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Desiccation cracking is a common and natural phenomenon under a drought climate. The geometric and morphologic characteristics of the crack pattern are critical to understanding the response of soil mechanical and hydraulic properties to drought climate. It is always a big challenge to obtain the refined geometric structure of the in-situ soil desiccation crack network. This study proposes an integrated method named ERT+ for determining the three-dimensional geometry of in-situ soil desiccation crack networks by integrating multi-source data from electrical resistivity tomography (ERT), surface image analysis, and depth investigation. The proposed method was applied to three in-situ expansive soil sites with different crack geometries and soil properties. The results showed that the joint application of ERT with other investigations reduced the ambiguity of interpreting each technique independently. The crack network model characterized the three-dimensional geometric structure of the desiccation crack accurately and quantitatively, verifying the effectiveness and feasibility of the ERT+ method. Field and laboratory experiments showed that heterogeneity in soil properties resulted in different cracking morphologies (width, depth, and width-depth ratio). The crack geometric data suggested that the width-depth ratio of the crack network was related to the cracking modes and the soil properties, indicating the non-homology of different crack networks. In addition, the correction gradients calculated from the ERT+ method also varied with the cracking modes and soil properties, further suggesting the reliability and prospect of the proposed method.

This paper investigates the steady-state resistance (RDC) of copper tape electrodes across eight configurations. The study evaluates both field measurements and simulations using CDEGS at two distinct sites with varying soil characteristics. It emphasizes the impact of electrode size, installation sequence, and soil disturbance caused by sequential installations. Specifically, the results reveal that the first configuration, which maintained a 100% tape-to-trench ratio with no disturbance, yielded computed values within the measured range at both sites. Subsequent configurations demonstrated varying degrees of soil disturbance, affecting RDC values, particularly in high-resistivity conditions. At the low-resistivity Site 1, as the tape-to-trench ratio increased, discrepancies between measured and computed RDC values decreased, highlighting a strong dependency on electrode size and soil cohesion after backfilling. In contrast, at the high-resistivity Site 2, RDC values remained relatively stable with increasing tape-to-trench ratio, likely due to lower soil cohesion and higher air void presence. These findings underscore the importance of considering soil disturbance effects in computational models to enhance the accuracy of RDC predictions and optimize grounding performance.

【Objective】 Crop growth and ecological functions in arid and semi-arid loess regions in northwestern China are limited not only by topsoil water directly available to crop but by deep soil water which functions as a reservoir. Slopes and lands formed by artificial retaining are two typical geographical units in small watersheds in the loess plateau. This paper presents a method to estimate soil water distribution in them up to 12.5 m deep. 【Method】 The method was based on electrical resistivity tomography (ERT). We measured electrical resistivity of the soil in typical slope and retained land in the small Liudaogou watershed in northern Shaanxi province. Using the measured soil volumetric water content, a power function relating the resistivity to soil water content was established, from which we calculated water distribution and water storage in the 0~12.5 m profile in both the slope and the retained land. 【Result】 The distribution of electrical resistivity over the slope was significantly affected by slope position, with the resistivity decreasing gradually from the slope top to the slope toe. Such changes were associated with vegetation consumption of the topsoil water and redistribution of the infiltrated precipitation over the slope. The vertical distribution of the resistivity in the retained land showed a high-low-high variation; this was also related to root water uptake from the topsoil and precipitation recharge to the subsoil. ERT inversion showed co-existence of a saturated zone and an unsaturated zone in the retained land, while the slope was partly saturated. In a 1.8×104 m2 of retained land, there was 1.49×104 m3 of water in the 0~6.5 m unsaturated layer, and 5.10×104 m3 of water in the saturated layer. In a same area but on the slope, there was only 2.59×104 m3 of water in the 0~12.5 m soil layer. 【Conclusion】 Retained land contains more water than slope, and the deep soil in it functions as a reservoir banking infiltration water in wet seasons. ERT is suitable for measuring spatiotemporal variation in soil moisture in both slopes and flatten plains in the loess plateau.

