Study of unequally spaced grounding groups

A new method is presented for designing an unequally spaced substation grounding grid where the grid conductor spacing increases progressively from the periphery to the center. Formulae for determining the spacing between conductors are derived. A procedure for designing an unequally spaced grid is described. The unequally spaced grid designed by using the proposed method can make current density in conductors more uniform, and therefore remarkably reduce earth surface potential gradients. It also uses 30 percent less grounding grid material. The numerical calculations agree well with the scaled down model and field test results