Grounding Arrangement Research Articles

Анализ факторов, влияющих на защитный потенциал металлического подземного сооружения, с учетом влияния движения электроподвижного состава по участку

The analysis of the factors affecting the protective potential of a metal underground construction during the motion of the locomotive on the section is carried out. A graphical representation of the factors affecting the magnitude of the protective potential of the DF (drainage facility) of a MUC is given. The factors influencing the protective potential of the MUC when driving along the section of the West Siberian Railway are grouped. The first group of factors - the locomotive parameters - includes current, speed, mass, locomotive type, train formation and locomotive coordinate. By means of KORTES PC, the intervals of parameter changes are determined. The second is the track parameters, comprises the resistivity of the upper structure of a track (sleepers, ballast and roadbed) and the rail type. The third one is the resistance of the GA (grounding arrangement) of a MUC, the bedding depth of a MUC and the distance from the rails to the MUC. The fourth - the TS (traction substation) parameters include the coordinates of a TS and the DF of a TS, the distance from the rails to the GD of a TS, the resistance of the DF of a TS, the equivalent resistance of the GD of a TS. Also, the specific resistance of soil is attributed to the factors affecting the protective potential of a MUC. The results are summarized in a final chart of factors affecting the protective potential of a metal underground structure, taking into account the motion effect of an electric rolling stock on the section.

Lightning Performance of Multiple Horizontal, Vertical and Inclined Grounding Electrodes

Single horizontal and vertical grounding electrodes are often used for an earth connection of the lightning protection system. However, there are many practical situations when such electrodes have to be enhanced for better efficiency and replaced by multiple horizontal, vertical and/or inclined electrodes. This paper presents a systematic approach to evaluating and comparing the lightning performance of such grounding arrangements based on simple formulas. The contributions of this paper are: It is shown that impulse impedance <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Z</i> may be derived from known formulas for low-frequency grounding resistance <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> ; a new definition of effective length is introduced that allows for such a derivation; a collection of accurate formulas for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> of all considered grounding electrode arrangements is presented; and a new concept of “effective volume” is described that enables a simple procedure to increase electrodes’ effective length. The new formulas for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> , <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Z</i> , and effective length of the different electrode arrangements allow an analysis that might help search for a choice of cost-effective configuration and dimensions of the grounding systems in the early design stage.

Method of integro-differential equations for interpreting the results of vertical electrical sounding of the soil

The paper is devoted to the problem of determining the geoelectric structure of the soil within the procedure of testing the grounding arrangements of existing power plants and substations to the required depth in conditions of dense development. To solve the problem, it was proposed to use the Schlumbergers method , which has a greater sounding depth compared to the Wenner electrode array. The purpose of the work is to develop a mathematical model for interpreting the results of soil sounding by the Schlumberger method in the form of a four-layer geoelectric structure. Methodology. To construct a mathematical model, it is proposed to use the solution of a particular problem about the field of a point current source, which, like the observation point, is located in the first layer of a four-layer soil. Based on this expressions, a system of linear algebraic equations of the 7-th order with respect to the unknown coefficients ai and bi was compiled. On the basis of its analytical solution, an expression for the potential of the electric field was obtained for conducting VES (the point current source and the observation point are located only on the soil surface). Results. Comparison of the results of soil sounding by the Schlumberger installation and the interpretation of its results for the same points shows a sufficient degree of approximation: the maximum relative error does not exceed 9.7 % (for the second point), and the average relative error is 3.6 %. Originality. Based on the obtained expression, a test version of the program was implemented in Visual Basic for Applications to interpret the results of VES by the Schlumberger method. To check the obtained expressions, the interpretation of the VES results was carried out on the territory of a 150 kV substation of one of the mining and processing plants in the city of Kriviy Rih. Practical significance. The developed mathematical model will make it possible to increase the sounding depth, and, consequently, the accuracy of determining the standardized parameters of the grounding arrangements of power stations and substations.

