Investigations on the conditioning of high-voltage vacuum interrupters

A high-voltage vacuum interrupter has a more complex design and geometry compared to medium voltage vacuum interrupters. Due to its larger dimensions, field control is necessary to avoid local dielectric overstress. This is implemented by segmented vapor shields. However, in this case the vacuum breakdown does not only occur between the contacts, but there are various possible breakdown spots, e.g., between vapor shields. In this work, for a deeper understanding of such a system, the conditioning process is investigated for specially prepared vacuum interrupter test samples containing vapor shield segments of different geometries. For large gap distances, as they are needed for high-voltage applications, the scatter of withstand voltages for samples of same geometry is observed to be large. The effects of conditioning and deconditioning can be greater than those of a geometrical parameter variation. Therefore, particularly for applications of high-voltage vacuum interrupters, it must be ensured that the conditioning of a sample has been finalized. It is important to avoid deconditioning during the conditioning process. For this contribution, it is investigated how the parameters of the conditioning test circuit affect the conditioning and deconditioning process. For optimized conditioning parameters, it is possible to reduce the time required for conditioning and to achieve high and reproducible withstand voltages.