36918976 Protection

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OBJECTIVE ELECTRICAL ENGINEERING PROTECTION

1. When all the three phase are shortcircuited it gives rise to:

(a) Asymmetrical fault current(b) Symmetrical fault current(c) Zero current(d) None of the above

Ans b

2. The most common type of fault on theover head lines:

(a) Single line to ground fault(b) Double into ground fault(c) Three phase fault(d) Line to line fault

Ans a

3. Reactors are used in various point in thepower system to

(a) Limit short circuit current(b) Short circuit(c) Avoid short circuit(d) None of the above

Ans a

4. The use of reactor permits installation of

circuit breaker of the(a) Lower rating(b) Higher rating(c) Same rating(d) None of the above

Ans a

5. If a 5 amp. Fuse is blown frequentlyhouse lightning circuit, it is required to

(a) Insert a fuse of higher current rating(b) Insert a fuse of higher voltage rating

(c) Check the load(d) None of above

Ans c

6. H.R.C fuse provide best protectionagainst

(a) Open circuit(b) Short circuit(c) Over load(d) Revers current

Ans b

7. The size of each wire is determined by(a) The amp. Capacity of service wire(b) Atmospheric condition(c) Voltage of the size service wire(d) None of the above

Ans a

8. When a fault occure on the system acircuit breaker

(a) Open the automatically(b) Close automatically(c) Open the manually(d) None of the above

Ans a

9. If the lenth of the arc of circuit breaker increase, its will

(a) Be extinguished(b) Decreases(c) Remain same(d) None of the above

Ans a

10. Current chopping mainly occure in(a) Oil circuit breaker (b) Air blast circuit breaker (c) Vaccume circuit breaker (d) SF6 gas circuit breaker

Ans b

11. Capacitive current breaking result in(a) Short circuit(b) Open circuit(c) Voltage surge(d) None of the above

Ans c

12. The speed of circuit breaker intruption inforced(air)blast circuit breaker

(a) Slow(b) Medium(c) Fast(d) None of the above

Ans c

13. The normal practice to specify themaking current of

(a) Circuit breaker in turn of (b) RMS value(c) Peak value

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(d) Everage value

Ans b

14. Resistance switching is normally resortedin case of

(a) Air blast circuit breaker (b) Bulk oil circuit breaker (c) Minimum oil circuit breaker (d) All type circuit breaker

Ans a

15. For remote operation circuit breaker mustbe required with a

(a) Time delay trip(b) Shunt trip(c) Inverse time trip(d) None of the above

Ans b

16. Which of the following circuit breaker isgenerally used in railway application

(a) Air break circuit breaker (b) Minimum oil circuit breaker (c) Bulk oil circuit breaker (d) SF

6circuit breaker

Ans a

17. Which of the following circuit breaker isused for E.H.T application

(a) Air blast circuit breaker

(b) Minimum oil circuit breaker (c) Bulk oil circuit breaker (d) SF6 circuit breaker

Ans d

18. In circuit breaker the arcing contents aremade of

(a) Porsline(b) Copper tungstone alloy(c) Aluminmum alloy(d) Electronic opper

Ans b

19. Which statement is correct(a) SF

6gas is toxic

(b) SF6 gas is lighter than air (c) SF

6gas is yellow in colour

(d) SF6 gas has cumgent smell

Ans a

20. A relay performs the function of (a) Fault isolation

(b) Fault detection(c) Fault prevention(d) All of the above

Ans b

21. The relay operating coil is suppliedthrough

(a) Fuse(b) Instrument T/F(c) Power T/F(d) None of the above

Ans c

22. Most of the relay on service on electricpower system are

(a) Electronic relay(b) Electro mechanical relay(c) Thermal relay(d) None of the above

Ans b

23. Back-up protection is generally imployedfor protection against

(a) Short circuit fault only(b) Open circuit fault only(c) Both a and b(d) None of the above

Ans a

24. MHO relay is a(a) Voltage restrand directional relay(b) Voltage controlled over current relay(c) Directional restand over current relay(d) Directional restand over voltage relay

