This study deals with the issue of entering into operation TS 220/110/35/20(10) kV Plat and the associated connection lines 220, 110, 35 and 20(10) kV, which connect the TS in question to the transmission and distribution network. TS Plat is a complex building where the process of transforming electricity into four voltage levels takes place. For this reason, it is necessary to plan the entry into operation of TS Plat in an optimal way, with as little unavailability as possible in the first line of the transmission network, the building in question assumed the position of the most significant power facility in the wider Dubrovnik area.