RED ALERT
Your undertanding of AC power transmission and connections is flawed
and dangerous.
Gotalk with an electrician explain to him your concept of ac
distribution.
If he laughs ,suck it up and ask him to strainghten you out.
Reference his explainations with your own self study.
mccet
in the biz for quit a while

RB wrote:
For single phase, 220v ac: what is the difference between 3 and 4 wire
systems?

Most 220 comes into houses with three wires. Two insulated, and one bare.
This implies to me that the bare one is also a ground, as well as the 220v
neutral.

I also observe portable generator to house setups using 4 conductor cable.
Why the difference? Are the 4 conductor setups simply using separate
neutral and ground? If so, is there any practical and/or safety reason to
separate the neutral from ground lead?