To address the recurrent issue of SF6 leakage caused by the cracking of epoxy resin terminal plates in gas-insulated switchgear(GIS)current transformers during high-temperature periods at a certain location

this paper analyzes the evolution of GIS shell displacement during sustained high temperatures

using a terminal plate cracking failure case as an example. Through technical means such as macroscopic inspection

spacing measurement

CT scanning

density measurement

and specific heat analysis

combined with influencing factors including assembly flatness

sustained high temperatures

and material properties

the causes of the failure are investigated from multiple perspectives. Testing on the failed samples shows that there is no abnormality in the terminal plate material quality. The failure mode involves cracks propagating symmetrically downward from the upper-left position-where the stress is most complex after tightening-under bending stress. The main cause of the failure is the uneven installation of the terminal plate inside the junction box

which subjects it to prolonged shear stress. Sustained high temperatures cause axial displacement and end rotation of the GIS shell. During heating

the displacement force converges at the top of the junction box outer shell

resulting in excessive pressure and significant stress concentration. In addition

the outdoor high-temperature environment degrades the polymerization rate of the epoxy resin molecular chain

gradually increasing brittleness. When local stress exceeds the allowable stress

a through-thickness crack is eventually induced.