中文摘要：

根据Manchester模型和最优潮流理论，提出了改进的连锁故障模型。该模型通过快动态和慢动态2个时间尺度对系统连锁故障过程进行描述，并通过电量不足期望值对系统的停电风险进行评估。对我国某区域电网进行了算例分析，研究了系统负载率和关键线路的故障率对电网停电风险的影响以及临界负荷情况下电网的幂律特性，对系统规划和运行人员分析连锁故障过程并采取有效措施降低系统停电风险具有参考意义。

英文摘要：

Based on Manchester model and optimal power flow （OPF）, an improved cascading failure model is established. This model describes cascading failure process by two different time scales, i.e., the fast dynamics and the slow dynamics. In this paper the blackout risk of power system is evaluated by expected energy not supplied （EENS）. The analysis on a certain regional power network in China, which is taken as a calculation example, is conducted; the impacts of system load factor and the fault rates of key-lines on blackout risk of power network as well as the power law process under critical load are researched. The results of this research is available for reference to the personnel engaging in system planning and operation to analyze the process of cascading failures and to adopt effective measures to reduce the blackout risk.