Visualization of late breakdown in vacuum by ICCD camera

Experimental observations of late breakdowns in a vacuum circuit breaker were made using an intensified charge coupled device camera (ICCD). These late restrikes can cause arc reignition and interruption failure. This type of failure is rare and can be initiated by a number of mechanisms. This paper illustrates the method used to observe this phenomenon. Some key image examples of the phenomenon occurring during breakdown initiation are shown.