The Impact of Apparent Frequency-Dependent Soil Properties on Electrical Grounding Characteristics

The purpose of this work is to estimate and reduce errors that can occur if apparent frequency-dependent soil properties are used for calculations of the grounding potential rise and exact inhomogeneous soil structure is neglected. Such estimation would help evaluate, which level of complexity is needed for measurement techniques when soil properties are used for grounding design. Simulations have shown that errors associated with the usage of apparent soil properties for electrical grounding characteristics can be avoided if the depth of investigation is chosen appropriately (except for specific cases). A measurement approach was proposed that takes into account which instruments are available for measurements. The approach was verified by measurements with inhomogeneous soils. In addition, it was found that to avoid the high-frequency effects in measurements of soil properties, it is convenient to limit the depth of investigation (rather than dipole size). It has also been demonstrated that soil inhomogeneities can lead to differences in apparent soil properties at higher frequencies (for the same low-frequency resistivity).