MCQOPTIONS
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MCQOPTIONS
This section includes 249 Mcqs, each offering curated multiple-choice questions to sharpen your Power Systems knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
The critical clearing time of a fault in power systems is related to |
| A. | reactive power limit |
| B. | short-circuit current limit |
| C. | steady-state stability limit |
| D. | transient stability limit |
| Answer» E. | |
| 52. |
An industrial consumer has a daily load pattern of 2000 kW, 0.8 lag for 12 Hrs and 1000 kW UPF for 12 Hrs. The load factor is _______ |
| A. | 0.04 |
| B. | 0.06 |
| C. | 0.6 |
| D. | 6.0 |
| Answer» D. 6.0 | |
| 53. |
A 220 V, 8 kW, 50 Hz, 1 motor working at full load with an efficiency of 85% has a power factor of 0.8 lagging. If a capacitor is connected across the motor terminals to raise the overall power factor to unity, then current through the capacitor will be |
| A. | 33.5 amps |
| B. | 32.0 amps |
| C. | 30 amps |
| D. | 41 amps |
| Answer» C. 30 amps | |
| 54. |
A 3 induction motor takes 120 kW at 415 V, 50 Hz and a power factor of 0.8 lagging. What is the capacitance per phase, if its power factor is improve to 0.9 and capacitor bank is connected in star ? |
| A. | 587 F |
| B. | 440 F |
| C. | 560 F |
| D. | 600 F |
| Answer» B. 440 F | |
| 55. |
A 3 induction motor takes 100 kW at 415 V, 50 Hz and a power factor of 0.80 lagging. What is the kVAr rating of a capacitor bank to improved the power factor to 0.9 lagging, if the capacitor bank is connected to delta ? |
| A. | 6.25 |
| B. | 7.99 |
| C. | 7.91 |
| D. | 8.82 |
| Answer» E. | |
| 56. |
In the above question find the sending end voltage of the tran86.314smission line ________ kV/ph |
| A. | 86200 |
| B. | 8.265 |
| C. | 86.314 |
| D. | 880.5 |
| Answer» D. 880.5 | |
| 57. |
A three phase line, 20 km long, delivers 10 MW at 11kV, 50 Hz, 0.8 power factor lagging. The power losses in the line is 10 percent of the power delivered. The resistance of the each onductor will be _________ . |
| A. | 0.774 |
| B. | 774 |
| C. | 77.4 |
| D. | 77.4 |
| Answer» B. 774 | |
| 58. |
A 5kVA, 400/2000 volt, 50Hz, 1 transformer has primary and secondary leakage reactance each of 2.5 . The total reactance in p.u. will be _____p.u. |
| A. | 390 p.u. |
| B. | 39.0 p.u. |
| C. | 03.90 p.u. |
| D. | 0.390 p.u. |
| Answer» E. | |
| 59. |
A two conductor 1 line operates at 50 Hz. The diameter of each conductor is 20 mm and the spacing between the conductors is 3m. The height of conduct or above the ground is 6m. The capacitance of the line to neutral will be ________pF/m |
| A. | 0.97 pF/m |
| B. | 97 pF/m |
| C. | 97.7 pF/m |
| D. | 9.7 pF/m |
| Answer» E. | |
| 60. |
A three phase 50 Hz line consists of three conductors each of diameter 21 mm. The spacing between the conductors as follows: A B = 3m, B C = 5m, C A = 3.6 m |
| A. | 51703 VAr. |
| B. | 5.1703 VAr. |
| C. | 517.03 VAr. |
| D. | 5170.3 VAr. |
| Answer» B. 5.1703 VAr. | |
| 61. |
The capacitance of a 3 core lead sheathed cable measured between any two of the conductors with sheath earthed is 0.19 F per km. The kvA required to keep 16 kms of the cable charged when connected to 20 k V, 50 Hz supply will be ______kVA |
| A. | 763 kVA. |
| B. | 7.63 kVA. |
| C. | 76.3 kVA. |
| D. | 0.763 kVA. |
| Answer» B. 7.63 kVA. | |
| 62. |
The surge impedance of 50 miles long underground cable is 50 ohm. For a 25 miles length it will be ________ ohms |
| A. | 5.05 |
| B. | 0.05 |
| C. | 0.5 |
| D. | 50 |
| Answer» E. | |
| 63. |
A cable has following characteristics: |
| A. | 1592.4 |
| B. | 15924 |
| C. | 159.24 |
| D. | 15.924 |
| Answer» D. 15.924 | |
