In gas insulated substation (GIS), very fast transient over-voltage (VFTO) is caused during the switching operation because of repeated arc reignition. At present only the first arc is considered for numerical simulation of VFTO, which can’t describe the character of VFTO exactly, because the time of arc reignition and extinction is difficult to determine. Base on arc dynamic energy equation, the paper confirms the decision condition of arc reignition and extinction, and gets VFTO wave and peak voltage of each node during arc reignition by simulating. Comparing to the two results, it could see that, for the same node, there was not great change in wave forms; the VFTO maximums both on mains side of switching, also this node’s peak voltage had the largest difference, base on the first arc peak voltage, approximately 10.78%, which should been attention to for insulation of apparatus.

GIS; Very fast transient over-voltage; Breakdown voltage of dielectrics; Arc reignition