Horizontal Conductor Research Articles

Study on Impulse Current Dispersal and Structure Optimization of Grounding Electrode Structure of Tower

In this paper, a simulation model for soil nonlinear ionization is established, and the actual grounding electrode of the project is studied. Results show that for radial grounding electrodes, the horizontal ray conductor has better current dispersal than the middle conductor. Therefore, when improving the horizontal radiating grounding structure, short conductors should be added to the horizontal ray conductors. According to the impulse current dispersal regularity, two improved methods are proposed. After simulation, the improved grounding resistance is getting smaller, so that the improvement scheme is correct. Finally, two improved methods are applied to the engineering grounding electrode, and the potential and grounding resistance of improved grounding electrode are all reduced, so the improved method is effective.

3D Time-Domain Airborne EM Inversion with Finite-Volume Method

We investigate an algorithm for 3D time-domain AEM inversion with the finite-volume and direct Gauss-Newton methods. We separate a spatially varying secondary field from the 1D background in time-domain, and constrain the calculation to be within the small volume of influence of airborne EM secondary source, resulting in more compact discretization. To demonstrate the validity and merits of 3D inversion, we first compare the results with 1D inversion on synthetic data for a horizontal conductor and a dipping plate, which shows that both methods can well recover the horizontal conductor, while only 3D inversion can offer good recovery for the dipping plate. We apply our 3D algorithm to invert GEOTEM data obtained over the Lisheen deposit in Ireland to map the sulphides at depth and obtain similar results to 1D inversion but with better data fitting, further showing the effectiveness of our 3D inversion algorithm.

Exact and Approximate Analytical Solutions for Lightning-Induced Voltage Calculations

In this paper, we thoroughly review all analytical solutions (both exact and approximate) presented to date in the literature for evaluation of voltages induced on a lossless horizontal conductor, placed over an infinite-conductivity ground, and excited by an external field produced by either a step function or a linearly rising current, moving unattenuated and undistorted along a vertical lightning channel. We also obtain the exact analytical solution for the step-function current case in the time domain via development in the s -domain. To date, there had been three attempts to obtain such solution, all of which yielding incorrect results.

Quality of Roof-Harvested Rainwater for Irrigation of Crops by Family Farmers in Brazil

The efficiency of family farmers irrigation is conditioned by several factors such as good quality water supply. In this context, it was to evaluate the salinity and physical, chemical, and bacteriological characteristics of water harvested from roofs for irrigation of crops by family farmers in Brazil. The experiment was conducted at the Federal Institute Goiano, in Rio Verde, Goiás, Brazil. The rainwater collected on the roofs was sent through vertical and horizontal conductors to the storage tank, which has a capacity of 5000 L. The risk of salinity, pH, turbidity, conductivity, color, total dissolved solids and thermotolerant coliforms during 13 precipitation events was analyzed. Rainwater was classified as water with no salinity problem (EC < 0.7). The variation of the electrical conductivity (EC) and Total Dissolved Solids (TDS) were similar during the collection period, with mean values of 0.05 dS m-1 and 29.72 mg L-1 for EC and TDS, respectively. The pH of the rainwater presented little variation, presenting a mean of 7.37. The mean value of the color of rainwater was 11.45 PtCo L-1, while the turbidity averaged 4.89 UT. During the period of rainwater harvesting, it was observed absence of thermotolerant coliforms in all samples. It is concluded that rainwater does not present restrictions on the risk of salinity and that all physical-chemical and bacteriological parameters analyzed are within the limits allowed by Resolution 357/2005 of CONAMA, indicating the propensity of this type of water for irrigation.

