Vapor shield potential in vacuum interrupters after clearing of short circuits

Measurements have revealed that, after a short circuit is cleared, the potential of an isolated vapor shield in a vacuum interrupter is initially coupled with the contact, which is the anode after current zero. This due to the fact that the residual plasma between the anode and shield first has to be depleted during that initial period. The duration of that coupling depends upon the arc current, the arcing time, and the interrupter geometry. Experiments using a shield with additional external circuitry make it possible to determine the number of charge carriers that have to be depleted at current zero. Shield potential measurement can be used, therefore, in the development of vacuum interrupters to facilitate the evaluation of a contact material or a contact configuration