Is lightning rod system of copper pipe OK?

Thread Starter

Nick_28

Joined Nov 24, 2019
3
Dear all,
Is it dangerous to make the lightning system of copper pipe? Is it going to explode when will it be hited by lightning? Thank you!
 

SamR

Joined Mar 19, 2019
1,503
Welcome to AAC! The concept of lightning suppression is to drain the potential difference to prevent a strike. It's not there to attract lightning but to prevent it. Once a strike occurs not much can withstand the enormous amount of energy being transferred.
 

Thread Starter

Nick_28

Joined Nov 24, 2019
3
A pipe would allways have some vapors inside which may heat instantly and may produce an explosion when a strike occurs. Is there anyone who used pipe to make a lightning system? Is it safe?
 

AlbertHall

Joined Jun 4, 2014
8,789
There was a glider accident where it was struck by lightning. An aluminium tube was crushed by the magnetic field but presumably a copper tube, being stiffer, would be more resistant to this kind of damage. The AIB report on the accident is linked below and includes the text below:
The bellcrank and the outer articulation rod were not recovered but most of the long centre rod,
which was made from an aluminium alloy tube of 16 mm outside diameter and 1 mm wall
thickness, was recovered in one section. This tube had suffered burning and arc erosion at each end
close to its jointed connections, which were missing, and it exhibited an unusual form of damage
over its entire length. It had 'collapsed', or had been 'crushed', as a result of the intense magnetic
field generated by the conduction of the lightning current, to form an almost solid irregularly
shaped 'bar';

https://assets.digital.cabinet-office.gov.uk/media/542300e540f0b613420009cf/dft_avsafety_pdf_500699.pdf
 

SamR

Joined Mar 19, 2019
1,503
It wouldn't even need liquid. The air expansion alone would do it. Once again, the idea is to prevent a lightning stroke from forming and not to channel one that has occurred. You should read what little is available on lightning suppression. There is also the pointy part of aerials mentioned. I have, in fact, made aerials from heavy wall aluminum tubing welded to a roof mounting plate that had a split bolt connector welded to the plate for the 2/0 grounding wire. Aerial end of tubing chamfered to sixty-degree angle to get the "pointy part" and small hole drilled in tubing at baseplate to drain water. They have never been struck by lightning.
 

SLK001

Joined Nov 29, 2011
1,541
A lightning strike is initiated by what are called "streamers". A "streamer" is an invisible stream of electrically charged particles emanating from a source. When a "streamer" from point A meets a "streamer" from point B, a lightning bolt forms between these two points. A lightning rod attracts and dissipates close by "streamers", thus preventing a bolt from forming.
 

Tonyr1084

Joined Sep 24, 2015
3,913
A lightning strike is initiated by what are called "streamers". A "streamer" is an invisible stream of electrically charged particles emanating from a source. When a "streamer" from point A meets a "streamer" from point B, a lightning bolt forms between these two points.
I was standing on the receiving dock (in Houston Texas where 20% chance of rain means 20% of Houston WILL get rained on - often with strong lightning {Summer time}). A colleague of mine and myself were standing, talking when we heard this crackling sound (Streamers). Almost immediately after that we saw the flash (the light from the flash not the bolt) and less than a second later the crash of the thunder. It was daytime. But it would have been interesting to see those streamers, as they CAN be seen sometimes at night. Still, the parking lot lights would have probably obscured them.

