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This article presents an experiment of rocket-triggered lightning to 10 kV power distribution lines and the characteristics of lightning current at Guangzhou Field Experiment Site for Lightning Research and Testing during 2018–2019. The return strokes (RSs) current of the triggered-lightning flashes in this study exhibits a shorter half-peak width and similar risetime and peak current compared with those of subsequent strokes current from natural lightning. The peak current of RSs shows strong power function correlations with charge transfer within 1 ms and action integral within 1 ms of RSs, with R2 of 0.80 and 0.92, respectively. Besides, the peak current of RSs is proportional to the average rate rise of RSs (dI/dt). We recommend the double HEIDLER function to simulate the RS current and provide accurate raw data for the study of lightning protection.

In this article, we analyzed the difference in the estimated currents from the Foshan Total Lightning Location System (FTLLS) under two triggered lightning situations, i.e., triggered lightning to ground and triggered lightning to the distribution line. FTLLS underestimated the peak currents of triggered lightning to the distribution line, which is reflected in the peak far electric field. The peak far electric field of triggered lightning to the distribution line is about 12% lower than that of triggered lightning to ground. However, this difference in estimated current is not reflected in the far electric field waveform parameters, at least for the three field parameters: zero to peak risetime, 10%–90% risetime, and half-peak width time. The presence of distribution line will increase the risetime of the lightning return stroke current, the arithmetic mean of the current risetime of triggered lightning to distribution line is 0.46 μs, and that of triggered lightning to ground is 0.27 μs. Clarification of this underestimation phenomenon is beneficial for the application of the lightning location system in power systems.

In this article, we analyzed the characteristic parameters of close vertical electric field waveforms from triggered lightning at 58 and 90 m obtained at Conghua, Guangzhou, in the summer of 2019. A total of 11 characteristic parameters were defined, including leader electric field peak [kV/m] (E $_L$ ), return stroke electric field change [kV/m] (E $_RS$ ), zero-to-peak rise time [μs] (T $_1$ ), 10-to-90% rise time [μs] (T $_2$ ), half-peak width [μs] (T $_3$ ), zero-crossing time [μs] (T $_4$ ), slow-front duration [μs] (T $_5$ ), opposite polarity overshoot duration [μs] (T $_6$ ), fast-transition 10-to-90% rise time [μs] (T $_7$ ), opposite polarity overshoot ratio [%] (E $_OS$ /E $_L$ ), and slow-front magnitude relative to peak [%] (E $_S$ /E $_L$ ). The arithmetic mean, geometric mean, and standard deviation of each parameter were counted. Data comparison results at 58 and 90 m show that T $_1$ –T $_7$ at 90 m were larger than those at 58 m. E $_L$ and E $_RS$ at 90 m were both positively correlated with the peak current [kA] (I $_P$ ). The influence of distance on this correlation was also analyzed. The half-peak width of the current waveform was inversely proportional to that of the electric field waveform.

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.

In this article, we present a theoretical evaluation of instrumental decay time on the lightning electric field waveforms excited by lightning M -components. Fast and slow M -component waveforms were adopted as the injected lightning current. Simulation results for the electric field waveforms at 100 m and 15 km are presented. The results show that the M -component electric field waveforms suffer noticeable distortion when the flat antennas are characterized by small analog integrator time constants. The waveform distortions were defined in this article. It is shown that, compared to the electric field waveforms of the fast M -component, the electric fields of the slow M -component suffered larger distortion. This article emphasizes the importance of the taking into account of the instrumental decay time in lightning M -component electric field waveforms.

The authors present a statistical analysis of characteristics of magnetic fields at different distances from triggered lightning experiments on Transmission Line at Guangdong Comprehensive Observation Experiment on Lightning Discharge during the summer of 2019. The histograms and parameters of statistical distributions for the following 22 waveform characteristics are presented, including current peak, 10%–90% risetime, half‐peak width and steepness, leader magnetic field peak, return‐stroke magnetic field peak, magnetic field peak, 10%–90% risetime, half‐peak width and steepness at 15 m, 130 m and 1.55 km. The arithmetic mean of 48 return stroke current peaks is 18.3 kA and the geometric mean is 17.0 kA. The arithmetic and geometric means of the current 10%–90% risetime are 0.6 and 0.6 μs, respectively. The leader magnetic field, return‐stroke magnetic field and magnetic field peak at 18 m, 130 m and 1.55 km are shown linear relationship with current peak values. With increasing the distance(r), the magnetic field peak value decrease, combining the magnetic field characteristics reported by previous studies, the analysis of all magnetic field peaks in different distances suggest linear relationship with r −0.90. The magnetic field 10%–90% risetime shows linear relationship with ln(r) and half‐peak width did not show significant correlation with distance.

