Research on the influence of the DC component of short-circuit current on arc dynamic characteristics during the arcing period

Based on the MHD (magnetohydrodynamic) equations, a 2-D dynamic mathematical model of nozzle arc considering the nozzle ablation is established in this paper, in which the interactions of the arc, the gas flow and the electromagnetic field are emphasized. A CFD software is used to simulate the process of interrupting the symmetrical and asymmetrical short-circuit current of a high voltage SF6 self-expansion circuit breaker, respectively. The dynamic characteristics of the nozzle arc as well as the pressure characteristics in the expansion chamber in the two cases are analysed and compared, more specifically, including the temperature and the pressure of arc at the current peak and at the current zero. Therefore, the interactions and influence between the DC component of the short-circuit current and the dynamic characteristics of arc during the arcing period are analyzed. The results show that the DC component of the short-circuit current increases the energy of the arc and raises the pressure of the expansion chamber; and it increases significantly the temperature, the pressure and the radius of arc at the current peak and the current zero.