Under the condition of snow

the electrical performance of polluted insulators will decrease obviously

even causing snow flashover. To study the effect of equal salt deposit density（ESDD）

snow thickness and shed geometry on the snow flashover voltage

we designed a test method of artificial snow covering

performed artificial contamination snow flashover tests of 4 kinds of 110 kV AC post insulators with different shed geometry

and analyzed the process of flashover. Research shows that conductivity of snow melting water per unit time will decrease in a snow melting progress. Arc discharge and flashover path often occurs where snow melts or falls off. The snow flashover voltage has a negative power function with ESDD

decreases and tends to saturation with the increase of ESDD. Compared that at snow thickness of 5 mm

10 mm and 15 mm

the lower snow flashover voltage is lower at the snow thickness of 10 mm. Post insulators with large umbrella spacing and edge have higher snow flashover voltage gradient

and can more effectively prevent the snow flashover.