March 2023
INTRODUCTION TO ELECTRIC GENERATION SYSTEMS
Time Allowed: 2.5 Hours Full Marks: 60
Answer to Question No. 1 of Group A is compulsory and to be answered first. This answer is to be made in separate loose script(s) provided for the purpose. Maximum time allowed is 30 minutes, after which the loose answer scripts will be collected and fresh answer scripts for answering the remaining part of the question will be provided. On early submission of answer scripts of Question No. 1, a student will get the remaining script earlier.
Answer any Five (05) Questions from Group B.
Group A
1. Choose the correct answer from the given alternatives (any twenty): 1×20
i. Economizer is used to heat
- Air
- Feed water
- Flue gases
- All above.
Show Answer
Answer: b) Feed water
Explanation: An economizer uses heat from the outgoing flue gases to preheat the feed water before it enters the boiler. This improves boiler efficiency by recovering waste heat.
ii. The function of the moderator in a nuclear power plant is to
- a) Stop chain reaction
- b) Absorb neutrons
- c) Reduce the speed of neutrons
- d) Reduce temperature.
Show Answer
Answer: c) Reduce the speed of neutrons
Explanation: A moderator slows down fast neutrons produced during fission to thermal-neutron energies. Slower neutrons are more effective in sustaining the chain reaction in thermal reactors.
iii. _____ takes water from valve house to turbine in hydroelectric power plants.
- a) Spillway
- b) Penstock
- c) Fore bay
- d) Tail race.
Show Answer
Answer: b) Penstock
Explanation: The penstock is the large pressure pipe that carries water from the valve house or forebay to the turbine. It delivers water at the required head and flow rate.
iv. For Flue gas flow, tick the correct sequence.
- a) Boiler-Air preheater – economizer- ID fan-Chimney
- b) Boiler-ID fan -Air preheater-Economizer-Chimney
- c) Boiler – Economizer- Air preheater- ID fan-Chimney
- d) None of the above.
Show Answer
Answer: a) Boiler-Air preheater – economizer- ID fan-Chimney
Explanation: Flue gases leave the boiler and pass through the air preheater and economizer, where their heat is recovered. The induced-draft fan then moves the gases toward the chimney.
v. Induced draft fans are used to
- a) Cool the steam let out by the turbine in thermal power station
- b) Cool the hot gases coming out of boiler
- c) Forces the air inside the coal furnace
- d) Pull the gases out of furnace.
Show Answer
Answer: d) Pull the gases out of furnace.
Explanation: An induced-draft fan creates a negative pressure in the furnace and draws the flue gases through the boiler and gas-cleaning equipment. It then discharges the gases toward the chimney.
vi. Function of Deaerator is
- a) Heat the water
- b) Heat the air in the water
- c) Remove dissolved gases in the water
- d) None of these.
Show Answer
Answer: c) Remove dissolved gases in the water
Explanation: A deaerator removes dissolved oxygen, carbon dioxide, and other non-condensable gases from boiler feed water. This reduces corrosion in the boiler and feed-water system.
vii. Load factor of a power station is defined as
- a) Maximum demand/average load
- b) Average load/connected load
- c) Average load/maximum demand
- d) connected load/Average load.
Show Answer
Answer: c) Average load/maximum demand
Explanation: Load factor is the ratio of average load to maximum demand over a specified period. A higher load factor indicates better utilization of the generating capacity.
viii. Steam turbine works on the principle of ___cycle.
- a) Carnot
- b) Brayton
- c) Rankine
- d) None of the above.
Show Answer
Answer: c) Rankine
Explanation: Conventional steam power plants operate on the Rankine cycle. The cycle includes pumping feed water, adding heat in the boiler, expansion through the turbine, and condensation.
ix. The function of a surge tank is
- a) To supply water at constant pressure
- b) To produce surges in the pipe line
- c) To relieve water hammer pressures in the penstock pipe
- d) To control water flow in turbine.
