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Saturday, 26 November 2016

Protection of Power System - Multiple Choice Question

Protection of Power System - Multiple Choice Question Points : protection of power system multiple choice questions and answers, electrical objective type question answers, mcqs, protection of power system blanks 1. Overheating of a transformer may be due to
(i) overloads
(ii) short-circuits
(iii) failure of cooling system
(iv) all above

2. In an alternator, relay protection is absolutely necessary against
(i) over current
(ii) field failure
(iii) stator winding faults
(iv) none of above

3. When failure of prime-mover takes place3 the alternator
(i) runs as a synchronous motor
(ii) draws some current from the supply
(iii) is in the inverted running mode
(iv) all above

4. If the stator winding fault is not cleared quickly, it may lead to
(i) burning of stator coils
(ii) burning and welding-up of stator laminations
(iii) damage to other equipment
(iv) all above

5. The most important stator winding fault in an alternator is
(i) fault between phase and ground
(ii) fault between phases
(iii) inter-turn fault in one phase
(iv) none of above

6. Balanced earth-fault protection is generally provided for
(i) small-size alternators
(ii) medium-size alternators
(iii) large-size alternators
(iv) none of above

7. In case of slow developing faults in a transformer, the Buchholz relay
(i) sounds an alarm
(ii) trips the circuit breaker
(iii) both (i) and (ii)
(iv) none of above

8. The busbar protection means protection of
(i) busbar
(ii) isolating switches
(iii) circuit breakers
(iv) all above

9. The earth fault current is generally than the short-circuit current.
(i) less
(ii) more
(iii) equal to
(iv) none of above

10. A surge diverter should be located ……… the apparatus to be protected.
(i) close to
(ii) far away from
(iii) in the middle of
(iv) none of above

11. The least expensive protection for low-voltage system is
(i) isolator
(ii) oil circuit breaker
(iii) fuse
(iv) air break CB

12. The most serious voltages on the power system are those caused by
(i) insulation failure
(ii) lightning
(iii) resonance
(iv) arcing ground

13. The ideal scheme of protection for overhead lines is
(i) time-graded over current protection
(ii) distance protection
(iii) differential protection
(iv) none of above

14. The ground wires protect the transmission line against
(i) direct lightning stroke
(ii) indirect lightning stroke
(iii) both (i) and (ii)
(iv) none of above

15. The most dangerous fault in an alternator is
(i) failure of field
(ii) stator winding faults
(iii) failure of prime-mover
(iv) unbalanced loading

16. The Merz-Price circulating current scheme is uneconomical for the protection of
(i) overhead fines
(ii) alternators
(iii) transformers
(iv) none of above

17. Buchholz relay is
(i) a gas-actuated relay
(ii) oil actuated relay
(iii) can be either (i) or (ii)
(iv) none of above

18. Earting screen provides protection to power stations and substation against
(i) direct lighting stroke
(ii) indirect lightening stroke
(iii) both (i) and (ii)
(iv) none of above

19. Buchholz relay in oil immersed transformer provides protection against
(i) insulation failure of windings
(ii) core heating
(iii) fall of oil level
(iv) all above

20. The earthing screen provides protection against
(i) indirect lightning strokes
(ii) short-circuits
(iii) direct lightning strokes
(iv) none of above

21. The overhead lines can be protected by
(i) instantaneous overcurrent relays
(ii) inverse time overcurrent relays
(iii) directional overcurrent relays
(iv) all above

22 . For protection against direct lightning stroke, we use
(i) ground wire
(ii) lightning arrester
(iii) both (i) and (ii)
(iv) none of above

23. The changes of faults occurring on transformers are very rare because they are
(i) static devices
(ii) totally enclosed
(iii) generally oil immersed
(iv) all above

24. In transmission line
(i) Inductance > Capacitance
(ii) Inductance < Capacitance
(iii) Inductance = Capacitance
(iv) none of above

25. For the protection of arcing ground, we use
(i) Peterson coil
(ii) ground wire
(iii) lightining arrester
(iv) none of above

26. The amount of damage to the equipment due to voltage surge depends on the
(i) amplitude of surge
(ii) steepness of its wave front
(iii) both (i) and (ii)
(iv) none of above

27. For protection against low voltage high frequency oscillation we use
(i) capacitors
(ii) surge absorbers
(iii) either (i) or (ii))
(iv) none of above

28. The surge diverters the station equipment against
(i) direct lightning stroke
(ii) travelling strokes
(iii) both (i) and (ii)
(iv) none of above

29. A can act as a surge absorber.
(i) a capacitor connected between line and earth
(ii) a parallel combination of choke and resistance connected in series with the line
(iii) either (i) or (ii)
(iv) none of above

30. For the proper protection of power system, the operating time of a relay should be
(i) 10 seconds
(ii) less than, 1 second
(iii) more than 10 seconds
(iv) none of above

31. Differential system of transformer protection provides protection against
(i) earth faults only
(ii) phase faults only
(iii) both (i) and.(ii)
(iv) none of above

32. Internal cause of overvoltage in a power system may be due to
(i) opening a loaded line
(ii) closing an unloaded line
(iii) insulation failure
(iv) all above

33. As compared to station equipment (e.g. alternators, transformers etc), the chances of faults on overhead lines are
(i) less
(ii) more
(iii) about same
(iv) none of above

34. As compared to negatively charged clouds, the number of lightning strokes due to the positively charged clouds is
(i) more
(ii) less
(iii) about the same
(iv) none of above

35. The equipment used for the protection of power system against lightning surges is
(i) earthing screen
(ii) overhead ground wires
(iii) lightning arresters
(iv) all above

36. The schemes of protection for transformer depend upon
(i) size of transformer
(ii) nature of load supplied
(iii) importance of service required
(iv) all above

37. The ground wires are placed ……. the line conductors
(i) below
(ii) above
(iii) in middle
(iv) none of above

38. Differential protection in principle is employed for
(i) protection of alternators
(ii) protection of transformers
(iii) bus-zone protection
(iv) all above

39. For the protection of power system against travelling waves, we use
(i) earthing screens
(ii) surge diverters
(iii) overhead ground wires
(iv) none of above

40. The automatic relay protection is generally not provided for the foll6wing alternator faults
(i) failure of field
(ii) over current
(iii) over speed
(iv) all above

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