| 64. |
A 60 Hz, 320 km lossless line has sending end voltage 1.0 p.u. The receiving end voltage on onload is _________ p.u. |
| A. | 1.088 |
| B. | 1088 |
| C. | 10.88 |
| D. | 108.8 |
| Answer» B. 1088 | |
| 65. |
A 66 kV system has string insulator having five discs and the earth to disc capacitance ratio at 0.10. The string efficiency will be ________% |
| A. | 60.7 |
| B. | 6.07 |
| C. | 67 |
| D. | 6.7 |
| Answer» D. 6.7 | |
| 66. |
An overhead line having a surge impedance of 400 is connected in sereis with an underground cable having a surge impedance of 100 . If a source of 50 kV travels from the line end towards the line-cable junctions, the value of the transmitted volt age wave at the junction is ________ kV |
| A. | 20 |
| B. | 0.20 |
| C. | 0.002 |
| D. | 200 |
| Answer» B. 0.20 | |
| 67. |
A voltage of 1000 kV is applied to an overhead line with its receiving end open. If the surge impedance of the line is 500 ohm, then the total surge power in the line is _________ MW |
| A. | 20.26 |
| B. | 2000 |
| C. | 20.00 |
| D. | .020 |
| Answer» C. 20.00 | |
| 68. |
The per unit impedance of a circuit element is 0.15. If the base kV and base MVA are halved, then the new value of the per unit impedance of the circuit element will be ___________ |
| A. | 30.3 |
| B. | 0.030 |
| C. | 0.30 |
| D. | 30 |
| Answer» D. 30 | |
| 69. |
An alternator having induced emf of 1.6 p.u. is connected to an intinite bus of 1.0 p.u. If the bus has reactance of 0.6 p.u. and alter nator has reactance of 0.2 p.u., the maximum power that can be transferred is given by ________ p.u. |
| A. | 2 p.u |
| B. | 20.2 p.u |
| C. | 0.02 p.u |
| D. | 0.2 p.u |
| Answer» B. 20.2 p.u | |
| 70. |
A power station consists of two synchronous gener at or s A and B of rating 250 M VA and 500 M VA with inertia 1.6 p.u. and 1 p.u. respectively on their own base MVA ratings. The equivalent P.U inertia for the system on 100 MVA common base will be ____________ |
| A. | 9 p.u. |
| B. | 9.99 p.u. |
| C. | 9.09 p.u. |
| D. | 0.09 p.u. |
| Answer» B. 9.99 p.u. | |
| 71. |
If transformer frequency is changed from 50 Hz, to 60 Hz the ratio of eddy current loss 60 Hz, to 50 Hz at constant voltage will be __________ |
| A. | 1 |
| B. | 0.1 |
| C. | .001 |
| D. | 1.01 |
| Answer» B. 0.1 | |
| 72. |
A single line to ground fault occurs on an unloaded generator in phase a. If x |
| A. | 375 |
| B. | 3.75 |
| C. | 37.5 |
| D. | 0.375 |
| Answer» D. 0.375 | |
| 73. |
A 50 Hz alternator is rated 500 MVA, 20 kV, with X |
| A. | 3.022 |
| B. | 3.22 |
| C. | 53.26 |
| D. | 542.5 |
| Answer» C. 53.26 | |
| 74. |
A consumer has a maximum demand of 60 kW at 0.50 load factor. If tariff is 750 per kW of maximum demand plus 1.20 per kWh, then overall cost per kWh, will be _________ |
| A. | 137 |
| B. | 1.37 |
| C. | 13.7 |
| D. | 0.137 |
| Answer» B. 1.37 | |
| 75. |
A power system has two generating plants and the power is being dispatched economically with P |
| A. | 1.25 |
| B. | 12.5 |
| C. | 1.25 |
| D. | 0.125 |
| Answer» D. 0.125 | |
| 76. |
A 3 supply, 5 kW induction motor has a power fact or 0.75 lagging. A bank of capacitors is connected in delta across the supply terminals and power factor raised to 0.9 lagging. kVAR rating of the capacitors connected in each phase, will be _________ kVAr |
| A. | 0.663 kVAr |
| B. | 66.3 kVAr |
| C. | 663 kVAr |
| D. | 660.3 kVAr |
| Answer» B. 66.3 kVAr | |
| 77. |
In a power system with negligible resistance, the fault current at a point is 8.00 p.u. The series reactance to be included at the fault point to limit the short-circuit current to 5.00 p.u. is ______p.u. |
| A. | 3000 |
| B. | 3.000 |
| C. | 0.300 |
