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A Guide to BS EN 62305:2006 Protection Against Lightning Part 5

Lý do sét hình thành và nguồn gốc của nó vẫn là một vần đề còn đang tranh luận: Các nhà khoa học đã nghiên cứu các nguồn gốc khác nhau như gió, độ ẩm, ma sát và áp thấp khí quyển cho đến ảnh hưởng của gió mặt trời và các hạt tích điện trong năng lượng mặt trời. | íùrse Tall structures As modern construction techniques improve the height of structures is increasing. Super structures approaching almost 1km in height are now being constructed. This standard devotes a small section to this topic but recognizes further more specific recommendations will be required in future editions. One of the major protection measures required is to ensure adequate protection is afforded to the upper sides of these super structures to minimise any protection damage from side flashes to the structure. Research shows that it is the upper 20 of the structure that is most vulnerable to side strikes and potential damage. Figure 4.23 Petronas Towers Malaysia Natural components When metallic roofs are being considered as a natural air termination arrangement then BS 6651 gives guidance on the minimum thickness and type of material under consideration. BS EN 62305-3 gives similar guidance as well as additional information if the roof has to be considered puncture proof from a lightning discharge. Table 4.5 refers. Class of LPS Material Thickness 1 t mm Thickness 2 t mm I to IV Lead - 2.0 Steel stainless galvanized 4 0.5 Copper 5 0.5 Aluminium 7 0.65 Zinc - 0.7 1 Thickness t prevents puncture hot spot or ignition. 2 Thickness t only for metal sheets if it is not important to prevent puncture hot spot or ignition problems. Table 4.5 Minimum thickness of metal sheets or metal pipes in air termination systems BS EN 62305-3 Table 3 Equipotential bonding is another important aspect and with these particular structures it is vital to utilize the vast fortuitous metalwork present both in the concrete encased steel as well as the metallic cladding adorning it. 51 www.furse.com Tall structures I BS EN 62305-3 BS EN 62305-3 Physical damage to structures and life hazard Down conductors Down conductors should within the bounds of practical constraints take the most direct route from the air termination system to the earth termination system. The lightning current