The mutual inductance calculation between the loop coil and the grounding grid using the superposition theorem method

As a key aspect of power system grounding protection, the detection of corrosion and fractures in the grounding grid has received greater attention. The data obtained by the Transient Electromagnetic Method (TEM) requires validation through electromagnetic coupling between the loop coil and the grounding grid. Therefore, based on Neumann's formula, this paper first derives analytical expressions for mutual inductance between a circular coil and a quadrilateral plane, as well as between a quadrilateral coil and a quadrilateral plane. The grounding grid is modeled as a composite of multiple quadrilateral planes, and the mutual inductance between the loop coil and the grid is analyzed using the superposition principle. Using the parameters of a typical grounding grid transient electromagnetic system, the mutual inductance is calculated and compared with other methods under identical conditions. The results demonstrate that the proposed approach achieves minimal relative error. Furthermore, this method can be extended to mutual inductance calculations between polygonal coils and polygonal composite planes, offering high versatility and scalability.