Three-station vacuum switch tube

The invention discloses a three-station vacuum switch tube comprising a vacuum chamber, a fixed contact assembly, a moving contact assembly and a grounding contact, wherein the grounding contact comprises a grounding contact ring and a grounding terminal, wherein the grounding terminal is electrically connected with the grounding contact ring, and a moving contact is driven by an operating mechanism to take linear back-and-forth movement between a fixed contact and the grounding contact ring; and when the moving contact, the fixed contact and the grounding contact ring are all in off states, the tolerance electric field intensity between the moving contact and the fixed contact is higher than that between the moving contact or the fixed contact and the grounding contact ring. The invention realizes the switch-on, isolation and grounding three-station functions, also not only has the advantages of compact structure, reasonable design, advanced technology, current relative standard accordance, long electrical life and mechanical life, wide application range, high safety and reliability, and the like, but also realizes that electric breakdown firstly generates between a loading terminal and a grounding terminal once vacuum degree is reduced, enables the leakage currents and the short-circuit currents to flow into earth and ensures the safety of maintenance personnel who possibly mistakenly contact the loading terminal.