Study on the Drawn Vacuum Arc Characteristics of the 126 kV Axial Magnetic Field Contacts

During the current interruption process, the vacuum arc evolution characteristics are crucial in determining whether a vacuum circuit breaker can interrupt the current successfully. In order to analyze the expansion characteristics of cathode spots (CSs) on the 126 kV axial magnetic field (AMF) contacts, the drawn vacuum arc experiments were conducted. To observe more characteristics of the drawn vacuum arc, two high-speed cameras were used simultaneously to capture the dynamics of both the vacuum arc and CSs. The experimental results indicated that the vacuum arc column could not expand sufficiently to cover the entire contact surface. Additionally, multiple types of vacuum arc column modes occurred in the experiments, and the number of ignition positions also affected both the appearance of vacuum arc and the diffusion process of CSs. Moreover, the magnetic field distribution under different vacuum arc column modes was simulated. In the contact surface near the contact edge, the AMF components are smaller than the transverse magnetic field (TMF) components and these lead a rapid radial expansion of CSs. Furthermore, significant deflection occurs for CSs located in central area on both cup-type AMF contact and coil-type contacts. However, the CSs of these two types of contacts show different deflection directions. When the total arc area remains constant but the number of arc columns increases, the TMF components decreases and radial velocity of CSs also decrease. The simulation results also indicated that the variation in the number of arc columns has a relatively small impact on the distribution of the AMF component.