Inspection and assessment of ageing buried metallic infrastructure such as pipelines can be costly, especially when soil sampling programs are involved to evaluate large networks and pipe health conditions. In order to reduce these costs through assessment prioritisation at infrastructure locations that are scientifically inferred to be under highly corroded state, advancements in current approaches are necessary. In this study we have investigated the utility of soil resistivity as an index for buried and ageing pipe health status through numerical and field case studies. Numerical study showed that the monotonous relationship between soil resistivity and maximum pit depth that is often considered in literature as linear is actually non-linear. Field study involving in-situ wall thickness measurements of 3 separate water distribution mains (each > 1.5 km in length) at selected excavated locations were compared with the saturated soil resistivity (ρsat) acquired a-prior. The ρsat was found to be highly correlated to the maximum corrosion pit depths observed in-situ. This correspondence is argued to exist provided the saturated soil resistivity displays statistical uniformity along the pipe and the pipes are not under submerged conditions. Locations on the pipe where ρsat < 15 Ω m were found to have corroded relatively more than other locations; in one instant a leaking pipe due to excessive corrosion was also observed. A practical indirect assessment framework was proposed that can be utilised immediately in professional practice.

In order to overcome the shortcomings of fuzziness, randomness and interaction between the soil corrosion factors of buried pipeline, as well as the low accuracy of prediction with the traditional methods, a prediction model of external corrosion rate was established with 10 influencing factors as the input, and the external corrosion rate as the output based on the field data of corrosion coupons of a buried pipeline. Thereby, the data samples were trained, verified and tested using the Radial Basis Function (RBF) neural network mode, and the key parameters affecting the corrosion were identified through Sobol sensitivity analysis. The results show that the mean square error is 0.000 99 when 10-35-1 type RBF model is iterated to step 2 273, and the correlation coefficients of the training, validation and testing stages are 0.970 7, 0.981 3 and 0.990 1 respectively. Compared with BP, MLR and SVM models, the average relative error of RBF neural network model is 2.07%, indicating that RBF neural network model has some advantages in terms of the external corrosion rate prediction of buried pipeline. The soil resistivity has the maximum effect on the external corrosion rate. Moreover, the soil resistivity, pH value, and Cl- content significantly interact with other factors, which should be paid much more attention. Generally, the established model can be effectively applied to the external corrosion rate prediction of pipeline, and the results could provide theoretical basis and reference for pipeline integrity management.

This article presented the characteristics of the grounding electrodes in uniform and two layer soils when subjected to lightning including the impacts of soil ionization with frequency, soil resistivity, and permittivity variations. The critical breakdown field strength of two layer soils with different values of the reflection factors was presented. The transient probabilistic grounding potential rise and the transient impedances of the horizontal and vertical electrodes were investigated in uniform and two layer soils including the effect of soil ionization with frequency. Finally, the influences of resistivity and permittivity variations which have substantial impacts on the electric field at the occurrence of the soil ionization were considered. Moreover, transmission line approach (TL) with the aid of ATP has been used to compute the transient grounding voltages. The results indicated that the reflection factor has a significant impact on the equivalent radius of the grounding electrode. It is also observed that the peak values of the lightning induced voltages decreases sharply when the soil ionization phenomenon considering the variations in soil resistivity and permittivity with the stroke frequency changes. Furthermore, the impedances of the burial electrodes that have negative reflection factors were lower than that in case of positive reflection factors.

Soil resistivity is an important parameter for designing electrical earthing system. The measurement of soil resistivity is greatly influenced by moisture content, temperature, porosity, degree of saturation, number of soil layer(s), and frequency of lightning current. Researchers have proposed various methodologies to provide an approximation of soil resistivity using the listed parameters. In order to ease the process of estimating soil resistivity at a particular area, there is a pressing need to devise a simple tool that enables the calculation of soil resistivity in the most accurate manner. As such, this research proposes a reliable tool for quick evaluation of soil resistivity based on variousmethodologies using Microsoft Excel’s built-in-functions and Visual Basic Application (VBA) Next, the developed tool was validated using two methods, in which the output value of the calculator was compared with data retrieved from IEEE Std 142-2007 and data reported in past studies. The validation results revealed that the developed calculator may serve as a significant application in future due to its time-saving and cost-effective attributes.

