External Field Control for Vacuum Interrupter

Inhalt:
The need to replace SF6 as an external insulating gas for high and medium voltage systems increases the importance of the external dielectric of vacuum interrupters. This point is particularly important for vacuum interrupter, as the external design of the vacuum chamber results from the requirements of the chamber interior. This paper presents one option for external field control of the vacuum interrupter triple points. For this purpose, field control rings are used on an industrial vacuum chamber. In a simulation of the electric field, the modification by the field control rings at the triple points is examined. Various combinations of field control rings on vacuum interrupter with lightning impulse voltage are investigated for the design of a field control system. The resulting field control increases the electric strength of the VI by 18 % for both polarities. From high-speed camera data of flashovers, the changes in the flashover path through the field control are analysed and the results are used to discuss the flashover sequence. The use of field control rings changes the flashover mechanism from a straight surface streamer to a combination of streamer discharge and surface streamer.