Lightning Electromagnetic Pulse Research Articles

The Indirect Effect of Lightning Electromagnetic Pulses on Electrostatic, Electromagnetic Fields and Induced Voltages in Overhead Energy Transmission Lines

The impact of a lightning electromagnetic pulse (LEMP) on a power line or power station produces an effect similar to that of switching between a significant power source and a power line circuit. This switch closure causes a sudden change in routing conditions, creating a transient state. This situation has been studied in terms of electrostatic and electromagnetic induction, as well as overvoltage changes. Appropriate mathematical models were used to analyze these changes. While vertical electric field analysis has been carried out in a few studies, magnetic field and horizontal electric field vectors have not been studied. In this study, the Rusck formulation and the Heidler current formulation are combined at the current level, developed and analyzed. This is because the Rusck expression can sometimes give incorrect results at the current level. Also, in the analysis, electromagnetic field formulations based on accelerating charges are used instead of the dipole approximation to eliminate the need for interpolation in the graphical results. In contrast to other studies in the literature, this study proposes the use of moving and accelerating load techniques to better understand the effects of LEMPs on power transmission lines. Also, in this study, the double exponential problem of the current form in Rusck’s formulation is addressed in order to obtain a close approximation of the physical form of the LEMP. Additionally, the field–line (coupling) relationship is studied according to a unique closed formulation, leading to important determinations about the overvoltages generated on a line depending on the propagation speed of the LEMP sprout and the electrical changes in the area where the LEMP first occurs.

Improving the Detection Effect of Long-Baseline Lightning Location Networks Using PCA and Waveform Cross-Correlation Methods

Ultra-long-distance and high-precision lightning location technology is an important means to realize low-cost and wide-area lightning detection. This paper carried out research on the high-precision location technology of very-low-frequency (VLF) lightning electromagnetic pulse based on the Asia-Pacific Lightning Location Network (APLLN) deployed in 2018. Two key technologies are proposed in this paper: one is the calculation method of signal arrival time using very-low-frequency lightning electromagnetic pulse waveform, and the other is the compression transmission technology of lightning electromagnetic pulse waveform based on a signal principal component analysis. The results of a comparison and evaluation of the improved APLLN with the ADTD system show that the APLLN has a relative location efficiency of 69.1% and an average location error within the network of 4.5 km.

Performance Analysis of Artificial Intelligence Approaches for LEMP Classification

Lightning Electromagnetic Pulses, or LEMPs, propagate in the Earth–ionosphere waveguide and can be detected remotely by ground-based lightning electric field sensors. LEMPs produced by different types of lightning processes have different signatures. A single thunderstorm can produce thousands of LEMPs, which makes their classification virtually impossible to carry out manually. The lightning classification is important to distinguish the types of thunderstorms and to know their severity. Lightning type is also related to aerosol concentration and can reveal wildfires. Artificial Intelligence (AI) is a good approach to recognizing patterns and dealing with huge datasets. AI is the general denomination for different Machine Learning Algorithms (MLAs) including deep learning and others. The constant improvements in the AI field show us that most of the Lightning Location Systems (LLS) will soon incorporate those techniques to improve their performance in the lightning-type classification task. In this study, we assess the performance of different MLAs, including a SVM (Support Vector Machine), MLP (Multi-Layer Perceptron), FCN (Fully Convolutional Network), and Residual Neural Network (ResNet) in the task of LEMP classification. We also address different aspects of the dataset that can interfere with the classification problem, including data balance, noise level, and LEMP recorded length.

On the Use of Electromagnetic Models and the 3D-FDTD Method in the Evaluation of Radiations Due to Lightning Strikes to Tall Objects

The purpose of this paper is the investigation of the use of a lightning return stroke current electromagnetic model and the Finite Difference Time Domain (FDTD) method, in three dimensions, in order to study the Lightning Electromagnetic Pulse (LEMP) due to lightning strikes to tall objects (towers). The proposed approach and the developed code are validated by the comparison with the measured data taken obtained in the specialized literature. The evaluation of the LEMP propagation, in presence of different values of ground conductivity, is finally presented and discussed. It is found out that the use of electromagnetic models, which are close to the physical reality of the lightning phenomena, yields reasonably accurate results. The obtained simulation results, using a calculation code developed on Matlab, have turned out to be in very good agreement with measurement data. It has been found out also that the spatiotemporal current distribution along the tower and the lightning channel is influenced by the conductivity variation. Indeed, the LEMP propagation is significantly affected by both lightning current change and ground conductivity variation. It can be noted that the simulation results obtained can be exploited in order to study the coupling problems between LEMP due to lightning strikes to tall objects with different electrical, electronic and telecommunication systems.

