Effect Of Soil Resistivity Research Articles

Research on Electromagnetic Interference of Lightning Current on Secondary Cable in Substation

Secondary cable is an important equipment for ubiquitous power Internet of things to transmit information. When the substation grounding grid is struck by lightning, part of the lightning current flows through the shielding layer of secondary cable and produces core-to-sheath potential difference, which seriously threatens the safety of the secondary system. Fourier transform was used to decompose the lightning current in frequency domain, and the core-to-sheath potential difference at the end of the secondary cable was obtained by calculating the shielding layer current and transfer impedance at each frequency component. The effects of soil resistivity, lightning current waveform, distance between lightning stroke point and cable and grounding grid on the core-to-skin potential difference of secondary cable were studied. It is shown that the core-to-sheath potential difference of secondary cable increases with the increase of soil resistivity, the peak value, and the tail time of lightning current. The core-to-sheath potential difference decreases with the increase of the distance, while the core-to-sheath potential difference increases with the increase of conductor spacing of the grounding grid. The core-to-sheath potential difference with copper grounding grid is smaller than that with steel grounding grid.

Investigation on soil resistivity of two‐layer soil structures using finite element analysis method

Effective grounding is the most important aspect in every electrical installation because it can ensure efficient equipment operation in the event of electrical faults. Measurement data of soil resistivity is used to assess the suitability of the soil for grounding purpose and also to evaluate the structures of the soil. However, the limitation of soil resistivity measurement is various investigations on two-layer soil structures cannot be performed due to the variation of natural soil structures is limited. Therefore, in this work, modelling of soil resistivity of two-layer soil structures was proposed using finite element analysis method to estimate the depth of upper layer of non-homogeneous soil based on the measurement results from Wenner and Schlumberger methods. Also, using the proposed method, the effect of soil resistivity of each layer on the overall two-layer soil resistivity was investigated. To validate the results obtained from the proposed method, comparison between the FEA results and measured field data was made. It was found that the average error between both results is <3%. From the model that has been developed, the soil properties can be varied, which enhances the information that can be obtained from two-layer soil structures.

Modeling of different tower grounding systems using hybrid continuous circuit-trapezoidal integration method

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.

The Synthesis of Soil Resistivity and EMF of underground Cable combined with 3-D Electromagnetic Field Study in Analyzing the Grounding Touch

The earthing analysis is proposed in this paper. The effects of 3-D electromagnetic field and the influences of stray currentare considered in the text simultaneously. The activity in the high-voltage environment is risky of being injured by electricshock. The safety of personnel in and around electric power the installations has been a prime concern. Specially, the safety isgenerally in terms of the allowable touch and step voltages. These voltages are related to the earthing resistance of human foot.I ofn order to increase the safety of personnel, a high resistivity surface layer of gravel is normally existed in the substationswitchyards or other high voltage areas. The thickness of this layer will affect the calculation of the earthing resistance ofhuman foot. Thus, the effect of soil resistivity will be considered in this paper. Among them, the electromagnetic field andhumidity factors are also considered in this paper. As a result, the surface layer of gravel can be used to reduce the earthingresistance of human foot. The equivalent model of human foot was modeled by the circular plate conductor in the past. Whichconsider the beauty of the environment, most of the transmission lines are in the surface, so the transmission line generated bythe discrete current will affect the earthing resistance estimation, thus the proposed paper will consider the composition of thespecial function which is the mathematical calculus popularized by the basic theorem of calculus. On the other hand, the dampingredients, temperatures, and soil resistivity on the surface will also be considered in this paper. This paper research into theproposed method for estimating the earthing resistance of human foot and proposes an equivalent model for calculating thegrounding resistance of human foot. The comparisons of the method are also shown in this paper.

Inductive coupling on metallic pipelines: Effects of a nonuniform soil resistivity along a pipeline-power line corridor

Metallic buried pipelines sharing the same corridor with AC power lines are subjected to AC interference, potentially harmful to personnel and equipment. The inductive coupling depends, among other factors, on the physical characteristics of the soil. This work presents an analysis of the effects of soil resistivity nonuniformities spanning along the length of a corridor. The investigation is performed by assessing several realistic configurations suited to highlight the various mechanisms affecting the phenomenon. The calculations are carried out employing an ad-hoc developed numerical tool, where the network analysis is used to enforce physical constraints on a 2D finite element analysis. The obtained results show that longitudinal nonuniformities in the soil resistivity can significantly affect the induced currents, depending on the particular configuration of the power line under exam.

