The correct answer is: D. all of the above.
A load curve is a graph that shows the amount of electricity that is being used at a particular time. It is useful in deciding the operating schedule of generating units, the sizes of generating units, and the total installed capacity of the plant.
The operating schedule of generating units is determined by the load curve. The units that are needed to meet the demand are turned on and off according to the load curve. The sizes of generating units are also determined by the load curve. The units that are needed to meet the peak demand must be large enough to meet that demand. The total installed capacity of the plant is also determined by the load curve. The plant must have enough capacity to meet the peak demand.
Here is a more detailed explanation of each option:
A. Operating schedule of generating units: The load curve shows the amount of electricity that is being used at a particular time. This information is used to determine the operating schedule of generating units. The units that are needed to meet the demand are turned on and off according to the load curve. For example, if the load curve shows that demand is high during the day, then the units that are most efficient at generating electricity during the day will be turned on.
B. Sizes of generating units: The load curve also shows the peak demand. The peak demand is the highest amount of electricity that is being used at a particular time. The units that are needed to meet the peak demand must be large enough to meet that demand. For example, if the load curve shows that the peak demand is 100 megawatts, then the plant must have at least 100 megawatts of generating capacity.
C. Total installed capacity of the plant: The total installed capacity of the plant is the total amount of generating capacity that the plant has. The total installed capacity must be enough to meet the peak demand. For example, if the load curve shows that the peak demand is 100 megawatts, then the plant must have at least 100 megawatts of generating capacity.