Interaction of a Vacuum Arc with an SF6 Arc in a Hybrid Circuit Breaker during High-Current Interruption

A hybrid circuit breaker consists of a series connected vacuum- and SF6 interrupter. The vacuum interrupter has the function to withstand very steep rising transient recovery voltages, whereas the SF6 interrupter is stressed with the peak of this voltage. Full scale tests are described of a 145 kV prototype, subjected to short-line faults based on 63 kA. During these tests, current through the breaker and voltages across both interrupters were monitored with a high-resolution measurement system. It is shown that the principal idea works correctly. From measured results, it is demonstrated that the interaction between the two arcs of completely different physical nature has a positive effect on the interruption: immediately before current zero the SF6 arc assists the vacuum arc to interrupt, whereas after current zero the vacuum arc assists the SF6 arc in the withstand of the recovery voltage