Abstract: In order to solve the problem that the headlights of the high-speed EMUs( Electric Multiple Units) can
not be restarted during the driving，the faults are locked in the 110 V bus system and the network control system
activates the circuit breaker after removing the influence of the high-voltage power supply line，380 V bus and
load side． Using computer control，frequency conversion voltage regulation，sensor measurement and other
technologies，combined with host computer control，a set of test systems is built． After verification，the system
can quickly find out the source of the fault．

Key words: circuit breaker, fault, detection, transient voltage suppressor ( TVS)