Overview of grounding schemes for solid‐state transformers in distribution networks

Proposed to be the critical enabling component for future distribution networks, solid-state transformers (SSTs) have drawn much attention lately. They have a massive potential to help reduce size and weight, improve efficiency, integrate microgrids, renewables and energy storages in distribution systems, and can fulfil multiple grid functions such as bidirectional power flow control, fault isolation, system reconfiguration, and post-fault restoration. The introduction of these power electronics devices in distribution systems, however, also brings new challenges to the grid. Extra levels of electromagnetic interference, stray current, and personnel safety are among the most prominent practical issues that proper grounding arrangements can address. In this paper, considerations that should be factored into the grounding scheme design for SST ports with different voltage forms and levels are thoroughly reviewed and summarised. The characteristics of various grounding schemes used in AC and DC distribution systems are evaluated and compared in detail from different perspectives. Based on the comprehensive review, several combinations of grounding schemes are recommended for typical SSTs. In addition, the inclusion of new relay protection devices in the SST grounding scheme design, considering their characteristics and unique requirements, to enhance protection and reliability is also discussed.

공동주택 전기실 관점에서의 침수피해 사례연구 및 수방기준 적용에 관한 연구

In Korea, flood damage caused by heavy rains occurs frequently. In addition, the number of people living in apartments is increasing day by day, and due to this, the electrical room located on the basement floor of the common part of the apartment is flooded. In the event of flooding damage, secondary property damage and personal injury may occur to many residents living in apartments. The case of flood damage in the electric room was investigated and the problems were identified. In this paper, as a solution to this, the ground arrangement of the electric room was suggested, and additional preventive measures were also suggested. Therefore, to better adapt to climate change during the rainy season, it is necessary to establish electric room arrangement and waterproofing standard plans strategically. It is judged that there must be institutional support for the proposed solutions to be realized.

Statistic analysis of lightning transients on wind turbines

In view of the actual random behavior of lightning strikes, an efficient algorithm is proposed in this paper for statistical analysis of the lightning transients on wind turbines. The equivalent circuits are established for blades, moving contact site, tower and grounding arrangement. A set of formulas is provided for evaluating their respective circuit parameters. With the equivalent circuits connected in sequence, a complete circuit model of wind turbines (WTs) is constructed for calculating lightning transients. The lightning transient responses can be obtained at different locations on a wind turbine by using the circuit model to perform the transient calculation. For checking the validity of the circuit model, the experiment measurement is also made on a laboratory-scale WT. An approximate match appears between the measured and calculated results. On the basis of the circuit model, the transient calculation is performed sequentially for each discrete amplitude in a large interval of lightning current. The random distribution of lightning current is taken into account by a cumulative probability function of exponential type. The corresponding probability density function is derived to weight the peak values of the lightning transient responses. The statistical values of the lightning transient responses can be determined by totalizing the weighted peak values in the interval of lightning current. Then, a case study is carried out to contrast the statistical values with the non-statistical ones calculated from the standard lightning current amplitudes, and a significant difference is discovered between them.

A study of grounding arrangements composed by vertical electrodes for two-layered stratified soil models

This paper presents a study of a grounding arrangement proposed for transmission line (TL) towers, particularly for conditions of a stratified soil where the electric resistivity of the first layer is higher than the second medium. Techniques based on TL-theory are presented to estimate the harmonic grounding impedance of such configurations and are compared to the solution obtained with a rigorous electromagnetic (EM) method. The results show that the grounding resistance, important to low frequency frequency phenomena, and the impulse impedance, to fast transients, decrease significantly with the use of vertical electrodes. For a 230 kV TL, the critical towers can be improved by the proposed arrangement, which includes a significant economy of the conductor material applied to the grounding.

