Every two years, ELES prepares the development plan of the transmission network. In the most recent Plan of the development of the transmission network 2009 -2018 we present the present state of the electric power system in Slovenia as well as the necessary interventions and measures taken in order ensure reliable, secure and high-quality operation of the transmission network as well as to provide its sufficient capacity, especially in the light of the planned construction of new power plants and expansion of distribution network.