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My solar array just fired off two "gunshots"


MdF

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Now that I have your attention, yes, the title of this thread is correct 🙄

Was working in the house just now and heard a loud bang from outside. It did indeed sound like a gunshot. It was not the seeds falling from the next door palm tree onto a corrugated tin roof.

I had a look at the solar array on the roof and there was no sign of visible damage, smoke or anything else. So I went back inside and looked at the inverter and installation setup. Nothing was untoward, no error messages or anything. All working perfectly fine. Solar power was being supplied to the system at the usual rate that it does for this time of day.

Five minutes later another loud bang. This time I climbed up on to the roof to have a closer look at the solar array. Was mindful not to touch anything. Every single panel looked fine. There were no cracks or deformities or broken glass or anything. All wires looked edzachery how they should and there was no visible sign of burning or melting.

Since then, which was about an hour ago, no further gunshots.

So to the experts out there, some kind assistance please as to what on earth happened 🤔

MdF

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16 minutes ago, MdF said:

some kind assistance please as to what on earth happened  🤔

Totally wild guess: some insulation broke down and there is arcing? Either PV to PV or PV to earth. Depending on the MPPT configuration, it could have half waves of 50 Hz AC from one of the PV inputs to earth. But if that was the case, I would not expect the system to carry on as if nothing happened.

I'm also at a loss as to how to test this wild theory.

Another wild theory: miscreants taking pot shots at your array, and they have bad aim?

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My thoughts about arcing too but the system is working perfectly fine.

Have contacted the installer and reported this to him as well. Will feedback here what he says.

But dang, it is so interesting indeed.

Defo not miscreants taking pot shots.

MdF 

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1 hour ago, GreenFields said:

Everything tied down securely? Nothing flapping and banging in the wind?

Everything is secure and tied down correctly. 
Gunshots heard just after peak production of PV to recharge batteries. Not sure if this is relevant?

MdF

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Normally,

Earth leaks from power below 800V does not create such a loud bang. If there are any earth leaks your inverter should have an alarm message indicate PV Isolation error or something.
 

Was there any sudden temperature changes?  Like clouds moving over  and then cleared again?

Edited by Erastus
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3 hours ago, Erastus said:

If there are any earth leaks your inverter should have an alarm message indicate PV Isolation error or something.
 

Was there any sudden temperature changes?  Like clouds moving over  and then cleared again?

Absolutely no errors on the inverter at all. All was working as it should. Checked all the displays for any other system errors and nothing showed up. Checked all the fuses and trip switches and all were in the correct on position.

No sudden temperature change at all. It was a clear sunny morning with no cloud cover at all and so the ambient temperature increased like on a normal sunny day in Joburg.

As posted above previously, "Another possible explanation could be deformation due to thermal expansion?" seems like the most probable cause 🤔

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7 hours ago, MdF said:

As posted above previously, "Another possible explanation could be deformation due to thermal expansion?" seems like the most probable cause 🤔

To have bang shot = to a gun must be extremely high deformation.Normally if a cable does that it will keep on doing it unless "it moves". are you sure its from the solar?

If it is and you find out let us know.  Does not make sense at all and you are not aware of any tokolos or UFO's?  😉

Extremely interesting a bang that loud you can see black marks on the metal if it was electricity.  Then it seems it is some sort of deformation  due to the temp which is very extreme for a normal constant rise in C.

Would love to know what it was.

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1 hour ago, Vaal said:

Hmm, what about thermal expansion on any structural bolts or brackets, causing bolts to break? How long ago was your array installed? I'm just thinking when some bolts on my carport sheared off due to shrinkage when it was very cold.

I am planning on doing a mored detailed inspection this week once the rain has let up.

The installation was done in July this year so still very new.

MdF

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On 2021/12/04 at 9:13 AM, Erastus said:

Normally,

Earth leaks from power below 800V does not create such a loud bang. If there are any earth leaks your inverter should have an alarm message indicate PV Isolation error or something.
 

