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- Switchgear & Protection Test Question - Set 3
MCQs 1: For a high speed circuit breaker what will the total clearing time?
MCQs 2: What is restriking voltage?
The transient voltage that appears across the circuit breaker contacts at the instant of arc extinction.
The transient voltage that appears across the circuit breaker contacts at the end of arc extinction.
Both (a) and (b)
None of the above
MCQs 3: In a circuit breaker, the active recovery voltage depends upon which among these?
MCQs 4: On what factor does the rate of rise of restriking voltage (RRRV) depend?
MCQs 5: Rate of rise of restriking voltage depend on_____________?
Type of circuit breaker.
Capacitance of the system.
Inductance of the system
Both (b) and (c)
None of these
MCQs 6: The stability of arc in vacuum depends on _________.
The contact material only.
The circuit parameters only.
The contact materials and its vapour pressure.
Both (b) and (c)
None of these
MCQs 7: Why is it difficult to interrupt a capacitive circuit?
The current has a leading power factor.
The restriking voltage can be high.
Current magnitude is very small.
Stored energy in the capacitor is very high.
MCQs 8: Recovery voltage is the value of rms voltage that reappears across the poles of a circuit breaker before_______________
MCQs 9: What is the interrupting medium in the contactor?
MCQs 10: How is the restriking voltage measured?
MCQs 11: The making and breaking currents of a 3 phase ac circuit breakers in power systems are respectively in ________form.
rms value, rms value
instantaneous value, rms value
rms value, instantaneous value
instantaneous value, instantaneous value
MCQs 12: In a short circuit test on a circuit breaker, the following readings were obtained on single frequency transients a. Time to reach the peak re striking voltage - 50μ sec b. The peak re striking voltage, 100 kV what will be the frequency of oscillations?
MCQs 13: Refer to the following facts to answer the question, A 50 Hz, 11 kV, 3 phase alternator with earthed neutral having a reactance of 3 ohms per phase and is connected to a bus bar through a circuit breaker, if the distributed capacitance upto CB between the phase and neutral is 0.01 μ F. What is the peak re striking voltage?
MCQs 14: Refer to the following facts to answer the question A 50 Hz, 11 kV, 3 phase alternator with earthed neutral having a reactance of 3 ohms per phase and is connected to a bus bar through a circuit breaker, if the distributed capacitance upto CB between the phase and neutral is 0.01 μ F. What is the frequency of oscillations?
MCQs 15: A 50 Hz 3 phase synchronous generator has inductance per phase of 15mH. The capacitance of generator and the circuit breaker is 0.002μ F. What is the natural frequency of oscillation?
MCQs 16: When using air blast circuit breaker, current chopping is a phenomenon observed when
A long overhead line is switched off.
A bank of capacitors is switched off.
A transformer on no load is switched off.
A heavy load is switched off.
MCQs 17: Why is the resistance switching used in a air blast circuit breaker?
Reduce the magnitude of fault current.
Control the CB operating time.
Damp out the fast transient.
Change the fault current power factor.
MCQs 18: What is the type of air blast in cross blast type CB?
The blast of air is along the arc.
The blast of air cuts across the arc.
Both (a) and (b)
None of the above.
MCQs 19: The air blast circuit breakers for 400 kV systems are designed to operate in how much time?
MCQs 20: In axial blast type of CB, expansion of air takes place from ______________.
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