Analysis of nozzle ablation characteristics of gas circuit breaker

Thermal puffer type gas circuit breakers have become a mainstream of high power circuit breaker, because they are compact in size and interrupt high current with low operating force. In this type, ablation gas of nozzle material flows back to a puffer chamber during nozzle clogging, and it increases puffer pressure. Namely, ablation gas plays an important role for puffer pressure build up. However, the nozzle ablation characteristics are not yet well known. In this paper, using a newly developed calculation program of nozzle ablation, we analyzed amount of nozzle ablation and ablation rate. As the results, it was found that nozzle ablation occurs by radiation energy of high temperature arc and ablation rate are greatly influenced by interrupting current. It was also found that they increase with the increase of DC component of interrupting current. The calculation results agree fairly well with experimental results.