LEMP and ground conductivity impact on the direct lightning performance of a medium-voltage line

• Assessment of the LEMP influence on direct lightning overvoltages of medium-voltage distribution lines of the type equipped with a shield wire and surge arresters. • Comparison between the results obtained by a 3D-FDTD method and the LIOV-EMTP code. • The LEMP contribution on the overvoltages across insulators increases with increasing values of the soil conductivity. • The appropriate modeling of the LEMP effects is important for the lightning performance assessment of the type of lines considered in this paper. In medium-voltage distribution lines equipped with a multi-grounded shield wire and with surge arresters installed along the line at relatively short intervals, lightning outages associated with indirect lightning are less frequent than those associated with direct ones. The protection for this type of distribution lines is therefore dependent on the response to direct strikes. This paper presents and analyses the response to direct lightning overvoltages of lines of such a type located over a lossy soil considering the influence of the lightning electromagnetic pulse (LEMP), which is typically disregarded in the calculation of overvoltages due to direct strikes. The calculation results, performed by means of a three-dimensional finite-difference time domain (3D-FDTD) method and of the LIOV-EMTP code, indicate that the voltage across the insulator is enhanced by LEMP effects. In addition, it is shown that the enhancement due to the LEMP increases with the increase of the soil conductivity value. The modeling of the LEMP effects is therefore important for the accurate assessment of the lightning performance of medium-voltage distribution lines of the type considered in this paper, even when direct strikes are considered.

Debye Representation of Frequency Dependent Ground for LEMP Analysis With RC-FDTD

Finite-difference time-domain (FDTD) method combined with the recursive convolution technique is applied to compute lightning electromagnetic pulses (LEMP) for dispersive ground adopting Longmire and Smith (LS) model in two-dimensional cylindrical coordinates. The novelty of our study is that, to the best of our knowledge, the LEMP simulation has been realized in the time-domain for the first time by directly using the parameters of the LS dispersive soil model by treating the ground as a multipole Debye medium without using approximate techniques such as vector fitting. As a numerical example, the LEMP is simulated above and under the dispersive ground with buried rock formation, which is also modeled as the dispersive Debye medium. The performed simulations are compared at distances of 500 m, 5 km, and 50 km away from the lightning channel for both first stroke and subsequent stroke. The results show that the case of dispersive ground and the rock leads to a difference of up to 61.77% with respect to using constant electrical parameters.

A study of lightning electromagnetic effect on the metal roof constructions

Metal roofs are often seen as substitute of traditional materials such as concrete these years. But there have been few researches on the lightning electromagnetic effect on these constructions. This work adopts the Finite Difference Time Domain (FDTD) method to carry out numerical simulation of Lightning Electro-Magnetic Pulses (LEMP) generated by lightning discharge current. A substation was taken as an example, the distribution of LEMP field with metal roof and non-metal roof were calculated separately by 3-Dimentional FDTD method. The results show that the metal roof has a reflection effect on the LEMP field, which makes the LEMP field significantly weakened compared to traditional concrete buildings. But for constructions of windows and doors, the intensity of LEMP field inside the construction is still destructive. This work also discussed effects of doors and windows on the electromagnetic distribution and came to conclusions that the amplitude of LEMP field decreases significantly with distance from the door (or window) increasing. The size of the windows or doors was positively related to the LEMP amplitude in the construction.

A novel method for ground-based VLF/LF single-site lightning location

A single-site lightning electromagnetic pulse (LEMP) localization approach based on deep learning was proposed and practiced. The approach was based on a large amount of ground-based lightning location and waveform data in the VLF/LF frequency band. A model for predicting the propagation distance of LEMP based on a deep learning method was proposed. The model used multiple types of LEMP waveform data as well as location data for parameter learning. The new model for detecting lightning activity has been validated against ADTD systems. The verification results for thunderstorms in the range of 1000 km show that the relative error of the model for the prediction of signal propagation distance was 2.75–13.08%. Affected by the azimuth calculation error, the relative error of single-site geolocation was 4.91–15.26%.

