipped for remote operation ?
(a) Inverse time trip
(b) Time-delay trip
(c) Shunt trip
(d) None of the above
Answer: -Option C
29. Fault diverters are basically
(a) Fuses
(b) Relays
(c) Fast switches
(d) Circuit breakers
Answer: -Option C
30. A thermal protection switch can protect against
(a) Short-circuit
(b) Temperature
(c) Overload
(d) Over voltage
Answer: -Option C
31. Arc in a circuit behaves as
(a) Capacitive reactance
(b) An inductive reactance
(c) A resistance increasing with voltage rise across the arc
(d) A resistance decreasing with voltage rise across the arc
Answer: -Option D
32. Thermal circuit breaker has
(a) Delayed trip action
(b) Instantaneous trip action
(c) Both of the above
(d) None of the above
. Answer: -Option A
33. Relays can be designed to respond to changes in
(a) Resistance, reactance or impedance
(b) Voltage and current
(c) Light intensity
(d) all
Answer: -Option D
34. Overload relays are of.....type.
(a) Induction
(b) Solid state
(c) thermal
(d) All above
Answer: -Option D
35. Thermal overload relays are used to protect the motor against over current due to
(a) Short-circuits
(b) Heavy loads
(c) Grounds
(d) All of the
Answer: -Option B
36. Magnetic circuit breaker has____ trip action.
(a) Delayed
(b) Instantaneous
(c) Both of the above
(d) None of the
Answer: -Option B
37. 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
Answer: -Option C
38. The relay operating speed depends upon
(a) The spring tension
(b) The rate of flux built up
(c) Armature core air gap
(d) all of the above
Answer: -Option C
39. In order that current should flow without causig excessive heating or voltage drop, the relay
contacts should
(a) Have low contact resistance
(b) Be clean and smooth
(c) Be of sufficient size and proper shape
(d) Have all above properties
Answer: -Option C
40. Circuit breakers usually operate under
(a) Transient state of short-circuit current
(B) Sub-transient state of short-circuit current
(c) Steady state of short-circuit current
(d) After D.C. component has ceased
Answer: -Option A
41. 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
Answer: -Option A
42. the current zero interruption, in oil and air blast circuit breakers, is achieved by
(a) Lengthening of the gap
(b) Cooling and blast effect
(c) Both (a) and (b)
(d) Deionizing the oil with forced air
Answer: -Option C
43. Air blast circuit breaker is used for
(a) Over currents
(b) Short duty
(c) Intermittent duty
(d) Repeated duty
Answer: -Option D
44. An efficient and a well designed protective relaying should have
(a) Good selectivity and reliability
(b) Economy and simplicity
(c) High speed and selectivity
(d) all of the above
Answer: -Option D
45. Burden of a protective relay is the power
(a) Required to operate the circuit breaker
(b) Absorbed by the circuit of relay
(c) Developed by the relay circuit
(d) None of the above
Answer: -Option B
46. Directional relays are based on flow of
(a) Power
(b) Current
(c) Voltage wave
(d) all of the above
Answer: -Option A
47. A differential relay measures the vector difference between
(a) Two currents
(b) Two voltages
(c) Two or more similar electrical quantities
(d) None of the above
Answer: -Option C
48. A transmission line is protected by
(a) Inrush protection
(b) Distance protection
(c) Time graded and current graded over current protection
(d) Both (b) and (c)
Answer: -Option D
49. Large internal faults are protected by
(a) Merz price percentage differential protection
(b) Mho and ohm relays
(c) Horn gaps and temperature relays
(d) Earth fault and positive sequence relays
Answer: -Option A
50. When a transmission line is energized, the wave that propagates on it is
(a) Current wave only
(b) Voltage wave only
(c) Both (a) and (b)
(d) Power factor wave only
Answer: -Option C
51. Protective relays are devices that detect abnormal conditions in electrical circuits by measuring
(a) current during abnormal condition
(b) Voltage during abnormal condition
(c) Constantly the electrical quantities which differ during normal and abnormal conditions
