Recently

more and more attention has been drawn in fast dirty snow flashover occurred in power system.The differences between dirty snow flashover and pollution flashover are in two aspects:①fast-dirty-snow flashover mostly occurred in the heavily polluted region.②the pollution accumulation process and wetting process of fast-dirtysnow flashover are occurred at the same time.In order to analyze the influence of snow on the electric insulation performance of insulator string

the snow-covered 110 kV insulator strings are modeled and analyzed by finite element method.The analysis results indicate that snow covered on insulator surface could change the total electric potential distribution of insulator string.The electric potential withstand by wire side insulator and tower side insulator are increased significantly.When insulator surface is covered by heavy snow and dirty snow pillar is formed

the total electric field distribution along the string axis direction will be distorted significantly.The electric field strength of the air gap between the neighboring dirty snow pillars will be distorted and which is 27.5 times than that of the normal value.The creepage distance probably be reduced and the flashover channel between dirty snow pillar and air gap may be formed.