Application of the ant colony system for open wye-open delta transformer´s phase sequence adjustment

In this paper, a co-operative agent algorithm, the ant colony system, for open wye-open delta (OYOD) transformer´s phase sequence adjustment is proposed. Many utility companies used the OYOD transformers to serve various customers since it can serve both the three-phase and single-phase loads by using two single-phase transformers. Through the OYOD can obtain more economical for transformer cost management, but it also achieves the severe phase unbalance problems. Phase unbalance is one of the prime reasons to cause extra line loss and ground current relay trip in the distribution systems. The formulation of OYOD transformer´s phase sequence adjustment is a combinatorial optimization problem with non-linear and non-differential objective function. In this paper we choose the ant colony system to solve the problem since the ant colony system has the characteristics of positive feedback, distributed computation and the use of a constructive greedy heuristic. Test results shown that the proposed ant-colony-system based algorithm can offer an optimum solution for OYOD transformer´s phase sequence adjustment.