Electrical Interview

Important Electrical viva Questions

What is RMS and how much is its value?

RMS stands for Root Mean Square, the amount of heat generated by a certain amount of direct current (DC) flowing in a circuit over a period of time requires the same amount of alternating current (AC) to flow in that electrical circuit. This is called the RMS value of the alternating current. The value of RMS is assumed to be 0.70 7 max. It is noted that you will get so many electrical engineering viva questions these will be very helpful for your government and non-government job interview. You can read these electrical viva questions to increase your skill.

What causes the transformer to overheat? And what is the function of transformer oil?

Transformers can be hot for a variety of reasons, but there are four main reasons why they can be hot

  • To be overloaded
  • When the insulation is weak
  • Somewhere at earth
  • For overvoltage supply

 The main function of transformer oil is to provide insulation between the primary and secondary windings of the transformer.

What does mean by cable RM, SM, SE, RE?

In many cases, the cable has RM, SM, and RE written on it, which basically means the unit of the cable.

  • RMS means that many of them have a cross-section whose cross-section is round.
  • SM means many of them whose cross-section is sector-shaped
  • RE means single solid wire whose cross-section is round.

What is MCB?

MCB stands for Miniature Circuit Breaker, MCB Circuit breakers that are small in size and used for much less current are called miniature circuit breakers. The reasons why we use MCB circuit breakers are mentioned below

  • For overload protection first
  • For short circuit protection
  • For on and off switch.

When the circuit breaker trips?

 Miniature circuit breakers usually trip in three ways.

  • When 3 to 5 times more current flows,
  • 5 to 10 times more current flows,
  • 10 to 20 times more current flows.

What is Phase and Phase angle?

The face is the angular position of a variable at any given time. The phase angle is the angle between the voltage and current of the AC circuit.

What is Relay?

The relay is a type of electromagnetic device or electromagnetic device that has a coil where a temporary electromagnet is generated as soon as the power is supplied and can turn the switch on and off so some important parts of the Relay such as

  • Normally open
  • Normally close
  • Common
  • Coil

What is Resistance?

 When current flows through a conductive substance, it is interrupted due to the properties or properties of the conductive material. This property is called resistance. Its symbol is R and the unit ohm of resistance

What is Voltage?

 The force or pressure required to displace the free electrons of the atoms of a conductive substance is called the electric force or voltage. The voltage K is expressed by v as the unit volt.

 What is Current?

 The rate at which electrons in a conductive material flow in a certain direction is called current. It is expressed by I as its single Ampere.

What do you mean by Modbus communication?

Modbus is the data communication protocol that was developed by the Modicon Company in 1979. Basically, the Modbus communication protocol is used for transmitting data or information between electrical or electronic devices. Basically, PLC, HMI, PC, and some other electrical or electronic devices are used for Modbus and RS-485, or RS-232 communication protocol is used that communicates by transmitting with ASCII characters

Which cable is used for Modbus communication system?

A shielded and twisted pair cable is used for the Modbus communication system. It is because CAT5 or CAR6 twisted-pair cable provides a good economical solution for field wiring, and the data transfer ratio is very high. For this reason, a shielded and twisted pair cable is used for the Modbus communication system.

What is the load curve and maximum demand?

If the curve shows the load variation of the power station with respect to time which is called load curve. The load of the power system is not constant it varies from time to time. Basically, load variation occurs during 24 hours and the load curve shows the result during different hours (hourly, half-hourly, and plotted against time) on the graph.

Maximum demand is the greatest demand of load within a day or 24 hours in the power station. We know that power system load is varied from time to time. Basically, the maximum demand is a higher load than the rated load. It can be very high than the rated load, such as 6 MW, or more, and load demand becomes very high at 6 PM which is called peak load.

Demand factor, load factor, diversity factor, and average load.

The demand factor is the maximum demand of the power station to its connected load. The demand factor value is usually less than 1. The maximum demand is indeed less than the connected load. If the maximum demand is 80 MW, and the connected load is 100 MW then the demand factor will be 80/100 = 0.8.

Demand factor = Maximum demand /Connected load

Demand factor = 80/100 = 0.8

Load factor

The ratio of average load to the maximum demand during a given period is called the load factor. The load factor is always less than 1 because the average load is lower than the maximum demand.

The load factor = Average load/maximum demand

If the power plant is operated for 24 hours (Time), then load factor = Average load * T/max. Demand * T

The unit generated in 24 hours (T)/maximum demand * 24 hours (T)

Diversity factor

The ratio of the sum of the individual maximum demand to the maximum demand on the power station is called the diversity factor. It is noted that the diversity factor will be more than 1, if the diversity factor increase then electricity generation cost is reduced.