Utilization and recycling of municipal solid waste in a subarctic zone

Municipal solid waste (MSW) collection and disposal is one of the major problems of urban environment in most countries worldwide today. The problem of utilization of solid waste in the Northern Europe on the Kola Peninsula was raised in this article, where the ground arrangement in a subarctic zone is very special and the weather conditions are severe. The paper main goal is to verify long-term impact of the Mezhdurechie municipal landfill on the atmosphere in Kola Peninsula. The paper also aims to establish the holding actions for recycling and utilization of worn-out tires for mentioned municipal landfill. The ground concentrations of pollutants from the operational sources were presented. The proposed recycling development in this paper has a positive impact on the ecoindustry and ensures environmental safety and municipal economy.

Shunt Capacitor Banks Online Monitoring Using a Superimposed Reactance Method

A new indicating quantity, named superimposed reactance (SR), is presented in this paper to determine failed capacitor elements’ involved phase and number in shunt capacitor banks (SCBs). The proposed quantity is estimated using available measurements to the unbalance protection function of SCBs numerical protective relays. The proposed SR adopts calibrating factors for element failures online monitoring and can provide live report of the number of failed capacitor elements. The proposed method applications are: faster identifying SCBs faulty units, for fuseless and internally fused designs, and planning preventive/scheduled maintenance for all types of unit designs including externally fused units. With integration of these applications into protection intelligent electronic devices that provide captured and time-tagged event records via communication protocols for HMIs and SCADA systems, outage times would be reduced and smart grids reliability would be improved. The developed algorithm supports three different grounding arrangements, Wye-ungrounded, Wye-grounded via a low ratio current transformer, and Wye-grounded via a grounding capacitor at the SCB neutral point. Comprehensive simulation and fault-location sensing in PSCAD and MATLAB have verified the proposed algorithm performance. Advantages of the proposed method reports over conventional unbalance relaying alarms are also demonstrated using a commercial relay test results comparison.

Studying grounding arrangements of the LVDC system through simulation

Low-voltage DC (LVDC) systems may soon become an integral part of our electric grid. Faults on DC lines are usually pole-to-ground faults that depend on the grounding arrangement of the DC system. The grounding of the LVDC system is not adequately covered in the literature and there is no comprehensive standard for it. This paper studies the effect of various grounding arrangements of the LVDC system on pole-to-ground fault protection. An overall scheme of the LVDC system is modeled and a pole-to-ground fault is placed on the DC lines. Possible grounding arrangements are analyzed employing MATLAB/Simulink software and detailed discussion is given for each arrangement. Finally, simulation results are compared and a preferred grounding arrangement is selected with the objective of having selective and effective protection without device damage.

A conductor arrangement that overcomes the effective length issue in transmission line grounding

The reliability and availability of the electric power transmission system is severely influenced by lightning. In Brazil, roughly 65% of the overhead transmission lines outages are due to lightning, whereas the backflashover is the predominant phenomenon compared to shielding failure. Hence, obtaining a low value for the transmission line grounding impedance is an important issue when dealing with transmission lines backflashover performance. Usually, for high resistivity soils, increasing the grounding grid dimensions does not lead to low impedance due to the effective length issue. In this work, a special arrangement of ground electrodes is proposed in order to overcome the effective length problem in high resistivity soil. The transient voltage response of this low impedance ground arrangement is evaluated numerically using parametric modeling approach. Comparisons of numerical simulations results and measurements from a reduced model study are presented for validation purpose. Additionally, the quality of the results obtained using the reduced model elects it as a valuable tool for studies of electromagnetic transients involving interaction of lightning and grounding grids.

A Strategy of Suppressing the Underground Impact Scattered Current in Power Grid by Using Insulation Baffle

In order to solve the accidents happened in the ponds or other special places around the tower which were caused by the diffusion current after lightning stroke the transmission tower, the protection measures for the problem tower in the area of Guangdong Province which occurred dead fish in the pond in thunderstorm weather were studied in this paper. The COMSOL mutiphysics simulation software was used in order to calculate the electromagnetic environment of the diffusion situation by grounding device after lightning stroke the power transmission tower. Study concluded that the safe distance between the fish pond and grounding device of transmission tower is 14 meter. The effects of the length and depth or stayed a gap of the insulation baffle on the fish in the fish pond were discussed. The protection method of the insulation baffle has important practical significance to the protection of the grounding device for diffusion current, and can provide some engineering guidance and basis for the grounding arrangement and transformation of the high voltage transmission line tower.