(d) None of the above
Answer: -Option C
52. The voltage appearing across the contacts after opening of the circuit breaker is called voltage.
(a) Recovery
(b) Surge
(c) Operating
(d) Arc
Answer: -Option A
53. 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
Answer: -Option D
54. In a circuit breaker the basic problem is to
(a) Maintain the arc
(b) Extinguish the arc
(c) Transmit large power
(d) Emit the ionizing electrons
Answer: -Option C
55. Overheating of relay contacts or contact born out is due to
(a) Slow making and breaking of load circuit
(b) Contacts
(c) Foreign matter on the contact surface
(d) Too low contact pressure (e) all of above
Answer: -Option E
56. Interruption of large currents by relay requires
(a) Arc suppressing blow out coils
(b) Wide separation of the opened contacts
(c) High speed opening of contacts
(d) all of the above
Answer: -Option D
57. Shunt capacitance is neglected while considering
(a) Short transmission line
(b) Medium transmission line
(c) Long transmission line
(d) Medium and
Answer: -Option A
02 – Circuit Interrupting Device Marks:-16
Content of Chapter:-
2.1 Necessity, functions of protective system.
2.2 Circuit Interrupting Device, Isolators- Vertical break, Horizontal break & Pantograph type Construction,
2.3 characteristics of HRC Fuse
2.4 Arc formation process, methods of arc extinction – High resistance method, Low resistance or current zero
method Definition: Arc voltage, Recovery voltage, Restriking voltage, RRRV
2.5 H.T – Air Blast Circuit Breaker,
2.6 Sulphur Hexa Fluoride circuit breaker (SF6), Vacuum circuit breaker
2.7 L.T.- Air circuit breakers (ACB), Miniature circuit breakers
2.8 (MCB),Moulded case circuit breaker (MCCB), Earth leakage circuit breaker
2.9 Selection and rating of circuit breakers, Selection of MCCB for motor.
2.10 Gas insulated switch gear
2.11 Introduction of E-TAB
1. Why are the isolators used?
a) Break abnormal current
b) Making under fault conditions
c) Breaking the circuit under no load condition
d) None of the above
Answer: -Option C
Explanation: - it is used to isolate circuit in no load condition
2. Which among these are the main characteristics of a fuse element??
a.) Low melting point
b). High conductivity
c.) Least deterioration due to oxidation
d.) All of the above
Answer: -Option D
Explanation: - all are required
3. SF6 gas has excellent heat transfer properties because of its
A. Low gaseous viscosity
B. High dielectric strength
C. Higher molecular weight
D. Both A and C
Answer: -Option D
Explanation: - dielectric material is good heat transfer properties
4. SF6 gas is transported in
A. Air cylinders
B. Gas cylinders
C. Liquid form in cylinders
D. Solid form
Answer: -Option C
Explanation: - it is is in gaseous form
5. Why is an isolator installed?
a) To isolate one portion of the circuit from another
b) As an substitute for the circuit breaker
c) It used on either sides of the circuit breaker
d.) Both (a) and (c)
Answer: -Option D
Explanation: - it is is used to isolate circuit
6. Why are the isolators used?
a) Break abnormal current
b.)Making under fault conditions
c) Breaking the Circuit under no load condition
d.) None of the above
Answer: -Option C
Explanation: - it is used to isolate
7. Which among these are the main characteristics of a fuse element?
A. Low melting point
B. High conductivity
C. Least deterioration due to oxidation
D. All of the above
Answer: -Option D
Explanation: - it is is used to isolate
8. Which among the following statement is true related to fuse?
a. Greater the current smaller is the time taken by the fuse to blow out.
b. Greater the current greater is the time taken by the fuse to blow out
c. The current is directly proportion to the blow out time of fuse.
d. Is dependent on the temperature and atmospheric conditions
Answer: -Option A
Explanation: -large current produces more heat which melts fusing element
9. What is the maximum current upto which fuses can be used?
a. 25 A
b. 50 A
c. 75 A
d. 100 A
Answer: -Option D
10. Arc interruption is done by
a) High resistance interruption
b) Low resistance interruption
c) Both (a) and (b)
d) None of these
Answer: -Option C
Explanation: resistance is opposes to flow of current which reduces magnitude of current
11. Rate of rise restriking voltage depends upon
a) Active recovery voltage
b) Natural frequency of oscillations
c) Both (a) and (b)
d) Rating of circuit breaker
Answer: -Option C
12. Desired tripping of a circuit breaker is
a) Manually
b) Automatically
c) That it should give warning
d) None of these
Answer: -Option b
Explanation: automatic operation isolates faulty part in less time
13. In circuit breaker, to facilitate arc quenching, dielectric strength can be increased by
a) Lengthening of the gap
b) Cooling
c) Blast effect
d) All of these
Answer: -Option D
Explanation: -all are methods of arc quenching
14. SF6 gas has excellent heat transfer properties because of its
A. Low gaseous viscosity
B. High dielectric strength
C. Higher molecular weight
D. Both A and C
Answer: -Option D
15. Keeping in view the cost and the overall effectiveness, which of the following circuit breaker is
best suited for capacitor bank switching?
a) Vacuum circuit breaker
b) Air blast cb
c) Sf6
d) Oil cb
Answer: -Option A
Explanation: -arc quenching medium available directly through air
16. the current zero interruption, in oil and air blast circuit breakers, is achieved by
