Vacuum circuit breaker is one of the most important electric accessory in traction power supply control. Circuit Breaker ( CB) on-line monitoring plays an important role in the safety operation of the system. 真空断路器是牵引供电控制中最重要电气设备之一,真空断路器的在线监测对保障供电系统安全运行具有十分重要的意义。