# Power Systems MCQ Electrical Engineering

50 Questions 30 Mins

### 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

• 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

• 1 Ω
• 0.5 Ω
• 2 Ω
• 5 Ω

### 6. 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

• 1965
• 1954
• 1990
• 1985

### 8.  If the load current decreases then the power factor

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

### 9. Power factor of a load can be improved by using

• Static capacitors
• Synchronous condenser
• All of the above

### 10. 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.

### 11. 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

### 12. 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

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

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

### 14. 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

• 5 %
• 30 %
• 25 %
• 15 %

### 16. A _________ distribution system is more reliable than the ______ distribution system.

• parallel, ring
• ring, parallel

### 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)

• 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 short circuit current of an alternator when short circuited on three phases will be

• Zero as time goes to infinity
• Maximum when time goes to infinity
• Infinity when time goes to infinity
• Small as time goes to infinity but not zero

### 23. 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

### 24. 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

### 25. 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

### 26. Which one of the following statements is NOT true?

• When the equipment is designed at low power factor it is to be designed for more kVA
• When power factor is decreased, loss in the cable supplying load is decreased.
• Due to reduced power factor voltage regulation of line becomes poor
• Reduced power factor reduces the efficiency of the plant

### 27. 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

### 28. 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

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

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

• Generation
• Distribution
• Transmission
• Grid

### 31. 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

• Kota
• Sarni
• Chandrapur
• Neyveli

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

• current capacity
• voltage drop
• operating voltage
• all of the mentioned

• Uneven land
• Sun
• Vegetation
• Seasons

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

• Temperature
• Photons
• Diode current
• Shunt current

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

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

### 37. 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

### 38. 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.

### 39. Skin effect is proportional to

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

### 40. 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

• Mechanical
• Solar
• Electrical
• Heat

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

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

• 155.6 V
• 311.12 V
• 622 V
• 220 V

• 200 km
• 160 km
• 100 km
• 80 km.

• False
• True

### 46. 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

• 0 A
• 33.3 A
• 66.6 A
• 100 A

• V/√2
• √2V
• V
• 2V

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

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

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