Coordination of electro-mechanical based overcurrent relays using CMA-ES algorithm

Bidirectional flow of power in power network imposes a serious threat on the reliable operation of overcurrent relays. Coordination of overcurrent relays is a challenging problem in multi-feed and heavily meshed power network. Complexity of problem increases as the size of system increases. Recently artificial intelligence based optimization techniques are applied successfully for optimizing the relay settings. Traditionally overcurrent relays are electro-mechanical in nature with discrete time dial and plug setting. Optimization of relay coordination problem considering electro-mechanical based over current relays requires an optimization algorithm which can handle the discrete types of variables. In this paper application of CMA-ES optimization algorithm is extended for coordination of overcurrent relays. Relay coordination problem is modified to optimize the relay setting for both near and far end faults. In addition to minimization of total operating time of primary and backup relays, coordination time margin is also optimized between 0.3 to 1.0 second for reliable operation of backup relays. The performance of proposed CMA-ES optimization algorithm is compared with other well established artificial intelligence bases optimization algorithms