Ans a

25. Different relay are mused to protect theequipment against

(a) Internal faulty

(b) Reverse current(c) Over current(d) None of the these

Ans a

26. The least expensive protection for over current in L.V system is

(a) Isolated(b) Oil circuit breaker (c) Reverse able fuse(d) Air breaker circuit breaker

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Ans c

27. Impedance relay can be used for (a) Earth fault(b) Phase fault(c) Both (a) and (b)(d) None of these

Ans c

28. If the fault occurs near the impedancerelay the V/I ratio will be

(a) Higher than the value if the fault occur away from the realy

(b) Lower than the value if the fault occur away from the relay

(c) Constant for all distance(d) None of these

Ans b

29. Which of the following material can notbe used for contents of switching devices

(a) Copper (b) Aluminium(c) Copper alloy(d) Siver

Ans c

30. What is the most serious problem invaccume circuit breaker

(a) Poor arc quenching(b) Low thermal stability(c) Current chopping(d) All of these

Ans c

31. The positive sequence reactance will beequal to negative sequence reactance incase of

(a) T/F(b) Generator

(c) Transmission line(d) Motor

Ans a

32. Rated making capacity of circuit breaker is equal to

(a) /2 X rated symmetrical breakingcapacity

(b) 2.55 X rated symmetrical breakingcapacity

(c) 1 X rated symmetrical breakingcapacity

(d) None of these

Ans b

33. M.H.O realy is used to protect(a) Long transmission line(b) Medium lenth transmission line(c) Short lenth transmission line(d) All of these

Ans a

34. Reactance relay is used to protectionagainst

(a) Earth fault(b) Phase fault(c) Over voltage fault(d) None of these

Ans a

35. The stability of arc in vaccume circuitbreaker is depends on

(a) The control material(b) Its vaccume pressure(c) The circuit paraments(d) All of these

Ans d

36. Why does minimum oil circuit breaker has less volume of oil

(a) There is insulation between contents(b) The oil between breaker contacts has

greater streath(c) Solid insulation is provided for

insulating the contents from earth(d) None of these

Ans c

37. Arcing on transmission line is prevented(a) By circuit breaker (b) By protective relay

(c) By inductor in the neutral(d) By capacitor in the neutral

Ans c

38. The energy in a lightning strock can beas high as

(a) 10 units(b) 100 units(c) 250 units(d) 1000 units

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Ans c

39. In what shape of conductor corona loss isless

(a) Circular (b) Oval(c) Flat(d) Any of these

Ans a

40. Merze price protection is used to protect(a) Transmission line(b) T/F and generator (c) Motor (d) T/F

Ans c

41. Switching and protection are used under taken by

(a) Switch gear (b) Fuse(c) Lightning arrestor (d) Relay

Ans a

42. Distance relay operation is depends on(a) Ratio of current to current(b) Ratio of voltage to current(c) Ratio of voltage to voltage(d) None of these

Ans b

43. Which relay is used to detect and protectinternal fault of T/F

(a) Buchholze relay(b) Directional relay(c) Thermal relay(d) Distance relay

Ans a

44. Surge protector provide(a) High impedance to normal voltage

(b) Low impedance to surge(c) Both a and b(d) None of these

Ans c

45. An isolator operate under (a) No load condition(b) Full load condition(c) 50% of full load condition(d) At fault current

Ans a

46. The lightning arrestor (L.A) is connected(a) In series in the line(b) Between line and earth(c) To a pole near the line(d) None of these

Ans b

47. Relay is using induction disc principleoperate

(a) Only on D.C(b) Only on A.C(c) Either on D.C or A.C(d) None of these

Ans b

48. Earthing is necessary to give protectionagainst

(a) Voltage fluctuation(b) Over loading(c) Danger of electric shock(d) High temperature of conductor

Ans c

49. The primary function of a fuse is to(a) Protect the appliances(b) Open the circuit(c) Prevent excessive current(d) Protect the line

