Off grid grounding technique?

icarusicarus Solar Expert Posts: 5,108 ✭✭✭✭
Ok all you smart guys out there. As many of you know I have struggled with grounding issues for a long time with my system. A little background. We live on a small island in the middle of a big lake in Northern Ontario. Lightning is a real consideration. The neighbouring bush camp we managed for years has lost a number of buildings due to lightning over the years, including one that burned due to a outlet box blowing off the wall.

Our island is on granite, with a thin layer of duff, some places have sand/clay/gravel mixed with large glacial stones. Very few spots can a hole be dug more than ~2' without hitting bedrock. My father who owned the place before us, grounded all his ham antennas, and the buildings with a piece of stiff steel wire, running off the roof (and the antennas) down to the ground, and then into the lake water. When he bought the first genny in 1949 the genny system went ungrounded for decades. Eventually I grounded the gennies with the same techinque.

A few years ago I built a new house (the one pictured above) that is completely independent of any other buildings. Someone who used to work for Manitoba Hydro suggested that grounding into the lake was crazy, as a near strick in the water would run up the wire and cause trouble.

So my current situation is this: I have a tall vertical antenna (20') mounted on the roof, as well as the small PV array, and a steel chimney. I have bonded all these together with a single piece of insulated #4 wire, carried down off the roof. When the wire meets the ground it runs through the duff for ~75', the last 50' or so I have stripped the insulation off the wire as it lays on the ground. The wire terminates on a zinc ground rod, with the wire coiled around the rod to increase it's contact area. The rod is then buried in a 5' deep pit of sand and coarse gravel, terminating at bedrock.

Previously I had the electrical system neutrals and ground buss tied to this system, until it dawned on me that a lightning strike on the roof system would run right into the building on it's ground wire. I realize that a direct strike on the roof of the building is probably going to damage all kinds of stuff, but I think the roof system is as good as I can get, unless I put it into the lake again. (We had 60 years of success with that system!)

I could probably live with keeping the 120/vac and 12vdc systems ungrounded as I think the potential for shock is pretty small, but I would like to have it done right.

I believe that I have asked this question in part(s) before but this is the whole picture. My intuition would be to send the building/lightning ground into the lake, and then send the electrical neutral/ground buss ground to the pit.

OK,

Balls in you guys court.

Tony

Once again thanks for you help in advance.
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Comments

  • KamalaKamala Solar Expert Posts: 452
    Re: Off grid grounding technique?

    I'm pretty sure that I am correct in saying that the lightning protection system should be completely separate from any other electrical systems. It is a diversion tactic.

    Intuitively, it seems to me that the lake would be a better ground, in which to divert lightning, than the "ground." At least in your case where you can't make a good dirt ground connection. What about the lake bed? I dunno. How do large vessels manage lightning protection without a good "earth" ground?

    K
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Off grid grounding technique?

    tony,
    as far as grounds go, you won't get much better than the lake unless it were salt water like in the ocean. the guy from your hydro company really doesn't seem to know as much as one would expect him to know because in your area the lake is the place it'll want go and then into the earth under the lake.
    did you read the article i posted about deep earth grounds? care to take a resistance measurement to the lake? it will be below 25 ohms for an 8ft ground rod i'm sure. and if you heard of the west virginia miners that died a few years back, it was the lightning traveling underground from above that gave them all their troubles so i doubt it would ever hit the lake and then travel up your ground wire.
    for your place i would do a faraday shield as lightning going down your antenna and cable and through your house is a real danger just by the height and close proximity to such a good ground. i'd do 4 leads, one at each corner of your place. ground those leads to the lake as well ending up with at least 2 connections to the rod from the faraday shield. i say 2 because the far side can just be tapped onto the closer ground leads. oh, and rocks on top of the ground leads are fine if you are carefull not to walk on them as this could stress and break the wire.
    i also seem to remember advising you to use the lake as a ground long ago and your daddy wasn't wrong and lightning never jumped out of the lake to him now did it?
  • KamalaKamala Solar Expert Posts: 452
    Re: Off grid grounding technique?

    The lake in question might actually have good ionic concentrations. Not so much derived from minerals but from acidic organic compounds. Pine trees?
  • icarusicarus Solar Expert Posts: 5,108 ✭✭✭✭
    Re: Off grid grounding technique?

    We used to have a submarine hand cranked telephone line than ran 5 kms down the lake to the other island. Every time lighting would strike the lake the phone would ring! You could tell how close it was by the loudness of the ring!

    Tony
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Off grid grounding technique?

    i had a funny thought, but i'll keep that to myself. anyway, you didn't get electrocuted, did you? i mean you are still here, right?;)
  • icarusicarus Solar Expert Posts: 5,108 ✭✭✭✭
    Re: Off grid grounding technique?

    So Neil,

    Please describe your Faraday cage idea. I understand 4 ground wires from the 4 corners of the building, but I am not clear what you are describing as the Faraday cage.

