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A single-station-based lighting mapping system comprising a microphone array, which detects electromagnetic (EM) and thunder signals, has recently been developed and deployed for lightning observations. Using one microphone array consisting of 19 electret microphones installed on a 3-D steel frame, this system receives and processes the EM and thunder signals to determine the location of lightning thunder sources. We implement a new broadband direction-of-arrival estimation technique, namely, the maximum power beamforming algorithm and derive the 3-D location results based on the time difference between the acoustic signal and the EM signal. In this paper, four cloud-to-ground flashes with different branch channels recorded by the system are analyzed and presented in which the located thunder sources of two lightning flashes are compared with the photograph of the high-speed camera. The details of the system implementation along with the successful reconstruction of the lightning channel in 2-D and 3-D space are discussed. The results indicate that the location system could effectively map the lightning thunder sources, and the result is highly consistent with the high-speed video camera images. Moreover, the acoustic mapping system is capable of locating the main channel produced by the return stroke process; it also depicts the branching channels. It is shown that the system is capable of distinguish different branches of the same lightning; it also obtains different lightning channels occurring almost simultaneously. [ABSTRACT FROM AUTHOR]

In order to solve the frequently occurring lightning flashover problems on ±500 kV dc transmission lines in China, the authors have conducted the research on the dc line arrester since 2011. In this paper, the structure and installation, technical parameters, and protection performances, as well as their deterministic processes of the arrester are presented and analyzed in detail. In 2013, the authors successfully developed the arrester products, and the type tests show that they have excellent performance parameters and can act effectively against the lightning impulse and cutoff the dc follow current. By now more than 500 dc line arresters have been installed and used on seven ±500 kV dc transmission lines in eight provinces of China. About four years of operating experience shows that the arresters work safely and reliably over a long period of time, and have been effectively reducing the lightning flashover rate of the ±500 kV dc lines. [ABSTRACT FROM PUBLISHER]

Abstract: Flashovers due to lightning, pollution and other factors frequently generate long ac arcs along the surfaces of insulator strings on overhead transmission lines; they cause great damage to insulators. Based on the motion characteristics of long ac arcs obtained from experiments, this paper presents the propagation models of the motion processes of long ac arcs, these simulations are important to design suitable parallel arc horns to protect insulator strings. The simulation models include the spatial model, the temporal model of a long ac arc, and the motion simulation models of an arc root and an arc column. The spatial model discretizes a long arc to current elements; the temporal model is proposed to consider the motion mode of a current element; and the motion simulation models of an arc root and an arc column describe the motion processes of an arc root and a column, respectively. At last, numerical simulations and corresponding experiments of long ac arcs along the surfaces of insulator strings of overhead transmission lines are compared. Both of them show a similar motion trend. [Copyright &y& Elsevier]

This article proposes the deconvolution method to evaluate the lightning channel-base current from the lightning magnetic field. We have verified the method using the magnetic field with/;without noises. The deconvolution results are both in good agreement with the simulated current. Also, we have discussed the deconvolution results when the condition number of the deconvolution matrix, $U_{{0}}$ , is different, and found that the deconvolution results will oscillate if the condition number of $U_{{0}}$ is very large. Note that the deconvolution method presented in this paper also works when using other engineering current models, such as transmission line (TL) model, and the modified TL model with exponential current decaying with height model, and so on. The deconvolution method is an efficient method to evaluate the lightning channel-base current from the electromagnetic field. This approach is also useful in research related to lightning characteristics and lightning protection. [ABSTRACT FROM PUBLISHER]

A systematic evaluation of the performance of the World Wide Lightning Location Network (WWLLN) over the Tibetan Plateau is conducted using data from the Cloud-to-Ground Lightning Location System (CGLLS) developed by the State Grid Corporation of China for 2013-15 and lightning data from the satellite-based Tropical Rainfall Measuring Mission (TRMM) Lightning Imaging Sensor (LIS) for 2014-15. The average spatial location separation magnitudes in the midsouthern Tibetan Plateau (MSTP) region between matched WWLLN and CGLLS strokes and over the whole Tibetan Plateau between matched WWLLN and LIS flashes were 9.97 and 10.93 km, respectively. The detection efficiency (DE) of the WWLLN rose markedly with increasing stroke peak current, and the mean stroke peak currents of positive and negative cloud-to-ground (CG) lightning detected by the WWLLN in the MSTP region were 62.43 and -56.74 kA, respectively. The duration, area, and radiance of the LIS flashes that were also detected by the WWLLN were 1.27, 2.65, and 4.38 times those not detected by the WWLLN. The DE of the WWLLN in the MSTP region was 9.37% for CG lightning and 2.58% for total lightning. Over the Tibetan Plateau, the DE of the WWLLN for total lightning was 2.03%. In the MSTP region, the CG flash data made up 71.98% of all WWLLN flash data. Based on the abovementioned results, the ratio of intracloud (IC) lightning to CG lightning in the MSTP region was estimated to be 4.05. [ABSTRACT FROM AUTHOR]

The overhead catenary system of high-speed railway, usually supported by viaducts, attracts more direct strikes than the conventional railway. However, there are ten thousands of slender steel rods in the reinforced concrete structure of viaducts. Therefore, it takes a lot of time to calculate the model of a long series of viaducts by the conventional electromagnetic field modeling method. An electromagnetic transient model for high-speed railway viaducts struck by lightning based on the decoupling method is proposed in this paper, in which the railway viaducts are divided into the box girder unit and viaduct pier unit. The viaducts model based on decoupling method (VMDM) is established by a series of box units supported by viaduct pier units at equal intervals. The equivalent circuit model of each unit was obtained by employing the vector fitting method based on the frequency-domain response. Experimental results of a newly built railway viaduct pier under lightning impulse current were presented to validate the equivalent circuit model of viaduct pier unit, which show high consistency with simulation results. In particular, the typical VMDM model of Beijing-Tianjin intercity railway viaducts was established with the proposed method. The result obtained from the VMDM model are compared with the simplified model. [ABSTRACT FROM PUBLISHER]