Investigations of Nozzle Materials in SF6 Circuit Breakers

With a puffer and a self-blast type SF6 circuit breaker (CB), various nozzle materials have been investigated. In addition, a small-scaled model SF6 breaker has been attached to a time-of-flight mass spectrometer (TOFMS) in order to study the exhausted gas contaminated with ablated material. The experimental results clearly show an influence of the nozzle material on the interrupting capability of the SF6 CB. The observed nozzle ablation is mainly determined by the geometry of the arcing device. The erosion of the nozzle and the chemical composition of arced SF6 gas depend slightly on the quality of the PTFE nozzles only.