400 Important Switchgear and Protection MCQ Question and Answer | PDF Free Download
1.IDMT relays are used to protect the power transformers against
- AExternal short circuits
- BOverloads
- CInternal short circuits
- DBoth (a) and (b)
2.In an inverse definite minimum time, electromagnetic type overcurrent relay, the minimum time feature is achieved because of
- ASaturation of the magnetic circuit
- BProper mechanical design
- CAppropriate time-delay element
- DElectromagnetic damping
3.Earth fault relays are
- ADirectional relays
- BNon-Directional relays
- CShort operate time relays
- DNone of these
4.The domains of power system where directional overcurrent relay is indispensable are
- AIn case of parallel protection
- BIn case of ring main feeder protection
- CBoth (a) and (b)
- DNone of the above
5.Directional overcurrent relays have two exciting coils connected across
- ACT secondaries of two different phases.
- BVT secondaries of two different phases.
- CCT and VT secondaries of the same phases.
- DCT and VT secondaries of two different phases.
6.In distance protection, the relay measures
- ANegative sequence impedance of the line from relay up to the fault point.
- BPositive sequence impedance of the line from relay up to the fault point.
- CSelf-impedance of the line from relay up to the fault point.
- DZero sequence impedance of the line from relay up to the fault point.
7.If the fault occurs near the relay, the V/I ratio will be
- ALower than that of if the fault occurs away from the relay.
- BConstant for all distances.
- CHigher than that of it the fault occurs away from the relay.
- DNone of the above.
8.Impedance relay may use
- ABalance beam structure.
- BInduction-cup structure.
- CShaded pole structure.
- DEither (a) or (b)
9.Impedance relay can be used for
- APhase faults only
- BEarth faults only
- CBoth Phase and Earth faults
- DNone of above
10.An impedance relay is a
- AVoltage restrained overcurrent relay.
- BVoltage restrained directional relay.
- CDirectional restrained overcurrent relay.
- DDirectional restrained overvoltage relay.
11.The Threshold characteristics of a plain impedance relay in a complex Z plane is a
- ACircle passing through origin.
- BCircle with the centre at the origin.
- CStraight line passing through origin.
- DStraight line offset from the origin.
12.On transient fault OC and impedance relay.
- AUnder reaches
- BOver reaches
- CReach unaffected
- DNone of these
13.The structure used in reactance relays is
- AInduction cup
- BDouble Induction Loop
- CSingle Induction Loop
- DEither (a) or (b)
14.A reactance relay is
- AVoltage restrained overcurrent relay.
- BVoltage restrained directional relay.
- CDirectional restrained overcurrent relay.
- DDirectional restrained overvoltage relay.
15.The operating characteristics of a reactance relay in the complex impedance plane is a
- ACircle with its origin at the centre of the R-X plane.
- BCircle passing through the origin.
- CStraight line passing through the origin.
- DStraight line parallel to the X-axis.
16.Reactance relay is normally used for protection against
- AEarth fault only
- BPhase fault only
- CBoth Earth and Phase faults
- DNone of the above
17.Admittance relay is
- ANon-directional relay
- BDirectional relay
- CDifferential relay
- DNone of these
18.A mho relay is a
- AVoltage restrained directional relay.
- BVoltage restrained overcurrent relay.
- CDirectional restrained overcurrent relay.
- DDirectional restrained overvoltage relay.
19.For ground fault we prefer :
- APlain impedance relay
- BDirectional relay
- CReactance relay
- DOver current relay
20.An over current relay is said to over reach when it operates at a current
- AHigher than its setting
- BEqual to its setting
- CLower than its setting
- D2/3rd of its setting