Investigations on the Performance of Grounding Device with Spike Rods (GDSR) with the Effects of Soil Resistivity and Configurations

In a recently published work, the characteristics of a new grounding device with spike rods (GDSR) with various arrangements of ground electrodes under high magnitude impulse currents (up to 16 kA), was investigated. In an earlier study, the ground electrodes were installed in low resistivity test media, with resistance at steady state (Rdc) values ranging from 11 Ω to 75 Ω. In practice, various soil resistivity, ranging from a few Ohm-metres to several kiloOhm-metres, have been reported in the standards. It is, therefore, necessary to investigate the characteristics of GDSR with different arrangements of ground electrodes in various soil resistivities under high impulse currents. In this present paper, six configurations of ground electrodes are used, installed at three different sites and subjected to high impulse conditions. Impulse test data of all the grounding systems are analyzed. The Finite Element Method (FEM) is used to compute the electric field values of the ground electrodes achieved. It is found that the highest electric field occurs in the presence of electrodes with the highest Rdc, soil resistivity and current magnitudes. This new data would be useful in bolstering the performance of GDSR in various types of soil resistivities, electrode arrangements and current magnitudes, which may allow for optimum design of grounding systems.

Characteristics of Earth Electrodes Under High Frequency Conditions: Numerical Modelling

The earthing segments of electrical power systems play an important role in ensuring human safety. A core function of these earthing systems is to maintain reliable operation and ensure safety for personnel and apparatus during fault conditions. Earthing electrodes can be buried in the soil to dissipate lightning and fault currents into the earth and limit the effect of any magnitude of voltage and current generated between different contact points to earth structures that may be occupied by people or sensitive electrical equipment. In order to obtain the best design of an electrical system to protect power system installations and ensure human safety against abnormal conditions, it is useful to clarify the behaviour of earthing systems subjected to variable frequency currents. In this paper, a numerical study is thus implemented to investigate the behaviour of earthing electrodes subjected to variable frequency current using the computational software program HIFREQ/FFTSESCDEGS with a uniform equivalent soil model. The effect of soil resistivity and permittivity on the behaviour of earthing electrodes is thus obtained, and the relationship between the length of earthing electrodes and their earthing responses over a wide range of frequencies from DC up to 1MHz is identified.

A Simplified Calculation Method for the Near‐Slope Laterally Loaded Pile Based on a Passive Wedge Model

When a pile is placed near the slope, the lateral loading capacity of the pile decreases significantly due to the weakening effect of soil resistance near the slope. As such, a modified soil passive wedge model for near‐slope laterally loaded piles is presented to consider the weakening effect in this paper. According to development depth of different wedges, the shapes of soil passive wedge can be classified into three sorts, so as to fully analyze the influence of the slope shape and the distance from the pile center to the slope crest. On this basis, a concept of equivalent depth is proposed considering the differences of laterally loaded piles near the slope and in the horizontal ground. Besides, the unit ultimate soil resistance, which can be obtained along the different depths of pile, is introduced into the p‐y curve of the soil, for achieving solution methods of internal force and displacement of laterally loaded piles under the slope weakening effect. The results of laboratory model and field tests on laterally loaded piles are compared with the proposed method, demonstrating its validity and accuracy. Furthermore, the influence of the near‐slope distance on the loading capacity of the pile is fully analyzed in detail, indicating the critical near‐slope distance is increasing with the increase of the undrained strength, while independent of the slope angle.

Simplified analysis of chord and brace effects on jack-up leg penetration for preloading in soft clay

The main codes of practice governing jack-up preloading presently do not consider the possibility of beneficial effects of soil resistance generated by leg chord and leg brace members as they move downwards through disturbed soil that has been squeezed past the spudcan to form part of the backfill. This paper argues that these effects can be significant for the special case of deep penetrations in soft clay. An approximate method of estimating the effects is proposed and discussed. Results are found to be broadly consistent with recent centrifuge model tests and numerical analyses. Further work is recommended to explore these potentially important and certainly complex effects.

Performance of Practical Grounding Systems under High Impulse Conditions

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.

Effects of Soil-Resistance Damping on Wave-Induced Pore Pressure Accumulation around a Composite Breakwater

ABSTRACT Zhang, J.; Tong, L.; Zheng, J.; He, R., and Guo, Y., 2018. Effects of soil resistance damping on wave-induced pore pressure accumulation around a composite breakwater. It is important to consider the potential instability of the seabed from the accumulation of wave-induced pore pressure in the design of a composite breakwater because the pore pressure within the seabed can build up considerably under wave loading, which can eventually lead to a sharp decrease in its effective stress. Because of the importance in practical engineering, many theoretical models have been developed to evaluate the magnitude and distribution of residual pore pressure. However, most of these studies treat the soil skeleton as an invariant medium, which ignores the damping of the soil strength from the reduction in the effective stress. In this study, a two-dimensional poroelastoplastic model, in which the influence of the reduction of effective stress on soil strength was considered, is proposed for investigating the a...

