Horizontal Conductor Research Articles

Effects of base frequency, duty cycle, and waveform repetition on transient electromagnetic responses: Insights from models of a deep-buried conductor

In transient electromagnetic (TEM) methods, the recorded data for the magnetic field and its time derivative are influenced by the waveforms of the transmitting current. These waveforms are characterized by parameters such as the durations of the turn-on, steady, and turn-off stages as well as the base frequency, duty cycle, and waveform repetition. The full-waveform effects encompass all counteracting effects observed in TEM responses that arise from using a waveform other than a step-off or step-on waveform. To address these complexities, a 3D forward-modeling solver is developed for TEM methods, capable of calculating TEM responses while considering realistic waveforms with considerations for base frequency, duty cycle, and waveform repetition. The effects of these parameters on the magnetic field and its time derivative are investigated through numerical experiments using models involving deep-buried horizontal and vertical conductors. The results indicate that as the waveform period increases, there is a significant improvement in the detection and discrimination capability of the magnetic field for perfect conductors with a conductivity of 1000 S/m or higher in the models presented in this study. However, the improvement in the time derivative of the magnetic field is minimal. Interestingly, the improvement in the magnetic field and its time derivative does not indicate a consistent trend as the conductor conductivity increases. In addition, a novel equivalence phenomenon is uncovered in the magnetic field and its time derivative data. The results also suggest that as the number of waveform repetitions increases or the duty cycle decreases, the discrepancies between the recorded TEM responses at the two off-time stages within a single period gradually diminish. However, the influence of the full waveform on the TEM responses becomes more pronounced with an increasing number of waveform repetitions or a decrease in the duty cycle, especially in terms of the magnetic field.

FDTD Analysis of Electric Field and Step Voltage in a Clay‐Wall House Struck by Lightning

The density of lightning flashes is quite high in Rwanda and its neighboring countries in Africa. In rural areas of these countries, there are still many clay‐wall houses. Sometimes people in clay‐wall houses are fatally injured by direct lightning strikes to the houses. In this paper, the electric field in a clay‐wall house and the step voltage on the floor, associated with a direct lightning strike to the house, are analyzed using the finite‐difference time‐domain (FDTD) method. Also, the electric field and the step voltage in the same clay‐wall house but with a horizontal air termination conductor connected to buried vertical bar earth conductors or a square ring earth conductor via bare or insulated down conductors are analyzed using the FDTD method. It has been shown that installing these protection systems reduces the inside electric field and the step voltage on the floor particularly if insulated down conductors are employed. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Ground Resistance Estimation for a DC Converter Station: Theory versus Experiment

This paper is aimed at proposing a calculation model for the ground resistance of a grounding scheme servicing a high-voltage direct-current converter station. The method is based on the equivalence of current conduction and electric field from the grounding scheme through the surrounding medium. The grounding scheme is composed of three concentric ring electrodes supported by two horizontal conductors and eight vertical rods. The calculated ground resistance is 4.8 Ω against the experimental value of 5 Ω with an error of 4.2%. The calculated ground resistance value agrees reasonably well with that of 4.7 Ω as obtained using CYMGRD software (version 7.0). The calculated surface-potential values over the ground surface agreed reasonably well with those measured experimentally, with an average deviation not exceeding 6.5%. This study is designed to investigate how ground resistance is decreased by the increase in the scheme parameters, including the rods’ diameter and length, as well as the radius of the inner and outer rings. The dependency of the ground resistance on the soil type is also investigated.

Unique laboratory “Currents in the ground”

