Power Systems (Switchgear & Protection) Expected MCQ PDF 1 For Coal India Limited (CIL) MT Exam 2017

1)   What is / are the main disadvantage of using oil as the quenching medium in the circuit breakers?

a. Need periodical replacement.
b. Risk of formation of explosive mixture with air.
c. Possibility of causing fire hazards.
d. All of the above.

ANSWER: All of the above.

2)   A three
phase, 33 kV oil circuit breaker is rated 1200 A, 2000 MVA, 3s. What is
its symmetrical breaking current?

a. 1200 A
b. 3600 A
c. 35 kA
d. 104.8 kA

ANSWER: 35 kA

3)   A thermal protection switch provides protection against what?

a. Overload
b. Temperature
c. Short circuit
d. Over voltage

ANSWER: Overload

4)   Which of the following circuit breakers is used for the railway electrification?

a. Air blast circuit breaker
b. SF6 circuit breaker
c. Bulk oil circuit breaker
d. Minimum oil circuit breaker

ANSWER: Air blast circuit breaker

5)   Which circuit breaker is preferred to be installed in extra high voltage AC system?

a. Bulk oil type circuit breaker
b. Air blast circuit breaker
c. SF6 circuit breaker
d. Vacuum circuit breaker

ANSWER: SF6 circuit breaker

6)   Which among these circuit breakers produce the least arc energy?

a. Plain oil
b. Minimum oil
c. Air blast
d. Air break

ANSWER: Air blast

7)   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: Symmetrical

8)   Which of the following circuit breaker is highly reliable and has a least maintenance?

a. Oil circuit breakers
b. Air blast
c. Vacuum circuit breakers
d. SF6 circuit breakers

ANSWER: SF6 circuit breakers

9)   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
d. None of these

ANSWER: Sub transient state of short circuit current

10)   What is the making capacity of the circuit breaker?

a. Less than the asymmetrical breaking capacity of the breaker
b. Greater than the asymmetrical breaking capacity of the breaker
c. Equal to the asymmetrical breaking capacity of the breaker
d. Equal to the symmetrical breaking capacity of the breaker

ANSWER: Greater than the asymmetrical breaking capacity of the breaker

11)   A three phase circuit breaker is rated 2000 MVA, 33 kV. What will be its making current?

a. 35 kA
b. 49 kA
c. 70 kA
d. 89 kA

ANSWER: 89 kA

12)   The breaking capacity of a three phase circuit breaker is given by

a. Service line voltage * rated symmetrical current in amperes * 10-6 MVA
b. √3 * Service line voltage * rated symmetrical current in amperes * 10-6 MVA
c. 1.1* Service line voltage * rated symmetrical current in amperes * 10-6 MVA
d. √2 * Service line voltage * rated symmetrical current in amperes * 10-6 MVA

ANSWER: √3 * Service line voltage * rated symmetrical current in amperes * 10-6 MVA

13)   Assertion
(A): In comparison to making capacity of a circuit breaker its breaking
capacity is normally higher.
Reason (R): The breaking capacity of a CB is expressed as √3 * VI * 10-6 MVA

a. Both A and R are true and R is the correct explanation of A
b. Both A and R are true and R is not the explanation of A
c. A is true but R is false
d. A is false but R is true.

ANSWER: A is false but R is true.

14)   What is the making to breaking current ratio for an extra high voltage circuit breaker?

a. More than 1
b. Equal to 1
c. Less than 1
d. A negative value

ANSWER: More than 1

15)   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)
e. None of these

ANSWER: To isolate one portion of the circuit from another

16)   For which among the following the current ratings are not required?

a. Circuit breakers
b. Relays
c. Isolators
d. Load break switch

ANSWER: Isolators

17)   The isolators used in the transmission lines are capable of breaking

a. Fault current
b. No current
c. Charging current
d. Load current

ANSWER: Charging current

18)   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: Breaking the circuit under no load condition

19)   What is the major cause of the failure of the circuit breaker?

a. Trip circuit open
b. Trip latch defective
c. Spring defective
d. All of these

ANSWER: All of these

20)   What is the purpose of back up protection?

a. To increase the speed
b. To increase the reach
c. To leave no blind spot
d. To guard against failure of primary

ANSWER: To guard against failure of primary

21)   What is the actuating quantity for the relays?

a. Magnitude
b. Frequency
c. Phase angle
d. All of these

ANSWER: All of these

22)   Protective relays can be designed to respond to ___________.

a. Light intensity, impedance
b. Temperature, resistance, reactance
c. Voltage and current
d. All of these

ANSWER: All of these

23)   On what factor does the operating speed of the relay depend?

a. Rate of flux built up
b. Armature core air gap
c. Spring tension
d. All of these

ANSWER: All of these

24)   In the
following figure, the relay circuit is divided into three parts. What
does the first part consist of?

a. Primary winding of a current CT which is connected in series with the line to be protected.
b. Secondary of the CT and the operating coil.
c. Tripping circuit.
d. None of these

ANSWER: Primary winding of a current CT which is connected in series with the line to be protected.

25)   In the
following figure, the relay circuit is divided into three parts. What
does the third part consist of?

a. Primary winding of a current CT which is connected in series with the line to be protected.
b. Secondary of the CT and the operating coil.
c. Tripping circuit.
d. None of these

ANSWER: Tripping circuit.

26)   In the following figure, which component ensures the safety of the line from damage?

a. Relay
b. Circuit breaker
c. Bus bar
d. Current transformer

ANSWER: Relay

27)   In the following figure, the tripping circuit is__________.

a. AC
b. DC
c. Either AC or DC
d. None of these

ANSWER: Either AC or DC

28)   Plug setting of a electromagnetic relay can be altered by varying

a. Number of ampere turns
b. Air gap of magnetic path
c. Adjustable back stop
d. None of these

ANSWER: Number of ampere turns

29)   The most efficient torque producing actuating structure for the induction type relays is

a. Shaded pole structure
b. Watt hour meter structure
c. Induction cup structure
d. Single induction loop structure

ANSWER: Induction cup structure

30)   Which of the following circuit breakers has the lowest operating voltage?

a. SF6 circuit breaker
b. Air break
c. Air blast
d. Minimum oil circuit breaker

ANSWER: Air break

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QUIZ OF DAY-10/03/2017 GK & CURRENT AFFAIRS
Signals & Systems Expected MCQ PDF 1 For Coal India Limited (CIL) MT Exam 2017

4 Comments

  1. Abhijit
    • Harikesh Yadav
  2. Abhijit
    • Harikesh Yadav

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