青藏铁路冻土地区接地方式研究

Study on Grounding Mode in Frozen Soil Area of Qinghai-Tibete Railway

青藏铁路沿线多年冻土地区普遍呈现出较高的土壤电阻率,非常容易造成雷击事故。根据格拉段多年冻土地区的特征,提出在铁路沿线变电站采用立体接地网,降低接地电阻和地表电压。采用接地设计软件CDEGS对变电站立体接地网的面积、垂直接地体及季节变化的影响进行了分析,结果表明,在冻土地区选择合适的立体地网参数能够达到降低接地电阻和地表电压的效果,立体接地网的水平面积可选100～150m2,垂直接地体布置在水平接地网边缘,尽可能等间距分布。季节性冻土的垂直接地体长度可选为15 m,根数选10～15;对于不太厚的多年冻土,垂直接地体长度可取30m,根数选15～20。冻土中立体接地网可减小季节因素的变化对接地电阻的影响。

The high soil resistivity at permanent frozen soil area along the Qinghai-Tibet railway tends to lightning strike accident. Based on features of permanent frozen soil regions along Germo-lhasa railway section, it is proposed to introduce a three-dimensional grounding grid at substations along the railway for decreasing the grounding resistance and ground surface voltage. The area of ground grid, vertical grounding electrode and seasonal variation was evaluated using grounding design program CDEGS. The results showed that three dimensional grounding grid with properly determined parameters may decrease the grounding resistance and ground surface voltage. The horizontal surface of grid of 100 - 150 m^2 may be chose, with equidistant vertical electrodes of 15 m length at fringe of horizontal grid. The effect of seasonal variation on grounding resistance can be weakened by using the three-dimensional grid.