Lightning Electromagnetic Fields Research Articles

Effects of Lightning Electromagnetic Field due to Lightning Strikes on a Tall Structure

Effects of Lightning Electromagnetic Field due to Lightning Strikes on a Tall Structure

Effect of Eddy Current for Photovoltaic Module on Lightning-Induced Overvoltage Caused by Electromagnetic Coupling

Lightning electromagnetic field will induce a high voltage on the photovoltaic (PV) farm and also generate the eddy current. To study the effect of eddy current inside a PV module, the mechanism of the eddy current is elucidated. The density of eddy current is derived and it is solved by the method of moments. The eddy current produces a magnetic field to weaken the original field, which can reduce the lightning-induced voltage. The eddy current is mainly distributed on the outside surface of both aluminum-back surface field solar cells and aluminum foil. Moreover, the lightning transient of a PV array is computed. It is concluded that the PV backsheet cored with aluminum foil can greatly reduce the differential-mode-induced voltage of PV module. Several crucial factors, including foil material, foil thickness, and the distance to solar cells, are discussed. In order to minimize the induced voltages of PV modules, the PV module with aluminum foil on backsheet is proposed and the suitable range of the foil thickness is determined.

Time-Domain Analysis of the Impact of Advanced Building Construction Materials on the Propagation of Lightning Electromagnetic Field and Its Mitigation Using Nanoforging

The comprehension of the propagation characteristics of lightning electromagnetic field (LEMF) is essential to inspect the impact of nearby lightning strike and its coupling effect on different systems and equipment. Undeniably, the presence of building structures alters LEMF reaching any point of installation of critical equipment. In this regard, this article attempts a complete time-domain analysis of the influence of building structures on LEMF propagation at near and far striking distance. The influence of aperture location on structures with respect to the direction of LEMF propagation is quantified first ever. The LEMF penetration capability of novel constructional materials, namely carbon nanotube (CNT)-forged concrete and glass fiber-reinforced gypsum, is compared to that of concrete, and surface charge estimation methodology is adopted for the first time to quantify the plausible LEMF shielding performance. It is observed that the presence of apertures influences the LEMF distribution, but their location has inconsequential effect. Among the materials, CNT-forged concrete offers nearly 2 dB of electric field attenuation and 10 dB in energy penetration due to LEMF, quantifying the field mitigation effect due to nanoforging. Experimental study confirms better shielding performance of nanocompounded concrete. For magnetic field, the presence of apertures and the type of construction material do not deliver a sizable effect.

Lightning Electromagnetic Fields Computation: A Review of the Available Approaches

Lightning represents one of the most critical issues for electrical infrastructure. In dealing with overhead distribution line systems, indirect lightning strikes can lead to induced voltages overcoming the critical flashover value of the line, thus damaging the insulators. The computation of lightning-induced voltages requires the modeling of the lightning current, the evaluation of the lightning electromagnetic fields and the solution of the field-to-line coupling equations. The numerical calculation of the lightning electromagnetic fields is time-consuming and is strongly dependent on the lightning channel modeling and soil properties. This article presents a review of the most widely adopted methods to calculate the lightning electromagnetic fields, starting from the classical formulation, which requires numerical integration, and highlighting the most effective approaches that have been developed to reduce computational effort. This is done first for the case of a perfectly conducting ground, then the available formulations to account for the ground finite conductivity are presented together with their possible implementations in both the frequency and time domains.

An Efficient Method for the Computation of Electromagnetic Fields Associated With Tortuous Lightning Channels

Lightning electromagnetic (EM) fields are typically computed by assuming the current propagation within a straight vertical channel of negligible cross section. However, it is well known that the lightning path is tortuous and this can significantly affect the radiated fields and the lightning-induced voltages on power lines. Lupò <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">et al.</i> (2000) proposed an analytical method evaluating the EM fields radiated by a tortuous channel assuming a step current source; to consider an arbitrary (realistic) current source, a slow-converging convolution integral was applied. The aim of this article is to reduce the computation time of such procedure by extending to the tortuous channel case the approach proposed by Brignone <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">et al.</i> (2021) for the evaluation of the lightning EM fields with arbitrary current source, originally developed for a straight vertical channel. The performances of the present method are evaluated by means of comparison with the solution proposed by Lupò <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">et al.</i> (2000), showing an excellent agreement with a significant reduction of the CPU effort. This in principle will allow the computation of lightning-induced overvoltages at both individual and statistical level without a prohibitive computational effort.

