地形结构及参数对特高压直流地电流散流特性的影响分析

直流接地极注入电流会对周边电力设施产生不利影响,而地形结构是特高压直流地电流散流特性的重要影响因素。为此,根据接地极极址的不同情况,分别建立了水平双层及复合分层的地形结构。首先,由镜像法和行波法消除了土层间的界面效应,进而推导出一种求解地中电流密度的简易算式,形式简单,易于大规模编程计算。其次,通过软件建模仿真,验证了提出的算式的准确性及可行性。最后,依托工程案例,研究了地形结构及参数对直流地电流散流特性的影响规律。提出的算式可用于特高压直流地电场的计算,对于深层土壤电阻率的测量、交流系统及埋地设施的选址均有一定的指导意义。

Influence of Terrain Structure and Parameter on the Divergence Character of UHVDC Grounding Current

Current from the DC grounding electrode has a negative effect on nearby electric power facilities,and the terrain structure is a predominate factor affecting the current distribution of the grounding current.We established a complicated soil structure and a horizontal 2-layer terrain structure according to the actual DC transmission grounding situation.First,the influence produced by boundary surface was eliminated by an image method and a traveling wave method in order to homogenize the terrain structures;then,an easy-to-use formula for calculating the current density was presented which was simple and good for large-scale programming calculation;thirdly,the correctness and feasibility of the formula were verified by the software simulation;finally,the relation between divergence characteristics of HVDC grounding current and terrain structure were proposed according to project cases.The obtained formula can be used for calculating the grounding electric field of HVDC system,guiding the measurement of depths soil resistivity,and directing the selection of AC system site and buried establishment location.