Abstract:Conductive circuit resistance of circuit breaker is an important index to monitor the status of circuit breaker and check the quality of circuit breaker installation and maintenance,there are many reasons for the excess.And there are different treatment methods for excessive resistance on the conductive circuit caused by different reasons.In this article, a fault of excessive resistance of 5021 circuit breaker in 500kV Dushan substation is introduced,and using the method of section testing to locate specific areas of excess,it is found that increased resistance of flange connection surface result in increased resistance of the total conductive loop.By returning to the factory for inspection,it is found that slight oxidation of flange connection surface result in increased resistance of flange connection surface.Calculating the relationship between the circuit resistance and temperature rise of flange connection surface by Newton''s formula for heat dissipation,as long as the actual contact resistance of flange connection surface does not exceed the specified value, the increase of temperature rise caused by partial slight oxidation will not affect the normal operation of circuit breaker.Therefore,for the fault of excessive resistance in the conductive loop of 500kV circuit breaker,it is necessary to adopt section test method to locate specific areas of excess,and for the excessive resistance of the conductive circuit in different parts,corresponding treatment measures should be taken to ensure the safe and stable operation of circuit breaker.