Effective Sounding Depths for HVDC Grounding Electrode Design: Wenner versus Schlumberger Methods

This paper compares the performance of the Wenner and Schlumberger soil resistivity measurement methods for vertical electrical sounding. The effective sounding depths of the two methods are examined, based on computer simulations of soil resistivity measurements in various two-layer soil structures. Also studied are uncertainties associated with both methods in the prediction of soil models, when near-surface local soil volumes with distinct electrical properties are present. It is shown that the Schlumberger method is particularly sensitive to such finite soil volumes, potentially resulting in significant error in the estimated deep soil resistivity and therefore in HVDC grounding electrode design