View attachment 234152
What I was saying above was that if the neutral centertap in the secondary output of isolation transformation is not grounded. The Neutral can shift to Line 1 or Line 2, right. So without grounding.. say a resident user put the Line 1 to the ground, then it can become the neutral. And neutral would become hot. The scenario I mentioned above may not work, that is, neutral connecting to other live and it becomes hot. This is because if the neutral connects to hot, it is short circuit and trip the breaker or fry the primaries.
Before I was not so clear about floating secondaries potential. So far this thread makes it clear that
1. Sources of secondary potential floating is from static charges which is little and not permanent.. I thought it was like HUP that the potential can take on any value even the Electroweak potential. And since you can't measure the potential. I wondered yesterday why if the potential take on the electroweak potential, we don't feel any plasma in the room.
2. Even if static charges cause potential changes, the output leads would still be 120v. I though the output lead voltage would vary.
3. If one of the leads touches other hot wires from other transformer, the two leads would still be 120v and it is the potential of the other lead with respect to ground that can have potential differences with respect to the Primary neutral (not the secondary which doesn't have it assuming it's not grounded).
4. And above... only if one of the leads are referenced to ground that it becomes the neutral. So without grounding the centertap, the neutral can shift to the side (L1 and L2 above). Please comment if the above scenario is correct.
At least I don't have to worry about my flat screen TV exploding from potential increase to millions of volts or even the GeV. And don't worry about me trying to change the utility grounding or terminals (of course I won't do it.. I'm afraid of getting shock). I just want theoretical understanding of it. Thanks a lot for those who helped.