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Overview

1. The surge impedance of 50 miles long underground cable is 50 ohms. For a 25 miles
length it will be:
(a) 25 ohms (b) 50 ohms
(c) 100 ohms (d) None of the above.
2. For a load flow solution the quantities normally specified at a voltage controlled bus are:
(a) P and Q (b) P and |V|
(c) Q and |V| (d) P and δ.
3. For reducing tower footing resistance it is better to use:
(a) Chemical and ground rods only
(b) Chemical and counterpoise only
(c) Ground rod and counterpoise only
(d) Chemical, ground rods and counterpoise.
4. The positive, negative and zero sequence impedances of a solidly grounded system under
steady state condition always follow the relations:
(a) Z1 > Z2 > Z0 (b) Z1 < Z2 < Z0
(c) Z0 < Z1 < Z2 (d) None of the above.
5. Mho relay is normally used for the protection of:
(a) Long transmission lines (b) Medium length lines
(c) Short length lines (d) No length criterion.
6. Reactance relay is normally preferred for protection against:
(a) Earth faults only (b) Phase faults only
(c) None of the above.
7. If the fault current is 2000 amps, the relay setting 50% and the C.T. ratio is 400/5, then
the plug setting multiplier will be:
(a) 25 amps (b) 15 amps
(c) 50 amps (d) None of the above.

CL Wadhwa bits Solutions (1-7)

8. Carrier current protection scheme is normally used for:
(a) HV transmission lines only
(b) HV cables only
(c) HV transmission and cables.
9. The ratio of reset to pick up current for an induction cup relay is approx:
(a) 0.99 (b) 1.01
(c) 0.75 (d) None of the above.
10. The rotation of disc of an induction disc relay under the poles is:
(a) From unshaded pole to shaded pole
(b) From shaded pole to unshaded pole
(c) It depends upon the magnitude of current
(d) It depends upon the C.T. secondary connection.
11. If the time of operation of a relay for unity TMS is 10 secs., the time of operation for 0.5
TMS will be:
(a) 20 secs (b) 5 secs
(c) 10 secs (d) None of the above.
12. The shape of the disc of an induction disc relay is:
(a) Circular (b) Spiral
(c) Elliptic.
13. If the phase angle of the voltage coil of a directional relay is 50° the maximum torque
angle of the relay is:
(a) 130° (b) 100°
(c) 25° (d) None of the above.
14. A reactance relay is:
(a) Voltage restrained directional relay
(b) Directional restrained over-current relay
(c) Voltage restrained over-current relay
(d) None of the above.

CL WADHWA bits solutions (8-14)

15. The per cent bias for a generator protection lies between:
(a) 5 to 10 (b) 10 to 15
(c) 15 to 20 (d) None of the above.
16. For protection of parallel feeders fed from one end the relays required are:
(a) Non-directional relays at the source end and directional relays at the load end.
(b) Non-directional relays at both the ends.
(c) Directional relays at the source end and non-directional at the load end.
(d) Directional relays at both the ends.
17. The number of pilot wires required for protecting 3-phase transmission lines using
Translay system of protection is:
(a) 6 (b) 4
(c) 3 (d) 2.
18. A shunt fault is characterized by:
(a) Increase in current, frequency and p.f.
(b) Increase in current reduction in frequency and p.f.
(c) Increase in current and frequency but reduction in p.f.
(d) None of the above.
19. For measuring positive, negative and zero sequence voltages in a system, the reference
is taken as:
(a) Neutral of the system only
(b) Ground only
(c) For zero sequence neutral and for positive and negative the ground
(d) None of the above.
20. The most economic load on an overhead line is:
(a) Greater than the natural load (b) Less than the natural load
(c) Equal to the natural load (d) None of the above is necessary.
21. The most economic load on an underground cable is:
(a) Greater than its surge loading (b) Less than the surge loading
(c) Equal to the surge loading (d) None of the above is necessary.