Study on protection measures of lightning electromagnetic pulse in automatic weather station

Due to automatic meteorological station, the distribution of the unique geographical location and environment, the equipment has a large number of sensors and electronic components, and a highly integrated, combined with the electronic components of low dielectric strength, compression ability and the ability to resist electromagnetic interference and weak ability to resist shock current and lightning electromagnetic pulse is easy to damage to electronic equipment. Therefore, this paper analyzes the existing problems and harms in lightning protection design of automatic weather station system in Shanxi Province, and puts forward improvement and protection measures.

Effects of Soil Uniformity on Radial Electric Field of Lightning Electromagnetic Pulse

Effects of Soil Uniformity on Radial Electric Field of Lightning Electromagnetic Pulse

Finite Difference Numerical Method: Applications in Lightning Electromagnetic Pulse and Heat Diffusion

The finite difference time domain (FDTD) is a technique of the finite difference numerical method and is a simple but powerful and versatile tool that has been widely applied in many scientific and engineering problems. A typical application of the technique is in dealing with electromagnetic (EM) wave interactions with physical structures. This technique has been used to solve governing equations of various systems through obtaining numerical approximations to the time-dependent differential equations for computer simulations. This paper demonstrates the accuracy and versatility of the application of FDTD method by applying it to examine the effect of lightning electromagnetic pulse (LEMP) on a transmission line using a cross-linked polyethylene (XLPE) insulated power cable, as well as to analyze heat diffusion in a microchip heat sink made from Aluminium Alloy 6061. The effect of LEMP on a transmission line showed that the higher the values of the line parameters, the larger the voltages that will be induced on the line and that bigger values of finite difference (FD) parameters give a more accurate model subject to a stability criterion. Accurate modelling of induced voltages ensures that appropriate mitigating techniques can be deployed to reduce or eliminate the damaging effect of these on electrical and/or electronic devices/systems. Similarly, proper modeling of a heat sink provides the ability to closely estimate heat diffusion at product design stage such that a design is confirmed as workable before manufacture; thereby saving cost. Keywords—Finite Difference Method, Finite Difference Time Domain, Engineering Applications, Lightning Electromagnetic Pulse, Heat Diffusion.

Mathematical Parameters Calculation of Double Exponential Function by a New Numerical Method

Background: Lightning electromagnetic pulse (LEMP) and high-altitude electromagnetic pulse (HEMP) are widely described by three physical parameters (rise time tr, full-width at halfmaximum pulse width tw, and maximum electric field strength E0). These pulse shapes are often given by a double exponential form concerning four mathematical parameters, namely α, β, k and Ep. Objective: The transformation from physical parameters into mathematical parameters is necessary in waveform simulation and is traditionally accomplished by linear fit functions regarding the two groups of parameters. However, traditional methods commonly rely on data analysis and calculation. In order to obtain the mathematical parameters more concisely and clearly. Methods: In this paper, a numerical method to calculate the mathematical parameters by solving nonlinear equations with three key constraints is proposed. Firstly, we establish the nonlinear system of equations regarding four variables, namely t1, t2, α and β. Then, three constraints are given to converge the solutions of the equations. Lastly, select the minimal value of the convergent solution of each equation. Results: Comparing the solutions obtained by our proposed method to the iterated ones, the overall relative error is less than 2×10-8. Conclusion: The results show that our proposed method not only simplifies the transformation from physical parameters to mathematical parameters, but also keeps the solutions high accurate.

Direct Lightning Performance of Distribution Lines With Shield Wire Considering LEMP Effect

In medium-voltage distribution lines, lightning outages associated with indirect strokes are less frequent when surge arresters are installed at close intervals. In this case, the lightning performance is mainly determined by the line response due to direct strikes, usually assessed disregarding the effect of the lightning electromagnetic pulse (LEMP). This paper examines the influence of such an electromagnetic effect on the voltages across the line insulators caused by direct lightnings. The presence of both surge arresters and a shield wire is considered. By means of adequate modeling and numerical calculations, we show that the flashover rate due to the direct strikes is increased by the LEMP. The obtained results indicate that in the statistical assessment of the direct lightning performance of lines equipped by surge arresters and shield wires, the LEMP effect is not negligible and its accurate evaluation is hence required.