Consideration of Lightning Current along a Tall Structure in the Presence of Horizontal Arrangement Grounding

The evaluation of the behaviour of lightning current along a tall structure is becoming an important issue when considering the lightning protection equipment required along a tall structure. This behaviour is affected by the element of the ground reflection factor which has a correlation between the impedance of the ground and the tower. The impedance of the ground is considered for a horizontal grounding arrangement while the impedance of the tower is assumed to be constant. Hence, the ground reflection factor can be given a variable value, whereas most of the existing literature assumes a constant value. When a constant value is entered into a calculation field, an inaccurate result is computed.In this paper, the lightning current along a tall structure under varying values of ground reflection factor and including the effect of the presence of a horizontal grounding arrangement has been considered and the results discussed accordingly. Modelling of the lightning return stroke current along a tall structure was undertaken by entering the calculated variable value of the ground reflection factor. The results indicated that a variable value of the ground reflection factor causes different peak values of the current and wave shape of the lightning current for different positions along a tall structure.

Alignment of graphene oxide nanostructures between microgap electrodes via dielectrophoresis for hydrogen gas sensing applications

Graphene oxide (GO) nanostructures have been aligned between conducting electrodes via dielectrophoresis (DEP) with different electrical configurations. The arrangement of ground with respect to peak-to-peak voltage (Vpp) plays a crucial role in manipulating the GO nanostructures. Grounds on both sides of the Vpp electrode give an excellent linking of GO nanostructures which is explained by scanning electron microscopy and current-voltage characteristics. A finite element method simulation explains the electric field and voltage variation profile during DEP process. The optimized aligned GO nanostructures are used as hydrogen gas sensor with a sensitivity of 6.0% for 800 ppm hydrogen gas.

Statistical Description of Counterpoise Effective Length Based On Regressive Formulas

This paper presents a novel statistical description of the counterpoise effective length due to lightning surges, where the (impulse) effective length had been obtained by means of regressive formulas applied to the transient simulation results. The effective length is described in terms of a statistical distribution function, from which median, mean, variance, and other parameters of interest could be readily obtained. The influence of lightning current amplitude, lightning front duration, and soil resistivity on the effective length has been accounted for, assuming statistical nature of these parameters. A method for determining the optimal counterpoise length, in terms of the statistical impulse effective length, is also presented. It is based on estimating the number of dangerous events associated with lightning strikes. Proposed statistical description and the associated method provide valuable information which could aid the design engineer in optimising physical lengths of counterpoises in different grounding arrangements and soil resistivity situations. Keywords—Counterpoise, Grounding conductor, Effective length, Lightning, Monte Carlo method, Statistical distribution.

An ATP-EMTP Monte Carlo procedure for backflashover rate evaluation: A comparison with the CIGRE method

The paper presents the application of an ATP-EMTP Monte Carlo procedure for backflashover rate (BFOR) evaluations to HV overhead lines (OHL), equipped with three different types of spatially extended and/or geometrically involved tower grounding systems. The ATP-EMTP circuit model of the OHL includes detailed line insulation and lightning representation; grounding systems are simulated by a new and simplified model which reproduces the effects of propagation along the ground conductors and soil ionization phenomena. The statistical variables include lightning stroke parameters (polarity, peak current, front and tail times), lightning location, as well as line insulation withstand and phase angle of the supply voltage. An external software engine generates all the required statistically-oriented ATP-EMTP input data, sequentially launches and manages ATP simulations and finally post-processes the results. A good performance in terms of convergence and computation times is evidenced. Results are compared to those yielded by both the simplified and ‘complete’ CIGRE methods for backflashover rate calculations, showing the applicability of the proposed procedure to line configurations characterized by complex tower grounding arrangements.

