Study Of Centralized Protection Based On Digital Substation

Digital substation can share the information of the whole substation. Researchers have proposed the centralized protection based on digital substation, the funtion, the structure, the reliability and the cost of which have been studied. Internally, the structures of centralized protection are mostly focused on.This paper introduces the definition, the function and the goal of the centralized protection from the theoretical point of view. Based on the theories of the centralized protection, two kinds of protection systems are proposed, which is protection system of digital substation based on GOOSE type network and the centralized protection system of digital substation. The overall plan, adaptive partition methods and the reliability of the system are mostly focused on.The study of protection system of digital substation based on GOOSE type network has focused on the overall plan, adaptive partition methods and the reliability of the system. This system is constructed by adding a functional module to the traditional protection devices. The module is used to detect the fault direction and store the real time topology of the substation. The protection devices sent out and receive the information of the fault direction through the GOOSE message according to the relations of subscriber and publisher. The information of the fault direction and the real time topology of the substation are used to identify whether there is a internal fault occurred to component being protected.The study of the centralized protection system based on digital substation has also focused on the overall plan, adaptive partition methods and the reliability of the system. This system has only one set of protection device. The device gathers the real time information of the values of currents, the values of voltages and the states of breakers. The current-differential algorithm and the real time topology of the substation are used to identify the fault occurred to the primary equipment.One methods of improving the reliability of the two protection systems is proposed. It is about tackling the situation of information missing. When there is information missing, the protection system based on GOOSE and centralized protection systems perform better then traditional protection system in selectivity and speed when fault occurs.Finally, PSCAD-EMTDC and VC++6.0 based fault simulations are carried out to the three different protection systems, the traditional protection system, the protection system based on GOOSE type network and the the centralized protection system. The analysis of the simulating data proves the feasibility of the two new protection systems. By comparing, we draw the conclusion that when there is information missing, the two proposed protection system operate much more quickly than traditional protection systems, thus improve the selectivity and reliability of relay protections.