Lightning Peak Currents Research Articles

Preliminary Findings on Lightning Peak Currents in Cilacap City at Central Java, Indonesia

Preliminary Findings on Lightning Peak Currents in Cilacap City at Central Java, Indonesia

Comparative Study on Lightning Data between the Fengyun-4A Satellite and the National Lightning Monitoring Network in Guizhou, China

Clustered data from the Lightning Mapping Imager (LMI) onboard the Fengyun-4A satellite were compared with lightning strike data from the National Lightning Monitoring Network (NLMN) for the period of 22 June–21 September 2020 over Guizhou Province, China. Spatial and temporal distributions of lightning counts for LMI and NLMN were mostly consistent, although the NMLN detected approximately ten times more lightning per hour than LMI. Influenced by background solar radiation, LMI data exhibited strong diurnal variations in lightning radiance, with significantly higher values during daytime. In contrast, NLMN lightning peak currents showed no similar variations. While no clear relationship was observed between the spatial distributions of LMI lightning density and radiance, a negative correlation was found between NLMN lightning density and peak current. Additionally, the matching rate (MR) for LMI and NLMN data, dependent on spatiotemporal matching criteria, was analyzed. The MR increased sharply with the extension of the temporal interval up to 2 s, then stabilized for longer intervals. In contrast, the MR was strongly influenced by the spatial matching grid cell size. For instance, within a 2-s temporal interval, an MR of 81.1% was estimated for NLMN data within a 27.5-km radius, compared to an MR of 79.8% for LMIG data within a 42.5-km radius. Furthermore, the MR was consistently higher for NLMN compared to LMI. Finally, using Bayes' theorem, we conducted a preliminary assessment of LMI's conditional detection efficiency, employing NLMN lightning data as prior information. The LMI detection efficiency was found to be significantly higher during nighttime than daytime, with values of 50.06% and 100% for daytime and nighttime detections, respectively, within a 2-s temporal interval and a 37.5-km grid cell.

Research on Lightning Overvoltage Protection of Line-Adjacent Pipelines Based on Solid-State Decoupling

Existing transmission lines and pipelines are frequently crossed and erected in parallel, meaning that if lightning strikes a wire and causes insulator flashovers, the resulting lightning current will spread through the grounding of the tower where the flashover insulator is located. This dispersion of current can lead to overvoltage effects on nearby pipelines. This study performs simulation calculations to analyze the overvoltage experienced by pipelines due to the dispersion of grounding current from the tower. Furthermore, this paper proposes a method for protecting the pipeline from such an overvoltage. Firstly, the lightning transient calculation model of a transmission line tower is constructed using the electromagnetic transient software ATP-EMTP 5.5. The model calculates the effects of lightning peak currents and soil resistivity on the distribution characteristics of lightning current in the tower, specifically in the area where the flashover insulator is located. Subsequently, a calculation model of the tower grounding grid–natural gas pipeline is developed, taking into account the distribution characteristics of lightning current in the tower. This model analyzes the impact of lightning peak currents, soil resistivity, and pipeline spacing on pipeline overvoltage. Finally, the effectiveness of the solid-state decoupler in mitigating lightning overvoltage in the pipeline is verified. The results demonstrate a positive correlation between the lightning current entering the tower grounding grid through the flashover insulator and the lightning current distribution characteristics. The solid-state decoupling device proves to be effective in reducing the voltage of the pipeline insulation layer, and the simulation results provide the optimal laying length of the bare copper wire.

