Particle detection in vacuum interrupter after current interruption

After high current interruption in vacuum interrupter, the electrode temperature rises because of the current heat process, and the surface becomes rough due to the arc burn on electrodes. In this paper, random discharge after current zero is reported, and conducting particle is considered to be responsible for the phenomenon. The authors developed a synthetic experiment system, which is a combination of current and voltage sources. High voltage is applied to the interrupter after current interruption. The arc current can be adjusted up to 10kA and the voltage can reach as high as 50kV under AC condition. The particle detection optical system consists of a laser and a diffraction imaging system. A high speed video camera is used to record the diffraction image induced by the small particle in the inter-electrode space. Using this system, the dynamics of small particles is tracked. The speed and size of the particle is measured and the charge quantity of small particles is derived from the dynamics.