Mohamed Kamal Eldin Essawy Afifi <br/><br/>
Applying multi-objective optimization for enhancing directional overcurrent relays coordination /  
 تطبيق الأمثلة متعددة الأهداف لتحسين التنسيق بين مرحلات الوقاية الاتجاهية ضد زيادة التيار 
Mohamed Kamal Eldin Essawy Afifi ; Supervised Doaa Khalil Ibrahim , Mahmoud Sayed , Hebatallah Mohamed Sharaf 
 - Cairo :   Mohamed Kamal Eldin Essawy Afifi ,   2020 
 - 100 P . :   charts ;   30cm 
<br/><br/>Thesis (M.Sc.) - Cairo University - Faculty of Engineering - Department of Electrical Power and Machines Engineering 
<br/><br/> One of the most important requirements of protection system is to isolate and disconnect faulted parts of the system selectively and quickly. Overcurrent relays are used as primary protection for distribution systems or combined with distance relays for protecting subtransmission systems. Coordination of directional overcurrent relays (DOCRs) is a main challenge in power system protection. This thesis studies DOCRs coordination by achieving two main goals. The first goal is introducing a DOCRs coordination comparative study using single-objective and multi-objective optimization approaches. Different fault locations are considered for each method then the results are compared based on the mean fault clearing time of the system, maximum primary and backup relays operating time and maximum coordination time interval. The second goal is introducing an enhanced two-fault point coordination scheme. The scheme employs severity weighting factors for each relay with respect to fault location. The proposed severity weights are calculated based on the ratio of fault currents that pass through the relay so relays with higher and more severe fault current should operate faster than relays with less severe faults 
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<br/><br/><label>Subjects--Index Terms: </label>Directional overcurrent relays (DOCRs)  Fault current severity Multi-objective optimization