Mixed-integer linear programming method for coordination of overcurrent and distance relays incorporating overcurrent relays characteristic selection

摘要

Coordination of overcurrent-overcurrent (OC) and overcurrent-distance (Dis) relays is one of the important issues in sub-transmission and distribution networks. In this paper, three approaches based on mixed-integer linear programming (MILP) is proposed for OC-OC and OC-Dis relays' coordination. Two of these proposed approaches are based on previously presented MILP-based approaches that were introduced for determining time and pickup-current settings in OC-OC relays' coordination problem. These predefined approaches are developed for obtaining optimal types of OC relays in addition to time and pickup-current settings in OC-OC and OC-Dis relays' coordination problem. A new MILP-based approach with less variables than the developed approaches is also proposed. This new approach has the ability to reach the best result in the short simulation time. In the new proposed approach, a cubic term which has two binary variables and one continuous variable must be replaced with a linear term. Therefore, a new linearization method is presented for this purpose. Three proposed approaches are implemented on the IEEE 8-buses and the IEEE 30-buses network. It is illustrated that new proposed approach from the point of view of objective function and simulation time is better than other methods especially for large networks. Therefore, new proposed approach is suitable for employing in the computing software as an efficient algorithm for relays' coordination.