With the effect of manufacturing technology

assembly process

operating environment and other factors

the gas insulated switchgear（GIS）in operation may appear such faults as SF

6

gas leakage

partial discharge and abnormal noise of gas compartment during the operation period. In this paper

the abnormal leakage of SF

6

gas in the bushing of one 500 kV hybrid gas insulated switchgear（HGIS）is introduced in detail. It is judged by disassembly inspection and composition analysis that the leakage is due to excessive application of silicone grease on the sealing ring

which overflows the sealing groove and produces chemical reaction with air and aluminum sheet during the long term operation period and causes sealing deteriora

tion. Such reasonable suggestions as double-layer sealing and enhancement of process management and control for such type of bushing are proposed. The rainproof cap and waterproof shed for the same lot of other types of bushings are added so to prevent the occurrence of similar phenomena. It can provide reference for gas leakage analysis

prevention and treatment for bushing of HGIS equipment.