About Power Systems

Following are some of the multiple choice questions on the Power Systems with answers that will help the students in developing their knowledge.

Power Systems MCQ

1. How much wind power does India hold?

  • 20,000 MW
  • 12,000 MW
  • 140,000 MW
  • 5000 MW

2. The overall efficiency of thermal power plant is equal to

  • Rankine cycle efficiency
  • Carnot cycle efficiency
  • Regenerative cycle efficiency
  • Boiler efficiency x turbine efficiency x generator efficiency

3. Solar thermal power generation can be achieved by

  • using focusing collector or heliostates
  • using flat plate collectors
  • using a solar pond
  • any of the above system

4. At what range of speed is the electricity from the wind turbine is generated?

  • 100 – 125 mph
  • 450 – 650 mph
  • 250 – 450 mph
  • 30-35 mph

5.  What should be the value of earthing resistance for large power stations?

  • 1 Ω
  • 0.5 Ω
  • 2 Ω
  • 5 Ω

6. When did the development of wind power in India began?

  • 1965
  • 1954
  • 1990
  • 1985

7.  If the load current decreases then the power factor

  • Will also decrease
  • Will increase
  • Will remains unchanged
  • None of these

8. Power factor of a load can be improved by using

  • Static capacitors
  • Synchronous condenser
  • Phase advancer
  • All of the above

9. Which of the following is not the distribution system normally used

  • 3 phase-4 wire
  • 3 phase-3 wire
  • Single phase - 3 wire
  • Single phase -4 wire.

10. Which type of system is generally adopted for the generation and transmission of electrical power?

  • 3 phase 4 wire
  • 2 phase 3 wire
  • 3 phase 3 wire
  • None of these

11. The steady state stability of the power system can be improved by

  • Increasing the number of parallel lines between the transmission points
  • Connecting capacitors in series with the line
  • Reducing the excitation of the machines
  • Both a and b

12. The stability of the power system is not affected by which among these?

  • Generator reactance
  • Line losses
  • Excitation of generators
  • All of these

13. Various power system faults in increasing order of severity are

  • LG,LL,LLG,LLLG
  • LLLG,LLG,LG,LL
  • LLG,LLLG,LL,LG
  • LL,LG,LLLG,LLG

14. What percentage of fault occurring in the power system is line to line fault

  • 5 %
  • 30 %
  • 25 %
  • 15 %

15. A _________ distribution system is more reliable than the ______ distribution system.

  • parallel, radial
  • parallel, ring
  • radial, parallel
  • ring, parallel

16. The amount of energy available in the wind at any instant is proportional to ___ of the wind speed.

  • Square root power of two
  • Square root power of three
  • Square power
  • Cube power

17. What is the expression for fault current in line to line fault?

  • If = √3 * (Ea / Z1 + Z2)
  • If = 3 * (Ea / Z1 + Z2)
  • If = √3 * (Ea / Z1 + Z2 + Z0)
  • If = 3 * (Ea / Z1 + Z2 + Z05)

18. Winds having following speed are suitable to operate wind turbines.

  • 5 – 25m/s
  • 10 – 35m/s
  • 20 – 45m/s
  • 30 – 55m/s

19. The rated voltage of a 3 phase power system is given by

  • rms peak voltage
  • Peak phase voltage.
  • rms line to line voltage
  • Peak line to line voltage.

20. What are the terminal conditions in case of SLG fault, if the fault occurs in the phase A?

  • Vb = 0, Ia = 0, Ic = 0
  • Va = 0, Ib = 0, Ic = 0
  • Va = 0, Ia = 0, Ic = 0
  • Vb = 0, Ia = 0, Ib = 0

21. The generating voltage and frequency in India is about?

  • 11 kV and 60 Hz
  • 11 kV and 50 Hz
  • 220 kV and 60 Hz
  • 220 kV and 50 Hz

22. The advantage of neutral earthing is

  • Freedom from persistent arcing grounds
  • Over voltages due to lightning can be discharged to earth
  • Simplified design earth fault protection
  • All of the above

23. When a line-to-line fault occurs, the short circuit current of an alternator depends upon its

  • Sub transient reactance
  • Transient reactance
  • Synchronous reactance
  • Short circuit reactance

24. Base impedance of the power system is given as:

  • (Base kV)2/Base MVA
  • (Base kV)/Base MVA
  • Base MVA/(Base kV)2
  • None of these