But yes - @SLK001 is correct. I've known of this phenomena and have seen pictures in extreme slow motion exactly how they form under lab conditions. Spikes with high charges from below and a single spike from above also charged opposite potential. Each spike wold emit a growth of these streamers. When one of the lower streamers would touch one of the upper streamers you'd get the flashover where all of the energy would be conducted through that single plasma path.
 

sagor

Joined Mar 10, 2019
122
@ Samr, my philosophy is a bit different. One cannot control when or where lightning will hit, all you can control is what you do with that energy. I use copper pipe as ground rods, bonded to copper strapping along the top (just below surface). That is all tied to my ground in the electrical panel, as well as back to my tower (which has its own grounded copper strapping).
I took a lightning hit somewhere about 2 years ago, but from what I could tell, the strike hit the grounding wire (6 gauge) from my solar panels, as all the tie wraps holding it to the building were blown off (bare stranded wire was wet from rain). My copper pipes survived.
As ground rods, pipe is ok, as even if it tries to "explode", it is below ground, and the material stays there still "conducting". Externally, I would not use pipe, but instead use 2" copper strapping. It has less inductance than heavy gauge copper wire. This is important since lightning contains a lot of RF frequencies (mostly below 1Mhz), and low inductance is more important than size of copper.

One cannot "prevent" any lightning hit, nature is just too unpredictable. All one can do is prepare for it...
 
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SamR

Joined Mar 19, 2019
1,503
Yup lightning doesn't strike from the sky. It actually starts from both the ground and sky meeting somewhere between to form the full stroke of lightning. Also... Coming home from work in a heavy downpour, when I got home I put my briefcase over my head to keep the rain off my glasses as I left the car. Lightning struck a way off but the aluminum metal frame of my briefcase collected enough of a charge to short to my hand in a static discharge that zapped me pretty damn good. Lightning strikes are not a pinpoint event.
 

SamR

Joined Mar 19, 2019
1,503
There is no such thing as Preventing a lightning strike but you can lessen the odds greatly with a suppression system. In an imperfect world, it is all you can hope for.
 

MaxHeadRoom

Joined Jul 18, 2013
19,421
I just pick up the 8ft copper plated steel ground rods from the local electrical supplier.
They probably stand up a lot more when pounding them in.
Personally would never use copper pipe, for the sake of a couple of $$'s.
Should be OK if it is already buried and is a water supply etc.
Max.
 

sagor

Joined Mar 10, 2019
122
I don't pound the copper pipes in. With mostly clay where I live, I crimp the end of the pipe to make a reduced "outlet", connect a water hose to the other end, and "water drill" the copper pipe into the ground. Works like a charm. Every location has different issues for ground rods... Use what works for you...
I would not use a buried copper water supply line with actual water in it as a lightning ground, any quick thermal expansion of the pipe/water could crack it and cause a water leak.
Don't forget to install "whole house" surge protection in your main electrical panel. That is what saved most things when I got hit. Only failures I had were things connected by wired Ethernet. I never thought of putting lightning protection on wired Ethernet, never suspected that would be a cause of zapping my TV and 2 computers as they were wired in.... I figure the EMP is what got into that wiring. Everything else electrical survived.
 

SamR

Joined Mar 19, 2019
1,503
I have actually "salted" a driven antenna ground rod. Drive rod, cup out around the top of it, dump in a box of rock salt. Never owned a megger so don't know if it was really needed or not. I always specified megging on new rod installation at work and there was a PM program in place to periodically test them by megging.
 

SamR

Joined Mar 19, 2019
1,503
We have to follow the electrical codes. In my area, it calls for 2 rods.
Are you in Canada? Max keeps saying that but here in Georgia we only drive one rod for panel grounding. At work megging was speced and I can't remember if that was per NEC or Corporate standards. If megging failed then we drove a 2nd rod. And we used 10' rods at work. Gotta find my NEC code book, had it my hands a few weeks ago and now can't find it.
 

MaxHeadRoom

Joined Jul 18, 2013
19,421
I would not use a buried copper water supply line with actual water in it as a lightning ground, any quick thermal expansion of the pipe/water could crack it and cause a water leak.
Commonly used here, the neutral is bonded to the incoming copper water supply for Ground reference..
Max.
 

SamR

Joined Mar 19, 2019
1,503
Commonly used here, the neutral is bonded to the incoming copper water supply for Ground reference..
Also allowable standard NEC practice where ground rod cannot be driven. IE rocky soil. Not up on the codes for commercial and multiunit housing construction.
 

