I'm a beginner but wouldn't it bring more safety if the neutral is grounded through a different earth connection(2 grounds each connected separately the earth). We would have two neutrals that could operate, safe to touch, and the current breaker still could function if the former hot wire shot-circuit with the neutral or neutral ground wire. The only risk remaining when we touch both the former hot and neutral wire, which could happen if you weren't adapted to this setup thinking that the power is off or somthing.
What disadvantage a setup like this would have?

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closed as unclear what you're asking by brhans, Dmitry Grigoryev, Voltage Spike, Autistic, uint128_t Apr 22 '17 at 0:18

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    \$\begingroup\$ You shouldn't touch neutral because you cannot guarantee that it hasn't become swapped with the live wire. Try capitalizing letters at the beginning of sentences as a mark of respect. \$\endgroup\$ – Andy aka Apr 18 '17 at 12:48
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    \$\begingroup\$ "different earth connection": different to what? I don't think you've sufficiently described what you've got now. So, your proposed change isn't fully understandable. \$\endgroup\$ – Marcus Müller Apr 18 '17 at 12:49
  • \$\begingroup\$ Ok i corrected my question taking both your advises into consideration. \$\endgroup\$ – habibhassani Apr 18 '17 at 12:55
  • \$\begingroup\$ so, I still don't fully understand – in what context are you considering this? Industrial installations? Home wiring? Device cables? Supply grid? \$\endgroup\$ – Marcus Müller Apr 18 '17 at 12:58
  • \$\begingroup\$ Andy aka let's say that my home installation is correct or that i verified each wire. \$\endgroup\$ – habibhassani Apr 18 '17 at 12:59

The resistance of a ground rod is highly variable, depending on the soil conditions. In damp earth, it may only be tens of ohms. In dry areas you may struggle to get hundreds of ohms.

If the soil resistance is at the low end, then there won't be a high resistance between the two rods. The ground around them will get hot from the current flowing (and somebody will be paying for this heating), and the rods will eventually dissolve from the electrolysis.

If the resistance is high, then the ground rods aren't actually achieving anything much anyway.

But in terms of safety, it won't achieve anything either. The neutral is (relatively) safe, because it's firmly grounded. If you stand on the earth and touch it, the neutral and the earth will only be a few volts apart at most.

If you ground the live, then all the ground around the live rod will be pulled up towards the live voltage. If you stand on that and touch the neutral, you will get a shock. Similarly, if you're standing near the neutral rod, and touch the live, you'll still get a shock.

  • \$\begingroup\$ Thanks, so what if we add a strong diode to the grounds ? wouldn't this solve the problem \$\endgroup\$ – habibhassani Apr 18 '17 at 17:45
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    \$\begingroup\$ @habibhassani please stop. You have no idea what you're talking about, and it shows. Your ideas make no sense, and adding more things to them doesn't help. \$\endgroup\$ – Marcus Müller Apr 18 '17 at 20:08
  • \$\begingroup\$ @MarcusMüller i said, i'm a beginner that's why i'm asking, to learn more, so why are you objecting for. \$\endgroup\$ – habibhassani Apr 18 '17 at 21:43
  • \$\begingroup\$ @habibhassani Since we're talking about AC here, adding a diode would mean that the hot or neutral would be only be grounded half the time, depending on which way round you put the diode. \$\endgroup\$ – Simon B Apr 18 '17 at 22:07

What disadvantage a setup like this would have?

Assuming (North American-Style) Residential/AC conditions:

1) Adding another "different earth connection(2 grounds each connected separately the earth)" increases the possibility of the two grounds being at different potentials, causing all sorts of undesired secondary effects. The primary being the possibility of shock just from the existence of two grounds. Lesser: introduced noise and interference due to -everybody's favorite- the introduction of local ground loops. You would be, in effect, intentionally defeating the desired "Star-Ground" topology that most systems strive for.

2) Adding cost, for no real increase in system capability or user safety. Copper is expensive. Adding another wire, with the same functionality, does not inherently increase system safety or reliability. Matter of fact, I would argue that in the system you describe, the extra wire would decrease safety due to two separate ground points. The additional cost for the extra conductor is not justified.

Remember, the neutral and ground are bonded together at a singular, central point. This common ground must then be directly connected to earth. The conductor size of both the neutral and ground are designed to be able to carry the full short-circuit load of the electrical branch in which they are located. Ideally, the neutral is always at the same potential as ground.

  • \$\begingroup\$ Thanks for your answer, and bear with me i'm a beginner. so do you mean by shock a short circuit, if so assume theoretically that ground connections are isolated from each other. and isn't different potentials if there is one would be so insignificant to cause a problem ? as for the cost, you maybe right but isn't it safe to have 2 neutrals for children or mistakes due to oversight etc. \$\endgroup\$ – habibhassani Apr 18 '17 at 15:29
  • \$\begingroup\$ "shock" means an injured or deceased user. \$\endgroup\$ – The Photon Apr 18 '17 at 17:12

The earth isn't that high resistance, it is used as an actual return conductor in the TT type of mains system.

What you are probably thinking of is an IT type mains - which is indeed used in safety critical places like surgical theaters at times. It comes with the disadvantage that some safety devices that work with the standard TN-S/TN-C systems will NOT work - especially with TN-S it is easy to discern an intentional load from an accident (as an RCD does), while it is very difficult to do with IT. There is less risk of an accident from ONE conductor being touched (short of capacitive effects) - but an insulation failure plus body connection can go totally undetected until a condition is reached where the other conductor is touched too, causing the worst possible accident.

  • \$\begingroup\$ TT systems do not use the earth as the return (i.e. neutral) conductor; it only carries leakage current. \$\endgroup\$ – Someone Somewhere Apr 14 at 10:10

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