CL wadhwa bits solutions (15 - 21)

22. For a long transmission line, for a particular receiving end voltage, when sending end
voltage is calculated, it is more than the actual value when calculated by:
(a) Load end capacitance method (b) Nominal T method
(c) Nominal π method (d) None of the above methods.
23. The p.u. impedance value of an alternator corresponding to base values 13.2 kV and 30
MVA is 0.2 p.u. The p.u. value for the base values 13.8 kV and 50 MVA will be:
(a) 0.306 p.u. (b) 0.33 p.u.
(c) 0.318 p.u. (d) 0.328 p.u.
24. For the same rupturing capacity, the actual current to be interrupted by an HRC fuse is:
(a) Much less than any CB (b) Much more than any CB
(c) Equal to the CB (d) None of the above is necessary.
25. The stability of arc in vacuum depends upon:
(a) The contact material only
(b) The contact material and its vapour pressure
(c) The circuit parameters only
(d) The combination of (b) and (c).
26. To limit current chopping in vacuum circuit breakers, the contact material used has:
(a) High vapour pressure and low conductivity properties
(b) High vapour pressure and high conductivity properties
(c) Low vapour pressure and high conductivity properties
(d) Low vapour pressure and low conductivity properties.
27. The capacitor switching is easily done with:
(a) Air blast circuit breaker (b) Oil C.B.
(c) Vacuum C.B. (d) Any one of the above.
28. Where voltages are high and current to be interrupted is low the breaker preferred is:
(a) Air blast C.B. (b) Oil C.B.
(c) Vacuum C.B. (d) Any one of the above.

CL wadhwa bits solutions (22-28)

29. For rural electrification in a country like India with complex network it is preferable to
use:
(a) Air break C.B. (b) Oil C.B.
(c) Vacuum C.B. (d) M.O. C.B.
30. The current chopping tendency is minimised by using the SF6 gas at relatively:
(a) High pressure and low velocity (b) High pressure and high velocity
(c) Low pressure and low velocity (d) Low pressure and high velocity.
31. SF6 gas has excellent heat transfer properties because of its:
(a) Higher molecular weight (b) Low gaseous viscosity
(c) Higher dielectric strength (d) A combination of (a) and (b)
(e) A combination of (b) and (c).
32. A fault is more severe from the view point of RRRV if it is a:
(a) Short line fault (b) Medium length line fault
(c) Long line fault (d) None of the above.
33. The most suitable C.B. for short line fault without switching resistor is:
(a) Air blast C.B. (b) M.O.C.B.
(c) SF6 Breaker (d) None of the above.
34. The voltages at the two ends of a line are 132 kV and its reactance is 40 ohms. The
capacity of the line is:
(a) 435.6 MW (b) 217.5 MW
(c) 251.5 MW (d) 500 MW.
35. An overhead line with series compensation is protected using:
(a) Impedance relay (b) Reactance relay
(c) Mho relay (d) None of the above.

CL wadhwa bits solutions (29-35)

35. An overhead line with series compensation is protected using:
(a) Impedance relay (b) Reactance relay
(c) Mho relay (d) None of the above.

36. The typical value of SCR for modern alternators is:
(a) 1.5 (b) 1.2
(c) 1.0 (d) 0.5
.
37. In case of a large size alternator the voltage control becomes serious if:
(a) SCR is high (b) SCR is low
(c) Voltage control is independent of SCR.

38. A large-size alternator is protected against overloads by providing:
(a) Overcurrent relays (b) Temperature sensitive relays
(c) Thermal relays (d) A combination of (a) and (b)
(e) A combination of (b) and (c).

39. The impulse ratio of a rod gap is:
(a) Unity (b) Between 1.2 and 1.5
(c) Between 1.6 and 1.8 (d) Between 2 and 2.2.

40. Shunt compensation in an EHV is resorted to:
(a) Improve the stability
(b) Reduce the fault level
(c) Improve the voltage profile
(d) As a substitute for synchronous phase modifier.