a) Lengthening of the gap
b) Cooling and blast effect
c) Both 1 and 2
d) Deionizing the oil with forced air
Answer: -Option C
Explanation: -both are the methods of current interruption
17. Fuse is a device which is used for ___________.
a) protection
b)amplification
c) impedance matching
d)none of above
Answer: -Option A
18. Fuse is connected in Parallel. True / False
a) TRUE
b)False
Answer: -Option B
19.Fuses are used in circuit for ________________
a) Equipment Safety
b)Human Safety
c)None of Above
d)a & b are correct
Answer: -Option D
20. Fuse is an Electronic Component used for ___________
a)Current limiting
b) power limiting
c)a & b are correct
d)none of above
Answer: -Option A
21. HRC stands for High Rupturing Capacity. True / False
a)TRUE
b)False
Answer: -Option A
22. The melting point of Fuse element is ____________.
a) low
b)medium
c)high
d)all are correct
Answer: -Option C
23. HRC Fuse used in ____________.
a)industrial motors
b)domestic wiring
c)distribution system
d)all are correct
Answer: -Option A
24. Fuse wire are always connected with _________.
a)Phase
b)neutral
c)earth
d)all are correct
Answer: -Option A
25. The part of fuse where the fuse wire is installed are called ___________.
a) fuse link
b)fuse base
c)none of above
d)a & b are correct
Answer: -Option A
26. The maximum current rating capacity of HRC fuse is ___________.
a)250 Amp
b)300 Amp
c)350 Amp
d)450 Amp
Answer: -Option B
27. The cheapest form of protection is ___________.
a)relay
b)circuit breaker
c)fuse
d)switch
Answer: -Option C
28.Miniature circuit breaker is a small
a)fuse
b)magnetic switch
c)electromagnetic switch
d)two way switch
Answer: -Option C
29.Circuit breakers work
a)constantly
b)only once
c)when there is resistance
d)when there is magnetic field
Answer: -Option A
30. What does “MCB” stand for?
a) Miniature circuit breaker
b) Mini circuit breaker
c) Miniature capacitor breaker
d) Mini Capacitance breake
Answer: -Option A
31. What is the standard colour of ac supply ground wire in India?
a) Red
b) Magenta
c) Pink
d) Green
Answer: -Option D
32. What is the standard colour of ac supply neutral wire in India?
a) Red
b) Black
c) Pink
d) Green
Answer: -Option B
33. The rating of the circuit breaker is usually determined on the basis of ____________ fault.
a. Symmetrical.
b. Line to line
c. Single line to ground
d. Double line to ground
Answer: -Option A
34. Which of the following circuit breakers has the lowest operating voltage?
a. SF6 circuit breaker
b. Air break
c. Air blast
d none
Answer: -Option A
35.Circuit breakers usually operate under
a. Steady short circuit current
b. Sub transient state of short circuit current
c. Transient state of short circuit current
Answer: -Option C
36.The making capacity of a circuit breaker is
A. Less than the asymmetrical breaking capacity of the breaker
B. Greater than the asymmetrical breaking capacity of the breaker
C. Equal to the symmetrical breaking capacity of the breaker
D. Equal to the asymmetrical breaking capacity
Answer: -Option B
37.Earthing is necessary to give protection against
A. Danger of electric shock
B. Voltage fluctuation
C. Overloading
D. High temperature of the conductors
Answer: -Option B
38.earting wire made up of
a. Copper
b.aluminium
c.iron
d.galvanised steel
Answer: -Option D
39.factors on soil resistance depends
a )depth of electrode
b) moisture
c )all of above
d )temprature
Answer: -Option C
40. What is earthing?
a) connecting electrical machines to earth
b) providing a connection to the ground
c) connecting the electrical machines to source
d) providing a source of current
Answer: -Option A
41. What is an earth electrode?
a) electrode that is connected to earth
b) material used for earthing
c) electrode connected to the circuit
d) electrode which is connected to the mains
Answer: -Option B
42.Earth electrode provides ____________
a) high resistance
b) medium resistance
c) low resistance
d) very high resistance
Answer: -Option C
43.In a three phase system, the neutral is _________
a) earthed
b) connected to low voltage
c) connected to high voltage
d) not connected
Answer: -Option A
44.After earthing, the different parts of an electrical machinery are at _________
a) infinite potential
b) intermediate potential
c) zero potential
d) undefined potential
Answer: -Option C
45.Connection of the various parts of a circuit to earth has a _________
a) medium resistance
b) high resistance
c) very high resistance
d) very low resistance
Answer: -Option D
46.Specific resistance of soil is _________
a) changes from soil to soil
b) is constant
c) depends on the circuit connected to it
d) depends on the supply voltage
Answer: -Option A
47. In Railway applications_____circuit breaker is used.
(a) SF6
(b) bulk oil
(c) minimum oil
(d) air break
Answer: -Option D
48.To protect most of the electrical equipment handling low power, the types of relays used are
(a) thermocouple
(b) electronic and bimetallic
(c) both (a) and (b)
(d) none of the above
Answer: -Option C
49.Wave trap is used to trap waves of
(a) power frequencies
(b) higher frequencies entering generator or transformer units
(c) either of the above
(d) none of the above
Answer: -Option B
50.Ungrounded neutral transmission systemm 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
Answer: -Option D
51. The reflection co-efficient at the open circuited end of a transmission line.
(a) zero
(b) infinity
(c) unity
(d) none of the above
Answer: -Option C
52.For the protection of power station buildings against direct strokes the requirements are
(a) interception
(b) interception and conduction
(c) interception, conduction and dissipation
(d) interception, conduction, dissipation and reflection
Answer: -Option C
53. The line insulation is the insulation level of the station equipment.
(a) less than
(b) same as
(c) more than
(d) not directly related
Answer: -Option C
54.The interaction between a transmission line and communication line is minimized by
(a) transposing transmission as well as communication lines
(b) increasing the height of the trans-mission line tower
(c) increasing the distance between the two lines
(d) all of the above
Answer: -Option D
55.When a wave propagates on a transmission line, it suffers reflection several times at
(a) tapping
(b) load end
(c) sending end
(d) sending and other end
Answer: -Option D
56. Which of the following statements is incorrect?
(a) Station batteries are used to operate relay only
(b) The lightning arresters are basically surge diverters
(c) An impedance relay has maximum fault current when fault occurs near the relay
(d) A high speed relay has an operation of 1 to 2 cycles
Answer: -Option A
57.Discrimination between main and back up protection is provided by the use of relays which
are
(a) fact
(b) sensitive
(c) slow
(d) none of the above
Answer: -Option C
58.Induction cup relay is operated due to changes in
(a) current
(b) voltage
(c) impedance
(d) all of the above
Answer: -Option D
59.A.C. network analyzer is used to solve problems of
(a) load flow
(b) load flow and short-circuit
(c) load flow and stability
(d) load flow, short-circuit and stability
Answer: -Option D
.60.Which of the following statements is incorrect?
