UHVDC系统故障树分析误差及灵敏度分析

FTA Error Analysis and Probabilistic Sensitivities of UHVDC Systems

采用故障树(fault tree analysis,FTA)法分析UHVDC系统可靠性及灵敏度。考虑多状态元件同站双极互为备用逻辑关系,建立所有故障方式的故障树。基于串、并联结构,分别建立FTA和状态空间(state space,SS)可靠性分析模型。发现FTA误差,源于对串联系统不当引入多个元件同时故障状态。分别采用FTA和SS法计算UHVDC系统状态概率和灵敏度,量化前者误差。结果证实FTA得到的不可用率确实较SS法偏高,误差与元件个数及元件可用度有关。发现系统故障概率对同一元件修复率和安装率的绝对灵敏度之比,为其安装率和修复率之比的平方,同一元件所有参数相对灵敏度之和为0,据此可大幅降低灵敏度分析计算量。

Fault tree analysis （FTA） is used to evaluate the reliability and sensitivity of ultra high-voltage direct-current （UHVDC） system. Considering that some elements in both poles are expected to reserve for each other in the same station, all kinds fault trees for different running models are built. To keep things simple, the reliability models of FTA and state space （SS） methods for series and parallel systems are analyzed initially. It is newly find that the error of FTA arises fi＇om falsely introducing failure modes involving more than one component. The UHVDC systems are decomposed to series and parallel systems to analyze the error. The state probability, the absolute and the relative sensitivities of the systems are quantified, and the error compared wit^a those of using SS is proposed. Numerical results show that the failure probability of the series system using FTA is higher than that using SS. The error is related to number of elements and reliability parameters. The ratio of absolute sensitivity to repair and installation rates equals to the square of the ratio of installation rate and repair rate. The sum of all relative sensitivities to one component is 0, which may notably reduce calculation effort of sensitivity analysis.