tailieunhanh - Lightning Protection

Lightning protection systems have changed drastically since Benjamin Franklin first invented lighting rods in 1752. Today's systems must protect modern appliances, electrical systems and building constructions - they have to keep up with tile changing requirements of modern technology. Underwriters Laboratories Inc. (UL) keeps up with these changes. | Generated by Foxit PDF Creator Foxit Software http For evaluation only. Lightning Protection Why You Need Lightning Protection Lightning protection systems have changed drastically since Benjamin Franklin first invented lighting rods in 1752. Today s systems must protect modern appliances electrical systems and building constructions - they have to keep up with tile changing requirements of modern technology. Underwriters Laboratories Inc. UL keeps up with these changes. Our experience in the safety testing field has earned UL worldwide recognition and respect. jurisdictional authorities government agencies insurance representatives and consumers alike have looked for the UL Mark on products and systems for almostlOO years. When you see the Mark it means that the product or system on which it appears compares with UL s internationally recognized Standards for Safety. In the lighting protection field UL has been serving home and building owners since 1908. Today UL has a large number of trained lighting protection field representatives located throughout tile United States. UL inspects sites ranging from cow barns to missile silos front golf Course shelters to high-rise building systems. In fact some of the most famous buildings in the world are protected by UL Master Labeled lightning protection systems including the White House the Sears Tower and the Washington Monument. The Need for Lightning Protection Lightning can strike anywhere on earth - event the North and South Poles In any . geographical location lightning storms occur as few as five times or as many as 100 times per year see Fig. 1 . -The Northeast United States has the most violent thunderstorms in the country because of the area s extremely high earth resistivity see Fig. 2 . High earth resistivity the earth s resistance to conduct current increases the potential of a lightning strike. If struck structures in these areas will generally sustain more damage when there is no .