    Also, in the near future I plan to install standing seam steel roofing. I would assume that the steel roofing in the would create a Faraday cage, and I could ground off the four corners. But in the meantime with asphalt roofing how should I accomplish this. I assume then that I should then sent the panel ground to the lake on a separate wire?

    Tony
  • BB.BB. Super Moderators, Administrators Posts: 28,176 admin
    Re: Off grid grounding technique?

    Have you been "hit" by lightning in your knowledge?

    Just "sinking" some 10's of feet of wire (as much as you wish to $pend) into the lake bottom muck will probably be as good as it gets... The lake itself is probably not very conductive.

    That is why people are warned to get of of lakes/pools during a thunderstorm. The human body (with all of the salt/ions/water) is relatively very conductive--so the any and all current "in the area" will try and go straight through the body (finding "ground").

    Given that you are near the water's edge--your location probably has a much better chance of attracting a strike than the nearby lake would (increases the odds of your home/area being hit).

    There are probably several effects of atmospheric electricity..

    The first is the normal charge of 100 to several hundred volts per meter (which can exceed 10,000's of volts per meter pre-strike). Metal objects (particularly tall objects) being grounded to earth (does not take a low resistance connection). This prevents a person from walking up to a tower from getting shocked (pretty nasty one because large tower has lots of capacitance). As HAMs know--even an antenna on a tower can pick up a charge if the cable is left open at ground level.

    Here is a good point of discussion... There are several things that attract lightning... Sharp Points and Voltage differential. Sharp points are great (or at least) for lightning rods to attract lightning within a few 10's of feet to hit it, instead of something nearby (and cause damage/start fire). The other is grounding a tower/object increases the electric potential to attract a lightning strike...

    So any grounding can attract lightning, and physical metal objects do to...

    Now that you have put up your lightning attractor--it seems like a good idea to safely route the energy via braid copper cable from the lighting rod / metal structure to earth.

    I will leave it to professionals to better describe the requirements for a Lightning Protection System. From page 2 of their little FAQ:
    [FONT=Arial, Helvetica, sans-serif]Who Needs Lightning Protection?[/FONT]
    [FONT=Arial, Helvetica, sans-serif]Lightning can strike anywhere and do millions of dollars worth of damage. Lightning is to blame for more deaths and property loss than tornadoes, hurricanes, and floods combined. And although we cannot yet predict where lightning will strike, there are some factors that increase the risk of a lightning strike. If your home or business meets 5 or more of the following criteria, you are in a high risk group. [/FONT]
    • [FONT=Arial, Helvetica, sans-serif]has had previous lightning damage[/FONT]
    • [FONT=Arial, Helvetica, sans-serif] is located in an isolated, open area[/FONT]
    • [FONT=Arial, Helvetica, sans-serif]is located on a hill[/FONT]
    • [FONT=Arial, Helvetica, sans-serif]located near a large body of water [/FONT]
    • [FONT=Arial, Helvetica, sans-serif]is located in an area that has a high number of thunderstorms [/FONT]
    • [FONT=Arial, Helvetica, sans-serif] has tall trees overhanging the roof [/FONT]
    • [FONT=Arial, Helvetica, sans-serif]has metal, brick or stone chimney brick [/FONT]
    • [FONT=Arial, Helvetica, sans-serif]has metal ridge vent [/FONT]
    • [FONT=Arial, Helvetica, sans-serif]has aluminum siding [/FONT]
    • [FONT=Arial, Helvetica, sans-serif]has no surge protection [/FONT]

    My two cents--If you do not install a lightning protection system--almost anything else you do is not going to help much (grounding structures, towers, arrays, etc. Routing the Lightning System cable away from any other cables/wiring/sensitive electronics will be a big help (prevent capacitive and inductive coupling from LS to other stuff).

    However, there is the counter argument (as I understand it) if you do nothing to overtly attract the lighting--it will as likely find somewhere else to strike and if you keep your equipment separate from the "earth" then nearby strikes will not create potential across your equipment (i.e., two points in the ground 50' apart may have hundreds or thousands of volts of differential potential from a nearby strike). Creating a single ground point to reference all "in-house" and "around house" electrical equipment will help reduce the issue of ground potential.

    If I recall correctly, Solar Guppy (who is in Lightning Central) -- believes in isolation (disconnecting arrays from building/inverters/charge controllers) and avoiding grounding of his solar arrays and their aluminum frames. Both reduces the changes of a strike--and limits the possibility of a nearby strike of coupling into his equipment. And it seems to work for him (not trying to put words in SG's posts--search around for his other posts that describe what he recommends and his results--no damage, as I recall--Not quite sure that I believe that his practices are as "untrained human" safe as heavy ground would be; and no human should be out and about in a lightning storm anyway--But they seem to work for him).

