| The protective configuration of Traction substation is "one for one" independent configuration of high reliability. But it has some disadvantages including hardware configuration redundancy, complicated secondary wiring, large investment cost, lack of real time information sharing, high cost for operation and maintenance and inadequate overall coordination and the optimization of function. Centralized protection has begun to attract the attention of Chinese scholars as improvements are made in intelligent substation technology, High-speed Ethernet communications technology, the performance of computer hardware and the adoption of IEC61850standard. Centralized protection has simplified Traction substation Secondary wiring, realized real time data sharing, avoided repeated configuration of hardware and reduced the space needed for the installation of protection devices and equipments. In consideration of its advantages, Centralized protection will be the main trend for the development of Microcomputer protection in Traction substation.First the impact of intelligent substation, IEC61850standard and telecommunication network technology to Centralized protection is analyzed, and then made a comparison between the protective configuration of Traction substation and Centralized protection and construed the superiority of Centralized protection in theory and application. Moreover, the author has conducted research on the technical difficulties of centralized protection, like message transmission delay, and then adopted label-mark key message priority transmission method to ensure real time and reliable transmission of key information. Based on the existing network topology shaped in stars-type, rings-type and Bus-type, the author has proposed the Hybrid dual redundant stars-type network scheme, and made detailed explanation on its design, advantages and reliability. Through computation, the author can select the model for the hardware of centralized protection, including electronic voltage (current) transformer、merging unit、Optical Ethernet exchange board, and the CPU of centralized protection device.In view of its theoretical basis and hardware performance, the software tasks of centralized protection such as sample processing, protection and communication are well formulated. In the task of protection, five programming flowcharts are given. Since Windows operation system is featured in parallel running of multi-thread and multi-tasks, the author has developed the software of centralized protection software by adopting in fourier algorithm, and presented ways to deal with unusual sample data. The IEC61850-9-2message is capture packets by WinPcap, computed in fourier algorithm, and then delivered to the protective devices of centralized protection device. The protective package will make logical judgements and send orders like atresia、alarm or tripping operation. A platform for software test is builted which can send data through merging unit and the intelligent operation box and test and verify the software. The result shows that capture packets procedures can capture message correctly and make correct logical judgement when protection software is normally operating or is having a fault testing.From hardware reliability and software reliability to calculation and assess the centralized protection system reliability. At the same time, analysis the calculation result, and some measures to improve the centralized protection system reliability are given. |
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