A brief description of the scientific laboratory is given, which has become a flagship in the field of electrical energy, which made it possible to obtain unique results on grounding and electrical safety, which were included in state regulatory documents. It is shown that a well-known scientific school has been created in the laboratory for the study of processes in grounding devices of electrical installations. The laboratory was founded in 1971 and has not been described previously. The article shows the main building in the form of a two-story building and a nearby stack-type pulse voltage generator for a voltage of 1,250,000 V. The circuit allows for reconnecting capacitors on floors to obtain different capacitances in the discharge. To connect to the grounding device under study, a portable overhead line with split wires is used. A map of grounding fields on the laboratory territory is provided. This allows you to design almost any design of a grounding device. Fields of vertical and horizontal grounding conductors of various lengths are used; fields of complex mesh grounding conductors; groups of single vertical electrodes of different lengths. The laboratory has several sets of self-powered electronic high-speed oscilloscopes, shielded and isolated from ground to avoid interference. The range of research questions can be significantly expanded by using already installed objects: an experimental overhead line with a voltage of 220 kV on nine reinforced concrete supports; cable line 600m long; a dynamic and thermal test stand, equipped with a circuit for obtaining industrial frequency currents of up to 4 kA at a voltage of 0.4 kV; 120 linear meters of reinforced concrete trays were laid on the field of a complex mesh grounding device for laying communication and control cables in them; two additional pulse voltage generators 1,600,000 V and 1,000,000 V (the latter allows transportation to full-scale test sites outside the laboratory); test transformers IOM-100/100.

A circuit model of electrical wiring nearby building structure for lightning surge analysis

AbstractA model expressing beams, pillars, and electrical wiring in a building for lightning surge simulation by circuit analysis method is proposed in this paper. The proposed model expresses the self‐surge impedance of the electrical wiring as a function of the distance between conductors and the radius of the electrical wiring. The mutual impedance is expressed by the distance between the surfaces of a structure and a nearby wire instead of the distance between the conductor centers. In the case of two conductors having far different radii in proximity, the distribution of electromagnetic fields around the two conductors is similar in horizontal and vertical arrangements. Thus, the electrical wiring nearby pillars can be treated as a horizontal conductor. The circuit analysis results show that the voltage difference generated between the structure and the electrical wiring is calculated more precisely by the proposed model than by the conventional model.

Analysis of grounding system transient with consideration of soil ionization and mutual coupling effect

The grounding system of an electrical substation provides safety to both operator and equipment. The lightning current waveform has a major influence on the dynamic performance of ground electrodes. If lightning current is large enough, soil will be ionized, which will have a great effect on the transient performance of the grounding system. Many numerical models have been developed to evaluate the transient performance of grounding system, still it is a challenging task to analyze the impulse behavior of grounding system efficiently. In this paper, the transient behavior of grounding systems with consideration of nonlinear and dynamic effects of soil ionization is presented. Grounding systems such as vertical rod, horizontal conductor and grounding grid buried in the homogeneous soil are considered as case study. Proposed model is the combination of circuit theory approach and method of moment with consideration of frequency-dependent impedance and mutual coupling effect between the conductor segments. Self and mutual component of inductance and resistance are considered in the analysis. Initially, transient performance of grounding system is analyzed for single vertical rod, horizontal and square grounding electrodes, further it is extended for vertical rod (more than one), horizontal conductor and grounding grids with different configurations. The analysis of grounding system with the consideration of mutual coupling effect is compared with devoid of mutual coupling, and differences between them are evaluated. For validating the developed method, simulated results are compared with the results reported in the literature, and good agreements are found. Analysis shows that the grounding impulse impedance decreased with increasing the magnitude of injected current. Developed method will help to improve the modeling of simple as well as complex grounding system buried in homogeneous soil.

Optimal design analysis of substation ground grid mesh

Substations are grounded by means of earth-embedded electrodes in order to provide safety during normal or fault conditions. Electric substations are effectively grounded to guarantee the proper operation of electrical devices, minimize the likelihood of flash-over during transient conditions as well as dispel lightning strokes. A structure is termed grounded if it is electrically bonded to earth-embedded metallic frames. The earth-embedded metallic frames provide a conducting pathway of electricity to the earth and it is called a ground grid system. Substation ground grid mesh is comprised of vertical and horizontal conductors as well as vertical rods buried beneath the substation ground. Electric current flow through the human body is hazardous. Therefore, ground grid systems should be designed such that the likely electric body current in an operator or passer-by should not exceed the standard defined limits under any foreseeable harmful circumstances and as well provide protection of equipment. The objective of this study is to determine substation, safe ground grid system parameters as well as the cost-effectiveness of designing substation ground grids by comparing the IEEE Std. 80-2000/2013 and the Finite Element Method (FEM). ETAP 16.0 Power Tool is employed in carrying out this analysis. The substation expected maximum short circuit current is stated. The design analysis using both methods is presented separately and suggestions are made with reference to the most cost effective and safest method for the effective designing of the substation ground grid system.

