SUMMARY When the contacts of circuit breaker are opened just before current zero, the gap between contacts will still be very short. Therefore, it cannot withstand recovery voltage between the contacts. In such a case, multiple reignition is likely to take place. Many investigators had tried to clarify this phenomenon, and many reports have been published. However, high‐frequency current interruption and dielectric recovery characteristics are related to some parameters (value of current, arc time, and so on). In addition, arc phenomenon has also been implicated. Hence, it is difficult to understand this phenomenon accurately. In this paper, we conducted dielectric recovery test and high‐frequency current interruption test. Further, we conducted observation experiment using vacuum chamber in order to investigate the effect of small dc current. At the end, we calculated plasma density in the electrodes after high‐frequency current interruption by considering the result of observation experiment and dielectric recovery test.

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When the contacts of circuit breaker are opened just before current zero, the gap between contacts will still be very short. Therefore, it cannot withstand recovery voltage between the contacts. In such a case, multiple re-ignition is likely to take place. Many investigators had tried clarify this phenomenon, and many reports have been published. However, high frequency current interruption and dielectric recovery characteristics are relates to some parameters (value of current, arc time etc). In addition, arc phenomenon also has been implicated. Hence, it is difficult to understand this phenomenon accurately. In this paper, we conducted dielectric recovery test and high frequency current interruption test. Further, we conducted observation experiment using vacuum chamber in order to investigate the effect of small DC current. At the end, we calculated plasma density in the electrodes after high frequency current interruption by considering the result of observation experiment and dielectric recovery test.

Usage of polymer materials in a quenching chamber is one of the most effective methods of improving performance of an air circuit breaker [1, 2]. During a high current interruption in the air circuit breaker, an arc discharge touches the insulator, and ablation gasses are emitted [3]. It is considered that the quenching performance and an arc characteristic are affected by this ablation gasses. In order to clarify the quenching performance of each polymer material, we are conducting the experiments. With these experiments, the relationships of the ablation gasses among the number of arcing cycles, arcing peak voltage, arcing conductances, and the pressure rise will be discussed with four kinds of polymer materials.