Distributed resources are small generators that are connected to distribution systems in order to supply a part of loads. Because of their special characteristics such as modern technologies, high efficiency of installation, they have economic, technical and environmental justifications. Increasing of distributed generations in distribution systems has encountered electrical companies to some problems. One of these problems is, altering the flow of currents in various sections of feeders during a fault, as well as increasing the short circuit current level. Thus, coordination of the protection systems may lose and protection devices mall operation. Under this coordination, the protection systems should be investigated again and if it is possible necessary, some setting are changed and some of devices are replaced. Some times regarding to under of resources and distributed generator penetration. Replacing the protection systems and using alternative protection scheme may be necessary. For this purpose, some of new protection schemes have been introduced. Purpose of this dissertation is study of impacts of distributed generation on the distribution systems short circuit current and traditional protective systems used in these systems. Protection systems for distribution systems are designed assuming the system to be radial. After connection, part of the system may no longer be radial. Since impacts of distributed generation on the operation of protection system depend on type, penetration, capacity and location of the resources, appropriate models for different sources such as synchronous generator, induction generator and inverter based sources and impacts of them on coordination of protection systems like fuse-recloser system are studied. In addition, results of detailed and approximate models are compared. The adaptive method presents a strategy to overcome the above problems. Scheme is suitable for distribution systems in present of distributed resource and is independent of size, number, and placement of distributed generators. This method is adaptive to temporary as well as permanent changes in distribution network and its region of implementation can be extended to more than one feeder. In protection based on neural network, a protective procedure for a distribution system including distributed generators is introduced. For online rapid fault detection, a feed forward perceptron neural network is used. Then for solving the installations of the protective systems due to connecting the distributed recourses, some of alternative schemes such as adaptive protection and neural network based protection scheme are reviewed and the performance of them on a test sy Keywords Distribution System, Protection, Distributed Resource, Fault Current, Adaptive Protection, Neural Network, Fuse, Recloser.