Influence of photovoltaic support on lightning transient under direct lightning strike

• A new transient circuit model for calculating the transient response of PV support is developed. • The transient overvoltage caused by the mode of air-termination rod and lightning strike point are investigated. • The influences of additional leg, tile angle and equipotential bonding have been studied. • Four types of PV supports are chosen and their lightning transient responses under direct lightning strike are comprehensively investigated. Due to the large-scale installation of photovoltaic (PV) plants in open areas, PV plants is exposed to lightning strike at a high risk. The influence of PV support on lightning transient under direct lightning strike is investigated in this paper. Firstly, the PV support composed of multiple branches is classified into vertical conductor, horizontal conductor and oblique conductor. Their wave impedances are individually derived. Considering the air-termination rod and earthing system, four types of PV supports are chosen and their lightning transient responses under direct lightning strike are comprehensively studied. It suggests that the transient response is heavily dependent on the number of grounding legs. The greater the grounding legs, the lower the overvoltage. The equipotential bonding provides additional routes for the discharge of lightning current. Its presence would minimize the voltage but increase the risk for the entire PV system. The additional auxiliary leg also plays a role. The non-isolated air-termination rod is suggested install at the symmetrical center of the PV support from the perspective of discharging the lightning current.

ARTIFICIAL NEURAL NETWORK MODELS FOR ESTIMATION OF ELECTRIC FIELD INTENSITY AND MAGNETIC FLUX DENSITY IN THE PROXIMITY OF OVERHEAD TRANSMISSION LINE.

This paper considers the application of artificial neural network (ANN) models for electric field intensity and magnetic flux density estimation in the proximity of overhead transmission lines. Specifically, two distinct ANN models are used to facilitate independent estimation of electric field intensity and magnetic flux density in the proximity of overhead transmission lines. The considered ANN approach is systematically evaluated under different scenarios. An example of an overhead transmission line with horizontal phase conductor configuration is used to enable a direct comparison of the electric field intensity and magnetic flux density estimates generated by the two ANN models to measurement results obtained over the lateral profile. Further investigation of ANN models involves an extensive study whereby 13 different overhead transmission lines of horizontal configurations are used as the basis for comparing measurement results to estimates provided by the ANN models. In this study, the performance analysis of the ANN models was evaluated using coefficient of determination and root mean square error. The obtained results demonstrate that the considered ANN approach can be used to estimate the electric field intensity and magnetic flux density in the proximity of overhead transmission lines.

Soil impulse ionisation model based on dynamic changes of electric field

Soil ionisation has an important influence on impulse characteristics of grounding conductor. This paper introduced improvements to an existing soil ionisation model considering the influence of electric field on the change of soil resistivity, while soil resistivity is not directly dependent on soil electric field. The validity of improved soil ionisation model was verified by surge response of vertical conductor in uniform soil and horizontally stratified soil. Furthermore, the impulse experiment was carried out on horizontal conductor in soil with finite volumes. Based on experimental configuration, the corresponding calculation model was built, and calculated results were in good agreement with experimental results.

Динамика несимметричного проводника с токами Фуко

Цель настоящей работы ‒ измерение силы, действующей на проводник, находящийся в переменном магнитном поле. Поскольку токи Фуко являются индукционными, средняя за период осцилляций переменного магнитного поля сила, действующая на проводник, должна быть равна нулю. На основе этого положения проведены подробные измерения изменения веса проводника при включении магнитного поля. Изучен характер магнитного поля, создаваемого источником, что позволило определить область, где магнитное поле однородно. Показано, что даже при расположении несимметричного проводника в области, где поле однородно, средняя сила, действующая на проводник, не равна нулю. Особое внимание обращено на зависимость изменения веса проводника в форме половины кольца от угла наклона по отношению к горизонтали. Это дало возможность отделить фоновую составляющую от силы Абрагама, представляющей собой силу реакции излучения на проводник. Отмечено, что максимальное значение измеренной силы Абрагама существенно выше известных экспериментальных значений и наблюдается при горизонтальном расположении проводника с цилиндрической поверхностью, расположенной снизу.

