Power Systems Expected MCQ PDF 1 Switchgear
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Attempt Free Power Systems Expected MCQ PDF 1 Switchgear Here. Read The Important Electrical MCQ From Below.
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
Power Systems Expected MCQ PDF 1 Switchgear
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
Power Systems Expected MCQ PDF 1 Switchgear
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
Power Systems Expected MCQ PDF 1 Switchgear
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
Power Systems Expected MCQ PDF 1 Switchgear
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
Power Systems Expected MCQ PDF 1 Switchgear
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
Power Systems Expected MCQ PDF 1 Switchgear
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
Power Systems Expected MCQ PDF 1 Switchgear
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
Power Systems Expected MCQ PDF 1 Switchgear
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
Power Systems Expected MCQ PDF 1 Switchgear
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
Power Systems Expected MCQ PDF 1 Switchgear
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
Power Systems Expected MCQ PDF 1 Switchgear