(a) Lightning arrestors are used before the switchgear
(b) Shunt reactors are used as compensation reactors
(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
Answer: -Option A
61.Short-circuit currents are due to
(a)single phase to ground faults
(b) phase to phase faults
(c) two phase to ground faults
(d) any of these
Answer: -Option D
67. To reduce short circuit fault currents are used.
(a) reactors
(b) resistors
(c) capacitors
(d) none of the above
Answer: -Option A
68.Bus coupler is very essential in arrangement
(a) single bus
(b) double bus, double breaker
(c) main and transfer bus
(d) all
Answer: -Option C
69.For cost and safety, the outdoor substations are installed for voltages above
(a) 11 kV
(b) 33 kV
(c) 60kV
(d) 110kV
Answer: -Option C
70.The short circuit in any winding of the transformer is the result of
(a) mechanical vibration
(b) insulation failure
(c) loose connection
(d) impulse voltage
Answer: -Option D
71. Relays are used for phase faults on long line.
(a) Impedance
(b) Reactance
(c) Either of the above
(d) None of the above
Answer: -Option A
72. For which of the following protection from negative sequence currents is provided?
(a) Generators
(b) Motors
(c) Transmission line
(d) Transformers
Answer: -Option A
73. Relay is preferred for phase fault on short transmission line.
(a) Induction type
(b) Reactance
(c) Impedance
(d) None of the above
Answer: -Option B
74. Distance relays are generally
(a) split-phase relays
(b) reactance relays
(c) impedance relays
(d) none of the above
Answer: -Option B
75. For which of the following ratings of the transformer differential protection is
recommended?
(a) Above 30 kVA.
(b) equal to and above 5 MVA
(c) equal to and above 25 MVA
(d) none of the above
Answer: -Option B
76. Air used to measure the stator % winding temperature of the generator.
(a) thermocouple
(b) pyrometer
(c) resistance thermometer
(d) thermometer A
Answer: -Option B
77.The under voltage relay can be used for
(a) generators
(b) bus bars
(c) transformers
(d) all of the above
Answer: -Option B
78.The relay with inverse time characteristic will operate within
(a)1.5 sec
(b) 5 to 10 sec
(c) 5 to 20 sec
(d) 20 to 30 sec
Answer: -Option B
79.The single phasing relays are used for the protection of
(a) single phase motors only
(b) two phase motors only
(c) two single phase motors running in parallel
(d) three phase motors
Answer: -Option D
80. Which of the following devices will receive voltage surge first travelling on the
transmission line?
(a) Lightning arresters
(b) Relays
(c) Step-down transformer
(d) Switchgear
Answer: -Option A
81. Which of the following parameter can be neglected for a short line?
(a) Inductance
(b) Capacitance
(c) Resistance
(d) Reactance
Answer: -Option B
82.Series reactors should have
(a) low resistance
(b) high resistance
(c) low impedance
(d) high impedance
Answer: -Option B
83. Which of the following circuit breakers has high reliability and minimum maintenance?
(a) Air blast circuit breakers
(b) Circuit breaker with SF6 gas
(c) Vacuum circuit breakers
(d) Oil circuit breakers
Answer: -Option B
84.Arc in a circuit breaker is interrupted at
(a) zero current
(b) maximum current
(c) minimum voltage
(d) maximum voltage
Answer: -Option A
85. What will be the reflection co-efficient of the wave of load connected to transmission line if
surge impedance of the line is equal to load?
(a) Zero
(b) Unity
(c) Infinity
(d) None of the above
Answer: -Option A
86.The inverse definite mean time relays are used for over current and earth fault protection of
transformer against
(a) heavy loads
(b) internal short-circuits
(c) external short-circuits
(d) all
Answer: -Option B
87.Over voltage protection is recommended for
(a) hydro-electric generators
(b)steam turbine generators
(c) gas turbine generators
(d) all of the above
Answer: -Option B
88.Air blast circuit breakers for 400 kV power system are designed to operate in
(a) 100 microsecond
(b) 50 millisecond
(c) 0.5 sec
(d) 0.1 sec
Answer: -Option B
89.Overfluxing protection is recommended for
(a) distribution transformer
(b) generator transformer of the power plant
(c) auto-transformer of the power plant
(d) station transformer of the power plant
Answer: -Option B
90.Series capacitors are used to
(a) compensate for line inductive reactance
(b) compensate for line capacitive reactance
(c) improve line voltage
(d) none of the above
Answer: -Option C
91. Admittance relay is______ relay.
(a) impedance
(b) directional
(c) non-directional
(d) none of the above
Answer: -Option B
92. The material used for fuse must have
(a) low melting point and high specific resistance
(b) low melting point and -low specific resistance
(c) high melting point and low specific resistance
(d) low melting point and any specific resistance
Answer: -Option A
93.If the fault occurs near the impedance relay, the VII ratio will be
(a) constant for all distances
(b) lower than that of if fault occurs away from the relay
(c) higher than that of if fault occurs away from the relay
(d) none of the above
Answer: -Option B
03 – Protective relay Marks:-16
Content of Chapter:-
3.1 Fundamental quality requirements: Selectivity, Speed, Sensitivity, Reliability, Simplicity, Economy.
3.2. Basic relay terminology- Protective relay, Relay time, Pick up, Reset current, current setting, Plug setting
multiplier, Time setting multiplier.
