Grounding RV with 30' high wind genny for lightning?

frankson

I've got a large mil truck with tilt-up 30' high wind genny and solar panels atop.

I understand the need for proper equip grounding for shorts and all, but just for
lightning concerns alone, might I be better off just disconnecting everything for
the duration of the storm, including pulling up metal stairs that go to ground,
and relying upon my big rubber tires to insulate and isolate being an attractive
lightning to ground path?

BB.

Re: Grounding RV with 30' high wind genny for lightning?

6" of rubber is nothing to a mile or more of travel of a lightning bolt through the air.

If the truck is unattended, then grounding may not matter much.

If the system is providing power and/or occupied, then grounding is probably very important. All that metal can attract static charges even on a clear day--So grounding can be helpful too.

-Bill

frankson

Re: Grounding RV with 30' high wind genny for lightning?

BB. wrote: »

6" of rubber is nothing to a mile or more of travel of a lightning bolt through the air.

Bill, yes, I understand that, and if it got hit I'd want it very well grounded as robustly and directly as possible.

What I'm inquiring about here is if the lightning is more or less attracted to strike the truck and it's panels and
30' high wind genny pole, in the first place, if they are all not grounded? Another way to ask it; are very well
grounded potential targets more apt to be hit, or less?

BB.

Re: Grounding RV with 30' high wind genny for lightning?

There is a theory that if you have your tower/mast/array "floating", they will be at a lower potential (i.e., they will float to the average voltage above the ground) and less attractive to lightning.

However, will that supply "reliable" protection... I am not sure.

Commercial Jet aircraft (some factoid I read somewhere--don't know if it is true) are struck by lightning, in flight, an average of once per year. An airplane is, more or less, at the potential of the local atmosphere (they have static discharge wicks to help this)--So that appears to not be enough to prevent lightning strikes.

So, your other option is to put up a lightning rod and make it "more attractive" to lightning, and properly ground that--So that you avoid energy flow through other, less desirable, paths.

But with a wind turbine--That is going to be difficult to easily mount a lightning electrode well above the turbine. And, from what I have read, wind turbines are hit often, and damaged often, by direct strikes.

Perhaps somebody here with more experience than I (I have "none"), can address the whole issue of wind turbines and lightning control.

If you are often (or forced) to setup your system in lightning prone areas--Then you should probably look at lightning alarms (google search). If nothing else, as a warning to keep well clear of the setup when lightning is in the area and/or you have high electric field potentials (normally, ~100 to 300 volts per meter atmospheric field strength; can be way over 1,000 volts per meter when there are thunderstorms overhead).

In the end, people safety first; equipment safety second; function during storms--you have to decide the risk/reward from there. In any case, while your truck is a natural attractor--Get 50' away and anything else will be too (structures, people, landscaping, etc.).

-Bill

frankson

Re: Grounding RV with 30' high wind genny for lightning?

One sailboat technique is to connect grounding wires at bottom of mast support cables on deck edge into the water,
so that a strike on mast might pass down them into water and, hopefully, not all fully down mast and through boat.

That might be something to consider with wind genny pole, having multiple pole support cables staked into the ground
around truck, rather than only attached to the truck top. Those higher cables might give some protection to PV panels
atop truck and electronics in truck, if it'd attract and direct more of the strike out to ground, especially if the truck was
not otherwise grounded.

I don't really know, lightning is pretty mysterious stuff. A little off topic, but sailing friend of mine who has traversed the
bermuda triangle area a lot says he has his own theory for the ship and plane disappearances reported there. He claims
he's seen lightning out there that was as thick across as a bus is long. He thinks that's what's claimed some victims there.

Jigme Urgyen

Re: Grounding RV with 30' high wind genny for lightning?

Hi. i have done this exact thing BB is talking about. If you put something up in the air the lightning will be attracted to it. doesn't matter floating or not. So your wind turbine is attractive regardless. Your panels would be less attractive because im assuming they are closer to the ground? If you have other items higher than your wind turbine, it will lessen the likely hood that the turbine will get a direct strike.

The only way to really look into this is to have an analysis done of the site, which takes into account the elevation, altitude, weather patterns, number of recorded strikes etc. Many companies offer lightning protection equipment will do this for free for you. I have used LPI australia (www.lpi.com.au) both in australia and in nepal and india. they are very helpful.

