DECEMBER 2024
INTRODUCTION TO ELECTRIC GENERATION SYSTEMS
Time Allowed: 2.30 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) In a Nuclear Reactor Moderator is used to –
- a) reduce the speed of Neutrons
- b) increase the speed of Neutrons
- c) decrease the Number of Neutrons
- d) increase the number of Neutrons
Show Answer
Answer: a) reduce the speed of Neutrons
Explanation: A nuclear reactor moderator slows down fast neutrons to thermal energies. Slow neutrons are more effective in sustaining the nuclear fission chain reaction.
ii) Power output from Hydropower plant depends on –
- a) water Head
- b) discharge rate
- c) efficiency
- d) all of the above
Show Answer
Answer: d) all of the above
Explanation: Hydropower output depends on head, water discharge, and the efficiency of the turbine-generator system. Therefore, all of the listed factors affect the power output.
iii) Cochran boiler is of the type –
- a) Fire tube boiler
- b) water tube boiler
- c) Electric boiler
- d) None of these
Show Answer
Answer: a) Fire tube boiler
Explanation: A Cochran boiler is a vertical, multi-tubular, fire-tube boiler. Hot combustion gases flow through the tubes while water surrounds them.
iv) A Kaplan Turbine is –
- a) inward flow impulse turbine
- b) outward flow reaction turbine
- c) a high head mixed flow turbine
- d) low head axial flow turbine
Show Answer
Answer: d) low head axial flow turbine
Explanation: The Kaplan turbine is a reaction turbine designed for low-head, high-flow applications. Water flows axially through its runner, whose adjustable blades help maintain high efficiency over varying loads.
v) The term feed water means –
- a) The unpurified water obtained directly from a natural source
- b) The purified water for replacing losses from the feed system
- c) The water suitable for feeding to boiler for steam generation
- d) None of these
Show Answer
Answer: c) The water suitable for feeding to boiler for steam generation
Explanation: Feed water is the water supplied to a boiler for conversion into steam. It is normally treated and conditioned to reduce impurities, scaling, and corrosion.
vi) Load factor is always –
- a) unity
- b) Less than unity
- c) Greater than unity
- d) None of these
Show Answer
Answer: b) Less than unity
Explanation: Load factor is the ratio of average load to maximum demand. For a varying load, the average load is less than the maximum demand, so the load factor is less than unity.
vii) Which variety of coal Has lowest calorific value?
- a) Lignite
- b) Bituminous
- c) Peat
- d) Anthracite
Show Answer
Answer: c) Peat
Explanation: Peat is the least mature stage in coal formation and contains high moisture and relatively low fixed carbon. Consequently, it has the lowest calorific value among the listed choices.
viii) Economizer is used in power plants –
- a) To recover heat using bled steam from turbine
- b) To recover heat from the flue gas
- c) To cool down the exhaust steam
- d) None of these
Show Answer
Answer: b) To recover heat from the flue gas
Explanation: An economizer uses waste heat from the flue gases to preheat the boiler feed water. This reduces fuel consumption and improves the thermal efficiency of the plant.
ix) Pelton turbine is a –
- a) Tangential flow turbine
- b) Radial flow turbine
- c) Axial flow turbine
- d) Mixed flow turbine
Show Answer
Answer: a) Tangential flow turbine
Explanation: In a Pelton turbine, one or more high-velocity water jets strike the buckets tangentially. It is an impulse turbine generally used for high-head applications.
x) The yearly load duration curve of power plant is straight line. The maximum load is 400mw and minimum load is 350mw. Then find plant load factor is –
- a) 1.14
- b) 0.87
- c) 0.11
- d) 0.94
Show Answer
Answer: d) 0.94
Explanation: For a straight-line load duration curve, the average load is the mean of the maximum and minimum loads: (400 + 350)/2 = 375 MW. Plant load factor = 375/400 = 0.9375, approximately 0.94.
xi) The diesel plants are mainly used as –
- a) Peak load Plants
- b) Base load plants
- c) Stand by power plant
- d) Both peak and stand by plants
Show Answer
Answer: d) Both peak and stand by plants
Explanation: Diesel generating sets can be started quickly and are suitable for meeting peak loads and for standby or emergency supply. Their relatively high operating cost makes them less suitable for continuous base-load operation.
xii) If the half-life of a radioactive isotope is 2 seconds, its Decay constant is –
- a) 1
- b) 0.35
- c) 1.39
- d) 0.5
Show Answer
Answer: b) 0.35
Explanation: The decay constant is λ = ln(2)/T½. With a half-life of 2 seconds, λ = 0.693/2 = 0.3465 s⁻¹, which is approximately 0.35 s⁻¹.
xiii) The net change in internal energy in a steam power plant is –
- a) zero
- b) positive
- c) negative
- d) none of these
Show Answer
Answer: a) zero
Explanation: A steam power plant operates on a thermodynamic cycle, returning the working fluid to its initial state after one complete cycle. Since internal energy is a state function, the net change in internal energy over the complete cycle is zero.
xiv) A plant having maximum load of 100MW with plant capacity factor 50% and plant load factor of 60%, the plant utilization factor is –
- a) 83.33
- b) 16.33
- c) 66.33
- d) 100
Show Answer
Answer: a) 83.33
Explanation: Average load = 0.60 × 100 = 60 MW. Capacity factor = average load/plant capacity = 0.50, so plant capacity = 120 MW. Plant utilization factor = maximum demand/plant capacity × 100 = 100/120 × 100 = 83.33%.
xv) In thermal power plant the pressure in the working fluid cycle is developed by –
- a) condenser
- b) super heater
- c) feed water pump
- d) turbine
Show Answer
Answer: c) feed water pump
Explanation: The feed water pump raises the pressure of condensate or feed water to the boiler pressure. This pressure rise is an essential part of the Rankine cycle.
GROUP-B
2) Draw the schematic diagram of a simple coal fired thermal power plant. Briefly describe the functions of its main components. [4+4]
3) An 100 MW thermal power plant uses coal of calorific value 25 kJ/kg. If the overall efficiency of the plant is 40%, how much coal does it have to burn per second? Write the uses of ESP and Cooling tower. [4+2+2]
4) Draw a schematic diagram of a nuclear reactor. Describe the functions of control rod and moderator. [4+2+2]
5) Draw the schematic diagram of a closed cycle gas power plant. Write the advantages and disadvantages of gas power stations. [4+4]
6) Draw the schematic diagram of a Diesel power plant. Write its application areas. [5+3]
7) Describe the functions of the following components of hydroelectric power plant – i) Penstock ii) Surge tank iii) Spillway iv) Draft tube [2+2+2+2]
8) A Hydroelectric power station is working with a 100 m head and flow rate of 50m³/s. If the efficiency of the plant is 70%, what is its power output? Write down the names of different turbines used in hydroelectric power plants. [5+3]
9) A daily load curve of a power plant is shown in the figure below. Find i) Maximum demand ii) Units generated per day iii) Average load and iv) Load factor. [2+2+2+2]