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A disastrous lightning strike.
By seanchan00, Section Controls Posted on Thu Aug 09, 2007 at 12:47:57 AM MST
How do I protect my system better ?

Hi Guys,
My wing generator was hit by a bolt lightning a week ago and my wind generator and the devices attached to the batteries has been knocked out for six. The wind gen is installed with a lightning rod and the base of the tower is grounded. How the surge could go through the batteries and shot out the devices is beyond me and I am here for seriouly needed advice.
You can see my wind gen system here :
http://www.fieldlines.com/story/2006/2/26/21156/5171
The lightning rod is seen in Picture 2 and it is made from iron alloy coated by copper coloured coating.
Picture 8 shows the base of the tower and the 1 inch strip of thick real copper tape 3mm thick can be seen bolted to the base. This has been connected to an iron rod driven 6 feet into the soil. all the guy wires too are connected to iron rods driven into the ground. I was wrongly quite confident that any direct strikes will be dissipated by this system since the tower is all metal and it should conduct well.
From the stator of the generator runs 3 wires to my control shed where the AC is rectified to DC. The positive output from the rectifier pass a 60 amp fuse before the power reaches the batteries to charge them. I have three batteries in two different locations in the farm and each battery has a schottkys diode to allow charge to come in but not reverse. To the batteries I connect my gadgets. 1 battery runs a Car audio disc player where the power amplifier is completely toasted. This has been replaced. This battery is protected from overcharge by a shunt regulator which has been shorted and I hope to repair it. I have just completed another shunt regulator with a much simplier design and I am replacing it. This was thankfully sent to me by Glen Hurd more than 2 weeks ago. This is a real life saver.
Next to the audio set sits my electric fence energiser and this is powered by another battery used to start my engine driving a water pump. This has beed shorted and possibly salvagable. Waiting for the parts to arrive. A 2N2222A and a 2N3055.
In the other location the batteries are used to power a 10 watt light. This is controlled by a light sensor which switches on the light when darkness falls and turn it off at daylight. This relay is not working and I have not opened it to see if it can be repaired. I paid one of the local green energy company a ridiculous price of 125 ringgit USD 35/= for this simple sensor and relay control. They sell solar panels.
Somehow enough power came through the the wires to toast the schotkys rectifier, blow the 60 amp fuse and hit the batteries and all devices connected to them.
I am hoping to maybe add a surge trip control somewhere to trip the connections to add protection. Not sure where. I am also thinking whether installing additional fuses at the user end may further protect against damage. Example, the audio player uses only 3 to 4 amp max and if I put a 5 amp fuse on the positive wire to the player this will blow and protect the amplifier. The shunt regulator uses only a fraction of an amp and a 0.5 amp fuse at the positive power line may help. I was told by the local chap I need to put fuse to both the positive and negative line from the battery to have any protection if at all it helps.
Looking back the audio power amplifier was wrongly sitting on metal inside a fully iron locked cabinet cemented into the concrete to prevent theft. I shall install the new amp on an insulator board to isolate this. The radio-repair guy said the whole circuit has been toasted because the lightning came thorugh the metal casing of the amp even after the fuse of the amp has blowned. One puzzle, my electric fence energiser is not connected to the wind generater and it still was hit. I think my farm was hit more than once and one of them must have hit the electric fence. The negative pole of the energiser is connected to the ground wire of the electric fence and the wire from that source to the energiser shows burnt mark. I should have grounded this negative rail separatly.
So Guys, what do I do now before I go on line with the wind generator and before the next lightning strike? Please help.
SeanChan from Malaysia.

A disastrous lightning strike. | 13 comments (13 topical)

Re: A disastrous lightning strike. (3.00 / 0) (#1)
by jmk on Wed Aug 08, 2007 at 08:23:21 PM MST

I sorry to hear of your misfortune. After hearing about other peoples problems with lightening I decided to make my run wires and ground so they unplug from the house. This way if we have a big thunder storm I can unplug my battery and controls from the tower. It's the one time I don't unplug it that it will probably get hit!
jmk

Re: A disastrous lightning strike. (3.00 / 0) (#2)
by EMF on Wed Aug 08, 2007 at 08:26:35 PM MST

With a few 1000 amps flowing throught your tower just think of the magnetic pulse field it could generate and the results on nearby wireing. I'd be looking at overvoltage protection on your 3 wires before the rectifier. Maybe 3 spark gaps with a serious earth stake.

Long cable runs are also likly to generate serious voltages in the event of a nearby strike.

Your pictures look great.

