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When lightning strikes an apartment building, transient voltages are generated or induced in electrical and telecommunication wires in the building. The transient voltages may cause malfunctions or failures of electronic or telecommunication appliances. Therefore, it is necessary to know the spatial distribution of voltage, generated by typical lightning, in the building. Although there are several works studying lightning‐generated voltages in buildings, they do not consider the presence of concrete that accommodates steel structures. In this paper, lightning‐induced voltages between wires in a simplified apartment building struck by lightning are computed using the finite‐difference time‐domain (FDTD) method, taking into account the presence of reinforced concrete. On the basis of the computed results, the effect of the presence of concrete is discussed. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Voltage and current waveforms of transmission lines struck by lightning are calculated for use in back flashover analysis. Calculation by using equivalent circuits is the general practice, however, there are limited experimental results for reference to evaluate validity of developed equivalent circuits under various line conditions. Calculation results by numerical electromagnetic analysis can be used as references if they are proved reliable. In this paper, the voltage rises at a model of a 154 kV transmission line hit by lightning is calculated by Method of Moments (MoM) and FDTD for comparison. They solve Maxwell's equations by using different algorithms, so, if the calculated results by these methods reasonably agree under various line conditions, the results of these numerical analyses are regarded reliable. The calculated voltage and current waveforms by the two numerical methods agree well under a variety of footing resistance of transmission towers, thus the authors conclude that the calculated results by FDTD or MoM can be employed as references to evaluate validity of circuit models for back flashover analyses. Thus, the results calculated by circuit analysis are compared with those calculated by FDTD. The multistory tower model (Ishii model) better reproduces the voltage waveforms in a wide range of the footing resistance than simple circuit models of a tower, and can be easily tuned for further accuracy. [ABSTRACT FROM AUTHOR]

This paper proposes a circuit model of a lightning strike to a tall grounded object. The model can consider the direction-dependent attenuation characteristic of current propagating along with a tall grounded object as well as frequency-dependent characteristics of lightning channel and tower impedances, in contrast to the conventional lossless transmission line representations. Hence, the model removes the use of an unrealistic high grounding impedance for approximately expressing the significant current attenuation propagating upward along with the tall object. Measured lightning currents at a height of about 500 m of the 634-m-high Tokyo Skytree are accurately reproduced with the proposed model, which assumes a constant lightning channel impedance with a current source that generates a current waveform decaying with time, or a frequency (time) dependent lightning channel impedance with a step-like voltage source. The proposed model can also be used for lightning electromagnetic pulse calculations. [ABSTRACT FROM AUTHOR]

Lightning electromagnetic pulse (LEMP) waveforms associated with lightning strikes to the 634-m high Tokyo Skytree are calculated by the finite-difference time-domain (FDTD) method in the two-dimensional (2-D) cylindrical coordinate. The three-dimensional (3-D) tortuous lightning channel and the tall strike object are represented by an “equivalent vertical” phased-current-source array. The current propagation speed along the equivalent vertical lighting channel is determined in two steps: first, the channel is projected on a plane including the strike object and a field observation point, and then it is converted into the straight vertical channel right above the strike object. Thus, the height-dependent lightning-current propagation speed along the equivalent channel depends on the direction of the observation point. The proposed method greatly reduces computational resources required for calculating LEMPs without deteriorating accuracy since it allows the use of the 2-D FDTD method. LEMP waveforms measured at a horizontal distance of 27, 57, and 101 km (in different directions) from the strike object are accurately reproduced by the proposed method. The results clarified that the lower region of the tortuous lightning has a large influence on the wavefront of the LEMPs at a horizontal distance ranging from 20 to 100 km from the strike point. [ABSTRACT FROM AUTHOR]

Observation of lightning current by using Rogowski coils started in February 2012 at Tokyo Skytree, which is a 634-m-high freestanding broadcasting tower. Electromagnetic field waveforms have been also observed by calibrated capacitive antennas at several tens of kilometers from the tower. Simultaneously observed lightning current and electric field waveforms are reproduced by using an electromagnetic model of a return stroke over lossy ground with the help of NEC-4. Lightning channel models with inclination are reconstructed from observed images. Consequently, it turns out that the electromagnetic field waveforms are affected by the geometrical shape of a lightning channel, current refractions in the tower, ground conductivity, and current wave velocity in the lightning channel. NEC-4 is quite useful for such analysis of lightning strokes hitting high structures. [ABSTRACT FROM AUTHOR]

