Using accurate gas state parameters is the key for the calculation of flow characteristic in the arcing chamber

and it is important for optimization design of a SF6 circuit breaker. We jointly solved the real gas Redlich-Kwong equation and the flow control equation

set up a nonequilibrium energy dynamic arc model on the basis of Leslie S. Frost enthalpy flow arc model and the microscopic parameters of plasma arc

and investigated the cold and hot flow fields in the arc quenching chamber for the 40.5 kV SF

6

capacitor circuit breaker. Meanwhile

we obtained the distributi

ons of pressure

density and temperature under the conditions of unload and capacitive small current break. Moreover

we analyzed the circuit breaker pressure characteristics in the process of opening circuit

and obtained the dielectric recovery characteristic curve between arc contact after arc extinguishing by coupling calculation of electric and flow field. The results show that the calculation error of Redlich-Kwong state equation can be as low as 2.11%. Compared with the ideal gas state equation

calculation with the Redlich-Kwong state equation has the higher accuracy. The larger the velocity is

the more the gas state equation influences the gas pressure. The gas pressure in real gas state equation is higher than that in the ideal gas. When the open distance of the circuit breaker is more than 7 mm

the decline of maximum electric field strength tends to be slow. When the circuit breaker current is small

if the open circuit phase angle is respectively 1/10π

1/5π

3/10π

1/5π

1/2π

the corresponding arc duration is 0.6 ms

0.73 ms

1.8 ms

2.9 ms and 3.7 ms

which shows that the arc can be extinguished in advance. After arc extinguishing

the breakdown voltage is always higher than transient recovery voltage

so the circuit arc can be successfully cut-off. In order to obtain higher breakdown margin

the breaking phase angle should be higher than 1/5π.