Comparison of Arc Motion in Lifetime Sealed Vacuum Interrupters with Different Bottle Geometries

Abstract

Vacuum circuit breakers are well established in the distribution levels of the electrical power grids. To maximise short-circuit interruption performance, an RMF-contact design forces the arc from a fault current to rotate. The performance of the RMF-contact designs is usually evaluated in a model vacuum chamber with viewing ports that allow observing arc rotation with the help of high-speed cameras. These setups differ significantly from lifetime sealed vacuum bottles in geometry (and thus volume) and due to the fact that the main metallic vapour shield cannot be present. This in turn can affect the arc rotation behaviour. In order to overcome these shortcomings, a new diagnostic tool has been developed to analyse the arcing behaviour in standard lifetime sealed vacuum interrupters. Optical methods are not possible here, since the view is blocked by the opaque ceramics and the metallic vapour shield. For this reason, a Hall-sensor based measuring system is applied, with that the variation in magnetic field from the arc position is observed by multiple sensors. This paper presents the comparison of arc motion in lifetime sealed vacuum interrupters with different bottle geometries. For this purpose, an investigation with identical spiral shaped RMF-contacts inside different vacuum bottle designs with differing vacuum volumes is performed. Similarities and differences between the corresponding arc motion behaviours will be discussed.