The Fault Detection And Isolation Technology Studies Of Distribution Network With Distributed Power

Distribution generation (DG) technology has been rapidly developed in recent years. The direction and distribution of the short circuit current in distribution power system has changed a lot due to the introduction of DG, as a result, the existing feeder protection there may be reduced sensitivity, tripping failure, malfunction, and so on, which gives distribution network fault detection and isolation brought about many problems. Therefore it is necessary to carry out related research, find new ways to solve problems and put forward countermeasures, and of great significance for the distribution network with DG in the development and promotion.On the basis of previous research, after qualitative analyzing the influence of distribution networks with DG on the protection, we found the impact of the line protection will be different, when the relationship of the fault point and DG position has changed. As following:When DG upstream failure, the fault current flowing through the fault feeder protection is only relevant to the system power, but if the reverse current caused by the DG is too large, it may lead malfunction of the feeder protection between fault point and DG. When the fault occurred in the DG access feeder, the protection have no effect on the DG downstream. When the fault occurred in the feeder of DG downstream, the fault current flowing through the protection will be increased by the help of DG. Based on the above conclusions, we improved the current protection configuration, and integrated it into the distribution network under different fault detection and isolation scheme, then put forward three kinds of fault detection and isolation schemes to response the distribution network with DG, including Recloser-Sectionalizer model improvement program, Distributed Pilot program and Master-Slave Regional Pilot program based on communications, and analyzed characteristics and scope of their. Focus on the master-slave regional pilot program conducted in-depth research, including fault detection and isolation algorithm, the design and implementation of device and communications programs. Every switch in the distribution power system is equipped with slave protection device (SPD)by Master-Slave Regional Pilot program. Each SPD has a fault direction element inside, which measures the voltage and current of its position and determines the fault direction. When the distribution power systerm is failure, the fault direction information are collected through the communication system, and used by fault detection and isolation algorithm. The reliable action of fault direction element, reasonably design of fault detection and isolation algorithm and fast communication is the key to program implementation. We analyzed the program requirements on the system before scheme implementation, constructed the basic structural framework, and focusing on core of the system algorithm discussed various situations, including fault detection algorithms, fault isolation algorithms, the method to deal with system structure change and the processing with incomplete information. Through the construction and implementation of each functional module, we develop the host monitoring system. Fault direction detection is achieved by SPD, in which the fault direction element use fault component and 90°wiring principle to ensure the reliability. The slave device is developed for the implementation of the program with both hardware and software, better to meet the needs of fault detection, and has a friendly interactive interface and networking functions.In the processing of fault detection and isolation, master and slave device achieve the interaction of information by the optical fiber communication network. This paper developed a detailed communication strategy and built a reliable communications platform, to ensure the system communication quickly. Finally, we set up the test platform and developed the corresponding test program to complete the entire system testing, which examined the Feasibility that Master-Slave Regional Pilot program in the distribution network with DG could also correctly and rapidly accomplish the fault detection and isolation.