The Magnetic Control Of Vacuum Arc And Design Of A New Contact For DC Vacuum Circuit Breaker

Circuit breaker has dual functions of control and protection in power system.Vacuum circuit breaker has been widely concentrated and applied for its high security and reliability.When the vacuum circuit breaker breaks the fault current in the DC power system,the magnetic field generated by the contacts can control the arc,which is one of the basic ways to improve the performance.Based on the working conditions of mechanical DC vacuum circuit breaker,the magnetic field control method of vacuum arc is analyzed from two aspects of simulation and experiment.The contact structure and the current of the simulation and experiment are similar,and the results can be used to guide the contact design of DC vacuum interrupter.The finite element method is used to analyze the magnetic field of vacuum interrupter contacts.The typical models of spiral groove transverse magnetic contacts and cup-shaped axial magnetic contacts are established.The magnetic field distribution at the center plane of the arc gap under certain interruption current level is analyzed,and the characteristics of magnetic field control can be obtained.The effects of the shape of spiral groove,the diameter of the contacts,the radius of chamfer and the distance of the contacts on the magnetic field distribution in the contact gap are analyzed.In order to combine the merits of transverse and axial magnetic field control,a new design idea of hybrid magnetic contacts is proposed,and its three-dimensional model and prototype are established.The characteristics of magnetic field distribution of the new structure are analyzed,the arc trajectory is predicted,and the arc control advantages of the new contacts for DC circuit breakers are analyzed.An experimental platform of HVDC vacuum circuit breaker interruption based on active injection method is built.The experiments are carried out by using spiral groove transverse magnetic field contacts,cup-shaped axial magnetic field contacts and the new hybrid magnetic field contacts.The arc images are captured by CMOS high-speed camera and processed.By analyzing the arc images,comparing the arc motion and shape characteristics of three different contacts,the control characteristics and advantages of the new combined contacts can be summarized.It is preliminarily confirmed that the control mode of hybrid magnetic field control of vacuum arc in DC vacuum interrupter is feasible.