The abnormal mechanical operation of the vacuum circuit breakers in C-GIS (cubicle type gas insulated switchgear) at 40.5 kV occurs occasionally under low temperature conditions. Thus

it is an urgent need to improve the mechanical operation reliability under low temperature. The influencing factors of the mechanical operating performance of the vacuum circuit breaker under low temperature environment are deeply analyzed

and the mechanical operating performance under low temperature is studied through experimental methods. The test results indicate that ①The viscosity resistance of the lubricating grease is the main factor affecting the abnormal operation of vacuum circuit breakers under low temperature. ②The special low temperature lubricating grease can assure the normal operation of transmission chain kinematic pair in vacuum circuit breakers for environment temperatures as low as -30 ℃. The optimization of the transmission chain kinematic pair in the vacuum circuit breaker and the low-temperature lubricating grease selection can improve stability and reliability of vacuum circuit breakers mechanical operation.