Ans c

50. The accepted value of dielectric strengthof T/F oil is

(a) 30 KV(b) 40 KV(c) 30 KV/minute (30 KV/2.5 mm/minute(d) None of these

Ans c

51. As compare to air the relative dielectric

strength of SF

6

gas is nearly (more)(a) 1.5 times(b) 4 times(c) 2.5 times(d) 5 times

Ans b

52. Which of the following gas has been usedas insulating medium in electricalappliances

(a) Nitrogen(b) Carbon dioxide

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(c) Sulphur haxa floride (SF6)

(d) Freon

Ans c

53. Liquids are generally used as insulatingmaterial upto stress of about

(a) 100 M volt/cm(b) 50 mv/cm(c) 50 kv/cm(d) 500 kv/cm

Ans c

54. Low voltage circuit breaker has ratedvoltage less than

(a) 66 KV(b) 33 KV(c) 11 KV(d) 1000 volt

Ans d

55. When a H.V circuit breaker is tested for inductance it is tested for at least

(a) 5000 open-closing operation(b) 3600 open-closing operation(c) 1000 open-closing operation(d) None

Ans c

56. For H.V ac circuit breaker the rated shortcircuit current is passed for

(a) 12 second(b) 3 second(c) 9 second(d) None

Ans c

57. Air blast circuit breaker, the pressure of air is of the order of

(a) 40-50 kg/cm2

(b) 3-5 kg/cm2 (c) 1-3 kg/cm2

(d) 20-30 kg/cm2

Ans d

58. The pressure of SF6

gas in circuit is of the order of 1-14 kg/cm2

(a) 3-5 kg/cm2

(b) 20-30 kg/cm2 (c) 18-20 kg/cm

2

(d) None

Ans a

59. Air blast circuit breaker can be installedon

(a) 11 kv(b) 66 kv(c) 132 kv(d) 400 kv

Ans d

60. Air blast circuit breaker for 400 kv power system are designed to operate in

(a) 50 milli second(b) 5 milli second(c) 100 milli second(d) None

Ans a

61. Breaking capacity of a circuit breaker isusually expressed in term of

(a) KVA

(b) MVA(c) KVAR(d) MVAR

Ans c

62. The capacitor switching is easily donewith

(a) Air blast circuit breaker (b) Oil circuit breaker (c) Vaccume circuit breaker (d) Any of above

Ans c

63. The most suitable circuit breaker for shortline fault without switching resistor is

(a) Air blast circuit breaker (b) SF

6gas circuit breaker

(c) Minimum oil circuit(d) None

Ans b

64. For rural electrification in a country like

india with complex network. It is preffer touse

(a) Oil circuit network(b) Minimum oil circuit breaker (c) Vaccume circuit breaker (d) Air breaker C.B

Ans c

65. Where voltage are high and current to beintrupted is low. The breaker preffered is

(a) Vaccume circuit breaker (b) Oil circuit breaker

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(c) Air blast circuit breaker (d) Any one of the above

Ans a

66. To limit current chopping in V.C.B thecontect material used has

(a) Low vapour pressure and highconductivity properties

(b) Low vapour pressure and lowconductivity properties

(c) High vapour pressure and lowconductivity properties

(d) None of these

Ans c

67. A 3Q circuit breaker is rated at 2000 MVA33 KV,it making current will be

(a) 69 KA(b) 89 KA

(c) 49 kilo ampere(d) None of these

Ans c

68. While using air blast circuit breaker,current chopping is a phenomenon oftenobserved, when

(a) Long over head line switched off (b) A T/F on no load switched off (c) A bank of capacitors is switched off (d) A heavy load switched off

Ans b

69. In order to quench the arc quickly andalso optimize the dimentions, generally

(a) SF6 gas circuit breaker is prefferd(b) Air blast circuit breaker is prefferd(c) Oil circuit breaker is prefferd(d) Minimum oil circuit breaker is prefferd

Ans b

70. A circuit breaker is a

(a) P.F correcting device(b) Wave shape correcting device(c) Current intrupting device(d) A device to neutralize the effect of

transient

Ans c

71. Circuit breaker usually operated under (a) Steady state short circuit current(b) Sub-transient state of short circuit

current(c) Transient state of short circuit current

(d) None of the above

Ans c

72. A circuit breaker normally operater (a) When the line is to tested(b) When the switch is put on(c) When the power is to be supplied(d) When ever fault occur is the line

