MCQ on Control and Protection 2

MCQ on Control and Protection 2

1. Which of the following circuit breakers is preferred for EHT (Extra High Tension) applications?

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

2. Interrupting medium in a contactor may be

a. Air
b. Oil
c. SF6
d. Any of the above.

3. SF6 gas is

a. sulphur difluoride
b. sulphur hexafluoride
c. sulphur fluoride
d. sulphur hexafluorine

4. In air blast circuit breakers, the pressure of air is of the order of

a. 1 kg/cm²
b. 20 to 30 kg/cm²
c. 200 to 300 kg/cm²
d. 100 mm Hg

5. SF6, gas is

a. is yellow in color
b. is highly toxic
c. has pungent odor
d. is non-inflammable

6. The pressure of SF6, gas in circuit breakers is of the order of:

a. 1kg/cm²
b. 30 to 50 kg/cm²
c. 3 to 5kg/cm²
d. 100mm of Hg

7. SF6 is :

a. is lighter than hydrogen
b. is lighter than air
c. has density 2-times as compared to that of air
d. has density 5 limes as compared to that of air

8. Out of the following circuit breakers, which one has the lowest voltage range?

a. Air-break circuit breaker
b. Air-blast circuit breaker
c. Tank type oil circuit breaker
d. SF6, circuit break

Also View: MCQ on Control and Protection

9. While selecting a gas for the circuit breaker, the property of gas that should be considered is

a. high dielectric strength
b. all of the above
c. non-toxicity
d. non-inflammability

10. In modem EHV (Extra High Voltage) circuit breakers, the operating time between the instant of moving trip signal and final contact separation is, of the order of:

a. 0.001 sec
b. 0.015 sec
c. 0.003 sec
d. 0.03 sec

11. Fusing factor for an HRC fuse is

a. Minimum fusing current/Current rating
b. Minimum fusing current/Minimum rupturing time
c. Maximum fusing current/Minimum fusing current
d. Minimum fusing current/Prospective current of the circuit

12. Which of the following circuit breakers does not use a pneumatic operating

a. Air blast circuit breaker
b. Air break circuit breaker
c. SF, blast circuit breaker
d. Bulk-oil circuit breaker

13. In an HRC fuse time between cut-off and final current zero is known as:

a. Arcing time
b. Any of the above
c. Total operating time
d. Pre-arcing time

14.The contact resistance of a circuit breaker is of the order of :

a. 20 micro ohms± 10
b. 20 milli ohms ± 10
c. 200 ohms ± 10
d. 20 ohms ± 10

15. The insulation resistance of a high voltage circuit breaker is:

a. 10k ohm
b. 1k ohm
c. 2000 Mega ohm
d. 20 Mega ohm

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