A hydraulic mechanism frequent bulge of a high-voltage circuit breaker occurred in a substation of the Northwest Power Grid.After disassembling analysis and checking components

this paper finds that the first sealing ring is damaged

which caused control valve leaking oil.Besides

the oil pressure switch has internal leakage

which caused frequent bulge

and the damage of the oil tank shockproof container intensified this situation.Considering components motion and manufacturing techniques

there are four points causing the leakage of the hydraulic oil.The first

the valve seat of the control valve has a small hole with a different axis from the chamfering angle

causing uneven force on both sides

so the seal ring is partially deformed.The second

the contact surface of the energy storage piston and the piston cylinder is too rough

resulting in impurities in friction.The third

the mating dimensions of piston

guide bar and spring seat are ground improperly.The last

the valve port or steel ball of the shockproof container is likely to damage during the assembly.In addition

the paper lists the causes of frequent bulge about common circuit breaker hydraulic mechanisms.Finally

the paper puts forward suggestions and improvement measures from three aspects of equipment inspection

manufacturing techniques and structure optimization.