MCQOPTIONS
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MCQOPTIONS
This section includes 40 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
A 3 phase over head transmission line is supported by three discs of suspension insulators. The potentials across the first and second insulator are 8 and 11 kV respectively. What is the line voltage and string efficiency? |
| A. | 0.654 and 63.5% |
| B. | 0.375 and 68.3 % |
| C. | 0.527 and 56.34 % |
| D. | 0.287 and 65.258 % |
| Answer» C. 0.527 and 56.34 % | |
| 2. |
A 132 kV transmission line, with the weight of conductor = 680 kg/km, length of span = 260 m, ultimate strength = 3100 kg, safety factor =2. Calculate the height above ground at which the conductor should be supported. Ground clearance required is 10 m. |
| A. | 10.7 m |
| B. | 13.7 m |
| C. | 20.83 m |
| D. | 18.75 m |
| Answer» C. 20.83 m | |
| 3. |
By _______, transient state stability is generally improved. |
| A. | using low inertia machines |
| B. | using high speed governors on machines |
| C. | dispensing with neutral grounding |
| D. | either "using low inertia machines" or "dispensing with neutral grounding" |
| Answer» C. dispensing with neutral grounding | |
| 4. |
A large AC generator, supplying power to an infinite bus, has a sudden short-circuit occurring at its terminals. Assuming the prime mover input and the voltage behind the transient reactance to remain constant immediately after the fault, acceleration of the generator rotor is |
| A. | inversely proportional to the moment of inertia of the volume |
| B. | inversely proportional to the square of the voltage |
| C. | directly proportional to the square of the short circuit current |
| D. | directly proportional to the short circuit power |
| Answer» B. inversely proportional to the square of the voltage | |
| 5. |
A 50 Hz 6 pole 1000 MVA ,44 kV synchronous generator is supplying a full load at the 0.8 lagging power factor. Its output is reduced by 50% due to an electrical fault. So what will be the accelerating torque of the generator immediately after the electrical fault, ignoring the loss and considering that the primary inductive current that drives it is constant? |
| A. | 6/π |
| B. | 24/π |
| C. | 12/π |
| D. | 2/π |
| Answer» D. 2/π | |
| 6. |
In a domestic electric installation, the maximum load permitted in a 16 A power circuit is |
| A. | 5 kW |
| B. | 3 kW |
| C. | 4 kW |
| D. | 10 kW |
| Answer» C. 4 kW | |
| 7. |
If the inertia constant H of a machine of 200 MVA is 2 pu its value corresponding to 400 MVA will be |
| A. | 4 p.u |
| B. | 2 p.u |
| C. | 1 p.u |
| D. | 0.5 p.u |
| Answer» D. 0.5 p.u | |
| 8. |
According to ECBC 2017, new buildings will be awarded ECBC plus status if they are able to demonstrate an energy saving of: |
| A. | 50 percent |
| B. | 35 percent |
| C. | 30 percent |
| D. | 25 percent |
| Answer» C. 30 percent | |
| 9. |
According to CPWD guidelines on electrical work 2013, Exhaust fans for installation in corrosive atmosphere, shall be painted with: |
| A. | Cement based paint |
| B. | Special PVC paint or chlorinated rubber paint |
| C. | Distemper |
| D. | White wash |
| Answer» C. Distemper | |
| 10. |
Consider the equal-area criterion graphs shown in the given figure. When the power system is operating such that A2 < A1(case C), the system is said to be: |
| A. | floating |
| B. | unstable |
| C. | stable |
| D. | critically stable |
| Answer» C. stable | |
| 11. |
An 800 kV transmission line has a maximum power transfer capacity of P. When operated at 400 kV with the series reactance unchanged, the new maximum power transfer capacity is approximately |
| A. | P |
| B. | 2 P |
| C. | P / 2 |
| D. | P / 4 |
| Answer» E. | |
| 12. |
For a fault in a power system, the term critical clearing time is related to, |
| A. | Transient stability limit |
| B. | Reactive power limit |
| C. | Short circuit current limit |
| D. | Steady state stability limit |
| Answer» B. Reactive power limit | |
| 13. |
A 50 MVA, 11 kV, 3-phase generator has a stored energy of 400 MJ, the inertia constant is |
| A. | 4 MJ / MVA |
| B. | 8 MJ / MVA |
| C. | 2 MJ / MVA |
| D. | 16 MJ / MVA |
| Answer» C. 2 MJ / MVA | |
| 14. |
Consider a lossy transmission line with V1 and V2 as the sending and receiving end voltages, respectively. Z and X are the series impedance and reactance of the line, respectively. The steady-state stability limit for the transmission line will be |
| A. | greater than \(\left| {\frac{{{V_{1{V_2}}}}}{X}} \right|\) |
| B. | less than \(\left| {\frac{{{V_1}{V_2}}}{X}} \right|\) |