    Remember, lightning contains both high currents and high frequency--so following good RF practices (as well as lots of copper/aluminum) helps.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,108 ✭✭✭✭
    Re: Off grid grounding technique?

    Almost too much to chew on. Using your list, I have almost all of the above in spades.

    Perhaps the weakest link is the 20' tall vertical antenna, and the steel chimney. The Pv array is 15' away.

    I heard once, and have no recollection of where, the real way that lightning work is that they provide such a good path to ground that they (can) dissipate enough static energy such that a lightning strike doesn't happen. In the event that it does strike, the rods and the ground wires then can direct the strike off the to reduce or eliminate damage.

    I suspect that I am stuck between a rock and a hard place on this. (no pun intended!) By providing a good path to ground, my chances of getting struck are greater, but if I do I will be somewhat protected. Heads you win/tails I lose.

    To answer our first Question Bill, we have been struck pretty close to the buildings over the years, usually striking a tall tree, working it's way down the tree, often jumping to another, and then into the duff. One time it found a #4 copper wire that was wired to a Charge controller and battery bank. It was 100' away, and it toasted the CC, a couple of 12v radios and nothing else. Lucky I guess.

    I do think the steel roof will add a level of protection assuming it is grounded.

    Tony

    PS One thing I have is miles of #4 solid copper wire. The folks I used to work for had miles of overhead wire on insulators that I replaced with UF a few years ago. I spooled up and saved several thousand feet!
  • BB.BB. Super Moderators, Administrators Posts: 28,176 admin
    Re: Off grid grounding technique?
    icarus wrote: »
    I heard once, and have no recollection of where, the real way that lightning work is that they provide such a good path to ground that they (can) dissipate enough static energy such that a lightning strike doesn't happen. In the event that it does strike, the rods and the ground wires then can direct the strike off the to reduce or eliminate damage.

    Does not make sense to me--but I will not claim to be an expert in the field... I go with -- anything that makes conduction easier will draw a strike (sharp points, ionized air such as a radionuclide on the tip of a rod, something conductive that is at a greater potential difference with respect to the source of the lightning, etc.).

    From what I have read about items that are intended to reduce the "field" in an area (ball of spikes?) to dissipate lightning before it strikes, they do not work; Charge Transfer System:
    Charge Transfer System is Wishful Thinking, Not Science
    New Mexico Institute of Mining and Technology, Socorro, NM 87801
    Langmuir Laboratory for Atmospheric Research
    November 24, 2000
    Jodi Haasz
    Standards Board
    Standards Activities
    IEEE- Power Engineering Society
    ...
    Piscataway, NJ 1331-1331
    Subject: Project Number P1576 (Proposed Standard for Lightning Protection System Using the "Charge Transfer System" for Industrial and Commercial Installations.)
    Dear Administrator Haasz:
    The purpose of this communication is to recommend that the IEEE be extraordinarily careful in its consideration of the proposed standard. Before a standard for the use of "Charge Transfer Systems" is issued, the Standards Board members should obtain and assess information on the electrical responses by these devices under active thunderstorms that has been measured by competent, independent investigators.
    The present consensus held by members of the lightning and thunderstorm electricity community in both the American Geophysical Union and in the American Meteorological Society about these devices is that they are replays of Benjamin Franklin's original, failed ideas about lightning rods. In the course of some parlor experiments, he and his associates discovered that they could discharge electrified objects silently, without sparks, by approaching them while holding a sharp-tipped needle directed at the object. This discovery of the "point discharge" or "corona current" phenomenon led Franklin to suggest that, perhaps, thunderclouds could similarly be discharged, thus preventing lightning, by taking away its electricity. However, after Franklin erected a sharp-tipped iron rod for this purpose, instead of discharging a thundercloud passing above, his rod was struck by lightning. Thereafter, Franklin recognized that a primary function for an elevated rod was to be a lightning receptor and to carry the lightning to Earth, around structures that were to be protected.
    Despite this new and unexpected function that his rods appeared to serve, Franklin (1767) remained enamored of the "power of a point" and recommended that the tips of lightning rods be sharp, a configuration that is still widely used today although the virtue of having sharp tips on lightning rods has never been established. Our assessment of the experience gained since Franklin's time is that sharp rods and "dissipation arrays" exposed in isolation on high towers are often struck by lightning but there is no credible evidence that they prevent lightning, which usually initiates high up in thunderclouds...
    Back to Tony:
    I suspect that I am stuck between a rock and a hard place on this. (no pun intended!) By providing a good path to ground, my chances of getting struck are greater, but if I do I will be somewhat protected. Heads you win/tails I lose.
    I suspect you are correct.
    To answer our first Question Bill, we have been struck pretty close to the buildings over the years, usually striking a tall tree, working it's way down the tree, often jumping to another, and then into the duff. One time it found a #4 copper wire that was wired to a Charge controller and battery bank. It was 100' away, and it toasted the CC, a couple of 12v radios and nothing else. Lucky I guess.
    Less lucky and more a standard operating procedure? :confused:

    For DC circuits--I wonder that any lightning suppressor is ever going to be fast enough and work at a low enough voltage to protect anything. If a Lightning Suppressor is installed--my suggestion would be to always install "pairs"--For example, install one on the + lead and the - lead. That way, ideally, both would fire at the same time and prevent on terminal from attaining a different voltage vs the other (engineering speak, prevent a common mode current/voltage spike from turning into a differential mode spike which will toast the input circuitry--most circuits can withstand common mode energy injection better than differential mode injection).

