"common ground" stands as the principle, it may be the
active grid ground, an abandoned grid ground or one that
the property owner installed in a "virgin" off-grid location.

One needs a way to measure that their common ground is
a good ground. The meters to do so can be costly off-
the-shelf but may be borrowed, bought used, or perhaps
an already equipped friend or neighbor will do the test.

 Um, power company? We are offgrid, lol.
 
 I installed a copper ground rod at my pv array,, and everything grounds
 at that point.