400 Important Switchgear and Protection MCQ Question and Answer | PDF Free Download
1.The most serious consequence of a major uncleared short-circuit fault could be
- ABlowing of fuse
- BFire
- CHeavy voltage drop
- DNone of these
2.Which of the following results in a symmetrical fault?
- ASingle-phase-to earth
- BPhase-to-phase
- CAll the three phases-to earth
- DTwo phase-to earth
3.Which portion of the transmission system is more prone to faults?
- AAlternator
- BTransformer
- COverhead lines
- DUnderground cable
4.Which portion of the power system is least prone to faults?
- AAlternator
- BSwitchgear
- CTransformers
- DOverhead lines
5.The magnitude of fault current depends upon
- ATotal impedance up to fault
- BVoltage at the fault point
- CLoad current being supplied before occurrence of fault
- DBoth (a) and (b)
6.The most common type of fault is
- ASingle-phase-to ground
- BPhase-to-phase
- CTwo-phase-to ground
- DThree -phase-to ground
7.The maximum short-circuit current occurs in the case of :
- AThree-phase bolted fault
- BDouble-line-to-ground fault
- CLine-to-line fault
- DSingle-line-to-ground fault
8.For a fault at the terminals of synchronous generator, the fault current is maximum for a
- A3-phase fault
- B3-phase to ground fault
- CLine-to-ground fault
- DLine-to-line fault
9.Series reactors are used to
- AImprove the transmission efficiency
- BImprove the power factor of the power system
- CImprove the voltage regulation
- DBring down the fault level within the capacity of the switchgear
10.Current limiting reactors may be
- AAir-cored air-cooled
- BOil immersed magnetically shielded
- COil immersed non-magnetically shielded
- DAny of the above
11.Symmetrical components are used in power system for the analysis of
- ABalanced 3-phae fault
- BUnbalanced 3-phae fault
- CNormal power system under steady conditions
- DStability of system under disturbance
12.In a star-connected system without neutral grounding, zero sequence currents are
- AZero
- BPhasor sum of phase currents
- CSame as rms value of phase currents
- DSame as peak value of phase currents
13.A balanced 3-phase system consists of
- AZero-sequence currents only
- BPositive-sequence currents only
- CNegative-and zero-sequence currents
- DZero, Negative and Positive sequence currents
14.The Positive sequence current of a transmission line is :
- AAlways zero
- B1/3 of Negative sequence current
- CEqual to Negative sequence current
- D3 times Negative sequence current
15.For a fully transposed transmission line
- APositive, Negative and zero sequence impedances are equal.
- BPositive and Negative sequence impedances are equal.
- CZero and Positive sequence impedances are equal.
- DNegative and zero sequence impedances are equal.
16.In case of an unbalanced star-connected load supplied from an unbalanced 3-phase, 3-wire system, load current will consist of
- APositive-sequence components.
- BNegative-sequence components.
- CZero-sequence components.
- DOnly (a) and (b)
17.For an unbalanced fault, with paths for zero-sequence currents, at the point of fault
- AThe negative-and zero-sequence voltages are minimum.
- BThe negative-and zero-sequence voltages are maximum.
- CThe negative-sequence voltages is minimum and zero-sequence voltages is maximum.
- DThe negative-sequence voltages is maximum and zero-sequence voltages is minimum.
18.In case of single line to ground fault
- AAll sequence networks are connected in parallel.
- BAll sequence networks are connected in series.
- CPositive and negative sequence networks are connected in parallel.
- DZero and negative sequence networks are connected in series.
19.When a line-to-ground fault occurs, the current in the faulted phase is 100 A. the zero-sequence current in this case will be :
- AZero
- B33.3 A
- C66.6 A
- D100 A
20.Zero sequence fault current is absent when fault is
- ASingle-line-to ground fault.
- BLine-to-line ground fault.
- CLine-to-line
- DDouble-line-to ground fault.