Calculation and interpretation of a grounding grid in two-layer earth with the synthetic-asymptote approach

An accurate method for calculating the resistance of a substation grounding grid buried in two-layer earth is proposed in this paper. The method is based on the image theory and the synthetic-asymptote approach. The synthetic asymptote is an expression that fits between the asymptotes of parameter limits and is therefore accurate throughout the parameter ranges. Despite the large number of parameters involved in the design of a grid buried in earth, the method is still simple enough to give good physical insight.