Assessment of the Effects of the Electromagnetic Pulse on the Response of Overhead Distribution Lines to Direct Lightning Strikes

In the usual practice, the evaluation of overvoltages due to direct lightning strikes to overhead power lines is focused on the representation of the effects of the lightning current injection, whilst the effects of the coupling between the conductors and the lightning electromagnetic pulse (LEMP) is disregarded. Motivated by recent results obtained for the case of a medium voltage line configuration with a shield wire, this paper extends the analysis to assess the contribution of the LEMP on the lightning performance of an overhead distribution line with and without periodically grounded wires and surge arresters. Moreover, the paper deals with the LEMP effect on the occurrence probability of flashovers on different phases, which is an important information on the service continuity of networks with isolated or compensated neutral earthing. A validation of the results is obtained by comparing the overvoltages calculated by the electromagnetic transient program including the model of the line illuminated by the LEMP and those obtained by a three-dimensional finite difference time-domain approach.

Analysis of coupling characteristics of coaxial line parallel to lightning current channel

Base on the analysis of the coaxial coupling theory, the experimental model of the coaxial cable short-range coupling lightning electromagnetic pulse is established to study the problem of coaxial cable short-range coupling lightning electromagnetic pulse on the ship mast and high tower. The combination wave generator is used to simulate the 8/20 μs lightning current waveform, and the metal bar with the length of 1 m and diameter of 0.016 m is used to simulate the lightning channel as the radiation source. The length of the coaxial cable and the distance from the radiation source are changed for the test. The conclusion is as follows: when the coaxial cable is coupled with lightning wave in a short distance, the voltage waveform of cable terminal is still double exponential wave, with strong damping oscillation at 0.1 ∼0.4 μs. When the cable terminal is open circuit or connected with matching resistance, the rising time is shorter, about 1 μs; when the cable terminal shielding layer is grounded, the rising time is longer, about 10 μs. The peak voltage and energy coupled to the coaxial cable at short distance are positively correlated with the cable length, and inversely correlated with the distance from the radiation source. The energy that the cable is coupled to mainly comes from the low-frequency part, and there are multiple energy peaks below 100 Hz. Using fitting curve and experimental data, when the coaxial cable terminal is open circuit, the lightning current reaches 30 kA, the cable length is 30 m, and the distance from the lightning channel is 0.15 m, the peak value of the voltage coupled to the cable terminal is 66 V. It has certain guiding significance and value in the practical application of electromagnetic pulse protection.

Lightning electromagnetic transient characteristics of the space launch site

The direct lightning protection system of the space launch site can achieve effective protection against direct lightning. However, the lightning electromagnetic pulse cannot be ignored while the rocket waiting on the platform. The three-dimensional lightning transient electromagnetic model is established by method of moments, when the launch site is struck by direct lightning. In order to quantitatively evaluate lightning environment of the launch site, electromagnetic fields of launch area are calculated in this paper with a size of 40×40 m2 on the ground and at 40 m above ground. When the lightning current is 200 kA in the case of severe lightning, the simulation results of basic parameters show that magnetic field on the ground is much larger than 40 m above ground, and the maximum and minimum values of magnetic field on the ground are respectively 608 A/m (7.6Gs) and 95 A/m (1.2Gs). The electric field at 40 m above ground is much larger than the ground, and the maximum and minimum values of electric field at 40 m above ground are respectively 111 kV/m and 26 kV/m. Under six different factors, the three factors of number of shielded wires, distance between lightning towers and lightning current wave-front parameters have obvious effects on the electromagnetic field in the launch area. The highest and lowest reduction rates of electromagnetic fields are about 88% and 33% respectively. However, other factors reduce electromagnetic fields by no more than 13%. The critical magnetic field for permanent damage of electronic equipment is 2.4Gs, which is between the minimum and maximum magnetic fields of the launch area. It is recommended that electronic equipment is placed in area with smaller magnetic field, which is close to the center of the launch area. This paper provides a reference for the lightning protection indicators and suggestions for the space launch site.

