400 Important Switchgear and Protection MCQ Question and Answer | PDF Free Download
1.Where voltages are high and current to be interrupted is low, the circuit breaker preferred is
- AAir-break
- BVacuum
- COil
- DAir-blast
2.The circuit breaker preferred for rural electrification in a country like India with complex network is
- AAir-break
- BOil
- CVacuum
- DMinimum oil
3.The most suitable circuit breaker for short line fault without switching resistor is
- AMinimum oil
- BAir-blast
- CSulphur hexafluoride
- DAir-break
4.The rating of a circuit breaker is usually determined on the basis of ___________ fault.
- ASymmetrical
- BLine to line
- CSingle line to ground
- DDouble line to ground
5.The transient phenomenon lasts in a power system for a period ranging from
- AFew ms to 1 s.
- B1 s to 2 s.
- C2 s to 3 s.
- DGreater than 3 s.
6.Circuit breakers usually operate under
- ASteady short-circuit current.
- BSub-transient state of short-circuit current.
- CTransient state of short-circuit current.
- DNone of these.
7.The re-striking voltage is measured in
- ARMS value
- BPeak value
- CInstantaneous value
- DAverage value
8.The making and breaking currents of 3-phase ac circuit breakers in power system are respectively in what form ?
- ARms value, rms value
- BInstantaneous value, rms value
- CRms value
- DInstantaneous value, Instantaneous value
9.Rated breaking capacity (MVA) of a circuit breaker is equal to
- AThe product of rated breaking current (kA) and rated voltage (kV).
- BThe product of rated symmetrical breaking current (kA) and rated voltage (kV).
- CThe product of breaking current (kA) and fault voltage (kV).
- DTwice the value of rated current (kA) and rated voltage (kV).
10.The making to breaking current ratio for an EHV circuit breaker is
- AMore than 1.
- BEqual to 1.
- CLess than 1.
- DA negative number
11.The making capacity of a circuit breaker is
- ALess than the symmetrical breaking capacity of the breaker.
- BGreater than the symmetrical breaking capacity of the breaker.
- CEqual to the symmetrical breaking capacity of the breaker.
- DEqual to the symmetrical breaking capacity.
12.A three-phase, 33 kV oil circuit breaker is rated 1200 A. 2000 MVA, 3 s. the symmetrical breaking current is
- A1,200 A
- B3,600 A
- C35 kA
- D104.8 kA
13.A three-phase breaker is rated 2,000 MVA, 33 kV. Its making current will be
- A35 kA
- B49 kA
- C70 kA
- D89 kA
14.Which of the following statements is not correct?
- AArc chutes are used in air break circuit breakers.
- BAir-blast circuit breakers are employed for high voltage traction system.
- CResistance switching is employed for overcoming current chopping.
- DLinear resistors are used in resistance switching.
15.Capacitor switching in 33 kV power system is breaker done with ?. Circuit breakers.
- AAir-blast
- BMinimum oil
- CVacuum
- DNone of the above
16.The probable causes for fall in insulation resistance between phase terminal and earthed frame could be
- ADirty insulation surface
- BIngress of moisture
- CSticking of carbon or copper particles to the internal surface
- DAll of the above
17.The probable causes for failure of a circuit breaker on electrical compound could be
- ATrip circuit open
- BTrip latch defective
- CSpring defective
- DAny of the above
18.Routine tests are conducted on
- ABulk oil circuit breakers
- BMinimum oil circuit breakers
- CAir-blast circuit breakers
- DAll of the above
19.An isolator is installed
- ATo isolate one portion one portion of the circuit from another.
- BUsually on both sides of a circuit breaker.
- CAs a substitute for a circuit breaker.
- DBoth (a) and (b)
20.Current rating is not necessary in case of
- AIsolators.
- BCircuit breakers.
- CLoad break switches.
- DCircuit breakers and load break switches.