Hey scottsAI,
I aggree with what you said there. I think it is highly unlikely that an experimental grid tie inverter will have enough capacity to power an entire neighbour hood, so for this sake of this discussion, I aggree with you. But.
The question of backfeeding is one that most definately needs to be considered. I'll give two expamples why:
I live sorta in the forest, with only six houses nearby besides mine. We are all fed from one 50KW transformer, and when the fuse blows on that it is only us six that go down. So, now a hypothetical situation:
It is day time, everyone but me is at work, so in the other houses the only things on are a few friges, a computer or two, maybe a few lights. Max load there would probably be 10KW including my house, probably less than that. Now, smart me decides to connect my (hypothetical ;-)) 12KW deisel genny to my breaker panel, so I can power my whole house. But, I forget to trip the breaker going to the grid, and voila, my small island of 7 houses now has power. If a linesman touches those lines, it will hurt. Probably not kill, since it is only 120 or 240 volts, but still most certainly has the possibility to be deadly. Now I'd have to be a pretty big idiot to do this, but there are people who might. Also, lets say I build a genny from a huge induction motor and fed that straight to the grid to sell back current. If I put capacators on it, it will continue to generate power even when the grid dies. So, again, possibility of a dead linesman.
Now, my second situation is completely true (if you can believe the newspapers, that is, lol!). There is a sort of club/dancehall type place where people have wedding and parties in a remote costal location in my country called Pier 1. It is quite a large place, so their backup generator is probably around 20KW. One day, the power company had turned off electricity in their area to service the lines, so Pier 1's genny was on. But, due to bad installation, etc, it was feeding power to the lines, and the linesman who was servicing them was killed. Yup, killed. Dunno what happened as a result of this, like lawsuites etc, but the fact still remains that a guy DIED. That should be reason enough to be VERY CAREFUll with this sorta thing.
So, I say go to it with your small transformer design, if you know what you're doing. A small transformer with not be able to power even your whole house, let alone your grid, so there is no real danger there. Once you get to larger models though, you should make your own 'mini-grid' to test it with, by using a backup genny or something.
Hope you do well, it is nice to see somebody who feels very strongly about doing this, and is not shot down by other people's negative comments. Keep safe, don't kill yourself or anyone else. And have fun.
Cheers,
Stephen.