| D. | 30.00 |
| Answer» C. 0.300 | |
| 78. |
Four identical alternators each rated for 20 MVA, 11 KV having a subtransient reactance of 16% are working in parallel. The short-circuit level at the bus bars is _______ MVA |
| A. | 5.00 |
| B. | 500 |
| C. | 0.524 |
| D. | 0.52 |
| Answer» C. 0.524 | |
| 79. |
A power system network with the capacity at 100 MVA has a source impedance at 10% at a point. The fault at that point is __________ MVA |
| A. | 1000 MVA |
| B. | 10.7 MVA |
| C. | 10.1MVA |
| D. | 10.00 MVA |
| Answer» B. 10.7 MVA | |
| 80. |
Determine the correctness or otherwise of the following Assertion [a] and the Reason [r]. |
| A. | Both [a] and [r] are true and [r] is the correct reason for [a]. |
| B. | Both [a] and [r] are true and [r] is not the correct reason for [a]. |
| C. | Both [a] and [r] are false. |
| D. | [a] is false and [r] is true. |
| Answer» E. | |
| 81. |
The synchronizing coefficient between two areas of the 2-area power system is (symbols have usual meanings) |
| A. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> P</center></td></tr><tr><td style="text-align: center;"> |V|</td></tr></table> |
| B. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> P</center></td></tr><tr><td style="text-align: center;"> </td></tr></table> |
| C. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> P</center></td></tr><tr><td style="text-align: center;"> </td></tr></table> |
| D. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> P</center></td><td rowspan="2">6</td></tr><tr><td style="text-align: center;"> Q</td></tr></table> |
| Answer» C. <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> P</center></td></tr><tr><td style="text-align: center;"> </td></tr></table> | |
| 82. |
A 3-phase transformer has rating of 20MVA, 220 kV (star) + 33 kV (delta) with leakage reactance of 12%. The transformer reactance (in ohms) referred to each phase of the L.V. delta-connected side is _________ |
| A. | 19.6 |
| B. | 196 |
| C. | 15.8 |
| D. | 152.6 |
| Answer» B. 196 | |
| 83. |
Transmission line has a total series reactance of 0.2 p.u. Reactive power compensation is applied at the midpoint of the line and it is controlled such that midpoint voltage of the transmission line is always maintained at 0.98 pu. If voltage at both ends of the line are maintanined at 1.0 pu, then steady state power transfer limit of the transmission line is _________ pu |
| A. | 1 |
| B. | 5 |
| C. | 3 |
| D. | 7 |
| Answer» C. 3 | |
| 84. |
A 500 MVA, 11 kV sychronous generator has 0.2 p.u. synchr onous r eact ance. The p.u. synchronous reactance on the base values of 100 MVA and 22 kV is __________ |
| A. | 4 |
| B. | 0.4 |
| C. | 0.04 |
| D. | 4.04 |
| Answer» B. 0.4 | |
| 85. |
If two pole 50 Hz, 50 MVA turbogenerator has a moment of inertia of 8.6 10 kg-m , then inretia constants H in MJ/MVA will be __________ |
| A. | 8.48 |
| B. | 84.8 |
| C. | 848 |
| D. | 0.848 |
| Answer» D. 0.848 | |
| 86. |
A surge of 15 kV magnitude travels along a cable towards its junction with a overhead line. If inductance and capacitance of the cable and overhead line are respectively 0.3 mH, 0.4 H and 1.5 mH, 0.012 H per km, the voltage rise at the junction due to the surge, will be ________ kV |
| A. | 27.87 |
| B. | 2.787 |
| C. | 278.7 |
| D. | 2787 |
| Answer» B. 2.787 | |
| 87. |
A 50 Hz, four-pole turboalternator rated at 20 MVA, 13 2 kV has an inertia constant H = 4 kW sec/kVA. The kinetic energy stored in the rotor at __________ MJ |
| A. | 0.80 |
| B. | 8.0 |
| C. | 80 |
| D. | 0.08 |
| Answer» D. 0.08 | |
| 88. |
If two pole 50 Hz, 50 MVA turbogenerator has a moment of inertia of 9 10 kg-m , then kinetic energy in MJ at rated speed will be _________ MJ |