    Which would lead to another protection device... Basically wrap a couple turns of cable around a loop of steel, ferrite, copper conductive band, etc. Basically you make a common mode Choke to prevent common mode lighting energy from entering your equipment (this is commonly done to reduce RFI emission and susceptibility for FCC/CE compliance--should help with lightning--maybe--depends on the energy levels--and RFI was typically a concern >30 MHz--protecting against 10kHz or less is something I would have to think about to design a "proper" common mode choke--I.e., more Googling ;)--but not tonight :p).
    I do think the steel roof will add a level of protection assuming it is grounded.
    Not really. Steel is a poor conductor... Joints are not made to be electrically secured, still need way to "capture" the energy and move it safely off the building.

    More on roofs (including metal) Specifications for Lightning Protection ASAE Engineering Practice (PDF Download)
    Metal roofing and siding, eave troughs, downspouts and other metal parts are not acceptable as substitutes for lightning conductors. A lightning conductor system shall be applied to the metal siding of a metal-clad building in like manner as on buildings without such metal coverings.

    Down conductors, which are continuations of roof conductors, shall be as widely separated as possible at diagonal corners of rectangular buildings, and diametrically opposite on cylindrical structures.
    Treating a metal roof like a conductor where the A/C (high frequency current) flows at the outside or skin of the wire (and why a proper lightning control cable is braided fine wires instead of a chunk of #4 copper)--the skin depth of lightning:
    Most lightning current energy is below 10 kHz. While there is some energy at 100 kHz, very little remains above 1 MHz. In this case, the design point for frequency might be at least 10 kHz, which means that conductors over 0.052" (1.3 mm) thick (representing a skin depth of 0.026" (0.66 mm) on each side of the conductor) have reduced conducting efficiency.
    ...
    The skin-depth effect means that copper straps about 1/16" (1 mm) thick will tend to outperform round wire of the same cross-sectional area, since the full cross section of the strap will conduct high current. Admittedly, wire (particularly stranded wire) is much easier to install, join, and change direction than straps. Flat-braid cable is a good alternative for vibration resistant and highly efficient grounding, which is why it is commonly used in aircraft-grounding applications.
    ...
    The length of the cable increases the impedance dramatically. Larger-diameter cables have slightly less impedance, due to the larger surface area. The benefit of larger diameter is less significant for resistive impedance, due to the skin-depth effects.
    So... The last clip would indicate that running 100' of #4 copper solid wire (just a SWAG) underground/underwater is of limited use... The "voltage drop" due to A/C impedance (DC Resistance is not the limiting issue) means that little energy will be carried those hundreds of feet out to the lake... Perhaps, given other specs. that say earth ground rods should be within 6' of each other would indicate that 6' or less is good, and 60' or longer is approaching useless for power dissipation (using a typical engineering design rule of thumb--difference of less than 2x are virtually the same; whereas differences of 10x an greater can be ignored--in this case a 10x longer wire (60+ foot) will hardly dissipate more energy than a 6' wire--again lots of SWAGing going here--but gives a few more points to research).

    I don't know--just lots of random thoughts going on here on what makes sense to my personal knowledge.

    -Bill

    Note: SWAG -> Scientific Wild Ass Guess :roll:
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dave AngeliniDave Angelini Solar Expert Posts: 4,137 ✭✭✭✭✭
    Re: Off grid grounding technique?

    Here is what I do for my customers. It is based on many years of sailing in the tropics and working for HP on an earth station for an international satellite phone system.

    1 Do all you can do to protect the system so that it can survive unattended. On the boat this included a Faraday cage for a GPS, VHF, and a 406 epirb.

    2 When attended shut down everything. Disconnect battery and all breakers off.

    3 For the ultimate protection all connections into the structure (solar, telephone, and all antennas) are disconnected by separating them for 10 feet minimum.

    Each person has to decide what level of protection they want to put into number one. Lightning is like hurricane season in that there can be no reason that things happen. It can be cheaper to deal with the damage which is what we did at HP.
    On a boat your life is way up on the list. At the Panama canal there was a case of three boats on a dock that were hit. In the middle of the three was a power boat that lost everything. All the light bulbs exploded on the power boat. On either side of the power boat were sailboats with 50 foot masts that were unharmed.

