RESISTANCE FORMULAS OF GROUNDING SYSTEMS IN 2-LAYER EARTH

This paper lists, under one umbrella, the resistance formulas of groun ding systems, namely : the buried grid, the driven rodbed, and the com bination of the buried grid and rodbed. The formulas are synthesized f rom rigorous asymptotes; as a result, they are accurate (averaged erro r approximate to 5%) and do not require empirical tables or graphs. Th e validity of these formulas is verified in this paper, not by their d erivations, since they are too lengthy, but by checking numerically, a gainst the results of detailed-numerical methods and analytically, aga inst asymptotes. The formulas are suitable for calculation with a hand held calculator, and therefore they are useful tools for an engineer i n the field.