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Direct Strike Lightning Protection
The awesome phenomenon of lightning is unpredictable. It is a constant danger to humanity and, in a world of increasingly complex and sophisticated buildings and equipment, a single direct strike, measured in microseconds, can result in physical damage to buildings and catastrophic failure to sensitive electronic equipment. It can start fires, cause major break-downs to electrical, telephone and computer installations, and simultaneously cause substantial loss of revenue. Lightning is a common event. Some 44,000 storms occur every day, bombarding land and sea with about 9 million lightning strikes.
It causes more than 1000 deaths per year around the globe and results in $1.2 billion in property damage each year in the USA alone.
Since 1760, the most popular methods of lightning protection have involved sharp (Franklin) rods, horizontal and vertical conductors (Faraday Cage) or combinations of both. Experience with these methods have evolved into the “Cone of Protection” and the “Rolling Sphere” techniques for design of lightning protection systems. The Codes of Practice acknowledge their limitations. For example -“ Experience shows that a conductor cannot be relied upon to provide complete protection with any protective zone” (British Code BS6651). In a similar way the German Code states, “Experience has shown that no unambiguous protection zone can be assigned to a lightning conductor”.
 System 3000 |
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System 3000, Lightning Protection System
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| System 2000 |
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Conventional AS- Australian Standard Lightning Protection Systems
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| ISODC System |
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Applications
Implementation of the Isolated Downconductor system is based on two sections of the IEC 62305-3 standard (Protection Against Lightning – Part 3: Physical damage to structures and life hazard). For correct installation, the system must be designed and installed in accordance with these requirements:
Step 1)
Determine the required height of the air terminal to provide protection according to the protection angle method of IEC 62305 or the rolling-sphere method of IEC 62305, NFPA780, AS1768, etc. The required lightning protection level can be determined by IEC 62035-2 Risk Assessment, or simply using LPL I for maximum protection. Using this information the designer should determine the required minimum height of the air terminal tip above the top of mast/items to be protected. (Note: Isolated Downconductor mast requires a minimum clearance distance of 2 m).
Step 2)
Determine the length of downconductor required, and for the selected lightning protection level, ensure that it does not exceed the maximum length in the following table. These lengths are derived from the knowledge that the ISODC cable has a tested separation distance of 1,000 mm (see IEC 62305-3 Section 6.3 or NFPA780 Section 4.21).
Step 3)
Meet ERICO’s mounting and installation requirements and interconnect to a standard compliant grounding or lightning protection system.
More Information
If the maximum cable limitations above cannot be adhered to, then it is possible to use two parallel downconductors. The ISODUAL adapter allows a second Isolated Downconductor to be connected to the air terminal. The second ISODC Downconductor is mounted externally to the Isolated Mast and fixed with UV-stable, non-conductive cable ties. Due to a policy of continued product development, specifications are subject to change without notice.
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| System 1000 |
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NFC Standard Systems
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