| From the data collected by Lightning Location System, we can find that Chongqing is strong -lightning-day and has about 95 lightning days per year and has 7.022 hours per lighting day. In addition to the ground flashing density is 0.1216/km2·d and beyond the value of rules. So according as the fact of Chongqing power system,the paper will investigates the 110kV power transmission line because lightning often stroked the line last years.On the basis of research for power transmission line's lightning-proof property, this paper calculate the lightning-withstand level when lightning strike to the tower and strike to the line directly and discusses the factor that effect line-surge arrester's function. This paper takes landform of transmission line aisle and spanning instance into account with reason, establishes the model of light striking to the tower and transmission line by wave transmitting on power line. The model considers peak value of lightning current, tower grounding resistance, tower style, line surge impedance, power frequency voltage and distance between towers. When calculates the lightning-withstand level of lightning striking to line directly, this paper adopts Electric Geometry Model method because it can satisfy the fact of the transmission line on mountainous area. The results indicate:1) The line-surge arrester can improve the lightning-proof property of transmission line on mountainous area and enhance the lightning-withstand level.2) Tower grounding resistance, distance between towers, etc can affect the function of line-surge arrester. When their value increase, the line-surge arrester 'action weakens.On the basis of calculation, we fix line-surge arrester on 110kV Shuang-Han transmission line and Shuang-Hai transmission line. After the observing of transmission line for a lightning storm season, we didn't find the lightning trip. The result indicates line-surge arrester can improve lightning-proof property evidently and reduce the lightning tripping outage.
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