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Lightning and Solar Panels


Delta9
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Hi Forum,

How big is the risk of a lightning strike to a solar panel array? How do you mitigate against it? People on the Highveld must have considered this when putting up an array given the amount of lightning that goes on there. 

If the panels take a hit what sort of damage will occur? Will this surge of energy go through the whole system and take out inverters and even worse, electrical appliances connected to the inverter?

Would a DC coupled system be safer in this respect as the surge would have to go through a battery bank before it can hit the inverter. Will a large electrical surge such as that from a lightning strike get through a large DC battery bank to the inverter?

Would it make sense to have DC fuses in the line that can be opened and the fuse taken out so that as you see a storm approach you can disable the solar system and in effect physically decouple it from the batteries/inverter system/s?

Another possibility comes to mind. In the rainy season when we have storms just about every afternoon/evening, it may make sense to remove the fuses from the solar panels to the rest of the system every afternoon when the sun is gone so that if a storm comes up through the night and you take a strike, the energy cant get through the cables to the Charge controller/batteries/inverter.

 

Case in point. Last night about 9.00PM we had a HUGE storm roll through quite quickly. it started raining softly at first then the heavens opened up! There were a few flashes of lightning here and there and thunder quite loud . I took the precaution of turning off the satellite modem. Next thing there was a brilliant flash of light that lit up the lounge room and a GOD almighty CRACK the same instant. I heard a loud clicking noise come through the satellite modem but it was powered off. However the ethernet cable from the modem to the router was connected, and even though the satellite modem was turned off the router's WAN port got fried.

That got me thinking about what would of happened had I had a solar array on the roof. Lightning is part of life in the rains in this part of the world. How does one deal with it regards a solar system ??

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7 minutes ago, Richard Mackay said:

You should also contact your bond insurance and have your system listed on the itinerary of your house.

When lightening strikes it is catastrophic for electronic equipment. (My inverter has plug in MOVs for the PV connections for easy replacement but I doubt how effective it is)

First thing I did was to contact my home owner's insurance to make sure my inverters and the whole system is covered. They only requested me to send them a copy of the CoC and asked me to keep the original for any future claim. I'm considering installing surge protection on the DC side. Only has it on my AC side 

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So earth the panels (strings) and get insurance. Then pray. Hmmm sounds like a plan.

Any thoughts on taking the fuses out of the line between panels and charge controller to act as a physical air break - nothing lost if this is done at the end of the day and put back early bells in the morning. That way if (when) a nasty storm rolls in over night any potential surge from a nearby strike is contained.

Strangely I also lost 2 light globes in the event 2 nights ago. A compact fluorescent and a new led bulb - both in or near the kitchen area. Odd.

I was worried my inverter might have suffered damage but it came back on last night and charged the batteries back up so all good. It was just a grid down for a bit over 24 hours because of the heavy rain. As soon as a dog pees on a power pole the grid goes down around here.

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OK ....so I am probably over thinking this but something like this would be a good setup to have

benedict.at/files/documents/4525177-D879E-161.pdf

Its a DC contactor. Have that controlled by a timer and the PV array can be disconnected every evening and reconnected every morning with no intervention other then an emergency stop for storms during the day.

Take it up a level..... have the contactor controlled by a lightning strike meter (cant remember what they are called but they detect lightning strikes at various distances) so that when the strike detector detects lightning within say 20 kilometers it energizes the contactor and disconnects the PV array. Dont know if this is practical but it would be a fun thing to setup (and watch working)

 

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Well another night another storm rolled on through.

Got woken up a bit after 1.15am to the sound of heavy rain and thunder. The lightning was some distance off this time and not directly over us like the other night. Still getting some good flashes and loud cracks but they were a good 5 or 6 seconds behind the flash of lightning so some distance off.

So this storm was not going to damage anything but it proves the point. A storm can roll in anytime of night and do some serious damage from lightning. Other then the hassle  of turning the solar array off early evening and back on again in the morning what is lost by disconnecting the solar array over night? It seems to be a safety factor for whatever is downstream of the solar array in one's system.

I do get this is probably of little interest to you if you are not in a high lightning strike zone.

So i guess i need to look into those contactors as a way of automating the disconnection of the solar array every evening and reconnecting the array back to the charge controller in the morning as the sun comes up

any thoughts anyone? seems to be no interest in this concept.

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16 minutes ago, Dani said:

I like the idea of a contactor that is automated to disconnect at sunset and when lightning is detected within a certain radius. 