Simultaneous Space‐Based Observations of TGFs and Lightning Optical Emission: Characteristics of Lightning

AbstractA previous study of the relative timing between optical lightning emission detected by the Geostationary Lightning Mapper and a sample of 24 simultaneous Terrestrial Gamma‐ray Flashes (TGFs) triggering the Fermi Gamma‐ray Burst Monitor has shown that the gamma‐ray signal appears at the same time as or slightly before the lightning stroke optical signal. A similar result has been demonstrated using simultaneous optical and gamma‐ray data from the Atmosphere‐Space Interactions Monitor. In this work, we add 95 additional untriggered (offline) TGFs to further investigate the correlations between the gamma‐rays and the associated lightning optical emission. Analysis of radio sferics has shown that TGFs are associated with relatively high lightning peak currents. The current results show that TGFs are associated with short duration, relatively low intensity optical signals in low‐to‐moderate flash rate thunderstorm cells, consistent with lightning leaders that produce TGFs occurring some distance below the cloud top and/or expending a fraction of their energy in accelerating relativistic electrons rather than in producing bright optical emission.

Lightning Peak Current Sensor Based on Electret Technology

Lightning peak current is one of the most important parameter concerning the studies of the lightning phenomena. Nowadays, with a continuous dissemination of elevated structures, such as telecommunication towers, the study of the lightning peak current could be intensified with the installation of measurement devices in large scale. Thus, it is useful to develop a device that is robust, compact, low cost, and allows data collection. This paper describes a high-current sensor operating in a range up to 100- and 7.7-kA resolution. The system consists of a self-integrating Rogowski coil connected to the electret sensor by a coaxial cable. The electret sensor is installed in a sturdy and inexpensive casing at the tower base. Measurements indicate a linear and precise correlation between the voltage generated by the coil, installed on the top of the tower, and the impulse current from lightning.

Predicting lightning sourced electromagnetic fields

Sferics used in audio-frequency magnetotellurics (AMT) for shallow conductivity-depth soundings (up to 400 m in a 1000 Ωm half-space at 1.5 kHz) are detected by global lightning networks, which catalogue the time and location of up to four million lightning strikes per day. Passive AMT surveys do not use source information, but rather assume that global lightning activity provides sufficient signal if data are acquired for long enough. This assumption not only limits survey productivity, but can also result in poor signal-to-noise ratios (S/N), particularly at dead-band frequencies (1.5–5 kHz). To increase S/N and survey productivity, we used lightning network data as a proxy for direct measurement of sferic source information. We carried out a Global Positioning System (GPS) synchronised AMT survey, and for each lightning strike in the catalogue we modelled earth-ionosphere waveguide propagation to accurately predict arrival time for every predicted sferic in our time series data. We extracted a window of data around each predicted sferic and stored these time series into a structured database with associated lightning network data, such as lightning peak current, polarity and geographical coordinates. Two examples from our sferic database show that lightning network data are accurate enough to predict amplitude and polarisation of sferics at our survey site. For large lightning peak current, we observed a strong correlation between source proximity and increased S/N, particularly at dead-band frequencies, which often correlate to induction scales pertinent to mineral exploration. Our findings establish an interconnected relationship between lightning network data and lightning sourced fields, introducing known source AMT.

Statistical Distributions of Lightning Peak Currents: Why Do They Appear to Be Lognormal?

AbstractThe statistical distribution of peak currents in cloud‐to‐ground lightning strokes is analyzed and discussed both in the context of the existing experimental data and from a theoretical viewpoint. The distributions of peak currents directly measured at instrumented towers are compared to those of peak currents reported by the U.S. National Lightning Detection Network and peak currents measured in rocket‐triggered lightning experiments; all those appear to be lognormal. To explain the observed peak current distributions, a simple model based on the large‐scale electric field evolution prior to lightning flashes is developed. Based only on the most general assumptions concerning the probability of occurrence of lightning discharge, it is shown that the distribution of the pre‐first‐stroke large‐scale electric field is close to lognormal in a certain range. With the introduction of structure factors relating the leader or cloud electric potential to this field, semiempirical relationships between the potential and the peak current in negative first and subsequent strokes imply that the peak current and pre‐first‐stroke large‐scale electric field obey distributions of the same type. It is demonstrated that with a suitable choice of parameters, the model‐predicted distributions are close to those obtained from direct measurements, and statistical tests show that their agreement with the data is at least as good as that seen for lognormal approximations.

