Electronic – Is ground connection in home electrical system really necessary


I know that the answer to my question is "Yes, it is!". The ground connection is needed to avoid a person touching a metallic part of faulty equipment to be electrically shocked. So the person acts as the conductor closing the circuit between the high voltage metallic part and the ground (at zero volt by definition). The grounding connection hence offers an alternative path for the current to flow, and this happens because somewhere along the power distribution system, the neutral wire N is connected to a metallic rod planted into the ground.
My question is: what if this neutral wire – ground connection is removed, as illustrated in the picture? This would make the ground wire in home electric sockets unnecessary, since a person touching the metallic case of a faulty equipment doesn't close the circuit, because there is not the circuit including the ground. So, as I understand it, this would work (maybe) if the power distribution system is not grounded anywhere. Is this possible to realize a totally floating-from-ground power distribution system? I am pretty sure the answer is no, but I don't know why… so, why is not possible???
Thank you.

Electrical power system without ground connections.

Best Answer

What you are not considering is that an earthed chassis or metal box containing a "rogue" live connection will be self-revealing should a fault occur that causes live to touch the earthed metal. It will blow a fuse and within a few milliseconds the problem is made safe and revealed.

For an isolated AC source (such as the secondary of an isolation transformer), there is nothing to reveal that live may have come into contact with the metal box. You can touch it and maybe receive a small tingle but, it isn't clearly self-revealing.

Fault 1 has occurred and it is not self-revealing...

Some time later, another fault occurs that can be anywhere on your street and in any of the houses on that street. That fault causes neutral to become connected to earth.

Fault 2 won't self-reveal either because it won't blow a fuse: -

Then you touch the unearthed metal box or chassis: -


simulate this circuit – Schematic created using CircuitLab

The magenta arrows show the flow of electrocution current

Now, the metal box is a death trap (because it isn't earthed) and is awaiting the next unlucky person to come along and touch it. Nothing has revealed itself that tells you a dangerous situation has arisen.

The first "hint" (if you survive the hint) is electrocution.