Abstract:In order to study the differences between coil current curve and stroke - time curve in fault diagnosis of circuit - breaker operating mechanism,based on the analysis of coil current characteristics of circuit - breaker operating mechanism and stroke - time characteristics of contacts,the influence of circuit - breaker operating mechanism failure on coil current and stroke - time characteristics is compared through testing the mechanical characteristics of circuit - breaker operating mechanism. Through comparative researches,it is found that the coil current curve is more sensitive and accurate than the stroke - time curve in terms of core pin,coil voltage resistance change,auxiliary contact arc extinguishing and spring fatigue failure. The research results have a certain reference significance in the selection of state evaluation method for circuit - breaker operating mechanism.