Fig. 2,716.—Diagram illustrating diversity factor. By definition diversity factor = combined actual maximum demand of a group of customers divided by the sum of their individual maximum demands. Example, a customer has fifty (50) watt lamps and, of course, the sum of the individual maximum demands of the lamps is 2.5 kw. watts ("connected load"). The customer's maximum demand, however, is 1.5 kw. Hence, the diversity factor[A] of the customer's group of lamps is 1.5 ÷ 2.5 = .6. In the diagram the ordinates of the curves show the ratio maximum demand to connected load for various kinds of electric lighting service in Chicago.
[ [A] NOTE.—The diversity factor of a customer's group of lamps, namely, the ratio of maximum demand to connected load is usually called the demand factor of the customer.
Size of Plant.—Before any definite calculation can be made, or plans drawn, the engineer must determine the probable load. This is usually ascertained in terms of the number and distances of lamps that will be required, by making a thorough canvass of the city or town, or that portion for which electrical energy is to be supplied. The probable load that the station is to carry when it begins operation, the nature of this load, and the probable rate of increase are matters upon which the design and construction chiefly depend.
Fig. 2,717.—Load curve for one day.
Ques. What is the nature of the load carried by a central station?
Ans. It fluctuates with the time of day and also with the time of year.
Ques. How is a fluctuating load best represented?