Simple Formula for Surge Impedance of Horizontal Grounding Conductor

Horizontal grounding conductor is often used to obtain low grounding resistance. Simulation results of voltages and currents in a circuit including a grounding system are sometimes different from measured results because the grounding resistance depends on temperature and water content. Lightning surge characteristics of a grounding conductor are important for lightning protection design. Simple formulas for the surge characteristics of the grounding conductor are useful for engineers to estimate the influence of parameters of grounding system on lightning overvoltages. This article describes measurement results of the surge characteristics of grounding conductors for various conductor lengths and terminal conditions. This article proposes simple formulas for surge impedance and propagation velocity of horizontal grounding conductor based on the measured results. A simple equivalent circuit of grounding conductor is described. The constants of the equivalent circuit are obtained using the proposed formulas. Simulation results of voltage on a grounding grid using the proposed formulas and the equivalent circuit of grounding conductor are compared with experimental results.

Research on the Temperature Distribution of the Hollow Conductors in the Self-circulating Evaporative Inner Cooling System for High Power Rectifier Equipment

In the evaporative inner cooling system for high power rectifier equipment, the thyristor and quick fuse are both cooled double-sided via hollow conductors. Different from the previous study on the system with single structure, the self-circulating system for high power rectifier equipment has composite structure. Then the system with composite structure may show different heat transfer characteristics. So in this paper, the temperature distribution of the horizontal and vertical hollow conductors in the self-circulating system was studied through theoretical analysis and simulation.

Determine the Electrode Configuration and Sensitivity of the Enclosure Dimensions When Performing Arc Flash Analysis

Arc flash hazard prediction methods have become more sophisticated because the knowledge about arc flash phenomenon has advanced since the publication of IEEE Std. 1584-2002. The IEEE Std. 1584-2018 has added parameters for more accurate arc flash incident energy (IE), arcing current, and protection boundary estimation. The parameters in the updated estimation models include electrode configuration, open circuit voltage, bolted fault current, arc duration, gap width, working distance, and enclosure dimension. The sensitivity and effect changes of other parameters have been discussed in the previous literatures. This article explains the fundamental theory on the selection of electrode configurations and performs sensitivity analysis of the enclosure dimension that have been introduced in the IEEE Std. 1584-2018. According to the newly published model for IE estimation, the IE between vertical conductors inside a metal box (VCB) and horizontal conductors inside a metal box (HCB) can differ by a factor of two with other parameter constants. Using HCB as the worst-case scenario to determine the personal protection requirements may not be the best practice in all circumstances. This article provides guidance for electrode configuration selection and a sensitivity analysis for determining a reasonable engineering margin when actual dimension is not available.

3D finite-volume time-domain modeling of geophysical electromagnetic data on unstructured grids using potentials

Unstructured grids are capable of faithfully representing real-life geologic models and topography with relatively few mesh cells. We have developed a finite-volume solution to the 3D time-domain electromagnetic forward modeling problems using unstructured Delaunay-Voronoï dual meshes. We consider the Helmholtz equation for the electric field and a combination of the Helmholtz equation and the conservation of charge equation for the magnetic vector (A) and electric scalar ([Formula: see text]) potentials. The [Formula: see text] formulation requires initial values for A that can be obtained by solving the magnetostatic problem. We use backward Euler time stepping to advance the electric field and the potentials in the time domain. When using the potential method, the electric and magnetic fields are calculated from [Formula: see text] solutions. To obtain consistent potential solutions at different time steps, we enforce the Coulomb gauge condition, using implicit and explicit methods. We validate the proposed method with a simple 3D conductive block model and with a comparison with other numerical methods. By using [Formula: see text] potentials, it is possible to decompose the electric field into galvanic and inductive parts, which is helpful in understanding the physics behind the behavior of the electromagnetic fields in the ground. We use vector plots to visualize the decomposed electric fields for horizontal and vertical thin conductor models with inductive loop sources. This allows the interplay between inductive and galvanic parts as the electric field and current density develop with time to be visualized.

