中文摘要：

为对压敏电阻在雷电过电压作用下的可靠性进行评估,提出了基于Markov过程的压敏电阻可靠性评估模型。通过Markov过程分析了压敏电阻在限压运行中不同状态的转移过程,同时推导出了压敏电阻在雷电冲击下的平均失效前时间的计算公式。以这一公式为基础,建立了相关的可靠性评估模型。然后通过配电变压器线路上雷电暂态过电压进行建模仿真,得出了压敏电阻在3种状态下的雷电流概率。将雷电参数代入公式计算压敏电阻的可靠性,预测了其在不同运行条件下的寿命：对转化率为1/10,动作电压620V、通流容量40kA的34S621型压敏电阻,当转化率取1/50时,其寿命〉4a;压敏电压取910V时,其寿命〉5a;通流容量取40kA时,其寿命〉3a。分析表明：压敏电阻的寿命与转化率成反比,而与压敏电压和通流容量成正比。

英文摘要：

To predict the reliability of metal oxide varistors（MOVs） under lightning overvoltage,a new assessment model for MOV was established based on Markov process.The Markov process was used for analyzing the transfer behavior of operating MOV in different states.The computational formula of the mean time to failure（MTTF） for MOV under lightning impulses was derived.Based on this formula,a realistic model was set up for predicting the reliability of MOVs.By simulating lightning transient of a distribution system,the lightning current probability was calculated in three operation states,and the reliability and lifetime of MOVs in different conditions was also estimated.For a 34S621 MOV which has a conversion rate of 1/10,a rated current capability of 40 kA,and a rated breakdown voltage of 620 V,when the conversion rate changes to 1/50,the breakdown voltage and the current capability are selected to be 910 V and 40 kA,respectively,the lifetime of the MOV will be more than 4,5,and 3 years,respectively.It is concluded that the lifetime of MOV is inversely proportional to the conversion rate,and it is directly proportional to the breakdown voltage and current capability.