Ground Rods at Light Poles

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charlie b

charlie b

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250.32(A) tells us it is not required. I keep encountering people who cling to the urban legend that they, somehow, provide a necessary protection. I can make the case for a shock hazard, given that the EGC, and not the ground rod, provides protection. But what about lightning strikes? I am debating one person who cites instances in which lightning struck a light pole that did not have a ground rod, and citing the damage that the pole suffered. I want to counter-claim that the presence of a ground rod would not have altered the results, would not have prevented or even reduced the damage.

Am I right? Does anyone have any real-life evidence to back my point of view?
 
I once attended a Mike Holt class, and he ridiculed the idea that a ground rod would make a difference.
 
I think you need to measure resistance with and without the rod, or if rod is in the concrete at two different poles but with similar base design in similar soil type.

small posts with luminaires may not have much of a base but parking lot lights and such on 20' plus poles will have big enough base that just the rebar in the base makes just as good if not better electrode than a single rod does IMO, even if it doesn't quite meet the NEC requirements of a CEE.
 
Charlie, if lightning makes a direct hit there is no way a rod will reduce the damage or even reduce the damage enough to make a difference. I have seen a house get hit that had chemical ground rods installed around the perimeter of his home but he lightning still got all his electronics. A direct hit is one thing but a hit from a surge is another. I am not sure a rod would help much but I guess there is a point at which it could.....
 
Dennis Alwon said:
Charlie, if lightning makes a direct hit there is no way a rod will reduce the damage or even reduce the damage enough to make a difference. I have seen a house get hit that had chemical ground rods installed around the perimeter of his home but he lightning still got all his electronics. A direct hit is one thing but a hit from a surge is another. I am not sure a rod would help much but I guess there is a point at which it could.....
Click to expand...
another good point, direct hits usually going to be some damage regardless what kind of electrode or resistance it has
 
Do most light poles not have concrete footing with rebar?

Ground rods come from the day when it was thought that soil did everything besides turning the prime mover.
 
I had a customer that lived on top of a hill, lighting continuously took out his fence charger. He was at the end of the poco line. Drove three ground rods at the house, three at the barn, and three at the last poco pole. He has had no more issues. Had another one below a rock quarry that every time a storm would come up, it would blow out his phones and tv’s, drove two more rods at his service, buried a bare copper wire in the yard to bond the phone and TV lines to the service (phone and tv came in at the other end of the house). No more problems. Most likely the surges were coming in from the cable and phone, and since they weren’t bonded to the service, I believe that was the biggest issue.
 
mbrooke said:
Do most light poles not have concrete footing with rebar?

Ground rods come from the day when it was thought that soil did everything besides turning the prime mover.
Click to expand...
Yeah, and usually the ground rod is just thrown into the pour, and not even tied to the rebar, so doesn’t really do a whole lot of good.
 
I recall an article from a power utility a long time ago that suggested that where they had concrete pole bases, they could reduce the damage to the concrete from a lighting strike to the pole by adding a ground rod outside the pole base or by doubling up on the wire ties used to secure the re-bar. Not sure of the actual source and if there were any actual studies on the issue. They suggested that the damage to the pole base was from the lighting current turning the moisture in the concrete into steam and the volume expansion of ~1700 would damage the concrete.
 
Once you are discussing lightning actually striking the pole, I don't think you can have a useful discussion on the basis of theory. The best you could do is find an actual study of events, for example if the article mentioned in post #9 actually had pole base damage stats.

As a related aside about how powerful a lighting strike can be:
A couple of days ago I learned that small fraction of lightning strikes accelerate electrons enough to cause gamma emission, to the extent of detectable levels of nuclear activation (the gamma rays are energetic enough to knock neutrons out of a nucleus, making it radioactive) and pair creation (the gamma rays are energetic enough to hit something and create an electron and a positron). Yes, lightning can in come cases generate very small quantities of antimatter. Given the energy available it is pretty useless to try to argue how lightning will affect a structure based on theory, you need data.

www.nature.com

Mystery gamma rays could help solve age-old lightning puzzle

Researchers in Japan are enlisting an army of citizens to explore how storms on Earth create extreme bursts of gamma radiation.
www.nature.com www.nature.com

-Jon
 
winnie said:
Once you are discussing lightning actually striking the pole, I don't think you can have a useful discussion on the basis of theory. The best you could do is find an actual study of events, for example if the article mentioned in post #9 actually had pole base damage stats.

As a related aside about how powerful a lighting strike can be:
A couple of days ago I learned that small fraction of lightning strikes accelerate electrons enough to cause gamma emission, to the extent of detectable levels of nuclear activation (the gamma rays are energetic enough to knock neutrons out of a nucleus, making it radioactive) and pair creation (the gamma rays are energetic enough to hit something and create an electron and a positron). Yes, lightning can in come cases generate very small quantities of antimatter. Given the energy available it is pretty useless to try to argue how lightning will affect a structure based on theory, you need data.

www.nature.com

Mystery gamma rays could help solve age-old lightning puzzle

Researchers in Japan are enlisting an army of citizens to explore how storms on Earth create extreme bursts of gamma radiation.
www.nature.com www.nature.com

-Jon
Click to expand...

Question is, does the anti matter do anything?
 
iaeimagazine.org

Are Your Streetlights Grounded?

It had been raining and the sidewalk was wet. This had been one of those summer storms where the temperature outside was a balmy 78 degrees. So the children playing on the sidewalk were in short pants, some were barefoot. One of these barefoot children, eight-year-old Sarah, was chasing Eric...
iaeimagazine.org iaeimagazine.org

I had a post a while back about local light poles not owned by the utility company, and their need for proper grounding. the above article was something I stumbled upon during my research to confirm the need for proper grounding at light poles.

I did not include lightning into my argument at the time.
 
mbrooke said:
Question is, does the anti matter do anything?
Click to expand...

The small amount of antimatter is in the form of positrons. They pretty much immediately annihilate with a nearby electron to emit a gamma ray. So the only thing this does is cause a bit of gamma 'after-glow' following the initial gamma producing event.

-Jon
 
winnie said:
The small amount of antimatter is in the form of positrons. They pretty much immediately annihilate with a nearby electron to emit a gamma ray. So the only thing this does is cause a bit of gamma 'after-glow' following the initial gamma producing event.

-Jon
Click to expand...

Alright, but nothing to do with avagadroes constant, correct? Or actual copper disapering in any sense.
 
dkidd said:
I once attended a Mike Holt class, and he ridiculed the idea that a ground rod would make a difference.
Click to expand...
There's a great video Mike did, probably similar or the same as you were talking about, where he shows a picture of this giant lighting bolt and he says, "now I don't know if you've done any critical thinking, but if you think a ground rod at the bottom of that light pole is going to do anything......"

Now even if we were to grant that grounding the light poles is advantageous, I would argue the anchor bolts/concrete base/ rebar is already a "ground rod" , you already have one so I don't see what the point of adding another one is.
 
Rock86 said:
iaeimagazine.org

Are Your Streetlights Grounded?

It had been raining and the sidewalk was wet. This had been one of those summer storms where the temperature outside was a balmy 78 degrees. So the children playing on the sidewalk were in short pants, some were barefoot. One of these barefoot children, eight-year-old Sarah, was chasing Eric...
iaeimagazine.org iaeimagazine.org

I had a post a while back about local light poles not owned by the utility company, and their need for proper grounding. the above article was something I stumbled upon during my research to confirm the need for proper grounding at light poles.

I did not include lightning into my argument at the time.
Click to expand...

That article basically does not have anything to do with grounding electrodes as asked about in the OP.
 
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