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In one-phase system, voltage is distributed over one phase while the other is called "neutral" and should be grounded, AFAIK. But, I think that I have experienced shock when touched one phase in 3-phase system, which does not even have a common ground. Is it charging-recharging of the the body capasistance? Is it less adverse than plugging a person between the phase and ground/neutral? If that is the case then why does the phase gives you the shock but ground does not? I see that birds are fine sitting on the power transmission lines, the high voltage one, I suppose.

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  • \$\begingroup\$ Even though you are refering to a three or four wire three-phase system, each phase definitly has a potential to ground, usually the midpint. DON'T TOUCH ANY PHASE! \$\endgroup\$ – winny Oct 3 '16 at 14:32
  • \$\begingroup\$ Three-phase DELTA connections are not ground-referenced. However, they are high-power, and capacitive coupling in the large transformers, switchgear, and wiring can easily generate enough current to break through your outer skin insulative layer. It wouldn't be enough current to light a lamp. But potentially enough to kill you. Touching live phases, at ANY mains voltage, whether "ground referenced" or not is simply suicidal behavior. Dunno know why anyone would do that? \$\endgroup\$ – Richard Crowley Oct 3 '16 at 14:45
  • \$\begingroup\$ Birds just do not know what they are sitting on. You know now :) \$\endgroup\$ – Anonymous Oct 3 '16 at 14:52
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If you have a 3 phase star mains system then there is always a common ground ( the to earth connected center on the transformer) and therefore a way of the current to pass from the touched phase trough the body to earth.

In a 3 phase delta mains system there is also a way for the current to pass but this time it is trough the body, the capacitance of the transformer and a different phase on the transformer.

When we have a frequency regulator the above can also take place with the same motivation.

Birds on a HV line can get hurt by lightning because a current can flow from the lightning bolt to the HV line. This in a capacitive sense or when the surge arrester gets activated. Anyway it will kill the bird.

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  • \$\begingroup\$ > then there is always a common ground and therefore a way of the current to pass from the touched phase trough the body to earth. 3 phase delta also -- Which way are you talking about? \$\endgroup\$ – Little Alien Oct 3 '16 at 19:29
  • \$\begingroup\$ Birds on a HV line can get hurt by lightning because a current can flow from the lightning bolt to the HV line. --- The lightening can beat crap of you even if you do not touch any conductor. I do not ask about such extreme cases. \$\endgroup\$ – Little Alien Oct 3 '16 at 19:43
  • \$\begingroup\$ @LittleAlien: The path I described "Phase, Human body,Earth or neutral ( both at the center of the Y connection) back to the phase. \$\endgroup\$ – Decapod Oct 3 '16 at 21:07
  • \$\begingroup\$ @LittleAlien: To get hurt by a current from what ever source there is always a current path. Such a path can be formed in many ways. No current path means no current and in such an occasion no problem. \$\endgroup\$ – Decapod Oct 3 '16 at 21:10
  • \$\begingroup\$ That is the real answer. Unfortunately, even it lacks the explicit mentioning of the body capacitance. \$\endgroup\$ – Little Alien Oct 4 '16 at 3:31
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Can 220v touch shock an insulated person?

Insulated from what? If I touch a wire with my finger and another one with my rubber boots, am I insulated or not? Let's try and answer the other questions first.

But, I think that I have experienced shock when touched one phase in 3-phase system, which does not even have a common ground.

As far as I know, there is always a ground wire in every 3-phase system. Closing a loop between touching a live wire and the ground CAN hurt you. If it is a Y connection, a neutral is present as well.

If that is the case then why does the phase gives you the shock but ground does not?

Touching the ground conductor alone does not shock you because the potential difference between the ground and the ground conductor is well... zero!

Same applies if you touch the neutral wire (DO NOT try it though!), as the potential difference between the neutral and the ground wires should be zero, if everything works correctly. In practice, I think it is normal to observe up to a few volts difference, but again, for safety reasons, DO NOT attempt to close a loop between the neutral and the ground using your body!

I see that birds are fine sitting on the power transmission lines, the high voltage one, I suppose.

This is again because the air acts as a very good insulation between the live "high-voltage" wire and the ground. If it is actually very high voltage, birds can get hurt (see how lightning works).

To clarify things a bit more


To get a better idea, in order for current to flow through a conductor, a voltage difference should exist between the end-points. A conductor can be any path of any material, as bad as air or as good as copper.

Because copper has indeed very good conductivity (in simple terms meaning current can pass through very efficiently and easy), we use it to create closed circuits. On the other hand, because air has pretty bad conductivity (or if you prefer, is a good insulator), it is often used in between end-points, where we do not want to create a circuit (as is the space between air wires and the ground).

What I am trying to say here is that anything can act either as a conductor or an insulator, depending on the voltages we are working with in each case.

This is a very impressive example where due to very high voltages, air temporarily acts as a conductor, where normally should be an insulator.

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  • \$\begingroup\$ Insulated from what? If I touch a wire with my finger and another one with my rubber boots, am I insulated or not? Let's try and answer the other questions first. -- I do not understand why people kidding. What are the birds isolated from? Why should I touch another wire with something to be isolated? By isolated and body capasistance I mean that I touch one wire and do not touch anything else. Insulator is a thing that isolates one wire from another. How can you deal with electricity and not realize that? \$\endgroup\$ – Little Alien Oct 3 '16 at 19:34
  • \$\begingroup\$ As far as I know, there is always a ground wire in every 3-phase system. Closing a loop between touching a live wire and the ground CAN hurt you. If it is a Y connection, a neutral is present as well. ---- In that system I had only 3 pins. That is how I decided that it is a 3 phase motor. Again, stop talking about closing the loop. 'Isolated' and asking about body capasistance mean you did not close any loops. \$\endgroup\$ – Little Alien Oct 3 '16 at 19:37
  • \$\begingroup\$ This is again because the air acts as a very good insulation between the live "high-voltage" wire and the ground --- How can you say that without figuring out what is an insulator first? \$\endgroup\$ – Little Alien Oct 3 '16 at 19:39
  • \$\begingroup\$ You clearly do not understand some basic things about how circuits work. See also @Decapod's comments on his own answer. An insulator is a material that does not allow current to pass through it, it has nothing to do with wires. But you always measure the insulation with reference to 2 other points, there is no meaning in saying "I am insulated from wire A", because you need a second point where the current will flow to. Also, as I told you, every 3-phase system has a ground conductor too. \$\endgroup\$ – DimP Oct 3 '16 at 23:35
  • \$\begingroup\$ Sure I don't. I just read an article about body capacitance, asked the question about antenna operation and do not see anything about 'the second point'. You seem not to have logic. It was clearly exposed to you that it is antilogic to deny the notion of insulation and, at the same time, explain the birds with it. I keep an outlandish belief that nothing can be understood without the logic. \$\endgroup\$ – Little Alien Oct 4 '16 at 3:36

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