Influence of the Simulation Model on the Spatial Arc Resistance Distribution of an Axially Blown Switching Arc

Circuit breakers are important elements of the electric power supply system. Due to the contact separation during the switch-off process an electric arc is ignited within the circuit breaker. A forced flow of the insulating quenching gas medium is used to cool the arc influencing its conductivity. Only if the power dissipation due to cooling exceeds the electrical power input by ohmic heating, the arc is extinguished and the current is successfully interrupted in its natural zero crossing (CZ). As the impact of the cooling by the quenching gas on the resistance of the arc is considered crucial for the success of the switch-off process, the spatial distribution of the resistance is of high importance for the assessment of a circuit breakers performance. Research and development projects related to circuit breakers more and more often use computational fluid dynamics (CFD) simulations. The implemented simulation models have to be be verified by adequate experiments. This paper deals with the influence of the simulation model on the simulated spatial arc resistance distribution near current zero. Different approaches for modelling the chaotic and turbulent phenomena of the arc are introduced and their results are compared with values measured in experiments. Here the turbulence model is of main interest. On the one hand the investigations show a good agreement between simulative and experimental results for the total arcing voltage when using adequate models. On the other hand these turbulence models lead to differences in the calculated spatial arc resistance distributions – which cannot be verified by experiments so far.