CL wadhwa bits solutions (35-40)

41. In order to have lower cost of electrical energy generation:
(a) The load factor and diversity factor should be low
(b) The load factor should be low but diversity factor should be high
(c) The load factor should be high but diversity factor low
(d) The load factor and diversity factors should be high.
42. The insulation of the modern EHV lines is designed based on:
(a) The lighting voltage (b) The switching voltage
(c) Corona (d) RI.
43. The size of conductor on modern EHV lines is obtained based on:
(a) Voltage drop (b) Current density
(c) Corona (d) (a) and (b).
44. A Mho relay is a:
(a) Voltage restrained directional relay
(b) Voltage controlled over current relay
(c) Directional restrained over current relay
(d) Directional restrained over voltage relay.
45. For stability and economic reasons we operate the transmission line with power angle
in the range:
(a) 10° to 25° (b) 30° to 45°
(c) 60° to 75° (d) 65° to 80°.
46. High voltage d.c. testing for HV machines is resorted because:
(a) Certain conclusions regarding the continuous ageing of an insulation can be drawn.(b) The stress distribution is a representation of the service condition
(c) Standardization on the magnitude of voltage to be applied is available
(d) The stresses do not damage the coil end insulation

CL wadhwa bits solutions (41 - 46)

47. For a lumped inductive load, with increase in supply ferquency:
(a) P and Q increase (b) P increases, Q decreases
(c) P decreases, Q increases (d) P and Q decrease.
48. Standard impulse testing of a power transformer requires:
(a) Two applications of chopped wave followed by one application of a full wave
(b) One application of chopped wave followed by one application of a full wave
(c) One application of chopped wave followed by two applications of a full wave
(d) None of the above.
49. The supply voltage |V| in diagram below is:
40 V 70 V 100 V
V
(a) 210 V (b) 70 V
(c) 50 V (d) 230 V.
50. The chances of arc interruption in subsequent current zero:
(a) Increases in case of OCB
(b) Decreases in case of OCB
(c) Interruption is always at first current zero (in OCB)
(d) None of the above.
51. The chances of arc interruption in subsequent current zeros:
(a) Increases in case of ABCB but decreases in OCB
(b) Decreases in case of ABCB but increases in OCB
(c) Decreases in both the cases
(d) Increases in both the cases.
52. The velocity of travelling wave through a cable of relative permittivity 9 is:
(a) 9 × 108 metres/sec (b) 3 × 108 metres/sec
(c) 108 metres/sec (d) 2 × 108 metres/sec.

CL wadhwa bits solutions(47-52)

53. An overhead line with surge impedance 400 ohms is terminated through a resistance R.
A surge travelling over the line does not suffer any reflection at the junction if the value
of R is:
(a) 20 ohms (b) 200 ohms
(c) 800 ohms (d) None of the above.
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54. The rate of rise of restriking voltage depends upon:
(a) The type of circuit breaker
(b) The inductance of the system only
(c) The capacitance of the system only
(d) The inductance and capacitance of the system.
55. Gas turbines can be brought to the bus bar from cold in about:
(a) 2 minutes (b) 30 minutes
(c) 1 Hour (d) 2 Hours.
56. A 3-phase breaker is rated at 2000 MVA, 33 kV, its making current will be:
(a) 35 kA (b) 49 kA
(c) 70 kA (d) 89 kA.
57. If a combination of HRC fuse and circuit breaker is used, the C.B. operates for:
(a) Low overload currents (b) Short circuit current
(c) Under all abnormal current (d) The combination is never used in practice.
58. The impulse ratio of a gap of given geometry and dimension is:
(a) Greater with solid than with air dielectric
(b) Greater with air than with solid dielectric

CL wadhwa bits solutions (53-58)

