grounding at light poles

[john windley]

I know this is an age old question: Is there any benefit in the way of lightning protection by driving a ground rod at light poles with a GEC to the handhole grounding terminal?

 

[raider1]

Welcome to the forum.

IMHO, there is no benefit to installing a ground rod at a light pole. The light pole will be most likely mounted to a reinforced concrete base with large steel bolts. This would act as a concrete encased electrode so the addition of a ground rod would be meaningless.

Chris

 

[M. D.]

any ?? insignificant I'd say ,. though I am no expert

http://www.imsasafety.org/journal/mj04/1.pdf

 

[tom baker]

I call these time and material electrodes.
There is a IEEE paper that states the concrete in the foundation is fairly conductive and will itself make an adequate ground.
But its commonly specd, due to lack of understanding. Often its in boiler plate that just doesn't get changed. I have seen boiler plate specs allowing Westinghouse lamps, they have not made lamps for 30 years.

 

[john windley]

Concrete is "fairly conductive"??, which leads me to believe that adding a rod may help? I've heard of lightning actually cracking concrete bases. Could adding rod(s) possibly help eliminate that? Thinking that the lightning may travel to earth through the rod instead of the base??

 

[iwire]

I've heard of lightning actually cracking concrete bases.

I have seen direct lightning strikes blow the cement cornice of the building.

Thinking that the lightning may travel to earth through the rod instead of the base??

Not instead of, only in addition to.

 

[JayP]

I have actually injected low voltage currents into concrete foundation slab of substation transformer to prove it will conduct. It does and more rebar increases it.

I also know it would help with lightning dissipation from my telecomm days.
If you're in a lightning prone area, it could be worth it.

 

[john windley]

Does anyone know if there has been a simple megger test that shows a decrease in ohms to ground when a rod has been added to a pole? That would prove it is helpful, obviously to what extent is unknown.

 

[benaround]

Does anyone know if there has been a simple megger test that shows a decrease in ohms to ground when a rod has been added to a pole? That would prove it is helpful, obviously to what extent is unknown.

At 186,000 miles per second it will have to be a quick test !!

 

[mcclary's electrical]

Does anyone know if there has been a simple megger test that shows a decrease in ohms to ground when a rod has been added to a pole? That would prove it is helpful, obviously to what extent is unknown.

A megger is not the right tool to test this. You need to check resistance to ground. I'd like to check a pole,,,,,,then add one rod,,,check,,,,then add two,,,check. I wonder if the pole was at say(for example) 22 ohms resistance, do you think the rods could drop it to a little less?

 

[benaround]

Mcclary,

I'll bet it would increase the resistance by adding rods, what do you think ?

 

[jwnagy]

I have seen concrete pole bases that have broken in a number of pieces (exploded) from a lightning strike, especially if the base is new/fresh and still has alot of moisture inside.