Abstract: Power systems are being expanded day by day with a more complex structure. The system topology always changes due to faults and/or operation requirements. Therefore; malfunctions might occur in the protection system which is one of the most important components for the system reliability, stability and economic operation. Distance protection relays fulfil the main protection function of the power transmission lines. In this study, an algorithm is created which recalculates the distance protection relay setting values depending on the topological changes of the network. The algorithm verified by testing on a selected area from the Turkish National Power Transmission System which comprises 154 kV 28 buses. Modelling of the power system carried out with Dig silent Power factory software. The algorithm is created in the DPL (Dig silent Programming Language) platform.

Keywords: Transmission line protection, distance relay, topology change, Dig Silent DPL script.