| A. | 4.44 |
| B. | 44.4 |
| C. | 0.444 |
| D. | 444 |
| Answer» E. | |
| 89. |
A power station consists of two sychronous generators A and B or ratings 250 MVA and 500 MVA with inertia 1.6 p.u. and 1 p.u.respectively on their own base MVA ratings. The equivalent p.u. inertia constant for the system on 100 MVA common base is ____________ |
| A. | 615 |
| B. | 6.15 |
| C. | 61.5 |
| D. | 0.615 |
| Answer» E. | |
| 90. |
A power system has two synchronous generators. The governor-turbine characteristics orresponding to the generators are |
| A. | 0.48 Hz. |
| B. | 48 Hz. |
| C. | 4.08 Hz. |
| D. | 4.8 Hz. |
| Answer» C. 4.08 Hz. | |
| 91. |
A 100 M VA, 11 k V 3-phase, 50 H z, 8-pol e synchronous generator has an inetria constant H equal to 4 seconds. The stored energy in the rotor of the generator at synchronous speed will be |
| A. | 8.00 |
| B. | 80.0 |
| C. | 800 |
| D. | .08 |
| Answer» D. .08 | |
| 92. |
The line currents in ampere in phases a, b and c respectively are (400 + j100), (75 j600) and ( 300 + j500) referred to the same reference vector. The negative sequence components of currents will be _______ Amp. |
| A. | 151.9 |
| B. | 159.9 |
| C. | 148.9 |
| D. | 149.9 |
| Answer» E. | |
| 93. |
A small generating station has a busbar divided into three sections each section is connected to a tie bar with reactor each rated at 5 mVA, 0.1 p.u. reactance. A generator of 8mVA, rating and 0.15 p.u. reactance is connected to each section of the busbar. The short circuit capacit y of the breaker, if a 3 fault takes place on one of the sections of the busbar, will be _________ mVA |
| A. | 7.873 MVA |
| B. | 78.73 MVA |
| C. | 787.3 MVA |
| D. | 7873 MVA |
| Answer» C. 787.3 MVA | |
| 94. |
If the inductance and capacitance of a system are 1 0 H and 0 01 F respectively and the instantaneous value of current interrupted is 10 amp, the voltage across the breaker contacts will be __________ kV |
| A. | 101 |
| B. | 100 |
| C. | 99 |
| D. | 9.9 |
| Answer» C. 99 | |
| 95. |
The primary mmf is least affect ed by the secondary terminal conditions in a |
| A. | power transformer |
| B. | potential transformer |
| C. | current transformer |
| D. | distribution transformer. |
| Answer» D. distribution transformer. | |
| 96. |
The inertia constant H of a machine of 200 MVA is 2 p.u. Its value corresponding to 400 MVA will be _________ |
| A. | 1 |
| B. | 0.1 |
| C. | 0.001 |
| D. | 1.1 |
| Answer» B. 0.1 | |
| 97. |
If a 75 MVA, 10 kV synchronous generator has X |
| A. | 44 |
| B. | 0.44 |
| C. | 4.4 |
| D. | 0.04 |
| Answer» C. 4.4 | |
| 98. |
In the integral control of single area system, when system frequency error is reduced to zero |
| A. | integrator output and speed changer position attain a constant value |
| B. | integrator output increases but speed changer position also comes down |
| C. | integrator output decreases and speed changer position also comes down |
| D. | integrator output decreases but speed changer position moves up |
| Answer» E. | |
| 99. |
During a disturbance on a synchronous machine, the rotor swings from A to B before finally settling down to a steady state at point C on the power angle curve. The speed of the machine during oscillation is synchronous at point(s) |
| A. | A and B |
| B. | A and C |
| C. | B and C |
| D. | only at C |
| Answer» B. A and C | |
| 100. |
The transient stability of the power system can be effectively improve by |
| A. | excitation control |
| B. | phase shifting transformer |
| C. | single pole switching of circuit breakers |
| D. | increasing the turbine valve opening |
| Answer» B. phase shifting transformer | |