Vacuum switch equipment (vacuum breaker, vacuum load switch, vacuum contactor, vacuum splitter, vacuum coincidence unit) has been widely used in various fields due to its advantages of small volume, light weight, high performance, high reliability, convenient maintenance and inspection, and suitable for frequent operation.

But vacuum arcing chamber of the vacuum switch arc is by evaporation from the contact of the neutral atoms in the metal vapor, ions and electrons, they provided by the contactor, quickly spread to the arcing chamber, after cooling attached on the surface of the arc shield contact, in current near zero and nature after current zero, the particles of rapid movement makes the vacuum switch device has a very high insulation resilience, but extremely steep river closure phenomenon has sprung up and high frequency arcing ability.This is an extremely important factor in the generation of overvoltage.In addition, since these particles are generated by contacts, the above properties will be largely affected by the material properties of contacts.

The above characteristics of the arc extinguishing chamber of vacuum switch equipment determine that it is easy to generate truncation, multiple reburning and three-phase synchronous overvoltage when the switch breaks various loads.

Operating over voltage is characterized by high frequency (can be as high as tens of KHZ, so the voltage rise is very steep) and high amplitude (can be as high as 7pu), which are extremely harmful to various electrical equipment running, and to a large extent affecting the stability, reliability and safety of the system.Therefore, the correct and reasonable selection of appropriate and ideal overvoltage protection device is of great significance.