JANUARY 2026
INTRODUCTION TO ELECTRIC GENERATION SYSTEMS
Time Allowed: 2.5 Hours Full Marks: 60
Answer to Question No. 1 of Group A must be written in the main answer script. In Question No. 1, out of 2 marks for each MCQ, 1 mark is allotted for right answer and 1 mark is allotted for correct explanation of the answer. Answer any Five (05) Questions from Group-B.
GROUP-A
1. Choose the correct answer from the given alternatives and explain your answer (any ten): [2×10=20]
i. What is the main function of a coal-based thermal power plant?
- a) To convert solar energy into electrical energy
- b) To convert chemical energy of coal into electrical energy
- c) To store electrical energy
- d) To distribute electrical energy
Show Answer
Answer: b) To convert chemical energy of coal into electrical energy
Explanation: A coal-based thermal power plant burns coal to release its stored chemical energy as heat. This heat converts water into steam, which drives a turbine coupled to a generator, producing electrical energy. So the overall function of the plant is to convert the chemical energy locked in coal into electrical energy.
ii. What is the purpose of the condenser in a thermal power plant?
- a) To superheat the steam
- b) To convert exhaust steam into water
- c) To supply fuel
- d) To generate electricity
Show Answer
Answer: b) To convert exhaust steam into water
Explanation: The condenser condenses the low-pressure exhaust steam coming out of the turbine back into water by removing its latent heat using cooling water. This maintains a vacuum at the turbine exhaust, which improves turbine efficiency, and the condensed water is recycled back to the boiler as feed water.
iii. Which cycle is used in coal-fired thermal power plants for energy conversion?
- a) Diesel cycle
- b) Otto cycle
- c) Modified Rankine cycle
- d) Brayton cycle
Show Answer
Answer: c) Modified Rankine cycle
Explanation: Coal-fired thermal power plants operate on a modified Rankine cycle, where steam is generated at high pressure and temperature, expanded through a turbine to do work, condensed, and then pumped back to the boiler. Reheating and regenerative feed heating are added to the basic Rankine cycle to improve efficiency, hence the term ‘modified’.
iv. In a steam turbine, the type of steam applied is:
- a) Wet steam
- b) Dry steam
- c) Superheated steam
- d) any of the above
Show Answer
Answer: c) Superheated steam
Explanation: Steam turbines are supplied with superheated steam rather than wet or dry saturated steam because superheated steam carries more energy and, more importantly, avoids excessive moisture content in the later turbine stages, which would otherwise cause erosion of the turbine blades.
v. Which type of coal is most commonly used in thermal power plants?
- a) Lignite
- b) Anthracite
- c) Peat
- d) Bituminous
Show Answer
Answer: d) Bituminous
Explanation: Bituminous coal is the most commonly used coal in thermal power plants because it has a good balance of calorific value, moisture content, and ash content, making it efficient and economical for large-scale steam generation compared to lignite, anthracite, or peat.
vi. What is the primary fuel used in a nuclear power plant?
- a) Coal
- b) Uranium-235
- c) Natural gas
- d) Boron
Show Answer
Answer: b) Uranium-235
Explanation: Uranium-235 is the primary fissile fuel used in most nuclear power plants. Its nucleus readily splits when struck by a neutron, releasing a large amount of energy along with more neutrons that sustain the chain reaction used to generate heat.
vii. What is the role of the moderator in a nuclear reactor?
- a) To speed up neutrons
- b) To absorb radiation
- c) To slow down neutrons
- d) To cool the reactor
Show Answer
Answer: c) To slow down neutrons
Explanation: Fast neutrons released during fission are not efficient at causing further fission in Uranium-235. The moderator (such as water, heavy water, or graphite) slows down these fast neutrons to thermal speeds, increasing the probability that they will cause further fission and sustain the chain reaction.
viii. What is the function of a nuclear reactor in nuclear power plant if compared to a conventional steam power plant?
- a) Boiler
- b) Electric generator
- c) Turbine
- d) Furnace
Show Answer
Answer: a) Boiler
Explanation: In a nuclear power plant, the reactor performs the same basic role as the boiler in a conventional steam power plant, that is, it generates the heat needed to convert water into steam. Instead of burning fuel like coal, the reactor uses controlled nuclear fission to produce this heat.
ix. In a thermal power plant, flue gas sequentially flows through the path of:
- a) Boiler – Economiser – Superheater – Air preheater
- b) Boiler – Superheater – Air preheater – Economiser
- c) Boiler – Air preheater – Superheater – Economiser
- d) Boiler – Superheater – Economiser – Air preheater
Show Answer
Answer: d) Boiler – Superheater – Economiser – Air preheater
Explanation: Flue gas leaves the furnace at the highest temperature and passes first through the superheater, transferring heat to the steam. It then passes through the economiser, preheating the boiler feed water, and finally through the air preheater, which heats the incoming combustion air before the cooled flue gas exits through the chimney.