| C. | equal to \(\left| {\frac{{{V_1}{V_2}}}{X}} \right|\) |
| D. | equal to \(\left| {\frac{{{V_1}{V_2}}}{Z}} \right|\) |
| Answer» C. equal to \(\left| {\frac{{{V_1}{V_2}}}{X}} \right|\) | |
| 15. |
Equal area criteria in power systems is used in the context of |
| A. | Deciding maximum loading for a given excitation |
| B. | Stability of a machine connected to infinite bus bar |
| C. | Stability of power systems in which many machines are connected to infinite bus bar |
| D. | Load distribution between a single machine and load drawn from infinite bus bar |
| Answer» C. Stability of power systems in which many machines are connected to infinite bus bar | |
| 16. |
A 100 MVA generator operates on full-load of 50 Hz frequency. The load is suddenly reduced to 50 MW. The steam valve begins to close only after 0.4 s and if the value of the inertia constant H is 5 s, then the frequency at 0.4 s is nearly |
| A. | 38 Hz |
| B. | 44 Hz |
| C. | 51 Hz |
| D. | 62 Hz |
| Answer» D. 62 Hz | |
| 17. |
Direction: The following item consists of two statements, one labelled as ‘Statement (I)’ and the other as ‘Statement (II)’. Examine these two statements carefully and select the answers to these items using the code given below:Statement (I): Stability of a power system can be improved by using parallel transmission lines.Statement (II): Two transmission lines in parallel will increase the impedance between sending end and receiving end compared to single line. |
| A. | Both Statement I and Statement II are individually true and Statement II is the correct explanation of Statement I |
| B. | Both Statement I and Statement II are individually true but Statement II is not the correct explanation of Statement I |
| C. | Statement I is true but Statement II is false |
| D. | Statement I is false but Statement II is true |
| Answer» D. Statement I is false but Statement II is true | |
| 18. |
Critical clearing angle is related to |
| A. | Stability study of power system |
| B. | Power flow study of power system |
| C. | Regulation of transmission line |
| D. | Power factor improvement of the system |
| Answer» B. Power flow study of power system | |
| 19. |
A 100 MVA, 50 Hz turbo-generator operates at no load at 3000 rpm. A load of 25 MW is suddenly applied to the machine and the steam valve to the turbine commences to open after 0.6 seconds due to the governor time-lag. Assuming the inertia constant H = 5.0 kW-s per kVA of the generator rating, the frequency to which the generated voltage drops before the steam-flow commences to meet the new load is |
| A. | 49. Hz |
| B. | 50.15 Hz |
| C. | 49.24 Hz |
| D. | 49.82 Hz |
| Answer» D. 49.82 Hz | |
| 20. |
For rewirable fuse, employing copper wire as the fusing element, the fusing factor is: |
| A. | 0.7 to 0.8 |
| B. | 1.0 to 1.2 |
| C. | 1.4 to 1.5 |
| D. | 1.9 to 2.0 |
| Answer» E. | |
| 21. |
In a power system, due to interconnection or grid formation and transmission line redundancy, the ability to serve all power demands without failure over long periods of time, is due to |
| A. | Power system quality |
| B. | Power system reliability |
| C. | Computers and microprocessors |
| D. | Reserve generating capacity |
| Answer» C. Computers and microprocessors | |
| 22. |
In the figure shown, self-impedances of the two transmission lines are 1.5j p.u. each, and Zm = 0.5j p.u. is the mutual impedance. Bus voltages shown in the figure are in p.u. Given that δ > 0, the maximum steady-state real power that can be transferred in p.u. from Bus-1 to Bus-2 is |
| A. | |E| |V| |
| B. | 2 |E| |V| |
| C. | \(\dfrac{|E||V|}{2}\) |
| D. | \(\dfrac{3|E||V|}{2}\) |
| Answer» B. 2 |E| |V| | |
| 23. |
If the torque angle ‘delta’ increases indefinitely, the system indicates |
| A. | Steady state stability |
| B. | Permanent stability |
| C. | Instability |
| D. | None of the above |
| Answer» D. None of the above | |
| 24. |
For transient stability analysis, as long as equal area criterion satisfied, the maximum angle to which rotor angle can oscillate is |
| A. | 90° |
| B. | 45° |
| C. | Greater than 90° |
| D. | Less than 90° |
| Answer» D. Less than 90° | |
| 25. |
An alternator having an induced emf of 1.6 pu is connected to an infinite bus of 1.0 pu. If the bus bar has reactance of 0.6 pu and alternator has reactance of 0.2 pu, what is the maximum power that can be transferred? |
| A. | 2 pu |
| B. | 2.67 pu |
| C. | 5 pu |
| D. | 6 pu |
| Answer» B. 2.67 pu | |
| 26. |
