Current Differencial Protection Using Optical Fiber Communication Channel And Its Application In Subway Power Supply System

The development, function and requirement of subway substation automation system were briefly introduced in this thesis. The principle and calculating method of current differential protection was analyzed in detail. And the synchronized data-sampling methods used in this protection were analyzed. The correlative functions of the device were configured and the corresponding setting principal of different function was presented. The functions of different modules were distributed and the hardware and software were designed, including hardware framework and the flow charts of software.In order to adapt to the alterable optical fiber multiplexed channel, the practice of the different synchronized data-sampling methods was discussed in detail and the data-adjusting method was improved on in this thesis. By analyzing the synchronous serial communication interface of master and slave CPUs and the required functions of the device to be manufactured, the synchronous serial communication interface of 80386EX was chose as the data communication interface and the tasks of master and slave CPUs were configured reasonably.According to the characteristic of subway power alternating current transmission line, a new synchronous method based on reference zero point of the wave shape of voltage was proposed. The method is suitable to short distance line such as the subway power alternating current transmission line. In addition, the merits and shortcomings were analyzed in detail and the method was simulated based on MATLAB. The method is significant to the domestic study on current differential protection using optical fiber communication channel of subway line or short distance line.