Research On Weak Links Of Connection Modes Based On Reliability Block Diagram

Distribution network locates at the end of power system. Due to its direct connection with users, the quality and ability of power is guaranteed by it. Connection modes are the basic reflection of distribution network structure which is the focus of the urban distribution network planning and rebuilding. So the selection of connection modes in distribution network is very important, and the levels of the load points'reliability reflect the performances of connection modes. In order to realize the secure and economical operation of the distribution network, it is necessary to make some researches not only on the changing law of the loads reliability, which is carried by the connection modes, and the weak links, but also on the largest number of load points under the condition of meeting the reliability requirement to offer useful references for the power system planners, operators and maintenance men.Power-system-reliability evaluation is applied to connection modes. Based on the reliability block diagram theory, the reliability block diagrams of several common connection modes are made, which lay the foundation for more complex connection modes'reliability block diagrams.A method of finding out the weak link in a distribution network is given, which uses the parameter of reliability importance, whose formula is defined. The method is an effective way of analyzing a network's weak link. The paper analyzes each load points'static weak link in common connection modes, then calculates out the reliability of each load point and finds out the law of their changes, for the references of the power system planning and implementation. The largest number of load points carried by common connection modes can be calculated out under the condition of meeting the requirement of the actual parameters of the .planning region. As the reliability of lines has an effect on the load points'reliability, the influence law of load points'reliability under different common connection modes are analyzed, which can provide a theoretical basis for network planning.Each load points'dynamic weak link in several connection modes is analyzed; hence the influence law of each load point's reliability is figured out, which can offer useful references for the maintenance.Actual example verifies the correctness and validity of the proposed methods, which can provide effective decision-making supporting information for power system planners.