3.3 Protective relays: Electromagnetic disc relay operation, Thermal relay. Block diagram and working of
Static relay, over voltage relay.
3.4 Over current relay-Time current characteristics.
3.5 Microprocessor based protection relays: Block diagram, working and protection features.
3.6 Distance relaying- Principle
3.7 Directional relay: Need and operation with block diagram.
3.8 Operation of current and voltage differential relay.
1. Burden of a protective relay is the power
A. Required to operate the circuit breaker
B. absorbed by the circuit of relay
C. Developed by the relay circuit
D. None of the above
Answer: -Option B
2. The protective relays is provided to
A. Provide additional safety to the circuit breaker in its operation
C. Limit the arcing current during the circuit breaker operation
B. Close the contacts when the actuating quantity attains a certain predetermined value
D. Earth any stray voltage
Answer: -Option B
Explanation: -relay operates on predefine value
3. For the protection of very long extra high-voltage lines, the productive relay used is
A. Over currently with extremely inverse characteristics
B. Percentage differential relay
C. Reactance type distance relay
D. Mho type distance relay
Answer: -Option D
Explanation: -these are used for protection of transmission line
4. Buchholz relay is
A. Located in the conservator tan
B. Located in the transformer tank itself
C. Connected in the pipe connecting main tank of transformer and conservator
D. Installed in the circuit breaker
Answer: -Option C
Explanation: -these are used for transformer protecton
5. Thermal relays are used for protection of motors against over current owing to
A. Short circuits
B. Heavy loads
C. Earth fault
D. All of the above
Answer: -Option B
Explanation: -to isolate heavey load current
6. Thermal relay are often employed in
A. Motor starters
B. Transformer protection
C. Generator protection
D. None of the above
Answer: -Option A
Explanation: -motor starting current is
7. Two input phase comparator in a static relay is made up of a
A. transformer amplifier
B. Transistor logic circuit
C. Rectifier Bridge
D. Thyrister Bridge
Answer: -Option C
8. The operating speed of a relay depends upon the
A. Rate of flux built up
B. Armature core air gap
C. Spring tension
D. All of these
Answer: -Option D
9. Inverse time current relays are used for the protection of
A. Feeders
B. Transformers
C. Alternators
D. Both A and B
Answer: -Option D
10. Distance relays are generally
A. Split phase relays
B. Reactance relays
C. Impedance relays
D. None of the above
Answer: -Option D
11. Three step time distance characteristic of distance relay can be had by
A. Changing taps on voltage transformer
B. Separate measuring elements for zones 2 and 3
C. Switching resistance in relay restrains circuit at pre-set time interval by means of a timer element
D. Any of the above
Answer: -Option D
12. Distance protection scheme is preferred over graded lime-lag over-current protection in HV and
EHV lines because
A. It is faster in operation
B. It is simple
C. It is cheaper in cost
D. All of the above
Answer: -Option A
13. Which of the following relay is/are overload relays?
A. Thermal
B. Electromagnetic
C. Induction
D. All of the above
Answer: -Option D
14. The torque produced in shaded pole structure induction type relay is
A. Proportional to the square of the current
B. Proportional to the current
C. Inversely proportional to the current
D. Inversely proportional to the square of the current
Answer: -Option B
15. If the fault occurs near the impedance relay, the V/I ratio will be
A. Constant for all distances
B. Lower than that of if fault occurs away from the relay
C. Higher than that of if fault occurs away from the relay
D. None of the above
Answer: -Option B
16. The relay with inverse time is
A .Directly proportional to the square of fault current
B .Direct proportional to the of fault current
C. Inversely proportional to the of fault current
D. Inversely proportional to the square of fault current
Answer: -Option C
17. Protective relays can be designed to respond to
a) Light intensity
b) Temperature
c) Resistance, reactance or impedance
d) All of the above
Answer: -Option C
18. Protective relays are the devices that detect abnormal conditions in electrical circuits by
measuring
a) Voltage
b) Current
c) Constantly the electrical quantities which differ during normal and abnormal conditions
