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The groundings of the power distribution, signaling, and power systems of a railway system are individually performed to realize fail safe, and the groundings are often installed in close proximity. Thus, when a grounding electrode is invaded by a lightning current, its ground potential rises together with the potential of the adjacent grounding electrodes; hence, there is a possibility of a large overvoltage being applied to the connected devices. In this paper, we have investigated the potential spread between two rod-shaped electrodes widely used in the grounding of the power, signal, and distribution systems of a railway system using the finite-difference time-domain method. The results of this paper are organized in such a way that the extent of the potential spread to the neighboring grounding electrodes can be understood from information such as the grounding resistivity at the installation location of the ground electrode and the wavefront duration of the lightning current, and these findings will be useful for grounding design. We also investigate the effect of the insulator between two neighboring electrodes to prevent the potential spread. [ABSTRACT FROM AUTHOR]

Unlike most electrical systems, electrical submersible pump (ESP) system grounding has its unique feature: it must be divided into two zones, i.e., surface and downhole zones, grounding practices for the two zones are significantly different. In this paper, the current practice and future trend for ESP system grounding is presented, which is based on an extensive literature review, including the industry practice, published technical papers, and the patent search. This paper will be extremely useful for field engineers and ESP system design engineers to understand requirements, techniques, and future development directions for ESP system grounding. [ABSTRACT FROM PUBLISHER]

This paper applies a rigorous electromagnetic model to determine the transient distribution of potentials along a substation earth grounding grid subjected to lightning currents. The obtained results show that, in the initial period of the transient, equipment pieces that are earth grounded at distinct points of the grid and are electrically linked (for example, by aerial communication cables) experience impulsive loop currents. Such loop currents can cause equipment malfunctions, failures, and damage. A remarkable conclusion of this paper is that such loop currents can reach substantial values even in the case of soils of low resistivity. Some practical aspects are highlighted in order to reduce the risks due to the nonuniform distribution of potentials along earth grounding. [ABSTRACT FROM AUTHOR]

This paper presents a new approach to wideband modeling of tower footing grounding impedances. Appropriate representation of transmission tower footing impedances is essential in electromagnetic (EM) transient simulations for proper evaluation of overvoltages and flashovers in the system during fast-front transient conditions such as lightning strikes. In this paper, a field solver is used to precisely model the most popular types of tower footing grounding systems, i.e., rods, counterpoises, and ring electrodes, for a variety of dimensions and soil parameters. Results are stored in a lookup table and used for generating frequency-dependent models that are exported to EM transient simulators. The table and model generation tool can be used by utility companies to model tower footings while taking into account local variations along the right-of-way, such as local variations in soil resistivity. The presented examples show close agreement of results of lightning studies using developed electrode models included in EM tools, e.g., PSCAD, EMTP-RV, and ATP-EMTP. A sensitivity study shows that the maximum voltage at the tower top during a direct lightning strike can be up to 19% higher when using the adopted modeling procedure, as compared to a standard approach of using a fixed resistor equal to the power frequency resistance. [ABSTRACT FROM AUTHOR]

This paper presents a technical/economic comparison between remedial measures aimed at improving the lightning performance of an existing Italian three-phase 150-kV overhead line. The line is characterized by a very high back-flashover rate (BFOR), due to large grounding resistance values. Two countermeasures are proposed: grounding system improvement with additional vertical rods and line metal oxide surge arrester (MOSA) installation on one or all phases. A Monte Carlo ATP-EMTP procedure developed by the authors, which takes into account both the tower grounding nonlinear transient response due to soil ionization and MOSA nonlinear response, has been applied to evaluate and compare the effectiveness of the proposed countermeasures. The installation of MOSA on all phases is technically the best option, but it is relatively expensive. Tower grounding improvement and MOSA installation on the lower phase yield very similar BFORs: the economic comparison strongly depends on tower's accessibility and soil nature. [ABSTRACT FROM AUTHOR]

This paper presents an overview on the response of grounding electrodes subject to lightning currents with a focus on industrial environment. The influent parameters of lightning currents are discussed, and the lightning response of electrodes is analyzed based on experimental and simulated results to provide the fundamental knowledge required in this field for engineers working in industrial plants. [ABSTRACT FROM AUTHOR]

