Mechanical defect is one of the common defects of GIS equipment during operation. Research on the mechanism of abnormal vibration of GIS due to mechanical defect is performed

which can effectively troubleshoot hidden troubles of the equipment at site. The finite element modeling is set up firstly in this paper to simulate the looseness of the shield which may occur during the operation of a 126 kV three-phase enclosed GIS and explore the mechanism and characteristics of abnormal vibration under defective conditions. Secondly

the normal model of the GIS and the looseness model of the shield are subjected to magnetic-solid coupling simulation respectively

and the vibration result on the enclosure is obtained through post-processing. Finally

a GIS test platform of the same model is set up to perform the defect simulation test

and the vibration signals of GIS under the same defect condition is subjected to detection and analysis. The results show that

in case of the looseness defect of the shield inside the 126 kV GIS analyzed in this paper

the main frequency will be shifted and the characteristic frequency at 300 Hz will be increased significantly. The simulation results is in good agreement with the experiment results. The study results in this paper can be used for abnormality judgment of GIS vibration signals in the case of shield looseness of GIS

and the analysis method combining numerical simulation and experiment can also provide a new perspective for studying many defect types.