Research On Transmission Technology Of High-speed And Real-time Signal In Power System

With the establishment of complex power system in China, the problems of traditional relay protection depended on local information measurement are gradually outstanding. Wide area protection system (WAPS) based on modern communication technology becomes the main development direction of relay protection. The key problem of WAPS is the real-time communication of wide area protection signal. Based on the analysis of real-time signal characteristics, the communication network of power system was researched to be appropriate for real-time transmission in this paper.Firstly, the current development of power communication network and the modern communication technology using in the network were analyzed in this paper. Secondly, the frame structures of relay protection main protection signal, the wide area measurement system (WAMS) signal and wide-area backup protection signal were analyzed. Then the communication range and communication process of wide-area backup protection signal were researched in the case of wide-area current differential protection system. WAMS transmission standard was modified to be appropriate for wide-area measurement information switching between two substations. Thirdly, according to the delay model of real-time signal transmission, the influence on real-time signal transmission was calculated in the aspects of the number of WAMS sub-sites, the load of link and the Diff-sev. The wide-area protection information response time was simulated in State Power Dispatching Network (SPDnet) of a province. The network topology and switching mode of the power dispatching network in a city were analyzed to meet the requirements of information switching between adjacent substations.The simulation results revealed that the current SPDnet in a province could meet the time delay requirements of200phasor measurement unit (PMU) sub-sites which sent information to the dispatching center; the main influence of transmission delay was the link load in access layer. The mean value of wide-area protection signal response time was less than30ms in the backbone layer of a province power system. The proposed scheme based on mesh topology and Multi-protocol Label Switching-Virtual Private Network (MPLS VPN) techenology was better than the current scheme in the aspects of transmission delay between PMU sub-sites and master station, the transmission delay between adjacent substations and the response time of wide area backup protection.