    Up in the mountains we have big trees and they can be your best friend in a storm. Just a casual look at the structure and you can almost see which trees need to go. Good Luck!
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • icarusicarus Solar Expert Posts: 5,108 ✭✭✭✭
    Re: Off grid grounding technique?

    Now you guys got me scared! I'm screwed! (LOL)

    When I leave I open all the breakers, and I should drop the antenna leads to protect the radio(s) but often don't.

    To be sure, my biggest worry is protecting the building from fire. The electronics are more easily replaced, so in order of priority , protecting me comes first, followed by, protecting the building, followed lastly by protecting the electronics.

    The reality is that we get T-storms so often, and so often out of the blue in the middle of the night with little warning, that unplugging everything every time there is a rumble is a non starter.

    Bill, I will re-read and look into what you have posted, great info by the way. I guess at this juncture I will do a really good ground to the antenna, then add diagonal grounds, look around for some good stranded wire, and (continue to) hope for the best.

    Tony
  • westbranchwestbranch Solar Expert Posts: 5,114 ✭✭✭✭
    Re: Off grid grounding technique?

    Tony, I will try to describe what we used to use in the fire lookouts here..
    all the wiring was in 3/4 ich copper wire/cable
    the lookout was about 16 foot square, in the style of a 'railroad house' where all facets of the roof met in the middle where there was a small rod.
    on the top of metal roof along each roof join was a cable heading down the ridge to the corner and then vertically to the ground.
    Remember this hut is on top of a stone mountain, granite I believe.
    there was another cable along the eaves as well as along the floor line.

    There were grounding lines starting at the eaves to ground rod about 20 feet away.

    there were also ground rods at each corner of the hut.

    Next just to make sure there would be safety for the poor soul inside the hut, the exterior wiring pattern was repeated on the inside of the walls!

    Old Ted the lookout man told me of one storm he went through that produced blue waves 'dancing' on the internal wires! I hate to think of what was going on outside.
    the inductance was so bad that he used a 12 inch stick to trip the FM radio switch for 2 days just to be sure, ....he had been 'bitten' once,..... twice shy. the radioi was a hand held lunch box in the middle of the room.

    Hope that is a good description of a 'box';)
    Eric
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
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  • nigtomdawnigtomdaw Solar Expert Posts: 705 ✭✭
    Re: Off grid grounding technique?

    Tony time for tablets, but Im also reading this thread with concerns, I have an earth nuetral bond should I remove it ?


    Nigel
  • bentherebenthere Solar Expert Posts: 109 ✭✭
    Re: Off grid grounding technique?
    icarus wrote: »
    I heard once, and have no recollection of where, the real way that lightning work is that they provide such a good path to ground that they (can) dissipate enough static energy such that a lightning strike doesn't happen. In the event that it does strike, the rods and the ground wires then can direct the strike off the to reduce or eliminate damage.

    I was once on a radio tower working as a storm rolled in. I began to hear a snapping noise from the lightning rods and in my investigation figured out that a tip was misthreaded. I removed the tip, got zapped in the process, and changed the frequency of the zapping. Not wanting to get zapped again, I touched the tip back to the rod increasing the frequency as the connection got better and closer to the top and put the tip back in place without getting bit. Realizing what was going on, I scurried down that tower faster than anything you've ever seen.

    A coworker related that story to the microwave radio repair guy. He's intelligent, works on towers all the time, and has been struck (I think once directly, and once zapped from a nearby strike). His idea of the way lightning rods work matches yours. They are to release the ions to the atmosphere that would otherwise build up and create a more likely strike.

    Interestingly, Wikipedia doesn't agree. I'll leave it to you to find a more reputable source for your research. But I'm not entirely sure that your idea is off base.
  • icarusicarus Solar Expert Posts: 5,108 ✭✭✭✭
    Re: Off grid grounding technique?

    Bill's link to the lightning safety research folks, (see his links) suggest otherwise. There seems to be no basis in fact for that conjecture. As I suggest, my concern is people first, building(s) second, electrical stuff last. If there are conflicts in details, I will err towards the first two at the expense of the third if needed.

    Much more reading to do,

    Thanks for you input,

    Tony

    PS. I am leaning toward keeping the electrical system(s) un-grounded except for the roof to panel frames,, but I may cast those loose from the Antenna/chimney wire and leave them to themselves.
  • BB.BB. Super Moderators, Administrators Posts: 28,176 admin
    Re: Off grid grounding technique?

    My understanding... Trying to bleed off energy to prevent a strike--more or less trying to prevent a flood by opening a 3/4" spigot at the base of Hover Dam.

    What the heck--try a SWAG and see what it looks like. From some basic Lightning facts:

    Say a stroke lasts about 1 milliseconds at 20,000 Amps (very large strike--but there can be larger)... And you want to bleed off the current at less than 5mAmps (below that current is human safe--guessing from "stories" in earlier post--that person did not die/cook/etc... So the current from dissipation is relatively low.

