Lightning strikes can also be classified as negative or positive depending on the charge transferred to the ground. Upward strikes also occur but are rare and start at the top of tall structures such as mountains, skyscrapers, towers and antennas. Almost all strikes that touch the soil are cloud-to-ground discharges. On average, 20% of all lightning strikes involve an exchange of electrical discharges between clouds and the ground. The impact of a 30,000-amp discharge did enormous damage,” he said. “A flaw in the installation left the area unprotected. When the video is played back in slow motion, it shows how lightning discharges behave and also how dangerous they can be if the protection system is not properly installed: although there are more than 30 lightning rods in the vicinity, the strike connected not to them but to a smokestack on top of one of the buildings. He used a camera that takes 40,000 frames per second. This is the spectacular image featured on the cover of the journal. The final image prior to the connection was obtained 25 thousandths of a second before the lightning hit one of the buildings,” Saba said. When it was a few dozen meters from ground level, lightning rods and tall objects on the tops of nearby buildings produced positive upward discharges, competing to connect to the downward strike. “The image was captured on a summer evening in São José dos Campos while a negatively charged lightning bolt was nearing the ground at 370 km per second. Saba’s research on this topic was supported by FAPESP. The image is so special that it appeared on the cover of the 28 December 2022 issue of Geophysical Research Letters (GRL) – one of the most important scientific journals in the field –, which featured an article with Saba as first author. With a high-speed camera and the luck of being in the right place at the right time, physicist Marcelo Saba, a researcher at Brazil’s National Space Research Institute (INPE), and PhD candidate Diego Rhamon obtained a unique image of lightning strikes showing details of the connections to nearby buildings. A little Googling should find a science or engineering forum with some LPS discussions.Image: The image captured with a high-speed camera shows several lightning rods trying to connect to the downward discharge. I suggest getting a detailed proposal from your LPS vendor and posting it to this and other web sites for comment before proceeding. Lighting protection is not well understood by most people, and that includes some who install lightning protection systems (LPS). Being the highest thing around does increase your odds of being hit. Very tall structures that are significantly higher than their surroundings, such as radio and TV towers, are struck frequently enough that they are sometimes equipped with strike counters to monitor the number of hits. However, it is more likely to strike high points than low points. Having had lightning strike about 100 feet from me twice, once hitting the ground instead of the multi-story structure I was in, and once hitting the ground instead of any of the forest of masts on hundreds of nearby sailboats, I can assure you that it does not always strike the highest point.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |