The Non-Uniform Grid in the FDTD Modeling of the Earthing Conductor in the Transient Grounding Resistance Analysis

The grounding system plays an important part in the lightning protection system of power and communication systems. The finite-difference time-domain (FDTD) method is widely used in modeling complex electromagnetic interaction problems. However, it is difficult to model the earthing conductor using the standard FDTD method in the transient grounding resistance analysis, for the electrically small depth of the earthing conductors. In this work, non-uniform grid in the FDTD methods, which is typically used to resolve fine structures, is introduced into reduce the computational domain and therefore lead to a reduction of the computational cost. To further reduce the computational memory, the uniform grids are used in the electrode length direction while non-uniform grids are occupied in the electrode sectional directions. The efficiency of the proposed model has been approved by verifying both the electromagnetic field components near the earthing conductor and the grounding resistance.