Effect of Soil Resistivity Measurement on the Safe Design of Grounding Systems

Abstract

A prerequisite for the proper and safe designing of a grounding system is the full knowledge of the ground structure in the terrain of installation. Through soil resistivity measurements, engineers are able to illustrate the ground profile, which constitutes the most significant parameter for the design of a grounding system and for determining the maximum permissible limits of step and touch voltages. This paper highlights the high importance and necessity for engineers to choose the proper measurement axes of soil resistivity in the terrain of interest and to choose suitable measurement depths, as well the combination of axes for the final determination of the ground profile. The variance of soil resistivity values, as a function of axis distance and the impact of axis placement on determining the uncertainty of measurements, is also analyzed in detail in this study. Furthermore, this work studies the value variance of step and touch voltages as a function of measurement axes, considering two- and three-layer soil models, based on soil resistivity field measurements performed at the university campus. Therefore, the proper and premeditated measurement of soil resistivity, particularly in anisotropic ground, is proved to be of major importance for the full designing of a safe grounding system.

Study on Structural Parameters and Analysis Method of Soil Successive Impulse Discharge Channel

“…The calculated average volume of the prism is 77.02 cm 3 , the actual value is 78 cm 3 . It shows that the method is feasible.…”

“…Soil is the most important medium in the grounding system [1][2][3][4][5]. Its discharge characteristics directly affect the lightning strike performance of grounding devices [6][7][8].…”

Influence of Lightning Current Parameters and Earthing System Designs on Tower Footing Impedance of 500 kV Lines

“…In particular, the response of the earthing system subjected to lightning is very different from the low frequency steady-state. This is caused by the occurrence of the soil ionisation phenomenon during lightning current discharge [23][24][25]. It has been recognised for many years that the soil will act non-linearly when it is subjected to a high current discharge.…”

Functionally Graded Multilayered Soil Models, an Alternative to Modeling the Soil Electrical Resistivity for Computing the Grounding Resistance

“…Determining the conductive properties of the soil is a fundamental requirement when designing a grounding system. In the theoretical calculation stage, it is necessary to choose a model for the electrical conductivity of the soil in order to calculate the grounding resistance that the chosen electrode will have [1]. From a general point of view, it would be necessary to solve the equation ( ( ) ( )) 0 rr      together with some boundary conditions, where () r  is the absolute potential at the sourceless point r and () r  is the function that represents the point conductivity of the ground.…”

“…The choice of a constant conductivity in each layer allows calculating the potential in the region of space occupied by each layer from a Laplace/Poisson equation arising from the equation for a generic conductivity. The connection between the solutions corresponding to each layer is made by imposing the continuity of the potential at the different interfaces , 1 1 , 1 ( ) ( )…”