Lightning Protection Calculation And Analysis Of 35kV Power Grid Of Xin-mi Mining Area

In the supply network of Xin-mi mine, most part of the coal mine power supply is charged with the 35 kV power supply system. So, the safety, stability and reliability of its operation must be ensured. However, the 35 kV power lines are mostly through these regions full of mountainous hills. The terrain is also complex, high-intensity lightning activity is frequent and soil ground resistance is always high. For these reasons, lightning has become a priority to work during the rainy season. Though part of the lightning protection measures has been taken, the effect is quite not well. The damage of power facilities caused by the lightning are still occurred sometimes. Therefore, it’s quite necessary to research the lightning protection technology and measures in the area of 35 kV power system.In this paper, it’s based on the lightning protection information by years and basic electrical parameters measured in the Ping-shen line of 35 kV. By considering the factors of topography, tower span and tower grounding resistance on the impact in transmission lines, the simulation model of lightning lines is established. Based on the analysis on these models, the withstanding level and rate of lightning trip are first studied. Then, the changes of withstanding level would be researched by installation the lightning conductor and lightning arrester, changing the tower grounding resistance. Summarizing the simulation results, it could be concluded taking these measures are effective to reduce the rate of lightning trip.In addition to analysis of the lightning protection, harms of the lightning invasion wave in 35 kV substation would also be considered in the simulation analysis. In other words, the impact on the main electrical equipment of substation by lightning invasion wave would be involved in the analysis. Also, the conditions affected by lightning invasion wave is analysis in-depth,when the lightning point and the impulse grounding resistance of line tower changes, which provides basis for improving the lightning protection in substation.Through simulation analysis, the main factors causing the high lightning trip in Ping-shen line of 35 kV are summarized. Combined with practical engineering, the line arresters should be installation on the tower which is easier to be struck by lightning. If possible, lightning conductor should be erected across the board as much as possible, and the tower grounding resistance should also be reduced, which are to raise the line withstanding level and reduce the rate of lightning trip in Xin-mi mine of 35 kV.