Alpha Harris Hawks Optimization based Overcurrent Relay Coordination with Hybrid Time-Current-Voltage Characteristics Considering the Grid-Connected Distributed Generation

The conventional protection schemes may lead towards the inadvertent operation of the protection devices with the increased penetration of renewable energy sources based distributed generation (RES-DG) in distribution networks (DN). The miscoordination and the malfunctioning of directional overcurrent relays (DOCR) may occur due to significant change in the fault current level (FCL) and the change in the network topology form the radial to ring topology caused by the RES-DG. Optimization algorithms (OA) and modification in relay characteristics were mostly used to tackle the DOCR miscoordination problem. However, in this paper, a fast and an accurate protection coordination scheme is proposed to eliminate the DOCR miscoordination and to reduce the overall operation time of DOCRs by employing an advance optimization algorithm along with an innovative modification in the relay characteristics. In the first step, time-current characteristics (TCC) of the conventional DOCR are modified to a hybrid time-current-voltage (TCV) characteristics by including the effect of the fault voltage in the relay characteristics equation. Thereafter, the performance of conventional Harris Hawk's optimization (HHO) is enhanced with an improvement in the exploration strength of the HHO by an adaptive mutation-selection of the alpha hawks during each iteration named as alpha-HHO (alpha-HHO). The protection coordination problem is formulated as a non-linear constrained optimization problem. The proposed protection scheme is evaluated on the IEEE-8 bus meshed DN. The standard IEEE-8 bus test system is modified by integrating multiple squirrel cage induction generators and PV-based RES-DGs at optimal bus locations. Detailed numerical studies are carried out with the help of simulations to show the performance of the proposed scheme. The results are compared with the existing protection schemes reported in recent literature. The investigation results show that the highest reduction in overall relay operating time with zero mis-coordination is achieved with the proposed scheme.