双层土壤台阶型特高压杆塔基础接地参数的计算与分析

台阶型特高压杆塔基础结构复杂,包含多个块状介质,在水平分层土壤条件下,以往简化模型计算台阶型杆塔基础的接地参数存在缺陷,从而对特高压杆塔基础的接地设计造成不利影响。为此,依据电磁场基本原理,计及土壤水平分层结构和杆塔基础混凝土,采用边界元法对静电场积分方程进行离散,并基于C++编程进行数值求解,以典型台阶型特高压杆塔基础的接地模型为例,计算得到均匀土壤中该接地模型的接地电阻,并与其他计算方法得到的结果进行比较,验证了该方法的有效性和正确性。另外通过计算水平双层土壤接地模型的接地参数,分析了土壤条件、基础尺寸对杆塔基础接地的影响。结果表明,当上层土壤厚度较浅时,降低下层土壤电阻率对减小杆塔基础接地电阻效果明显,准确估计下层土壤电阻率对接地计算有重要影响,增大基础尺寸可降低接地电阻。

Calculation and Analysis of Grounding Parameter for Two-layer Soil Step-Type UHV Tower Foundation

Considering structure complex and multiple volume medium, the traditional simplified method for calculation of grounding resistance of step-type UHV tower foundation causes large deviation, which is unfavourable of grounding design of UHV tower foundation. Based on the basic laws of electromagnetic field, considering soil horizontal slice structure and concrete of tower foundation, BEM is used to discretize the integral equations of electromagnetic field and numerical solutions are obtained by C++ programming. Taking the grounding model of typical step-type UHV tower foundation for an example, the grounding resistance in uniform soil is calculated. Compared with other methods, it proves the correctness and validity of the algorithm. In addition, grounding parameter is calculated for UHV step-type tower foundation in two-layer soil. The influence of soil conditions and foundation size on grounding parameter is analyzed. The results show that when the top soil thickness is small, the performance for decrease of UHV tower foundation grounding resistance is obvious with smaller subsoil resistivity. Therefore, accurately estimating subsoil resistivity is important for grounding calculation. At the same time grounding resistance would decrease by enlarging foundation size.