Coordination of distance relays and directional over current with optimal injection of DG capacity using smart method

One of the most applicable relays in protecting the power system is distance and overcurrent relays. In transmission and distribution networks, protection is usually performed by distance protection, and overcurrent protection is used as a backup for distance protection. In the present study, a new approach was provided to coordinate distance and overcurrent relays using pickup current, time adjustment coefficient, and overcurrent relay characteristics to delay these relays as backup for distance relays. It is possible to adjust the second zone of the distance relays' operating time with a fixed and normal value using instantaneous operation relays with changes in coordination constraints. In the proposed method, the coordination problem was solved using GA algorithm. A protection coordination index is then provided to evaluate distributed generation sources' impact on the protection coordination of distance and overcurrent relays. A new method was proposed to obtain the maximum injection capacity under coordination constraints using MATLAB and DIGSILENT software's parallel performance. The proposed method was implemented in IEEE 9 and 39 bus sample networks. Finally, the obtained results were compared and evaluated.