Under The Protection Of Wide-area Communication System

With the increasingly enlargement of electric network scale and the fast development of interconnected network, power system protection and stability control are becoming more and more important. In recent years, several major accidents among the world reveal that there is a lack of cooperation between relaying protection system and automatic safety device. It is also realized that relaying protection and automatic control must be strengthened from the point of view of whole network or regional network. The reliability of relaying protection must be improved, further more it is necessary to control relaying protection and automatic control device coordinately to enhance stability after fault.Based on modern communication technology, wide area protection system (WAPS) has been paid much attention since it is proposed in the end of last century. It finds a new way to deal with coordination issue between relaying protection system and automatic safety device in large power system. It leads the development of relaying protection. In order to coordinate devices installed all over the power system, information from each point is needed, including electric measurements, actuating signals and network topological structure. WAPS analyzes the information to decide the optimal control strategy and execute it. Wide area real time communication is the key technique to realize wide area protection in power system. It requires most reliability and least time error in data transmission. Weather the problem can be well solved depends on the development of communication technology in power system.The development of satellite, computer and communication technology provide hardware base for realization of wide area protection. At present, 10M and 100M Ethernet have been widely used, and wider bandwidth network such as 1G and 10G are becoming applied. Optical fiber has been widely used in power system. Taking Shandong electric network as anexample, SDH dicyclic self-healing optical fiber network have been set up between substation of 220kV and higher voltage grade. ATM service based on SDH has implemented partly. All these new technologies have brought communication revolutionary for wide area protection, and create opportunity to realize it.Communication research is carried out associated with the project of "study of wide area protection system based ?n 'three lines of defense'", to work out the best scheme for WAPS using present communication techniques. At first the WAPS structure and the development of each part are summarized, and the actuality and development of communication technology in power system is introduced. Then study is emphasized on how to reduce communication delay in order to meet the need of WAPS. Then discuss the communication means, such as communication physical media layer, communication mode etc., to find the scheme which is applicable of WAPS. Finally, evaluate the selected scheme together with advantages and disadvantages of communication system are discussed according to characteristic of power system. Finally , program for communication application 0...