Analytical Expressions for the Resistance of Grounding Grids in Nonuniform Soil

Some improvements and extensions of certain resistance formulas for grounding grids are proposed enabling their application at two-layer soils for a wide range of soil parameters. To test the accuracy and the applicability margins of the expressions proposed as well as of some other available formulas , a comparative analysis of ground resistances for a set of sample grids is performed, using the complete digital model ing as the reference basis.