2. The positive and negative halves of a complex wave are symmetrical when
Correct : C. it contains odd harmonics
3. The rms value of the complex voltage given by v = 161i sin cot + 12 Ari sin Rot is
Correct : B. 20
4. In a 3-phase system,the harmonic has negative phase sequence of RBY.
Correct : C. 5
5. Two complex waves will have the same wave-shape if
Correct : D. they have all of the above
6. The trigonometric Fourier series for a complex wave will contain positive cosine
terms only when
Correct : C. its value is zero at 0= n/2, 3n/2 etc.
7. Tansient disturbance is produced in a circuit whenever
Correct : D. all of the above
8. There are no transients in pure resistive circuits because they
Correct : C. have no stored energy
9. Transient current in electrical circuits are associated with
Correct : D. both (a) and (b)
10. The transients which are produced due to sudden but energetic changes from one
steady state of a circuit to another are called transients.
Correct : B. transition
11. In an R-L circuit connected to an alternating sinusoidal voltage, size of transient current primarily depends on
Correct : A. the instant in the voltage cycle at which circuit is closed
12. Double-energy transients are produced in circuits consisting of
Correct : D. resistance, inductance and capacitance
13. The transient current in a loss-free L-C circuit when excited from an ac source is
a/an sine wave.
Correct : B. undamped
14. Transient current in an R-L-C circuit is oscillatory when
Correct : C. R <2
15. For measuring positive, negative and zero sequence voltages in a system, the
reference is taken as :
Correct : D. None of the above
16. The most economic load on an underground cable is :
Correct : B. Less thart the surge loading
17. In case of a 3-phase short circuit is a system, the power fed into the system is :
Correct : A. Mostly reactive
18. An RLC series circuit remains predominantly inductive :
Correct : C. Above resonance frequency
19. A generator is connected to a synchronous motor. From stability point of view it is preferable to have :
Correct : D. Generator neutral resistance and motor neutral reactace grounded
20. The positive sequency component of voltage at the point of fault is zero when it is a :
Correct : C. L-L-G fault
21. Tick out the correct statement :
Correct : D. None of the above
22. The order of the lightning discharge current is :
Correct : A. 10,000 amp
23. The magnetising-inrush-current in a transformer is rich in :
Correct : C. 7th harmonics
24. The in-rush current of a transformer at no load is maximum if the supply voltage is
switched on
Correct : A. At zero voltage value
25. Pure inductive circuit takes power (reactive) from the a.c. line when
Correct : C. applied voltage decreases but current increases
26. With 100% series compensation of lines
Correct : D. (a) and (b)
27. In a pure LC parallel circuit under resonance condition, current drawn from the supply mains is
Correct : D. Zero
28. A lightning arrestor connected between the line and earth in a power system
Correct : A. protects the terminal equipment against travelling surges
29. Lightning arresters are used in power systems to protect electrical equipments against
Correct : A. direct strokes of lightning
30. Consider the following statements : The transient stability of the power system under unbalanced fault conditions can be effectively improved by
1. Excitation control
2. phase-shifting transformer
3. single-pole switching of circuit breakers
4. increasing the turbine input. Of these statements
Correct : C. 3 and 4 are correct
31. One current transformer (CT) is mounted over a 3-phase 3-core cable with its sheath and armour removed from the portion covered by the CT. An ammeter placed in the CT secondary would measure
Correct : D. three times the zero sequence
32. Earth wire on EHV overhead transmission line is provided to protect the line
against
Correct : A. lightning surge
33. The velocity of travelling wave through a cable of relative permittivity 9 is
Correct : C. 108 m/s
34. A wave-trap is used at the termination of a HVAC overhead line to a station switchyard to
Correct : D. provide for carrier communication
35. Shunt compensation in an EHV line is used to improve
Correct : B. fault level and voltage profile
36. The principal information obtained from load flow studies in a power system are
1. magnitude and phase angle of the voltage at each bus.
2. reactive and real power flows in each of lines.
3. total power loss in the network.
4. Transient stability limit of the system Select the correct answer from the codes given below :
Correct : C. 1,2 and 3
37. While rising and while falling, if a wave is symmetrical, it contains
Correct : B. odd harmonics in addition to fundamental
38. While rising and falling if a wave is not symmetrical, it contains
Correct : A. even harmonics in addition to fundamental
39. The main reason for generation of harmonics in a transformer could be
Correct : D. saturation of core
40. Harmonics in transformer result in
Correct : D. all of the above
41. Which fractional pitch will eliminate the seventh harmonic from the voltage waveform of an alternator?
Correct : A. 6/7
42. Most of the power quality problems are related to ______
Correct : B. Grounding Issue
43. Which of the following is not considered as good power quality voltage
Correct : A. Power Supply is more compared to demand
44. Lightening and Tree striking on a live conductor is an example________ Power
Quality issue.