Ans d

73. While selecting a gas for circuit breaker,the property of gas, that should beconsidered is

(a) Non- toxicity(b) Non-inflame ability(c) High dielectric strength(d) All of these

Ans d

74. The fault clearly time of a circuit breaker is usually of

(a) Few cycle of supply voltage(b) Five second(c) Five minotue(d) One minotue

Ans a

75. For high voltage A.C circuit breaker therated short circuit current is passed for

(a) 0.01 second

(b) 3 second(c) 0.1 second(d) 30 second

Ans c

76. Out of the following circuit breaker whichone has the lowest voltage range

(a) Air break circuit breaker (b) Air blast circuit breaker (c) Tank type oil circuit breaker (balk oil)(d) Minimum oil circuit breaker

Ans a

77. In minimum oil current breaker, used oilfor

(a) Insulation only(b) Arc quenching only(c) Cooling only(d) Lubrication only

Ans c

78. The medium used for arc aretinction in

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the air circuit breaker is(a) Oil(b) SF

6gas

(c) Air (d) Compressed air

Ans b

79. Air used in air blast circuit breaker must(a) Have least cor (b) Be-oinized(c) Have oil mixed(d) Be free from moisture

Ans d

80. Under normal condition a circuit breaker should be inspected

(a) Every day(b) Once in six month or 12 month(c) Every week

(d) Once in six years to 7 years

Ans c

81. In a vaccume circuit breaker, thevaccume in the order of

(a) 1 torr (b) 10-12 torr (c) 10

-6torr

(d) 10-16 torr

Ans b

82. Plane break oil circuit breaker can beused upto

(a) 11 kv(b) 33 kv(c) 1.1 kv(d) 132 kv

Ans a

83. For E.H.V line, which of the followingcircuit breaker is preffered

(a) Air breaker circuit breaker

(b) Bulk oil circuit breaker minimum oilcircuit breaker

(c) Minimum oil circuit breaker (d) Any of the above

Ans c

84. Air blast circuit breaker for 400 KV power system are designed to operate in

(a) 5 milli second(b) 500 milli second(c) 50 milli second


Ans b

85. For high speed circuit breaker the totalclearing time is nearly

(a) 1-2 cycle(b) 50 cycle(c) 7-12 cycle(d) 60 cycle

Ans a

86. If the least of the all of circuit breaker isincreased its resistance will

(a) Increase(b) Remain same(c) Decreases(d) None of these

Ans a

87. If the dielectric strength of the mediumbetween contects build up more rapidlythan the re-striking voltage, then the arcwill

(a) Be extinguished(b) Not be extinguished(c) Increase(d) None of the above

Ans a

88. Which of the following circuit breaker take

minimum time for installation(a) Air blast circuit breaker (b) Minimum oil circuit breaker (c) Bulk oil circuit breaker (d) SF6 gas circuit breaker

Ans c

89. Bulk oil circuit breaker is suitable for voltage upto

(a) 6.6 kv(b) 11 kV

(c) 36 KV(d) 132 KV

Ans c

90. Which of the following circuit breaker ismost popular for out ultra H.V application

(a) Air blast circuit breaker (b) Minimum oil circuit breaker (c) Bulk oil circuit breaker (d) Vaccume circuit breaker

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Ans a

91. The voltage across the circuit breaker pole, after final current zero is

(a) Recovery voltage(b) Re-striking voltage(c) Supply voltage(d) None of these

Ans a

92. Which of the following circuit breaker does not use pneumatic operatingmechanism

(a) Air blast circuit breaker (b) SF


(c) Air blast circuit breaker (d) Bulk oil circuit breaker

Ans d

93. Rutien tests are conductor on(a) Minimum oil circuit breaker (b) Air blast circuit breaker (c) Oil circuit breaker (d) All of the above

Ans d

94. In modern E.H.V circuit breaker theoperating time between instant of receiving tripp single and final contectseparation is of the order of

