Post-arc current of vacuum DC interruption

Post-arc current significantly influences the interrupting process of breakers, which can reflect the appearance of the arc before current zero and the residual metal vapors in electrode distance after current zero. In order to investigate the characteristics of post-arc current in DC interruption, a high speed hybrid actuator was designed, and forced current zero method was used to carry out the DC interrupting experiments in the synthetic test circuit. Also, the equipment for the measurement of post-arc current was established to study the factors influencing on the post-arc current, including the rated breaking current and electrode distance. The experimental results indicated that post-arc current presented the instability in a certain range, due to the different contact structures, arcing positions and so on. To some extent, post-arc current also reflects the sheath growth process after the current zero. Furthermore, the amplitude of post-arc current changes with the variation of electrode distances. And for the same distances, post-arc current keeps stable in a certain range. While the rated breaking current is lower than 800A, post-arc current increases with a high growth rate. And it is under a low growth rate and no sharply when the rated breaking current varies within 800A to 2000A. For the same electrode distances, post-arc current presents a significant increase with the increase of commutation frequency. It is for the reason that more residual metal vapors exist in the electrode distance after current zero for higher commutation frequency, which goes against for the DC interruption.