I don't think this is the way to go..

The link I posted to the other forum has this pertinent comment:

People often make the mistake of thinking the lightning conductor is there for the lightning to strike or that the arrestors and crows foot spikes on buildings are there to attract the lightning to them and save the building. That 6 - 8 mm alu rod with the 10mm spike or crows foot will melt away if a lightning bolt comes near it and the same goes for the 25mm copper wire that comes with the thatch pole arrestor. One thing that these have in common is the sharp pointy tip and of course a good earth. the pointy tip will discharge electrons in an area around the building or pole and thus minimizing the risk of a positive or negative charge bolt being discharged from the opposite charged cloud. Should a strike occur it provides a low resistance path to ground.

Earth mats and earth spikes are not easy as hitting a spike i the ground or burying a copper mat, these have to be tested to get proper earth conductivity readings and the good old consumer earth in the db should be a reasonable earth, more often than not the neutral is earthed at the point of connection and a earth spike is installed next to it. In the older days the Inspector used to do the earth loop test but nowadays it fall s to the contractor.
PV systems are a new ball game and calls for some serious new approaches and regulations to ensure safety I can see this ending up like the different classes of wiremans licence with a specialist field of its own.

So by providing lightening arrestors this reduces the likelihood of a strike because your structure won't be the 'path of least resistance'..

 

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Correct me if I am wrong......

The array is acting as an "antenna" of sorts. It is up high on the roof facing the sky. A nearby strike generates a "pulse" and is carried through conductors to electronic equipment. That is enough to blow the equipment.

 

It happened to me the other night. My satellite modem is connected by thick RG11 cables out to a large satellite dish. I turned the power to the modem off but left the ethernet cable from the LAN port of the modem to the router connected. We had what must have been a very close by strike. As soon as the flash lit up the room the CRACK!!! was instant. It was quite frightening actually. Scared the shivers out of us !

The modem survived but the router connected via LAN cable got fried. The energy from the pulse of the strike came through the RG cables , through the modem and went down the LAN cable to the modem. and on into the router. The router was powered on and got fried, the satellite modem was powered off and survived.

 

Why couldnt this happen with solar panels connected to charge controllers? What I am considering is that by providing a physical break in the cabling between the solar array up high in the sky and the charge controllers a pulse cant get through to the charge controllers. With the money one needs to invest in charge controllers (DC or AC types) it is worth considering how to protect them from strikes...especially overnight when they are just sitting up there exposed and doing nothing useful.

We tend to get our heavy rain at night here. With rain comes lighting and thunder. Its a serious problem.

I am not suggesting that this is going to save anything in a direct strike scenario. If you get a direct strike the least of your worries is your charge controllers.

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It's a big problem. In the days of ADSL routers it was virtually impossible to protect those routers. The strike would come down the telephone wire (from faraway) and zap the router. Now with fibre it's a lot better..

Yes you can disconnect the equipment and if you have the energy to do this it will help. But remember that the mains cabling is also a path for the strikes to take out equipment.  So just ensure that your house (bond) insurance covers this damage!

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2 hours ago, Delta9 said:

Well another night another storm rolled on through.

Got woken up a bit after 1.15am to the sound of heavy rain and thunder. The lightning was some distance off this time and not directly over us like the other night. Still getting some good flashes and loud cracks but they were a good 5 or 6 seconds behind the flash of lightning so some distance off.

So this storm was not going to damage anything but it proves the point. A storm can roll in anytime of night and do some serious damage from lightning. Other then the hassle  of turning the solar array off early evening and back on again in the morning what is lost by disconnecting the solar array over night? It seems to be a safety factor for whatever is downstream of the solar array in one's system.

I do get this is probably of little interest to you if you are not in a high lightning strike zone.

So i guess i need to look into those contactors as a way of automating the disconnection of the solar array every evening and reconnecting the array back to the charge controller in the morning as the sun comes up

any thoughts anyone? seems to be no interest in this concept.

You still have another possible path to the inverters that you will have to disconnect to make sure they are safe from lightning. The Neutral and earth wires on the AC side 

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17 hours ago, hoohloc said:

You still have another possible path to the inverters that you will have to disconnect to make sure they are safe from lightning. The Neutral and earth wires on the AC side 

Thats a point. I have lightning arrestors on in my DB board for incoming power from grid including neutral. Not sure how effective these are. Does earth need to be considered here?

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