(a) .001 second(b) .015 second(c) .003 second(d) .03 second

Ans d

95. The circuit breaker which have highrelabilty and negaligible maintenance

(a) Air blast circuit breaker (b) Minimum oil circuit breaker (c) SF


(d) Bulk oil circuit breaker

Ans c

96. For modern circuit breaker, the time of closing the cycle is

(a) .001 second(b) .1 second(c) .01 second(d) .003 second

Ans c

97. The arc voltage produced in A.C circuit

breaker is always(a) Leading the arc current by 900 (b) Lagging the arc current by 90

0

(c) In phase with the arc current(d) None of the above

Ans c

98. The transient stability of power systemcan be effectively improved by

(a) Excitation control(b) Phase shifting transformer (c) Single pole switching circuit breaker (d) Increasing the turbine value opening

Ans c

99. Which of the circuit breaker is costly(a) Air blast circuit breaker (b) SF6 gas circuit breaker (c) Minimum oil circuit breaker

(d) None of these

Ans a

100. The speed of circuit instruption inforsed air blast circuit breaker is

(a) Slow(b) Fast(c) Medium(d) None of above

Ans c

101. The fault current intrupted bymodern circuit breaker attain value ashigh as

(a) 10000 amp(b) 100000 amp(c) 60000 amp(d) None of above

Ans b

102. In modern breaker at the time faultcurrent the temperature inside rise up to

(a) 300000

C(b) 90000 0C(c) 60000 0C(d) None

Ans a

103. The circuit breaker of least design,are capable of intrupting current thesecondition with an arc duration of

(a) 5-20 mile second(b) 5-20 second(c) 5-20 minute

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Ans a

104. A fuse blowns of by(a) Melting(b) Arcing(c) Burning(d) None of the above

Ans a

105. A fuse operate on with effect of electric current

(a) Magnetic effect(b) Heating effect(c) Electrostatic effect(d) Photo electric effect

Ans c

106. A delay fuse is generally used for the protection of

(a) 3 Q motor (b) Flourocent motor (c) G.l.S lamps(d) All the above

Ans a

107. As compared to rewire able fuse aH.R.C fuse has

(a) High rupturing capacity(b) High speed of operation

(c) No aging effect(d) All the above

Ans d

108. A fuse wire made of whichmaterial will have relatively sharp meltingaction

(a) Copper (b) Tin-lead-aloy(c) Silver (d) Aluminium

Ans b

109. A fuse should have(a) Low resistance and high melting point(b) Low resistance and low melting point(c) High resistance and high melting point(d) High specific resistance and low

melting point

Ans d

110. In H.R.C fuse major portion of heat

generated is dissipated by(a) Conduction(b) Radiation(c) Convention(d) None of above

Ans a

111. Which fuse material is moresuspected to oxcidation as compare tothe remaining

(a) Tin lead alloy(b) Copper (c) Silver (d) None

Ans b

112. Protection by fuse is generally notuse beyond

(a) 10 A

(b) 25 A(c) 100 A(d) 250 A

Ans c

113. Which of the following is used inliquid fuse

(a) Carbon tetra chloride(b) Sulphur hexa floride(c) Distilled water (d) Transformer oil

Ans a

114. A fuse is never instated in(a) Phase lime(b) Positive of d.c circuit(c) Negative of d.c circuit(d) Neutral wire

Ans d

115. H.R.C fuse posses(a) Linear time current characteristic

(b) Inverse time current characteristic(c) Parabolic time current characteristic(d) None of the above

Ans b

116. H.R.C fuse can be used up to(a) 100 A(b) 33 KA(c) 1000 A(d) 330 KA

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Ans c

117. Under fault condition informationto the circuit breaker is provided by

(a) Rewire able fuse(b) Relay(c) H.R.C fuse(d) All the above

Ans c

118. Out door type switch gear isgenerally used for voltage beyond

(a) 11 KV(b) 66 KV(c) 33 KV(d) 132 KV

Ans b

119. A high speed circuit breaker can

compleat its operation time(a) 1 micro second(b) 1 mili second(c) 2-3 cycle of frequency(d) 4-8 cycle of frequency

