Economics of Trolley Coach Power Supply

The total cost of power delivered to trolley coaches is influenced by system engineering as well as by prevailing power rates. In the case of a single-unit rectifier substation, the equipment cost per kilowatt decreases as substation rating increases. With increases in substation rating, however, proportionately more feeder copper is required to distribute the power from each station. Evaluation of these factors for various headways reveals substation ratings and spacings which result in minimum system investment. Cost of power delivered at the trolley coach is the sum of fixed charges and operating costs of the substations and overhead. Such factors as the number of points of power delivery, maintenance expense, and depreciation rates affect the over-all power cost. Their influence upon selection of substation rating is discussed. By careful investigation of all variables, the transit operator is able to minimize the cost of power delivered to his vehicles.