Analysis of the plasma behaviour after current zero phase based on the post-arc current of a vacuum interrupter

The vacuum interrupters (VI) are an environmentally friendly alternative to circuit breakers based on sulphur hexafluoride (SF6). The aim is to replace the SF6 interrupters. During the interruption process of a VI a plasma consisting of metal vapour occurs. This plasma must be extinguished as fast as possible to recover the dielectric strength. Therefore, it is necessary to understand the plasma behaviour. The plasma can be described through the voltages and currents during the breaking process. In this paper an analysis of the post-arc current is carried out.The aim is to describe the phenomenon during the current zero crossing (CZC) like chopping current. Limits and appearances will be described by the current and voltage curves at CZC. Thereby, the circuit elements, which generate a circuit response will consider and with a circuit model will verify the plasma behaviour by the current curves. The measurements were taken in a synthetic test field, a Weil-Dobke circuit. High short-circuit current up to 15 kA rms, 50 Hz and transient recovery voltages (TRV) of 60 kV peak were carried out.