In order to protect the transmission lines against lightning strikes, it is important to investigate the tower grounding system. In this paper, a recent method called hybrid continuous circuit-trapezoidal integration method is used to calculate the impulse impedance of the grounding system. Moreover, conventional structures of the grounding systems have been simulated and the results show that, with the same wire length, the square with additional wire system has the least impulse impedance as compared to counterpoise, square and crow’s foot. Moreover, the effects of soil resistivity and lightning current rise-time on the impulse impedance of these grounding systems are investigated. It is concluded that the design of the grounding system depends on the geographic location of the site in terms of soil resistivity and isotropic characteristics of the area in terms of lightning current rise-time.

In view of problems of limited terrain, short effective dispersion length, and low resistance reduction efficiency in the extensional resistance reduction of the grounding grid of incoming line section of mine substation, a resistance reduction method using long -distance extension lead for auxiliary grounding of incoming line tower was proposed. The grounding calculation software CDEGS is used to establish simulation model of 'Τ' type, 'Γ' type, box type, vertical type unidirectional auxiliary grounding network, and study stray current characteristics of unidirectional auxiliary grounding grid of steel tube tower and corresponding influencing factors. The research results show that the longer the extension lead, the higher the resistance reduction efficiency; when the extension lead length exceeds 60 m, the resistance reduction efficiency is stable at about 80% under the action of high -frequency current; the 'Γ' type unidirectional auxiliary grounding grid has stable stray current characteristics, strong shunting ability, and its resistance reduction effect is the best; resistance reduction efficiency of the unidirectional auxiliary grounding grid is more than 70% under different soil conditions. In practical engineering applications, it is recommended to determine the extension lead length and terminal structure of the auxiliary grounding grid according to the actual soil conditions, and to lay the auxiliary grounding grid to areas with low soil resistivity or to take local soil replacement measures for areas with high soil resistivity to improve the resistance reduction efficiency of unidirectional auxiliary grounding grid of the incoming line tower.

Research relevance. One of the main causes of high accidents and outages in distributed power supply systems of 6(10) kV oil well clusters is damage to overhead power lines due to single-phase ground faults. Widely conducted researches to determine the location of a single-phase ground fault have established a correlation between the determination accuracy and a large number of changing factors, such as operating mode parameters, overhead power line parameters, damage type, transition resistance, soil resistance, and taking their average values, regardless of changing climatic conditions. Rationing of technical means for determining the location of a single-phase ground fault according to instrumental errors without taking into account the methodological component defines the error in determining the location of the damage, reaching 30 %. Thus, the relevant research is aimed at determining the primary parameters of transmission lines and minimizing the methodological error in defining the location of damage to transmission lines considering climatic factors. The main aim of the research is to improve the accuracy of determining the location of a single-phase ground fault of a 6 (10) kV transmission line with developing a methodology that takes into account the influence of climatic factors. Research methods. The basic physical processes of propagation of an electromagnetic wave in a power line are taken into account. The main principles of the theory of electrical circuits and the electromagnetic field are used; MATLAB Simulink package algorithms. Research results. The authors have developed the algorithm that allows determining the distance from 6(10)/0,4 kV substations to the point of single-phase ground fault occurrence in distribution networks of oil well clusters taking into account climatic factors. A simulation model of a 10 kV distribution network supplying oil well clusters considering the dependence of the primary transmission line parameters on climatic factors and soil resistivity, was developed in MATLAB Simulink.

