The new TEŠ generating unit 6 was connected to the power system with an existing 400 kV overhead line Podlog-Šoštanj on which unit 5 was already operating. Consequently the protection schematic of differential protection for the line with two feeders had to be changed for the case of line with three feeders. The masters thesis presents and analyzes a new configuration of differential protection of the 400 kV overhead line with three feeders. This new schematic of differential protection takes currents from three line feeders, which are connected to a single numerical terminal. A simulation network is modeled in a simulation software together with all the network elements. Same current transformers on all three line feeders are used in the simulation model. Current transformers are precisely modeled, together with their magnetizing curves which were obtained with measurements. Based on numerous simulated faults in the network the adequacy of differential protection parameter settings is analyzed. These settings are based on recommendations of the protection relay supplier. Finally, the suitable range of differential protection parameter settings is suggested in order to ensure absolute selectivity of protection.