Based on the magnetic field recorded with a magnetic sensor deployed at 130-m distance from the channel base, we remotely measured the return stroke current waveform in classical rocket-triggering lightning flashes, including 40 M-components and 48 return strokes (RSs) in eight triggered flashes observed during the summer of 2019. The current waveform retrieved from the close magnetic field is in excellent agreement with the coaxial shunt measurement. For return strokes, the amplitude error of the peak current is less than 1 kA. The error of the 30%–90% risetime is less than 0.1 μ s. The error of the half-peak width is less than 1 μ s. The error of charge transfer within 0.1 ms of the return strokes is less than 0.1 C. For M-components, the amplitude error of the peak current is about less than 0.3 kA. The error of the 30%–90% risetime is generally less than 4%. The error of the half-peak width is approximately less than 3%. The error of charge transfer within 0.1 ms of M-components is less than 0.02 C. The magnetic sensor is likely applicable to measure lightning current without direct current measurement at near range in rocket-triggered lightning or natural lightning flashes.

This paper presents the induced voltage measured at the terminal of a 10 kV distribution line when triggered lightning taking place at a distance of 40 m. It is shown that the induced voltage waveforms exhibit three components including a slow increase preceding the initial negative peak, following a rapid polarity reversal and the attenuated oscillations. The waveform parameters are defined in this paper. The observed negative peak value ranges from −47.1 kV to −7.5 kV. The positive peak value ranges from 5.3 kV to 20.9 kV, and the peak to peak value ranges from 12.8 kV to 63.2 kV. The test results show that the negative peak value of the induced voltage at the terminal of distribution generated by nearby negative triggered lightning generally exceeds the positive peak value, and in some cases the negative peak value even reaches twice the positive peak value. The negative 10%-90% rise time ranges from 2.3 μs to 88.5 μs, and the average oscillation period is about 18 μs. Both negative and positive peaks of induced voltages show good linear relationship with the peaks of lightning return stroke current.

In this paper, we present the characteristics of current, electric fields and modeling approaches of lightning M-component mode of charge transfer. We consider both the classical M-components (occurring after return strokes) and M-component-type ICC (Initial Continuous Current) pulses occurring during the initial (ICC) phase of upward flashes. M-component-type ICC pulses can be distinguished from mixed-mode pulses using different criteria: (i) the 10–90% current risetime at the channel-base with respect to an 8-µs risetime; (ii) the time lag between the onset of the current and electric fields with a respect to a threshold of 10 µs; (iii) an asymmetrical waveform coefficient (AsWc) with respect to a value of 0.8; (iv) the relative height of the junction or connection points on the grounded channel above the ground. The features of M-component electric field waveforms are summarized for close, intermediate, and far distance ranges. The observed millisecond-scale slow-part pulse shows a polarity reversal from an initial-negative waveform at close range, to a full positive-flattening late-time response at intermediate range and a bipolar wave-shape at the far distance range. One or some microsecond-scale fast pulses (junction pulse) are observed to precede the millisecond-scale slow part pulse at intermediate and far distance ranges. The microsecond-scale fast pulses are dominated by unipolar pulses along with several cases of bipolar pulses exhibiting initial polarities of both signs. The main advantage of the guided wave model and its variations is their simplicity and straightforward implementation. The guided wave model is also able to reproduce reasonably well the observed slow electric fields. The nonlinear models are more physics-based compared to the guided wave models. They are based on an important number of adjustable parameters, many of which cannot be directly inferred from experimental observations. The significance of M-components is reviewed according to practical aspects in transformer secondary, surge protective devices (SPD), grounding systems.

