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Lightning protection from tower NFPA 70 artcle 250.60 & 106 and NFPA 780

Question asked by c.valvo on Aug 21, 2019
Latest reply on Aug 29, 2019 by mbr

Lightning protection systems NFPA 780 and NFPA 70 article 250.60 and 250.106

 

I have a design with has multiple towers on these towers the manufacturer has lighting strike protection, the tower is aluminum they have supplied a 5 foot ground round a 6 foot piece of #6 insulated copper wire and connectors to attach to the structure and ground rod. They installation instruction are absent of any details or lightning protection scheme.

 

I have called them and found no assistance. 

 

My concerns are the engineering design has determined that per nfpa article 250 section 60 and 106 indicate that the strike devices shall be bonded to a common ground. We have no buildings but we have many inverter skid structures where our EGP are all connected and ground grid. The design is calling for each tower to have attachment to the structure of these skids, I don't like or believe this is proper, 

 

I do agree that the lightning protection system should be bonded and provide a common scheme to minimize potential difference, but my recommendation/belief would be that the lightning protection system have it's own reference to ground and that reference would be bonded at one location, moreover being it is going to a inverter skid with MV transformers and 1500v DC inverter surge arresters should be include at the bonding location to ensure protect of the equipment and further catastrophic failures. 

 

This of course is in absence of a certified Lightning protect design and evaluation, which is not in my scope, but I feel I should not accept the engineering design that using the bonding from each tower into our EGP as a replacement of a lightning protection reference to ground.

 

Please know this is on a location that is indicated as not being covered by NFPA 780, but is is a non excempt location so NFPA 70 is applicable

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