In this paper the necessary equations for considering existing network reconfiguration in the disjunctive linear model used to solve the problem transmission expansion planning. In the traditional methods used for solving this problem new transmission lines and two-winding transformers are commonly used as expansion candidates. However, reconfiguration of existing network has not been considered as a valid solution in the classical models. The Garver test system and a Colombian system are used to show that considering network reconfiguration can reduce investment costs of the transmission expansion planning problem. This work shows that an optimization model that includes conventional candidates and reconfiguration produces better expansion signals in the transmission lines of electric power systems.