The method for fault line selection based on pulse current must change grounding mode of neutral point in short period. The negative effects on extinction of fault arc are produced by the change of grounding mode. According to the extinction conditions of fault arc, recovery voltage of fault point has been researched. Results show voltage recovery rate may become fast and the probability of arc re-striking may be increased because of the change of grounding mode. To avoid the negative effects produced by method for fault line selection based on pulse current, the time ranges suitable for changing grounding mode and its computing method are proposed. In addition, the negative influences on fault arc can also be reduced by adding current limiting residence.