Optimal Protection Planning and Coordination in Microgrids With SDGs, SFCLs, and OCR Using WOA

One of the critical challenges in power system protection is ensuring proper relay coordination. To achieve optimal coordination of protection systems and ensure security, fast cleaning, and selection of types of faults is a necessary priority. This priority, when hosting synchronous distributed generations (SDGs), although technical factors like power loss reduction and voltage profile may lead to the loss of protection coordination in these networks. To address this challenge, a truth table is initially introduced to assist users in selecting the optimal settings for directional overcurrent relays (DOCR). The objective is to reduce the total operating time of the relays. Normally, the conventional coordination between the pair of primary and backup relays is achieved with two settings, which include setting the time factor and excitation current. In addition to these settings, two constant coefficients of reverse time characteristics, that is, relay characteristic and reverse curve type, are continuously considered to be optimized. Defining an index to determine the penetration of SDGs based on structure, the Thevenin impedance ( Z th ) of the distribution system, and the impedance of SDGs is also very important in this field. Finally, optimization of the problem, including minimizing the losses, improving the voltage and cost profile, and protection coordination indicators, will be expressed to solve the problem. In addition, DGs increase the fault current level. Hence, employing suitable fault current limiters (FCLs) can help restrict fault current levels and protect network equipment from potential damage under such conditions. The Whale Optimization Algorithm (WOA) evolution is used to achieve the solution of optimal by unique response. So, the efficiency of the proposed design is applied to the IEEE 30 and 34 busses. The obtained results show the positive effect of the proposed method in determining the amount of penetration of SDGs in distribution systems.