Studying the impact of mutual coupling on distance protection relays using a real-time simulator

This paper examines the impact of mutual coupling between parallel transmission lines on the performance of distance protection relays using hardware-in-loop connection of actual relays on a real-time simulator. The results confirm the extent of the likely reach errors in a distance protection scheme in a practical field example, and demonstrate the need to carefully consider mutual coupling effects when designing distance protection schemes in parallel-line topologies.