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I live in Egypt where the neutral wire is grounded. The ground wire is not separated from the neutral wire. A wall outlet has two holes only (live and neutral), The third whole (ground) does not exist.

According to this question, I can NOT use neutral wire as a ground:

Why don't we use neutral wire for to ground devices and earth wire for closing the circuit?

So, How can I protect myself from the weak electrical shocks that happens when I touch the metal case of an electric device? Such as: The metal case of a personal computer or a washing machine.

I have one more question, What makes the shock too weak? I accidentally touched the live wire before and it was horrible.

If the live wire touches the metal case and then I touched the metal case, What makes the shock weaker? And If the live wire does not touche the metal case, What is the supply of the metal case? What causes the weak shock?

Thank you very much,

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    \$\begingroup\$ Is the earth wire connected to anything or just left unconnected? \$\endgroup\$ – Transistor Jul 28 '16 at 22:50
  • \$\begingroup\$ You write: "I live in Egypt where the neutral wire is grounded." and then you go on to write: "According to this question, I can NOT use neutral wire as a ground:", which confuses me since, if your neutral wire is grounded, and you've only got two terminal outlets, how is it possible to unground it? \$\endgroup\$ – EM Fields Jul 28 '16 at 22:53
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    \$\begingroup\$ @EMFields I think the OP is referring to a system where the neutral is connected to ground at the panel, but shouldn't be used for protective earth purposes. (Since there's so much potential (sorry for the pun) for the outlet to be wired backwards for example.) \$\endgroup\$ – John D Jul 28 '16 at 23:20
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    \$\begingroup\$ +1 For actually writing your country instead of handwaving it in some misguided pretense of trying to make the question "generic". It annoys me so much that I had to write a long rant on my profile page. \$\endgroup\$ – pipe Jul 29 '16 at 4:06
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    \$\begingroup\$ Some places in the UK are similar, we call this TN-C-S (see this PDF for info). Individual outlets still have their own earth. \$\endgroup\$ – David Jul 29 '16 at 6:11
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Usually the tingle you feel when touching an ungrounded case of a device is due to a capacitor (called a Y-cap, for EMI reduction) from the line to the case. This is a special safety-rated capacitor which will not allow a dangerous amount of current to leak onto the case. Nevertheless, the case is intended to be grounded so that you don't feel the tingle. You could connect the case to a grounding rod or maybe a cold water pipe.

For safety in the case of a live wire contacting an ungrounded case you could replace your outlets with ground fault interrupter type outlets. Then if you come between line (hot case) and some external ground you would be protected.

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Using a very nice decription from user @David: enter image description here

Neutral and earth are connected together, but in main cabinet side. The Neutral an Earth may be splitted from PEN just once. Then you got three wires, you need to change the entire installation.
In case the PEN wire braaks, there is still dangerous, therefore an earthing rod is needed. In the depiction is named additional source electrode. For further more safety a GFCI can be installed at point where the circuit is splitted with dots in depiction.
What you may not do, is the link you added. You may not connect neutral to earth in the connecting plug of appliance. Also the used terminology is incorrect:

I can NOT use neutral wire as a ground.

Rather, the neutral is splitted from earth (therofore you already have the earth) and not viceversa.

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    \$\begingroup\$ Using an earthing rod may be difficult in Egypt. In a dry area, the earth resistance will be high and the current caused by a short between live and earthing rod may be to low to break the fuse. \$\endgroup\$ – Uwe Jul 29 '16 at 7:53
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Egypt's electrical wiring regulations conform with IEC standards.
It is likely that what you are describing is what is typically done and not what is required to be done. ie it is likely that the installation is technically illegal. This does not mean that anyone in authority cares enough to do anything about it.

This document International electrical standards & regulations shows wiring standards applicable worldwide. On page 2 it shows Egypt as using IEC standards. Sockets are meant to be to the IEC German standard - page 16 - two pin no polarised with side wiping earth contact.

They say

  • GENERAL CIRCUITS These circuits supply both lighting points and socket outlets. The rating of the protective device is usually 16 A. There is no limitation of the number of outlets on a circuit. This limit is calculated according to expected/ probable use of the circuit. Socket outlets are generally of the 2P+E type “German". These plugs are non polarized. All German socket outlets are earthed. In general, the protective conductor is distributed throughout all circuits. For class II devices < 2.5 A, the Euro-plug is used. The wire cross-section of the fixed installed cables is normally 1.5mm² (protected by a 16 A Circuit Breaker).

