Enhanced Algorithms for Transmission Protective Relay Coordination

Algorithms employing sparse techniques for coordinating directional overcurrent and distance relays on transmission network are described with an example system. Analytical expressions are derived for determining the limiting values of settings for zones 2 and 3 of distance relays on systems with both two and three-terminal systems. These values are then used to completely coordinate all the three zones of distance relays and to ensure maximum coverage of the lines by these zones. Some of the desirable enhancements added to the existing overcurrent relay coordination algorithm have also been described.