The application of the distribution network protection can effectively reduce the fault interval and improve the reliability of power supply by using the selective power distribution of the power distribution line. But the existing protection schemes are mainly applicable to transmission network, for distribution network line hand in hand structure and the dynamic network topology changing frequently and other special problems, the existing one-way permissive protection is not suitable. In this paper, a new method based on character recognition is proposed to segment the distribution network. Each FTU feeling fault current sends out the trip request interrogation signal to adjacent FTUs, the FTUs receiving trip request according to whether they feel the flow determines whether return trip signal, FTU according to whether or not receive the trip signal(export FTU to identify the fault power direction) determine the location of the fault section and action. When the communication is interrupted, the subsection protection is refused, and the outlet protection in the substation can be used as backup protection. By using optical fiber communication technology to achieve two-way communication between adjacent protection devices, the method can effectively isolate the fault section directly, reduce the impact of the fault, and improve the reliability of power supply. The selectivity and reliability of the algorithm are verified by an example.%配电网允许式保护的应用可以通过实现配电线路多级保护间的选择性来有效减小故障停电区间、提高供电可靠性。但是现有的允许式保护方案主要适用于输电网，对于配电网线路的手拉手结构和时常发生改变的动态网络拓扑等特殊问题，现有单向允许式保护适用效果不佳。本文提出一种基于角色识别的双向允许式配电网分段保护新方法，感受到故障电流的各FTU分别向前后相邻FTU发送跳闸请求询问信号，接收到跳闸请求询问的FTU根据自身是否感受到过流判断是否返回跳闸允许信号，FTU根据是否在规定时间内接收的跳闸允许信号（出口FTU需识别故障功率方向）判断故障区段位置并动作。当通讯中断时，分段保护拒动，变电站内的出线保护可作为后备保护。通过采用光纤通信技术实现相邻保护装置之间的双向信息交流，该方法可有效直接地隔离故障区段，减小故障影响，提高供电可靠性。通过实例分析验证了该算法的选择性与可靠性。
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