Reloadron

Joined Jan 15, 2015
4,701
Are you in Canada? Max keeps saying that but here in Georgia we only drive one rod for panel grounding. At work megging was speced and I can't remember if that was per NEC or Corporate standards. If megging failed then we drove a 2nd rod. And we used 10' rods at work. Gotta find my NEC code book, had it my hands a few weeks ago and now can't find it.
The problem with the NEC Code here in the US is not only the changes, my last revision was 2008, but the fact that state and even local codes can trump the NEC. Most states and localities just run with the NEC rather than regulate their own codes but not all.

Lightening rods aside for a moment and a focus on Residential US Grounding and only residential. This is where the NEC mentions:
250.53 Grounding Electrode System Installation.

(D) Metal Underground Water Pipe.
Where used as a
grounding electrode, metal underground water pipe shall
meet the requirements of 250.53(D)(1) and (D)(2).


(2) Supplemental Electrode Required. A metal underground
water pipe shall be supplemented by an additional
electrode of a type specified in 250.52(A)(2) through
(A)(8). Where the supplemental electrode is a rod, pipe, or
plate type, it shall comply with 250.56.
The supplemental
electrode shall be permitted to be bonded to the grounding
electrode conductor, the grounded service-entrance conductor,
the nonflexible grounded service raceway, or any
grounded service enclosure.


250.56 Resistance of Rod, Pipe, and Plate Electrodes. A
single electrode consisting of a rod, pipe, or plate that does
not have a resistance to ground of 25 ohms or less shall be
augmented by one additional electrode of any of the types
specified by 250.52(A)(4) through (A)(8). Where multiple
rod, pipe, or plate electrodes are installed to meet the requirements
of this section, they shall not be less than 1.8 m
(6 ft) apart.

So as we see we start hopping all around. What it comes down to is that if a single ground is adequate then a second is not required. One needs to muddle through all of this or be doing it daily to know exactly how to apply the code. :)

As to lightening? My own observation over all of my years is that the predictably of lightening is that it is totally unpredictable. Sometimes things do not behave quite the way we seem to think they should and lightening is one of those things. A friend of mine has a nice home in a country setting. Nice home surrounded by tall, very tall trees. The trees are at least twice plus the height of the house and then some. When lightening struck it hit his fireplace chimney none of the much taller wet trees. My friend and his kids were in the den where the fireplace is. The strike was so intense it made super heated steam out of moisture in the brick and mortar fireplace. The fireplace literally exploded sending glass chars and bricks into his den. They were cut up a little but OK. The lightening decided it liked the chimney better than the trees I guess.

My observation is simple. When a major lightening strike happens lightening rods and similar are reduced to a blob of molten metal. Good grounding may help with a small strike in close proximity but a major strike and everything in its path is toast.

Just My Take
Ron
 

nsaspook

Joined Aug 27, 2009
6,595
The NEC ground rod specs are for electrical safety not lighting protection. Our station antennas/receiver/transmitter facilities would get lightning strikes several times a month will no damage to equipment or the RF grounding system because we had real lighting protection installed in addition to electrical safety grounding.
 

Reloadron

Joined Jan 15, 2015
4,701
The NEC ground rod specs are for electrical safety not lighting protection. Our station antennas/receiver/transmitter facilities would get lightning strikes several times a month will no damage to equipment or the RF grounding system because we had real lighting protection installed in addition to electrical safety grounding.
Absolutely and you guys are a commercial station. The Empire State Building is home to dozens of commercial antennas and they average two strikes a month. Interesting is that when the building takes a hit lightening does not always strike the very top antennas, the building also gets strikes on the sides. NSA Spook, does lightening always strike the top of your tower or does it also strike the sides? Just a curiosity thing. :)

Real good point as to electrical safety (NEC Code) verse lightening protection.

Ron
 
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