The Effect of a Large Backfill Area on Grounding Grid Performance

The construction of a substation will undoubtedly change the properties of any surrounding native soil. In order to study the influence of backfill material on grounding grid performance and in turn optimize that performance, current distribution, electromagnetic fields, ground, and soil structure analysis (CDEGS) was undertaken to simulate the secondary peak of the step voltage generated by a large backfill soil area. As for the various parameters of the finite soil volume, the influence of the soil length L, the edge gradient tan θ, and the resistivity ρ on the secondary peak of step voltage was researched. Then, a grounding test system was established, the selection process of the protection resistors was clarified, and the usage method of agar gel was improved. The feasibility of simulating backfill material with agar gel was verified, and the influence of resistivity and soil scale on the secondary peak of the step voltage was tested. The results show that the larger the backfill material length is, the larger the resistivity is, and the lower the peak voltage is. The effect of soil resistivity on the secondary peak will be greater when the range of backfill material is larger, which means that reducing soil resistivity can effectively reduce the secondary peak. Therefore, a smaller slope can be formed at the edge of the earthwork in the actual substation to reduce the project amount and save investment, which has a certain degree of engineering significance.

Effect of soil resistivity on the design of sacrificial anode cathodic protection system

In this research, the effect of soil resistivity on the sacrificial cathodicprotection of a pipeline steel of oil was studied. Sufficient sacrificial cathodicprotection could be obtained at various soil resistivty for different types ofanodes. High current output (2.98, 2.38 and 8.33 Amps) of Zn, Al and Mganodes respectively, are obtained at 25 ohms.cm soil resistivity. Simultaneous,for the same conditions, low numbers and large weights of anodes are requiredto satisfy protection

Overload Safety Analysis of the North Anchor Foundation of the Run Yang Suspension Bridge

As a main bearing structure of suspension bridges, the stability of anchorage foundation is very important. For the north-anchor foundation of the Run Yang Bridge, the stabilities against sliding and overturning are analyzed from the computation results of three-dimension finite element simulation models. The effect of soil resistance before and behind the pit on the stabilities is analyzed. Suppose the values of overload cable tension increase proportionally and by studying changes of the deformation and stress of anchor foundation, the basement resistance and the foundation stabilities against sliding and overturning with different overload coefficients, overload safety is obtained for anchor foundation. Based on the numerical computational results of the stability and overload analysis, some beneficial results are obtained for the stability analysis of anchorage foundation of suspension bridge.

The involvement of gibberellin signalling in the effect of soil resistance to root penetration on leaf elongation and tiller number in wheat

The concept of root-sourced chemical signals that affect shoot growth in response to drought is widely reported; in particular the role of ABA in regulating stomatal conductance has received much attention. ABA, alone, does not fully explain all the effects of abiotic stresses in the root zone on shoot architecture. An increase in mechanical impedance, which can occur on even relatively modest soil drying, results in reduced root and shoot growth, processes that are potentially regulated by gibberellins (GAs). In this study we explored the role of mechanical impedance and exogenous gibberellin (GA3) on root and shoot architecture in wheat seedlings containing the Rht-B1a (tall), Rht-B1b (semi-dwarf) or Rht-B1c (dwarf) alleles in the April-Bearded or Mercia backgrounds. Our experiments were based on the use of the sand culture system which allows the mechanical impedance of the root growth environment to remain constant and independent of water and nutrient availability. We investigated the effects of the application of exogenous GA3 to the root system. We found that impeding soil reduced leaf elongation in the tall and semi-dwarf lines, confirming the stunting effect of mechanical impedance which is widely reported. However, leaf elongation in the dwarf lines was not affected by root impedance. Application of GA3 to the roots restored leaf elongation in the tall and semi-dwarf lines growing in impeding soil, with some growth response even in the dwarf line, the longest leaves being obtained when GA was applied to impeded roots of a tall line. Both exogenous GA and root impedance reduced the number of tillers, but there was no interaction with the Rht genotype. The genetic background did not affect the results. We suggest that the GA signalling pathway has an unidentified role in the leaf elongation response to mechanical impedance to root growth.

Soil Resistance and its Impact on Tillage Depth

Abstract Currently manufactured tractors are equipped with a three-point hitch, which is used to connect semi-mounted implements to the tractor. The tractor three-point hitch is operated hydraulically, using various types of control. The most commonly used control is a force, positional and a mixed one. Each of these types of control has its specific characteristics and some advantages and disadvantages. Finally, each type of control is suitable for certain soil and terrain conditions. Particular attention was paid to a force control, which is improving the use of the tractor with a mounted implement, but on the other hand, adversely affects the uniformity of working depth of implements on soils with variable resistance. Based on theoretical analysis and experimental measurements, there has been determined the effect of soil resistance on the tillage depth, depending on initial conditions for implement deepening. Initial conditions for implement deepening are given by the tillage depth, soil resistance, and the cutting width of a plough. It was found that soil resistance strongly affects the tillage depth, and with increasing soil resistance the tillage depth decreases non-linearly. A gradual increasing of soil resistance is associated with a less-marked decreasing of the tillage depth. These facts will be further used in research, development and experimental verification of new control systems of the three-point hitch of tractors.

