Robust and adaptive coordination approaches for co-optimization of voltage dip and directional overcurrent relays coordination

Abstract Selectivity constraints are very crucial in directional overcurrent relays (DOCRs) coordination and could be affected by the change of short circuit current (SCC), which itself is highly dependent on network topology change (NTC). In this paper, robust and adaptive coordination approaches are used to achieve an acceptable level of power quality (PQ) and selective operation of DOCRs under NTC conditions and to find the optimal setting of DOCRs. Also, considering the importance of voltage dip, an objective function consisting of three main parts is used. The first part is defined to minimize the tripping time of relays, and the other parts are set to minimize the voltage dip energy index and voltage dip duration. Due to the importance of impedance of fault current limiter, it is considered as an optimization variable along with the time setting multiplier, setting current, and operation characteristic of DOCRs. Based on the simulation results, using robust and adaptive coordination, the DOCRs have selective operation during NTC, and voltage dip improvement is achieved.