Correct : B. Voltage Swell
45. Interruption is
Correct : B. complete loss of voltage
46. The Transients in the power system occurs for
Correct : C. less than one complete cycles
47. The most common cause of long interruption is ______
Correct : C. Both (a) & (b)
48. Outage is the
Correct : A. Removal of Primary Component
49. Single Phase Tripping is generally used in _________________.
Correct : A. Transmission System
50. The Short Interruptions occurs for
Correct : C. less than one complete cycles
51. The most common way to calculate voltage sag is from ______
Correct : C. RMS Voltage
52. Effect of temperature rise in overhead lines is to
Correct : A. Increase Sag Decrease Tension
53. What should be the value of sag for proper operation of overhead transmission line?
Correct : C. Neither too low nor too high
54. Voltage dips cannot be caused by which of the following:
Correct : D. Capacitive Switching
55. Which one of the following cannot be possible with voltage surges:
Correct : C. Flicker in Incandescent Lamps
56. During sag, power electronic component will trip, this will decrease ______
Correct : C. Load Current
57. The total power taken by the load remains constant so that _____ will be higher
Correct : A. Current
58. The major cause of voltage sag is
Correct : D. All the above
59. To obtain a constant current input, a inductor is placed in current source inductor
(CSI) in:
Correct : B. Series
60. The harmonic current distortion in adjustable speed drive is_____
Correct : B. Not Constant
61. Reducing the number of short-circuit faults in a system, reduces ______
Correct : C. Sag & Interruptions
62. Current-limiting fuses are able to clear a fault within one _______.
Correct : A. Half cycle
63. By implementing changes in the supply system, the severity of the event will__.
Correct : A. Reduce
64. The main mitigation equipments is___
Correct : D. All the above
65. During normal operation, the UPS takes its power from the supply, rectifies the ac
voltage to dc and inverts it again to ac with the
Correct : A. same frequency and rms value
66. What is the value of transient stability limit?
Correct : B. Lower than steady state stability limit.
67. By using which component can the transient stability limit of a power system be improved?
Correct : B. Series capacitor
68. What is transient stability limit?
Correct : C. The maximum flow of power through a particular point in the power system without loss of stability when large and sudden disturbances occur
69. Which among the following methods is used for improving the system stability?
Correct : D. All of these
70. What is steady state stability limit?
Correct : A. The maximum flow of power through a particular point in the power system without loss of stability when small disturbances occur.
71. Which among these is a classification of power system stability?
Correct : D. All of these
72. The stability of the power system is not affected by which among these?
Correct : B. Line losses
73. What is power system stability?
Correct : B. The ability of the power system to regain the state of operating equilibrium point when the system is subjected to any disturbances.
74. Power factor can be mathematically expressed as:
Correct : A. P/Q
75. The power factor angle of a purely inductive circuit is:
Correct : D. 90 degree
76. In a load comprising of resistance and inductance:
Correct : A. Load current lags voltage
77. The power factor of capacitive circuits is:
Correct : A. Leading
78. A circuit having poor power factor will draw:
Correct : D. High current
79. The power factor of purely inductive circuits is:
Correct : B. Lagging
80. A 500 kVA circuit drawing 200 kW and an inductive load requires how much capacitance to obtain unity power factor:
Correct : C. 300
81. Which of the following statement refer to IEEE definition on power quality?
Correct : D. The concept of powering and grounding sensitive electronic equipment in a manner suitable for the equipment.
82. Which of the following explains the reasons for concern with power quality?
Correct : A. End-user equipment become more sensitive to power quality due to many microprocessor-based controls
83. The following statement describes the effects of poor power quality, EXCEPT
Correct : C. Premature failure of equipment
84. Since most of the industrial loads are inductive type, which of the following will help to correct the power factor?
Correct : B. Compensate lagging reactive current by supplying leading reactive current to the power system
85. Which of the following is an advantages of power factor correction (PFC)?
Correct : B. Power consumption reduced
86. Which of the following represents short duration voltage variation?
Correct : C. Voltage Outage
87. Which of the following terms describes the transient voltage variation?
Correct : D. It can be caused by lightning, electrostatic discharge or load switching.
88. Which of the following terms describes the effects of harmonics to industrial power systems?
Correct : A. Disturbance to Electric and Electronic Devices