中文摘要：

综合考虑影响电压暂降评估的系统元件和保护设各可靠性参数的复杂性，从满足工程应用需要的角度出发，提出将可靠性参数表示为确定数和不确定数统一形式的联系数刻画方法，并对系统元件故障率和保护设备故障率联系数的分析方法进行研究。以现有故障定位法为基础，提出电压暂降频次联系数评估模型和算法。对IEEE30节点系统进行仿真，并与现有确定值、区间值评估方法进行比较，结果证明该方法的正确性和适应性，同时证明该方法同时包含了确定值和区间值评估法的优点，现有的确定值和区间值评估法是联系数评估法的特例，新方法能更好地满足工程应用需要。

英文摘要：

Considering the complexities of influencing factors on voltage sag assessment, such as the reliability parameters of system components and protection devices, the notion of connection number comprised of certain number and uncertain number was proposed to depict the uncertainty of reliability parameters for satisfying the requirements of the practical engineering. The connection number analysis method on the failure rate of system components and protection devices was studied. Based on the traditional fault location method, a new connection number assessment model and an approach were presented to assess the occurrence frequency due to voltage sags. The proposed method had been applied to the IEEE 30-bus test system. Compared with the current deterministic and interval number methods, the simulation results have shown that this method is the expanding of existing methods and it meets the practical application better.