Top 250+ Solved Testing and Commissioning of Electrical Equipment’s MCQ Questions Answer
Q. For a high speed circuit breaker what will the total clearing time?
a. Few minutes.
b. Few seconds.
c. 1 to 2 cycles.
d. 5 to 20 cycles.
Q. The interrupting time of a circuit breaker is the period between the instant of_________.
a. Initiation of short circuit and the arc extinction on an opening operation.
b. Energizing the trip circuit and the arc extension on an opening operation.
c. Initiation of short circuit and the parting of primary arc contacts.
d. Energizing of the trip circuit and the parting of primary arc contacts.
Q. 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.
Q. 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.
Q. The heat produced at the contact point owing to flow of electric current is leastaffected by_____________________.
a. Temperature of the surrounding medium.
b. Contact resistance.
c. Magnitude of electric current flowing.
d. Duration of flow of current.
Q. 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 ar(C)
d. Increasing the arc cross section.
Q. By using low resistance method for arc extension what is the value of arcresistance?
a. Arc resistance is zero.
b. Arc resistance is high
c. Arc resistance is low
d. Arc resistance is very high
Q. 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.
Q. What is the arc voltage in a circuit breaker?
a. In phase with the arc current.
b. Lagging the arc current by 90°
c. Leading the arc current by 90°
d. Lagging the arcing current by 180°
Q. 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.
Q. The arc resistance depends on which among the following factors?
a. Cross section of the ar(C)
b. Length of the ar(C)
c. Degree of ionization
d. All of the above.
Q. 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
Q. Which part of the circuit breaker is helpful in breaking the current?
a. Trip coil.
b. Contacts.
c. Medium
d. Handle.
Q. 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.