The radiated electric field produced by lightning plays a vital role in lightning location systems (LLSs). The presence of the elevated objects, i.e. transmission lines in the presented study, result in an increase of amplitude and multiple sub-peaks in the observed electric fields. On the basis of the electric fields obtained from multiple sensors of Foshan total LLS, electric fields from nine negative lightning strokes associated with transmission-line faults at a distance of 10-86 km in Foshan area were examined in detail, which were adopted to make comparison with the radiated electric fields from natural negative cloud-to-ground lightning detected nearby within 1 min. It can be found that the arithmetic means (AMs) of initial electric-field peak values of waveforms associated with transmission-line faults are about twice those of natural negative lightning and the second and third sub-peaks can be identified obviously. In addition, the correlation between electric-field waveform characteristics and propagation distance was validated. The AM zero-crossing time, fast-transition 10-90% rise time and the time interval between sub-peaks slightly increase with distance.

Wind turbines are very vulnerable to lightning strikes due to their height, sharp edges and remote locations often with high soil resistivity. In this paper we present numerical simulations of the impedance of a typical wind turbine grounding geometry. We analyze the influence of interconnecting grounding systems of different wind turbines. IEC TR61400-24 suggests interconnection of grounding electrodes of wind turbines through horizontal electrodes (in the form of insulated or bare conductors) to achieve low steady-state grounding resistance. The analysis takes into account the frequency dependence of the soil electrical parameters. We show that the low frequency grounding impedance can be reduced by a factor of two or more as a result of interconnecting grounding systems. However, the reduction is significantly lower at higher frequencies because of the interconnection wire’s inductance. We analyze the spatial distribution of the ground potential rise and step voltage in response to typical first and subsequent lightning return stroke current waveforms. It is shown that both, ground potential rise and step voltage can be significant along the wire, especially for high resistivity soil, and placing sensitive equipment near the interconnecting wire should be either avoided, or insulated wire should be used.

International audience; The authors present an analysis of different charge transfer modes during upward negative flashes. The analysis includes a total number of 94 pulses that occurred during two upward negative flashes recorded at the Säntis Tower. The pulses included 59 mixed-mode (MM) initial continuous current (ICC) pulses, 17 M-component-type ICC (M-ICC) pulses, 8 returnstroke pulses, and 10 classical M-component (MC) pulses. It is found that the initial stage of the flash is responsible for the largest share of the total charge transferred to the ground. Simulation results for the electric fields associated with the considered charge transfer modes are presented and discussed. Return stroke (RS) and MM pulses were simulated adopting the MTLE model, while MCs and M-ICC pulses were simulated using the guided wave model of Rakov et al. The simulated results are shown to be in good agreement with simultaneous records of electric fields measured at a distance of 15 km from the Säntis Tower. The inferred velocities for MCs and M-ICC pulses range from 2.0 × 10 7 to 9.0 × 10 7 m/s, and the corresponding junction point heights range from 1.0 to 2.0 km. The inferred pulse velocities for RSs and MM pulses range from 1.3 × 10 8 to 1.65 × 10 8 m/s. The inferred current attenuation constants of the MTLE model obtained in this study range from 0.3 to 0.8 km, lower than the value of 2 km previously suggested for RSs in downward flashes. The obtained results support the assumption that the mode of charge transfer to the ground giving rise to MM pulses is similar to that of RSs. The results are also in support of the generally assumed similarity between M-ICC pulses and classical MCs.

Acoustic observation of laboratory simulated lightning discharge can greatly avoid the observation difficulties under natural thunderstorm environment. An acoustic observation experiment based on the impulsive current generation system and a microphone array was carried out and illustrated in this study. A quantitative study on characteristics of response sound pressure initiated from simulated lightning current was performed. The first arrived acoustic N-waves measured at different distances initiated from different discharge amplitudes were compared and analysed. The acoustic amplitude, rise time and duration time defined for N-waves and peak frequencies were found to have an obvious correlation with the discharging amplitudes of simulated lightning currents and the observing distances. The linear change of acoustic amplitude is more obvious than that of the other parameters with the changed discharging amplitude or observing distance. A certain degree of shape change of the simulated lightning current except for the amplitude may not significantly affect the response acoustic characteristics when comparing the first acoustic N-waves from 8/20 μs lightning current and another kind of impulsive current which has a wider shape and two subsequent peaks. The subsequent current peaks in short time delays were proved to successively generate acoustic N-waves independently without overlapping, which meanwhile, indicated a consistent linear relationship of amplitude and time delay between electrical and acoustic pulses.

This paper statistically analyzed electric field waveform parameters of 56 negative triggered lightning return strokes at the distance of 58 m obtained at Guangzhou Field Experiment Site for Lightning Research and Testing (GFESLRT) during the summer of 2019. In addition, the correlation between the electric field peak and the current peak at the bottom of the lightning channel has also been analyzed. The statistical results in this paper extend the database of detailed close electric field waveform parameters of triggered lightning leader/return stroke.

