Ant Lion Optimizer for Optimal Coordination of DOC Relays in Distribution Systems Containing DGs

Traditionally, the distribution system is typically radial and the protection system has been designed for this purpose. After increasing the distributed generations (DG) in distribution systems, the direction of the electrical power flow and the short-circuit currents in the system should be changed. Moreover, at least a part of the system is converted from radial to loop due to the system contains multi power sources (main source and DGs). Thus, the protection relays are severely affected by the presence of DGs in the distribution networks and lost their coordination. Three fertile and robust meta-heuristic optimization techniques are competing in this paper for finding the optimal value of the pickup currents, Ip, and time multipliers setting of the directional over current relays (DOC) with different DG penetration levels, sites, and fault types and locations. These are an ant lion optimizer (ALO), artificial immune system, and particle swarm optimization. The objective function is minimizing the total operating time of the DOC relays. The transient stability of the distribution system is used as a new constraint for getting the optimal coordination of the DOC relays. Two study systems are considered to test the functionality of the proposed algorithms; they are IEEE-30 bus (distribution section) and practical 11-bus distribution system from Egyptian West Delta Distribution Utility. The comparative results verify the robustness and reliability of the ALO in minimizing the total operating time of the DOC relays while confines with the constraints. Moreover, they show that ALO has the highest accuracy and convergence efficiency while enjoying the reduced execution time.