Introducing Distributed Generation (DG) into the distribution and subtransmission systems has both positive and negative impacts. One of the negative effects of DGs is on system protection. This disturbance is caused by the change in value and direction of short-circuits current due to DG implementation. Fuse- Recloser and directional over current relays are effective schemes for the protection of distribution and sub transmission systems, respectively. These protection systems are designed prior to implementation of DGs. So that, presence of DGs results in miss-coordination of these schemes. Several methods have been proposed to solve this problem. These methods are expensive and have many constraints. In this thesis, this problem is dealt with revising protection schemes setting. Actually instead of changing protection system structure or using new elements, setting of current elements is changed. In this thesis, an optimized algorithm is proposed to design Fuse-Recloser protection systems. Proposed algorithm includes many steps. In each step, nominal values of Fuse and Recloser setting are designed using an optimization algorithm. Also, the effect of DGs in Fuse-Recloser coordination is demonstrated and an optimized method is proposed to revise protection system. Genetic Algorithm (GA) is used to solve this problem. Several optimization techniques have been proposed to solve the overcurrent relay coordination problem. In this thesis, hybrid GA method is used to determine the optimal relay settings. The hybrid GA method is designed to improve the convergence of conventional GA using a local LP optimizer. There are two approaches for solving the relay coordination problem in presence of DGs, minimizing relays operation time and minimizing number of relays setting changes. Keywords Distributed Generations (DGs), Fuse, Recloser, Directional overcurrent relay coordination, Hybrid genetic algorithm.