x. Diesel power plants are best suited for:
- a) Base load
- b) Peak load
- c) Stand-by power plants
- d) Both b) and c)
Show Answer
Answer: d) Both b) and c)
Explanation: Diesel power plants have a high running cost due to expensive fuel but can start up very quickly. This makes them unsuitable for continuous base load operation but well suited for meeting short-duration peak loads and for use as stand-by or emergency power sources.
xi. What is the function of the compressor in a gas turbine power plant?
- a) To increase fuel pressure
- b) To compress air before combustion
- c) To compress exhaust gases
- d) To reduce emissions
Show Answer
Answer: b) To compress air before combustion
Explanation: In a gas turbine power plant, the compressor draws in atmospheric air and compresses it to a high pressure before it enters the combustion chamber. This compressed air is essential for efficient and complete combustion of the fuel.
xii. What is the main advantage of a gas turbine power plant?
- a) High maintenance
- b) Large startup time
- c) Fast startup and compact size
- d) Low power-to-weight ratio
Show Answer
Answer: c) Fast startup and compact size
Explanation: Gas turbine power plants can be started up and brought to full load much faster than steam power plants, and their equipment occupies comparatively less space. This makes them ideal for peak load duty and locations with limited space.
xiii. What is the role of a surge tank in a hydro-electric plant?
- a) To generate electricity
- b) To regulate water pressure variations
- c) To store fuel
- d) To remove silt from water
Show Answer
Answer: b) To regulate water pressure variations
Explanation: A surge tank is installed close to the turbine in a hydro-electric plant to absorb the sudden rise or fall in water pressure caused by rapid changes in turbine load, protecting the penstock from water hammer effects and stabilising the flow of water to the turbine.
xiv. The efficiency of a modern hydel power plant is approximately:
- a) 25–30%
- b) 35–40%
- c) 60–70%
- d) 85–90%
Show Answer
Answer: c) 60–70%
Explanation: Modern hydroelectric power plants are highly efficient because the conversion of potential energy of water into electrical energy involves relatively few losses. Overall plant efficiency, considering hydraulic, mechanical, and electrical losses together, typically falls in the range of about 60 to 70 percent.
xv. Load factor of a power plant having average demand of 40 MW and maximum demand of 60 MW is:
- a) 66.67 %
- b) 150 %
- c) 40 %
- d) 60 %
Show Answer
Answer: a) 66.67 %
Explanation: Load factor is defined as the ratio of average demand to maximum demand. Here, Load factor = (Average demand / Maximum demand) x 100 = (40 / 60) x 100 = 66.67%.
GROUP-B
Answer any Five (05) questions.
2. (a) Draw the overall block diagram of a coal-based thermal power plant.
3. Explain the features and functions of the following equipments associated with a nuclear reactor: (i) Coolant (ii) Moderator (iii) Control rod and (iv) Reflector. [2+2+2+2]
4. Draw a neat labelled block diagram of a diesel power plant and discuss the advantages and disadvantages of it. [4+2+2]
5. Draw a neat labelled block diagram of a gas turbine power plant and state its advantages, disadvantages and applications. What is the function of a regenerator in a gas turbine power plant? [4+3+1]
6. (a) Define: (i) Demand factor, (ii) Diversity factor, (iii) Load factor and (iv) Base load.
(b) Discuss the importance of a load curve. [4+4]
7. (a) State the differences between nuclear fission and nuclear fusion.
(b) Discuss the merits and demerits of a hydroelectric power plant.
(c) Write down the function of a spillway. [2+4+2]
8. Write short notes on (any two): (i) ESP, (ii) Brownout and Blackout, (iii) Pumped storage hydro power plant and (iv) CANDU reactor. [4+4]
9. (a) Write down and explain each term of hydro-power (in kW) generation equation.
(b) It has been estimated that a minimum run-off of approximately 94 m³/s will be available at a hydro-electric power project with a head of 39 m. Determine: (i) Firm capacity (ii) Yearly gross output of the plant. Assume the overall efficiency of the plant to be of 80%. [2+3+3]
10. (a) Why pulverization of coal is done in thermal power plants?
(b) A 100 MW steam station uses coal of calorific value 6400 kcal/kg. Thermal efficiency of the station is 30% and electrical efficiency is 92%. Calculate the coal consumption per hour when the station is delivering its full rated output. [2+6]