Air Blast Circuit Breaker - MCQs with answers

Air Blast Circuit Breaker - MCQs with answers

Q1. Which type of air is used in air blast circuit breaker?

a. Ionised air
b. Air free from moisture
c. Air should have least CO₂
d. Air must have oil mist.

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Q2. When using air blast circuit breaker, current chopping is a phenomenon observed when

a. A long overhead line is switched off.
b. A bank of capacitors is switched off.
c. A transformer on no load is switched off.
d. A heavy load is switched off.

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Q3. 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.

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Q4. What is the type of air blast in cross blast type CB?

a. The blast of air is along the arc.
b. The blast of air cuts across the arc.
c. Both (a) and (b)
d. None of the above.

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Q5. The air blast circuit breakers for 400 kV systems are designed to operate in how much time?

a. 0.1 s
b. 0.5 s
c. 50 ms
d. 100µs

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Q6. 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.

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Q7. What is the breaking capacity of the air blast circuit breakers?

a. 5000 MVA
b. 6000 MVA
c. 7000 MVA
d. 10000 MVA

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