50+ Power plant interview questions and answers

1. What is a power plant?

The power plant is also called as a power station, it is a place where power is generated and transmitted. It does the production of electrical energy and then the electric power is distributed. So power plant can be considered as a network which consists of power generation, distribution, and transmission.

2. What are the types of power plants?

• Steam power plant

• Hydroelectric power plant

• Diesel power plant

• Nuclear power plant

• Gas turbine power plant

• MHD power plant

3. What is the slack bus?

This is responsible for delivering losses in the power system, in this bus the voltage and phase angle magnitude is specified. This bus will respond quickly to a load change condition.

4. What are the factors that can determine the performance of a power system?

Certain factors must be considered to determine the power plant performance they are

• Heat rate

• Capacity factor

• Economic efficiency

• Load factor

• Operational efficiency

5. What is the conventional and non-conventional power plant?

Conventional power plant

• Hydropower plant

• Steam power plant

• Nuclear power plant

• Gas turbine power plant

Non-conventional power plant

• Tidal power plant

• Wind power plant

• Geothermal power plant

• Solar power plant

• Wave power plant

• MHD generation

6. What are the circuits that can be seen in the steam power plant?

• Air and flu gas circuit

• Coal and ash circuit

• Feed-water and steam circuit

• Cooling water circuit

7. Explain the critical disruptive voltage?

It is the minimum voltage at which the breakdown of insulation properties of air takes place and at this time the corona will begin

8. What are the kind of faults that can be seen in a three-phase power system?

• LG fault or a single line to ground fault

• Line to line fault LL

• Three-phase short circuit fault

• Three-phase to ground fault

9. In the future which power plant will be used more?

The use of electric power is increased, and it must be supplied without any interruption. Our natural resources such as oil, gas, and coal are depleting. So we need to use other sources of energy, and most of them are not able to supply a huge amount of power such as nuclear plants, so this can be considered as the future power plant.

10. What is a nuclear power plant?

This power plant can create a huge amount of power and it uses a nuclear reactor to generate power, so it is a thermal power generation. The heat source in this plant is the thermal reactor

11. Which relay scheme is used for transmission line protection?

Impedance relay

12. For long-distance transmission lines which type of relay is used?

Mho relay

13. How long can a nuclear fuel last in a nuclear power plant?

A large amount of energy can be produced by using nuclear fuel, so it would last very long. It could last for 4-5 years.

14. Explain hybrid substation?

It is the combination of air-insulated substation and gas-insulated substation.

15. What are the different types of bus-bar arrangement scheme in a substation?

• Single bus scheme

• Double bus single breaker scheme

• Main and transfer bus bar scheme

• Double bus single breaker scheme

• Breaker and half scheme

• Ring main bus scheme

16. In a distribution network which type of switching scheme is suitable and why?

Ring main bus bar scheme can be used because it has an advantage that if the interruption of power takes place in a bus section then, the power can be fed the bus from the other side of the power system.

17. Explain the electrical clearances done in a substation?

Ground clearance – it is the clearance between any live conductor and earth

Phase clearance – clearance is needed between different phases in a circuit or the same phases in different circuits.

Sectional clearance – this is the minimum clearance that is required between the live conductor and limits of work. So this clearance will be useful for the operating person’s safety. The limits of the work section could be ground or the platform in which the person is working.

18. What are the types of current transformers that are used in a substation?

Current transformers are used in a substation to decrease the alternating current from higher value to lower value, for the measuring and control purpose. Two types of current transformers are used they are

Measuring current transformers

These transformers are used for measuring purpose, it is used with an ammeter, wattmeter, and KVA meter.

Protective current transformers

These transformers are used for overcurrent protection, earth fault protection, differential, and impedance protection.

19. Explain the basic impulse level?

It is the peak value of lightning impulse voltage, withstand capability of the equipment

20. What are the disadvantages of corona?

It causes power loss and noise and they also cause radio interference

21. What are the different types of conductors?

• Solid conductors

• Stranded conductors

• Composite stranded conductors

• Bundle conductors

22. Explain bundle conductors?

Bundle conductors are created by using two or more sub-conductors, these conductors are used as one phase conductors. These conductors have certain advantages and they are, it can reduce reactance and voltage gradient, it can also reduce corona loss and interference.

23. Why do we need double circuit lines?

Double circuit lines are used to improve the power handling capability, it has certain advantages like half of the load is shared by another line, it can handle the load current increase, if there is a power failure in one circuit then the power will be supplied by other lines.

24. Why intercooler is used in a gas turbine power plant?

In the isothermal process, the power used to compress the air is very less, so the temperature of air constant is required to be maintained. The intercooler will cool the air leaving the L.P compressor and then it is sent to the H.P compressor.