Re: A disastrous lightning strike. (3.00 / 0) (#5)
by seanchan00 on Wed Aug 08, 2007 at 11:25:01 PM MST

Thanks EMF,

Can you please elaborate on overvoltage protection on my 3 AC wires esp 3 spark gaps with a serious earth stake?

Sean.

[ Parent ]

Re: A disastrous lightning strike. (3.00 / 0) (#7)
by richhagen on Thu Aug 09, 2007 at 12:06:06 AM MST

A friend of mine had an oak tree struck by lightning near her house. The near strike caused significant damage, apparently from voltages induced in nearby conductors, even though it did not appear to strike anything directly. Rich
'A Joule saved is a Joule made'
[ Parent ]

Re: A disastrous lightning strike. (3.00 / 0) (#3)
by stephent on Wed Aug 08, 2007 at 08:47:27 PM MST

SeanChan.
It's going to be hard to keep a genny/tower safe from lightening...very hard.
That copper strap going to a ground rod....put it under ground several inches--metric maybe 1/2 metre or so.
Put in several more, like maybe 3 more and bury them too.
It's the total ground dissipation that allowed the lightening voltage to jump and connect to everything that was connected to the tower.
Ground dissipation is poor at best. You need that strap under the ground going to a rod--several more buried wouldn't hurt.

Keeping the ground area under the tower wet or damp wouldn't hurt..
The copper straps are one of the best conductors for lightening and having them underground makes them conduct the volts/amps all over their length to the ground.
You need more rods and straps to get rid of the lightening over a larger area.

Deeper driven rods work good too--8 foot are good--10 foot is better.
and bond all the rods together with copper straps or the largest BARE wire you can find--buried at least a foot down if possible--more is always better.
Large metal plates of 2' x 2' size (thickness of at least 1/8th" or so) buried and all tied together will help.

Using the same copper strips from each of the guy wire ground rods buried down--maybe at least 2 or 3 of them 10' (3m or so) can assist the tower straps.

You need to have "more" conductive stuff exposed to the ground over a much larger area to dissipate the lightening--putting it simply.....and there's no such thing as "too much", except in the wallet catagory, unfortunately.

Even having a 1/10th ohm grounding system will allow a large voltage buildup when lightening strikes....it's hard to get that.

The reason the voltage went everywhere was because simply the ground rods/straps (and ground/dirt exposed to them) couldn't dissipate all the currant quick enough...

Re: A disastrous lightning strike. (3.00 / 0) (#4)
by MaryAlana on Wed Aug 08, 2007 at 10:33:32 PM MST

Couple of things that might help. The copper strap to the ground rod should be brazed and not clamped. from the picture I see a copper strap running along the ground. If that is the ground strap it should be shortened and the ground rod should be right at the base of the tower. A long strap like that can act as an inductor to a lightning hit.

Re: A disastrous lightning strike. (3.00 / 0) (#6)
by ghurd on Wed Aug 08, 2007 at 11:38:25 PM MST

We are all very sorry to hear this news.

I don't believe a fuse helps much.
Lightning traveling a kilometer through the air is not likely to be deterred by 5cm of a blown fuse.
I am told, by people more knowledgeable than myself, that a spark gap is very effective. Multiple spark gaps for each conductor may also help.

Is the wind gen OK?
Does the ground strap and rod show any signs of a hit?

The information about how the batteries charge is interesting. I did not remember that.

The `kit' can be modified for use as a daylight sensor and light control circuit, with the addition of a few common parts.

Please inform me if I have anything that could assist you in repairs.
G-

Ghurd.info

Re: A disastrous lightning strike. (3.00 / 0) (#9)
by seanchan00 on Thu Aug 09, 2007 at 06:27:35 PM MST

Hi Glen,

The wind gen is ok back charging and I need to shut it down by shorting it out before the batteries get boiled out. Can you explain spark gaps and how to use it on my three incoming AC wires from the wind gen?

Your kit sounds very interesting to modify for use as a daylight sensor and light control circuit. I would appreciate very much for details as It will be so much cheaper to go this way rather than order one after each lightning strike even thouh it struck after almost three years running.

After reading all the responses, I think I will run the wires to the batteries undergroung at least 6 inches or better 1 foot under and try to keep part of this run wet. I will add grounding cables and rods but there is no way I can get exothermic welds here. The best locally is normal stick weld for metal.

Thanks a lot for all the answers guys. Phil B, your input is very comprehensive. I need a long while to read the material you sent.

Sean.

