The distribution system is an important part of the total electric power system, as it provides the final link between the bulk system and the customer. Analysis of the customer failure statistics of most utilities shows that the distribution systems makes the greatest individual contribution to the unavailability of supply to a customer. Distribution system reliability is an important issue in system planning and operating. At present, the electric power industry is undergoing considerable change with respect to structure, operation, and regulation. As a result of power system restructuring, using distributed generation (DG) has been increasingly attended. By definition, the DG is of limited size (generally 10 MW or less) and connected at the substation, distribution feeder, or customer load level. Nowadays, using DG is a good method to contribute small sellers in competitive electricity market and also a convenient method to generate electric power from renewable energy. The study and reliability evaluation of distribution system with DG is essential; since these generators are commonly connected to distribution systems. In this thesis, reliability evaluation of distribution systems in different operation modes of DG is studied. Both analytical and simulation techniques have been used to evaluate the reliability of distribution system containing DG. An analytical method is proposed in order to evaluate reliability indices in the presence of certain amount of generated power by DGs with continuous or temporary availability. This method is based on connection matrix and hourly load curve. Accuracy of this analytical method is comparable with the simulation methods. Furthermore, another algorithm is proposed for networks with wind turbine, which is a common example of uncertain generation sources. This algorithm is based on random modeling of DG by using the Monte Carlo Simulation (MCS). Both methods are applied to a distribution test system and standard indices of reliability are calculated to show good performance and accuracy of proposed methods. Key Words Reliability, Distribution System, Distributed Generation, Analytical Method, Monte Carlo Simulation
