A slow-closing accident of 220 kV porcelain column circuit breaker was analyzed by means of on-site check

test

and disassembly inspection in the manufacturer. It was found that the fit tolerances are too small among the guide sleeve base

the guide sleeve and the guide rod of the circuit breaker

and the temperature compensation coefficients of the guide sleeve and guide rod are different due to their different materials. All these factors increased the closing resistance of the circuit breaker at high environmental temperature

and eventually leaded to this accident. In addition

countermeasures are suggested in this paper.