Is there any information regarding lightning protection systems for a mast mounted on the top of a building?
There are systems based on NFPA 780 that are “mast” systems, where air terminals (lightning rods) or conductors are mounted on poles or masts to provide a zone of protection covering a structure. Normally these masts are much taller than 20 ft., and the masts are not mounted on the structure but beside it. This is normal practice for a hazardous or explosive structure, where you can accept no arcing or sparking so the lightning protection is placed above, not on, the structure. Conventional systems may use mast mounted strike termination devices to provide zones of protection for center roof areas. This is normally added to standard perimeter protection designs, because a centered mast wouldn’t meet the requirements of the Standards for protection within 2 feet of building corners and edges. The 150 ft. radius sphere model may be used with centered masts to place mid-roof areas under zone of protection.
