The stochastic breakdown model proposed by Niemeyer et al. has been im
proved by taking the time evolution into account in the two-dimensiona
l lattice system. A Markov process has been assumed in the breakdown p
rocess and 'time' has been defined reflecting the distribution of brok
en bonds in the cluster. The change of breakdown patterns with time pr
edicts various aspects of breakdown phenomena. We have shown that the
final breakdown path does not always form a straight line. We have pro
posed one of the possible origins. for the polarity problem and shown
that the polarity difference is understood by the relative position of
the damaged layer to the starting point of breakdown.