Lightening & Inverters

fooddiva · August 2008

We are totally off the grid and have a Trace 4024 Inverter as part of our PV system and recently have had some lightening damage. Not a direct hit but obviously close enough to first fry the control panel and now not sure what happened. All within 2 months!! Our repair tech says they aren't making the 4024's any longer but you can still get parts. We have lightening suppressors/arrestors on both ends of the inverter, on the generator, on the water pump but I guess it doesn't matter when lightening wants to get in. After the first round this season we thought we were disconnecting everything by disconnecting the gen. switch,turning off the main AC panel, the solar array, we have wired our phone system so that all we have to do is unplug one thing and the entire house is disconnected, but it didn't matter. I'm looking for suggestions for future lightening protection. Our supplier suggested the twist and lock method on both ends of the inverter. Obviously we need to isolate that unit during a storm. Does anyone have any other suggestions on how to protect this inverter? And what do you think of the twist and lock scenario? Also are there any other inverters worth checking out that might be cheaper but yet as sturdy as the 4024? Thanks.

mike95490 · August 2008

Re: Lightening & Inverters

I'd think if you can isolate the battery bank, charge controller and inverter, from the long wires from the PV array, you should be OK. Even a "near strike" can induce, via inductive coupling (1% of a couple megavolts, induced in wires, will fry stuff) That's where I'd spend my $, to isolate the PV's DC feed from the power building. If you have long lines from a power shed to your house, those long lines will be susceptible to induced voltages too.
There are a lot of Ham Radio Operators that have extensive schemes to keep lighting damage out of their shacks.
How have your PV panels held up in near strikes? I've wondered what sort of voltage it takes to fry them?
If you are in a really "active" area, you may need to re-think the entire wiring scheme, as it may not be correctable in it's current state.
Solar Guppy is in Fl. and may have more info on what works there.

BB. · August 2008

Re: Lightening & Inverters

Do you know a HAM radio owner in your area? Working with lightning suppression is a lot like working with RF energy... Grounding, wire runs, and such can make a huge difference in how easy it is for the lightning energy to get into your system... Many HAMs are very familiar with trying to prevent lightning damage into their radios.

Search for HAM + Lightning + Grounding for many discussions/diagrams on trying survive a lightning hit.

A proper ground system (may require more than one grounding rod), making sure you don't have "loops" of wires that can act like antennas (run +/-. Hot/neutral wires right next to each other--don't let the plus lead take a different route than the negative lead, try to keep the DC solar panel wires separate from the AC and DC wires that run to your inverter/home--don't run them in parallel, have them cross at 90 degrees, etc.).

Try to avoid multiple ground rods that are attached to different parts of the system--two rods some distance apart will become different voltages (rod nearer t he strike with be at high voltage with respect to a rod far from the strike)...

A few pictures of your system/setup posted here may help.

-Bill

Solar Guppy · August 2008

Re: Lightening & Inverters

When a storm comes, I switch off all the GT's using the built in disconnects, I take the house offgrid ( flip the main ) and run the house on the batterys to the storm has passed.

My arrays float, no grounding and no connections to anything once the disconnects on the GT's are switched off. What I get from storms in a rainy season is 100 years worth of storms in Mass. Its very simple, lighting is lookng for the lowest resistance to ground, put nothing outside that offer a path to ground and those componets will never get hit. The "experts" that write the NEC code think otherwise and want not only the solar panel frames connected to a ground wire but half the PV wiring as well, very very very bad for you expensive electronics.

Also VERY importaint is not to have long computer network cables or cables that are long connected to the electronics, as Mike points out, they make excellent pickups for the emp for a lightning strike.

I have probably 20-30 hits within 1/4 mile of the house every week, very common as I'm in the highest lighting prone area in the country.

The only damage I have had is due to network cables , comm cables and once I had a hit on the street light in front of the house ( about 30 feet from the house ), street light litteral vaporized and sent all that juice into my main panel, that why I now disconnect from the grid durring these storms

Since then, lots of hits around me but no damage

niel · August 2008

Re: Lightening & Inverters

if you do have multiple ground rods then tie them together with at least a run of bare #6 copper wire underground. this will make the potentials between the rods nearly disappear and help to make it all one large ground rod. we have had many discussions here on the forum too concerning grounds and lightning so search this forum first. the problem is if lightning wants to, it will, and there are ways of lessening the chances. a switch turned off even in sg's case won't help him if it jumps the switch, but that open switch does help by making the path not as appealing due to added resistances of the air. let's face it it jumped how far through the air already so it can jump switches in some cases where the emp is high enough or where a direct strike has occured.