Transient behaviour of grounding electrodes in uniform and in vertically stratified soil using state space representation

This investigation is devoted to study, in time domain, the transient behaviour of vertical and horizontal grounding conductors submitted to impulse current using state space representation-based transmission line method. This study has been carried out with and without incorporating soil ionisation and mutual coupling between conductor elements for soils of low and high resistivities. The results are focused on the time-domain solution of the electrode's transient potential rise and its impulse performance parameters. The results show the importance of including the mutual coupling between segments of the same electrode and soil ionisation. The results are compared with both published theoretical approaches and experimental measurements, and show acceptable agreement. This method has been applied to compute the transient potential of horizontal electrodes buried in vertically stratified soil, a situation which can occur where long horizontal counterpoise is buried in a highly contrasting soil along its length.

Evaluating the High Frequency Behavior of the Modified Grounding Scheme in Wind Farms

Wind generators are exposed to numerous destructive forces such as lightning and are therefore vulnerable to these phenomena. To evaluate the transient behavior of a wind power plant during direct and indirect strikes, modeling of all relevant components is required. Among the protective and control components of wind turbines, the grounding system is the most important element for protection against lightning strikes. This paper examines the impact of nonlinear soil ionization behavior and frequency dependency on a wind turbine in order to model a sufficient protection scheme to reduce overvoltage and make the system tolerable against transitions. The high frequency models of other equipment such as transformers, horizontal conductors, vertical rods, surge arresters and underground cables must also be taken into account to design the grounding system. Our Proposed Modified Grounding Scheme (PMGS) is to reduce the maximum transient overvoltages. We simulate the model in a restructured version of the Electromagnetic Transient Program (EMTP-RV) software to examine the effectiveness of the system. We then apply the simulated results to pair of turbines that are interconnected with a frequency-dependent cable. We carry out the simulation for direct and indirect lightning strikes. The results indicate that the MGS can lead to considerably more than a 50% reduction in transient voltages for lightning and thus leads to more reliable networks.

Characterization of buried cables and pipes using electromagnetic induction loop-loop frequency-domain devices

The detection and characterization of buried cables and metal pipes has become a key component of field surveys carried out prior to excavation work on construction sites. The very high conductivity and magnetic permeability contrast between any buried cables/pipes compared with the soil makes electromagnetic induction (EMI) instruments very useful for their detection. We have developed a seminumerical method that can be used to model the responses of this type of target. A straight horizontal conductor is equivalent to a series of magnetic dipoles, the magnitude of which can be determined in the spectral domain and then converted back into the spatial domain through the use of an inverse fast Fourier transform. Simulations and case studies allow to establish rules of thumb for the estimation of (1) the nature of the metal: the in-phase response of magnetic cables is of the opposite sign from the conducting ones, (2) the sensitivity to the target characteristic: the influence of the cable/pipe diameter is greater than that of the metal properties, and (3) the depth of the cables. The simulations also underline the role of the coil configuration: Vertical coplanar and perpendicular responses allow a more precise location of the cable/pipe, whereas the horizontal coplanar response is less dependent on the orientation. As ground truth, a known electric cable buried at a depth of 0.5 and 0.002 m in diameter is determined at 0.56 m. The first field test is related to the detection of a buried military cable from World War I, between 2.5 and 3 m below the original ground level. The second field test is related to the detection of a water pipe 0.35 m deep. The modeling technique can be applied to all EMI prospecting methods, and thus it opens the way to the correction of the disturbances generated by cables and pipes.

The profile of the electric field on the earth discontinuity with a lightning conductor

In this paper, we present some results of investigations carried out in the electric field distribution of both horizontal and vertical lightning conductors in the case of discontinuous earth. The conductors may be situated as well as in the upper or the lower earth part. The electric field distribution was determined in the case of lightning conductor situated between the high voltage rod and the discontinuity (interface) and also in the case of high voltage rod situated between the lightning conductor and the discontinuity. In some situations the electric field distribution on the plan are smaller than defined by the electro-geometrical model. We attribute this result to the great field intensity at the discontinuity, which reduce the lightning conductor discharge capture effect. This is in concordance with the results concerning the electrical strength of such air gaps without lightning conductors.

Frequency domain model for transient analysis of lightning protection systems of buildings.

