复杂土壤结构对水电站接地装置散流机理影响分析

Analysis the Effect of Complex Soil Structure on the Dispersion Mechanism of the Grounding Device in the Hydropower Station

准确计算复杂土壤结构中接地装置接地参数及其散流机理是水电站接地装置合理优化设计的基础。提出考虑大范围复杂土壤结构的接地装置有限元计算方法,针对有限元数值计算方法中大范围求解区域和接地导体截面尺寸的差异导致的计算量过大问题,采用二维接地导体与三维散流土壤耦合的有限元数值计算方法;基于有限元模型分别建立垂直三层土壤模型、块状土壤模型以及落差土壤模型,对接地装置散流过程中土壤中的电流密度、电场强度分布规律进行了详尽分析;并对河道两岸土壤电阻率、河水深度对水电站接地网散流过程及接地电阻的影响规律进行了定量分析。对比分析了三种不同土壤模型对水电站接地网散流过程及接地电阻的影响规律,结果表明河水深度是影响接地装置散流过程的重要因素,复杂土壤结构中水电站接地网设计中宜采用考虑实际河水深度的块状土壤模型和落差土壤模型。

The accurate calculation of grounding device parameters and current flow mechanism in complex soil structure is the foundation of reasonable optimization design of the hydropower station grounding device. A finite element calculation method of grounding device considering large scale complex soil structure is published in this paper. In this modeling, two dimensional finite element is coupling with three dimensional finite element to overcome the large computation induced by large contrast between extensive soil domain and grounding conductor. Vertical three layer soil model, massive soil model, and drop soil model were established respectively based on the presented method; current density, electric field strength in soil are analyzed in detail. The influence of soil resistivity of the riverside and the depth of river on ground resistance of hydropower station grounding device is analyzed quantitatively. The results show that the water depth is the important factor influencing the current flow process of grounding device, design of hydropower station grounding device in complex soil structure should consider the actual water depth of massive soil model and drop soil model.