引线间互感对接地阻抗测量结果的影响分析

The Impact of Mutual Inductance Between Measuring Leads on the Grounding Impedance Measured Value of grounding Grid

准确分析引线间互感对接地阻抗测量结果的影响是精确测量接地阻抗的基础。分别采用基于薄壳理论的接地装置有限元模型和引线间互感计算公式对不同电阻率土壤中不同尺寸接地网进行建模仿真,得到了不同土壤电阻率和接地网尺寸下引线间互感引起的测量误差曲线;并在此基础上计算得出是否需要考虑引线间互感影响的分界线--5%误差分界线。结果表明:随着土壤电阻率和接地网尺寸的变化,引线间互感引起的测量误差是不断变化的;5%误差分界线右下侧的测量误差小于5%,此时可忽略引线间互感的影响;分界线左上侧的测量误差较大,甚至可能高达接地电阻真实值的数倍,此时应考虑引线间互感的影响。此结果对接地阻抗的精确测量具有一定的工程指导意义。

The mutual inductance between measuring leads is an important factor which influence grounding impedance measured value. The author present a finite element method for large grounding grid based on the shell theory firstly, based on the finite element model of grounding grid and mutual inductance formula, the variation curve of the grounding impedance measurement error under different soil resistivity and grounding grid size is obtained. Finally, we get the dividing line between the mutual inductance should be considered and not(the 5% error dividing line). The results show that, the measurement errors are changing with the variation of the soil resistivity and the grounding size. For grounding grids in the right lower lateral of the 5% error dividing line, the mutual inductance error is less than 5%, which can be ignored. While for grounding grids in the above-left of the 5% error dividing line, the mutual inductance error can be several times the true value of grounding resistance, which has to be considered. This result has certain engineering guiding significance for the accurate measurement of grounding impedance.