Diversity factor = Sum of individual maximum demand/maximum demand of power station

Average load

If the average load occurs in the electrical power station in a certain period (day, month, and year) which is called average load or average demand.

The daily average load = number of units (KWh) generated in a day/24 hours.

The monthly average load = number of units (KWh) generated in a month/number of the hour in a month (one month = 720 hours).

The yearly average load = number of units (KWh) generated in a year/8760 hours (1 year = 8760 hours).

 What are the types of load in the power system?

If any electrical or electronic device taps the electrical energy from the electrical power system which is called load in a power system. Basically, the load can be resistive, capacitive, and inductive. If we think without the above load then will get some other load on the power system, such as

  1. Domestic load
  2. Irrigation load.
  3. Municipal load.
  4. Industrial load
  5. Commercial load
  6. Electric traction load

What do you mean by the base load and peak load?

There are different types of load in the power system and these loads vary from time to time. The power system load curve shows that load curve. In this stage, we get two main loads

  1. Base load. Base load is the main load that occurs almost whole the day in the power plants. It means that 50 MW electrical powers are supplied to meet the load demand and no extra load available for a certain time which is called base load.
  2. Peak load. Peak load means that load demand is higher than the rated load. Suppose, 50 MW is supplied as the base load but suddenly 10 MW load demand is increased then the increased load will be considered as peak load. Basically, peak load occurs at 5 PM.

What are the advantages of an interconnected grid system?

If the connection of the several electrical generating stations in parallel which is called an interconnected grid system. There are some advantages of the international grid system. These are given below.

  1. Exchange of peak load. When peak load occurs in the power system then the peak load can be exchanged by the interconnected grid system. If the load curve shows that load demand has been increased than the rated load. In this case, the excess load can be shared by another power station.
  2. Use of older power plants. If any older power plant is not able to meet the load demand or is inadequate to meet the desired load demand then another power plant can be used to meet the load by the interconnected grid system.
  3. Interconnected grid systems increase diversity factors. The load curve becomes different on the different interconnected power stations. In this case, the individual maximum load demand becomes lesser than the maximum load demand, and the diversity factor is increased which is very essential to reduce electricity generation costs.
  4. Interconnected grid systems make sure economical operation.
  5. Grid system reduced plant reserve capacity.

What are the types of electrical energy cost?

The total cost of generation of electrical energy is divided into three parts

  1. Fixed cost. It is the cost which is dependent on maximum demand and unit generated. Fixed cost is included in the interest on the capital cost of land and salaries of a high official.   
  2. Semi-fixed cost. Semi-fixed cost depends on the maximum demand but semi-fixed is independent of the unit generated.
  3. Running cost or operating cost. Running cost is depends on the number of units generated. The annual cost of fuel, maintenance cost, salaries, and wages are included in the running cost.

Why damper is used in the transmission line?

The damper is designed to spread the oscillating force of the main wire to an acceptable level. Its distinctive shape gives it the nickname dog-sister damper. These dampers are used to prevent vibrations excited by the wind, the so-called Karman vibration. Basically, the damper is used in the very high voltage (132KV, 230KV, 400 KV, and so on) transmission line.

Types of Power in Electrical Power System

Basically, There are three types of power in electrical power system, such as

Apparent power: Apparent power is the ideal power and apparent power is the total power of a circuit. There are two types of apparent power, such as active power and reactive power. Apparent power is expressed in KVA.

Active power: Active power is the power which consumed in an AC circuit. It is also called real power and expressed in KW.

Reactive power: Reactive continuously flows from source to load and it is expressed in KVAR. Reactive power is responsible for the low lagging power factor.

Some Important electrical engineering viva questions and answers in Bangladesh

1. Total generation capacity of Bangladesh: 25000 MW

2. Daily Total Generation capacity: 10,000-12,000 MW

3. Highest generation so far: 12,793 MW

4. Total power plants in Bangladesh: 138 power plants

5. Total Distribution Loss: 9.35%

6. Total Transmission Loss: 2.75%

7. Largest Power Plant: Ashuganj power plant

8. Capacity of Barapukuria Coal Power Plant: 525 MW (it is a coal power plant).

9. Which is the fuel of Ruppur nuclear power plant: Uranium-235 (two sections 1200 + 1200) total generation capacity is 2400 MW.

