Grounding System

The method suggested by you is incorrect for the following reasons:

1- Use of steel as a conductor is not recommended as it has a greater resistance to flow of inrush current in case of a lightining strike.

2- At the joining points of steel and copper galvanic corrosion will start after some time providing more resistance and making the system unsafe.

As such it is recommended that from the lightning arrestor an independant bare copper wire be connected to the earthing rod underground.

The main point is to have a path offering least possible resistance to the flow of current

yes ... copper as thick as possible, straight to the ground, avoid connections ... this is the only rule.

As stated by others, run the copper wire all the way down.

Without knowing your exact setup and lightning arrestor, use the manufacturers recommendation of wire size as the absolute minimum. Again, as previously stated, thick is better.

I would also ground the tower legs, tying all grounds together with appropriate clamps. Make sure the grounding rod is of good quality, (some cheap rods are steel with a thin copper plating) and deep enough, at a distance of at least one foot from the concrete base or leg footings. If in doubt, use two, on opposite sides, depending on the size and height of your tower.

A typical lighting discharge will take the path of the least impedance, so running a single equipment grounding conductor from your "lightning arrester" to one or more grounding electrodes at the base of the tower will give you the best results. The National Electric Code does not offer any minimum requirements for protecting towers against lighting strikes, only grounding requirements in terms of power to the system.

If you are receiving or transmitting a signal through an antenna, you will want to use an "antenna discharge unit" at the point just before your coax, lead in, wave guide, etc., enters the building. The ADU is then grounded with a separate equipment grounding conductor to a grounding electrode. In the event that the antenna receives a lightning discharge, the ADU will offer a degree of protection to the equipment that the antenna is connected to. You will want to bond this system to your lighting protection system as well.

As Greg G. pointed out, the more grounding electrodes in use and the larger size (gauge) of your equipment grounding conductors, the least amount of impedance you will encounter, equating to the best amount of protection.

Or you could always contact a reputable company that deals with lightning protection in your area, they should be able to design a system that will fit your needs.

Good Luck!

JLD2896,

Good point on the ADU. I was too focused on just the tower related issues. ADUs/lightning arrestors are standard procedure for any antenna leads, cable (as in data and/or TV), or phone wires immediately prior to entering a building.

Greg

Gerg G,

Thanks! I don't believe that you were too focused, I may have simply read too much into the topic and assumed that there was going to be an antenna on top. I tend to do that on occasions.

So I thought that I would simply give Siklista some additional info, just in case. Maybe I should have covered FAA obstruction lighting regulations as well..................

Thanks for your input on the original question / topic!

Take care!

Jeff

One other thing to add is a bond to the coax outer metal layer just above the bend at the bottom of the tower as it turns to enter the building. Take this conductor straight down to the earthing system. It will condut a majority of the lightning current into the grounding as high frequency lightning does not like to go around corners as evidenced by the large number of blown apart wground wires we find on power poles and towers when the installer puts a V in the wire for ease of testing.

To all that replied, thank for your comments. We shall be re-evaluating our procedures.