d) Note the above
Answer: -Option C
19. The protective relays is provided to
a) Provide additional safety to the circuit breaker in its operation
b) Close the contacts when the actuating quantity attains certain predetermined
c) Limit the arcing current during the circuit breaker operation
d) Earth any stray voltage
Answer: -Option B
20. For the protection of very long extra high-voltage lines, the productive relay used is
a) Over currently with extremely inverse characteristics
b) Percentage differential relay
c) Reactance type distance relay
d) Mho type distance relay
Answer: -Option D
21. Burden of a protective relay is the power
a) Required to operate the circuit breaker
b) Absorbed by the circuit of relay
c) Developed by the relay circuit
d) None of the above
Answer: -Option B
22. Buchholz relay is
a) Located in the conservator tank
b) Located in the transformer tank itself
c) Connected in the pipe connecting main tank of transformer and conservator
d) Installed in the circuit breaker
Answer: -Option C
23. Buchholz relays are used on
a) Air cooled Transformers
b) Instrument Transformers
c) Distribution transformers
d) Oil immersed power transformers of ratings above 500 Kva
Answer: -Option D
24. Buchholz relay cannot be used on
a) Three-phase transformers
b) Air cooled transformers
c) 500 KV transformers
d) D.1000 kV transformers
Answer: -Option B
25. Buchholz relay is a.......relay
a) Oil immersed
b) Arc quenching
c) Gas actuated
d) None of the above
Answer: -Option C
26. Buchholz relay can detect faults..........oil level in the transformer.
a) Upper
b) Below
c) Same
d) None of the above
Answer: -Option B
27. Distance relays are generally
a) Split phase relays
b) Reactance relays
c) Impedance relays
d) None of the above
Answer: -Option D
28. Three step time distance characteristic of distance relay can be had by
a) Changing taps on voltage transformer
b) Separate measuring elements for zones 2 and 3
c) Switching resistance in relay restrains circuit at pre-set time interval by means of a timer element
d) Any of the above
Answer: -Option D
29. Distance protection scheme is preferred over graded lime-lag over-current protection in HV and
EHV lines because
a) It is faster in operation
b) It is simple
c) It is cheaper in cost
d) All of the above
Answer: -Option A
30. Which of the following relay is/are overload relays?
a) Thermal
b) Electromagnetic
c) Induction
d) All of the above
Answer: -Option D
04 – Protective relay Marks:-16
Content of Chapter:-
4.1Faults
4.2 Differential protection: over current, earth fault,
Overheating and field failure protection.
4.3 Reverse power protection.
1. List two limitations of Differential-Protection scheme for transformer
(a) To ensure maximum safety conditions from generation stage to consumers premises.
(b) Tap changing may lead to change in settings & improper operation
(c) Inrush of magnetizing current may lead to inadvertent operation.
(d) Both (b) & (c)
Answer: -Option D
2. How many types of faults can occur in a system?
a) 2
b) 3
c) 5
d) Many
Answer: -Option D
3. System-short circuits may occur due to ________________
a) Line to line contacts
b) Line to neutral contacts if neutral is not earthed
c) Line to neutral contacts if neutral is earthed
d) LL and LG faults
Answer: -Option D
4. What are protection scheme for alternator
a) External Fault
b) Internal Fault
c) Line to neutral contacts if neutral is earthed
d) A and B
Answer: -Option D
5. What are stator winding fault for alternator
a) Line to line fault
b) Line to earth fault
c) Interturn fault
d) all of above
Answer: -Option D
6. What is the abnormal condition in stator winding?
a) Thermal overloading
b) unbalance loading
c) over voltage
d) all of above
Answer: -Option D
7. What is the abnormal condition in stator winding?
a) Thermal overloading
b) unbalance loading
c) over voltage
d) loss of excitation
Answer: -Option d
8. What is the mechanical abnormal condition in alternator?
a) loss of prime mover
b) over speeding
c) dame to prime mover
d) all of above
Answer: -Option d
9. In large generators protection provided against external faults is
A. Inter-turn fault protection
B. Sensitive earth fault protection
C .Biased differential protection
D .All of the above
Answer: -Option D
10. What are rotor winding fault for alternator
a) Line to line fault
b) Line to earth fault
c) Interturn fault
d) b and c both
Answer: -Option D
11. What is cause of loss of excitation?
a) Sudden opening of field switch
b) Line to earth fault
c) Interturn fault
d) winding heating
Answer: -Option A
12. Transformers are subjected to transients because _________________
a) open-circuit currents
b) short-circuit currents
c) inrush currents
d) both OC and SC currents
Answer: -Option D
13. In Merz-Price differential protection of a delta star transformer, the CT secondary’s connection
in the primary and secondary winding of the transformer would be in the form of
A. Delta star
B. Star delta
C. Delta delta
D. Star star
Answer: -Option B
14. Which kind of protection scheme employed for over load
A. Thermal Over load relays
B. Temperature relay
C. horn gaps
D. both A and B
Answer: -Option D
15. Which kind of protection scheme employed for Earth Fault
A. differential protection
B. earth fault relay
C. horn gaps
D. both C and B
Answer: -Option D
16. Factors consider for transformer protection
A. kva raiting
B. voltage and current ratio
C. Transformer connection type
D. all of above
Answer: -Option D
17. In an alternator one of the advantages of distributing the winding is to
a) Improve voltage waveform
b) Reduce noise
c) Same on copper
d)Reduce harmonics
Answer: -Option A
18. In large generators protection provided against external faults is
a) Inter-turn fault protection
b) Sensitive earth fault protection
c) Biased differential protection
d) All of the above
Answer: -Option D
19. Due to which of the following reasons, for aircraft alternators high frequency is used
a)To reduce the bulk
b) To compensate for high speeds
c) To compensate for high altitudes
d) To free the systems from external distribuance
Answer: -Option A
21. The permissible duration for which a generator of rated frequency 50Hz can at 46 Hz is
a) One cycle
b) One second
c) One minute
d) Zero
Answer: -Option B
22. In an alternator the voltage of field system is usually
a) More than 1000 V
b) Between 400 V and 600 V
c) Less than 200 V
d) None of the above
Answer: -Option C
23. In an alternator field the effect of cross-magnetization is to make the output
a) Non-sinusoidal
b) True sinusoidal
c) Free from harmonics
d) None of the above
Answer: -Option A
24. When two alternators are running in exact synchronism, the synchronizing power will be
a) Unity
b)Zero
c) Sum of the output of two
d) None of the above
Answer: -Option B
25. The power factor of an alternator is determined by it
a) Excitation
b) Speed
c) Prime mover
d) None of the above
Answer: -Option D
26. If two alternators are running in parallel and the excitation of one of the alternators is increased,
then
a) Power output will decrease
b) Wattless component will change
c) Machine with excess excitation will burn
d) Both machines will start vibrating
Answer: -Option B
27. When an alternator is supplying unity power factor load, the armature reaction will produce
a) Distortion of the main field
b) Magnetization of the main field
c) Demagnetization of the main field
d) None of the above
Answer: -Option A
28. Turbo-alternators are generally used to run at
a) 1500 r.p.m.
b) 3000r.p.m.
c) 5000 r.p.m.
d) 15000 r.p.m.