Show Answer
Answer: c) To relieve water hammer pressures in the penstock pipe
Explanation: A surge tank absorbs pressure fluctuations caused by sudden changes in water flow. It thereby reduces water-hammer effects in the penstock and protects the hydraulic system.
x. The thermal efficiency of a steam power station is
- a) 38%
- b) 28%
- c) 40%
- d) 45%
Show Answer
Answer: a) 38%
Explanation: A typical steam power station has a thermal efficiency of roughly 30–40% depending on operating conditions and plant design. Among the given alternatives, 38% is the appropriate value.
xi. The nuclear energy is measured in
- a) MW
- b) Farad
- c) Curie
- d) MeV.
Show Answer
Answer: d) MeV.
Explanation: Nuclear reaction energies are commonly expressed in electron volts, especially mega-electron volts (MeV), because nuclear energy changes are very large on the atomic scale. MW is a unit of power, Farad is a unit of capacitance, and Curie is a unit of radioactivity.
xii. Which of the following is base load power station? 1. Hydroelectric, 2. Diesel, 3. Thermal, 4. Pumped storage.
- a) Only 1,2,3.
- b) Only 4
- c) Only 1,3.
- d) Only 1,4.
Show Answer
Answer: c) Only 1,3.
Explanation: Hydroelectric and thermal stations can be used as base-load generating stations when operated for sustained demand. Diesel stations and pumped-storage stations are generally used for peak or load-following duties.
xiii. If maximum demand of a power plant is equal to the plant capacity, then
- a) Plant reserve capacity will be zero
- b) Diversity factor will be unity
- c) Load factor will be unity
- d) Load factor will be nearly 60%.
Show Answer
Answer: a) Plant reserve capacity will be zero
Explanation: Reserve capacity is the difference between plant capacity and maximum demand. If maximum demand equals plant capacity, this difference is zero.
xiv. The first nuclear power plant in India is built at
- a) Kota
- b) Kalapakkam
- c) Tarapur
- d) Bareilly.
Show Answer
Answer: c) Tarapur
Explanation: Tarapur Atomic Power Station in Maharashtra was the first commercial nuclear power station in India. Its first two units began commercial operation in 1969.
xv. Flat rate tariff is charged on the basis of
- a) Connected load
- b) Units consumed
- c) Maximum demand
- d) Both (a) and (b).
Show Answer
Answer: d) Both (a) and (b).
Explanation: A flat-rate tariff applies a fixed rate to the consumer based on a specified measure such as connected load or units of energy consumed. It does not use maximum demand as the principal basis.
xvi. The cheapest plant operation and maintenance is
- a) Thermal power plant
- b) Nuclear power plant
- c) Hydropower plant
- d) Diesel engine power plant.
Show Answer
Answer: c) Hydropower plant
Explanation: Hydropower plants have no fuel cost and generally require comparatively low operating and maintenance expenditure. Their main costs are associated with the initial construction and civil works.
xvii. The following element is a fissile material ________
- a) 238U
- b) 235U
- c) 232Th
- d) 240Pu.
Show Answer
Answer: b) 235U
Explanation: Uranium-235 is a fissile isotope that can sustain a nuclear chain reaction with slow neutrons. Uranium-238 and thorium-232 are fertile rather than readily fissile, while plutonium-240 is not the standard fissile isotope listed for this purpose.
xviii. Control rod of a nuclear power plant is made of
- a) Copper
- b) Graphite
- c) Boron
- d) Silicon.
Show Answer
Answer: c) Boron
Explanation: Boron is an effective neutron absorber and is therefore used in control rods, commonly in the form of boron compounds. By absorbing neutrons, the control rods regulate the reactor chain reaction.
xix. The value of demand factor is
- a) Less than one.
- b) Equal to one.
- c) Greater than one.
- d) Greater than two.
Show Answer
Answer: a) Less than one.
