Electrical shock with wet panels

[bcroe]

Hi wondering if someone can help,

We had pigeons nesting under the solar panels, so had a company come in and put chicken wire in the gap, however this didn't work and they managed to still get in. We researched and saw that you can put metal mesh from the aluminium frames down to the roof and this works. My husband did this with metal screws and washers. He did this sat on the roof and when he got to the back where he couldn't sit on the roof any longer, he went to finish it off standing on the ladder.
As soon as he touched the solar panel he got a shock, so the panels were live.
In all the forums he looked in, it said you can drill into the aluminium frame, he drilled into the lower part.
What do we do now, to stop the panels being live?

Please help, thanks in advance

Your installer should have connected a safety ground system to every panel
frame. I suggest you have him inspect the system and find the fault.
Bruce Roe

[Rowan1972]

Hi wondering if someone can help,

We had pigeons nesting under the solar panels, so had a company come in and put chicken wire in the gap, however this didn't work and they managed to still get in. We researched and saw that you can put metal mesh from the aluminium frames down to the roof and this works. My husband did this with metal screws and washers. He did this sat on the roof and when he got to the back where he couldn't sit on the roof any longer, he went to finish it off standing on the ladder.
As soon as he touched the solar panel he got a shock, so the panels were live.
In all the forums he looked in, it said you can drill into the aluminium frame, he drilled into the lower part.
What do we do now, to stop the panels being live?

Please help, thanks in advance

[bcroe]

Normal Array Leakage Current

I went out to get a handle on this; here are the results.

The system is in 2 identical arrays that had been running all day.

Array description: 5 strings of panels: 2 strings with 10 panels of 72 cells and 3 strings
of 12 panels of 60 cells; 6" X 6" cells. About 820' of PV 10 gauge wire, 75' of that
underground in plastic conduit. 460' of 6 gauge buried in plastic conduit.

Mostly sunny, 1 deg F. Both sides measured the same. Operation was at about 404 VDC.
I went out while power was dropping, about 1KW, and opened the DC disconnect switches.
All power connections were broken. Either array open circuit voltage was about 454 VDC.

Voltage drop across a 1 ohm resistor was monitored by a DVM, to determine the current.
One end of the resistor was tied to ground metal, and a probe on the other end made
contact with an array + or - terminal. If there was leakage current from the array to
ground, it could flow through this resistor. Each milliamp of current would produce a
millivolt across the resistor. I noted there was a small spark on INITIAL contact, probably
due to static charge of the capacity to ground (No, I didn't measure the capacity THIS TIME).

Current through the 1 ohm resistor was too low to register on my MV DVM. I switched
to a 1000 ohm resistor, 1 mv = 1 micro amp. I found the current would start around 5
micro amp, but over some seconds trail off to 3 micro amp or less. This was consistent,
on either the + or - terminal, either array.

I concluded each array was properly insulated, and the current was lower than I anticipated
given the voltage and amount of insulation involved. If it were a steamy rain soaked day
I would expect an increase, but that measurement will have to wait till summer. Bruce Roe

[SoCalsolar]

That just confirms what I said. The point I was making is 300 ma is more than enough to kill you. 30 ma is quite painful but not considered lethal to a healthy person and about what a Stun Gun supplies. Enough to knock you down and paralyze you for a few minutes. Now if you are on your roof and get hit with 30 ma may kill you when you fall off the roof. Grounded systems are dangerous.

That sounds like a possible new addition to the X Games Competitive Stun Gun Aerobics on a roof.

[Sunking]

The amount of time exposed matters.

That just confirms what I said. The point I was making is 300 ma is more than enough to kill you. 30 ma is quite painful but not considered lethal to a healthy person and about what a Stun Gun supplies. Enough to knock you down and paralyze you for a few minutes. Now if you are on your roof and get hit with 30 ma may kill you when you fall off the roof. Grounded systems are dangerous.

[sensij]

100 ma is considered lethal.

The amount of time exposed matters. The 30 mA delta trip level is what is designed for human safety. If your point is that the 1 A fuses on the Fronius and other grounded transformer based inverters will not prevent lethal fault current, I fully agree!

