Urban distribution network planning with 2-step ladder topology considering joint nodes

In this paper, the problem of upgrading an electric urban distribution network is considered. Although network planning has attracted considerable attention in the field of power systems since the early 1970s, the urban distribution network of Milano (Italy) shows significant and challenging peculiarities. Due to historical reasons, there are two separate distribution networks, previously operated by two different companies, which grew up independently and uncoordinated. This paper presents a mixed integer linear programming approach (MILP) for planning a new network configuration, called 2-step ladder topology, which optimally integrates the two networks already in place. The distribution system has to be shaped considering electric power cable joints already in place. Traditional electrical constraints are included in the model, such as power flow balance, lines thermal limit, number of customers per feeder. Extensive computational experiments are carried out on a small-scale system.