10. Ruppur Nuclear Power Plant Fuel Supplier: Russia (Rosatom company)

11. How many years will the Ruppur nuclear power plant run on fuel once: Almost 60 years

12. Where will the 2nd nuclear power plant be: Hijla, Barisal

13. What is CCPP? – Combined cycle power plant

14. Electricity is produced at the lowest cost of any fuel: natural gas. 2.8 taka

15. How much electricity is brought from India: 1160 MW

16. What is the electricity demand of the country in winter: 50-60% of the total demand.

17. Which region produces the most electricity: Sylhet

18. Which region has the lowest power generation: Rangpur

19. What grade of coal is used in coal power plants: Bituminous / sub-bituminous

20. Number of distribution companies: 6

21. Are REB and PBS the same? No Rural Electrification Board (REB) and Polli Biddut Songostha (PBS) is not same.

22. How many PBS: 80



25. With which fuel is most power generated? – Natural gas (83%)

26. Bangladesh will be 100% electrified: in 2025

27. Per capita power generation: 510 kWh

28. Hydropower plants and capacity: 1, 230 MW

29. How many 400 levy lines are there?

30. Where is the 65 kV line going?

31. Capacity of Rampal Coal Power Plant: 1320 MW

32. Capacity of Matarbari Coal Power Plant: 1200 MW

33. Capacity of Payra Thermal Power Station: 1320 MW

34. Capacity of Ruppur Nuclear Power Plant: 2 * 1200 = 2400 MW

35. The first unit will go into production: 2023

36. The second unit will go into production: 2024

37. Target of power generation from windmills by 2021: 1360 MW

38. Power generation from renewable sources: 628 MW

39. Power generation target from a renewable source: 10% of total capacity.

40. Power generation from Quick Rental: 1890 MW

41. Population with access to electricity: 98%

42. Total transmission line: 12,119 circuit km

43. Distribution line: 5 lakhs 60 thousand km

44. Number of subscribers: 3 crores 84 lakhs

45. Frequency of electricity in Bangladesh: 50 Hz

46. ​​Peak Load Power Plant Key: Plants run to meet the demand for electricity during peak hours.

47. Off-peak and on-peak power demand: 7000 / 11000MW

48. Where is the first waste power plant of the country: Jalkuri, Nahganj (3 MW)

49. 1st HVDC substation: Bheramara, Kushtia

50. 2nd HVDC substation: Devpur, Comilla

51. Longest Transmission Line: KHULNA-VERAMARA (353CKT KM)

52. High Generation, Low Demand Area: Sylhet

53. Low Generation, High Demand Area: Rangpur

54. Means of communication from the substation to substation: SCADA + PLCC



57. NLDC: National Load Dispatch Center

58. Grid usable power generation capacity: 16,000 MW

59. Number of interconnected grids: 1

60. Generation target in 2022: 24,000 MW

61. Generation target for 2030: 40,000 MW

62. Generation target in 2040: 60,000 MW

63. Where will the LNG terminal be: Maheshkhali

64. Power Hub: Maheshkhali, Ashuganj, Payra, Bheramara, Matarbari

65. What is the voltage of the line passing over the river Jamuna – 230 kV

66. Price of electricity imported from India: 5.34 taka

67. Next countries from which electricity will be imported: Nepal, Bhutan

68. Does Picking Power Plant Run 24 Hours: No, Running in Peak Time

69. Most power plants in any zone: Dhaka zone, 39

70. The lowest power plant in any zone: Rangpur, Mymensingh, 6

71. Largest Solar Power Plant: 26 MW, Hinla, Teknaf

72. First Isolated Grid: Hatia, Noakhali

73. The first windmill of the country: Sonagazi, Feni

74. 2nd windmill of the country: Kutubdia, Cox’s Bazar

75. How many volt DC batteries are used in substation: 110 VDC

76. Upcoming Hydropower Project: Sangu River (140 MW), Matamuhuri River (75 MW)

77. Per unit solar cost: 16.14 taka

78. Coal cost per unit: 7.38 taka

79. Per unit gas cost: 2.8 taka

80. Per unit Furnace Well Cost: 11.48 taka

81. Per unit hydropower cost: 1.32 taka

82. Coal is imported mainly from Indonesia, Australia

83. The first gas insulated substation in the country: Dhanmondi

84. Where the wave trap is used: PLCC

85. Highest Generating Voltage of Bangladesh: 22.05 KV (Ashuganj)

86. 1 MW coal power plant takes 24 hours to run coal: 10 tons




90. Peak Hour: 5 pm to 11 pm

Peak Hour: 5 pm to 11 pm

91. Off-Peak Hour: 11 pm to 5 pm

92. Conductor used in transmission line: ACCC / ACSR

93. A 400 KV line requires 21 disk insulators

94. Grid Ring: 2, Dhaka, Chittagong

95. Upcoming Largest Switching Substation: Gopalganj

96. Brownout key: If the voltage is down even after the power is OK

97. How many wires are there in the distribution line: 3 or 4 (three phase three wire or three phase four wire).

98. PGCB: Power Grid Company of Bangladesh

99. PGCB Sells Optic Fiber Bandwidth to Telecom Sector with GP

100. Commercial Name of Transformer Oil: Pyranol

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