POWER SYSTEMS MCQS SET 20

POWER SYSTEMS MCQS SET 20

1․ A power station has a maximum demand of 15000 kW. The annual load factor is 50% and plant capacity factor is 40%. What is the reserve capacity of the plant?
a. 7500 kW         b. 3750 kW          c. 6000 kW            d. 3000 kW
ANSWER: b
 
2․ The daily energy produced in thermal power station is 720 MWh at a load factor of 0.6. What is the maximum demand of the station?
a. 50 MW      b. 30 MW         c. 72 MW            d. 720 MW
ANSWER: a

3․ A power station has a maximum demand of 15 MW. The plant capacity is 20 MW. Find the reserve capacity of the plant?
a. 5 MW           b. 15 MW           c. 20 MW            d. 10 MW
ANSWER: a

4․ A generated station has a maximum demand of 30 MW, a load factor of 60% and a plant capacity factor of 50%. The reserve capacity of the plant is
a. 5 MW             b. 10 MW        c. 6 MW              d. 12 MW
ANSWER: c
 
5․ When a pumped storage power plant is operated in conjunction with a steam power plant
a. the operating cost of the steam plant become optimum
b. load factor of the steam plant is increased
c. chances of the tripping of the system decrease
d. all of the above
Explanation: Advantages of pumped storage plants:
1. Most economical as a peak load supply plant
2. Used as load frequency control
3. If it is combined with thermal plant of an area load factor is increased
4. Pollution free
5. Easily adaptable for remote operation
6. Operating time is minimum
 
6․ Which of the following statements is/are true?
a. A pumped storage plant is a base load plant
b. The starting time of pumped storage plant is very short
c. Pollution free
d. both 2 and 3
Explanation::
Peak load plants: A peaking power plant is a power station that only runs during high demands of electricity throughout the day during peak hours. Because of that, the price of electricity it generates is generally higher than the electricity generated by base load power plant, which operates continuously throughout the year.
Some examples are 1. Pumped storage plant
2. Diesel plants
3. Hydro plants ( when water availability is less)
4. Gas fired power plants
Advantages of pumped storage plants:
1. Most economical as a peak load supply plant
2. Used as load frequency control
3. If it is combined with thermal plant of an area load factor is increased
4. Pollution free
5. Easily adaptable for remote operation
6. Operating time is minimum
 
7․ On which one of the following cycles does a modern steam power plant work?
a. Carnot cycle        b. Rankine cycle        c. Otto cycle
d. Bell-Coleman cycle
Explanation::
The Rankine cycle is a model that is used to predict the performance of steam turbine systems. The Rankine cycle is an idealized thermodynamic cycle of a heat engine that converts heat into mechanical work. The heat is supplied externally to a closed loop, which usually uses water as the working fluid.
 
9․ What is the approximate efficiency of a normal thermal power station?
a. 30-40%        b. 45-55%            c. 20-25%             d. 60-70%
Explanation::
Steam is condensed into the water inside the condenser using circulating water. Most of the energy is wasted in the condenser for conversion of steam into water. So that thermal efficiency is low value i.e., 35 % to 40%.
 
10․ In coal fired thermal power stations, what are the electrostatic precipitators used for?
a. To remove dust particles setting on the bus bar conductors in the station switch yard
b. To keep the air heaters clean
c. To collect the dust particles from the flue gases
d. all of the above
Explanation::
The electrostatic precipitators (ESP) are extensively used in the thermal power plant or steam power plant for removal of fly ash from the electric utility boiler emissions. The use of electrostatic precipitators is growing rapidly because of the new strict air code and environmental laws. An electrostatic precipitators can be designed to operate at any desired efficiency for use as primary collector or a supplementary unit to cyclone collector.