中文摘要：

将经验所得设备电压耐受曲线（VohageToleranceCurve，VTC）不确定性的定性概念转换为定量表达是评估设备电压暂降敏感度的关键。用云滴表示VTC曲线的不确定事件，用云模型将VTC曲线的定性概念转换为定量刻画。根据测试样本，用逆向云发生器确定反映VTC曲线总体特征的期望、熵、超熵等数字特征值，用正向正态云发生器确定云滴概率密度函数值，并由此定量计算设备故障概率。以实测结果为样本，对Pc机进行评估，并与模糊评估法进行比较，证明云模型评估法正确、有效。

英文摘要：

The key in evaluating the equipment sensitivity caused by voltage sag in assessing the sensitive equipment due to voltage sags is to transform the qualitative concept about the uncertainty of voltage tolerance curve of the equipment into a quantitative expression. With the uncertainty event of the equipment voltage tolerance curve （VTC） represented by cloud drops, in this paper the qualitative concept of VTC is transformed into a quantitative expression by cloud model. According to the practical testing results, the numerical characteristics such as expected value （Ex）, entropy （En） and hyper entropy （He） of VTC are obtained by the backward cloud generator. Based on the arithmetic of directed cloud model, the probability density values of cloud drops are determined. Then, the failure probability of the equipment is calculated. As a case study, the personal computer is evaluated and the result is compared with that obtained by the existing fuzzy method. The case results show that the cloud model based method is correct and effective.