Evaluation of Transient Response of Different Earthing Configurations due to Lightning Impulses (original) (raw)
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Determination of Critical Electric Field and Recommended Earth Resistance Values of Earthing Systems
IREE, 2021
Impulse characteristics of earthing systems are important for designing earthing systems and lightning protection. In this work, experimental investigation on the impulse response of earthing systems of the single rod and tower is presented. The earthing systems of the single rod and tower are installed at three different sites, with different level of soil resistivity. Calculation using CIGRE's formulae is performed to determine the ionisation level of soil, which is also known as the critical electric field, Ec. Earth resistance values are also calculated using experimental results. It has been found that Ec is lower in high level of soil resistivity. Furthermore, the initial study indicates that it is important to consider the Ec and ionisation process occurring in soil when designing the earthing system.
This paper presents the transient behavior of an earthing system under the influence of lightning current injected in to it. Vertical rod and horizontal electrode buried in homogeneous soil are considered in this analysis. State-space representation based transmission line methodology is adopted with non-linear parameters for modelling the earthing electrodes in the time domain. Soil ionization phenomenon is taken up with the presence of residual resistivity. In this method, soil resistivity variation is adopted to evaluate the soil ionization phenomenon that occurs due to changes in the electric field. This study incorporates mutual coupling between the electrode segments for low and high soil resistivity. Earthing electrodes are subjected to a high-magnitude of lightning current impulse with different peaks. Transient voltage and impulse impedance are calculated to analyse the transient behaviour of earthing electrodes with soil ionization. Impulse impedance of vertical earthing r...
Modelling and Touch Voltage Simulation of Various Earth Grid Configuration Against Lightning
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Workers in an oil and gas refinery plant are exposed to the danger of touch voltage that occurs due to lightning strike. Horizontal grounding grid with minimum mesh size is the best precaution to eliminate this risk. However, this prevention method requires a lot of money. Henceforth, a series of calculations and simulations have been conveyed in order to obtain the most advantageous and proper grounding grid mesh size. Simulations were carried out by using CDEGS software. In this study, the mesh sizes were varied from 6.5m x 6.5m to 20m x 20m. The simulation results indicate that the peak value of maximum transient touch voltage rose for when the mesh size increases. Moreover, when the mesh size smaller, the injected current dispersed and flowed towards the earth faster, making the safety perimeter radius shorter. Nevertheless, grounding grid with smaller mesh size had more total conductor length. As a result, the cost would also increase. The results conclusively show that 10m x 1...
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The grounding system of a lightning protection scheme is designed basically to avoid arcing and dangerous step potentials. The grounding impedance of the system varies depending on soil structure and frequency. This paper describes the effect of harmonic impedance (also called frequency dependence of soil) on potential distribution under lightning strike to a metal tower with single grounding path, for different soil types. The results show that the peak value of ground potential rise (GPR) and step voltage (SP) may reach extremely hazardous values even at distances in the order of 90 m from the tower footing, especially when soil resistivity is high. Hence, we emphasise that, in contrast to power grounding, when designing of grounding systems that are meant to handle transient or high frequency currents as well, the frequency dependent soil parameters should be considered to avoid hazardous situations, especially at locations with a high probability of lightning strikes such as met...
Electrical earthing in troubled environment
International Journal of Electrical Power & Energy Systems, 2013
Practical challenges of electrical earthing in both steady and transient states have been revisited. By analyzing the cases based on theoretical and practical aspects, engineering guidelines are proposed to develop suitable solutions. Less complicated cases can be approached with various electrode configurations such as multiple ring, antenna, crow-foot and centipede arrangements. Distributed earthing arrangements treated with backfill materials are suitable for the sites with extremely high resistive soil. Clay based backfill materials such as bentonite-mix give corrosion and erosion protection for the electrodes in highly acidic, alkaline, saline and sulfur-rich environments apart from reducing the low frequency resistance. On-rock sites such as transmission and communication towers are better approached with concrete-based earthing systems in both cases of power and lightning protection earthing. Extreme cases of soil instability have been identified and discussed. The suitability of vertical and horizontal electrode components as well as copper and steel electrodes under various soil conditions is also discoursed. For most cases, we recommend all types of earthing systems to be integrated, however, properly coordinated system of Surge Protective Devices (SPDs) should be incorporated in such integrated earthing system.