    20,000 Amps * 0.001 seconds = 20 Amp*Hours

    To dissipate the energy down below 100 amps (small strike)--basically:

    20 AH / 0.005 amps = 4,000 hours

    So, with low amperage dissipation (air is a "poor conductor" until it is ionized--then we get the 100-20,000 amp current)... We would need the dissipation to "discharge" the strike within 5 minutes. The time frame would seem to be "too long" for that to have any meaningful advantage.

    Take 20,000 amps in 1 msecond and dissipate over 5 min:

    20,000 amps * 0.001 sec / 300 seconds = 0.067 amps of current

    That sounds plausible... a 1/10 amp of current over five minutes to dissipate the strike energy... However, how do I get 1/10 (or even ) 1/100 of an amp) without ionization of the air. And if I ionize the air, I improve the conditions for attracting a strike.

    If you look at the total energy of a single large storm (from link at top):
    • Williams says a moderate thunderstorm generates several hundred megawatts of electrical power.
    • One storm can discharge enough energy to supply the entire U.S. with electricity for 20 minutes
    I don't see how any "one" small location can dissipate enough energy to protect from a good sized electrical storm.

    At best, you attract the strike to something that won't suffer economic (tree, lamp post) or to something designed to absorb the bolt (lightning rod + wiring to earth).

    -Bill :confused:
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,108 ✭✭✭✭
    Re: Off grid grounding technique?

    Bill, concede for the moment that I am over my head, but following your previous logic; If instead of bleeding off the current in 5 minutes, the mere fact that the lightning rod were bleeding off energy 24/7, or in this case 20 minutes before and 20 minutes after the "strike that doesn't happen", therefore bleeding off the energy such that the arc doesn't have to strike.

    It seems at least plausible to me. Because of the fickle nature of lightning and lightning behavior, I don't know how you can do a control, such that you can calculate the lightning strikes that don't have to happen. Perhaps this is something that "the mythbusters" can tackle. Certainly someone way smarter than me.

    Tony
  • BB.BB. Super Moderators, Administrators Posts: 28,176 admin
    Re: Off grid grounding technique?

    The storm is a massive static electricity generator...

    It is generating enough energy to do a local strike every 5 minutes (just a SWAG from my own limited experience).

    There is no "reservoir" to empty before or after the storm. Only the local storage with is filled, emptied, and refilled--every 5 minutes or so.

    Sort of like saying can use VW brakes on a 40 ton truck if I start pushing the brakes last Tuesday... Nope--the energy is here and now that needs to be addressed (from my limited understanding).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,108 ✭✭✭✭
    Re: Off grid grounding technique?

    You're missing my point (my fault, not yours!)
    If, during the storms duration, lets say for the sake of this conversation 40 minutes, is is plausible that a lightning rod could dissipate enough energy to preclude a strike?

    By the way, a lightning strike every five minutes would be quiet in our lives. I think that there have been lots of cells that the sky is lit up enough almost continually for a couple of hours,,, perhaps 30-50 bolts per minute. Not all ground strikes, in fact most aren't, but one continual roll of thunder.

    I've got some pretty cool analog pictures taken off the front of our place. Someday I will have Susan scan them and I will post some.

    Tony
  • bentherebenthere Solar Expert Posts: 109 ✭✭
    Re: Off grid grounding technique?

    Following Bills logic, I think it's even worse than he stated because we've only dealt with current and not power.

    The linked article would indicate several hundred million volts at 10000 amps for .001 seconds.

    So .001 * 10000A * 300000000V / 3600 (60 seconds * 60 minutes) = 833333 watt-hours, or 830 KWH.

    I don't know at what voltage it would bleed off the lightning rods, but it must be fairly high in order to arc. Even so, the amperage would have to be HUGE to bleed off all that power.

    Like Bill said, I'm still here, but might mention that this was one of two lightning rods within 10 feet of each other that I believe have a common ground.

    Still, you may not have to bleed off all that power, just enough that the lightning doesn't strike HERE.
  • icarusicarus Solar Expert Posts: 5,108 ✭✭✭✭
    Re: Off grid grounding technique?

    Ben,

    Perhaps this is the point "Still, you may not have to bleed off all that power, just enough that the lightning doesn't strike HERE."

    I can't calculate much less comprehend the idea of several MILLION volts at 10,000 amps! Also in my experience an average lightning strike lasts longer than .001 seconds. Now from the start of the arc until it contacts either the other cloud, or the ground may be longer, but I have no idea how long the arc "stays" on the ground.

    Oh well, more thunderstorms are predicted for the next few days.

    Tony
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Off grid grounding technique?

    Might not help no matter what you do:

    http://ca.news.yahoo.com/s/capress/090812/national/hit_by_lightning

    These poor kids were out in the middle of a wide-open soccer field. You would think that would be fairly 'safe'.