Answer: -Option B
29. In the case of turbo-alternators the rotor is usually made of
a) Cast iron
b) Forged steel
c) Laminated stainless steel
d) Manganese steel
Answer: -Option B
30. The number of poles in turbo-alternators is usually
a) 2
b) 4
c) 12
d) 50
Answer: -Option A
31. What kind of rotor is most suitable for turbo-alternators which are designed to run at high speed
a) Salient pole type
b) Non-salient pole type
c) Inversely proportional to its upper 3dB frequency
d) None of the above
Answer: -Option B
32. For a given output steam turbo-alternators are much smaller is size than water turbine -
alternators because
a) Steam turbo-alternators are built with smaller capacities
b) Steam turbo-alternators have long rotors
c) Steam turbo-alternators run at high speed
d) All of the above
Answer: -Option B
33. Salient pole type alternators are generally used on
a)Low voltage alternators
b) Hydrogen cooled prime movers
c) High speed prime movers
d) Low and medium speed prime movers
Answer: -Option B
33. The speed of a salient pole machine is nearly
a) 500 r.p.m.
b) 1000 r.p.m.
c) 1500 r.p.m.
d) 3000 r.p.m.
Answer: -Option A
05 – Protection of Motor, Bus-bar & Transmission Line Marks:-12
Content of Chapter:-
5.1Protection of Motor
5.2 Abnormalities & faults
5.3 Short circuit protection, Overload protection, Single phase preventer- (circuit diagram, operation)
Protection of Busbar& Transmission Line
5.4 Abnormalities & faults
5.5 Bus Bar Protection – Operation of Differential Protection and Fault bus protection schemes
5.6 Transmission line, over current, distance protection. Pilot wire protection
5.7. Differential protection: over current, earth fault, overheating and field failure protection.
5.8. Reverse power protection.
1. Suggest protective scheme for overloading of motor
a) Electromagnetic release
b) Overload release
c) MCB
d) All of above
Answer: -Option d
2. Suggest protective scheme for single phasing
a) Single phase preventer
b) Overload release
c) MCB
d) All of above
Answer: -Option d
3. Suggest protective scheme for un-balance supply
a) Negative phase sequently relay
b) Overload release
c) MCB
d) all of above
Answer: -Option d
4. Suggest protective scheme for stator side faults
a) HRC fuse
b) instantaneous over current relay
c) differential protection
d) all of above
Answer: -Option d
5. Suggest protective scheme for rotor side faults
a) HRC fuse
b) instantaneous over current relay
c) differential protection
d) all of above
Answer: -Option b
6. the voltage drop, for constant voltage transmission is compensated by installing
a). inductors
b). capacitors
c). synchronous motor
d). all of the above
Answer: -Option c
7. Minimum faults occur in which of the following power system equipment?
a) Transformer
b) Switch gear
c) CT, PT
d) Alternator
Answer: -Option d
8. Which of the following characteristics should the line supports for transmission line possess?
a) low-cost
b) High mechanical strength
c.) longer life
d.) all of the above
Answer: -Option D
9. When a line-to-line fault occurs, the short circuit current of an alternator depends upon its
a) Sub transient reactance
b) Transient reactance
c) Synchronous reactance
d) Short circuit reactance
Answer: -Option c
10. Transmission line insulators are made of
a). glass
b) Porcelain
c). iron
d.) p.v.c.
Answer: -Option b
11.In which portion of the transmission system is the occurrence of the fault more common?
a) Alternators
b) Transformers
c) Transmission lines
d.)Underground cables
Answer: -Option c
12. Which among these is the most severe fault?
a) Single line to ground fault.
b) Double line to ground fault
c). Line to line fault
d) Symmetrical fault.
Answer: -Option d
13. On which among the following factors does the magnitude of the fault current depend?
a)Total impedance upto the fault.
b) Voltage at the fault point
c) Both (a) and (b)
d.) None of these
Answer: -Option c
14. Which of the following fault results into a three phase faults?
a) Single line to ground fault.
b) Double line to ground fault
c) Line to line fault
d.)Fault due to all the three phases to earth.
