Protection Of Distribution System With Distributed Generations

Development of distributed generations (DG) technology is changing society's over-reliance on non-renewable energy sources. DG makes full use of environment friendly renewable energy sources, and it is the new direction of generating electricity. Presence of DG in distribution networks enhances power supply reliability and flexibility, but it has disadvantages along with so many advantages it have. UsingDGs results in distributed networks losing its radial configuration and consequently leads to complexity in control and protection of distributed networks. Moreover, the existing protective devices may lose their coordination.At present, researches on protection of distributed networks with distributed generations are mainly based on communication. Protections using communication channels require a lot of devices and great investment. Also, once the communication devices fail to work, those protections lose their function and result in poor reliability. This dissertation first introduces the traditional protection strategies for distributed networks and the impact of DGs'presence on protection coordination. Then the paper analyses the philosophy of protection based on communication.Finally the paper proposes a new protection scheme for distributed networks with DGs. Without changing the existing protection of distributed networks, we can use adaptive protection and fast protection as a whole to protect distributed networks with DGs.In order to enhance the power supply's reliability, we should reclose the breaker after the fault is clean. This paper discusses the influence of DGs on the reclose operation and adds the autoreclose function to the protection scheme. This paper introduces a computer-based relay protection device and fulfills the protection scheme mentioned above. Simulation results prove that the protection scheme is correct.