Optimum Coordination of overcurrent relays using CMA-ES algorithm

Coordination of directional overcurrent relays in a meshed power system is a challenging task for the protection engineers. In the earlier days it was done manually. Linear and non-linear programming optimizing techniques were very frequently used for Coordination of overcurrent relays. Presently, artificial intelligence (AI) techniques are applied for optimal co-ordination of directional overcurrent relays (DOCR). This paper discusses application of Covariance Matrix Adaptation Evolution Strategy (CMA-ES) for optimal coordination of DOCR relays in a looped power system. Combination of primary and backup relay is chosen by using Far vector of LINKNET structure, to avoid mis-coordination of relays. Coordination of DOCR is tested for IEEE 30 bus distribution systems using CMA-ES. The objective function (OF) is formulated to minimize the operating time between backup and primary relays (coordination time interval). Results are compared with the optimized values of Time dial setting (TDS) and Plug setting (PS) values obtained from modified differential evolution algorithm. The proposed algorithm (CMA-ES) gives optimal coordination margin between 0.3 to 0.8 second and no miscoordination between primary and backup pairs.