59. Tick out the correct one:
(a) The insulators and lightning arresters should have high impulse ratio
(b) The insulators and lightning arresters should have low impulse ratio
(c) The insulator should have high impulse ratio and lightning arrester low
(d) The lightning arrester should have high impulse ratio but insulator low.
60. Phase modifier is normally installed in the case of:
(a) Short transmission lines (b) Medium length lines
(c) Long length lines (d) For all length lines.
61. Series compensation on EHV lines is resorted to:
(a) Improve the stability
(b) Reduce the fault level
(c) Improve the voltage profile
(d) As a substitute for synchronous phase modifier.
62. Ferranti effect on long overhead lines is experienced when it is:
(a) Lightly loaded (b) On full load at unity p.f.
(c) On full load at 0.8 p.f. lag (d) In all these cases.
63. Stringing chart is useful for:
(a) Finding the sag in the conductor (b) In the design of tower
(c) In the design of insulator string (d) Finding the distance between the tower.
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64. The presence of earth in case of overhead lines:
(a) Increases the capacitance (b) Increases the inductance
(c) Decreases the capacitance (d) Decreases the inductance.
65. For an existing a.c. transmission line the string efficiency is 80%. Now if d.c. voltage is
supplied for the same set up, the string efficiency will be:
(a) 80% (b) More than 80%
(c) Less than 80% (d) 100%.

CL wadhwa bits solutions (59-65)

66. Effect of increase in temperature in overhead transmission lines is to:
(a) Increase the stress and length
(b) Decrease the stress and length
(c) Decrease the stress but increase the length
(d) None of the above.
67. The Buchholz relay protects a transformer from:
(a) All types of internal fault (b) A turn to turn fault
(c) Winding to winding fault (d) None of them.
68. The Self GMD method is used to evaluate:
(a) Inductance (b) Capacitance
(c) Inductance and capacitance both (d) None of the above
of the overhead transmission lines.
69. A voltage-controlled bus is treated as a load bus in subsequent iteration when its:
(a) Voltage limit is violated (b) Active power limit is violated
(c) Reactive power limit is violated (d) Phase angle limit is violated.
70. The voltage of a particular bus can be controlled by controlling the:
(a) Phase angle (b) Reactive power of the bus
(c) Active power of the bus (d) Phase angle and reactive power.
71. In case of a 3-phase short circuit in a system, the power fed into the system is:
(a) Mostly reactive (b) Mostly active
(c) Active and reactive both equal (d) Reactive only.

CL wadhwa bits solutions (66-71)

72. The load flow solution is always assured in case of:
(a) Newton-Raphson method (b) Gauss method
(c) Gauss-Seidel method (d) None of these methods guarantees.

73. If α is the angle of voltage wave at which an R-L circuit is switched in and θ is the
impedance angle of the R-L circuit, there will be no transient when the circuit is switched
in, if:
(a) α = θ (b) α = 90 – θ
(c) α = 90 + θ (d) None of the above.
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74. At a particular unbalanced node, the real powers specified are:
Leaving the node 20 MW, 25 MW
Entering the node 60 MW, 30 MW
The balancing power will be:
(a) 30 MW leaving the node
(b) 45 MW leaving the node
(c) 45 MW entering the node
(d) 22.5 MW entering the node and 22.5 MW leaving the node.

75. The loss coefficients for a two-bus system are given as follows:
(a) B11 = 0.02, B22 = 0.05, B12 = 0.01, B21 = 0.015.
(b) B11 = 0.02, B22 = 0.04, B12 = – 0.01, B21 = 0.001.
(c) B11 = 0.03, B22 = 0.005, B12 = – 0.001, B21 = – 0.001.
(d) B11 = 0.03, B22 = 0.05, B12 = 0.001, B21 = – 0.001.

76. For economic operation, the generator with highest positive incremental transmission
loss will operate at:
(a) The lowest positive incremental cost of production
(b) The lowest negative incremental cost of production
(c) The highest positive incremental cost of production
(d) None of the above.

