Ground Rods at Metal Poles

[tom baker]

From Mike Holt a video on ground rods at metal poles
For decades misguided electrical professionals have been specifying and installing ground rods at metal light poles thinking they are making the world “safer” and protecting the metal poles from lighting strikes. Despite this fact, metal light poles injure or kill people, and lighting strikes take out lights poles that have ground rods connected to them.

These events leave many in the industry with questions such as; Does a ground rod make a metal light pole safe? Does it need an equipment grounding conductor if it has a ground rod? Does a ground rod install at a metal light pole protect it from a lightning strike? These are common questions surrounded by myths in the electrical trade. Because people forget or don’t know electrical theory, ground rods are specified and installed to increase safety when, in fact, they may be creating an even greater hazard if there is a fault in the wiring.

 

[tom baker]

From Mike Holt a video on ground rods at metal poles
For decades misguided electrical professionals have been specifying and installing ground rods at metal light poles thinking they are making the world “safer” and protecting the metal poles from lighting strikes. Despite this fact, metal light poles injure or kill people, and lighting strikes take out lights poles that have ground rods connected to them.

These events leave many in the industry with questions such as; Does a ground rod make a metal light pole safe? Does it need an equipment grounding conductor if it has a ground rod? Does a ground rod install at a metal light pole protect it from a lightning strike? These are common questions surrounded by myths in the electrical trade. Because people forget or don’t know electrical theory, ground rods are specified and installed to increase safety when, in fact, they may be creating an even greater hazard if there is a fault in the wiring.

There is a very dramatic video at the end showing a lightning strike to a tree

 

[electrofelon]

The ground rod at a metal pole is ridiculous for two reasons. First is just generally what earthing would accomplish. Then there is the fact that even if it was beneficial, you have a concrete base with the pole bolted to the base so you are already Earthed. I have this great picture I took, that I can't find at the moment but it's a big high voltage distribution Tower, like a 3 ft diameter steel pipe bolted with a zillion bolts do a concrete base and has a ground rod pounded next to it with a little ground wire. Looks like Fisher-Price my first ground rod!

 

[mopowr steve]

I tried to engage Mike Holt some years ago about whether a ground rod (which seems futile) by his explanation, I argued that would it not actually benefit diverting some of the Lightning energy in the soil verses all that energy spalling/rupturing a concrete foundation during a strike. Although he remarked that he lived in the worlds most active lightning state; Florida: he didn’t offer any research/evidence that what I was conveying might be true.
Has anyone here seen an actual test (oh I don’t know is it Arizona that has a lightning testing facility?) to see what the effects of a lightning strike causes to a concrete footing. I would think the steam generated by such an event would blow the concrete apart. Especially when you only utilize the rebar/bolts in a concrete footing to carry that kind of energy.
Would love to hear others take on this!

 

[ActionDave]

......Has anyone here seen an actual test (oh I don’t know is it Arizona that has a lightning testing facility?) to see what the effects of a lightning strike causes to a concrete footing. I would think the steam generated by such an event would blow the concrete apart. Especially when you only utilize the rebar/bolts in a concrete footing to carry that kind of energy.
Would love to hear others take on this!

I can't see a lightning strike blowing up a concrete footing. Radio and cell tower bases are made of concrete and they get hit by direct strikes all the time and last for decades.

 

[mopowr steve]

I can't see a lightning strike blowing up a concrete footing. Radio and cell tower bases are made of concrete and they get hit by direct strikes all the time and last for decades.

Yes but don’t those towers have an elaborate grounding system of rod/plates/etc

 

[tom baker]

There is an IEEE paper "The use of concrete enclosed reinforcing rods as grounding electrodes" Fagan and Lee, July /August 1970.




