Physical principles and development of a new generation of SF6 circuit-breakers for 145 kV

The arc in conventional gas-blast circuit-breakers is merely a passive element to be quenched by a transonic gas flow of sufficient pressure. The latter is generated mechanically by rather simple means, but uneconomically from the modern point of view. The arc in a self-blast circuit breaker is an active element controlling the breaker action in a complicated manner all the time from contact separation to extinction at one of the subsequent current-zeros. For these reasons, the development of 3rd generation SF₆ switchgear requires high-level research activities including arc physics, flow dynamics, material sciences and mechanics. The theoretical modelling has pointed out to be a valuable tool to approach the final design sufficiently closely already before the series of switching tests are performed. Further steps of improvement require highly sophisticated computational fluid dynamics in order to obtain high-resolution spacetime patterns of the interesting physical quantities and to point out the influence of details of the design. The reward for these efforts is the new generation of high-technology switchgear which guarantees safe power distribution with minimum maintenance during long service life