Multivariate analysis of dim elves from ISUAL observations

AbstractThe Imager of Sprites and Upper Atmospheric Lightning (ISUAL) on the FORMOSAT‐2 satellite, launched in 2004, records Transient Luminous Events (TLEs). ISUAL has an imager and a spectrophotometer that observe TLEs all over the globe. Among these phenomena, elves are particularly difficult to detect. ISUAL often records events that correspond to significant far ultraviolet (FUV) emissions in the spectrophotometer but have no discernible TLEs in the imager. These FUV events are called “dim” elves. Therefore, it is important to develop mathematical tools to analyze the data to obtain a better evaluation of the number of elves and their occurrence. Multivariate approaches are applied to characterize the unlabeled events. The first approach is the principal component analysis which distinguishes two different groups, one including elves and dim elves. The second approach is the PARallel FACtor analysis which provides a waveform model for each group. These methodologies confirm that FUV signal is the evidence of TLE presence. A crude classification method was then suggested taking into account these results. The proportion of elves, relatively to the considered ISUAL data set, is found to be about 40%. It is similar to previous results and confirms that relatively weak lightning peak current is sufficient to produce elves. This new strategy demonstrates the potential for discriminating between lightning and TLEs without prior knowledge within the selectivity of the FUV spectral band.

Climatological diurnal variation of negative CG lightning peak current over the continental United States

AbstractThis study provides an 11 year climatology of the diurnal variability of the cloud‐to‐ground (CG) lightning peak current. The local diurnal variation of peak current for negative polarity CG (−CG) flashes exhibits a highly consistent behavior, with increasing magnitudes between the late night to early morning hours and decreasing magnitudes during the afternoon. Over most regions, an inverse relationship exists between the −CG peak current and the corresponding −CG activity, although specific details can depend on region and time of day. Overall, the diurnal variation of the −CG peak current appears to reflect fundamental differences between morning and afternoon storms, but additional studies are required to clearly identify the primary cause(s).

Positive Lightning Peak Currents Reported by the U.S. National Lightning Detection Network

We infer peak currents from radiation electric field peaks of 48 positive return strokes acquired in Gainesville, FL, USA, from 2007 to 2008. In doing so, we use the transmission line model, National Lightning Detection Network (NLDN) -reported distances, and assumed return-stroke speed. From a similar analysis of negative subsequent strokes, it appears that the implied return-stroke speed in the NLDN field-to-current conversion equation is 1.8 × 108 m/s (the NLDN peak current estimation algorithm is calibrated for negative subsequent strokes). The NLDN uses the same field-to-current conversion procedure (and hence the same implied return-stroke speed) for positive return strokes. However, NLDN-reported peak currents for positive return strokes differ from peak currents predicted by the transmission line model with an assumed return-stroke speed of 1.8 × 108 m/s. The discrepancy between regression equations for negative and positive return strokes suggests that the NLDN procedure to compensate for field propagation effects and find the average range-normalized signal strength (RNSS) works differently for these two groups of strokes. We find that the difference can be explained by the bias toward NLDN sensor reports from larger distances for positive strokes combined with the higher relative sensor gain (the ratio of sensor's peak current estimate to the NLDN-reported peak current) at larger distances.