Direct observation of lightning current is a fundamental approach to evaluating lightning parameters, which are among the most basic factors for the lightning protection design of various grounded objects. However, for a tall grounded structure, upward lightning flashes initiated from the top of the structure have usually been observed, and the direct observation results of downward flashes have been limited. We developed and installed a pair of Rogowski coils at Tokyo Skytree, which is a 634-m-high freestanding broadcasting tower in Japan (35.71°N, 139.81°E), and have conducted direct observation of lightning flashes striking the tower. As of November 2018, 70 lightning flashes striking the tower, 26 downward and 44 upward, have been observed since the end of February 2012. In this paper, we focus on the downward negative flashes that occurred at the tower for seven years from 2012 to 2018 and report on the observed results of typical waveform parameters of lightning stroke currents in comparison with other observed results on downward negative flashes. [ABSTRACT FROM AUTHOR]

Nine electric power companies in Japan have been collecting lightning data with lightning location systems. Five years of the lightning data (2009-2013) are summarized and analyzed in this paper. The recent annual number of lightning flashes of which the current is more than 10 kA in Japan is around 1 million. The variations of lightning occurrence characteristics by areas, seasons, and so on, are clarified. Meteorological conditions that may affect lightning occurrence are also discussed. Furthermore, we show that there is a clear correlation between the number of lightning strikes and the outage rate of transmission lines. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

SUMMARY In recent years, frequent damage to wind turbines by winter lightning has been reported in the region along the Sea of Japan. It is a serious finding that lightning hits concentrate on wind turbines in this region. The authors investigated the increase rate of the frequency of lightning hits on wind turbines due to wind turbine construction by using LLS (lightning location system) data. As a result, an experimental formula to estimate the increase rate of the frequency of lightning hits on wind turbines as a function of parameters related to the construction conditions, namely the height of wind turbines, the height above sea level, and the latitude, is proposed. [ABSTRACT FROM AUTHOR]

Wind turbines on the coast of the Sea of Japan have been damaged by lightning in winter. This is due to the frequent occurrence of upward lightning from wind turbines in winter. Occurrence of upward lightning proves to be closely related to the temperature distribution at high altitudes. In this paper, the correlation between lightning hits of wind turbines and the height of the-10 °C layer is analyzed. When an upward lightning hits a wind turbine in winter, the height of the-10 °C layer is lower than 2000 m in most cases. Moreover, winter lightning is classified into two types, namely, the storm type and the inactive type, and it is found that the parameters of lightning currents observed by LLS differ depending on the type of lightning storm. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 184(2): 44-50, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22357 [ABSTRACT FROM AUTHOR]

Lightning electric-field waveforms related to power line faults in winter have been identified. Most of those waveforms appear to be associated with upward lightning discharges with absolute peak currents of over 100 kA. They are quite different from common return-stroke waveforms, and the lightning discharges which produce these characteristic waveforms are called GC (Ground to Cloud) flashes. These high-current lightning discharges are distributed around the coastline in different ways depending on their polarities. The spatial distributions of high-current lightning discharges around Japan are also investigated. It is revealed that the region of Honshu Island along the coastline of the Sea of Japan belongs to the area in which the density of high-current lightning flashes is the highest in Japan through the year. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(1): 8–15, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20874 [ABSTRACT FROM AUTHOR]

In this paper, lightning electric field waveforms related to notable power transmission-line faults in winter along the coastline of the Sea of Japan were examined. Most of the wave- forms of the observed electromagnetic field changes, which were more than five times as intense as an average negative return- stroke fields, are inferred to be associated with upward lightning discharges. Lightning discharges that produce such characteristic waveforms are termed ground-to-cloud flashes, and properties of the associated electric field waveforms are examined. These lightning discharges in winter distribute around the coastline of the Sea of Japan in different ways depending on their polarities. [ABSTRACT FROM AUTHOR]

The lightning occurrence characteristics around Tokyo Skytree are investigated with Japan Lightning Detection Network, and the results are evaluated with observation data by the Rogowski coils installed at a height of 497 m and by cameras set around Tokyo Skytree. After the construction of Tokyo Skytree, the apparent density of detected strokes near Tokyo Skytree increases, but without lightning strokes to Tokyo Skytree, the density of detected strokes around Tokyo Skytree seems to be roughly constant. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]