in sg's case turning off his connections to the outside world during storms will minimize the chances and he just included grounds as part of that disconnection. know that odds are that few inspectors will allow you to not have a ground so when attached to one it better be right or it can be worse than none at all. i know you did take precautions (except disconnecting the ground) and it got you anyway, but if you read through the past posts and then come back to here with any questions or ideas you may wish to run past us with more input on how your setup is and what it consists of, maybe we can avert another incidence in the future.
edit to add:
as to the, "i don't know what happened now", long after the emp did some damage, it's all the same damage, but some parts take a bit of time to fail all of the way. sometimes a smaller emp from another passing storm is enough to pop the weakened parts that were still functioning though damaged and weakened from the first incident.

System2 · October 2008

Re: Lightening & Inverters

Solar Guppy wrote: »

When a storm comes, I switch off all the GT's using the built in disconnects, I take the house offgrid ( flip the main ) and run the house on the batterys to the storm has passed.

My arrays float, no grounding and no connections to anything once the disconnects on the GT's are switched off. What I get from storms in a rainy season is 100 years worth of storms in Mass. Its very simple, lighting is lookng for the lowest resistance to ground, put nothing outside that offer a path to ground and those componets will never get hit. The "experts" that write the NEC code think otherwise and want not only the solar panel frames connected to a ground wire but half the PV wiring as well, very very very bad for you expensive electronics.

Also VERY importaint is not to have long computer network cables or cables that are long connected to the electronics, as Mike points out, they make excellent pickups for the emp for a lightning strike.

I have probably 20-30 hits within 1/4 mile of the house every week, very common as I'm in the highest lighting prone area in the country.

The only damage I have had is due to network cables , comm cables and once I had a hit on the street light in front of the house ( about 30 feet from the house ), street light litteral vaporized and sent all that juice into my main panel, that why I now disconnect from the grid durring these storms

Since then, lots of hits around me but no damage

Wow, what to do?

I'm putting up the system this weekend. I've thought about this grounding issue and it has caused great consternation. Reading back through various "grounding" threads I see a constant:

SG lives in a high lightning area. SG unplugs everything (including ground) from the outside when lightning storms happen. I tend to think that makes sense. Especially when it seems some folks don't do so, and then seem to get everything fried. My cabin is in a very high lightning area during monsoons. I am tending toward the SG approach to grounding. It seems there are 2 purposes in grounding. 1) to keep someone from getting fried during a fault and 2) keeping my system from getting fried during a lightning storm. Since my system is low volt and low amp, I'm less concerned about # 1.But #2 is highly likely. I'm thinking that what i may do is put a fuse on both the + and - input at the PV disco. Then if a strike occurs at the array, it will blow both fuses and keep the strike out of my equipment. Thoughts?

Finally, SG, do you ground anything (arrays, inside equipment, batteries, boxes, etc.)? If so, how do you keep the inside grounded equipment (with an outside rod) safe from a strike during a storm?

Thanks.

niel · October 2008

Re: Lightening & Inverters

fuses will not stop lightning even when they're blown for it will jump across them just like i said for the switches and it only needs a potential of about 1000v/inch to do so. this is a piece of cake for lightning that has already travelled miles through the air to get there and it won't stop until it's destinated.

there may be another option for you and that might be to setup a lightning rod some distance away from your place that would attract the lightning to it instead. there's no getting around it though because the lightning will set off a strong emp that will reach your stuff. a good ground imho is the best option and having it like a shield or cage (faraday) is the best way to achieve that going into ground rods for each leg of the cage that are intertied underground. use lightning protection devices too, but keep them somewhat physically isolated because they can explode under a strong enough condition like a full strike. between the distant lightning rod (must be significantly higher than your pvs) and a faraday cage i'd say you're pretty well covered, but still no guarantees. i'd take this option over just having no ground anyday and i use a faraday cage at my place.

Mangas · October 2008

Re: Lightening & Inverters

This subject concerned me a lot too when I built my system. I was about to install lightening rods but was strongly advised not do it.

We spent a lot of time grounding the array, solar mechanicals and house.

mike95490 · October 2008

Re: Lightening & Inverters

Mangas wrote: »

This subject concerned me a lot too when I built my system. I was about to install lightening rods but was strongly advised not do it.

I'm looking////// planning a flagpole down the driveway, and use it as a lighting rod. Maybe set something on high ground, near the house, but not next to it. I'm of the school of "Attract it away from the house, not to the house". (but not so far away, it's ineffective)

Mangas · October 2008

Re: Lightening & Inverters

Hi Mike. Good compromise. Sounds like that flag pole of yours must have few "close encounter" battles scars.

