Study On Reliability And Routing Selection Of Wide Area Protection Commnication System

Wide Area Protection System (WAPS) is a protection and control system simultaneously achieving relay and security and stability control. WAPS acquires multi-point information of the grid by modern measurement and communication technologies, and realizes isolated fault accurately and quickly through comprehensive decision, also identifies the disturbance which possible serious consequences to the power system and takes appropriate control measures to eliminate or mitigate the consequences. Wide area protection is based on communication system with high reliability and real-time. The development of modern communication technology provides the possibility of real-time, so the reliability of communication system is an important factor in reliable operation. Studying on the reliability analysis of the communication system and routing methods with meeting the requirements of reliability and delay of information transmission is very important to improve the reliability of wide area protection.Wide area protection communication system is a complex system, according to the functions, which can be divided into three subsystems: substation communication system, wide area backbone communication network, the center communication system. This paper analyzes the structure of the subsystems and establishes reliability model under different structures of each subsystem by using the availability index, and calculates the overall reliability of the communication system, finally gets the most reliable structure of wide area protection communication system, to provide a theoretical basis for communication system's design.Differing from conventional communication network, communication network for power system wide-area protection requires high reliability and strict delay characteristics. Therefore, the routing selection of communication network for wide-area protection has particularity. The occurrence of random failures makes shortest path be not necessarily the best path suitable for information transmission, sometimes it needs to choose a path with less failures. To solve this problem, according to the state of communication network's nodes and links, drawing on the reliability principles of routing selection, this paper presents a routing selection method for wide area protection based on communication reliability and delay requirement, which finds the most reliable path with meeting the transmission delay and bandwidth requirements for communication between nodes. A routing model is established and the method to solve the model is given, also the importance of network unit is analyzed. The model is suitable for optimal selection of information transmission paths in wide-area protection in normal state and path reconstruction after component failure in communication network. The results of case study show that the model and algorithm are simple, convenient, and exact. The model can balance the impact of reliability and delay to information transmission of wide-area protection, and fully improve reliability of wide-area protection information transmission.