Top 250+ Solved Testing and Commissioning of Electrical Equipment’s MCQ Questions Answer
Q. When does the arc interruption in oil circuit breaker take place?
a. Contacts apart.
b. Voltages becomes zero
c. Current goes through zero
d. All of the above
Q. For rural electrification in India, which circuit breaker is generally used?
a. Oil
b. SF6
c. Vacuum
d. Air blast
Q. Keeping in view the cost and the overall effectiveness, which of the following circuit breaker is best suited for capacitor bank switching?
a. Vacuum circuit breaker
b. Air blast CB
c. SF6
d. Oil CB
Q. To limit current chopping in vacuum circuit breakers, the contact material employed should have the properties of
a. Low conductivity and high vapour pressure.
b. Low conductivity and low vapour pressure.
c. High conductivity and high vapour pressure.
d. High conductivity and low vapour pressure.
Q. SF6 gas is imported in _____________.
a. Air cylinders
b. Gas cylinders
c. Liquid form in cylinders
d. Solid form.
Q. During arc extinction SF6 gas gets converted to which among these?
a. Gets decomposed to SF4 and SF2
b. Gets decomposed to S and F
c. Gets reduced to SF6
d. Gets oxidized
Q. What is the most important property which makes the SF6 very efficient medium for circuit breaking?
a. Is non toxic and non inflammable.
b. Has a high dielectric constant.
c. Has a high breakdown strength
d. Is highly electronegative gas
Q. What is the normal pressure at which the SF6 gas is maintained in the closed position of the breaker?
a. 2 kg / cm2
b. 2.5 kg /cm2
c. 2.8 kg / cm2
d. 3 kg / cm2
Q. What is the major drawback of using SF6 circuit breakers?
a. Sealing problems of the gas.
b. Ingress of moisture in the gas system – dangerous.
c. Deterioration of SF6 gas with time.
d. Both (a) and (b)
Q. Why do the SF6 gases have an excellent heat transfer property?
a. Low gaseous viscosity.
b. High dielectric strength.
c. Higher molecular weight.
d. Both (a) and (c)
Q. What is the breaking capacity of the air blast circuit breaker?
a. 5000 MVA
b. 6000 MVA
c. 7000 MVA
d. 10000 MVA
Q. In axial blast type of CB, expansion of air takes place from ______________.
a. High pressure to low pressure.
b. Low pressure to high pressure.
c. Always in high pressure.
d. Always in low pressure.
Q. The air blast circuit breakers for 400 kV systems are designed to operate in howmuch time?
a. 0.1 s
b. 0.5 s
c. 50 ms
d. 100µs
Q. What is the type of air blast in cross blast type CB?
a. The blast of air is along the ar(C)
b. The blast of air cuts across the ar(C)
c. Both (a) and (b)
d. None of the above.
Q. Why is the resistance switching used in a air blast circuit breaker?
a. Reduce the magnitude of fault current.
b. Control the CB operating time.
c. Damp out the fast transient.
d. Change the fault current power factor.