*2.5. Arc Ignition*

To initiate the arc in the most of the other researches, a predefined conducting column, usually rectangular with a temperature between 7000 and 10,000 K, is assumed between two contacts, which has the role of a thin melting wire in practical experiments [71,76,80], but it causes the shape of the arc and its movement to be unrealistic during the initial arcing period. As an accurate arc shape and therefore *Varc* in the first 200 μs is necessary for current commutation purposes, a di fferent approach has been taken here. The initial air conductivity is assumed to be 1 s/m wherever its conductivity is less than 1 s/m. By taking this approach along with electron emission from contacts, the arc starts from the sharp points and with an accurate initial shape. Then, the arc region can be determined using the σ distribution.

### *2.6. Turbulent vs. Laminar*
