Improved seismic risk evaluation for high‐voltage switchgear equipment: A copula‐based framework considering joint failure modes

Traditional seismic evaluations for high‐voltage switchgear equipment, the critical power facilities, consider only structural failure mode and may underestimate the actual seismic risk. By additionally introducing a probable functional failure mode caused by the excessive deformation of the switchable blade of equipment, a novel copula‐based framework is proposed to utilize limited samples to generate simulation data and evaluate the joint failure probability (JFP). The correlation index and Akaike Information Criterion are employed to optimize the Copula function. For illustration, a disconnector, representative switchgear equipment, was selected as an example and modeled with the experiment validation. Model analysis results demonstrate the Clayton type is the most competent for evaluation. Neglecting functional failure can significantly underestimate the actual failure probability at various seismic intensities, up to 50%. Furthermore, it was found that the current equipment material strength level already meets the requirements, and enhancing strength alone does not effectively improve reliability under strong earthquakes. For PGA intensities ≥0.7 g, the blade deformation capacity plays the primary reliability constraint, independent of material stress. A cost‐effective seismic design should optimize the combination of allowable material stress and blade deformation based on the JFP considering seismic intensity and targeted reliability.