Switch Gear and Protection 3

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Electrical Engineering MCQ Question Papers: Campus Placement

Subject: Switch Gear and Protection 3

Part 3: List for questions and answers of Switch Gear and Protection


Q1. Which material is used in the liquid type of fuse?

a) SF6

b) Distilled water

c) Carbon tetra chloride

d) Mineral oil/transformer oil


Q2. In a HRC fuse what is the time between the cut off and the final current zero called?

a) Pre-arcing time

b) Arcing time

c) Total operating time

d) None of these


Q3. Upto what voltage a cartridge type of fuse can be used?

a) 400V

b) 11kV

c) 20kV

d) 33kV


Q4. On what basis is the selection of fuse done?

a) Steady load

b) Fluctuating load

c) Both (a) and (b)

d) None of these


Q5. What is the main advantage of using a fuse?

a) Cheapest type of protection

b) Inverse time current characteristics

c) Current limiting effect under short circuit conditions

d) All of above


Q6. Upto what voltage can the liquid type HRC fuses be used?

a) 33kV

b) 132kV

c) 66kV

d) 220kV 


Q7. When a fault occurs in a high voltage transmission line, what happens first?

a) Circuit breaker operates then the relay

b) Relay operates and then the circuit breaker

c) Relay operates, then successively the isolator and the circuit breaker

d) Isolator operates, then successively the relay and the circuit breaker


Q8. Which part of the circuit breaker is helpful in breaking the current?

a) Trip coil

b) Contacts

c) Medium

d) Handle


Q9. Which type of tripping is generally preferred for the circuit breaker?

a) Manual

b) Automatically

c) Depending on the voltage level

d) None of the above


Q10. The arc resistance depends on which among the following factors?

a) Cross section of the arc

b) Length of the arc

c) Degree of ionization

d) All of the above


Q11. How is the initiation of electric arc at the instant of contact separation caused?

a) Thermionic emission of electrons

b) Field emission of electrons

c) Both (a) and (b)

d) None of these


Q12. Arcing voltage will be the least in case of

a) Carbon

b) Copper

c) Silver

d) Tungsten


Q13. What is the arc voltage in a circuit breaker?

a) In phase with the arc current

b) Lagging the arc current by 90 degree

c) Leading the arc current by 90 degree

d) Lagging the arcing current by 180 degree 


Q14. What happens in the arc extinction using high resistance method?

a) Arc resistance is decreased with time

b) Arc resistance is increased with time

c) No change it remains same

d) Arc resistance is kept zero


Q15. By using low resistance method for arc extension what is the value of arc resistance?

a) Arc resistance is zero

b) Arc resistance is hig

c) Arc resistance is low

d) Arc resistance is very high


Q16. The resistance of an electric arc can be increased by

a) Increasing the concentration of ionised particles

b) Reducing the arc length

c) Splitting the arc

d) Increasing the arc cross section


Q17. The heat produced at the contact point owing to flow of electric current is least

affected by_____

a) Temperature of the surrounding medium

b) Contact resistance

c) Magnitude of electric current flowing

d) Duration of flow of current


Q18. Which of the following should have low value for the contacts and their material?

a) Thermal capacity

b) Contact resistance

c) Thermal conductivity

d) None of above


Q19. In a circuit breaker, ionisation is facilitated by_____

a) Increase in field strength

b) Increase in mean free length

c) High temperature of the surrounding medium

d) All of the above 


Q20. In a circuit breaker the contact space is ionised by what?

a) Field emission from the contact surface

b) Thermal emission from the contact surface

c) Thermal ionisation of gas

d) All of above 


Part 3: List for questions and answers of Switch Gear and Protection


Q1. Answer: c


Q2. Answer: b


Q3. Answer: d


Q4. Answer: c


Q5. Answer: d


Q6. Answer: b


Q7. Answer: b


Q8. Answer: b


Q9. Answer: b


Q10. Answer: d


Q11. Answer: c


Q12. Answer: c


Q13. Answer: a


Q14. Answer: b


Q15. Answer: c


Q16. Answer: c


Q17. Answer: a


Q18. Answer: b


Q19. Answer: d


Q20. Answer: c