Identifying a relation between current and channel luminosity is beneficial for producing an approximation to channel current via channel optical signal. In this paper, damped sinusoidal oscillation currents with more or less symmetrical waveshapes are injected into a tungsten copper hemispherical air gap and into a graphite rod air gap. Repeatability and reliability in channel luminosity measurement are compared between two air gap channels. Parametric correlation analyses, involving 12 sequences of lightning currents with a current peak from 13.0 kA to 34.4 kA, a current 10–90% risetime from 9.7 μs to 20.2 μs, and a current half-peak width from 21.6 μs to 46.4 μs, show the luminosity signatures also exhibit more or less symmetrical pulses, although they lag behind the corresponding current pulses. In initial primary pulses of these damped sinusoidal oscillations, the current peak is approximately direct proportional to the luminosity peak. Direct proportional relations are also observed between current 10–90% risetime and luminosity 10–90% risetime, between current half-peak width and luminosity half-peak width, as well as between current charge transfer and luminosity-time integration. These features are similar to those found in classical M-component current pulses associating with the M-component mode of charge transfer. Applicability of the results is further discussed to estimate the channel current from the channel luminosity.

Temporal variation of the luminosity of lightning channel can provide a proxy for the temporal variation of current flowing through it. In this study, seven groups of lightning currents with fast-front waveforms, spanning a 10–90% risetime range from 2.1 to 9.5 μs, a half-peak width range from 35.5 to 147.8 μs, and an amplitude range from 3 to 30 kA, are injected into a 15-mm air gap between a pair of graphite rod electrodes. An analysis is given of waveform associations and of waveform parameter correlations between current pulses and luminosity pulses emitted by the current-carrying channel. The luminosity signature is found to be generally divided into three stages: initial rising stage, initial fast decay stage, and later slow decay stage. During the later slow decay stage, the luminosity follows faithfully with the current (i.e., linearly correlated with current), whereas no such a feature is found in the previous two stages. The current peak is roughly, linearly correlated with the luminosity peak. A roughly linear relationship is found between the current risetime and the luminosity risetime, but no direct correlations are observed between their half-peak widths. In regard of optical signature, it is concluded that the laboratory-generated lightning currents, which are featured with relatively short front times and relatively slow decay after peak, are of similar nature as the return-stroke current in naturally-occurred lightning arc.

Far-field measurements of lightning-produced electromagnetic fields are of high importance for lightning location systems. Data from recorded lightning strokes can be, for example, used to assess the risk of lightning-induced damage in some geographical areas. Artificially triggered lightning, usually generated using rocket-wire technology, plays an important role in the study of lightning physics. Multiple-station observations of far (typically larger than 20 km) electric field waveforms produced by rocket- triggered lightning are quite rare. In 2014, electric field waveforms were measured for return strokes through the rocket-and-wire technique at Conghua. They were measured by electric field sensors at nine sites belonging to the lightning locating system in Foshan, Guangzhou, China. A total of 38 events were recorded and overall statistics of those waveforms are presented. The results were compared to previous experimental data related to natural and artificially triggered lightning to validate their similarity.

This work aimed to develop an integrated process for production of gasoline fraction bio-fuels from bio-oil under atmospheric conditions. This novel transformation process included the catalytic cracking of bio-oil to light olefins and the subsequent synthesis of liquid hydrocarbon bio-fuels from light olefins with two reactors in series. The yield of bio-fuel was up to 193.8 g/(kg bio-oil) along with a very low oxygen content, high RONs (research octane numbers), high LHVs (lower heating values) and low benzene content under the optimizing reaction conditions. Coke deposition seems to be the main cause of catalyst deactivation in view of the fact that the deactivated catalysts was almost recovered by on-line treating the used catalyst with oxygen. The integrated transformation potentially provides a useful way for the development of gasoline range hydrocarbon fuels using renewable lignocellulose biomass.