The corrosion behavior of carbon steel X36 (CSX36) in solutions of soils collected from different areas linked to the main pipe network of a water distribution system in Jeddah City (Obhour Al Shamaliyah, Ob-Sh; Al Shateie, Sh; Al Safa, Sf; Al Samer, Sa; and Al Jameaah, Ja) at an ambient temperature (23 ± 1 °C) was studied. The corrosion behavior was monitored using various techniques, such as weight loss and electrochemical (open circuit potential [OCP]; electrochemical impedance spectroscopy; and potentiodynamic polarization) measurements. Visual and microscopic examinations of the surface morphology of the studied metals were evaluated and discussed. The corrosion rates in all the studied soil solutions decreased with an increase in the immersion period over 80 weeks. The corrosivity of the studied soils based on weight loss measurements followed the order Sh > Ja > Ob-Sh > Sa > Sf. The value of the OCP gradually shifted to more negative values, indicating a higher tendency to corrode. For the soil solutions studied, the Ecorr shifted to more negative values, indicating that the corrosion process was under cathodic control. The values of icorr and 1/Rp tended to increase as the soil resistivity decreased. Moreover, there was good consistency between the corrosivity order of the studied soil solution obtained from electrochemical impedance spectroscopy and PDP measurements in the following order: Ob-Sh > Sh > Ja > Sa > Sf. A comprehensive assessment of the soil corrosivity based on various soil variables revealed that soil solutions of Ob-Sh and Sh are extremely corrosive, while the rest of the soil solutions are noncorrosive.

The joint application of geophysical investigations, non-invasive methods, and geotechnical investigations, invasive methods, in order to interpret the geological features in subsurface has been increasingly accepted, however, the correlation between the values collected by the geophysical methods and the direct investigative techniques have been developed in recent years. The obtained linear relationships are site specific and complementary studies are needed to establish their validation and limitations for each site. In this study, Electrical Resistivity Tomography (ERT) was used with Standard Penetration Test (SPT) for geotechnical investigation at three hillslope sites with different tropical soil properties in Bahia, Brazil. The results from thirteen boreholes were analyzed against data from 2D inverted sections. Linear fitting successfully correlates resistivity and NSPT for one borehole. Correlations of electrical resistivity and NSPT values were also performed using soils with similar compositions and physical characteristics, which showed good results. The coefficient of correlation (R) was 0.94. In addition, results the fitting slope coefficient seems to be dependent of soil genesis (lithology, texture and clay content variation) scription obtained in SPT surveys.

Spatial information about soils generally results from local observations which are destructive and time consuming. Geophysical techniques could help soil mapping since they are non-destructive and fast. Electrical resistivity is interesting for soil studies due to a wide range of values and as it depends on soil characteristics. This work aims to study soil spatial variability using electrical resistivity. GPS defined grid points of 40X40 m were installed in the experimental western farm (EWF) in the Faculty of Agriculture of Cairo University in Giza. Electrical resistivity was measured at 40 points using 4-electrodes Wenner array in a line perpendicular to the path direction. Soil resistivity data from 2-depths profiling mode was considered to produce two apparent resistivity maps and geostatistically tested. Soil resistivity taxa were sampled and analyzed for soil moisture, EC and bulk density. Krigged soil resistivity maps were produced for depths (i.e. 30 and 60 cm). Kriging and Semivariogram interpretation was conducted, and the spatial dependency of top and subsoil resistivity were moderate (48.4% and 68.6% respectively). Highly significant negative correlations were recorded in the topsoil between apparent or true resistivity and soil moisture, EC or bulk density. The obtained models were used to produce conjugated moisture and EC maps and geostatistically investigated. The spatial dependency of the top and subsoil moisture or salinity were moderate. Soil moisture and EC are the most significant factors for controlling soil electrical resistivity. The method used opens the way to the development of semi-automatic soil mapping from electrical resistivity data.

In the present study, field tests were performed using low-resistivity materials (LRMs) in different grounding system (GS) configurations to reduce the grounding resistance (GR) and assess the variation in the effectiveness of the LRMs with increases in the complexity of the GS design. Different configurations were implemented in soils with different resistivity values to determine the variation in the effectiveness of each LRM design with increases in the soil resistivity. Lastly, the percentage decrease in the GR was assessed as a function of the increase in the complexity of the GS design and the variation in the soil resistivity. The results of this study provide a useful guide for engineers and researchers who study, design, and build innovative and effective GSs by applying improved compounds for safe electrical installations.

