Abstract: At present, there are few studies on the interaction mechanism between the support system and the shell of GIS equipment in operation.Focusing on the support bracket deviation observed during the operation of a 500 kV long busbar system, this paper systematically investigates the effects of foundation settlement, sliding support clamps, fixed support bolts, and washer materials on the equipment''s thermal compensation system. Based on the busbar equipment of this substation, a thermal-mechanical coupling simulation model was established using ANSYS Workbench. The model revealed the coupled failure mechanism where the locking of sliding supports leads to temperature compensation failure, subsequently causing the loosening of fixed supports. Based on this, a comprehensive management plan was proposed considering the foundation settlement conditions of the substation. The improved structure was validated by simulation, showing a significant reduction in stress levels.The research results provide systematic analysis methods and engineering practice references for the design, construction, and safe operation of high-voltage long busbar equipment.