PURPOSE: To enable the monitoring of vacuum free from effecting influence on shut down performance by the start of discharge within a discharge tube, by connecting a discharge tube which starts a discharge at a higher vacuum than that within a vacuum interrupter to the vacuum interrupter with a communicating member.
CONSTITUTION: One end of a discharge tube 1 is mounted to an upper end plate 22 of a vacuum interrupter VI through a pipe 2 so that internal pressure of the tube 1 will be the same that of the interrupter VI under a static condition. As the tube 1 is connected to the end plate 22 of the interrupter VI with the pipe 2, the potential of a pipe side end plate 12 of the tube 1 and the electrode 14 is the same as that on the high voltage size of the interrupter VI. In addition, the distance between the electrodes 14 and 15 in the tube 1 is set smaller than any vacuum gap within the interrupter VI. Therefore, when the vacuum of the tube 1 lowers, a discharge starts between the electrodes 14 and 15 to allow a discharge current to flow through circuit elements Z1 and Z2 and a specified voltage develops at a midpoint in the elements Z1 and Z2. A drop is vacuum of the interrupter VI can be detected by checking these voltages with a vacuum monitoring circuit.
YANAGISAWA HIFUMI
KAMATA SEIICHI
HIRAOKA JIYOUSUKE