    And I have 10 acres of trees, most of them over 100' tall and about half tinder-dry dead pine. Oh boy. :cry:
  • icarusicarus Solar Expert Posts: 5,108 ✭✭✭✭
    Re: Off grid grounding technique?

    Comes under the category of "being in the wrong place at the wrong time" or "S*%*T happens!" or "When your time is up".

    You can't prevent or solve everything,

    Tony

    PS. I have to say I have been WAY to cavalier about lightning over the years. Living and working in lightning country, and being on the water a lot lead me to do some stupid stuff over the years.

    The dumbest was perhaps going out after a vicious squall, with lots of lightning around to search for a tourist fisherman who didn't get off the water as the 150km squall came bearing down on him. Looking out with the glasses after the squall passed, seeing no sign of him, I went looking fully expecting to find a boat and no boater. I found, that at the last minute he had made a run for shore and was sitting out the storm in the rain. He was more than a bit shaken. We took him in for coffee and warm clothes.

    Susan was pissed that I jumped into the boat with tons of lightning around to search for someone who was perhaps stupider than I!

    T
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Off grid grounding technique?

    tony,
    the faraday cage is to bypass that energy from you, your house, and to a degree your equipment. the antenna you have is a strong lure for lightning and even with a faraday cage it could travel down the coax to do whatever it wants to. that needs a lightning arrestor to allow much of the energy to jump to ground before the coax enters the building. there are also other ways to bleed this off more directly by using very large low resistance inductances (i don't expect you to do this) to bypass the bulk of the low frequency portions of the lightning while being too resistive to pass the upper frequiencies of your radio to ground. in addition to that bleedoff, be it with the cheap gap arrestors out there or the inductive method, you need the coax switched to ground by either a high quality switch or screwing it into a chassis connector that has a heavy wire lead from both the center pin and outer shield going to the outside ground.
    the idea is simple for like being in a car or plane when they are struck that the energy is allowed to pass around that which is inside. solid metal all around is going overboard as the sparce cage of wire will most likely suffice. you can use the #4 for this cage if you like, but the steel roof won't be good as a cage by itself. you can try to bond the upper parts of the steel roof with stainless connections to go to the copper wire lead down for the cage if you would like, but isn't necessary. do keep the copper cage leads from touching dissimilar metals directly, like your metal roof, or it will cause rust there. the top of the cage will need those needle like protrusions pointing up and can be just the #4 sticking straight up for a foot or 2 if you like and you'd need 2 of them minimally and spaced out with more of them being better.
    the antenna mount (stove pipe i believe you said) should also get bonded to the faraday cage wire, but the stove pipe may still pass the lightning energy into the house. not much you can do there.
    as to the conductivity of the lake being poor in bill's eyes i bet he wouldn't want to be in it during a storm as it is the most conductive thing around. keep in mind bill does not realy experience the lightning phenomina and is basically only kicking around ideas he sees via the net. he isn't totally off on some things either, but not enough to make me change my mind on the subject. this lake ground is by far better than putting the ground rod into a pit because the water is more conductive than that pit would ever provide even if both were of identical 8ft ground rods. if you sink it into the lake bed it would be for stability, keeping it away from boats or swimmers (anti physical hazard), and possibly for times the lake could receed some. it would be the high moisture levels (water) in the lake bed that would keep it conductive. water is only a poor conductor in comparison to most metals, but passes a lightning bolt with ease, especially with that much water. it is also better in conducting than soil or rocks and those things gain most of their conductivity when wet. if you don't believe me then do yourself a controlled experiment with the rocks, soil, and water if you have a dmm.
  • icarusicarus Solar Expert Posts: 5,108 ✭✭✭✭
    Re: Off grid grounding technique?

    Neil,

    I mostly got it, but for a bit of nuance. I still don't know how to "build" a Faraday Cage around the house. I understand the concept. Here is what I am going to do in the interim. I am going to move the vertical antenna to the opposite gable end from the metalbestos chimney. The though being that the antenna being ~20' higher and 20' horizontal away from the chimney would present a better "target", and being well grounded it should deflect the lightning away from the chimney. (hopefully) I will then cast the roof mounted Pv ground wire loose and leave them ungrounded. I suppose I might add a separate ground wire to the lake from the chimney.

    So now, what hardware do I need to get the coax from the 3 antennas to ground without disrupting their ability to transmit and receive? (1 FM omni directional vertical, 1 directional FM yagi type antenna, plus a 800 mhz Yagi for the cell phone, all sharing the same aluminum mast?

    Also, how would you suggest I build a Faraday cage? Years ago, I had a mile of copper screen wire that I got from some test lab that used it for Faraday cages! I could wrap the entire house in copper screen wire,,if I could afford it!