A frequency domain modeling approach for lightning protection systems (LPS) of buildings is described and validated in this paper. The model is based on a 2-port transmission line representation of each conductor, and the further assembling of a network representing the complete structure. Horizontal and vertical conductors are modeled using formulas based on the complex images method, in order to take into account frequency dependence. Variation of electrical parameters with height is also considered for vertical conductors. This is accomplished by means of a non-uniform modeling approach based on conductor subdivision and cascaded connection of chain matrices computed for each segment. The results from the model are validated by means of comparisons with measurements reported elsewhere, as well as simulations using PSCAD/EMTDC.

OPTIMIZATION DESIGN OF GROUND GRID MESH OF 132/33KV SUBSTATION USING ETAP

This paper presents ground grid mesh design analysis and optimization of a 132/33kV substation. Ground grid mesh is made up of horizontal and vertical conductors connected with vertical rods buried under substation ground. The function of this structure is to effectively dissipate extremely high current generated in the system. The objective of this study is to determine the cost effective and safe ground grid mesh parameters by comparing mesh design analysis using IEEE and Finite Element Analysis (FEM) methods. The two methods are used differently to determine the ground grid mesh parameters, step & touch voltages, horizontal and vertical number of conductors, vertical numbers of rods, and final substation Resistance. Etap 12.60 software is used for the analysis. Firstly, expected maximum short circuit current of OHIA 132/33kV substation is determined. Secondly, analysis is performed to determine input and output parameters of grid mesh structure using IEEE and FEM methods. An optimized result of IEEE method is determined. Analysis of both results is shown in different tables and recommendation is given regarding the best method for the grid mesh design. http://dx.doi.org/10.4314/njt.v35i4.30

On the Image Model of a Buried Horizontal Wire

It is common practice in the engineering analysis process to use an approximate image method for the computation of the current in buried horizontal conductors (in the literature, this is often referred to as the “modified image” or “reflection coefficient” method). According to this approach, the earth/air interface is replaced by a positive mirror image of the charge and current in the conductor, and its field is multiplied by a suitable reflection coefficient. Different opinions on the validity of this approximation have been expressed in published debates, but more systematic analysis of the error introduced by this approach is not available in the literature. To establish the amount of error, we compare the computation results of the image model with the rigorous Sommerfeld integral method for a wide range of parameters. Contrary to widespread opinion, our results suggest that the modified image (or reflection coefficient) method in EFIE-based solutions (e.g., the Pocklington equation) leads to a large error (larger than 20%) in the low-frequency range for the computation of the current distribution in conductors longer than 10 m. In such a case, MPIE-based methods are preferred for use to achieve a smaller error (approximately 5%). Guidelines for the application of image models related to the conductor, earth and excitation parameters, upper frequency limit, and modeling method are presented.

Numerical Electromagnetic Field Analysis of High-Frequency Wave Propagation on an Overhead Conductor

The wave propagation characteristics on an overhead conductor in a high-frequency band were investigated based on the Wise's earth-return admittance and modified Pollaczek's (accurate) earth-return impedance in a previous paper. In this paper, the characteristics are studied using the numerical electromagnetic code (NEC), which is based on the method of moments in the frequency domain. Results computed using NEC show quite similar characteristics to those described in the previous paper, i.e., a transition between transverse electromagnetic and transverse magnetic propagation called Sommerfeld–Goubau propagation. Thus, the mode transition has been confirmed. Also, observation indicates that Wise's admittance and an accurate impedance (transmission line approach) are applicable to investigating high-frequency wave propagation on an overhead horizontal conductor, as Kikuchi pointed out.

