Combined Positional and Boundary Protection for Transmission Lines

This paper presents a novel relay for power transmission line systems, which is based on a combination of positional and boundary protection principle. The relay installed at a substation is responsible for the protection of the transmission lines associated with the substation. The relay is able to offer fast trip for any fault on its protected line sections without the need for communication link. The paper presents a detailed description to the basic principle, algorithm and design of the combined positional and boundary protection relay.