David Nebenzahl wrote:
Sorry, I don't think you know what you're talking about.

You seem to think that you can "force" or push "voltage" into a line,
by using a higher voltage than what's on the line.

That's not at all what's at work here when one has a photovoltaic
system and an intertie feeding power back into "the grid".

The intertie and the house's power connection are going to be at
pretty much exactly the same voltage. What happens is that the PV
system is connected *in parallel* with the grid; it's dumping more
*current* into the system, not more voltage.

You do understand the difference between current and voltage, don't
you?

"Pretty much the same" is not the same as "the same". The grid may have very low
impedence, so the voltage difference will not be much, but if the voltage you
produce is less than the grid voltage, no current will flow from you to the
grid. The higher your voltage is above the grid voltage (at your house), the
more current will flow into the grid. Kind of like charging a battery - until
you exceed the battery voltage, no current will flow. As the voltage exceeds the
battery voltage the current increases rapidly.