A Single Chip LiNbO₃ Photonic 2D Electric Field Sensor Using Two Perpendicular Electrodes

A lithium niobate (LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) single chip two dimensional (2D) electric field sensor has been proposed, fabricated and experimentally demonstrated. Two perpendicular electrodes are designed and fabricated on an optical waveguide asymmetric dual parallel Mach-Zehnder interferometer (ADMZI). Experimental results demonstrate that the sensor can be used to detect the two field components of a transient pulsed electric field simultaneously. The minimum/maximum detectable electric fields for the sensor <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${z}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${y}$ </tex-math></inline-formula> axes are 5 kV/m, 140 kV/m and 10 kV/m, 106 kV/m respectively for measuring the nanosecond and lightning electromagnetic pulse (EMP) in the time domain. In addition, the frequency response deviation is ±2.5 dB for the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${y}$ </tex-math></inline-formula> axis from 10 kHz to 1 GHz and for the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${z}$ </tex-math></inline-formula> axis from 100 kHz to 1 GHz.

Comparison of ionospheric reflection heights for LEMPs produced by lightning return strokes of different polarity

Apparent ionospheric reflection heights estimated using electric field waveforms of negative and positive cloud-to-ground lightning return strokes (-CGs and +CGs) that occurred during the same thunderstorms have been compared. We analyzed electric field waveforms of 101 -CGs and 74 +CGs that were recorded in August 2016 in Florida. For daytime conditions, the mean ionospheric reflection height for lightning electromagnetic pulses (LEMPs) produced by + CGs is larger than that for LEMPs produced by -CGs for either first or subsequent strokes, although the difference is statistically significant only for subsequent strokes. For nighttime conditions, the trend is the same, but the sample sizes are too small to draw meaningful conclusions. For daytime conditions, the mean ionospheric reflection height for subsequent strokes in -CGs is smaller than that for first strokes, while for + CGs the mean reflection heights for first and subsequent strokes are essentially the same. This disparity is related to the fact that subsequent strokes in –CGs usually develop in the channel of the first stroke, while subsequent strokes in +CGs usually form new terminations on ground and, hence, are similar to first strokes. In our dataset, NLDN-reported peak currents for + CGs tend to be higher than for –CGs for both daytime and nighttime conditions and for either first or subsequent strokes.

Exposure of Underground Cable Intrusion Detection System to Transient Disturbances Caused by Nearby Lightning Strikes

Electronic systems with extensive underground cable installations are endangered by damage or interference during lightning as a result of current and voltage surges induced in the installations. The paper presents the study on the lightning threat to the electronic intrusion detection system based on underground cable sensors during a nearby lightning strike to the pole of the lighting system installed in parallel with the sensory cables. In the extensive intrusion detection system working in a network composed of several controller-sensor-terminator units, a problem arises whether the neighbouring units should or should not be connected galvanically in order the system is less vulnerable to the effects of a lightning electromagnetic pulse. The problem is complex since the threat level may depend on many factors, i.e. the point of the strike, the lightning current, soil parameters, and configurations of the affected systems. The problem has been studied using numerical simulations based on the electromagnetic field theory and method of moments. The results show that the isolated configuration, i.e. without the galvanic continuity between the units, may be better as far as relatively low soil resistivity and low steepness of the lightning current waveform are considered.

Lightning return stroke electromagnetic field and energy at close distance by using 3D FDTD simulation

In this paper, the lightning return stroke electromagnetic field at close distance is calculated by the way of transmission line (TL) model and full-wave three-dimensional electromagnetic field simulation software XFDTD, which is based on finite-difference time-domain (FDTD) method. The evolution of distributions of electric field and magnetic field are summarized in the study. Furthermore, the total electromagnetic field and major components are analyzed to clarify the electromagnetic hazard from lightning electromagnetic pulse (LEMP). Then the temporal and spatial distribution characteristic of Poynting vector of the electromagnetic environment is shown to expound the energy distribution of LEMP at close distance. The results based on the analyses of field strength and Poynting vector show that the distribution of electric field, magnetic field and Poynting vector at close distance is akin to multilayered cylinder, and LEMP in the region characterized by large amplitude, transient behavior and high electromagnetic energy is a potential threat to adjacent electronic equipments. Moreover, engineering basis concerning LEMP protection and electromagnetic compatibility (EMC) design in the region closed to the return stroke point can be provided by the synthetical analysis of LEMP.