Explanation: Demand factor is maximum demand divided by connected load. Since maximum demand is normally less than or equal to connected load, the demand factor is generally less than one.
xx. The gas turbine power plant mainly uses which among the following fuels?
- a) Wood
- b) Natural gas and liquid petroleum fuel
- c) Coal and Peat
- d) Biogas
Show Answer
Answer: b) Natural gas and liquid petroleum fuel
Explanation: Gas turbine plants commonly use gaseous fuels such as natural gas and liquid fuels derived from petroleum. These fuels can be burned readily in the combustion chamber and are suitable for continuous turbine operation.
xxi. Francis and Kaplan turbines are used for _____ heads.
- a) High
- b) High and Medium.
- c) Low.
- d) Low and Medium
Show Answer
Answer: d) Low and Medium
Explanation: Francis turbines are generally used for medium heads, while Kaplan turbines are designed mainly for low heads with high flow rates. Therefore, together they cover low and medium head applications.
xxii. In an interconnected grid system, the diversity factor of the whole system
- a) increases
- b) decreases
- c) remains constant
- d) depends on the load
Show Answer
Answer: a) increases
Explanation: Interconnecting power systems combines loads whose individual peaks do not normally occur at exactly the same time. This increases the overall diversity factor and can reduce the required installed generating capacity.
xxiii. The area under the daily load curve gives
- a) average load
- b) maximum demand
- c) units generated
- d) connected load
Show Answer
Answer: c) units generated
Explanation: The area under a load-versus-time curve represents the integral of power with respect to time. Therefore, its value gives the electrical energy or units generated over the period.
xxiv. Fixed charge in tariff is
- a) Cost of investment irrespective of energy generated
- b) Operating cost of the fuel along with cost of investment plant
- c) Cost of fuel only.
- d) None of the above.
Show Answer
Answer: a) Cost of investment irrespective of energy generated
Explanation: Fixed charges are associated with capital investment and other costs that do not vary directly with the amount of electrical energy generated. They are payable even when energy consumption is low.
xxv. The most ideal tariff for the consumer is
- a) Two part tariff
- b) Three part tariff
- c) Both (a) and (b)
- d) None of the above.
Show Answer
Answer: a) Two part tariff
Explanation: A two-part tariff generally consists of a fixed charge and a charge based on energy consumed. It is comparatively simple and is commonly considered more suitable for consumers than a three-part tariff, which also includes a maximum-demand charge.
Group B
2. a) Write the points to be considered for selection of site of coal based Thermal Power Plants. b) Write the functions of Economiser and Electrostatic precipitator. (4+4)
3. a) Write the differences between fission and fusion reaction. b) What are the different types of nuclear reactors used in nuclear power plant? c) Briefly explain the main components of a nuclear reactor. (2.5+1.5+4)
4. a) Briefly explain the working of large hydro power plant with the help of a proper layout. b) What is the function of Pump storage plants? (6+2)
5. a) Write the merits and demerits of Hydro Electric Power Plants. b) A Hydro station has a mean head of 50 m and is supplied from a reservoir at a rate of 10 m³ per second. Calculate the power generated in kW if the efficiency of the power plant is 80%. Assume the density of water 1000 kg/m³. (4+4)
6. a) Write the merits and demerits of Diesel Electric Power Plant. b) Explain the working of Gas turbine power plant with the help of block diagram. (3+5)
7. a) Define the following terms, i) Demand factor, ii) Load factor, iii) Diversity Factor. b) The load on a power plant on a typical day is as follows: Time: 12AM-6 AM, 6AM-9AM, 9AM-6PM, 5PM – 10PM, 10PM – 12AM; Load (MW): 25, 50, 90, 120, 25. Plot the load curve and load duration curve of the power plant. Also find the load factor of the power plant. (3+5)
8. a) What information are conveyed by a load curve? b) Write a short Note on Integrated Load Duration Curve. (4+4)
9. a) What are the advantages of interconnected power system? b) Briefly explain two-part tariff. (4+4)