Simulation And Experimental Research On The Characteristics Of Magnetic Arc Blow In Double-break Vacuum Circuit Breakers

With the rapid development of China’s power system,the improvement of the power grid voltage capacity has put greater challenges on the safety and reliability of high-voltage electrical equipment.In the field of high voltage circuit breakers,SF₆ circuit breakers have been restricted in use because of the environmental hazards of SF₆ gas.Double-break vacuum circuit breaker has the advantage of strong arc extinguishing and insulation ability due to its short vacuum gap in series,VCBs has become a hot topic at home and abroad.Since the characteristics of vacuum arc play a key role in the performance of vacuum circuit breakers（VCBs）,it is critical to study the characteristics analysis of the series arc in double-break vacuum circuit breakers.When double-break vacuum circuit breakers interrupt the fault current,the series arc will generate their individual magnetic fields in different breaks.The magnetic field in one break will influence the other arc in another break if the magnetic field is strong enough or the two breaks are too close.In this case,the interactive magnetic field effect happens.Through the analysis of the magnetic field between the double-break VCBs,it is found that the magnetic field of the double-break VCBs deflects from the center of the contact,that is,there is the effect of the bias magnetic field（BMF）.BMF can cause magnetic arc blow,and cause anode erosion on the surface contact and affect the breaking performance.Based on this paper,the results are helpful for the design of compact double-break VCBs.The article firstly introduces the influence mechanism of magnetic arc blow under BMF.Combine with the vacuum arc characteristics,the mechanism of vacuum arc under the axial magnetic field contact and transverse magnetic field contact has been analyzed.Furthermore,the action mechanism of TMF and diffusion vacuum arc and column vacuum arc has been analyzed.Theoretical analysis shows that when TMF acts on diffusion vacuum arc,vacuum arc plasma mainly acts as Hall electric field,and when TMF acts on arc column vacuum arc,vacuum arc plasma is mainly affected by Ampere force.The simulation part uses Ansoft Maxwell software for electromagnetic field simulation.Firstly,the distribution of magnetic fields under different contact structures were analyzed,then established the models of double-break VCBs with different configuration.The distribution of bias magnetic field at different vacuum chamber distances has been analyzed.Based on the distribution of BMF and the optimal configuration of the double-break VCBs is U-type.Finally,the shielding measures were applied to the double-breaker VCBs.The magnetic field distribution of the double-breaker VCBs under the shield was obtained and then compared with the results of the magnetic field without shielding measures.The simulation results show that the magnetic field distribution of the double-break VCBs in the magnetic shield is uniform;the magnetic shield has magnetic shielding effect.Based on the simulated bias magnetic field data,in the magnetic arc blow experiments the interaction between the series vacuum arcs in double-break VCBs was equivalent to the interaction between the single vacuum arc and the magnetic field generated by a Helmholtz coil.The high-speed CMOS camera was utilized to shoot the trajectory of the vacuum arc plasma under different BMFs with different types of contacts.The results show the BMF can increase the arc voltage and the arc becomes unstable.When the BMF becomes stronger,the arc voltage increases,the arc becomes more unstable.In addition,for different types of contacts,the development process of the arc and the influence level are different under the same BMF.For the Wan-type TMF contact or strong BMF,metal sputtering is evident,and anode erosion is serious.For the Cup-type AMF contact,the influence of BMF on the series arc plasma in double-break VCBs is less than the Wan-type TMF contact.