[AMRadio] Comment on lightning surges

[CL in NC]

At a facility I worked at years ago, all the control lines coming into the building came through lightning protection circuits, mostly consisting of Tranzorbs and discharge tubes  A lot of the control lines were several miles long.  If a storm was in the area, but not necessarily the immediate area, you could turn out the lights at the protection panels and watch the discharge tubes fire as lightning induced spikes from miles away were trying to get in.  Our home installed ground systems at best can handle all the induced stuff, but the major near strikes and direct strike will only be dissipated reliably with a ground system beyond most of out incomes.  Thompson lightning cable, Cadwelded connections, 500MCM cable around the building, and enough ground rods to get the earth resistance the lowest possible might be beyond the wallets of most folks. 

Even with all of that installed, in one storm where the building received a direct strike, I was in the perfect spot to  observe and arc occur on a cable ladder between the edges of the joints.  The ladder was connected to the next section with a plate on each edge, 8 bolts on each side, and also had a continuous #4 ground in the ladder bonded ever few feet.  With all that, it still arced between the edges of two sections of ladder next to the plates that bonded them together.  There was no damage to anything in the building, so I guess the $250K ground system did it's job.

Charlie, W4MEC in NC