New dynamic, branch exchange method for optimal distribution system planning

The optimisation of distribution system expansion planning constitutes a combinatorial problem. The application of accurate methods has been restricted to systems of small size, while approximate but more effective heuristic methods have been proposed. This paper presents a new, branch exchange method for the optimisation of multiyear distribution system planning. The problem is faced in two steps: first, a set of economical and technically accepted system configurations is constructed; second, the optimal sequence of system configurations, for a multiyear study period, is determined based on the set of economical configurations. The proposed method is fully dynamic, models accurately the economical and technical data and constraints, while all the system reinforcement and extension alternatives are modelled and optimised. The effectiveness is demonstrated by applications on a 134 node and 177 branch typical system. Load patterns, for two different seasons, are used to model load variations, while the installation or construction of capacitors, voltage regulators, lines and substations is optimised.