[AMRadio] Comment on lightning surges

[Bob Macklin]

In the 80's I worked on the UofAz/NASA telescopes in the Tucson Az area.

On Mt. Lemmon (10K') NE of Tucson NASA had 3 telescopes and a tracking 
station.

All the power wiring was underground.

We installed large knife switches on the entry to each building. EVEN THE 
GROUND WAS DISVONNECTED!

We had both gas tubes and Transorbs on the input side. On the building side 
of the switches we only had transorbs.

These buildings all had metal dome roofs.

We knew we would get hit in every electrical storm. We installed a 300' 
crankup antenna tower in the corner of the compound. When a storm was 
approaching the custodian would disconnect ALL the buildings. He would also 
un plug the electronics in the buildings. Then he would run the tower up.

One custodian I knew was hit three times before he quit.

Bob Macklin
K5MYJ
Seattle, Wa.
"Real Radios Glow In The Dark"
----- Original Message ----- 
From: "CL in NC" <mjcal77 at yahoo.com>
To: <amradio at mailman.qth.net>
Sent: Friday, July 29, 2011 10:58 AM
Subject: [AMRadio] Comment on lightning surges


> 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
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