Reserch On The Limited Wide Area Protection System Based On The Innovation Theory

The modern power grid structure is increasingly complex and the variable operation mode caused difficulties of traditional backup protection setting and long operation delay. Wide area measurement technology and advanced communication technology provide opportunities of development of wide area protection system. Wide area protection system takes advantage of rich wide area information and considers the domain main protection action and the system running state to achieve the function of backup protection. Such characters bring it advantages of short protection action time and small scope of fault removal. How ever, incorrect operation of protection will appears if there is bad data in the wide-area information. Innovation graph theory is applied to state estimation field, and has many unique advantages on identification of bad data, sudden load change and topology error. In particular, the rapidity of its bad data identification makes it possible to apply it to wide area protection. Under innovation graph theory, using catastrophe subnet to identify load mutation can reach an outstanding result, and mutation subnet range of applications can be extended to identify the short-circuit failure. Based on the innovation graph theory and the limited wide area protection system, this paper combines their advantages to construct a limited wide area protection system and improves the accuracy of protection by bad data identification and correction in wide area information.Firstly,this paper constructed the basic framework of a limited wide-area protection system. By analyzing the structure of the existing wide-area protection system, we established a limited wide-area centralized architecture. Based on graph theory, the principle of protection division is established, and it is verified through analysis of a regional power grid. At the same time, the tripping strategy of the limited wide area backup protection is analyzed through simulation system.Secondly, performance characteristics of the bus and line faults in the innovation graph are analyzed, then the fault innovation graph model is built. Research on the fault location method which has bad date in the wide area information is conducted, and a fault identification method by using the current path of mutation and subnet is proposed. According to mutations subnet witch indicates failure, it corrected the link branch calculation innovation by using the node injection current innovation. Based on innovation difference value after correction, it determined bad date and fault location. By taking innovation value after correction into the current differential protection criterion used the innovation value, thus it avoided the possibility that the bad data caused relay protection incorrect operation. Consequently, fault identification method based on mutations subnet and the current differential protection criterion verify each other, which can improve the accuracy of the protection operation.Finally, it established a 14 nodes-simulation system model, and simulated the condition that the bad data existed in the wide-area information and bus fault or transmission line fault at the same time. The simulation results verify the feasibility that using mutations subnet to recognize the fault and the current differential protection criterion using the innovation value would not be affected by the bad data.