Switchgear Protections

21. Discrimination between main and back up protection is provided by the use of relays which are

1. fact
2. sensitive
3. slow
4. none of the above

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22. Distance relays are generally

1. split-phase relays
2. reactance relays
3. impedance relays
4. none of the above

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23. elays are used for phase faults on long line.

1. Impedance
2. Reactance
3. Either of the above
4. None of the above

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24. Fault diverters are basically

1. fuses
2. relays
3. fast switches
4. circuit breakers

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25. For cost and safety, the outdoor substations are installed for voltages above

1. 11 kV
2. 33 kV
3. 60kV
4. 110kV

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26. For the protection of power station buildings against direct strokes the requirements are

1. interception
2. interception and conduction
3. interception, conduction and dissipation
4. interception, conduction, dissipation and reflection

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27. For which of the following protection from negative sequence currents is provided?

1. Generators
2. Motors
3. Transmission line
4. Transformers

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28. For which of the following ratings of the transformer differential protection is recommended?

1. above 30 kVA.
2. equal to and above 5 MVA
3. equal to and above 25 MVA
4. none of the above

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29. H.R.C. fuse, as compared to a rewirable fuse, has

1. no ageing effect
2. high speed of operation
3. high rupturing capacity
4. all of the above

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30. H.R.C. fuses provide best protection against

1. overload
2. reverse current
3. open-circuits
4. short-circuits

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