[Sunking]

SolarEdge uses a detection technique similar to SMA, and also chose a 30 mA delta current as the trip threshold. This is a value in operation, not a start-up check. They report that changes as low as 15 mA may trip in some systems. Their default absolute level is 300 mA, but it can be set as low as 100 mA.

100 ma is considered lethal.

[sensij]

SolarEdge uses a detection technique similar to SMA, and also chose a 30 mA delta current as the trip threshold. This is a value in operation, not a start-up check. They report that changes as low as 15 mA may trip in some systems. Their default absolute level is 300 mA, but it can be set as low as 100 mA.

[bcroe]

Yeah, your Fronius's design doesn't give the same level of ground fault detection that the transformerless SMA's can achieve. A 30 mA change in current, or 100 mA absolute current, is enough to trigger it. Here is one of the presentations that discusses it from when the product was being launched.

The Fronius perform well, but their Ground Fault technology is crude. I see it as quite
adequate for equipment faults, but not for people. That isn't an unusual situation in
powerful systems.

Detecting .030A DC before startup isn't so difficult. Detecting DC leakage in operation
is much more difficult, unlike the .005A AC detectors for people. I really wonder what
is the practical limit given that a huge array of outdoor equipment is going to have
leakage at some level?

Now I will need to set up an experiment to see just what my systems leakage is. I will
ground one terminal through a shunt (1K ohm resistor) and measure the shunt voltage,
then try it again grounding the other terminal instead. Will do East and West systems.

Bruce Roe

[sensij]

The "GFI" detector in my inverters requires over 1A of leakage current for any response.
That is way beyond a safe level for personal. GFIs for people trigger at 0.005 A or less.

If you are getting a tickle from panels, there may indeed be faulty insulation there. But
as for my own hide, I always assume there is a fault and keep myself isolated from any
active elements of the system. Bruce Roe

Yeah, your Fronius's design doesn't give the same level of ground fault detection that the transformerless SMA's can achieve. A 30 mA change in current, or 100 mA absolute current, is enough to trigger it. Here is one of the presentations that discusses it from when the product was being launched.

[bcroe]

If there is a conductive path from DC to ground, whether it was put there intentionally or it occurs by a bad glass seal and water providing continuity to the frame, shouldn't that trigger the inverter's GFDI?

The "GFI" detector in my inverters requires over 1A of leakage current for any response.
That is way beyond a safe level for personal. GFIs for people trigger at 0.005 A or less.

If you are getting a tickle from panels, there may indeed be faulty insulation there. But
as for my own hide, I always assume there is a fault and keep myself isolated from any
active elements of the system. Bruce Roe

[Sunking]

If there is a conductive path from DC to ground, whether it was put there intentionally or it occurs by a bad glass seal and water providing continuity to the frame, shouldn't that trigger the inverter's GFDI?

Yes if it is wired correctly to code. That is what it is there for.

[sensij]

If there is a conductive path from DC to ground, whether it was put there intentionally or it occurs by a bad glass seal and water providing continuity to the frame, shouldn't that trigger the inverter's GFDI?

[Mike90250]

Wet glass can have electrical leakage along the conductive water path, dry glass is an insulator. But the bigger question is how it's happening. The DC connectors should be sealed, and not allow any leakage. This then indicates maybe the glass/frame seal is bad, and the moisture conducting from there. That would be VERY bad, and cause early panel failure.

Another test, is to get a Neon light based tester, and see if the current is DC (one side of the bulb lights) or AC (both elements light) There is a chance that Induced AC is appearing on the panels - are there high voltage powerlines in the neighborhood ? I could on dry days, get a tingle from my car, when working on it, induced from the power lines across the street:ViewInstall_c.jpg

[sensij]

The SB is 4000TL. Modules are grounded with normal grounding from the structure.

Why would you ground the DC- of this inverter? From the manual:

6.4.2 Conditions for the DC Connection
The inverter is transformerless
and has no galvanic isolation.
Therefore, the inverter may only be
operated with ungrounded PV arrays.