Effects of cost optimised grid configuration on earthing system performance: a comparative assessment

This study presents the comparative analysis of earthing grid configurations to determine the optimum design in terms of safety parameters and cost for 66/11 kV substation. For different grid configurations, a fixed earthing area of 9000 m2 was considered. Rectangular, triangular, L-shaped and T-shaped grids buried in two-layer soil model were considered for this study. Three methods, i.e. ANSI/IEEE standard 80-2000, finite element method and genetic algorithm, were used to design the grids. All safety constraints as mentioned in the IEEE standard were followed for designing the earthing grid. A new mathematical cost function (CF) was proposed for designing an effective and economic L-shaped, T-shaped and triangular earthing systems. The CFs used in this study include grid depth, dimensions of earthing rod and horizontal conductor, number of rods and conductors, revetment and excavation area. The economic earthing grid obtained through the proposed method reduces the total cost related to grid materials, installation and excavation. Analysis also showed that the rectangular grid showed preferred results in terms of safety parameters while the triangular grid showed optimum cost design for the earthing system under study. Good agreements were found with the rectangular earthing grid in comparison with triangular, T-shape and L-shape configurations.

Hybrid continuous circuit‐trapezoidal integration method analysis of multi‐cross structure of grounding system

An essential requirement to improve the lightning performance of transmission line is the achievement of low impulse impedance of grounding system, which diminishes the occurrence of the external overvoltages. In this study, for the first time, a multi-cross structure used as transmission line tower-footing grounding system is investigated by means of hybrid continuous circuit-trapezoidal integration method (HCCTIM). It is discovered that the angle of minimum impulse impedance or the optimal structure of multi-cross grounding system is mainly dependent on the branch length compared to the effective length of a single horizontal conductor. Furthermore, in the current work, the trapezoidal integration method is used to solve the continuous circuit equations which elements are extracted from electromagnetic integral method, called HCCTIM. Coupling elements and soil ionisation are considered in this model. This method is an accurate, simple, and less time-consuming computational method. The comparison of the results with measurements, other recent simulations and CDEGS software, satisfactorily validate the proposed method.

Research on the Feasibility of the Self-circulating Evaporative Cooling System with Composites Structure for High Power Rectifier Equipment

Self-circulating evaporative cooling system is safe, effective and energy-saving. It has advantages compared with the traditional cooling technology. So it provides a new cooling method for high power rectifier equipment. Then take an example of the three-phase bridge full-controlled rectifier, a new cooling system with composite structure and non-single heat loads was proposed. Through analysis on the circulation mechanism and operation characteristics, the feasibility of the self-circulating evaporative cooling system which is composed of horizontal and vertical hollow conductor was studied in this paper.

Shape Proposal and Electric Field Distribution of Horizontal Lightning Conductor

Horizontal lightning conductor is installed horizontally on the top or side of the building. It uses specific materials and wires or rods of minimum thickness. In the horizontal conductor system, a horizontal conductor is laid on top of the building to be protected and absorbs the lightning through it. And the lightning current is safely discharged to the earth through the conductor connecting this to the ground. The starting point of the discharge current of the lightning strikes depends on the sectional shape of the horizontal conductor. In this paper, a new shape is proposed through electric field analysis in order to find the optimum shape that can lower the discharge start voltage according to the sectional shape of the horizontal conductor. Two - dimensional electrostatic field analysis was carried out for the electric field analysis, and the maximum electric field was analyzed at the upper part of the horizontal conductor for comparative analysis. This study is considered to be helpful in designing or constructing horizontal conductors.

EMP Coupling to a Straight Conductor Above Ground: Transmission Line Formulation Based on Electromagnetic Reciprocity

A simple model for coupling of an electromagnetic plane wave incident on a conductor above ground has been developed using reciprocity theory, providing some advantages as compared to the conventional transmission line approach. The model is developed using a semi-infinitely long single conductor above a lossy ground plane and connected by an arbitrary load impedance to a vertical grounding conductor. This configuration corresponds to the worst-case wave coupling, because it leads to a line induced current larger than in the cases of finite and multiconductor lines. A frequency-domain Thevenin equivalent model is developed to relate the incident wave amplitude to the voltage across a generic load, connected at any point on the vertical conductor. The application to the threat analysis of a high-altitude electromagnetic pulse impact on a power transmission line is discussed by considering the time-domain solution (via inverse Fourier transform) for an incident EMP fast-rise transient (E1) waveshape, following the standard IEC specifications. For typical high-voltage power line load impedances, it is shown that voltage magnitudes in the MV range can be induced across the line termination, in the case of a wave with a near-grazing incidence angle and with wave vector aligned along the horizontal conductor.