Research And Prediction Of Electric Life Of EMU Vacuum Circuit Breaker

Vacuum circuit breaker,as an important equipment in the power system,is a new type of circuit breaker that uses a vacuum environment with high dielectric strength as the arc-extinguishing medium.It is widely used in the field of EMUs due to its strong breaking capacity and good arc-extinguishing characteristics.Vacuum circuit breakers will generate arcs during the process of breaking the current,and the arcs will ablate metal materials on the contact surface and form conductive pollutants,resulting in changes in contact surface morphology and cumulative loss of materials,increasing the loss of electrical life.Therefore,it is of great significance to study and predict the electrical life of vacuum circuit breakers in this paper to improve the reliability and operating efficiency of the equipment.Aiming at the influence of the arcing time factor on the erosion of the contacts during the current breaking process of the vacuum circuit breaker.Based on the simulation module,this paper establishes an improved Mayr arc dynamic simulation model,and simulates and analyzes the voltage and current changes before and after the current zero point of the vacuum circuit breaker during the breaking process;it is concluded that the arcing time after multiple breaking times obeys the Gaussian normal distribution conclusion.Aiming at the wear and erosion problem of contacts under different breaking voltage and current conditions,this paper establishes a single contact breaking erosion model based on the electrical contact theory,and establishes a remaining electrical life performance degradation model based on the Wiener process,and draws the probability density function and reliability function curve.The results show that the reliability of the vacuum circuit breaker is 0.9 when it is opened about 5285 times;the reliability is reduced to 0.8 when it is opened about 7190times;The probability density of the vacuum circuit breaker in the initial state is the largest when it is opened 5280 times.In order to verify the accuracy and reliability of the obtained model,a vacuum circuit breaker prototype is made in this paper for breaking test.Measure and record the arc voltage,contact bounce times and time changes,contact resistance changes,and contact ablation quality changes during the contact breaking process,select the contact ablation amount to describe the performance degradation process,and simulate the remaining electrical life performance degradation model Comparing the calculated accumulative wear amount of the contact with the actual ablation amount of the contact measured during the breaking test,the relative error does not exceed 2.53%,and the error result meets the engineering requirements.