中文摘要：

指出电网运行方式和阻抗继电器的特性对距离保护运行可靠性有重要的影响，并提出了其风险评估模型。首先根据各种圆动作特性阻抗继电器的整定阻抗和最大灵敏角，详细描述了启动概率和不启动概率在阻抗复平面上的分布情况，并求取其在特定测量阻抗区域内的平均值作为基础可靠性参数。然后考虑各段保护的动作时限，分析运行时距离保护拒动和误动的模式，并推导出计算其概率的公式。最后分析距离保护的错误行为对电网的影响，构建了失负荷风险指标，并用算例说明了该方法的应用。

英文摘要：

To reveal that the operating mode of power grids and characteristic of impendence relay have significant impact on the reliability of distance protection, an operational risk evaluation model is proposed for distance protection. Firstly, the distributions of action probability and inaction probability on the complex impendence plain are described in detail according to the setting impendence and angle for various impendence relays with circle performance characteristics, and the probability average on the special measuring impendence region is calculated out as the basic reliability parameters. And then, the mis- operation mode and real-operation mode of operational distance protection are analyzed considering the tripping time, furthermore the calculating formulae of m/s-operation and mal-opera＇tion probabilities are.deduced. Lastly, after analyzing the impact of the mis-operation and real-operation on the power grids, the risk indexes of loss-of-load are put forward, and the application of this method is clarified using an example.