The vulnerability of the mechanical clamped type bushing for 500 kV transformer is high under seismic action and the leakage of insulating oil of bushing is likely to occur. For studying the seismic performance of the mechanical clamped type bushing flange

a certain type of 500 kV mechanical clamped type bushings joint is adopted in this paper to perform quasi-static lateral push tests under three different loading conditions. The damage phenomena and mechanisms of the mechanical clamped type flange joint and the porcelain bushings under seismic action are studied. Through the decomposition of the top displacement and the derivation of the bending stiffness formula

the stiffness variation of the mechanical clamped type flange joint under seismic action is analyzed. The results show that the reciprocating vibration of the mechanical clamped type bushing under seismic action will cause the extrusion de-formation and displacement of the sealing ring at the root of the porcelain bushing and the damage phenomena of ceramic fracture. The tensile stress at the weak part of the hitch lug is relatively large

which is consistent with the damage phenomenon in the seismic damage. Based on the quasi-static lateral push test data and theoretical analysis

the bending stiffness empirical coefficient in the bending stiffness calculation formula of the mechanical clamped type flange joint of the 500 kV transformer is corrected.