OPTIMUM ALLOCATION OF DISCHARGE TO UNITS IN A HYDRO-ELECTRIC GENERATING STATION'

IN OPERATING A HYDRO-ELECTRIC GENERATING STATION, the station output, corresponding to a given station discharge, depends on how the discharge is divided among the individual generating units in the station. The problem of determining the division of discharge which results in maximum output is certainly not new, and considerable study has gone into it. Published procedures appeared at least as early as 1919 [1], and since then several papers have been written on the subject [2, 3]. Unfortunately, the rules for optimum allocation of discharge given in some of these papers are not correct even for the simplest case of a station with identical units. Others present tables and charts for allocating discharge between units in specific stations but do not provide sufficient detail on how to carry out such calculations. Considering the importance of the problem in the economic operation of electric power systems with hydro stations, it seems desirable that the literature should contain a clear, detailed statement on how to determine the division of discharge that will produce maximum output. In this paper, the writer has attempted to provide such a statement by presenting a solution, including a simple computational procedure, which is sufficiently general to cover all cases met in practice. Individual units in a hydro-electric generating station are usually identical or they may be divided into several (most often two, but occasionally three or four) groups with the units in any one group being identical. The solution presented here takes advantage of this fact as follows. For each group of identical units the allocation of discharge to individual units which produces maximum output is determined. The total station discharge is then divided among the groups so as to produce maximum station output. Except in the simplest case of a station with all units identical, the calculations involved are of considerable magnitude. This is inherent in the problem and cannot be avoided.