Quenching Processes of Axially Inhomogeneous Arcs in SF6 Circuit Breakers

The description of the arc in a modern high-voltage SF6 circuit breaker by only one single-arc equation is not sufficiently exact for application, especially when using constant arc parameters. In typical nozzle configurations, arcs are generally being axial inhomogeneous. For these arcs, a theory is presented taking into account the gas-flow properties determining the axial structure. This is applied for investigating an arc consisting essentially of two different parts. It is shown, how to determine for these parts the arc parameters depending on the conductances, which are required for an appropriate mathematical description. As an example a computer simulation of the performance of the investigated circuit breaker is presented, and compared with corresponding full-scale interruption tests. Breaking capacity limit as well as the complete interaction phenomena between circuit breaker and test circuit are in agreement, proving the presented theory of an axially inhomogeneous arc.