Electrical systems have neutral besides live and ground. Electronic systems have only VCC and gnd. I read that having neutral is necessary for safety in electrical systems because of the higher voltage and current involved.

How does having neutral make electrical systems safer?


marked as duplicate by Andy aka, bitsmack, W5VO Dec 28 '16 at 21:08

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  • \$\begingroup\$ I guess this question asks about safetyness and the other one about the technicality of not having a neutral? But they are almost identical, like you said. \$\endgroup\$ – user132236 Dec 28 '16 at 13:46
  • \$\begingroup\$ I believe it is also the same guy posting but I could be wrong. Use of similar phrasing etc.. \$\endgroup\$ – Andy aka Dec 28 '16 at 13:51
  • \$\begingroup\$ In fact if you omit the neutral, the electrical installation won't work because of the fact that the ground wire is not connected to the transformer. The wires that are connected to the power transformer are line (live) and neutral. Earth (ground wire) is there for security purposes as it has been answered. \$\endgroup\$ – Krauss Dec 28 '16 at 14:36

enter image description here

1,2,3 is line,

N is neutral

PE is Earth.

Notice that in this system, there is a fault between L2 and the object chassis. If you don't use earth line (PE), the man is dead.

If you use a PE line, the man will only get a voltage of Uf, as indicated in the picture. Uf << UL2 if Zct and RnA are low resistance, a.k.a you tie the midpoint of the generator/transformer directly to ground.

That's how PE saves your life.

Example 2:

enter image description here

Notice in this picture, PE is tied to all nearby conductors to create an equipotential zone. If there is a fault in either the lamp, motor, washing machine, the whole green area increases voltage the same amount. This way, a guy touching the motor and washing machine chassis can survive even in the event of a fault.

Oh and about electronic systems, they are usually low voltage systems, right? It is very unlikely that someone needs protection from their 5V battery powered Arduino. So for almost all electronic circuits, earthing is not necessary.

  • \$\begingroup\$ Just stumbled upon this question. Why don't they just connect the natural to the chassis instead in the buildings? If all the neutrals are connected to the earth at the transformer side why to pay for extra cable/wire in the houses? \$\endgroup\$ – HelpMee Dec 28 '16 at 14:55
  • \$\begingroup\$ There are many reasons, here is one reason: If you connect N to device chassis then it's possible for the incoming electricity to skip the load (L-LOAD-N) line and do this (L-CHASSIS-N). When this happens not only your device won't work, there will be sparks everywhere (also fire). However, by using a separate conductor (unpowered, PE is unpowered normally) you can connect various chassis of devices and floor/walls of your building altogether to make an equipotential zone to save people from getting electrocuted. \$\endgroup\$ – user132236 Dec 28 '16 at 17:03
  • \$\begingroup\$ PE line also doesn't have to extend all the way from the generator to the apartment. You can ground the generator/transformer, ground the apartment as shown in second picture. The apartment grounding will lower the voltage drop of the fault enough to save the guy. \$\endgroup\$ – user132236 Dec 28 '16 at 17:32
  • \$\begingroup\$ So I guess we can sum up and say that the trick of PE is to make it not viable for regular electricity passage (otherwise PE and N is the same, like you said) but make it low resistance enough for it to drop the fault voltage to a safe level for people. I suspect that using N as chassis earthing/grounding is too much of a viable option for electricity. Definitely some sparks will be seen. \$\endgroup\$ – user132236 Dec 28 '16 at 17:38

The terminology is a bit different between AC and DC circuits, I think that's where the confusion stems from (Earth = dirt ground as opposed to electrical ground).

AC Neutral is the equivalent of DC ground. The Earth is a physical connection to the Earth. (the neutral is commonly tied to earth at and only at the fusebox before the breakers and safety switches).

The Earth is used as a shield (so you don't get zapped) while the Neutral/Ground is the return path for normal current flow.


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