A safe and cost-effective design of a wind turbine generator (WTG) grounding system requires accurate modeling of local soil resistivity, particularly when wind turbines are spatially distributed across a wide area with different soil types and features. In this paper, three locations at an Australian wind farm were modeled based on measured data. Four soil resistivity models were considered: uniform, multi-layer horizontal, vertical, and exponential variation with depth. Full-wave electromagnetic simulations were performed at different lightning discharge current frequencies to find the expected ground potential rise and WTG earthing impedance in the event of a lightning strike. Furthermore, the effect of frequency dependent soil parameters on the WTG earthing was analyzed, along with the effect of foundation rebar on the grounding impedance. Our results show that an accurate soil resistivity model is critical in the design of a WTG earthing system.

Onset electric field of soil ionisation is one of the basic parameters to analyse the lightning impulse performance of a grounding electrode, which has been fully investigated based on experiments on hemispherical electrode or rod-to-rod gap. Until now, there has been lack of onset electric field of rod-to-plane gap, which is the real situation for grounding electrode. In this study, the soil ionisation around the grounding electrode is studied by experiment. Method to judge the start of ionisation is discussed. Both the effect of the soil resistivity and that of the radius of the grounding electrode on the onset electric field of soil ionisation are investigated. It shows that the onset electric field decreases as the radius of the electrode increases, while increases as the soil resistivity increases. A formula to predict the onset field with respect to soil resistivity and the radius of the grounding electrode is proposed.

Studying the frequency and impulse characteristics of grounding grids is of great reference value for the optimal design of the substation. As the frequency increasing, the variation trend of the grounding resistance under different conditions is not same, which is affected by many factors. Therefore, this study focuses on the influence of grounding grid sizes, sparsity, soil resistivity, and grounding material on frequency and impulse characteristics. Based on these factors, the corresponding value of the grounding resistances at different frequencies and the impulse resistances are obtained by simulation. The trends of grounding resistances under different factors are analysed by using the dispersion mechanism. The simulation results show that the impulse grounding resistance will decrease with the increase of the grounding grid sizes and the conductor radius, or will decrease with the decrease of the spacing and the soil resistivity. With the increasing in frequency, the inductance effect of grounding resistance is strengthened, and the effect of soil resistivity and grounding grid parameters on grounding resistance become remarkable.

Lightning-induced voltages are one of the main causes of shutdown in distribution lines. In this work, attention is focused on the effects of wideband modeling of electric grounding in the overvoltage calculation along insulator strings due to indirect lightning strikes. This study is done directly in the time-domain with the grounding being represented with an equivalent circuit accounting for its dynamics. Results show that the adoption of commonly adopted simplified grounding models, such as low-frequency resistance, may lead to an underestimation of the overvoltage. According to the results, differences in the order of 25% can be found in some studied cases.

In this paper, soil resistivity and ground resistance at two different sites near an electrical substation are measured using a grounding system grid with and without rods. With the Wenner four-pole equal-method, the soil resistivity is measured at both selected sites, one of which contains wet soil while the other contains dry soil. Cymgrd simulation software is then used to determine the acceptability of these measured resistivity values by finding out the root mean square error between the measured and calculated values for both wet and dry soil sites. These values for wet and dry soil sties were found to be only 0 % and 4.92 %, respectively, and deemed acceptable. The measured soil resistivity values were then used to evaluate the ground resistance values of a grounding grid ‘with rod’ for the wet soil site and ‘without rods’ for the dry soil site, and then compared with the simulated ground resistance values. These comparisons were also found to be in good agreement. In addition, ground potential rise, maximum permissible step and touch potentials have also been estimated using the simulation software.

