5 th International Conference on Control Engineering & Information Technology (CEIT2017) , 17-19 December,2017, Sousse , Tunisia, Optimization and evaluation of Overcurrent Relays Coordination In Benghazi Distribution Network Using Genetic Algorithm Naser El Naily 1 , Saad. M. Saad 2 , Jamal Wafi 3 , T. Hussein 1 , Ibrahim Ighneiwa 1 , and Mohamed M. M. Elfituri 4 , 1 University of Benghazi, Electrical and Electronics Engineering Department, Benghazi, Libya 2 College of Electrical and Electrical Technology, Benghazi, Libya 3 General Electricity Company of Libya, Benghazi, Libya 4 Authority of Natural Science Research and Technology, Tripoli, Libya E-mails: { {naseralnaile222 & smuftahndi}@gmail.com,{ jamal_help & melfituri}@yahoo.com, Tawfiq.elmenfy@uob.edu.ly, and Ibrahim.ighneiwa@uob.edu.ly Abstract—When abnormal operating systems occur, the protection systems operate and isolate the affected parts from network to maintain the security of the network by optimally coordinate the protective relays. interconnected systems and the increasing demand for consumers are forcing operators to optimally coordinate protection system for continuous power circulation in the network. Protection Coordination Requires calculations for the breakpoint of protective relays and systematic enumeration of all possible loops in the network. Therefore, protection coordination should be done in an optimal manner to avoid mal-function, thus avoiding the outage and interruption of feeders from the healthy parts. The presence of backup protection in the protection coordination ensures the isolation of faults if the primary protection does not work effectively. In this study, the genetic algorithm was applied to determine optimum protection coordination for Benghazi distribution Network. GA searches it globally. Systems with OC considered and real coded GA is used in software MATLAB and the system will be evaluated by using ETAP software. Keywords—Protective relays; protection coordination; distribution network; genetic algorithm (GA); ETAP software. I. INTRODUCTION Several factors affect the continuity of power flow to the costumer, most importantly the coordination of protection system in the distribution network. In order to coordinate the protection system, power flow analysis and the short circuit level must be well known for the proper working of the protection system. The arrangement and coordination of protection system ensure the stability, reliability, and sensitivity of the protective relays in the distribution network in case of sudden faults. protective relays are the first line of defense for the distribution network against fault currents and isolating the affected areas from the rest of the distribution network by initiating and activating circuit breakers [1]. The way the relays work depends on the existence of a primary and backup protective relay for each section in the network. backup protective relays are working on isolating the fault in the case of primary protection failure. Optimal coordination of the protective relays ensures that the protection system decisions do not affect the reliability, reduce the damage caused to the equipment and decrease the areas separated by the fault [2]. OCR characteristic, according to International Electro Technical Commission (IEC), uses protection coordination such as normal inverse, very inverse and extremely inverse [3], [4], [5], [6]. Ordinarily, Protective relay detection for fault currents and issues in the distribution network happened when the measured currents increases to exceed the value of the protective relay setting, the two most important variables in the confeguration of overcurrent relay for better coordination between adjacent relays, the time multiplying setting (TMS), and plug setting (PS) for each relay which depends on the knowledge of the minimum fault current and the highest loading current [1], [7], [8]. Optimizing overcurrent relays passes through many stages. Firstly, trial and error [9], in [11] and [12] optimizing overcurrent relays achieved by applying graphical approach using curve fitting technique, [13] suggest employing fixed point coordination curve adjustment, and [14] suggest using computer programming software. In [14] deterministic methods formulated as mixed integer non-linear programming and solved with general Algebraic modeling. Complexity in MINLP assess construct coordination problem of DOCR with linear programming LP technique [10] and [15], in those methods, assumption of pickup current setting and TMS values had been chosen, and allowing operating time of each relay as linear function of TMS, and PS. Pattern search is one of the numerical optimization which require gradient problem to be optimize [16, 17]. Minimizing function of many variables had been done by simulated annealing combinatorial optimization technique [18, 19]. Those previous methods are quite unuseful for the large number of variables in large systems, and require long time analysis and large iteration amounts. Artificial Intelligence methods adapt and moderate 5th International Conference on Control Engineering&Information Technology (CEIT-2017) Proceeding of Engineering and Technology –PET Vol.33 pp.72-77 Copyright IPCO-2017 ISSN 2356-5608