The optimal loss reduction of distribution feeder based on transformer rearrangement

This paper presents an efficient strategy for transformer planning to reduce the system losses by means of transformer rearrangement. The load patterns of residential, commercial and industrial customers are derived by load survey and then used to calculate the transformer hourly loading. The three-phase load flow is used to solve the system losses and unbalance factor according to the load patterns and transformer hourly loading. With regard to transformer rearrangement, the Dynamic Programming (DP) technique is employed to find out the phase assignment of transformers. In the DP process, a backward procedure and a forward procedure are used to search for the best phase arrangement of transformers. The objective function including the cost of loss reduction and switching is formulated in this paper. To verify the efficiency of the proposed method, a practical feeder is selected for computer simulation. By comparison of the results between without transformer rearrangement and with transformer rearrangement, the proposed method is verified to be valid and available.