In contrast to the three cases described above, the reason for grounding the positive
terminal of the power supply battery in telephone outside plant wiring is to minimize the amount
of corrosion on the copper wire. Corrosion effects related to the grounding of the battery would
not occur if the insulation around the wire were perfect (no leakage current whatever) and bare
(non-insulated) parts of the wire were never exposed to moisture or chemically reactive
molecules in the air. It would also be nice, to absolutely prevent corrosion if the insulation
around each wire was a perfect barrier to the passage of metal atoms or ions. If this ideal
situation were to exist, then we could ground either terminal of the battery and not worry about
corrosion. If absolutely all of the current flows from the + to the - pole of the battery only via the Grounding and Corrosion in Telephone Outside Plant p. 3
telephone wires (and through the telephone set), then we would not be concerned about the
current removing or placing (electroplating) copper atoms off of or onto the wires. No current
would leak through the insulation and return to the other battery terminal via the conductive
earth. That would be nice but this desirable situation is not practically possible.
Plastic insulation used today is much better -- lower leakage current -- than paper pulp or
silk or cotton fiber insulation used in the past. But even with very good insulation, corrosion can
be accelerated because the insulation is not perfect and some "leakage" current gets through the
insulation and some metal or oxygen molecules can move through imperfections in the
insulation. The leakage current is typically only in the range of 1 to 10 microamperes, but over a
long time it could cause some serious changes in the wire diameter if we made the wrong design
choice regarding battery grounding
(...)
If we ground the positive battery terminal, then even when the earth is wet, the earth is at
a positive voltage just like the positive (tip wire or green insulation) wire. Therefore, there is
little or no voltage difference between that + wire and the + voltage earth, and there is much less
leakage current and much less "de-plating" of the wire. There may still be some copper plating or
a build up of copper oxide or copper carbonate onto the negative (ring or red insulation) wire if it
is physically close to the wet earth or in a wet corrosive atmosphere.
If we have made a secure metal-to-metal contact of the wire to a screw terminal (or a
type-66 stake-down electrical connection block that cuts through the insulation with two tinplated
metal prongs and grips the copper wire), with no gaps between the wire and the metal
terminal, there should not be a problem with corrosion forming between the wire and terminal. If
we made a loose "sloppy" connection, then there will probably be a problem with corrosion
forming in the gap between the negative wire and the terminal (but not so much corrosion
forming on the positive wire). In that case we would need to occasionally clean the wire and reconnect
it, a definite maintenance problem.

http://lyle.smu.edu/~levine/ee8320/positiveground.pdf

Uziemienie dodatniego lub ujemnego bieguna (opcje
+F282 oraz +F283)
Opcje dodatniego i ujemnego uziemienia biegunów mogą być użyte, gdy moduły solarne
wymagają uziemienia biegunów DC inwertera.

http://www05.abb.com/global/scot/scot232.nsf/veritydisplay/b...$file/PVS800_Hardware.pdf