The three monotheisms in the world, Judaism, Christianity and Islam, all originated from Semites in Middle East and were one and the same line of ancestries denoting a certain state that existed in the past.

In politics the small states gathered to the united Semitic Nation but did the opposite in culture and the culture-dominant nations acknowledged allegiance to culture-inferior nations.

In order to provide a scientific reference for the constructions of DC transmission lines in high altitude areas,the flashover characteristics of two kinds of large tonnage insulators(porcelain and glass insulator) were investigated systematically in natural high altitude areas(1970 m).

Artificial pollution experiments was carried out with up-and-down method under direct current(dc)voltage in natural high altitude areas(1970 m)to analyses the effect of insulator profiles and suspension patterns on flashover characteristics of porcelain,glass,and composite insulators.

In order to provide a scientific reference for the constructions of UHVDC transmission lines,the flashover characteristics of three kinds of insulators(porcelain,glass and composite insulator) are investigated systematically in natural high altitud.

So far, in the region of 4000 m more above sea level, there have not carried on the study on flashover performance of insulator of electric railway at home and abroad.

Then,based on the“U”distribution of the flashover voltage values of composite insulators with the increase of the temperature cycle in the cold fog,the flashover performance evaluation method is brought forwa.

Therefore, a systematic study of flashover performance and mechanism of insulators covered-with.