In this paper, an analysis of experimental results on the behavior under impulse currents of various grounding electrodes: rod and horizontal electrodes, a ground grid, and tower footings, is presented. The parameters used for analyzing transient performance are reviewed, and the differences are highlighted based on test data. The analysis is extended to the following: 1) to quantify the effect of impulse shape; 2) to quantify the effect of current magnitude; 3) to compare low-frequency and impulse performances; 4) to compare impulse and high-frequency performances; and 5) to examine the effects of the test setup on measured results, e.g., in the case of field tests, the effect of current return leads, and proximity and extent of return electrodes. A generalized impulse index is introduced to help elucidate the differences between different parameters used for the analysis of transient test results on ground electrodes. It is found that the analysis of test data based on different parameters may lead to different assessments of impulse performance. The results also show that the impulse parameters used for the analysis of test data can be influenced by several factors such as electrode length, impulse current rise time, and experimental setup. In addition, variable-frequency test results are analyzed by introducing a “harmonic coefficient” which quantifies the deviations of the harmonic impedance from the low-frequency resistance over different frequency ranges covering the entire lightning frequency spectrum. Significant variations of the harmonic coefficient with frequency were observed, highlighting the importance of taking the frequency dependence of soil properties when modeling the impulse and high-frequency behavior of grounding systems. [ABSTRACT FROM AUTHOR]

Grounding is essential to build effective lightning protection design for electric power equipment. The main role of grounding is to disperse abnormal current such as that from lightning into the soil via a grounding electrode. When the lightning current flows into the grounding electrode, the electrical potential of the electrode rises, and overvoltage arises between the equipment connected to the grounding electrode and nearby equipment. The overvoltage causes equipment to breakdown or malfunction. An effective grounding electrode controls the overvoltage at the equipment in a lightning strike and can ensure the normal operation of electrical equipment. The most common grounding electrodes are the vertical grounding rod and the horizontal buried electrode. A property of these grounding electrodes, known as effective length, has been investigated by many researchers. Many formulas to express effective length have already been proposed, all of which are determined heuristically on the basis of formulas that approximate the property from experimental or analytical test results; they are not formulas derived based on the physical phenomenon of grounding. In this paper, we first report on the results of the derivation of a formula for effective length based on the propagation velocity within the soil and the depth of penetration of the lightning surge into the soil. The aforementioned formula still has unknown constants. To decide those parameters, the finite-difference time-domain method is utilized. [ABSTRACT FROM PUBLISHER]

Grounding is the fundamental measure of lightning protection for power systems, industries, and buildings, and the lightning impulse behavior of grounding electrodes plays a very important role. How to correctly consider the lightning impulse characteristics of grounding electrodes is the fundament in lightning protection design. This paper summarized the progress in lightning impulse characteristics of grounding electrodes with soil ionization, including the images of soil ionization, the residual resistivity of ionized soil, the critical breakdown electrical field, the impulse breakdown delay characteristics of soil, and the impulse breakdown mechanism of soil. Finally, the numerical simulation methods for lightning impulse characteristics of grounding electrodes are classified, and some key performances of grounding electrodes under lightning impulse were presented. [ABSTRACT FROM AUTHOR]

In this paper, the simulation of towers cascade under lightning surge conditions is presented. Finite-difference time-domain method is used to solve both the Maxwell's and telegraph equations. Maxwell's equations and the time-domain resistivity model of Darveniza are used to simulate the nonlinear behavior of the grounding system. Telegraph equations are used to describe the propagation in the overhead lines. Multiple ionizations, on different grounding electrodes belonging to various towers, can be implemented simultaneously, without making assumptions on the shape of the ionized areas. [ABSTRACT FROM AUTHOR]

This paper studies the electric response of a common lattice tower when it is hit by a lightning stroke. Although some studies have been already done about this subject, the novelty of this one lies in the usage of a highly accurate electric model of an actual lattice tower. This model allows to calculate the impedance variation with different frequencies by using an adaptation of the well-known method of moments. Moreover, the authors also analyze how the impedance is affected when the grounding parameters and the connection to ground conditions are modified. These results are lately used to explain the electric behavior of the tower under two kinds of lightning impulses and different grounding configurations. [ABSTRACT FROM PUBLISHER]

In recent years, the ripple effects of damage to home electrical appliances of private residences near a cellular phone base stations due to lightning strikes on the station have become a problem. The damage is primarily caused by the ground potential rise of cellular phone base stations during lightning strike. To prevent such damage, instead of conducting lightning current from the grounding system of cellular phone base stations to the ground, a deeply buried grounding electrode that releases the lightning current deep into the ground through a separate grounding line has been employed in some cellular phone base stations. However, this technique is not versatile and may lead to a large overvoltage in the insulated conducting wire of the deeply buried grounding wire and may cause a dielectric breakdown, thus causing concern that this technique can no longer fulfill its role. Therefore, in this paper, we study the effectiveness and problems of employing deeply buried grounding electrodes using the finite-difference time-domain method. [ABSTRACT FROM AUTHOR]