25. What are the required elements in a hydro-power plant?

Catchment area, reservation, dam, surge tanks, draft tubes, powerhouse

26. Explain the mini and micropower plants?

The mini –power plants can produce about 1MW to 5MW of power and they operate with 5m-20m head. While the micropower plant needs ahead less than 5m and it will produce power about 0.1MW to 1MW

27. What kind of energy conversion takes place in a thermal power plant?

In a thermal power plant, the chemical energy is converted to mechanical energy, and then it is converted to electrical energy.

28. Why the reheat cycle is used in the steam power plant?

It is used to increase the thermal efficiency

29. Explain tine graded protection?

This is the overcurrent protection, in this protection the time setting of the relay is graded in a way that in case of a fault, during the fault the smallest part of the system will be disconnected.

30. What are the elements of current carrier protection?

The elements of current carrier protection are the transmitter, receiver, coupling equipment, and line trap.

31. What are the main circuits in the thermal power plant?

• Feed water and steam flow circuit

• Coal and ash circuit

• Air and gas circuit

• Cooling water circuit

32. Explain the thermal efficiency of the steam power plant?

The thermal efficiency of a steam power plant can be described as the ratio of heat equivalent of mechanical energy transmitted to the turbine shaft to the heat of combustion

33. What is the function of a moderator in a nuclear power plant?

The major function of the moderator is to absorb the heat energy caused by nuclear reaction

34. Why oxygen is not used as a moderator in a nuclear power plant?

It is not used as a moderator because of its low density and also because of the consequent small number of collisions.

35. Why thermal reactor control is very easy than the other reactor?

The thermal reactor control is very easy because of the low power density and longer neutron lifetime.

36. Why the leakage or component failure in a primary nuclear fission reactor coolant is dangerous?

It is very dangerous because it is very difficult to repair these faults and also because of the presence of fission products in the coolant which can cause contamination.

37. What kind of turbines are used in modern steam turbines?

Impulse reaction turbines

38. What is the use of track rash?

This device is used to reduce or prevent the entry of debris, if this is not done then it would badly affect the turbine.

39. What is a forebay and why is it used?

This is for temporary water storage, in case the load on the plant is decreased and it also gives water for the initial increment for the increasing load.

40. Explain prime movers and why is it used?

This is used to convert the kinetic energy of water into mechanical energy so that the electrical energy can be produced. Prime movers have been used in hydraulic power plants some examples for prime movers are Kaplan turbine and Pelton wheel.

41. Explain the draft tube?

The draft tube is used, in order to regain the kinetic energy of water which comes from the reaction turbine.

42. List out some high-pressure boilers?

• Benson boiler

• Loffler boiler

• Velox boiler

43. Why high-pressure boiler is used in power plants and what is its purpose?

Power plant efficiency can be increased by using high-pressure boilers, and they can reduce the cost of electricity production.

44. What is the overall efficiency of the nuclear power plant?

The overall efficiency of the nuclear power plant is in the range of 30-40%. Their efficiency will be high at high road factors.

45. Why the operating cost of the nuclear power plant is less than the thermal power plant?

The major cost of the nuclear power plant is the fuel and it is considered as the capital cost. While in the thermal plant the cost of handling and transporting the coal is very high, when compared to the nuclear power plant.

46. Which nuclear reaction is performed in a nuclear power station?

Nuclear fission is the reaction that takes place in a nuclear power station, in this reaction heavy nucleus is bombarded by certain particles and the heavy nucleus will split and because of this a huge amount of energy will be released during this process.

47. Why neutron is bombarded on the heavy nucleus of nuclear fuel?

Neutron is bombarded and neutrons are chosen for this process because they are neutral in charge and because of that, they are able to make way through the shells of electrons and then through the nucleus at low energy.

48. Which fuel is used for nuclear fission reactors?


49. Why the reheat cycle is done in the steam power plant?

It is done to increase the thermal efficiency

50. Why mercury is used with steam in the binary vapor cycle?

Because mercury has, high critical temperature and pressure. It also has a higher saturation temperature than other fluids and they have relatively low vaporization pressure

51. Why protection is not provided for the turn to turn fault in an alternator?

Nowadays the alternators are of single turn so it is not necessary to provide protection for the turn to turn faults

52. Explain the negative phase sequence relay and where is it used?

These relays are used for the protection of generators and motors, in case of unbalanced loading, which could happen because of phase to phase faults.

53. What is the purpose of the differential relay?

A differential relay would operate if the phasor difference of two or more similar electrical quantities exceeds a predetermined amount.