Improving Current-Interruption Performance by Using Spiral Electrode for SF6 Disconnecting Switch

To improve current-interruption performance, spiral electrodes were experimentally investigated to magnetically drive an arc. Arcing times for conventional plane electrodes and spiral electrodes were obtained from conducting current-interruption tests and compared. The comparison results indicate that the arcing time in spiral electrodes is about one-third shorter than that in plane electrodes when interruption current is above 900 A. To clarify the principle of improving interruption performance, arc parameters, electrode erosion, and rate of increase in transient recovery voltage were compared for both plane and spiral electrodes. These results revealed that the magnetically driven arc enhances thermal loss of the arc and heat exchange between the arc and ambient gases. Regarding the spiral electrodes, the recovery rate of dielectric strength between the contacts was high. It is thus concluded that current-interruption performance improves by cooling the arc and increasing the dielectric strength by the magnetically driven arc.