Answer: -Option d
15. Fault diverters are basically
a) Circuit breakers
b) Fast switches
c) Relays
d) Fuses
Answer: -Option b
16. Which of thermal protection switch is provided in power line system to protect against?
a) Over voltage
b) Short circuit
c) Temperature rise
d) Overload
Answer: -Option d
17. For a transmission line the standing wave ratio is the ratio of
a) Peak voltage to rms voltage
b).maximum current to minimum current
c) Maximum voltage to minimum voltage
d.)Maximum impedance to minimum impedance
Answer: -Option c
18. What voltage of On-load tap-changer is required for unit transformer?
a) 11 kV
b) 23 kV
c) 400 kV
d) Not required
Answer: -Option d
19. for limiting the short circuit current
a) Reactors are used
b) Resistors are used
c) Capacitors are used
d) any of above
Answer: -Option a
20. The power factor of the arc in a circuit breaker is
a) Zero leading
b) Zero lagging
c) Unity
d) any value from zero to unity
Answer: -Option c
21. Short circuit in any winding of the transformer is the result of
a) Mechanical vibration
b) insulation failure
c) loose connection
d) impulse voltage
Answer: -Option d
22. For which of negative sequence current is provided
a) Generator
b) motor
c) transmission line
d) transformer
Answer: -Option d
23. Relay is prefferd for phase fault or short transmission line
a) Induction type
b) reactance
c) impedance
d) none of the above
Answer: -option b
24. Raiting of transformer differential protection is recommended
a) Above 30 kva
b) equal and above 5 mva
c) equal and above 25 mva
d) equal and above 55 mva
Answer: - option b
25. Under voltage relay can be used for
a) generator
b) bus bar
c) transformer
d) all of above
Answer: - option d
26. Single phasing relay are used for protecton of
a) single phase motor only
b) two phase motor only
c) two single phase motor running in parallel
d) three phase motor
Answer: - option d
27. Which of the parameter can be neglected for short line?
a) Inductance
b) capacitance
c) resistance
d) all of above
Answer: - option d
28. Transmission line has reflection coefficient as on
a)open circuit
b) short circuit
c) long
d) none of above
Answer: - option d
29. 400 kV power system are design operate in
a)100 mic sec
b) 50 mic sec
c) 0.5 sec
d) 0.1 sec
Answer: - option b
30. Series capacitor are used to
a) Compensate line inductive reactance
b) Compensate for line capacitance reactance
c) improve line voltage
d) none of the above
Answer: - option a
31. Torque produced induction induction type relay
a)inversely proportional to the current
b) inversely proportional to square of current
c) proportional to the current
d) all of the above
Answer: - option b
32. Power loss is important factor for the design of
a) Transmission line
b) motor
c) generator
d) feeder
Answer: - option a
33. Power loss is important factor for the design of
a) Transmission line
b) motor
c) generator
d) feeder
Answer: - option a
34. Oil switched are employed for
a) Low current circuit
b) low voltage circuit
c) high voltage and large current circuit
d) feeder
Answer: - option a
35. Relay can be designed to respond to changes in
a) Resistance reactance or impedance
b) voltage and current
c) light intensity
d) all of above
Answer: - option d
36. The relay with inverse time characteristics will operate within
a) 1.5 sec
b) 5 to 10 sec
c) 5 to 20 sec
d) 20 to 30 sec
Answer: - option b
37. The inverse definite mean time relays are used for over current and earth fault protection of
transformer against
a) Heavy loads
b) Internal short circuits
c) External short circuits
d) All of the above
Answer: -option b
38. static over current relay, inverse time characteristic are obtained by
A) Transistor amplifier
b) internal short circuits
c) A transistor switch
d) a differentiating circuit
Answer: - option b
39. In the case of transmission line protection, over current relay is used
a) Only upto 110 kV
b) only upto 120 kV
c) only upto 50 kV
d) only up to 1100 KV
Answer: - option c
40. The domains of power system where directional over current relay is indispensable are
a) In case of parallel feeder protection
b) in case of ring main feeder protection
c) Both A and B
d) none of the above
Answer: - option c
41. Impedance relay can be used for
a) Phase faults only
b) Earth faults only
c) Both earth and phase faults
d) None of the above
Answer: - option a
42. Impedance relay may use
a) Balance beam structure
b) Induction cup structure
c) Shaded pole structure
d) Either A or B
Answer: - either A OR B
43. the most commonly used method for the protection of three phase feeder is
a) Time graded protection
b) Differential protection
c) Reverse power protection
d) none of the above
Answer: - option B
44. Which is the pilotless protection method for feeder line?
a)Differential protection
b) Carrier current protection
c) Time credit protection
d) none of the above
Answer: - option B
45. Time graded protection of a radial feeder can be achieved by using
a)Definite time relay
b) Inverse time relay
c) Both definite and inverse time relays
d) None of the above
Answer: - option B
46. Problems associated with differential protection is/are
a)Magnetizing inrush current
b) Mismatching characteristics of CTs
c) Charge of ratio as a result of tapping
d) All of the above
Answer: - option d
47. for the protection of transformers, harmonic restraint is used to guard against
a) Magnetising inrush current
b) unbalanced operation
c) Lightning
d) switching over-voltage
Answer: - option d
48. The types of faults that occur in electric motors are
a)Stator
b) Rotor
c) Overload
d) All of the above
Answer: - option d
49. The frequency of carrier in the carrier current pilot scheme is in the range of
a) 1 kHz to 10 kHz
b) 10 kHz to 25 kHz
c) 25 kHz to 50 kHz
d) 50 kHz to 500 kHz
Answer: - option d
50. In carrier current protection the purpose of the wave trap is for
a) Trapping power frequency waves
b) Trapping high frequency waves entering into generators/ transformer unit
c) Both a and b
d) None of the above
Answer: - option B
51. Directional relays responds to
a) Power
b) Voltage
c) Current
d) Reactance
Answer: - option C
52. for motor protection, which relay is used?
a) Thermocouple type relays
b) Bimetallic relays
c) Electronic relays
d) All of these
Answer: - option D