Ans c

120. The power factor of arc in a circuitbreaker is

(a) 0 lagging(b) 0 leading(c) 0.8 lagging(d) Unity

Ans d

121. The time instant from the instantopening contact to the instant of extinction of arc is known as

(a) Arc clearance time(b) Break time(c) Arc duration time(d) None of the above

Ans a

122. The time interval from the instantof fault to the instant of energizing the tripcoil is known as

(a) Arcing time(b) Breaking time(c) Operating(d) Protection time

Ans d

123. The time interval from the instant

of energizing the trip coil to the instant of opening of the contacts is known as

(a) Arcing time(b) Operating time(c) Breaking time(d) Total clearing time

Ans b

124. The time interval from the instantof fault to the instant of extinction of arc isknown as

(a) Clearing time(b) Making time(c) Break time(d) None of the above

Ans a

125. The breaking capacity of 3 Qcircuit breaker is given by

(a) Service voltage X rated symmetricalcurrent

(b) 3 X service voltage X ratedsymmetrical current

(c) /3 X service voltage X ratedsymmetrical current

(d) None of these

Ans c

126. Which of the following is not a partof C.breaker

(a) Explosion pot(b) Current T/F(c) Fixed and moving contacts(d) Operating machenism

Ans b

127. Which of the following circuitbreaker the arc energy produced will beleast

(a) Air blast circuit breaker (b) Minimum oil circuit breaker (c) Plane oil circuit breaker (d) Self generated pressure oil circuit

breaker

Ans a

128. Air blast circuit breaker are usedabove

(a) 11 KV(b) 33 KV(c) 66 KV(d) 132 KV

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Ans d

128 A.In case of SF6 circuit breaker the time of intruption is

(a) 1 micro second(b) 3 mili second(c) 3 second(d) 3 cycle

Ans d

129. Which of the following is not truefor SF6 gas

(a) SF6 gas has insulation property(b) SF6 gas is not inflame able(c) SF

6gas is poisonous

(d) SF6 gas is heavier than air

Ans c

130. The dielectric strength of SF6

gas

at atmospheric pressure is nearly(a) Same as that of air (b) Less than that of air (c) 21/2 time that of air (d) 10 -15 time that of air

Ans c

131. The circuit breaker for E.H.Tapplication is

(a) Air blast circuit breaker (b) SF6 gas circuit breaker (c) Minimum oil circuit breaker (d) None of these

Ans b

132. Relay can be design to change in(a) Voltage(b) Lightning intensity(c) Current(d) Any of the above

Ans d

133. The operating time for high speedrelay is usually(a) 1 second(b) 1 mili second(c) 1-2 cycle(d) 10-15 cycle

Ans c

134. The operating of a distance relayis based on the measurement of any of the following, expect

(a) Admittance

(b) Impedance(c) Reactance(d) Frequency

Ans d

135. The operating time of a relay withinverse time characteristic could be

(a) 2-3 cycle(b) 5-10 mili second(c) 2-3 micro second(d) 5-10 second

Ans a

136. A single phasing relay is used on(a) Single phase motor (b) Universal motor (c) Three phase motor (d) Three phase motor

Ans c

137. In distance relay the operatingdepends upon

(a) Voltage(b) Voltage to current ratio(c) Current(d) None of the above

Ans c

138. Which relay is used for protectionprotecting a T/F against frame leakage

(a) Directional relay(b) Intentanious earth fault relay(c) Intentanious over voltage relay(d) Intentanious over current relay

Ans b

139. Translay relay is suitable for (a) Feeder (b) The welding T/F(c) Alternator (d) None of the above

Ans a

140. Merg price protection relay isused for

(a) Air cooled T/F(b) Alternator (c) Short transmission line(d) Long transmission line

Ans b

141. MHO relay is used for

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(a) Long transmission line(b) Feeder (c) Alternator (d) Transformer

Ans a

142. The pilot relay is provided toobtained

(a) Pre-set tripping(b) Delayed tripping(c) High speed tripping(d) None of the above

Ans c

143. For the protection of radial feeder the relay used must have

(a) Linear time characteristic(b) Inverse time characteristic(c) Extetion time characteristic