A 3 Phase, 50 Hz Synchronous generator is connected to an infinite bus through a transformer and two parallel transmission lines. The input mechanical power to synchronous generator is 0.8 p.u. Grid is consuming a power of 0.8 + j0.4 p.u. Generator impedance is 0.25 p.u., transformer impedance is 0.5 p.u. and each transmission line impedance is 0.5 p.u. If the infinite bus voltage is 1∠0 p.u then, what is the generator voltage load angle? |
| A. | 26.56° |
| B. | 31.30° |
| C. | 30° |
| D. | 60° |
| Answer» D. 60° | |
| 27. |
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° |
| Answer» C. 60° to 75° | |
| 28. |
Direction: The following item consists of two statements, one labelled as ‘Statement (I)’ and the other as ‘Statement (II)’. Examine these two statements carefully and select the answers to these items using the code given below:Statement (I): Equal-area criterion can be used to determine the stability of single machine infinite bus system.Statement (II): An infinite bus system has infinite inertia and constant voltage. |
| A. | Both Statement I and Statement II are individually true and Statement II is the correct explanation of Statement I |
| B. | Both Statement I and Statement II are individually true but Statement II is not the correct explanation of Statement I |
| C. | Statement I is true but Statement II is false |
| D. | Statement I is false but Statement II is true |
| Answer» C. Statement I is true but Statement II is false | |
| 29. |
A 3 Phase, 50 Hz synchronous generator is connected to an infinite bus. The maximum power that can be transferred to infinite bus is 1 p.u. The mechanical input to the generator is \(\frac{{\sqrt 3 }}{2}\) p.u. Inertia constant of the generator is 5s. Find the natural frequency of oscillation of the system? |
| A. | \(\sqrt {10\pi }\) rad/sec |
| B. | \(\sqrt {20\pi }\) rad/sec |
| C. | \(\sqrt {15\pi }\) rad/sec |
| D. | \(\sqrt {5\pi }\) rad/sec |
| Answer» E. | |
| 30. |
A 2-pole, 50 Hz, 11 kV, 100 MW alternator has a moment of inertia of 10,000 kg.m2. The value of inertia constant, H is |
| A. | 3.9 s |
| B. | 4.3 s |
| C. | 4.6 s |
| D. | 4.9 s |
| Answer» E. | |
| 31. |
Equal-Area Criterion is employed to determine |
| A. | The steady state stability |
| B. | The transient stability |
| C. | The reactive power limit |
| D. | The rating of a circuit breaker |
| Answer» C. The reactive power limit | |
| 32. |
In a power system, which of the following is/are critical clearance time of a fault related to?1. Transient reactance2. Sub-transient reactance3. Reactive power limit4. Transient stability limit |
| A. | 1 and 2 |
| B. | 2 only |
| C. | 3 and 4 |
| D. | 4 only |
| Answer» E. | |
| 33. |
A 90 MW, 11 kV water wheel generator has an inertia constant H = 3. The stored energy in the rotor at synchronous speed is: |
| A. | 40 kJ |
| B. | 270 kJ |
| C. | 270 MJ |
| D. | 40 MJ |
| Answer» D. 40 MJ | |
| 34. |
______ has a maximum life tenure. |
| A. | Wooden Poles |
| B. | Steel Poles |
| C. | Concrete Poles |
| D. | Steel Towers |
| Answer» E. | |
| 35. |
According to general practice, the land required for a 400 kV substation is _______. |
| A. | 30 acres |
| B. | 10 acres |
| C. | 50 acres |
| D. | 20 acres |
| Answer» D. 20 acres | |
| 36. |
Consider a step voltage wave of magnitude 1pu travelling along a lossless transmission line that terminates in a reactor.The voltage magnitude across the reactor at the instant the travelling wave reaches the reactor is |
| A. | 1pu |
| B. | 1pu |
| C. | 2pu |
| D. | . 3pu |
| Answer» B. 1pu | |
| 37. |
A cylindrical rotor generator delivers 0.5 pu power in the steady-state to an infinite bus through a transmission line of reactance 0.5 pu. The generator no-load voltage is 1.5 pu and the infinite voltage is 1.5 pu. The inertia constant of the generator is 5MW-s/MV and the generator reactance is 1 pu.The critical clearing angle, in degrees, for a three-phase dead short circuit fault at the generator terminal is |
| A. | 53.5 |
| B. | 60.2 |
| C. | 70.8 |
| D. | 79.6 |
| Answer» E. | |
| 38. |
How many 200W/220V incandescent lamps connected in series would consume the same total power as a single 100W/220V incandescent lamps? |
| A. | Not possible |
| B. | .4 |
| C. | 3 |
| D. | .2 |
| Answer» C. 3 | |
| 39. |
For a fixed value of complex power flow in a transmission line having a sending end voltage V, the real power loss will be proportional to |
| A. | V |
| B. | V2 |
| C. | 1/V2 |
| D. | 1/V |
| Answer» D. 1/V | |
| 40. |
A 500MW, 21kV, 50Hz, 3-phase, 2-pole synchronous generator having a rated p.f. =0.9, has a moment of inertia of 27.5 x 103 kg-m2. The inertia constant (H) will be |
| A. | 2.44 s |
| B. | 2.71s |
| C. | 4.88s |
| D. | 5.42s |
| Answer» B. 2.71s | |