Was there any sudden temperature changes?  Like clouds moving over  and then cleared again?

Solar panel output does not "leak" to earth . It can only "jump" from plus to minus unless you connect minus to earth.

 

 

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15 minutes ago, Jaws said:

Solar panel output does not "leak" to earth . It can only "jump" from plus to minus unless you connect minus to earth.

 

 

Pitted cable we refer to leaking electricity to earth.  Happens often on certain of the connectors combined with rain ...

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On 2021/12/05 at 10:22 PM, MdF said:

The installation was done in July this year so still very new.

Temperature expansion seems to me the most plausible explanation. Installed in July - at what temperature were the clamping bolts tightened?

Perhaps - you should go up there on a warm day, loosen and re tighten the bolts again.

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12 minutes ago, Beat said:

Temperature expansion seems to me the most plausible explanation. Installed in July - at what temperature were the clamping bolts tightened?

Perhaps - you should go up there on a warm day, loosen and re tighten the bolts again.

Thanks Beats, that sounds like a good plan.

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On 2021/12/06 at 1:17 PM, Jaws said:

Solar panel output does not "leak" to earth .

? Why not?

The usual "transformerless" higher voltage PV charge controllers typically have half sinusoid waves of AC output superimposed on the DC PV voltage, when measured with respect to earth. This can leak to earth, sometimes causing nuisance trips, and at other times causing inverter problems, e.g. excessive bus voltage.

Just a bare panel or string of panels can have a leakage conductance to the frame(s), which is(are) usually connected to earth.

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On 2021/12/07 at 11:15 AM, Coulomb said:

? Why not?

The usual "transformerless" higher voltage PV charge controllers typically have half sinusoid waves of AC output superimposed on the DC PV voltage, when measured with respect to earth. This can leak to earth, sometimes causing nuisance trips, and at other times causing inverter problems, e.g. excessive bus voltage.

Just a bare panel or string of panels can have a leakage conductance to the frame(s), which is(are) usually connected to earth.

Are yopu referring to a string or a single panel or to the cables?

 

It takes about 30,000 volts per centimeter, or about 75,000 volts per inch, to jump a clear air gap. Once the gap is ionized, the sustaining voltage is less.

That’s in normal air, at normal temperature, humidity and air pressure, with nothing else near the gap. Sharply pointed electrodes can reduce that a bit for short gaps. Nearby ionization sources can also encourage arcing.

Edited by Erastus
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On 2021/12/07 at 11:15 AM, Coulomb said:

? Why not?

The usual "transformerless" higher voltage PV charge controllers typically have half sinusoid waves of AC output superimposed on the DC PV voltage, when measured with respect to earth. This can leak to earth, sometimes causing nuisance trips, and at other times causing inverter problems, e.g. excessive bus voltage.

Just a bare panel or string of panels can have a leakage conductance to the frame(s), which is(are) usually connected to earth.

The sinusoid waves should be less than 5% of the peak voltage AFAIK, in order to meet regulations. That usually means plenty of capacitors to "bridge" the gap in grid-tied (battery-less) inverters.

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9 minutes ago, Erastus said:

Are you referring to a string or a single panel or to the cables?

One or more panels. It's also possible for cables to leak to earth, but it's far less likely.

 

10 minutes ago, Erastus said:

It takes about 30,000 volts per centimeter, or about 75,000 volts per inch, to jump a clear air gap.

Yes, but moisture can conduct enough current to cause problems without ionising air.

But I'll agree that a small leakage is very unlikely to cause a gunshot type of sound.

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  • 5 months later...

Afternoon All,

Just an update to this issue and it turns out there is an axplanation for this - it has nothing to do with the solar array 🤨

One of our neighbours is setting off thunderbolt firecrackers because the neighbours next to him have a noisy dog and their children play outside a lot. So he will set off these crackers in his garden next to the boundary wall to try and frighten their dog.

Not good indeed, but mystery solved.

MdF

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