Abstract
We developed a multifunctional vacuum interrupter that has three functions: current interruption, disconnection, and earth operation in a vacuum vessel. Using the multifunctional vacuum interrupter, we realized 24 kV, 630 A, 25 kA rated switchgear that do not use SF6 gas. In addition, we could downsize the switchgear greatly compared with conventional switchgear by applying excellent vacuum insulation characteristics. In this paper, we report the backgrounds and the solutions of the following technical problems regarding vacuum insulation inside the multifunctional vacuum interrupter: (1) Improvement of breakdown voltage between the vacuum vessel and high voltage flexible conductors, (2) optimization on the shape of shielding electrodes set at both ends of an insulating rod, (3) removal of conductive micro particles and improvement of breakdown voltage between contacts by using AC working voltage, and (4) identification of long-term reliability of vacuum insulation under the continuous application of AC working voltage.