Transmission towers and substations are used in a variety of natural environments, coupled with the interference of the surrounding production and life, facing the test of soil corrosion. Based on the experimental data of 72 soil samples from five cities in Southern Hebei Province, the soil resistivity, soil pH value and soil moisture content were investigated, and the soil corrosion grade and soil corrosion grade distribution map were obtained. It provides a reference for the collection of soil corrosivity data in power transmission and transformation projects.

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.

It is significant to research the impulse characteristics of substation grounding grid for its optimal design and safe and stable operation. In order to obtain the impulse transient characteristics of substation grounding grid under lightning impulse current more accurately, the impulse current field test was done on a real substation grid. By monitoring the impulse grounding impedance, impulse coefficient, longitudinal current, and node potential under different test conditions, impulse characteristics curves and the effect of some influence factors are gotten, then the main zones of current dispersion and voltage drop are proposed, as well as the effective areas under different conditions are proposed combined with simulation analysis. The results show that: the impulse grounding impedance and impulse coefficient are smaller when the current is injected from the central of the grid. The main current dispersion region of the large-scale grounding grid is about 40 m around the injection point. The potential drops about 30% within 20 m around the injection point, and the change of the potential is small in the far distance. The effective area of substation grounding grid is affected by soil resistivity, and its side length is usually only tens of meters.

One of the most important parameters of the performance of grounding systems is the soil resistivity. As generally known, the soil resistivity changes seasonally, hence the performance of grounding systems, at DC and under high impulse conditions. This paper presents the performance of grounding systems with two different configurations. Field experiments were set up to study the characteristics of the grounding systems seasonally at power frequency and under high impulse conditions. A review of field testing on practical grounding systems was also presented. It was found that the soil resistivity, RDC and impulse characteristics of grounding systems were improved over time, and the improvement was higher for electrodes that have more contact with the soils.

This paper presents the soil resistivity testing results carried out at the location designated for the construction of substation 110/35/10 kV 'Zlatibor'. Testing results show that the tested soil is double-layered. Interpretation of the results of geoelectric sounding based on a mathematical model of double-layered soil shows good matching with the test results.

A method to measure ground impedance in various soil structures is described, which takes into account inductive coupling between current and potential wires. For this purpose, a family of coupling effect curves versus the potential wire length was calculated. It was found that these curves are not dependent on the current wire length and are practically identical to the same soil resistivity. The true resistance of the substation grounding is determined using received coupling effect curves, and a simple formula which subtracts the coupling effect from the measured substation grounding resistance. Practical comparative measurements were performed to validate the method.

This paper investigates the factors affecting the impulse characteristics of purposely built grounding systems. We installed 2 m × 2 m grounding systems in four different sites with different soil resistivity values. The effect of impulse polarity on soil characteristics was also investigated for different soil resistivity. A circular ring electrode was used as a return electrode in all four sites. For one of the sites, different configurations of grounding systems were installed to allow the study of the effect of ground electrode configurations on soil characteristics. The aim of this study was to quantify the effects of soil resistivity, impulse polarity, and earth electrode configurations on soil electrical properties under high impulse conditions by field measurements. The new data could be useful in understanding the characteristics of grounding systems in various factors under high impulse conditions. It is hoped that by considering these factors, it can help optimize the design of earthing systems.

The electrical conductivity (EC) of soil is generally measured after soil extraction, so this method cannot represent the in situ EC of soil (e.g., EC of soils with different moisture contents) and therefore lacks comparability in some cases. Using a resistance measurement apparatus converted from a configuration of soil microbial fuel cell, the in situ soil EC was evaluated according to the Ohmic resistance (Rs) measured using electrochemical impedance spectroscopy. The EC of soils with moisture content from 9.1% to 37.5% was calculated according to Rs. A significant positive correlation (R2 = 0.896, p < 0.01) between the soil EC and the moisture content was observed, which demonstrated the feasibility of the approach. This new method can not only represent the actual soil EC, but also does not need any pretreatment. Thus it may be used widely in the measurement of the EC for soils and sediments.