This paper utilizes CDEGS software to calculate the transient ground potential rise (GPR) in a commercial building, with a base of 39\ \m\ \times 13\ \m and a height of 21 m, during direct lightning strokes. The influences of soil resistivity, location of the lightning strike point, and wave shape of the lightning current on the transient GPRs of three scenarios for the building are analyzed. Such scenarios within the building include the following: 1) devices are grounded independently; 2) devices are grounded via vertical ground electrodes that are connected to each down conductor fixed on the outside of the building; and 3) devices are grounded via a ring ground electrode that is sited around the periphery of the building. The results show that the ring ground electrode provides effective lightning protection for the building under lightning and, therefore, is recommended. [ABSTRACT FROM AUTHOR]

In conducting analysis of systems that have failed as a result of lightning and transients, the authors have observed repeated incidences associated with corrugated flexible tubing (CFT). Corrugated stainless-steel tubing is one of a group of flexible pipes used for low-pressure gas. This tubing is increasingly used not only in processes but also in laboratories, warehouses, and office facilities for distribution of heating gas. These products were designed with mechanical properties in mind. The design does not directly consider electrical characteristics; however, since these piping systems are constructed of conductive metals, they will have electrical properties. Despite the observed tendency of this piping to fail during lighting and transient events, there has been no coherent hypothesis for the phenomenon of CFT failure due to lightning. This paper will address the electromagnetic response of these tubing systems. Ten electrical properties are correlated to the impact of lightning and transients on materials such as corrugated tubing. [ABSTRACT FROM AUTHOR]

Antennas, if present on roofs, are, usually, the most prominent part of edifices. Grounding their metal supports is, generally, considered an effective means of protection of the structure against the effects of lightning strokes, eventually "attracted" by the antennas themselves. The antenna's mast and the down conductor are incorrectly assumed capable of safely draining to ground the lightning current flowing at the point of strike. This, supposedly, would prevent both hazard for people and damage to the building and electrical equipment situated inside of it. This paper will substantiate how the sole grounding of the antenna's mast can instead result in lowering the safety of the edifice, and, thereby, expose users to the hazard of dangerous electrical sparking (flashover) and possible fires. [ABSTRACT FROM AUTHOR]

Spacer cable provides compact distribution of three-phase power. However, the close proximity of the phases to each other and the neutral carrier wire results in very high fields under lightning conditions. The concept of spacer cable is based on the assumption that the neutral carrier wire is grounded at each pole with an earth resistance no greater than 25 Ω. In many areas, this assumption is far from met. In this paper, we compute lightning-induced overvoltages for long lengths of spacer cable including the effect of every lightning arrester, transformer, etc., on the line and using measured ground resistances, for a range of lightning currents and rise times. [ABSTRACT FROM AUTHOR]

The probability of nuisance operations of distribution fuse links due to lightning-induced current surges is the subject of much discussion today. This discussion is driven, in part, by the practice of moving the surge arrester to the transformer tank to improve overvoltage protection of the transformer. One consequence of this practice is that the probability of nuisance operation of the fuse link protecting the transformer will increase significantly unless larger fuse-link sizes are employed or unless high-surge-capacity fuse links are used. Section II of this paper describes a method for determining the probability of nuisance operations of fuse links under various conditions. Section III describes one utility's experience with moving the arrester to the transformer tank and also its success with high-surge-capacity fuse links. [ABSTRACT FROM AUTHOR]

Strong circumstantial evidence suggests that lightning has initiated methane explosions in abandoned and sealed areas of underground coal mines. The Mine Safety and Health Administration (MSHA) investigated several of these occurrences within recent years. The investigated explosions occurred at significant depths, ranging from 700 to 1200 ft. Data from the National Lightning Detection Network indicated a strong correlation between the times and locations of the explosions with those of specific lightning strikes. This paper proposes that corona discharge from a steel borehole casing is the most likely mechanism responsible for these ignitions. A recently investigated mine explosion and fire at a depth greater than 1000 ft was selected for this study. Computer simulations were performed, using data collected at the mine site. CDEGS software from Safe Engineering Services & Technologies, Ltd. and MaxwellSV from Ansoft Corporation were used for the simulations. [ABSTRACT FROM AUTHOR]

The study of lightning protection system design encompasses nearly 300 years. Yet, many of the original sources for common design practices used today remain obscure. This paper traces the significant developments in lightning protection from the late 1700s to the modern day. Emphasis is placed on significant events in the history that have had direct consequences in the establishment of design practices for lightning protection. It is also demonstrated that many of the design practices used today were subject to significant scrutiny and empirical qualification. Our intent is to familiarize the student of lightning protection design with the original literature, testing, and other noteworthy contributions to the design of effective lightning protection systems. [ABSTRACT FROM AUTHOR]