Voltage on one lead of solar panel/string

[ttpvt1]

Can someone explain what the voltage on one lead (+ or -) of a solar panel/string is?
Obviously testing voltage from one lead to the other is Voc.
From experience, testing voltage from one lead to ground shows a small initial voltage which quickly dissipates to 0. Does this mean that touching the bare conductor from one lead of a panel (or string) presents no shock hazard?

[SunEagle]

Depends on the voltage level. OSHA has stated that anything below 50VDC is safe to touch and will not hurt someone due to the high body resistance between the voltage source and ground. But if you shorted out a 12V battery + and - terminal you would see fireworks that could burn or even kill you.

[bcroe]

When you touch/measure voltage from one lead to the frame of an otherwise unconnected
panel, you do not have a complete circuit. Therefore you will not be able to draw any
continuous current. Connecting a very high input impedance voltmeter might give an
initial reading of voltage but no current/power. This is caused by static charge or extremely
small leakage of the insulation, charging minute stray capacity with a few electrons. The
energy content is less than you get rubbing your feet on the rug.

Most single panels do not develop enough voltage between leads to be dangerous. Strings
of panels can be very dangerous, mine run at 400VDC. Bruce Roe

[ttpvt1]

Thank you all for responding! I would like to follow up with a video showing voltage testing to ground from one lead of the module. Can anyone provide explanation for these results?

https://drive.google.com/open?id=1-BuW2SXaYP0Sdv8uDIDzj9Su5L9ZYRbs

https://drive.google.com/open?id=1AKjBydjs5EExaSEu9lLUC_vp8gi_-pLr

[littleharbor]

Unable to play video. Anybody else?

[Mike90250]

testing from a PV wire to ground is not a valid test

[Sunslacker]

Thank you all for responding! I would like to follow up with a video showing voltage testing to ground from one lead of the module. Can anyone provide explanation for these results?

https://drive.google.com/open?id=1-BuW2SXaYP0Sdv8uDIDzj9Su5L9ZYRbs

https://drive.google.com/open?id=1AK...LUC_vp8gi_-pLr

You may have yourself a pinched wire somewhere in the installation. I'd go check each module where the frame comes in contact with the ballast for the string you're picking this up on.

[bcroe]

A voltmeter is for measuring the difference in potential between points (nodes) in a circuit. A circuit
is a connected arrangement of legitimate electrical components. The active elements of a panel are
not connected to the frame. Unless they are connected externally (apparently not in this case) you
do not have a circuit, so a so called measurement is meaningless.

What is happening here, is there is a very small amount of capacity (because nothing is perfect
without any slight unintended effects) exists between the panel elements and the frame. Something
like static electricity has put a few electrons into the cap giving a voltage. A (digital) meter with half
a dozen orders of magnitude higher impedance than needed for this work is connected and detects
this arbitrary voltage. But even this meter draws a few electrons to make the measurement, which
slowly discharges the cap, so the voltage heads slowly down.

This job does does not require lab level resolution or impedance, a plain old self powered swinging
needle meter would instantly drain the static charge to read zero with adequate resolution. I use
light bulbs on my array, just like I did on power distribution good/bad at work. It would be really cool
if that digital screen lit up, THIS IS NOT A LEGITIMATE CIRCUIT. Bruce Roe

PVtestLt.JPG