Putting a direct strike terminal up is the best way to reduce the likelihood of the turbine getting the direct strike. Your budget will dictate the air terminal protection. For example, a larger expensive air terminal will cost a couple of thousand dollars, mounted at least 5 meters higher than anything else and somewhere cental, it will give a radius of 30 meters level 1 protection, 50 meters level 2 protection, and 100 meters level 3 protection for example. A smaller, but similar quality terminal will give you the same levels of protection with smaller radius.

Putting a big air terminal up centrally like in this example, would certainly reduce the risks significantly. A large single centrally mounted unit could possible cover your entire site and protect everything.

I would still put surge arrestors on all your equipment for the static build up problem. Charge controller will get axed from statis build up, i always use a surge arrestor in the combiner and another one in the charge controller, everything bonded to the same ground.

All of what I have explained I have done a lot in places like the nepal and Indian Himalaya's in category 1 zones where the lightning strikes are the top of the scale. I know it works.

niel

Re: Grounding RV with 30' high wind genny for lightning?

no matter what you do lightning is a possibility. putting metal in the air does increase the chances of a hit. in the case of a car or plane getting hit, the outer metal shells act like a faraday cage and keep the lightning away from things and people in the interior. with wires running into the truck from the turbine and pvs, this could negate the effectiveness of such a cage that the truck itself could present. the idea of the pole guy wires going to the ground and acting like a faraday cage is good except that the cage would need to start above the turbine to be fully effective. if the nacelle is metal and at ground potential this could make your idea of using the guys to shield everything within a good one. the more guy wires the better to increase the effectiveness of the faraday cage, but 4 i think would be minimum.

one note here would be the fact that most guy wires are small gauge steel which could present a poor connection to ground. you may be able to get copper coated steel wire that many hams use for antennas and use that for guys, but i'm not sure of the tensile strength of the wire compared to the regular guy wires.

BB.

Re: Grounding RV with 30' high wind genny for lightning?

Driving a ground rod partially into the ground for a temporary installation will help with static discharge (so people don't get shocked when touching the truck body--assuming some level of soil conductivity).

But, I would also consider using flat plates of heavy gage sheet metal (copper if you are made of big bucks--here is an interesting looking temporary copper plate setup) either buried slightly under ground, or even lying on the surface. The large surface area of the plate will probably conduct a lightning strike to the ground better than a foot or two of ground rod.

http://www.kuefler-lightning.com/series700-ground-rods.htm

[h=2]Ground Plate[/h] Copper Grounding Plate made from 20 AWG thick high conductivity copper sheet.



12" wide by 24" long
(2 Square Feet)
LPC750 two cable attachments
LPC753 single cable attachment
18" wide by 18" long
(2-1/3 Square Feet)
LPC751 two cable attachments
LPC754 single cable attachment
36" wide by 36" long
(9 Square Feet)
LPC752 two cable attachments
LPC755 single cable attachment

Here are a couple of nice PDF's that show some practical off-the-shelf hardware for lightning control (note: these links are biased towards HAM radio setups--but the information is still useful):

Selecting and Installing Lightning Protection Devices (1.37M pdf)

Lightning Protection Tech Articles

An informative 3 part article on lighting protection published in ARRL's QST Magazine
Lightning Protection for the Amateur Station
by Ron Block, KB2UYT
Part 1
Lightning protection can be a serious issue for amateurs. In part one, the author leads us through the process of developing a protection plan.

Part 2
In part two the author discusses the characteristics of lightning and the hazard it presents to the amateur, and presents a method of preparing a schematic of a protection plan. This installment also shows us how to design a protective installation and what type of protection is needed.
Part 3
In part three the author shows how to develop a
good external ground system to complete your station’s protection.

Reprinted with permission from QST; Copyright ARRL

Additional Lighting Protection Articles from Polyphaser

An overview of Lightning Protection for Ham Radio Stations
Lightning Protection Tech Articles

I think all of the links are still good--But the couple I have tried are loading really slowly on my cell phone modem setup--So if it take 5+ minutes--they still may successfully load.