Novel Modified Characteristic Curve of Distance Relays by Consideration of Harsh Weathers

One of the main challenges in the operation of power systems is the protection of transmission lines against faults. In the majority of power systems, distance relays locate the faults in transmission lines with high speed, reliability, and selectivity. Moreover, due to the installation of distance relays in each line, the whole of a transmission system is also covered by these devices. The operation of these devices depends on the parameters of transmission lines, and the design of their settings is based on the assumption of fixed transmission line parameters. However, due to the harsh weather in Nordic countries, this assumption is not true, and variation in weather conditions rapidly will have an impact on the accuracy of these devices significantly. In this paper, the impact of harsh weather on the operation of distance relays is investigated, and an improved distance relay setting is proposed to improve their operation of them. The effectiveness of the proposed method is proved during different conditions by simulations.