On the relationship between lightning peak current and Early VLF perturbations

Lightning strokes are known to cause direct heating and ionization of the D region, some of which are detected via scattering of VLF transmitter signals and are known as Early VLF events. The disturbed ionosphere typically recovers in many tens of seconds. New experimental evidence is presented demonstrating that the scattering pattern and onset amplitude of Early VLF events are strongly related to both the magnitude and polarity of causative lightning peak current. Observations of Early VLF events at nine Stanford VLF receiver sites across the continental United States are combined with lightning geolocation data from the National Lightning Detection Network (NLDN). During January and March 2011, NLDN recorded 7769 intense lightning discharges with high peak currents (>100 kA) generating 1250 detected Early VLF events. We show that the size of the scattered field due to the ionospheric disturbance increases with the peak current intensity of the causative lightning discharge. The most intense peak currents of >+200 and <−250 kA disturb VLF transmitter signals as far as ∼400 km away from the lightning stroke. Early VLF event detection probability also increases rapidly with peak current intensity. On the other hand, the observed VLF amplitude change is not significantly dependent on the peak current intensity. Stroke polarity is also important, with positive strokes being ∼5 times more likely to generate Early VLF disturbances than negative strokes of the same intensity. Intense positive cloud‐to‐ground lightning discharges, especially when occurring over the sea, are also more likely to produce Early VLF events with long recovery (many minutes).

The VLF fingerprint of elves: Step‐like and long‐recovery early VLF perturbations caused by powerful ±CG lightning EM pulses

AbstractSubionospheric VLF recordings are investigated in relation with intense cloud‐to‐ground (CG) lightning data. Lightning impacts the lower ionosphere via heating and ionization changes which produce VLF signal perturbations known as early VLF events. Typically, early events recover in about 100 s, but a small subclass does not recover for many minutes, known as long‐recovery early events (LORE). In this study, we identify LORE as a distinct category of early VLF events, whose signature may occur either on its own or alongside the short‐lived typical early VLF event. Since LORE onsets coincide with powerful lightning strokes of either polarity (±), we infer that they are due to long‐lasting ionization changes in the uppermost D region ionosphere caused by electromagnetic pulses emitted by strong ± CG lightning peak currents of typically > 250 kA, which are also known to generate elves. The LORE perturbations are detected when the discharge is located within ~250 km from the great circle path of a VLF transmitter‐receiver link. The probability of occurrence increases with stroke intensity and approaches unity for discharges with peak currents ≥ ~300 kA. LOREs are nighttime phenomena that occur preferentially, at least in the present regional data set, during winter when strong ± CG discharges are more frequent and intense. The evidence suggests LORE as a distinct signature representing the VLF fingerprint of elves, a fact which, although was predicted by theory, it escaped identification in the long‐going VLF research of lightning effects in the lower ionosphere.

Estimating the Expected Number of Failures to Buried Optical Fibre Cables Due to Direct Lightning Strokes by Means of a Monte Carlo Algorithm

This paper presents an algorithm, based on a Monte Carlo method, to assess the yearly expected number of failures to buried optical fibre cables (provided with metallic components) due to direct lightning strokes. The random parameters that have been considered in the algorithm are the lightning peak current, the distance between the cable and the point of impact of the stroke to soil and the cable failure current (i.e. the minimum value of the lightning peak current able to produce a failure on the optical fibre cable). From this point of view, this paper proposes a new and more general approach to the problem; because, in addition to the lightning peak current, it is also based on other random parameters that should be considered for a better modelling of the phenomenon. Finally, the occurrence of the cable failures is associated to a time Poisson stochastic process.

Lightning occurrence characteristics in Japan for 17 years: observation results with lightning location systems of electric power utilities from 1992 to 2008

AbstractWe summarize the lightning data for 17 years from 1992 to 2008 obtained with lightning location systems of nine electric power utilities in Japan and analyze them. The observed annual number of lightning flashes of which the current is more than 10 kA is 400 000–800 000 and the 50% value of the cumulative distribution of lightning peak currents is about 23 kA in recent times. The variation of lightning occurrence characteristics by areas, seasons, and so on, is clarified. Comparison of the obtained data with those obtained by another lightning location system is also made. The relationship between lightning occurrence and climate is discussed. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Lightning Performance on Overhead Distribution Lines : After Improvement Field Observation

