| The mountainous terrain is complex,the soil resistivity is high,lightning activity is very frequent,coupled with the mountainous transmission line corridor environment is bad,resulting in transmission line lightning trip accidents often happen.With the rapid development of Chinese economy and the continuous expansion of power grid scale,the economic loss and social impact caused by power grid failure are also increasing.In order to better adapt to the situation and reduce the loss caused by lightning disaster,it is very important to build a mountain transmission line model and analyze its lightning resistance performance.Based on the similarity between thundercloud discharge and long air gap discharge,a leading development model is established in this paper,and the transmission lines of four typical terrains,such as plain,mountain top,hillside and valley,are studied with this model.The results show that when the transmission lines are in plain terrain,the wires are well shielded by ground and earth.When the wire is in the valley terrain,it is shielded by the mountain on both sides,and there is almost no strike around it.When it is on the mountaintop and hillside,it is necessary to pay more attention to its lightning resistance.By calculating the strike rate of different phases,it can be seen that the running voltage of transmission line wire will affect its mine induction ability.Based on the ATP-EMTP electromagnetic transient software,the transmission line counterattack simulation model is built,including the tower multiwave impedance model,the insulator flashover model based on the pilot method and the impact grounding resistance model considering the impact of spark effect.This model is used to analyze the effect of impact grounding resistance of tower on lightning resistance of line.The analysis results show that the impact grounding resistance of the tower has a great influence on the lightning resistance of the transmission line.Reducing the grounding resistance of the tower can effectively improve the lightning resistance of the transmission line.When transmission lines pass through mountains with high soil resistivity,the ground resistance may not be reduced to a small range.In this case,appropriate measures should be taken to reduce the risk of tower counterattack.Based on the lightning current and fault recording provided by the lightning positioning system,the characteristics of the fault are analyzed by combining the shape parameters of the tower and the geographical information of the location.The model established in this paper is used to evaluate the differential lightning protection of 5 220 k V transmission lines in Tonghua area,and the lightning protection reconstruction principle for mountainous terrain is given.According to the results of risk assessment and combined with the information of tower,landform and geological conditions of the region,lightning protection reconstruction suggestions are put forward for the tower that needs to be rebuilt. |
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