25. If power factor is less than unity then it will result in

  • Large kVA rating of equipment
  • Greater conductor size
  • Large copper losses
  • All of the above

26. Which of the following type of reactors are popularly used in power systems?

  • Compensation reactors
  • Current limiting reactors
  • Suppression or Peterson reactors
  • All of these

27. While designing the distribution to locality of one lac population with medium dense load requirement, we can employ ___________

  • radial system
  • parallel system
  • ring main system
  • any of the mentioned

28. Skin effect is proportional to

  • diameter of conductor
  • (diameter of conductor)1/2
  • (diameter of conductor )2
  • none

29. What are the common assumptions made for the equal area criterion?

  • The transmission line and machine resistances are neglected
  • Rotor speed of the machine is constant
  • Mechanical input remains constant.
  • All of these

30. In India largest thermal power station is located at

  • Kota
  • Sarni
  • Chandrapur
  • Neyveli

31. . One would design the feeders of the transmission system based on its ____________

  • a) current capacity
  • b) voltage drop
  • c) operating voltage
  • d) all of the mentioned

32. The amount of photo generated current increases slightly with increase in _________

  • Temperature
  • Photons
  • Diode current
  • Shunt current

33. The load flow solution is always assured in case of:

  • Newton-Raphson method
  • Gauss method
  • Gauss-Seidel method
  • None of these methods guarantees

34. In a star connected system without neutral grounding, zero sequence currents are

  • Zero
  • Phaser sum of phase currents
  • Same as r.m.s. value of phase currents
  • Same as peak value of phase currents

35. When alternating current passes through a conductor

  • it remains uniformly distributed throughout the section of conductor
  • portion of conductor near the surface carries more current as compared to the core
  • portion of conductor near the surface carries less current as compared to the core
  • entire current passes through the core of the conductor.

36. Wind energy is harnessed as ______ energy with the help of windmill or turbine.

  • Mechanical
  • Solar
  • Electrical
  • Heat

37. A’ is an operator used to symmetrical component analysis

  • Which rotates the vector, it operates upon, through an angle 90° in the clockwise direction
  • Which rotates the vector, it operates upon, through an angle 120°, in the counter-clockwise direction
  • Which rotates the vector, it operates upon, through an angle 120°, in the clockwise direction
  • Which rotates the vector, it operates upon, through an angle 240°, in the clockwise direction

38. By using which component can the transient stability limit of a power system be improved?

  • Series resistance
  • Series capacitor
  • Series inductor
  • a. Shunt resistance

39. For the given distribution system the maximum voltage at the midpoint will be ________

  • 155.6 V
  • 311.12 V
  • 622 V
  • 220 V

40. In overhead transmission lines the effect of capacitance can be neglected when the length of line is less than

  • 200 km
  • 160 km
  • 100 km
  • 80 km.

41. Use of high speed circuit breaker will actually increase the system stability.

  • False
  • True

42. Which one of the following device is used for improving the power factor of the system:

  • Synchronous Phase Modifier
  • Shunt Reactor
  • Series Reactor
  • Asynchronous Generator

43. When a line to ground fault occurs,the current in faulted phase is 100 A.The zero sequence current in this case will be

  • 0 A
  • 33.3 A
  • 66.6 A
  • 100 A

44. For the single phase 2-wire system, the maximum voltage between the outer wires and earth is ______________

  • V/√2
  • √2V
  • V
  • 2V

45. Which among the following quantities are specified at the generator bus?

  • P and Q
  • P and |V|
  • Q and |V|
  • P and δ

46. Which one of the following loads has the poorest power factor?

  • Electric fan Induction motor 
  • Transformer 
  • Induction motor
  • Induction furnace

47.  Phase advancers are used to improve the power factor of

  • Induction motors
  • Induction generators
  • Synchronous motors
  • Synchronous generators

48. At what value of ‘δ’ the maximum power transfer takes place

  • 90 degree
  • 0 degree
  • 45 degree
  • 30 degree

49. Which among these is related to the critical clearing timeof a fault in a power system?

  • Transient stability limit
  • Steady state stability limit
  • Frequency limit
  • All of these

50. The Critical Clearance time of a fault in the power system is related to

  • Reactive power limit
  • Short Circuit limit
  • Steady state stability limit
  • Transient stability limit

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