Under normal working conditions, the fixed and moving contacts are
closed. On the occurrence of fault, the moving contacts come down
and an arc is struck between the contacts. The oil between the
contacts gets decomposed and hydrogen gas bubble is formed
around the contacts. The hydrogen gas cools the arc and rthe
turbulence effect cause the lengthening of arc. The deionization of
medium between contacts takes place and at some critical length of
gap between the contacts ,the arc is extinguished.