601 / 2017-05-15 15:32:19

Influence of arc quench medium on the arc decaying behaviour in the circuit breaker by non-chemically equilibrium calculation

arc decaying,, non-chemically equilibrium, ,arc quench,chemical reaction

In the circuit breaker, the arc plasma will be generated when the two electrodes are separated from each other. Usually the investigation on the arc plasma can be divided into two phases: the arc burning phase and the arc decaying phase. To investigate the arc behavior numerically, the Magneto-Hydrodynamic (MHD) method is widely adopted, which couples the calculation of fluid dynamics with the electromagnetic field. During the arc burning phase, the local thermally equilibrium (LTE) hypothesis was commonly used, in which one of the assumptions is that all the chemical reactions reach the equilibrium. However, during the arc decaying phase, since the temperature keeps decreasing and so do all the reaction rates, the LTE hypothesis is no longer consistent during this period. In our previous work, a numerical non-chemically equilibrium (non-CE) model for the arc decaying phase was established and the validity was con-firmed by the experiment. In this work, we focused on the arc decaying behaviors by this non-CE model in various gases (N2, O2 and air), the arc behaviors obtained by the LTE model are also presented for comparison.

In the previous researches, thermodynamic and transport properties were considered to have the crucial influence on the arc behavior. However, from the non-chemically equilibrium calculation, it was found out that the reaction pathway and the reaction rate has more important influence. For example, although the properties of air and N2 are similar, but such kind of reactions in air, N+O+O→NO+O, will greatly accelerate the reaction process, leading to the great difference of arc behaviors between air and N2.