[ Parent ]

Re: A disastrous lightning strike. (3.00 / 0) (#11)
by MaryAlana on Thu Aug 09, 2007 at 10:16:00 PM MST

I do believe the hot shot exothermic weld kits are available from hardware stores as a special order. Haven't looked to see if they are available online.

[ Parent ]

Re: A disastrous lightning strike. (3.00 / 0) (#12)
by kell on Sat Aug 11, 2007 at 02:13:53 PM MST

There's an exothermic welding supplier in Thailand
http://www.exothermicweld.com/

[ Parent ]

Re: A disastrous lightning strike. (3.00 / 0) (#8)
by phil b on Thu Aug 09, 2007 at 06:39:11 AM MST

I am also sorry for your misfortune.
This has been a continious problem at work for me as well.

This may help:
http://www.nrel.gov/docs/fy02osti/31115.pdf

I got some of the best information from
http://www.eng-tips.com/viewthread.cfm?qid=121295&page=1

I have copied and pasted the best part here. Lightning.txt should also be in my files on this board. I can't seem to get it to post this morning, so it's also here:

Let me start by saying that I'm not a P.E., however, I've spent years in substation construction, maintenance, and operation so the subject of lightning is one that concerns me almost daily. Although I'm sure there are many devices and practices that people will recommend throughout the world, there is only one "fix" that I truly believe is a big help and is as close to a "true" remedy for dispersion of energy from a lightning strike as you can get. That remedy would be properly sized and carefully installed grounding. Whether your transmission structures are steel or wood, a properly sized static or sheild wire that is connected to earth at every structure with a large enough copper conductor is the answer. Of course, once that copper conductor gets to earth level, there is work to do there as well. If you know you are in a lightning prone area, provide adequate earth contact by properly installing ground rod(s) (more than one in your case would probably be a very good idea) and making sure they are connected with connections that are specifically rated for direct earth bury service. To me, mechanical connectors are not to be used in this instance. It amazes me yet today that there are companies with lightning prone lines(and substations for that matter) who haven't yet discovered exothermic welds for making grounding connections! At my current place of employ, grounding practice has changed recently. Transmission line and substation structures are now solidly grounded using large(1/0 to 4/0) copper conductors. Ground rods are installed liberally and spaced several feet apart and are connected using exothermic welds. The results speak for themselves. Few if any flashovers to 13KV underbuild conductors have occured and the breaker operations during storms (in my estimation) have been cut by at least 75%. On wood pole structures, #4 solid copper wire is the MINIMUM conductor size(many times #2 awg and 1/0 is used) and in addition to a butt rap at the bottom of the pole, at least 1 ground rod (5/8 in. X 10ft.) is installed 4 to 6 ft. away from the installed pole butt into undisturbed earth. When grounding steel towers or any steel fixture that is subject to lighning strikes, carry the grounding conductor all the way to the top of that structure and attach directly to your shield wire. Don't allow "coils" or "pigtails" to be installed in the slack area near the shield conductor in these conductors either. Keep them as straight as possible and keep bends in the grounding conductor gentle and sweeping. Sharp or abrupt bends or kinks should not be tolerated. This "new practice" may ruffle the feathers of some linemen, but when they witness the results, the complaining should stop. Don't rely on the steel structure itself to carry the energy of a strike. Bonding the base of the steel using a 5/8in. X8ft. ground rod and a short piece of #6 copper is NOT proper grounding.(At least here in the middle of the U.S.) Now, grounding is not cheap by any person's estimate, but it sounds like you've had enough damage and destruction to warrant some expenditure on problem prevention. It has been my experience that grounding is without a doubt the most misunderstood subject at many utilities today. It seems the folks who make the decisions are always looking to cut expenses somewhere,(aren't we all?)but cutting the grounding is probably the LAST place where cost cutting should take place. I'd forget the splined balls and get some large copper conductor and some 3/4in. X 10ft. ground rods.

Re: A disastrous lightning strike. (3.00 / 0) (#10)
by JW on Thu Aug 09, 2007 at 06:43:03 PM MST

Hi All,

This might be useful.

"Knock on wood... but I've had no problems since I started unhooking the AC side of my inverter in storms. Perhaps time will tell!"

http://www.fieldlines.com/story/2003/9/19/82225/2621

JW

[ Parent ]

Re: A disastrous lightning strike. (3.00 / 0) (#13)
by scottsAI on Sun Aug 12, 2007 at 08:18:22 PM MST

Hello seanchan00,

Check out:
http://www.fieldlines.com/comments/2007/5/8/21473/65854/16#16

Hope you recover quickly and good luck on the rebuild.
Have fun,
Scott.

A disastrous lightning strike. | 13 comments (13 topical)

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