On the Importance of Considering Realistic Orography Into the Evaluation of Lightning Electromagnetic Fields in Mixed Path

A lightning event striking the sea could induce several damages to the near infrastructures located on the coast. The possible damages are connected to the induced voltages caused by the electromagnetic fields generated by the lightning discharge. In order to compute them, several simplified approaches have been developed, using ideal models for the surrounding geometry and for the electrical parameters of the soil. This works provides the evaluation of the lightning electromagnetic fields generated by a lightning event striking on the sea taking into account the possible elevation of the terrain with respect to the sea level and the inclination of the seabed. The analysis has been carried out taking into account several distances between the coast and the striking location as well as different observation points, in order to evaluate the induced effects on a structure located close to the sea–land interface as well as in a more distant location. The analysis, implemented with the aid of the finite element method, leads to important conclusions on the components of the electric and magnetic field that are more affected by the realistic characteristics of the surrounding orography.

Influences of Soil Water Content and Porosity on Lightning Electromagnetic Fields and Lightning-Induced Voltages on Overhead Lines

This study is performed to analyze the effects of both soil water content and porosity, two of the influencing factors of the finite conductivity, on the propagation of lightning electromagnetic fields (LEMFs) and lightning-induced voltages (LIVs) on overhead lines. A two-dimensional finite difference time domain (FDTD) model together with an improved Archie’s soil model is adopted for the field calculation at close distances from the lightning channel. The obtained results confirm that the soil water content and porosity have notable impacts on the peak values of LEMFs, especially the horizontal electric field. Moreover, the soil water content and porosity are correlated when acting together. The peak values of the horizontal electric field are found to be markedly influenced by the porosity changes at high water content or the water content changes at low porosity. The LIVs on overhead lines in these two cases are also studied. There appear to be greater differences in the induced voltages as the water content changes at low porosity.

A Prony-based approach for accelerating the lightning electromagnetic fields computation above a perfectly conducting ground

Lightning strikes can seriously affect the reliability and availability of electrical infrastructures. The computation of lightning-electromagnetic fields represents one of the most crucial steps in the evaluation of the induced effects; thus, having at disposal accurate and efficient dedicated tools is essential. This paper proposes a new approach for the lightning-electromagnetic fields computation above a perfectly conducting ground. The proposed approach does not involve any assumption either on the channel-base current waveshape or on the attenuation function of the current along the channel. Integrals are expanded in series of exponential functions (Prony series) which makes them analytically solvable. The proposed approach results in a speed up of the computational time by a factor of 10 to some hundreds with respect to classical numerical approaches. The proposed method is validated against the classical formulas obtained through numerical integration for different channel-base current waveforms, attenuation functions and observation points.

Impact of Lightning Channel Base Current (CBC) Function Modeling on Computed Lightning Induced Overvoltage Waveshapes

Adverse effects of lightning strike are studied through the modeling of the lightning-induced over-voltage (LIOV) using the channel-base current (CBC) functions. A lightning current is characterized by the parameters like current peak value (Im), time-taken by the current to reach Im (tm), maximum rise-rate of the current (di/dt)max (steepness), and charge transferred at the contact point of the strike (Q). Using the CBC functions, the lightning electromagnetic fields (LEMFs) are calculated to compute the LIOV using a coupling model. Since the choice of CBC function plays an important role in LIOV computation, the present work studies its effect on the computed LIOV for matching and zero load impedance. As a case study, two functions: Heidlers and NCBC functions were examined. It was shown that a-sort-of delay characteristic from the NCBC function is reflected in the computed LIOV and also the tripolar nature of the LIOV for the case of imperfect ground. The difference between the LIOV computed using NCBC and Heidler?s function shows space-time reflections of the order of <formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex>$10^4$</tex></formula> magnitude.

