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<p>Support-type tubular busbar structures widely used in substations are inherently vulnerable to earthquake-induced damage. This study experimentally characterizes the load-resisting behavior and deformation mechanisms of post insulators under quasi-static cyclic loading representative of 220&#xa0;kV substation conditions. Quasi-static test results revealed that the porcelain body responded almost elastically, whereas localized plastic deformation developed at the porcelain-to-cast-iron-sleeve interface. The effective viscous damping ratio of the post insulator remained below 1.5%, indicating limited energy dissipation capacity within each loading–unloading cycle. A progressive increase in the top horizontal displacement induced pronounced stiffness degradation in the post insulator. Relative to the initial elastic value, the secant lateral stiffness decreased by 48% at a top displacement of 50&#xa0;mm and by 67% at 100&#xa0;mm. Building upon these observations, a composite cantilever-beam model incorporating stiffness degradation was proposed to represent the dynamic response of post insulators, and the associated dynamic equilibrium equation was formulated. Incorporating plastic deformation at the porcelain–sleeve interface into seismic design calculations increases the required flexural strength of electrical equipment by approximately 10–12%, thereby markedly improving its seismic resilience.</p>

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A degraded cantilever model for post insulators under cyclic loading

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年5月29日

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  • Qilin Sun,
  • Guanglin Yuan,
  • Xinghui Wu

摘要

Support-type tubular busbar structures widely used in substations are inherently vulnerable to earthquake-induced damage. This study experimentally characterizes the load-resisting behavior and deformation mechanisms of post insulators under quasi-static cyclic loading representative of 220 kV substation conditions. Quasi-static test results revealed that the porcelain body responded almost elastically, whereas localized plastic deformation developed at the porcelain-to-cast-iron-sleeve interface. The effective viscous damping ratio of the post insulator remained below 1.5%, indicating limited energy dissipation capacity within each loading–unloading cycle. A progressive increase in the top horizontal displacement induced pronounced stiffness degradation in the post insulator. Relative to the initial elastic value, the secant lateral stiffness decreased by 48% at a top displacement of 50 mm and by 67% at 100 mm. Building upon these observations, a composite cantilever-beam model incorporating stiffness degradation was proposed to represent the dynamic response of post insulators, and the associated dynamic equilibrium equation was formulated. Incorporating plastic deformation at the porcelain–sleeve interface into seismic design calculations increases the required flexural strength of electrical equipment by approximately 10–12%, thereby markedly improving its seismic resilience.