The paper establishes an operational risk evaluation model of operation failure based zero sequence current protect, and points out real-time operating condition plays an important role to the reliability of relay protection. In view of the uncertainty and the change of operation mode of the actual operation of power system, according to the system's operation mode and principles of relay protection, we analyze the reason of action of the zero sequence current protection in detail, quantitatively calculate the fail-operation probability and false-operation probability of protection after system ground fault occurred, then list the consequences which protection failure and protection false may lead to, and calculate and analyze the risk index. The practicability of the method is demonstrated through a typical example by considering the effect of transition resistance.%建立了基于原理性运行失效的零序电流保护运行风险评估模型,指出了实时运行状态对保护的可靠性有着重要的影响.考虑由于电网实际运行中的各种不确定性和运行方式的变化,根据系统的运行方式和保护原理,详细分析了零序电流保护各段的动作原因,定量计算系统某处发生接地短路后各保护的运行拒动概率和运行误动概率,然后列举保护拒动和误动后可能发生的失效后果,计算并分析风险指标.考虑过渡电阻的影响,通过一个典型的系统实例,说明该方法的应用.
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