Diagnostic of Arc Root Motion inside Hollow Electrodes in a Thermal-Expansion Circuit-Breaker

Abstract

In the studied auto-expansion circuit-breaker, about one millisecond before current zero, the arc centers itself on the axis of the system and gets longer because of the gas flowing from the upstream to the dowstream volume. The imagined solution to determine the arc root position inside the hollow electrodes, consists in embedding small Rogowski coils within the electrode material, close to the inner surface. Experimental results showed that sometimes the arc stretches out, then gets shorter suddenly, then gets longer again. But, if the arc is centered during a minimum critical duration, it remains permanently centered until current zero.