The growing demand of commercial jet fuels, in combination with the strict environmental legislations, has led to immense interest in developing aviation biofuels. This work demonstrated that the bio-oil derived from fast pyrolysis of straw stalk was able to be converted into the jet and diesel fuel range hydrocarbons by a designed transformation route. This transformation included three reaction steps: (i) the catalytic cracking of bio-oil into low-carbon aromatics and light olefins, (ii) the synthesis of C8-C15 aromatic hydrocarbons by the alkylation of low-carbon aromatics with light olefins, and (iii) the production of C8-C15 cyclic alkanes by the hydrogenation of C8-C15 aromatics. It was also demonstrated that the production of the desired C8-C15 aromatics with a high selectivity of 88.4% was achieved by the low temperature alkylation reactions of the bio-oil-derived aromatics using the ionic liquid of [bmim]Cl-2AlCl(3) (1-butyl-3-methylimidazolium chloroaluminate). The synthetic biofuels basically met the main technical specifications of jet fuels based on the combustion heat, viscosity, freeze point and other characteristics of fuels. (C) 2015 Elsevier Ltd. All rights reserved.

We present an analysis of lightning electromagnetic fields taking into account the soil stratification and frequency dependence of its electrical parameters. Two current waveforms corresponding to typical first and subsequent return strokes are considered for the analysis. Different cases for the soil (homogeneous, 2-layer, frequency-dependent/constant electrical parameters) are considered. The analysis is carried out considering different distance ranges: close (50 m), intermediate (5 km) and distant (100 km). The obtained results confirm that the vertical electric field and the azimuthal magnetic field at close range can be evaluated assuming the ground as a perfectly conducting plane. The impact of the soil stratification and frequency-dependent parameters on the vertical electric field and azimuthal magnetic field appear at intermediate and distant ranges. On the other hand, the horizontal electric field is found to be very sensitive to the ground stratification for all the considered distance ranges. However, at close range, the impact of the soil becomes less significant for observation points that are located at above-ground heights of 10 m or higher. It is shown that the three field components are affected more markedly by the soil stratification than by the frequency dependence of its electrical parameters, especially for intermediate and distant ranges (i.e., 5 km and 100 km). Furthermore, subsequent return stroke fields are more significantly affected by the soil stratification and frequency-dependence compared to first return stroke fields. The impact of the frequency-dependent soil parameters on the considered field components is more noticeable in a poorly conducting soil compared to a good conducting soil. We present also a comparison between simulation results with simultaneous measurements of current and distant vertical electric fields associated with rocket-triggered lightning flashes. It is shown that the computed vertical electric field waveforms for the case of a two-layer soil follow to a much better extent the corresponding experimental waveforms compared a non-stratified ground model. The frequency-dependence of the soil affects slightly the early-time response of the field. However, the late-time response of the field is essentially determined by the soil stratification.

We succeeded in extracting intense O - ion beam by applying dc voltage to a microporous crystal 12CaO.7Al 2 O 3 (C12A7) engineered to incorporate extremely large amounts of O - (1.3 X 10 2 0 cm - 3 ) and O 2 - (2.7 X 10 2 0 cm - 3 ) in crystallographic cages. The O - ion beam is monochromatic and the current density (∼2 μA/cm 2 ) is higher by three orders of magnitude than the maximum value recorded for yttrium-stabilized ZrO 2 (YSZ). A surface metal electrode, essential for the YSZ to dissociate a drifted O 2 - in the bulk into an O - and an electron on the surface, is not needed for the C12A7. The presence of extremely large concentrations of O - and O - 2 ions and fast oxygen-ion-conductive nature of C12A7 allow extraction of O - ions directly from the surface.

In this paper, we present an analysis of the propagation effect along a lossy ground on the characteristics of lightning-generated electric fields, using simultaneous observations of lightning currents and radiated fields measured at nine different distances associated with rocket-triggered lightning. The triggered-lightning site is located in Conghua (Guangdong, China). The electric field waveforms were measured using the sensors belonging to the Foshan three-dimensional lightning location system that are located at distances from the triggered-lightning site ranging from 69 to 126 km. The propagation path was over land and mainly over flat ground. The field sensors used had an overall bandwidth from 160 Hz to 1 MHz. It is shown that even though the early response of the field can be reproduced reasonably well by adjusting the ground electrical conductivity, the subsidiary peaks, and the late-time response of the fields cannot be satisfactorily reproduced assuming a homogeneous ground model. However, a two-layer soil model allows obtaining very good agreement between computed and measured waveforms for all the considered distances and events. Compared to the homogeneous ground case, the computed early-, intermediate-, and late-time response follows to a much better extent the experimental waveforms. We also provide a discussion on the influence of the computational model and parameters on the simulated results.