77. The inertia constant H of a machine of 200 MVA is 2 p.u. its value corresponding to 400
MVA will be:
(a) 4.0 (b) 2.0
(c) 1.0 (d) 0.5.

CL wadhwa bits solutions (72 - 77)

78. The inertia constant of two groups of machines, which swing together are M1 and M2.
The inertia constant of the system is:
(a)
M M
M M
1 2
1 + 2
(b) M1 – M2, M1 > M2
(c) M1 + M2 (d)
M M
M M
1 2
1 2
+
.
79. The leakage resistance of a 50 km long cable is 1 MΩ. For a 100 km long cable it will be:
(a) 1 MΩ (b) 2 MΩ
(c) 0.66 MΩ (d) None of the above.
80. The coefficient of reflection for current for an open ended line is:
(a) 1.0 (b) 0.5
(c) – 1.0 (d) Zero.
81. The connected load of a consumer is 2 kW and his maximum demand is 1.5 kW. The load
factor of the consumer is:
(a) 0.75 (b) 0.375
(c) 1.33 (d) None of the above.
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82. The maximum demand of a consumer is 2 kW and his daily energy consumption is 20
units. His load factor is:
(a) 10% (b) 41.6%
(c) 50% (d) None of the above.
83. Resistance switching is normally resorted in case of:
(a) Bulk oil circuit breakers (b) Minimum oil circuit breakers
(c) Air blast circuit breakers (d) All types of breakers.
84. If the inductance and capacitance of a system are 1.0 H and 0.01 μF respectively and
the instantaneous value of current interrupted is 10 amp, the voltage across the breaker
contacts will be:
(a) 50 kV (b) 100 kV
(c) 60 kV (d) 57 kV.
85. The p.u. synchronous impedance of a machine is 2.0 p.u., its SCR is:
(a) 2 (b) 1.414
(c) 0.5 (d) 0.707.

CL wadhwa bits solutions (78-85)

86. Sheaths are used in cables to:
(a) Provide proper insulation (b) Provide mechanical strength
(c) Prevent ingress of moisture (d) None of the above.
87. Tick out the correct statement:
(a) The higher the initial load, the larger the critical clearing angle
(b) The higher the initial load, the lower the critical clearing angle
(c) The initial load has nothing to do with the critical clearing angle
(d) The higher the operating time of the circuit breaker, the larger will be the critical
clearing angle.
88. The capacitance and inductance per unit length of a line operating at 110 kV are 0.01 μF
and 2 mH. The surge impedance loading of the line is:
(a) 40 MVA (b) 30 MVA
(c) 27 MVA (d) None of the above.
89. An RLC series circuit remains predominantly inductive:
(a) At resonance frequency (b) Below resonance frequency
(c) Above resonance frequency (d) At the lower half power frequency.
90. An alternator is delivering a load current; its per cent regulation is found to be zero. The
type of load it delivers is:
(a) Capacitive (b) Inductive
(c) Resistive.
91. A short length of cable between the dead end tower and the power transformer :
(a) Always reduces the steepness of the incident wave
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(b) Reduces the steepness of the wave under certain conditions only
(c) It does not change the steepness.
92. For protection of rotating machines against lightning surges a combination of:
(a) Lightning conductor and capacitor
(b) Lightning conductor and lightning arrester
(c) Lightning arrester and capacitor
(d) Lightning arrester alone is used.