A Prony-Based Approach for Accelerating the Lightning Electromagnetic Fields Computation: Effect of the Soil Finite Conductivity

This work provides an approach for speeding up the evaluation of lightning ElectroMagnetic (EM) fields in the case of a finite soil conductivity. The soil conductivity is taken into account through the well-known Cooray-Rubinstein (CR) approximation, which corrects the radial term of the electric field. A comparative analysis with some of the existing methods reveals an excellent accuracy with a substantial improvement in the CPU performance.

Characteristics of Lightning Electromagnetic Fields Produced by Antarctica Storms

This paper presents the temporal characteristics of electromagnetic fields produced by cloud-to-ground (CG) lightning flashes associated with Antarctica storms. A total of 51 positive CG (+CG) and 103 negative CG (−CG) flashes have been recorded by a magnetic direction finder (MDF) sensor in King Sejong Station, King George Island. In total, 47 positive and 107 negative return strokes were located, ranges from 32 to 569 km. All CG flashes were detected to occur over the ocean. The return strokes characteristics include the observations of slow front, fast rising, rise time, and pulse duration with geometric mean values of 3.2, 0.53, 3.21, 13.12, and 67.09 µs for +CG flashes, while 3.9, 0.57, 3.72, 20.75, and 69.86 µs for −CG flashes, respectively. Additionally, the average peak currents of +CG and −CG flashes were 4.13 kA and 3.14 kA, respectively. The temporal characteristics of the return strokes of Antarctica storms are comparable to other geographical regions. The smaller peak currents might be due to small magnitude of Antarctica cloud charges when compared to other geographical regions.

An Effective Method for Fast Evaluation of Lightning-Induced Voltages on the Overhead Transmission Lines Combining Electromagnetic Topology and Matrix Pencil Method

In this article, an effective method combining electromagnetic topology (EMT) and matrix pencil method (MPM) for the fast evaluation of the lightning-induced voltages on the overhead transmission line (TL) is proposed. First, the EMT of the TL network is established based on the structure characteristic of the TL network and the scattering hypermatrix is constructed according the information of the junctions and terminal loads. Then, the piecewise sampling is performed for the spectrum of lightning signal, and the calculation of the lightning electromagnetic fields (LEMFs) of all observation points along the TL at the sampling frequency point is accomplished. Next, the supervector of the excitation source is constructed to realize the generation of the Baum–Liu–Tesche matrix equation, and the results of the lightning-induced voltages of all junctions on the TL network at the sampling frequencies are obtained. Finally, the lightning-induced voltages at all frequencies are obtained by using MPM to fit the sampled results, and the time-domain results can be generated by inverse fast Fourier transform (IFFT). In the proposed method, the LEMFs above the lossy ground are solved by the C–R formula and those below the lossy ground are calculated by the Cooray formula. Moreover, the feasibility of using EMT to analyze the lightning-induced voltages of the junctions on the TL network and adopting MPM to fit the sampled values of the lightning-induced voltages is verified. The correctness and efficiency of the proposed method are validated and proved by several numerical examples.

Influence of meteorological parameters on the propagation of lightning electromagnetic fields

Lightning electromagnetic field computation is essential in determining the impact of lightning discharge on various systems, equipment, and structures. In this regard, it is essential to know the factors affecting field propagation, and among these, the climatic conditions are essential to consider. This paper discusses the effect of different meteorological parameters on the propagation of lightning electromagnetic fields.The effect of temperature, vapor pressure, and relative humidity fluctuation on the change in the medium parameter is assessed, and the electric and magnetic field alteration is calculated. From the analysis, inconsequential variation is noted in permittivity for a temperature change from C to C and relative humidity from 0% to full saturation of 100%. Upon computing the variation in the field, the peak value of electric field and its time of arrival shows insignificant change. In line with this, the magnetic field propagation also remains unaffected by the weather conditions.

