Underground wire short....

[SkyMo]

I had an issue that I think is caused by very alkaline/salty water getting into my cable run and causing a short.

I am using a 150ft run of 6 gauge copper connected to 15 240 watt panels in a 5s3p configuration. I have two sets of panels wired like this, each to its own inverter and all in the same 1 1/2 plastic conduit. The full short amperage is 9 amps, so the max amperage is 27 amps and this 6 gauge is rated twice that. Normal voltage is around 175 volts. It's been working for 3 or so years no issues and last week we had a sudden thunderstorm and water pooled around my panels and drained into the conduit (my fault for not covering it up). As you can see by the pictures, it shorted out. Even during the brightest days, the cables do not get hot.

I'm thinking that the silt that washed into the conduit was highly conductive that this caused the shorts.

Does this sound reasonable??
Should I run the positive leads though a different conduit than the negative ones? I ran spare conduit.

 

[efficientPV]

More likely lightning caused a puncture of the insulation and water did the rest.

 

[Supervstech]

I had an issue that I think is caused by very alkaline/salty water getting into my cable run and causing a short.

I am using a 150ft run of 6 gauge copper connected to 15 240 watt panels in a 5s3p configuration. I have two sets of panels wired like this, each to its own inverter and all in the same 1 1/2 plastic conduit. The full short amperage is 9 amps, so the max amperage is 27 amps and this 6 gauge is rated twice that. Normal voltage is around 175 volts. It's been working for 3 or so years no issues and last week we had a sudden thunderstorm and water pooled around my panels and drained into the conduit (my fault for not covering it up). As you can see by the pictures, it shorted out. Even during the brightest days, the cables do not get hot.

I'm thinking that the silt that washed into the conduit was highly conductive that this caused the shorts.

Does this sound reasonable??
Should I run the positive leads though a different conduit than the negative ones? I ran spare conduit.

While not impossible, water could only cause wattage loss… a failure like that would need to be direct wire to wire damage, chafed conductors in contact with each other. Or, like suggested, lightning.

What kind of grounding do you have on the array and the wire way?

 

[SkyMo]

I have the array itself grounded, and the a cheapo once built into my combiner box, but I don't have a lighting arrester. Not yet anyway as I just ordered a set of them and will ground this property. Is this a case where lightning in the area, even though I did not get a direct hit, could have caused this?

 

[Supervstech]

I have the array itself grounded, and the a cheapo once built into my combiner box, but I don't have a lighting arrester. Not yet anyway as I just ordered a set of them and will ground this property. Is this a case where lightning in the area, even though I did not get a direct hit, could have caused this?

No, lightning would have had to hit for it to cause this kind of damage.
Induced would only be a voltage spike.

 

[efficientPV]

Not necessarily. I had a small panel on a pole less than 5 feet from a tall garage and ten feet in another direction a tall tree. I had put this panel up just a year earlier and noticed a small hole in it. No visible damage on anything else in the area. I had bought some used panels cheap because they matched what I had. Once I cleaned them, I could see burn areas on adjacent cells. Each panel had between 7 and 19 of these. Then I looked at the ones I bought new and saw the same thing. I had a strike on another array and that could have been from then. I was on the porch of my other house and some temporary fencing for the dog was loosely connected to a metal downspout. All at once sparks flew out where the two pieces touched. There was lightning, but no close event. I know what that is like, one hit 30 feet away from me. magnetically induced currents can cause a lot of damage.

 

[Supervstech]

30 feet is considered a direct strike in my book...
I was talking about a mile away, em wave. Voltage can sure be high, bit likely it takes amps to destroy cable.
Volts can take out insulation though, and contact later can destroy with amps