This set of Power Systems Multiple Choice Questions & Answers (MCQs) focuses on “Economics of Power Generation”.
1. What is the advantage of sectionalizing of power plant?
a) High reliability
b) Low capital cost
c) Low maintenance
d) Easy operation
View Answer
Explanation: Sectionalizing means installing more number of small units rather than installing a big unit. Doing so enables us to maintain continuity of supply from rest of the units, when one or two units of plant fails. this makes the plant more reliable.
2. The area under the load curve represents ____________
a) the average load on power system
b) maximum demand
c) number of units generated
d) load factor
View Answer
Explanation: Load curve is obtained by plotting fluctuating load be keeping load on y axis and time in x axis. The area under the load curve represents the total number of units generated in a particular time.
3. Which of the following is equal to the maximum demand?
a) The ratio of area under curve to the total area of rectangle
b) The ratio of area under curve and number of hours
c) The peak of the load curve
d) The area under the curve
View Answer
Explanation: The ratio of area under curve to the total area of the rectangle is called load factor. The ratio of area under the curve to the number of hours represents the average load. The peak of the curve represents the maximum demand.
4. Load duration curve indicates _______
a) the variation of load during different hours of the day
b) total number of units generated for the given demand
c) total energy consumed by the load
d) the number of hours for which the particular load lasts during a day
View Answer
Explanation: The variation of load during different hours of the day is shown by load curve. Load duration curve is different from Load curve. Load duration curve indicates the variation of the load, but with the load arranged in descending order of magnitude. Load duration curve give the number of hours for which a particular load lasts during a day.
5. During which time the demand of electrical energy is maximum?
a) 2 A.M. to 5 A.M.
b) 5 A.M. to 12 P.M.
c) 12 P.M. to 7 P.M.
d) 7 P.M. to 9 P.M
View Answer
Explanation: From the load curve it is obtained that during early morning demand is always low. Around 5 A.M. it starts increasing and around 9 A.M. load reaches a high value and remains almost constant till evening except for some Dip during lunch hours. The load again starts increasing in evening hours and reaches its peak around 7 to 9 P.M.
6. Size and cost of installation depends upon ____________
a) average load
b) maximum demand
c) square mean load
d) square of peak load
View Answer
Explanation: The greatest of all “short time interval averaged” during a given period, on the power system is called the maximum demand. Maximum demand represents the maximum amount of load that is active, out of total connected load. So the size and rating of power plant depends on Maximum demand.
7. What is Demand factor?
a) Ratio of connected load to maximum demand
b) Ratio of average load to connected load
c) Ratio of maximum demand to the connected load
d) Ratio of kilowatt hour consumed to 24 hours
View Answer
Explanation: Demand factor is the ratio of actual maximum demand on the system to the total load connected to the system. The idea of demand factor was introduced due to the fact that all the equipments connected to the system does not work at a time in practice.
8. Which of the following represents the annual average load?
a) (KWh supplied in a day)/24
b) {(KWh supplied in a day)/ 24 } × 365
c) {(KWh supplied in a month)/(30 x 24)
d) (KWh supplied in a year) / (24 × 365)
View Answer
Explanation: The average load on the power station is average of load occurring at the various events. It can also be stated as energy deliver in a given period divided by the number of hours in that period. Option d matches correctly to these statements.
9. The load factor is __________
a) always less than unity
b) less than or greater than 1
c) always greater than 1
d) less than zero
View Answer
Explanation: Load factor is the ratio of average demand to the maximum demand. Average demand can not be greater than maximum demand. So the value of load factor is always less than unity.
10. In practice what is the value of diversity factor?
a) Less than Unity
b) Geater than Unity
c) Equal to or greater than Unity
d) Less than zero
View Answer
Explanation: Maximum demand of different consumers never occurs at a time, due to this the total maximum demand of the load is always less than sum of individual maximum demands. And hence, demand factor e.i. the ratio of sum of individual maximum demand to the maximum demand of total load is always greater than unity.
11. Coincidence factor is reciprocal of ___________
a) average load
b) demand factor
c) capacity factor
d) diversity factor
View Answer
Explanation: Coincidence factor is the ratio of total maximum demand to the sum of individual maximum demands which is the reciprocal of diversity factor.
12. Which of the following is called as cold reserve?
a) Reserve capacity available but not ready for use
b) Reserve capacity available and ready for use
c) Generating capacity connected to bus and ready to take load
d) Capacity in service in excess of peak load
View Answer
Explanation: Cold reserve is the generating capacity which is available for service but not normally ready for immediate loading. Reserved capacity available and ready to use are called hot reserve.
Sanfoundry Global Education & Learning Series – Power Systems.
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