A"I"shaped conductor is set up in the A phase and the B phase in three phase enclosed GIS structure

the GIS temperature-rise experiment under different current is carried out by simulating the overheating defectscaused by the bad contact of the internal conductor of GIS. In the experiments

thermosensitive sensors and infraredthermometry are respectively adopted to detect the temperature of inner conductor and shell. It is concluded that

thetemperature of inner conductor and shell under A phase overheating defects is higher than B phase overheating de-fects. The temperature-rise of the inner conductor and the shell changes along the axial direction and the tendency torise first and then decrease

the maximum temperature-rise at the simulated defect. By analyzing the relationship be-tween inner conductor and shell

the temperature-rise difference ratio of inner conductor to shell is constant. The ac-tual temperature-rise of the conductor at the defect can be calculated by the shell temperature

the temperature-riseof the normal conductor and the temperature-rise difference ratio. According to the allowable temperature-rise of theconductor

the assessment for GIS internal overheating defects severity is achieved.