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Switchgear and Protection

Study 102 Electrical Engineering MCQs with correct answers and explanations.

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41Electrical EngineeringMedium

Air blast circuit breaker is used for________?

Ashort duty

Bintermittant duty

Crepeated duty

Dover currents

Correct answer

C. repeated duty

Explanation

The correct answer is repeated duty.

42Electrical EngineeringMedium

Circuit breakers usually operate under________?

Aafter D.C. component has ceased

Bsub-transient state of short-circuit current

Csteady state of short-circuit current

Dtransient state of short-circuit current

Correct answer

D. transient state of short-circuit current

Explanation

The correct answer is transient state of short-circuit current.

43Electrical EngineeringMedium

Which of the following is the least expensive protection for overcurrent is low voltage system?

AAir break circuit breaker

BOil circuit breaker

CNone of the above

DRewireable fuse

EIsolator

Correct answer

D. Rewireable fuse

Explanation

The correct answer is Rewireable fuse.

44Electrical EngineeringMedium

The voltage appearing across the contacts after opening of the circuit breaker is called________voltage

Arecovery

Barc

Cnone of the above

Dsurge

Eoperating

Correct answer

A. recovery

Explanation

The correct answer is recovery.

45Electrical EngineeringMedium

The contacts of high voltage switches used in power system are submerged in oil. The main purpose of the oil is to________?

Aextinguish the arc

Blubricate the contacts

Cnone of the above

Dall of the above

Einsulate the contacts from switch body

Correct answer

A. extinguish the arc

Explanation

The correct answer is extinguish the arc.

46Electrical EngineeringMedium

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?

AInfinity

BNone of the above

CUnity

DZero

Correct answer

D. Zero

Explanation

The correct answer is Zero.

47Electrical EngineeringMedium

The short circuit in any winding of the transformer is the result of________?

Aloose connection

Bimpulse voltage

Cinsulation failure

Dmechanical vibration

Correct answer

B. impulse voltage

Explanation

The correct answer is impulse voltage.

48Electrical EngineeringMedium

Protective relays are devices that detect abnormal conditions in electrical circuits by measuring________?

Aconstantly the electrical quantities which differ during normal and abnormal conditions

Bvoltage during abnormal condition

Cnone of the above

Dcurrent during abnormal condition

Correct answer

A. constantly the electrical quantities which differ during normal and abnormal conditions

Explanation

The correct answer is constantly the electrical quantities which differ during normal and abnormal conditions.

49Electrical EngineeringMedium

H.R.C. fuse, as compared to a rewirable fuse, has________?

Aall of the above

Bno ageing effect

Chigh rupturing capacity

Dhigh speed of operation

Correct answer

A. all of the above

Explanation

The correct answer is all of the above.

50Electrical EngineeringMedium

SF6 gas________?

Anone of the above

Bis nontoxic

Cis lighter than air

Dhas pungent small

Eis yellow in colour

Correct answer

B. is nontoxic

Explanation

The correct answer is is nontoxic.

Protective relays are devices that detect abnormal conditions in electrical circuits by measuring________?

Aconstantly the electrical quantities which differ during normal and abnormal conditions

Bvoltage during abnormal condition

Cnone of the above

Dcurrent during abnormal condition

Correct answer

A. constantly the electrical quantities which differ during normal and abnormal conditions

Explanation

The correct answer is constantly the electrical quantities which differ during normal and abnormal conditions.