While I'm surrounded by desert mountains (multiple peaks), I also have a lot of tall mescal agaves sporting flower spikes rising up to 25 feet. When lightning hits those babies it sure lites up the country! I've put out a few agave strikes close to the house, say 400 feet away.

Between the mountains and the attractive flora, I try to keep a very low profile. Electrical guys told me don't compete! Nonetheless, I get pretty edgy when the summer rain storms move in.

niel · October 2008

Re: Lightening & Inverters

"Between the mountains and the attractive flora, I try to keep a very low profile. Electrical guys told me don't compete!"

maybe i've got this one all wrong as i don't know what the mescal agave looks like, but maybe pick one of those agaves about 200-300ft distance from you and run a heavy copper wire from the top of it, or at least high up on it, and down into a ground rod. it doesn't need to conform to nec so you pick the wire size and ground rod length. if you have an old piece of copper pipe then use it for the ground rod and use a stainless steel type hose clamp to attach the wire. nature will conceal it all.
this won't mean you don't need to do something with your pvs ground as you still have to do that and by the book.

Mangas · October 2008

Re: Lightening & Inverters

Niel, our native agaves have a dangerous tight cluster of 4'-6' upright long, very sharp leaves, each adorned with poisionous spike on the end surrounding a 25'+ tall flower stalk (blooms only once and plant dies). Tapered flower stalk can range up to over a foot in diameter at base.

Technically creative, but no way safely to get close to the stalk to run a wire. That is, unless you're very brave. Anything closer than say 300', I cut (carefully) the flower stalk down with a pole cutter.

Electricians tell me the system is as grounded as it gets. We'll see. I did build a steel T-Post/Rabbit Fence around the array to catch high wind debri which has caught several potentially damaging flying objects (like plastic chairs). I wonder if that improves or counteracts what grounding measures we've taken? The galvanized fence perimeter is only 10 feet from the array's panels.

Good topic and one which concerns me a lot.

niel · October 2008

Re: Lightening & Inverters

it might not be a bad idea to try and ground the fence too, but a proper grounding for the fence would be very elaborate and maybe just a few of the posts with a ground rod and an underground connection to your pv ground rod. all posts should ideally be tied to ground and with straps connecting all other parts of the fence, but i know it'd be too much trouble, especially for a fence.

Mangas · October 2008

Re: Lightening & Inverters

Niel, you make a good point.

The fence is tied together (posts to panels with galvanzied wire) so, I think your idea of grounding it to the array grounding rod makes sense. If the wire rabbit fence panels (lattice 1/4" x 6"x 6" steel squares) are wired to the posts do you think I'd still need to strap the posts (set about 10' apart)?

The electricians are here in a couple of weeks and I ask them what they think too. When we built the system the fence wasn't up.

mike95490 · October 2008

Re: Lightening & Inverters

Re: Tpost/rabbit fence:
I'd ground the fence separately from the array's ground. I'd drive at least 3 - 6 equidistant grounds for the fence. My idea would to be to keep the Lighting strike away from the array.

So the array is not on your roof - am I right ? How does power get from the array to the house, DC, AC, above ground pole, underground conduit ? That route needs protection, and if you have a way to disconnect it from the house in a BAD storm (without getting outside, feet wet and grabbing a metal handle), I'd look into it.

With the way lighting "splashes around", I'd consider that any near strike would have a good chance of "frying" stuff, unless elaborate precautions are taken. A direct hit, assume it's all toasted.

Agave/Century plant photos:
http://en.wikipedia.org/wiki/Agaves#Images_of_species_and_cultivars

niel · October 2008

Re: Lightening & Inverters

the electrician will give you a strange look as fences aren't considered part of an electrical system and aren't really necessary to be grounded. in light of the proximity to the array and being able to expand upon your ground system gives a larger and better common ground point and better able to discharge lightning. what mike said about luring the lightning away just isn't so when it's that close to and below the array. as i said to properly do it would be too involved so just pick a few of the posts if you like and ground them. this is totally optional just to be clear. if you do it make sure you properly attach dissimilar metals to avoid galvanic reactions.

mike95490 · October 2008

Re: Lightening & Inverters

Of course, the distance from fence to array, array hight, fence pole heights will influence what sort of protection you get. (you could add a couple tall rods on your fence line)

I subscribe to the "rolling sphere protection" model, where an imaginary 60 meter sphere is used as a guide to determine where/what is protected.
http://www.ptsa.co.kr/image/ifimmg4.jpg

And NEC wants all safety earth/neutral stuff bonded together, but that is for household current only. If you are trying to ground lighting, you need much beefer grounds than for household. If tied together, you need to have ALL grounds lighting pulse capable. A 6 ga wire will not likely survive a full strike, but it's plasma will help direct the strike into where ever it was heading toward.