Manufacturing technology of intra- and interchip interconnects for modern ULSIs: Review and concepts of development

Technological operations involved in manufacturing multilevel ULSI interconnections by the dual damascene (DD) method have been analyzed. Problem issues are considered, including (i) etching of porous intralevel insulation with ultralow values of dielectric constant, (ii) application of metal barrier and seed layers onto the porous surface of etched dielectric spacers, in which copper conductors have to be formed, (iii) low mechanical strength of porous dielectric spacers between copper conductors, (iv) insufficient stability of copper conductors with respect to failures as a result of electromigration, and (v) rapid growth in the resistivity of copper conductors with decreasing width, and limited possibility of compensating this factor by increasing conductor height (thickness). Possible approaches to solving these problems are proposed. According to one of these, horizontal copper conductors are formed first and then a porous dielectric is incorporated into the gaps between conductors by the method of chemical sol-gel deposition from solution by spin-on-dielectric (SOD) method on a centrifuge. The horizontal conductors can then be formed by the standard single-damascene process of copper deposition into temporal mask that is subsequently removed and replaced by the porous dielectric. According to another method, copper conductors are formed by local electrochemical deposition on the wafer surface that is preliminary covered by the barrier layer (BL), seed layer (SL), and a temporal mask, in which a pattern of conductors is prepared by etching down to the SL surface. In this case, the deposited copper conductors initially possess a textured crystalline structure, which facilitates the formation of elongated crystallites during subsequent thermal recrystallization. The surface of conductors can be also covered by local electrochemical process with an electroless barrier layer (e.g., of CoWP). Then, the BL and SL are removed and a porous ultralow-dielectric-constant insulator is incorporated into the gaps between copper conductors. The next stage of forming interconnections in multicrystal ULSIs consists of a three-dimensional (3D) vertical assembly of thinned chips by connecting them with copper conductors formed using through substrate via (TSV) technology. In order to improve heat removal from the assembly and increase its mechanical strength, the filling of vertical through channels in chips by copper is supplemented by copper plating of side edges and the formation of microbumps on crystal surfaces.

A Comparison of Ground Grid Mesh Design and Optimization for 500kv substation using IEEE 80-2000 and Finite Element Methods

An Air Insulated substation is chosen for the analysis located in Pakistan. The protective scheme installed in any substation should be fully active to ensure its proper and accurate operation in case of any fault. Ground Grid mesh used under substation ground consist of horizontal conductors connected with vertical rods. The function of mesh is to dissipate extremely high current generated in any scenario related to fault. In this regard, firstly 500KV substation is chosen for analysis of protection scheme with focus especially on Ground Grid mesh. The analysis of mesh is carried out using both IEEE 80-2000 and Finite Element Methods for the evaluation of important ground grid mesh parameters. A Software is used for analysis i.e. ETAP -12 having more enhanced features than previous versions. The problems regarding existing functioning ground grid mesh are brought to light in one case study. In second Case study, the remedies for the rectification of mesh are provided. In third, case study a new ground mesh is designed for the existing substation considering new methodologies and latest analysis techniques. In fourth case study, a new ground mesh for Ultra High Voltage Substation is designed for 750KV substation. Finally, a inter comparison is done between mesh designed using IEEE 80-2000 and FEM methods to effectively establish the efficiency and effectiveness of each method by each Case study. A recommendation is given regarding the best method to be used for the future designing of ground grid mesh of all AIS substations.

ESTIMATION OF LIGHTNING STRIKING DISTANCE TO HORIZONTAL CONDUCTOR

This paper attempts to investigate the horizontal conductor lightning striking distance estimation.An electromagnetic model was proposed to model a vertical downward lightning leader and aninfinite grounded horizontal conductor by using the charge simulation method (CSM) to calculatethe lateral striking distance. A formula between the lateral striking distance, the lightning current,and the horizontal conductor height was estimated. The proposed formula was compared withelectromagnetic model and previous formulas. By the use of a similar methodology, a horizontalconductor voltage coefficient had been proposed and estimated. The proposed voltage coefficientwas used to modify the electrogeometric model in order to study lightning striking rates of anunshielded horizontal conductor for different heights at either AC or DC voltages.

