| 摘要 |
<p>Detection of vacuum degradation in vacuum circuit breakers has been low in detection sensitivity owing to the presence of various noises besides electric discharge. Accurate detection of vacuum degradation is made possible by detecting the continuity of electric discharge occurring between the electrode and the shield as vacuum degrades, and the duration of electric discharge. It is arranged that the continuity of electric discharge is detected as a somewhat longer period of time than one cycle time of power source frequency and the duration of electric discharge is detected as a sufficiently longer period of time than one cycle time.</p> |
