Except from the two basic and conventional contamination accumulation modes

the common slow solid mode and the rapid liquid mode

there is another kind of rapid contamination accumulation mode which is even easier to cause the pollution-flashover. It is related to human activities

such as burning straw and setting off firecrackers

or natural factors as forest fire and acid rain. Those factors result in the weather condition of high conductivity and high humidity

due to whom the rapid contamination accumulation is added to the normal one. In this paper

the relationship between flashover voltage and the fog conductivity is researched

by doing artificial polluted tests using porcelain insulators of XP-70. Contrast to the process of the pollution’s getting wet under the clean fog

the variation characteristics of flashover voltage under the high conductivity fog is systemically studied.It is pointed out that the high conductivity fog decreases flashover voltage

which is more notable on low salt deposit. After studying the changing law of the flashover voltage under different fog conductivity and salt deposit

the relational expression among them was obtained. According to the local meteorological environment

the warning model was revised

by using the expression. It also can be decided if the insulation configuration should be improved.