The influence of PTFE vapour on the characteristics of nozzle arc is considered in the mathematical model of nozzle arc in this paper.The interruption of heavy short circuit current is simulated numerically by the finite element method in an SF 6 auto expansion circuit breaker. As compared with the interruption when PTFE vapour is ignored

the influence of PTFE vapour on the characteristics of nozzle arc is obtained.The results show that the PTFE vapour enhances the pressure of nozzle arc obviously

and reduces the temperature of arc during high current

increases the one during current zero

declines the one slower during arc current decreasing and increases the radius of arc

too.