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I have a 6m tall steel tower (see photo). I'm in a 3rd world country so no code to bother with but safety is still a good thing.

My staff are not well educated and are very scared of lightning and as such insist we need a lightning rod on it. I thought that the structure would be sufficient to conduct a strike, and also maybe it is a faraday cage too? I'm not fussed about the expense but don't want to attract lightning either.

we have a 300mm x 20mm pointed copper rod on the top, and a 1.5m 20mm rod in the ground, connected with 25mm2 copper wire.

Also the PE for the 6000W search light on the tower is boulted to the tower, and the foot of the tower is tied into the copper rod at the base.

Is this good bad or Ugly? enter image description here

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    \$\begingroup\$ People shoud be pretty safe from direct lightning hits under that roof and in the vincinity of the tower. It's the secondary effects from the high currents and in the worst case molten metal that can be an issue. \$\endgroup\$
    – kruemi
    Commented Aug 12 at 10:22
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    \$\begingroup\$ Why would that be a Faraday cage? Concrete conducts poorly but it does conduct. \$\endgroup\$
    – Lundin
    Commented Aug 12 at 11:28

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In the US forest service has a document that describes the lightning safety standards for look-out towers used for spotting forest fires. These towers are frequently occupied during lightning storms, so I would believe I was fairly safe in a tower that followed these guidelines.

Of special note:

These standards call for down and main conductors to be stranded copper conductors 1/2 inch in diameter or larger.

and

Down conductors should be secured to the structure and not permitted to move or flex

In your drawing, the down conductor is (contrary to my understanding of the specification) not attached along the frame of the tower.

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    \$\begingroup\$ Thanks for that, I can do both of those things. \$\endgroup\$
    – SV Savannah
    Commented Aug 12 at 6:53
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    \$\begingroup\$ Fasten it well. Remember that when you send a large current pulse through a wire, you have essentially created a linear motor, and the wire will move. Tie it down with steel straps or similar! \$\endgroup\$
    – vidarlo
    Commented Aug 12 at 19:34
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You might want to refer to a US standard such as NFPA-780. I've linked a copy, but not sure how legitimate it is.

Your wire size is substandard.

I would not want to be in that tower in an electrical storm, lightning rod or not. Image from Forbes. Aside from the noise, currents are relatively high (tens of kA) and there might be enough voltage drop across the steel to injure a human if the copper wire does not do its thing properly.

enter image description here

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    \$\begingroup\$ bigger wire: easy done, and no doubt first rain drop the tower will be unmanned, of that i'm sure.. \$\endgroup\$
    – SV Savannah
    Commented Aug 12 at 6:54
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    \$\begingroup\$ Also keep in mind that the wire will melt in a flash spewing molten metal everywhere if the wire can't handle the current (50kA comes to mind as the current the system should be able to handle). \$\endgroup\$
    – kruemi
    Commented Aug 12 at 10:21

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