At any moment, there are as many as 1,800 thunderstorms in progress somewhere on earth and each is producing deadly lightning. Lightning detection systems in the U.S. see an average of 25 million strokes of lightning each year, from some 100,000 storms. It is estimated that the earth is struck somewhere by 100 lightning bolts every second.
There are five elements that need to be in place to provide an effective lightning protection system. Strike termination devices must be suitable to accept direct lightning attachment and patterned to accept strikes before they reach insulated building materials. Cable conductors route lightning current over and through the construction, without damage, between strike terminations at the top and the grounding electrode system at the bottom. The below grade grounding electrode system must efficiently move the lightning to its final destination away from the structure and its contents. Bonding or the interconnection of the lightning protection system to other internal grounded metallic systems must be accommodated to eliminate the opportunity for lightning to sideflash internally. Finally surge protection devices must be installed at every service entrance to stop the intrusion of lightning from utility lines, and further equalize potential between grounded systems during lightning events. When these elements are identified properly in the design stage, incorporated into a neat workmanlike installation, and no changes to the building occur, the system will protect against lightning damage. Elements of this passive grounding system always serve a similar function, but the total design is specific for each particular structure.
Lightning protection components are made from materials that are resistant to corrosion and they must be protected from accelerated deterioration. Many system components will be exposed to the atmosphere and climate. Combinations of materials that form electrolytic couples in the presence of moisture must not be used. Current carrying system components must be highly conductive. Prevailing site soil conditions will impact in-ground system components. The system life and maintenance/replacement cycle is dependent on material choice and the local environment. System materials must be coordinated with the structural materials in use – including flashings, copings, ventilator housings, various roofing systems – to maintain the moisture envelope for the intended life of the building.
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