Fast Evaluation of Lightning-Induced Voltages on the Transmission Lines Above a Lossy Ground

To achieve the fast evaluation of the lightning-induced voltages on the transmission lines (TLs) above a lossy ground, the matrix pencil method (MPM) is adopted in this article to perform the fast calculation of the lightning electromagnetic field (LEMF). The feasibility of using MPM to accelerate the calculation of the LEMF is discussed and verified. For the observation point above a lossy ground, the Cooray–Rubinstein formula is selected to complete the calculation of the lightning horizontal electric field. For the observation point below a lossy ground, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Cooray</i> method is adopted. Then, on the premise of considering the influence of ground impedance and admittance, the iterative expressions of the voltages and currents on the overhead TLs are derived. Moreover, for the TLs with periodic grounding properties, the iterative expression of the voltage at the node is analyzed according to Kirchhoff's law. Finally, the correctness and efficiency of the proposed method are verified by several numerical examples.

Azimuth and elevation factors correction for single station lightning electromagnetic field sensor

This study aims to find the location of lightning return strokes using a single station electromagnetic field sensor with the implementation of magnetic field Factor B correction to best match with a reliable lightning strike location reference from TNB Research (TNBR) that uses Vaisala lightning detector with ±500m tolerance. A parallel plate antenna was used to measure the electric fields while two orthogonal loop antennas were used to measure the magnetic fields from thunderstorms in Melaka. Based on the type of Cloud-to-Ground flash and its recorded magnetic field peak amplitude polarities, the general direction of the lightning source could be determined in four quadrants divided equally between the cardinal directions. Measurement of return stroke peak amplitudes from electromagnetic field waveforms, distance between lightning measurement station and lightning strike was determined. Factor B corrections varied between 53M to 69M where the separation distance between compared strikes averaged 3.22 km. From the varied Factor B, it was averaged to 60.1M that yield a separation distance between the same compared strikes between 0.75 to 15.02 km. From all the strikes compared, the average separation distance between compared strikes was 7.64 km. It was determined that the accuracy of our lightning measurement system lightning location were between 7.14 and 8.14 km. Keywords: Azimuth, elevation, electromagnetic, lightning, localization, return stroke

Effects of Long Upward Connecting Leader Channel on Electromagnetic Fields for Lightning Striking to Tall Towers

The effects of long upward connecting leader (UCL) channel on electromagnetic fields for lightning striking to tall towers are studied via lightning transmission-line return-stroke model. The current distributions along the lightning channel and the tower are derived, and the resultant lightning electromagnetic fields with various UCL lengths above tower are calculated at close and far distances. It can be found that the contribution of the various components of the electric and magnetic fields depends strongly on the distance to the observation point. Electric field has a shading effect showing that the field amplitude generated by lightning striking to tall towers is smaller than that to ground, and that this shading effect depends on the UCL length and the tower height. However, we cannot find such an effect for the magnetic field. The shading effect of the electric field increases with the increase of the junction height above tower, but disappears when the observation distance exceeds a critical distance. Modeled results are also compared with their measured counterparts associated with lightning striking to the 600 m tall Canton Tower. The proposed model can explain why the ratios of peaks of luminosity to magnetic field of the downward first stroke are considerably larger than those of the subsequent strokes as being due to the fact that the junction height above tower for first stroke is higher than that for subsequent stroke, whereas the downward return stroke speed of first stroke is smaller than that of subsequent stroke.

Comparison of 3-D and 2-D Cylindrical Symmetry FDTD Simulation Results of a Lightning Strike to Gaisberg With ALDIS Sensor Measurements

In this article, numerical computations applying the finite-difference time-domain (FDTD) method are performed. Lightning electromagnetic fields radiated by a lightning strike to the Gaisberg Tower in Salzburg, Austria, and propagating over irregular terrain are calculated. The field propagation is computed with a three-dimensional (3-D) FDTD and, for comparison, a 2-D cylindrical symmetry FDTD. With topographic height maps, seven different propagation paths for a selected lightning strike to the Gaisberg tower are simulated and the resulting magnetic field (H-field) is compared with the received signal strength at seven sensors of the ALDIS sensor network for that event. The return stroke is represented by a transmission line model and the current waveform recorded at the top of the Gaisberg tower was used. The results of the 3D-FDTD simulation correlate well with H-fields registered at sensor sites in mountainous environments. Hence, 3D-FDTD can represent complex local reflection phenomena correctly, which the 2D-FDTD cannot. The results of recent studies, which show that a lightning strike to a mountain gives rise to a field enhancement at the sensor site for a relatively flat propagation path, could be verified by comparing the FDTD results with a set of existing sensor measurements. For the, otherwise, very hilly terrain conditions in Austria, the field enhancement caused by the mountain is attenuated along the paths to the respective sensors.