Approximate Formulas for Terminal Voltages on the Grounding Conductor

This paper proposes approximate formulas to estimate voltages on a horizontal grounding conductor. The formulas are derived in the time domain using Bewley's lattice diagram method based on transmission and reflection coefficients. The expression of the approximate formulas is simple, and the formulas are useful for engineers to carry out grounding system design for lightning protection. This paper concerns a voltage source with step waveform. A formula for an arbitrary voltage waveform can be calculated by using Duhamel's integral. Surge characteristics of voltages and an effective length of a grounding conductor are discussed using the proposed formulas. It is easy to understand experimental and simulation results of a grounding system using the approximate formulas.

FDTD surge analysis of grounding electrodes considering soil ionization

Recently, Ala et al. (2008) [7] have proposed a soil ionization model, on the basis of the dynamic soil-resistivity model of Liew and Darveniza (1974) [16], for finite-difference time-domain (FDTD) computations, and tested the validity of the model against experiments on a single vertical grounding conductor. In the model, the resistivity of each soil-representing cell is controlled by the instantaneous value of the electric field there and time. In this paper, in order to test the validity of this model more thoroughly, it has been applied to analyzing the surge responses of different grounding electrodes: a horizontal grounding conductor of lengths 8.1m and 34m, a vertical grounding conductor of lengths 1m and 1.5m, and four parallel vertical conductors of length 3.05m, buried in different-resistivity soils. The FDTD-computed responses agree reasonably well with the corresponding ones measured by Sekioka et al. (1998) [17], Asaoka et al. (2005) [19], Geri et al. (1992) [23], and Bellaschi et al. (1942) [24].

A Study of Surge Propagation Characteristics of Grounding Conductor using Approximate Formulas

The surge characteristics of a grounding conductor are quite different from those of an overhead wire. It is difficult to represent the characteristics of a grounding conductor in time domain without numerical simulation. This paper describes approximate formulas for voltage and current in a horizontal grounding conductor. The formulas are derived in time domain on the basis of the lattice diagram method, and are very simple. It is convenient from the engineer's point of view to do rough estimation of surge characteristics of a grounding conductor by the approximate formulas. Some empirical laws on the grounding have been employed without any discussions. The surge characteristics of a grounding conductor are discussed using the approximate formulas.

Instability of the magnetic fluid shape in the field of a line conductor with current

The static shape of the surface of a finite magnetic fluid volume between horizontal plates is investigated theoretically. The nonuniform magnetic field is generated by a horizontal line conductor with current, which is placed above the upper plate. The variational problem of minimum energy relative to plane surface perturbations is considered for a simply connected magnetic fluid volume. The problem is solved for arbitrary magnetic fields in the noninductive approximation with account for the gravity force and surface tension. Unstable solutions are found. The possibility of stepwise behavior in response to quasi-static changes of the current in the conductor is investigated for the surface shape of a finite magnetic fluid volume.

Crustal and lithospheric scale structures of the Precambrian Superior–Grenville margin

Abstract The lithosphere beneath the margin of the Archean Superior and Proterozoic Grenville provinces was investigated with a northwest–southeast oriented, 650-km-long profile of 40 magnetotelluric stations. Dominant geoelectric strike azimuths of N45°E and N85°E were defined for the crust and the lithospheric mantle respectively. A 2-D isotropic resistivity model derived using the crustal strike images resistive Laurentian margin rocks dipping southeast to the base of the crust, bounded to the northwest by the Grenville Front, and to the southeast by the Central Metasedimentary Belt Boundary Zone. The observation is in contrast to conductive mid to lower crust elsewhere in the region. A 2-D isotropic resistivity model determined using the lithospheric mantle strike azimuth reveals an extremely resistive region in the upper 100 km of the mantle lithosphere of the northern Grenville Province. The geometry of this body, which includes a well-defined base and southeast dip, suggests that it is Superior lithosphere. A sub-vertical conductor, located approximately 50 km along strike from the Mesozoic Kirkland Lake and Cobalt kimberlite fields, is interpreted to be due to re-fertilization of an older mantle scar. The resistivity model includes a horizontal conductor at 160 km depth beneath the southern Superior Province that is possibly the resistivity signature of the lithospheric–asthenospheric boundary.