Non-destructive depth detection approach for substation grounding grids based on magnetostatics

Abstract

Grounding grid depth is one of the important factors to diagnose the grounding grid faults. However, due to the drawing loss and back fill during the reconstruction, the real buried depth of the grounding grid is changed and unknown. A magnetostatic method to calculate grounding grid depth is proposed in this Letter. Initially, the proposed method is applied on a single buried conductor where the depth is calculated from the extremum points in the surface magnetic flux density function. Furthermore, the branch current is calculated from the main peak value in the derivative of magnetic flux density function. Finally, a comparative analysis is performed regarding grounding grid depth and branch current. It is shown that the horizontal component of surface magnetic flux density yields results with low error as compared to the vertical component.