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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]

The features of lightning shielding of transmission lines have been calculated using the electrogeometric model (EGM) proposed by Armstrong and Whitehead. Discrepancies, however, have been found in the case of ultra-high voltage (UHV)-designed transmission lines. UHV-designed transmission lines often pass through high-altitude mountain areas, where foggy or rainy conditions are common when there is lightning. While the electrogeometric model determines the striking distance based on the lightning stroke current, environmental conditions, and how they might affect lightning discharge paths, they are not considered. It is possible, therefore, that foggy conditions may cause differences in the performance of transmission-line lightning shielding. This study used scale models of transmission lines for discharge tests with a 1-m air gap and analyzed differences in discharge paths and locations in dry and foggy conditions. The results showed that the polarity of the discharge had a significant influence, but differences in dry and foggy tests were negligible. [ABSTRACT FROM AUTHOR]

Investigates the incidence of ground lightning between the period of 1992-1995 in Japan. Establishment of the rational insulation design of power transmission systems; Information on lightning location systems in Japan; Description of the dispersion of lightning flash density in Japan; Examination of the relationship between the number of lightning strokes and thunderdays.

Laser-guided discharge is promising for protection of power transmission systems against lightning. Several experiments concerning the laser-induced electrical discharge have been performed up to now. However, it is necessary to understand the mechanism of the laser- induced electrical discharge to achieve the laser-triggered lightning. When a high-power laser beam is focused in air, a high degree of ionization is produced as brilliant beams near the focus. In this paper. the electrical discharge induced up to 2-meters with a high-power CO² laser focused by a 10-meter focal length mirror is described. Experiments of the laser-guided discharge were carried out by application of an impulse voltage to a rod- rod gap after laser radiation. This paper deals with the effects of delay times and polarity of the impulse voltage on 50 percent flashover voltage characteristics and the observation results of discharge phenomena taken by a still camera, a special camera named ALPS (Automatic Lightning Discharge Progressing Feature Observation System) and an image converter camera. [ABSTRACT FROM AUTHOR]