Research On Early Fault Diagnosis Technology Of Circuit Breaker

Frequent opening and closing operations of high-voltage circuit breakers can easily cause contact wear and deterioration of mechanical transmission mechanism,the contact surface will be damaged and the opening and closing time will be delayed.In addition,the abnormal pressure of the arc extinguishing medium（SF₆ leakage,abnormal vacuum）will also affect the arc extinguishing performance of the circuit breaker.In severe cases,the circuit breaker will fail to operate and may even cause a breakdown and explosion.In view of this problem,this paper has carried out research on early detection technology of HV circuit breakers’health status and detection technology of arc extinguishing ability.Specific work and innovation points are as follows:1)Find a characteristic quantity that can be used to describe the contact wear and the abnormality of the mechanical transmission mechanism.The critical breakdown field strength and contact spacing are analyzed as the limitations of the characteristic quantities that characterize the contact wear of the circuit breaker and the abnormal characteristics of the mechanical transmission mechanism.In order to extract new characteristic quantities,the dynamic closing process of the circuit breaker and the cause of the arc are analyzed.A breakdown current model was established,and a technical scheme was designed to use the breakdown current value instead of the critical breakdown field strength and contact spacing to comprehensively characterize the health status of the circuit breaker.Based on the actual arcing fault current waveform,the breakdown current model was constructed.Comparing the simulation results with the measured data,it is found that the breakdown current model established in this paper can better model the actual arcing fault,and the accuracy of the model is verified by changing the contact spacing and the critical breakdown field strength value.2)Early fault detection algorithm for monitoring the electrical quantity of circuit breaker closing.Analysis of existing detection method based on electric parameters by a priori assumptions limits and measurement methods are susceptible to interference can cause misjudgment,in response to this problem,the possible degradation state of the breakdown current sequence is analyzed from a physical point of view,the fitting method is used to determine whether the circuit breaker has contact wear or the abnormality of the mechanical transmission mechanism according to whether the sequence has a monotonic trend.Then,an early detection method of abnormal health status of the circuit breaker based on the sequence of different breakdown current ratios is proposed to judge the contact.Whether the head wear and mechanical abnormality have reached the serious level.The influence of zero-degree closing phase and closing phase deviation on the proposed detection method is analyzed,a large number of simulations and actual field record data are used to verify its effectiveness.3)Aiming at the shortcoming that the early detection method of health status cannot determine whether the pressure of the arc extinguishing medium is abnormal,the arc extinguishing capability detection is carried out.In this paper,the angle is changed,and the traditional method of characterizing the arc extinguishing ability of a circuit breaker by the pressure of the arc extinguishing medium is transformed into the exploration of the characteristic relationship between the arc extinguishing ability and the electrical quantity.Based on the arc extinguishing principle of arc gap energy balance,the arc extinguishing ability is inverted by the influence of arc resistance on the attenuation characteristics of arc current when the medium is restored,and an online detection method of arc extinguishing ability of circuit breakers was proposed.In summary,the early detection method of abnormal health status of the circuit breaker with the characteristic of the breakdown current sequence is used to judge whether the contact wear and the mechanical transmission mechanism are abnormal in this paper,and the detection method of the arc extinguishing ability with the arc current trend item as the characteristic quantity is used to judge its arc extinguishing whether the medium pressure is abnormal,two detection methods are used to finally determine whether the circuit breaker has an early abnormality.