Hi again,
to complete the thread and the right answer about grounding systems i add some links to some WIKIs about the power line system. The WIKIs explain the consumer power line and the earthing system better than i could do it.
The main point on this is to show up how the earthing from power lines works. Usually the TN-C and TN-C-S / TT sytems are used in our households. On the pictures from the Wikis you can see, that L1, L2, L3 feed the loads and that PE (Protection Earth) and the N (Neutral) come together at the supply generator. As mentioned before, Earth and Neutral are splitted in the household. L1, L2, L3 are hooked up to the loads via circuit breakers. Neutral (N) is used as device / household grounding, the Earth (PE) re-combines the Neutral with the earthing and goes back to the PL Supply.
Earthing SystemThis is how GCFI (Residual current devices) works:
Residual current trapsVideos about GFCIThe neutral conductor and the live conductor go through a coil (balanced transformer core).
If a residual current (current due to a circuit failure) runs into the neutral, the transformer is inbalanced and switches the breaker.
Personal protections switch down at 4 to 6 mA - device protectors in the range of 40 to 80 mA (depends on the installed systems).
IMO - the basics of mains wiring are the most important things someone should know when building High Voltage circuits.
@Steven - i wish i could write like you

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Have fun

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