Dividing load economically among power plants by use of the kilowatt — Killowatt-hour curve

FREQUENTLY, it becomes necessary for various reasons to study the relations between the output and the plant capacity of part of an electric system as distinguished from the whole capacity and the whole load. For example, it may be desired in a system of, say, 100,000-kw. capacity, to know how many kilowatt-hours will be absorbed by the load between the 50,000-kw. and 75,000-kw. loads, or how many kilowatt-hours lie below or above the 50,000-kw. line. One instance when such information is valuable is in estimating fuel cost for a year in the future. When operating steam plants where the system contains units of higher and lower fuel economies and where it is desired to get the greatest use out of the more efficient units and hold those of lower efficiencies for peak loads, the course can well be to forecast the output of each kind of plant and to predict the amount of fuel to be required by each.