The authors had high current discharge tests done by Westinghouse electric, ranging from 1900 to 9300 amps, no damage was found.
This paper is copyrighted so I can not post it, but it does answer the question about lightning and damage to concrete foundations with rebar

 

[ActionDave]

Yes but don’t those towers have an elaborate grounding system of rod/plates/etc

Yes they do, but that has nothing to do with the where the energy goes when a lightning bolt hits the tower. There are a fair amount of rods and plates that get installed, but all of that and more is geared toward making sure that every piece of conductive material is bonded together so that the whole site acts like a cork in a bucket when the big gush of electrons get dumped in.

There is no way any kind of ground rod, no matter how big and no matter how deep and no matter how large the conductor connected to it can compete with the amount of steel and concrete in the pilings that anchor a cell tower. The amount of electrical energy a ground rod can divert away from one of those pilings during a lighting strike would be like holding out a shovel when a dump truck drops a load of gravel. I think the same is true for a light pole base. Besides that, despite it's appearance as being indestructibly hard, concrete is porous, and has a lot of air space and flexibility engineered into it.

 

[tom baker]

Yes they do, but that has nothing to do with the where the energy goes when a lightning bolt hits the tower. There are a fair amount of rods and plates that get installed, but all of that and more is geared toward making sure that every piece of conductive material is bonded together so that the whole site acts like a cork in a bucket when the big gush of electrons get dumped in.

There is no way any kind of ground rod, no matter how big and no matter how deep and no matter how large the conductor connected to it can compete with the amount of steel and concrete in the pilings that anchor a cell tower. The amount of electrical energy a ground rod can divert away from one of those pilings during a lighting strike would be like holding out a shovel when a dump truck drops a load of gravel. I think the same is true for a light pole base. Besides that, despite it's appearance as being indestructibly hard, concrete is porous, and has a lot of air space and flexibility engineered into it.

And yes I agree, this study "A comparsion of concrete encased grounding electrodes to driven ground rods" says the same.

 

[GoldDigger]

And yes I agree, this study "A comparsion of concrete encased grounding electrodes to driven ground rods" says the same.

View attachment 2558435

But the fault currents from any of the referenced sources can be orders of magnitude lower than those of a lightning strike.

 

[mopowr steve]

Yes they do, but that has nothing to do with the where the energy goes when a lightning bolt hits the tower. There are a fair amount of rods and plates that get installed, but all of that and more is geared toward making sure that every piece of conductive material is bonded together so that the whole site acts like a cork in a bucket when the big gush of electrons get dumped in.

There is no way any kind of ground rod, no matter how big and no matter how deep and no matter how large the conductor connected to it can compete with the amount of steel and concrete in the pilings that anchor a cell tower. The amount of electrical energy a ground rod can divert away from one of those pilings during a lighting strike would be like holding out a shovel when a dump truck drops a load of gravel. I think the same is true for a light pole base. Besides that, despite it's appearance as being indestructibly hard, concrete is porous, and has a lot of air space and flexibility engineered into it.

May I ask what your feelings are of lightning rods and earthing of those systems?
I don’t have a stance about them. Just curious how we feel about them in relation to my original post.

 

[ActionDave]

May I ask what your feelings are of lightning rods and earthing of those systems?
I don’t have a stance about them. Just curious how we feel about them in relation to my original post.

If by feelings you mean opinions then I would say the earthing and bonding that goes on there is expensive. There is no doubt in my mind that single point grounding is an effective system and that auxiliary rods are a waste of time and money.

 

[K8MHZ]

The ground rod at a metal pole is ridiculous for two reasons. First is just generally what earthing would accomplish. Then there is the fact that even if it was beneficial, you have a concrete base with the pole bolted to the base so you are already Earthed. I have this great picture I took, that I can't find at the moment but it's a big high voltage distribution Tower, like a 3 ft diameter steel pipe bolted with a zillion bolts do a concrete base and has a ground rod pounded next to it with a little ground wire. Looks like Fisher-Price my first ground rod!

I have a similar picture around here somewhere.

 

[R777V]

Would the sand in the concrete mix tend to turn into glass? Or maybe too unevenly dispersed to?


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