In order to investigate the frequent pressurizing fault of the OM-3 hydraulic operating mechanism in 500 kV HGIS

the fuel tank was taken apart under the field high pressure condition

and the cause of the fault was analyzed according to the principle of the operating mechanism.The result showed that the seal failure of the closing first-level valve body created the internal high-pressure leakage.This failure was eliminated by replacing the closing valve body.In addition

all this type of the first-level valve bodies with long running time are suggested to be replaced.