Ans b

144. Reactance relay are used for phase fault in

(a) Long transmission line(b) Medium transmission line(c) Short transmission line(d) All of the above

Ans c

145. In induction type relay, torque isdirectly proportional to

(a) Current(b) /current(c) 1/current(d) Current

2

Ans d

146. The relay preffered for phase faultalong long transmission line is

(a) Reactance relay

(b) Impedance relay(c) MHO relay(d) Buchholze relay

Ans c

147. Relay preffered for phase faultalong medium transmission line is

(a) MHO relay(b) Buchholze relay(c) Impedance(d) Reactance relay

Ans c

148. Relay generally used for phasefault is

(a) Distance relay(b) Induction relay(c) Over current relay(d) MHO relay

Ans a

149. Which of the following is not adistance relay

(a) Reactance relay(b) Induction relay(c) Buchholze relay(d) MHO relay

Ans b

150. Earth fault relay are, invariable

(a) Short operating time relay(b) Long operating time relay(c) Directional relay(d) Non-directional relay

Ans c

151. A thermal protection circuitprovided protection against

(a) Over voltage(b) Short circuit(c) Over load(d) Temperature rise

Ans c

152. A use of air core reactors is agenerally restricted up to

(a) 1.1 KV(b) 3.3 KV(c) 11 KV(d) 132 KV

Ans c

153. The used oil immersed reactanceis generally restricted up to(a) 1.1 KV(b) 33 KV(c) 11 KV(d) There is no restricted of voltage

normally

Ans d

154. The reactance for the protection of transmission line are connected in

(a) Series

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(b) Delta(c) Parallel(d) Star

Ans a

155. Any voltage surge travlling on thetransmission line, will first enter in

(a) Switch gear (b) Current transformer (c) Circuit breaker (d) Lightning arrestor

Ans d

156. A lightning arrestor is alwayslocated

(a) Before the isolator (b) Before the switch gear (c) Before the transformer (d) Before the current transformer

Ans c

157. The main purpose of providinglightning arrestor in a sub-station is toprotect

(a) Circuit breaker (b) Relay(c) Transformer (d) Civil-structure

Ans c

158. Explution type lightning arrestor are used with system having operatingvoltage up to

(a) 11 KV(b) 33 KV(c) 1.1 KV(d) None of the above

Ans c

159. Which of the following needs toprotect a direct stock due to lightning

(a) Power station(b) Sub-station(c) Over head transmission line(d) All of the above

Ans d

160. Which of the following systemsuffer most from arcing ground

(a) Solid ground neutral system(b) Insulated neutral system(c) Resistance ground neutral system

(d) Reactance ground neutral system

Ans b

161. Which section of power systemgenerally suffer from more fault ascompared to the remaining

(a) Generator (b) Transmission line(c) Transformer (d) Under ground cable

Ans c

162. Least no. of fault reported for (a) Cable(b) Switch gear (c) Transformer (d) Transmission line

Ans a

163. Batteries are provided at sub-station mainly for

(a) Emergency lightning(b) Voltage regulation(c) Trip circuit(d) Meter movement

Ans c

164. The gap lenth of rod type surgedivertor used for 132 KV line should be

(a) 10 cm

(b) 50 cm(c) 15 cm(d) 65 cm

Ans d

165. Wave trap is use to trap wave of (a) Low frequency(b) Higher frequency(c) Power frequency(d) Micro wave frequency

Ans c166. When a transmission line is

energized the wave that propagates it is(a) Current wave only(b) Voltage wave only(c) Current and voltage wave only(d) None of above

Ans c

167. A circuit breaker is rated at 2000amp 1500 MVA,33 KV 3 Q, OCB, then

7/27/2019 36918976 Protection



the making current is(a) 1.2 KA(b) 67 KA(c) 26.25 KA(d) None of above

Ans c

Breaking capacity = 1500 MVAvoltage = 33 KVbreaking current = 1500 MVA/3X33 KV 10 3 =

26.25 KA

Making current = 2.55 X breaking current

= 2.55 X 26.25 =67 KA

36918976 Protection

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