The distribution network is part of a constantly evolving system. The increase in consumption and connection of new consumers requires network topology redefinition and requires the construction of new substations and distribution network power lines. In most European countries, distribution networks by its topology, is radial. For purposes of network planning, a non-automatic and automatic approach can be used. This thesis defines an automatic approach for distribution network expansion planning, so for this purpose, an optimization model was first mathematically defined, and then implemented in Python. Before the practical part, the criteria considered in the process of network expansion planning as well as the possibilities of its integration in the optimization models are presented.