中文摘要：

缺乏历史故障统计数据是电力系统运行风险评估中的突出难题。以架空线路为例，用模糊变量表示难以用统计数据得到的线路故障率，利用人工经验给出故障率的隶属度函数。然后基于随机过程和可信性理论，建立线路的状态模糊概率的计算方法。进一步，提出采用可信性的模糊模拟来计算线路风险指标（亦为模糊变量）期望值、乐观／悲观值的方法，用于在线风险决策。算例证明了所提方法的可行性和科学性，将为数据缺乏问题提供一条解决途径。

英文摘要：

Absence of statistical components＇ failure data is a great challenge for power system operation risk assessment. A fuzzy and random model was developed to overcome this challenge in this paper. Firstly, fuzzy variable was used to describe fault rate of line, whose membership function can be given according to the limited statistical data combined with experts＇ experience. Secondly, a method was presented to calculate line＇s fuzzy state probability, which is based on random process algorithm and credible theory. Lastly, an algorithm to calculate the expect value, optimistic and pessimistic value of the line risk index （fuzzy variable） was proposed for decision-making. Numerical tests prove the method feasible and practical.