Resistivity Testing and Modeling.
Soil, being a conductor, has the electrical properties of resistivity and conductivity. Additionally, when AC current passes through soil, the soil can present a susceptance, or an imaginary portion of the admittance of a grounding element or a pipeline.
Soil properties change along the surface of the earth and with depth. To design grounding and analyze electrical interactions, soil electrical properties need to be known as accurately as possible given practical constraints. Usually bulk soil resistivities are measured using a method of electrical current injection and electrical field strength measurement. These are called apparent soil resistivity measurements.
Apparent soil resistivity testing can be completed using Wenner, Schlumberger or Dipole Electric Field Arrays. These arrays can be completed to various electrode spacings. To arrive at a model of the actual soil resistivity profile, single or multi dimensional software is used to convert the apparent data into resolved resistivity values and soil patterns.
Soil Susceptance can be measured using equipment that give polarization data and waveform analysis. This information is very useful for substation, HVDC grounding and other large grounds used in AC grounding.