CL wadhwa bits solutions (86-92)

93. An alternator is delivering a balanced load at unity p.f. the phase angle between line
voltage and line current is:
(a) 90° (b) 60°
(c) 30° (d) 0°.
94. For the stable operation of interconnected system, the passive element that can be used
a interconnecting element is:
(a) Reactor (b) Resistor
(c) Capacitor (d) Resistor and capacitor.
95. If two synchronous generators are connected, loss of synchronism will result in:
(a) Stalling of generators
(b) Wild fluctuations in current
(c) Wild fluctuations in current and voltage
(d) None of the above.
96. A generator is connected to a synchronous motor. From stability point of view it is
preferable to have:
(a) Generator neutral reactance grounded and motor neutral resistance grounded
(b) Generator and motor neutrals resistance grounded
(c) Generator and motor neutrals reactance grounded
(d) Generator neutral resistance and motor neutral reactance grounded.
97. A 50 Hz, four-pole turboalternator rated at 20 MVA, 13.2 kV has an inertia constant
H = 4 kW sec/kVA. The K.E. stored in the rotor at synchronous speed is:
(a) 80 kilojoules
(b) 80 megajoules
(c) 40 megajoules
(d) 20 megajoules.
98. The breakdown strength of air at STP is 21 kV/cm. Its breakdown strength at 30°C and
72 cm of Hg will be:
(a) 21.25 kV/cm (b) 20.2 kV/cm
(c) 23 kV (d) 19.5 kV/cm.
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99. Corona loss is less when the shape of the conductor is:
(a) Circular (b) Flat
(c) Oval (d) Independent of shape.
100. Corona loss increases with:
(a) Increase in supply frequency and conductor size
(b) Increase in supply frequency but reduction in conductor size
(c) Decrease in supply frequency and conductor size
(d) Decrease in supply frequency but increase in conductor size.

CL wadhwa bits solutions (93-100)

101. The corona loss on a particular system at 50 Hz is 1 kW/phase per km. The corona loss
on the same system with supply frequency 25 Hz will be:
(a) 1 kW/phase/km (b) 0.5 kW/phase/km
(c) 0.667 kw/phase/km (d) None of the above.

102. A system is said to be effectively grounded if its:
(a) Neutral is grounded directly (b) Ratio of
X
X
0
1
> 3.0
(c) Ratio of
R
X
0
1
> 2.0 (d) Ratio of
X
X
0
1
< 3.0.

103. For effective application of counterpoise is should be buried into the ground to a depth
of:
(a) 1 metre (b) 2 metres
(c) Just enough to avoid theft (d) None of the above.

104. If r is the radius of the conductor and R the radius of the sheath of the cable, the cable
operates stably from the view point of dielectric strength if:
(a)
r
R
> 1.0 (b)
r
R
< 1.0
(c)
r
R
< 0.632 (d)
r
R
< 0.368.

105. Three insulating materials with same maximum working stress and permittivities 2.5,
3.0, 4.0 are used in a single core cable. The location of the materials with respect to the
core of the cable will be:
(a) 2.5, 3.0, 4.0 (b) 3.0, 2.5, 4.0
(c) 4.0, 3.0, 2.5 (d) 4.0, 2.5, 3.0.

CL wadhwa bits solutions (101-105)

106. Three insulating materials with breakdown strengths of 250 kV/cm, 200 kV/cm,
150 kV/cm and permittivities of 2.5, 3.0 and 3.5 are used in a single core cable. If the
factor of safety for the materials is 5, the location of the materials with respect to the
core of the cable will be:
(a) 2.5, 3.0, 3.5 (b) 3.0, 2.5, 3.5
(c) 3.5, 3.0, 2.5 (d) 3.5, 2.5, 3.0.
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107. The coefficient of reflection of voltage for a short circuited line is:
(a) 1.0 (b) – 1.0
(c) 0 (d) 2.0.

108. The insulation resistance of a cable of length 10 km is 1 MΩ, its resistance for 50 km
length will be:
(a) 1 MΩ (b) 5MΩ
(c) 0.2 MΩ (d) None of the above
.
109. The capacitance of a 3-core cable between any two conductors with sheath earthed is 2
μF. The capacitance per phase will be:
(a) 1 μF (b) 4 μF
(c) 0.667 μF (d) 1.414 μF.

110. If δ is the loss angle of the cable, its power factor is:
(a) sin δ
(b) cos δ
(c) Power factor is independent of δ
(d) Power factor depends upon δ but it is not as per (a) and (b).