Behavior of Suction Embedded Plate Anchors during Keying Process

Suction embedded plate anchors (SEPLAs) allow for accurate positioning, thus providing an attractive alternative to traditional drag embedment anchors. This paper presents an analytical model for predicting the behavior of SEPLAs during the keying process, with a specific focus on predicting the loss of embedment depth as the anchor rotates from its initial vertical position to its target orientation perpendicular to the direction of loading. The soil is idealized as an incompressible, rigid-plastic material obeying an associated-flow rule. A generalized plastic limit analysis is employed to estimate the trajectories and corresponding capacities of SEPLAs under different loading conditions. The effects of soil resistance on the shank and anchor interaction with the anchor chain are also considered in the model. The SEPLA design commonly features a hinged flap; the effect of the flap is examined theoretically by comparing the solutions for the SEPLA with and without flap. Predicted solutions are shown in reasonably good agreement with some published numerical and experimental results, supporting the validity of the model.

Global buckling of pipelines in the vertical plane with a soft seabed

Offshore pipelines are usually buried to avoid damage from fishing activities and to provide thermal insulation. Provided that the buried pipelines are sufficiently confined in the lateral direction by the passive resistance of the trench walls, they may be subject to vertical buckling caused by a rise in temperature. Vertical buckling is usually called upheaval buckling because the heated pipeline is assumed to move upwards conventionally. However, the seabed may be very soft, especially where a pockmark or abyssal ooze appears. Consequently, under thermal compressive force, the pipeline may buckle downward and penetrate into the seabed because the downward soil resistance is small. In this study, we extended an analytical solution for vertical pipeline buckling on a rigid seabed to a soft seabed, and the effects of soil resistance on pipeline stability, buckling mode and amplitude are illustrated and analyzed.

Kinetic study on corrosion of steel in soil environments using electrical resistance sensor technique

Corrosion of steel in soil environments was monitored by thin film electrical resistance sensor having high sensitivity for corrosion rate measurement. The results show that this sensor made it possible to predict the long-term corrosion behavior of steel expressed by a kinetic curve obeying power law within a short period. Moreover, the effect of soil resistivity on corrosion rate measurement was eliminated using this sensor.

Efeitos de sistemas de preparo nas propriedades físicas de um Latossolo Vermelho distrófico

Os sistemas de preparo do solo e o manejo dos resíduos culturais assumem fundamental importância para a sustentabilidade dos sistemas de produção de mandioca nos solos de textura média a arenosa da região Noroeste do Estado do Paraná. O objetivo deste trabalho foi avaliar os efeitos de diferentes sistemas de preparo utilizados para o plantio da cultura da mandioca, em algumas propriedades físicas de um Latossolo Vermelho distrófico. Os tratamentos utilizados foram: plantio sem revolvimento do solo (PSR), preparo mínimo com escarificação (PM) e preparo convencional com aração e gradagem (PC). Nas camadas de 0-0,15 e 0,15-0,30 m, foram avaliadas as seguintes propriedades físicas: a densidade do solo (Ds), a curva de retenção de água no solo, a curva de resistência do solo à penetração e o intervalo hídrico ótimo (IHO). Nos sistemas de preparo com reduzida mobilização do solo (PSR e PM), foram constatados maiores valores de Ds e de resistência do solo à penetração. A curva de retenção de água foi influenciada apenas pela Ds, a qual incorporou os efeitos dos sistemas de preparo, independentemente da camada amostrada. A modelagem da curva de resistência do solo à penetração foi influenciada pelos sistemas de preparo e camadas amostradas, com maior resistência à penetração em PSR &gt; PM &gt; PC, acentuada na camada subsuperficial. Com o aumento da Ds, verificou-se redução do IHO associada aos efeitos da resistência do solo à penetração e da porosidade de aeração que determinaram, respectivamente, os limites inferior e superior de água disponível. Os valores do IHO seguiram a seqüência PC = PM &gt; PSR na camada de 0-0,15 m, não diferindo significativamente na camada de 0,15-0,30 m. O valor de densidade do solo crítica (Dsc), densidade em que IHO = 0, foi menor no PSR e PM, comparado ao PC, o que contribuiu para a menor freqüência de valores de densidade maiores que a Dsc no PC.