Background/Objectives

Extreme weather events such as hurricanes can cause severe damage to various components of the electrical power system. Transmission towers and distribution poles are some of the most vulnerable parts during such events. Studies show that utility poles subjected to wind loading are susceptible due to their in-service decay processes. However, most of the studies only consider failure events of utility poles to be statistically independent. In reality, loads are shared between adjacent spans and poles during high wind events. With the boundary conditions from the adjacent spans and poles applied, it is shown that the overestimation of failure probabilities in case of weaker poles and underestimation in case of stronger poles can be prevented. Furthermore, using these boundary conditions, system level reliability and resilience assessment frameworks are developed to study the impact of correlated events on the failure probabilities of the system. The objective of this study is to investigate the applicability of such frameworks in larger and more realistic systems such as the power distribution networks.

Approach/Activities

While the boundary conditions approach to address the impact of adjacent spans/poles on the wind fragility of individual poles is intriguing and shows promising performance, it is only studied for smaller systems (as few as 11 poles). The objective of this study is to first, summarize the initial findings from the literature for smaller systems and second, to devise ways to study the applicability of these models to larger systems by identifying potential challenges and addressing those. 

Results/Lessons Learned

Initial studies on the equivalent boundary conditions from the literature show that the adjacent spans/poles can have significant impact on the wind fragility of individual poles during extreme wind conditions. Moreover, the level of correlation between failure events reduces the overall probability of failures of the system. Based on these findings, the primary goal of this study is to investigate the applicability of these methods to larger systems and develop toolsets to assess system reliability and resilience and propose hardening strategies to improve the resilience of the system.