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In recent years, there have been several reports of blade damage caused by lightning strikes on wind turbines. A few of these accidents have resulted in more serious secondary damage owing to the continued rotation of the damaged blades. To prevent the initial damage from spreading in this manner, wind farms in the regions of Japan vulnerable to winter lightning were required to introduce lightning detection systems, which can accurately detect when lightning strikes the wind turbine and then immediately stop the rotation of the blades. Normally, when the system detects a lightning strike to a wind turbine and stops operation, the process of restarting is initiated only after the soundness of the blades is confirmed by visual inspection. However, in bad weather, it is often difficult to check the soundness of the blade visually, and the resulting delay in the restart process prolongs the downtime and reduces the availability of the wind turbine. In this paper, we report the results of using the supervisory control and data acquisition (SCADA) system data to check the soundness of the blades after a lightning strike to resume operations more quickly, thereby increasing up-time. [ABSTRACT FROM AUTHOR]

An unusual negative lightning flash was recorded at the Säntis Tower on June 15, 2012. The flash did not contain an initial continuous current typical of upward negative lightning, which is the most common type of event at the Säntis Tower. The flash contained four strokes, the last three of which were normal while the current associated with the first stroke resembled a Gaussian pulse with an unusually high peak value of 102.3 kA, a long risetime of 28.4 μs, and a pulsewidth of 53.8 μs, which was followed by an opposite polarity overshoot with a peak value of 8.5 kA. Our current records suggest the involvement of a long upward connecting positive leader in response to the approaching downward negative leader in the formation of this flash. Lightning location system (LLS) data indicate that a positive cloud-to-ground stroke occurred 1 ms prior to the first stroke of the flash. In this paper, we present a detailed description of the data associated with this event. Moreover, both a return stroke model and an M-component model are used to reproduce the far-field waveform of this bipolar stroke. The simulations result in a radiated electric field waveform that is similar to those of large bipolar events (LBEs) observed in winter thunderstorms in Japan. A sensitivity analysis of the used simulation models reveals that, by proper selection of the input parameters, all field waveform characteristics, except for the positive half-cycle width, can be made to fall in the range of LBE field characteristics reported in Japan. [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]

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]

Examines the results of lightning current measurement on transmission lines in Japan. Publication of the characteristics of lightning current amplitude in papers written on the issue; Methods used for conducting field investigations of lightning current in Japan; Results of lightning current measurement using magnetic links on transmission lines.