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-This paper considers the impact of the Inductive Fault Current Limiter (IFCL) on d irect ional overcurrent relays coordination. The coordination problem is formulated as a non-linear constrained mono-objective optimization problem. The objective function of this optimizat ion problem is the minimizat ion of the operation time of the associated relays in the systems, and the decision variab les are: the time dial setting (TDS) and the pickup current setting (I P ) of each relay. To solve this co mplex non linear optimization problem, a variant of optimization algorith ms named Firefly A lgorith m (FA) is used. The proposed method is tested on 8-bus power transmission systems test systems considering the influences of current relay under three-phases short-circuit with and without IFCL for d ifferent locality. The results show the effectiveness of the solution.

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In this paper, a new method for optimal locating multi-type FACTS devices in order to optimize multi-objective voltage stability problem is presented. The proposed methodology is based on a new variant of Particle Swarm Optimization (PSO) specialized in multi-objective optimization problem known as Non-dominated Sorting Particle Swarm Optimization (NSPSO). The crowding distance technique is used to maintain the Pareto front size at the chosen limit, without destroying its characteristics. To aid the decision maker choosing the best compromise solution from the Pareto front, the fuzzy-based mechanism is employed for this task. NSPSO is used to find the optimal location and setting of two types of FACTS namely: Thyristor Controlled Series Compensator (TCSC) and Static Var Compensator (SVC) that maximize Static Voltage Stability Margin (SVSM), reduce Real Power Losses (RPL), and Load Voltage Deviation (LVD). The optimization is carried out on two and three objective functions for various FACTS combinations. The thermal limits of lines and voltage limits of load buses are considered as securityconstraints. The simulation results show the effectiveness of the proposed NSPSO to solve the multiobjective optimization problem considered and capture Pareto optimal solutions with satisfactory diversity characteristics.

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