This paper reports an abnormal reclosing event of the high-voltage circuit breaker equipped with hydraulic operating mechanism.The action of the line protection device and the background message were analyzed on site

and the microswitch pressure setting value of the operating mechanism was checked.As a result

this event was found to be due to that the adjusting screw of the low-oil pressure closing lock contact was squeezed off the axis to cause higher setting value of closing lock oil pressure

and after the circuit breaker was opened the oil pressure of the mechanism was lower than the setting value of closing lock oil pressure

which led to the failure of reclosing.A resulting treatment scheme was proposed

and multiple tests on site verified the effectiveness of the scheme.