Abstract
Energy released by electric arc during short-circuit current interruption is mostly absorbed by the surrounding cold gas and partly transferred to the arcing contacts and nozzle. The radiation is the main mode of thermal energy transfer between the electric arc and nozzle surface. Experimental research on the nozzle ablation has been carried out at a model circuit breaker, in which CO2 is filled in the chamber and poly-tetrafluoro-ethylene (PTFE) is used as the nozzle material. It is found that the arc voltage can be as an indicator of nozzle ablation degradation by comparing the voltage at current peak and arc voltage extinction peak. Under 20kA and 35kA peak current interrupting conditions, the voltage at current peak decreases with the number of operations. There are two factors that affect the arc voltage at current peak. One is the size of the arc cross section, and the other is the content of PTFE entering the arc zone, which affects its conductivity.
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