The Causes of the Parameters Changes of Soil Resistivity
Abstract – The grounding of electrical installations is primarily concerned with safety; in particular, the prevention of electrical shock risks of human life. As such, a grounding system must be designed, tested and maintained to satisfy this primary aim. This scientific paper presents a survey of soil resistivity and how its value varies from geological and meteorological factors. Soil resistivity is not only a useful measurable that reflects subsurface structure, but also a basic parameter to the design of effective grounding and lightening prevention / protection system. The most significant variations occur from such parameters of soil resistivity as moisture content, chemical composition, porosity, conductivity, temperature, vertical thickness and divisions, etc. Knowledge of soil resistivity at the intended site provides a valuable insight into how the desired ground resistance value can be achieved and maintained over the life of the installation with the minimum cost and effort.
The electrical characteristics of the ground have an effect on the resistance of the whole grounding system, and therefore to the electrical safety of the personnel, which operates and uses electrical devices .
Soil resistivity is a basic parameter necessary for the design of effective grounding and lightning prevention / protection systems. In addition, resistivity profiling can yield information on characteristics (including depth) of different layers in the subsurface. The resistivity of rocks or soils is in general a complicated function of their porosity, permeability, ionic content of pore fluids and mineralization. In most rock materials, the porosity and the ionic content of the pore fluid are more important in governing resistivity than the conductivity of the constituent mineral grains. In situations where the porous rocks lie well above the water table and the fraction of the pores filled with fluid is negligibly small, mineralization starts to contribute. Igneous rocks tend to have higher resistivity than sediments .