Topological measurement and characterization of substation grounding grids based on derivative method

Derivative method, which avoids pathological solution of the magnetic field inverse problem, was proposed to solve the problem of drawing loss or unknown of grounding grids. First, a shape function was introduced to describe the distribution of magnetic field which is perpendicular to the surface of grounding grids. Since its odd-order derivatives contain main peaks, the 1st-, 3rd- and 5th-order derivatives were chosen to solve the topology of substation grounding grids and measure the branch current of the grid by determining the position and value of main peak, respectively. Numerical example and experimental result show that the 1st- and 3rd-order derivative method works well with low error and less computation.