&

  • EARTHING Earthing is local, usually through a foundation earthing arrangement. All metallic services shall be bonded (gas and water pipe, heating, waste systems, etc.) with a 10 mm2. In bathrooms the local equipotential bonding could have a cross sectional area of 4 mm2. Neutral is re-earthed in the control panel. A protective conductor is distributed to all socket outlets.

Related:

IEC membership

Electrical outlets

World electricity standards

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As JohnD said - a GFI / ELCB (ground fault interupter / earth leak circuit breaker may disconnect the circuit when you feel shocks (depending on how much leakage is present, but with the system you describe this could be a major inconvenience.


I'm not suggesting that the following is sensible or practical or even safe - but it is a system that SHOULD work, but which is non standard and may violate local regulatory standards:

Provide a local ground with waterpipe or similar.

  • This MAY exist already and MAY already be connected to neutral at your switch board. @Alephzero noted that connection to a "waterpipe" at random locations in a residence may be both dangerous - and also illegal in some countries. I agree that this is unwise. What I intended to convey is that the point where a main metal water-pipe for a home enters the ground is usually a good point for either an earth rod and/or for connection to the metal water-pipe. In some regulatory systems it is required that a suitably designed ground system be established AND that this is bonded to the water pipe at the point of entry to the ground (soil). This ensures that the ground-connection is a good one (by design) and that the formal and water-pipe ground connections do not develop a potential difference during a major fault, due to one or other having a lower resistance to true ground.

Provide 3 pin appliance sockets with ground connection.

Extend ground as above to socket ground.

Fit appliance with 3 pin plug and cord and connect body to ground wire.

Safe?: Probably but not certainly. IF your local system happens to provide high voltage to the body of an appliance, connecting ground may or may not be a 'good idea'.

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Regulations and practices in NZ as an example:

Here is the related NZ code of practice for earthing. It is essentially certain that Egypt has equivalent standards documents available.

NZECP:25 1995 NEW ZEALAND ELECTRICAL CODE OF PRACTICE for EARTHING AND EQUIPOTENTIAL BONDING of LOW VOLTAGE ELECTRICAL INSTALLATIONS

NZ electrical safety regulations and as DF here
Older

Related:

Wikipedia Earthing Systems

Here is a worthwhile 76 page pdf from AVO on ground resistance testing
Introductory page PDF A practical guide to Earth Resistance Testing

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    \$\begingroup\$ "Provide a local ground with waterpipe or similar." That is bad advice. One day, an electrical fault will connect the live side of the mains supply to your water pipe, which for some reason was never actually connected to earth even though you thought it was (Teflon plumbing tape used for sealing joints is a pretty good electrical insulator). If somebody then touches a metal tap with wet hands, they might not survive the experience. Using water or gas pipes as an electrical earth is illegal in the UK. \$\endgroup\$ – alephzero Jul 29 '16 at 4:38
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    \$\begingroup\$ @alephzero (1) Note that I specifically said: " I'm not suggesting that the following is sensible or practical or even safe ... is non standard and may violate local regulatory standards...". The main point was to show how much effort is involved in providing a ground system & 3 pin socket - ground, connection, new socket, new cable, connection in appliance. ... \$\endgroup\$ – Russell McMahon Jul 29 '16 at 10:09
  • \$\begingroup\$ @alephzero ... (2) I agree with you that the "ground" in such a system MUST be GROUND. When I said 'local ground' I meant one which was connected to true ground. I apparently should have made that clearer. As this was a concept (unsafe/illegal/impractical ... works) I did not go into detail about how the ground should be made. Your concern was worth noting ! :-) \$\endgroup\$ – Russell McMahon Jul 29 '16 at 10:10
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So, How can I protect myself from the weak electrical shocks that happens when I touch the metal case of an electric device? Such as: The metal case of a personal computer or a washing machine.

Start with an isolation transformer so that the "new" neutral and live are isolated. Connect the new neutral to earth at one point (distribution point or "new" fuse board) and wire this point also to a very solid gounding rod. Next use RCDs (GFCI in the US) for your power circuits.

Yes it's complicated but you asked!

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