杆塔冲击接地阻抗的有限元分析

电力系统的运行经验表明,大多数输电线路事故是由雷击输电线路或杆塔引起跳闸所致。经由输电线路杆塔接地体流入大地的雷电流可达数十甚至上百千安,此时接地体周围土壤出现非线性火花放电现象。为了提高输电线路耐雷水平,降低雷击故障率,考虑实际工况下土壤非线性火花放电效应进行杆塔接地体参数计算对降低杆塔接地电阻的优化设计至关重要。文中基于电磁场理论,考虑土壤中的火花效应特性,采用有限元数值计算方法建立了仿真模型,实现了高幅值冲击接地电流下接地体入地散流过程的模拟。研究表明,该仿真模型与试验结果偏差小于10%;随着雷电流幅值的升高,冲击接地阻抗降低且有饱和趋势;接地体阻抗随雷电流频率增大而增大。

Analysis of Tower Grounding Impedance Under Lightning Impulse by Finite Element Method

Operating experiences of power system shows that most of accidents occurred at transmission lines were caused by lightning. The lightning current flowing through tower grounding electrode can be dozens or even hundreds thousands amps, which leads to nonlinear spark effect in the soil around the electrode. In order to improve the lightning prevention of transmission lines, it is necessary to take the non-linear spark effect into consideration in the simulation of tower grounding electrode, which is essential for the design. In this article, a new model based on Maxwell differential equations is built and finite element method is used to calculate the model by COMSOL - multiphysics software. Also, the non-linear sparking discharge phenomenon in soil is considered. With this model, a grounding electrode simulation with a high amplitude can be done. The results show that the deviation between the simulation model and the experiment result is less than 10%. With the increase of the amplitude of the lightning current, grounding impedance decline and will be saturated. The grounding impedance increases with the increase of the lightning frequency.