Lighting protection is tricky. Solar Guppy has a system that seems to work well for him.

Mangas · October 2008

Re: Lightening & Inverters

Thanks Mike and Niel.

The array is located 150' away from a solid rock and morter constructed solar mechanical room (metal roof) dedicated to housing the inverters, charge controllers and batteries. The array's underground DC lines are buried (crusher fines shaded) in electrical conduits. The solar house is located 100' from the ranch house with AC lines buried in electrical conduits.

5 1/2' of T-Post fence are showing above ground which are tall enough to attract a strike. Based on your comments, I think I'll ground each corner to dedicated equidistant grounding rods.

Niel, what do you mean by "...make sure you properly attach dissimilar metals to avoid galvanic reactions? By that you mean not to have metal between the posts and the grounding wires? I need to read Mike's link too.

Yes, I have DC array main disconnects at the array field as well as in the solar mechanical room.

I believe the electrician told me he spent many years grounding industrial plants, so this will a good question for him. He also designed and turnkey built the photovoltaic system as well as wiring the house, genny, etc. I have a lot of confiedence in their work.

Yes, that's an agave but a small one.

mike95490 · October 2008

Re: Lightening & Inverters

Wow ! now that I see the size of the array, vs it's corral, the fence is too close/low to be a useful diversion.

What does come to mind, is the elevated road you appear to have shot the photo from. A pair of flagpoles on that high ground would be a great diversion rod. There are also thoughts about a protection grid or wire, high above the array, so the wire would intercept any strikes, sparing the array below it. I don't know if you have any telephone poles or whatever.
The wikipedia page has some thoughts too, http://en.wikipedia.org/wiki/Lightning
also there is a Yahoo Group :
LightningProtection · Lightning Safety & Power Quality Issues
http://tech.groups.yahoo.com/group/LightningProtection/ that has some learned discussion for some in depth theorys. Just don't pay $ for a "porcupine" protection device.

niel · October 2008

Re: Lightening & Inverters

mangas,
what i meant was that in making proper connections that they have to be of the same metals or galvanic reactions can occur. aluminum to aluminum and copper to copper. when intermixing these one needs to take steps to ensure the proper connection and that over time it won't diminish due to corrosion. that's where stainless steel comes in as it doesn't seem to bother other metals much and acts well as the go between for some of them.
in seeing your setup i agree to ground the corners of the fencing and into a ground rod, but also tie it to the pv ground via bare heavy gauge copper wire underground. seperate grounds not intertied will have different voltage potentials develope and could cause problems without lightning being present and with lightning if hitting the fencing it will induce greatly into the pv system so the grounds should be one large groundind system. rather than run heavy bare copper wire under ground from post to post have those go underground to the single ground point for the pv system as in an x fashion.
ps now that i know what the plants look like i can see why they get hit.

Mangas · October 2008

Re: Lightening & Inverters

Got it guys and thanks very much for the plan. Learned a lot about this tricky subject which I believe many people don't fully understand.

Answering Mike's question, I have a mircowave phone which sends and receives its signal to the nearest telephone pole with a mounted receiver over 10 miles away. By the way this neat technology does away with the need for expensive telephone poles. The little receiver the size of a shoe box sits inocuosly on the side of the ranch house and gives us two phone and a data line.

RCinFLA · October 2008

Re: Lightening & Inverters

One of the weakest link in the SW series is the sense transformers which monitor the AC voltage. These are three small transformers that convert 120vac to about 13.8 vac which is actually what is measured by the control board. One is for Inverter, one for AC1, and one for AC2 measurement. I put surge protector disks on back side of PCB under the sense transformers.

Any time lightning hits in the close area (several hundred feet radius) there is a voltage gradient across the ground due to the resistivity of the soil. One thing to avoid is multiple grounding rods with significant spacing. A single point ground is usually best to avoid the gradient issue.

You can not avoid a jump to a line going out to a remote location, only try to protect it with ground wire running from common ground rod out to remote location.

niel · October 2008

Re: Lightening & Inverters

hi rc,
i'll clarify that i speced multiple ground rods for each corner of the fencing and each ground rod is tied directly via large sized bare copper wire buried underground and attached to the pv ground in an x fashion with the pv ground at the x apex. this makes for one large ground and is perfectly fine. no jumps will occur as they are all intertied.

Lightening & Inverters

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Lightening &amp; Inverters

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Lightening & Inverters