Seismic fragility analysis of multi-line transmission structure based on gas-insulated switchgear (GIS) equipment for nuclear power applications

The stable transmission of nuclear-generated electricity is vital for grid reliability and reactor external power supply. This study addresses this critical need by developing Finite Element Models (FEMs) of Gas-Insulated Switchgear (GIS) and a representative multi-line transmission structure to rigorously assess their seismic vulnerability through dynamic analysis and response evaluation. Based on the practical configurations of key substations system-level seismic fragility curves are constructed by integrating the failure probabilities of individual lines. The results indicate that, under identical structural dimensions, tapered bushings demonstrate superior seismic performance compared to uniform-section bushings. Furthermore, the maximum stress at spherical pipe joints is approximately three times that at right-angle joints, highlighting a critical structural vulnerability. Crucially, while a single transmission line is prone to failure under a given seismic excitation, increasing the number of parallel lines significantly enhances the seismic resilience and operational stability of the overall transmission system.