A simplified turbulent arc model for the current-zero period of a SF6 gas-blast circuit breaker

A simplified model for the current-zero period of an are buming in a SF6 gas-blast circuit breaker is developed on the basis of the boundary layer integral method. The shape factors needed to complete the model are determined before the current zero using the well-established correlation parameter method. The shape factors and correlation parameter are determined using numerical solutions of the are governing equations in full differential form (the differential method). Similarity theory based on the differential method is used as a guide in determining a suitable correlation parameter. After the current zero an extra semi-empirical equation is added to model the competing processes of ohmic heating and turbulence-enhanced thermal conduction. The resulting model contains a single free parameter associated with the turbulence and when this is set appropriately the complete set of experimental results given by Frind and Rich [1] is successfully predicted.