A new way to interpret the three-point method for soil modeling in two horizontal layers

Abstract

Faced with the design of the grounding of an electrical installation, we must have an adequate model of the terrain. Modeling in two horizontal layers has proven to be the most useful, practical and accurate. In a previous presentation [1] a new approximate formula was proposed to be considered in IEEE 80-2000 and IEEE 81-2012 standards for terrain modeling when four-point measurement methods (Wenner or Schlumberger) were used. In this presentation, a similar procedure is used for the three-point method. It leads to the presentation of a new formula that relates the parameters of the two-layer model and simplifies their calculation from the series of field measurements. The form of application of the new procedure and the differences and complements with the other methods are shown. This method, by using rods during the measurements, is consistent with a common construction practice. This has notable advantages over the four-point methods in some types of terrain, especially those with high surface resistivity; while it can be used as a complement in other measurements except in those to be carried out on rocky terrain where it is difficult to drive rods.