Effects of Various Earth Grid Configurations on Ground Potential Rise Caused by Lightning Strike
International Journal on Robotics, Automation and Sciences, 2019
Ground Potential Rise (GPR) caused by lightning strike is a potential hazard for electrical equipment inside an oil and gas refinery plant. In order to mitigate the risk, horizontal grounding grid is applied. The best mitigation is to install a grounding grid with mesh size as small as possible. This condition requires a high cost. In order to obtain the optimal mesh size, a series of simulation of a grounding grid with mesh size variations on GPR caused by lightning strike has been carried out. CDEGS software was used to observe the GPR with various mesh size from 6.5 x 6.5 m to 20 x 20 m. Simulation results show that the maximum transient GPR rises as the grounding grid mesh size is increased, while the GPR distribution throughout the grounding grid area does not change much for different mesh sizes. In the other hand, decreasing the grid size would mean that more conductors are required, hence the cost would increase accordingly. The result shows that grid sizes from 6.5 x 6.5 m ...
Effects of Soil Profile on the Transient Performance of Substation Grounding System
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Lightning transient characteristic of the grounding grid is fundamental for optimum performance of lightning protection of a substation. In order to design an appropriate grounding system for such substation, it is important to study its transient characteristics because the high impulse current is significantly different compared to power frequency current. In this paper, substation grounding grid model was developed using CDEGS software to analyze the grid transient performance in terms of ground potential rise (GPR), touch voltage and step voltage when the grounding system is struck by a lightning impulse current. Several parameters, such as lightning current amplitude, feed point and the number of sub-grids, were altered to study their relationship with the transient performance. The maximum transient GPR, touch voltage, and step voltage increase as the lightning current amplitude increase. The maximum transient GPR and step voltage are the highest at the corner of the grounding...
Frequency and Time Response of Power Plant Grounding System Exposed to Lightning Strike
International Journal of Electrical and Computer Engineering (IJECE), 2016
This paper examines the frequency response of power plant grounding system exposed to the lightning current. Large amount of current generated by the stroke flow in the grounding system of power plant and dissipate in the soil. The electric and magnetic field generated by such high voltages and currents may cause damage of equipment and may be dangerous for the personnel in power plant. For the every given frequency obtained using Fast Fourier Transformation (FFT) of lightning current impulse, electromagnetic field theory approach is used to solve Maxell’s equation and compute scalar potential, electric and magnetic field. Also, the influence of the point in which lightning current is diffused in the grounding system is presented. Three dimensional plots of spatial distribution of scalar potential, electric and magnetic field are presented. The time domain response of scalar potential, electric and magnetic field on one profile is also presented.
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A Newly On-Time Following Up Electrical Earthing System Technology
2019 21st International Middle East Power Systems Conference (MEPCON), 2019
The electrical earthing/grounding for power systems is very important to restrict the residual current from any unwanted fault and reduce undesirable outage and prevent shock hazard. Many factors can affect the earthing system; corrosive soils with high moisture content and high salt content…etc. The proper design for earthing system depends on many parameters and must be carefully measured in the installed earthing site “i.e. moisture, temperature, salt contents…etc.”. In most cases, after determining the earth resistance system referenced to the standard values, there is no followed up by preventive maintenance during the life time of earthing system which leads to serious defaults in safety system. This paper introduces an actual model system which is a newly on-time automatic measuring and correcting earthing site system. The proposed technique uses an Aurduino program integrated with suitable electromechanical and electronic equipment as inputs and outputs corrected parameters....