Divergências e chão comum: o direito à educação no IV Seminário de Educação Brasileira

Este artigo aborda debates ocorridos no IV Seminário de Educação Brasileira (IV SEB), promovido pelo Centro de Estudos Educação e Sociedade (Cedes), em fevereiro de 2013, na Unicamp. Seu objetivo é caracterizar alguns temas e posições que estiveram em jogo para, deles, inferir elementos gerais do debate contemporâneo sobre a educação brasileira que possam contribuir para a caracterização do chão comum no qual nos movemos. Dentre os temas tratados no Seminário, foram destacados: a definição de direito à educação de qualidade, as formas de sua verificação e de responsabilização dos agentes que devem assegurá-lo.

Numerical analysis of electric force influence on heat transfer in a channel flow (theory based on saturated porous medium approach)

The present paper reports the influence of electrode and ground arrangement on electrically-driven airflow and heat transfer enhancement in a saturated porous medium placed in a channel flow. In simulations, the inlet velocity and temperature of air entering a test section are controlled at 0.35m/s and 60°C, respectively. High electrical voltage is tested in the range of 0–30kV. The numerical results show+ that when electric field is applied, swirling flow caused by shear flow effect is observed. When electrode is placed near ground, swirling flow is small but it has a high strength. In addition, the strength of swirling flow is increased by increasing electrical voltage. With occurrence of swirling flow, the heat transfer is totally higher than the case of conventional hot-airflow. By comparing with a single ground, swirling flow created by multiple ground effect spreads wider over the surface of sample. This causes temperature of the sample to increase faster. It is found from flow visualization that behaviors of swirling flow obtained by smoke incense technique and simulation have a good agreement. Furthermore, enhancement of heat transfer in the sample depended on the arrangement of electrode and ground, as well as, the position of the sample.

Novel approach of estimating grounding pit optimum dimensions in high resistivity soils

Good grounding arrangement is very important for safe and reliable operation of a power system and to ensure safety of the power apparatus as well as the operating personnel. In most of the inland arid desert areas, the soil resistivity is significantly high and it is difficult to get low earth resistance with conventional methods. Therefore, an economical and efficient grounding system design of the earthing pit is necessary which can be achieved by using a low resistivity material (LRM). When such material is used, it is important to optimize the pit design. The grounding resistance for different configurations were calculated and based on the results, an optimized pit configuration is discussed. The intent of this paper is to present a simple general computational technique for finding the optimum economical size of grounding pit when filled with LRM. It was found that the use of too high volume of LRM does not reduce the earthing resistance in a corresponding manner. The suggested method can be readily used by engineers to obtain a good earthing pit configuration for efficient grounding of the power system components in high resistivity soils.

Grounding Pit Optimization Using Low Resistivity Materials for Applications in High Resistivity Soils

Grounding arrangement is very important to maintain safe and reliable operation of a power system and to ensure safety of the power apparatus and operating personnel. In Saudi Arabia, the weather is dry and the soil resistivity varies significantly from area to area because the geodetic terrain varies from sea shore to the arid desert and dry mountains. In most of the inland desert areas, the soil resistivity is significantly high and it is difficult to get low earth resistance with conventional methods. Therefore, an economical and efficient grounding system design of the earthing pit is necessary which can be achieved by using a low resistivity material (LRM). When such material is used, it is important to optimize the pit design. This paper presents different configurations of grounding pits commonly used with LRM applications. Different parameters that affect the grounding resistance are studied in detail and an optimized pit design is suggested that can effectively reduce the grounding resistance to an acceptable value. The suggested method can be readily used by engineers to obtain a good earthing pit configuration for efficient grounding of the power system components in high resistivity soils.