Two feeders of 20 kV overhead distribution lines which are located in a high lightning density area are chosen to be observed as a field study due to their good lightning performance after improvement of lightning protection system. These two feeders used the new overhead ground wire and new line arrester equipped with lightning counter on the main lines. The significant reduced of lines outages are reported. Study was carried out to observe these improvements by comparing to the other two feeders line which are not improved and not equipped yet with the ground wire and line arrester. These two feeders located in the nearby area. Two cameras were installed to record the trajectory of the lightning strikes on the improved lines. Lightning peak currents are measured using magnetic tape measurement system installed on the grounding lead of lightning arrester. Lightning overvoltage calculations are carried out by using several scenarios based on observation results and historical lightning data derived from lightning detection network. Lightning overvoltages caused by indirect or direct strikes are analyzed to get the lightning performance of the lines. The best scenario was chosen and performance of the lines were improved significantly by installing overhead ground wire and improvement of lightning arrester installation.

Lightning peak current estimation using a system identification approach

A system identification-based lightning peak current estimation algorithm using upper-air radiosonde observations is developed. The preceding convective and precipitative process leading to thunder cloud formation followed by the cloud electrification and the leader processes together with return stroke and the discharge process, is identified by considering it as a deterministic dynamic system, whose undisturbed and unmeasurable output signal – the lightning peak current, is contaminated with a stochastic disturbance. The model parameters determined thus, are used to predict the likely temporal lightning return stroke peak current magnitudes. Two alternative parametric estimation models namely Autoregressive with Exogeneous Input (ARX) and Autoregressive with Moving-Average Exogeneous Input (ARMAX) are used to estimate model parameters of the pilot study area and predict the likely lightning return stroke peak current in each case. The relative performances of the models are compared to determine the best model for application in 12-hour and 24-hour ahead predictions. For a short-term (12 hour) prediction, ARMAX2921 giving a best fit of 78.8429% turns out to be the most suitable model. For a longer (24 hour) prediction, the ARX291, giving a best fit of 75.0181% emerges to be the suitable model. These preliminary results indicate that lightning peak current may be estimated to a good performance using upper-air radiosonde observations.

On the estimation of lightning peak currents from measured fields using lightning location systems

Although, due to the high variability of key parameters such as the return-stroke speed, it is impossible to determine the lightning current accurately from the remotely measured electric or magnetic field for a given event, we show in this paper that, for an assumed return-stroke model, the statistical estimation (e.g. in terms of mean values and standard deviations) is possible. We show additionally that for the transmission line (TL) model, the equation permitting to infer the mean value of the return-stroke current from the mean value of electric or magnetic field and the mean value of speed has the same functional form as the well-known TL current—far field relationship. This result gives to some extent a theoretical justification to the use of lightning location systems to infer parameters of lightning current statistical distributions from measured fields alone.

Evaluation of lightning location data employing measurements of direct strikes to a radio tower

A lightning location systems (LLS) provides large scale information for lightning strikes to ground. In addition to the event time and strike point position, the LLS gives estimates for the lightning peak current. For the end user of LLS data it is important to know the technical limits of the applied network in terms of detection efficiency, accuracy of the stroke location and peak current estimate. To establish a ground truth reference for comparison of natural lightning current parameters and the data of ALDIS (Austrian Lightning Detection & Information System), a telecommunication tower on Gaisberg near the city of Salzburg (Austria) was instrumented for direct lightning current measurement. Since the start of the tower experiment in 1998 we have recorded more than 200 lightning flashes to the tower. Based on the analysis of the current waveforms nearly all of them are so called upward initiated discharges. GPS time synchronization of both data sets allows a precise correlation of individual events measured at the tower and reported by the lightning location network.

Distribution of lightning peak stroke currents in Ontario using an LLP system

Lightning peak currents are typically estimated with the use of remote sensing techniques. The lightning location and protection (LLP) system is used specifically for this purpose. This system records the remote peak magnetic fields radiated by cloud-to-ground lightning flashes. The peak stroke current distribution is determined by using these fields, a lightning locating algorithm, and a suitable propagation model. A more efficient lightning location algorithm and an improved propagation model are both investigated and applied to data collected in Ontario, Canada. These results are used to examine double-corridor outages on transmission lines.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>