计及老化线路电流承载能力退化特性的电力系统连锁故障分析

长期老化效应导致输电线路的电流承载能力退化以及老化失效风险增大，会使连锁故障风险进一步恶化。研究了输电线路老化对电力系统连锁故障的影响。首先，基于热平衡理论建立了输电线路老化相依的电流承载能力计算模型，阐述了电流承载能力与输电线路运行年龄的数值对应关系。在此基础上，综合考虑实时潮流和输电线路的老化效应，建立了包含实时潮流、运行年限、停运概率的三维映射关系，改良了输电线路动态停运概率模型。然后，通过引入概率阈值参数，建立一种改进的基于停运概率模型的连锁故障路径搜索准则，以连锁故障演化过程中的最大概率耦合事件为导向，在过滤低概率连锁故障路径的同时筛选代表性故障路径。最后，在改进的IEEE 39节点系统上进行了实例研究。算例结果证明，考虑线路老化效应后，由单线路意外事件触发的连锁故障事件增多，概率增大，其对应路径阶数增大，系统连锁故障风险明显升高，表明输电线路老化效应与连锁故障后果之间存在显著相关性。

Cascading failure analysis of power system considering current carrying capability degradation of aging lines

The long-term aging effect leads to the degradation of current carrying capacity of transmission lines and the increase of aging failure risk, which will further worsen the risk of cascading failure. The aging effect of transmission lines on the cascading failure of the power systems is investigated. Based on the heat balance theory, the calculation model of the current carrying capability dependent on the aging of transmission lines is established, and the numerical correspondence between the current carrying capability and the operation year of transmission lines is expounded. On this basis, considering the aging effect of real-time power flow and transmission lines, a three-dimension mapping relationship including real-time power flow, operation year and outage probability is established, and the dynamic outage probability model of transmission lines is enhanced. Then, by introducing probabilistic threshold parameter, an improved cascading path search criterion based on outage probability model is established. Guided by the maximum probabilistic coupling event in the evolution process of cascading faults, the representative fault paths are screened while the low probability cascading failure paths are filtered. An example study is carried out by the improved IEEE 39-bus system. The numerical results indicate that after considering the aging effect of the transmission line, the number of cascading failure events triggered by single line accidents increases, the probability increases, the corresponding path order increases, and the risk of system cascading failure increases significantly, indicating that there is a significant correlation between the aging effect of the transmission line and the consequence of cascading failure.