Seismic response and force transfer mechanism of flexible conductors in multi-span substation systems considering bending stiffness and slackness

The outgoing line system in substations is highly susceptible to seismic damage due to the complex dynamic interactions between flexible conductors and interconnected equipment. However, most existing studies model conductors as tension-only elements, neglecting their bending stiffness and geometric slackness, which may lead to inaccurate predictions of seismic response. This study presents an integrated experimental, numerical, and theoretical investigation of the dynamic behavior of flexible conductors and their influence on a typical three-phase multi-span outgoing line system in a 220 kV substation. Quasi-static tests demonstrate that flexible conductors exhibit linear-elastic bending behavior, with stiffness ranging from 1 to 1.7 kNm 2 under typical service axial forces. A refined finite element model incorporating conductor bending stiffness is developed, revealing that circuit breakers are the most vulnerable components, with bending moments 1.8 and 4.7 times those of current transformers and disconnectors, respectively. Furthermore, the effect of conductor slackness is systematically evaluated, showing that increasing slackness significantly reduces axial forces and bending moments. A slackness of 10% decreases bending moments on circuit breakers by 8%–13%. Theoretical analysis further explains the slackness-dependent force reduction mechanism. The results demonstrate that incorporating bending stiffness and optimizing slackness are critical for accurately predicting and mitigating seismic responses. A 10% slackness is recommended to improve the seismic resilience of substation outgoing line systems.