Based on the set theory and the Prolog programming language, the paper develops methods by which the allocation of loads to the busbars of distribution substations may be determined automatically. Starting from the initial possible allocation of loads to the substation busbar sections, a formulation for load allocation is first developed using set theory. The `generate evaluate and test¿¿ technique and the depth-first search method are then applied to the solution-seeking process. The formulation is implemented and recursive search procedures are derived using the Prolog language. The Prolog software aid developed includes a complete solution generator from which all hypothetical solutions are generated, an evaluator which prunes invalid solutions, and a tester which produces feasible solutions by checking the load allocation constraints related to the firm capacity of the distribution substations. An application of the methods developed is given for two 11 kV interconnected substations which include 5 busbar sections and 10 ring loads.