The effect of the inclined lightning channel on electromagnetic fields and the induced voltages on overhead lines

In this study, the effect of lightning channel inclination on above-ground lightning electromagnetic (LEM) fields and their induced voltages on the overhead lines at different distances from stroke location (SL) in the presence of lossy soil ground is investigated. To this end, the finite element method is used to solve the full-wave Maxwell’s equations. The results show that channel inclinations affect LEM fields significantly at all distances from the SL. At an equal distance from SL, the observation point position relative to the lightning channel is important, and LEM fields of the points located on the horizontal axis of the lightning channel are affected more than other points. If the ground is more conductive, increasing channel inclination affects the radial component of the electric field at a close distance to the SL more; if the ground is more resistive, increasing channel inclination angle affects the radial component of the electric field at a far distance to SL more significantly. The vertical electric fields and azimuthal magnetic fields are slightly affected by ground conductivity but significantly affected by the position and channel inclination angle. Seven different states are considered for the channel position relative to the overhead line, and the lightning-induced voltage along the line is calculated at three points. The obtained results show that position and soil electrical parameters significantly affect the peak and wave shape of the induced voltage. If the lightning channel passes above the overhead line, the induced voltage peak will increase at points near the SL. If the horizontal axis of the lightning channel is parallel to the overhead line, the induced voltage peak will increase for the ground with lower conductivity by increasing the channel inclination angle. In this case, at distances farther from the SL, the effect of increasing the channel angle is negligible for high-conductivity grounds, but the induced voltage peak for less conductive grounds will increase. If the lightning channel's horizontal axis is perpendicular to the overhead line and the lightning channel does not pass above the overhead line, close to the SL, the induced voltage peak will decrease by increasing channel angle. At points far from the SL, increasing the channel angle in the low-conductivity ground will increase the voltage peak, and grounds with larger conductivity will decrease the voltage peak.

Study on electromagnetic environment analysis and lightning protection in buildings

When a direct strike occurs, the lightning surge current will intrude into the steel frame and steel bar of the building, forming a high lightning electromagnetic environment inside the building, which will affect the telecommunications equipment set in the building. Therefore, the problem of lightning protection in buildings becomes more and more important. In this paper, by studying the distribution law of lightning electromagnetic field in buildings, the intensity of magnetic field generated in buildings under different lightning strikes is analyzed. According to the three-dimensional diagram and equivalent diagram of the intensity of lightning magnetic field in each case, when the building encounters direct lightning, the lightning electromagnetic field is the strongest near the leadoff line, and the middle zone is weak. The lightning protection measures inside the building are put forward.

Time Domain Analysis of the Effect of Apertures on the Shielding Effectiveness of Buildings

High intensity electric and magnetic fields produced by lightning discharge can penetrate through any structure in its vicinity. Installation of a sensitive component inside any structure complying the Electromagnetic Compatibility standards need the information of exposure limit of the equipment in the installation environment. Any structure provides natural shielding to electromagnetic field and its limit depends on the material properties. In addition the structure dimension plays key role in defining the limit of shielding. This paper investigates the effect of aperture on the shielding effectiveness of building structure made of construction material against lightning electromagnetic fields. Building structures constructed in computer aided design (CAD) tool, are subjected to lighting electromagnetic field in FEKO Electromagnetic simulation software. Time domain approach is used to compute the shielding effectives of the building for different structural variations. It is seen that apertures decrease the shielding effectiveness of the building . As the structure size increases the percentage decrease in shielding effectiveness due to the presence of aperture increases. For magnetic field, construction material does not provide considerable shielding.