    Thanks for you insight and help,

    Tony
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Off grid grounding technique?

    those items you listed are they coaxial cables or twin lead? i'm guessing the 800mhz antenna is coax and can have the type of arrestor i talked of, but it may depend also on the type of connections used too. got any more info on them you can provide? it is tough to advise long distances, but i'm trying.
    this is the cheap gap type i mentioned. http://www.ba-electronics.com/a28.htm this is reusable as it has no cartridges, but this is for 50 or 75 ohm type coaxial cables like for cb or ham on hf. the cheap gap type i wouldn't trust the losses on them up on the higher frequency bands like for cellular. ice products were mentioned, but a search could provide other options and they could vary for the application to some degree and we may need to address each radio device searately .
    picture a bird cage and how the wire goes down. now make the cage rectangular like your house is and being we aren't keeping birds in the wire cage it can just be at the house corners. many will tie the sections together horizontally around the perimeter about every story or so plus the roof gutter line, but i think you can skip that too, but the top needs tied. if any more would be added it would be down the front and back following the same outside contours, but i think the 4 corners would do fine.
    normally each wire of the cage that meets the ground should meet it in a ground rod and tie them together with thick bare copper wire underground, but your homestead is rocky so picture the back wires (farthest from the lake) following the ground to meet up with the front wires which will continue along the ground and into the water to the rod. i'm still thinking that 2 wires to the lake would be good to meet in 1 ground rod. example of what i'm saying is left rear lead coming down and then sloped to the left front of the house and continuing on down to the lake with the left front wire being connected to the passing left rear. connections could be split bolts or other heavy duty connectors. the top of the roof should be intertied to the left and right sides and if you can have a copper point there in the roof center that would be good too.
    if your pvs are right there then go right ahead and put the pv frames straight to the cage wires be it connected on the house or preferably connected at the ground. always try to place the wires in a downward slope with the top interconnecting wire as the exception with no sharp turns. pretend it's electrical conduit that needs carefully bent to change directions with.
    somehow i think i'm confusing you to a point, but we can take it slow until the entire picture of what you want, need, and can do becomes clear.
  • icarusicarus Solar Expert Posts: 5,108 ✭✭✭✭
    Re: Off grid grounding technique?

    All the antenna leads are on coax. The antennas come down into an AB switch, then on to one radio. I found some links to some coax connector lightning arresters.

    Thanks for your link, I will look into these.

    As for building a cage,, I think I am going to pass on the idea. I think I will do as good a ground on the antennas and the stove pipe, do my best to lightning arrest the coax and hope for the best. We been doing it for 60 years so I guess we'll just keep at it.

    Thanks for all your help, and keep those ideas coming,

    T
  • BB.BB. Super Moderators, Administrators Posts: 28,176 admin
    Re: Off grid grounding technique?

    Well--I did have to design numerous computers, networks, telephone, etc. to withstand lightning and other discharges in the neighborhood and go through Belcore/Telcordia (phone company), UL/NRTL, FCC, and CE testing to boot... So I did have quite a bit of experience with the issue.

    However, my equipment was inside the building and (usually) after the network demark--so the carbon blocks/flash tubes were usually between my equipment and the lightning.

    I had looked many times at how to control the energy on the board to prevent damage (gas discharge, MOV's, grounded grids inside transformers, and such)--and every time it came down to a choice--the gas discharge tubes and MOV's lost out to designing a high voltage barrier between the side of the equipment subjected to surge and the balance of the system.

    I have not had to design equipment to sustain direct strikes--but I have studied the issue some in jobs past to better understand the energies my equipment would be dealing with.

    It always ends up being a mixture of solutions... Keep the lighting away, design/install something to drain the excess energy away before it gets into the home, and then inside the home/building, design the interface circuits to have 2,000+ volt barriers between the "network" and the inside world.

    Probably with DC power has always been that there can never be a barrier between the battery and where the power is used (Switching Power Supplies being the one common exception). With AC, you have electrical batteries and common mode barriers that limit the amount of energy transmitted "through" the protective devices.

    What more can I say...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 8,029 ✭✭✭✭
    Re: Off grid grounding technique?
    These poor kids were out in the middle of a wide-open soccer field. You would think that would be fairly 'safe'.

    But they were the "tallest" item around. The "rolling safety sphere" from trees and such is pretty short ranged. (60m sphere model) some talk, diagrams, and such here:
    http://www.furse.com/elp/lpov.htm
    &
    http://www.bautforum.com/science-technology/64811-lightning-protection-rolling-sphere-method.html
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  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Off grid grounding technique?

    very well tony as anything you do should help somewhat. know that the gap type arrestors will still tend to pass on some of that energy. the other types can blow out after a few or even one emp event. it is hoped that you will disconnect the coax from the radios and connect them to ground as i had gone into before. this gets it away from your equipment as radios with transistors and ics are prone to modest voltages blowing them out. static is enough for ics.
    i would still use the lake as ground.
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