CL wadhwa bits solutions (106-110)

110. If δ is the loss angle of the cable, its power factor is:
(a) sin δ
(b) cos δ
(c) Power factor is independent of δ
(d) Power factor depends upon δ but it is not as per (a) and (b).

111. The effect of bonding the cable is:
(a) To increase the effective resistance and inductance
(b) To increase the effective resistance but reduce inductance
(c) To decrease the effective resistance and inductance
(d) To decrease the effective resistance but increase the inductance.

112. In order to eliminate sheath losses, a successful method is:
(a) To transpose the cable along with cross bonding
(b) Transpose the cables only
(c) Cross bonding the cables is enough
(d) None of the above is effective.

113. The sending end voltage of a feeder with reactance 0.2 p.u. is 1.2 p.u. If the reactive
power supplied at the receiving end of the feeder is 0.3 p.u., the approximate drop of
volts in the feeder is:
(a) 0.2 p.u. (b) 0.06 p.u.
(c) 0.05 p.u. (d) 0.072 p.u.

114. If a synchronous machine is overexcited, it takes lagging vars from the system when it
is operated as a:
(a) Synchronous motor
(b) Synchronous generator
(c) Synchronous motor as well as generator
(d) None of the above.

CL wadhwa bits solutions (110-114)

115. If a synchronous machine is underexcited it takes lagging vars from the system when it
is operated as a:
(a) Synchronous motor
(b) Synchronous generator
(c) Synchronous motor as well as generator
(d) None of the above.

116. A synchronous machine has higher capacity for:
(a) Leading p.f.
(b) Lagging p.f.
(c) It does not depend upon the p.f. of the machine
(d) It depends upon the p.f. of the load.

117. A machine designed to operate at full load is physically heavier and is costlier if the
operating p.f. is:
(a) Lagging (b) Leading
(c) The size and cost do not depend on p.f.

118. For the same voltage boost, the reactive power capacity is more for a:
(a) Shunt capacitor (b) Series capacitor
(c) It is same for both series and shunt.

119. A synchronous phase modifier as compared to a synchronous motor used for mechanical
loads has:
(a) Larger shaft and higher speed (b) Smaller shaft and higher speed
(c) Larger shaft and smaller speed (d) Smaller shaft and smaller speed.

CL wadhwa bits solutions (115-119)

120. If Ia1 is the positive sequence current of an alternator and Z1, Z2 and Z0 are the sequence
impedances of the alternator. The drop produced by the current Ia1 will be:
(a) Ia1 Z1 (b) Ia1 (Z1 + Z2)
(c) Ia1 (Z1 + Z2 + Z0) (d) Ia1 (Z2 + Z0).

121. For the system shown in diagram below, a line-to-ground fault on the line side of the
transformer is equivalent to:
(a) A line-to-ground fault on the generator side of the transformer
(b) A line-to-line fault on the generator side of the transformer
(c) A double line-to-ground on the generator side of the transformer
(d) A 3-phase fault on the generator side of the transformer.
×
F
 	
	
122. The positive sequence component of voltage at the point of fault is zero when it is a:
(a) 3-phase fault (b) L-L fault
(c) L-L-G fault (d) L-G fault.

123. Tick out the correct statement:
(a) The negative and zero sequence voltages are maximum at the fault point and decrease
towards the neutral
(b) The negative and zero sequence voltages are minimum at the fault point and increase
towards the neutral
(c) The negative sequence is maximum and zero sequence minimum at the fault point
and decrease and increase respectively towards the neutral.
(d) None of the above.

124. For complete protection of a 3-phase line:
(a) Three-phase and three-earth fault relays are required
(b) Three-phase and two-earth fault relays are required
(c) Two-phase and two-earth fault relays are required
(d) Two-phase and one-earth fault relays are required.

CL WADHWA bits solutions (120-124)

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