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I've been reading for hours and still confused in regards to my situation. I'm trying to improve electrical safety in my house, especially with a growing family.

Any help would be great.

I'm in Pakistan, where electricians are basically uneducated and there are no codes or regulations.

Current situation:

  • 3 phase meter, 220V.
  • All phases go to a big breaker in the panel, then onwards to smaller individual breakers.
  • All neutral wires come into the panel, are joined together and connected with the neutral wire coming from the transformer (neutral wire is not connected to the breaker panel box in anyway).
  • Ground wires all meet up in the breaker panel and are joined together where then it is run outside and goes into the earth (again not connected to the breaker panel.) So this setup is NOT equipment grounding conductor (EGC,) if I understand correctly.

If ground is not present and I take a voltage tester screwdriver and check the metal case of the desktop case or camera NVR case, for example, I can see the tester light up. There is small leakage of current. This was the sole reason for taking ground wire to earth, tester does not light up then.

Q1. If the hot wire touches a metal case (say desktop), ground is currently only going to earth. What happens then? I am assuming that I would get shocked and breaker cannot trip as the circuit is not complete (no EGC).

Q2. My router for example, only has a 2 plug power adapter (so no ground plug.) With the tester screwdriver I see some power leakage if I touch any metal part. If the neutral wire and ground wire (that goes into the earth) are connected (at breaker panel,) will it prevent this small leakage happening in the router?

PS: I don't understand why such small power leakages occur.

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  • Can I ask "overseas" from where? Electrical practice and legislation varies a lot from country to country: which one are you in?
    – jonathanjo
    Jan 27, 2020 at 11:19
  • Sounds like a Y and not a \$\Delta\$. So you have three banks of breakers?
    – jonk
    Jan 27, 2020 at 11:45
  • Neutral is connected to earth at source (power station, transformer, generator, inverter, utility supplier) in default cases. Earth should allow connection to local grounds for better grounding as no current should flow in earth normally. Modern practice is to have residual current interrupters (GFI, earth leakage breaker) on circuits (plugs, wet appliances) that have larger risk of user coming into contact with live line under fault conditions.
    – KalleMP
    Jan 27, 2020 at 12:38
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    Pakistan's electric code can be found online in English here: pec.org.pk/downloadables/PETSAC/PETSAC.pdf. It was apparently written under collaboration with IEEE, so it's pretty familiar. Pakistan uses standard European power distribution 230V @ 50Hz.
    – Nate S.
    Jan 28, 2020 at 0:47
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    Reading up on earth leakage breaker that is available locally, that I think could easily resolve my concerns. Replace the main breaker with an earth leakage breaker. Ground is already going to earth. So if ground becomes live for some reason the earth leakage breaker should trip OR if someone just touches a live wire breaker would trip.
    – Roony
    Jan 28, 2020 at 9:25

2 Answers 2

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IEC terminology splits earthing systems can be split into two main categories*, one of which has subcategories.

In a TN system the neutral and earth conductors are connected together. There are subcategories.

  • In a TN-S system, neutral and earth are connected in exactly one place with seperate wiring for neutral and earth throughout the system.
  • In a TN-C system, neutral and earth are the same conductor.
  • In a TN-C-S system, neutral and earth are combined in some parts of the system (typically the suppliers wiring), while being kept seperate in other parts (typically the wiring within the customers property).

Of these systems, TN-S is generally regarded as the best system from a safety persepctive, but utilities don't like the cost, and it can also become problematic if there is more than one source of supply. TN-C was used historically in some places but is generally regarded as too dangerous due to the risks of broken neutrals. So, where TN systems are used, TN-C-S ends up as a common compromise, with precautions taken on the utility side to mitigate the risk of broken neutrals.

The other big category are TT systems. In a TT system, the supply neutral is connected to an earth electrode by the supplier and the customers earth is connected to an earth electrode by the customer, but the customers earthing system is not directly connected to the suppliers earthing system.

The advantage of a TT system over a TN-C-S system is that a lost neutral in the suppliers wiring will have no affect on the customers earth.

The downside of a TT system though, is that fault currents are much lower, too low to quickly and reliablly trip/blow overcurrent protection devices, indeed in many cases too low to trip them at all. So to make a TT system safe, requires the use of residual current protection. Ideally, residual current protection should be the first thing the power passes though, to minimise the chances of a fault happening in wiring before the RCD protection.

It sounds like you may have a TT system with no residual current protection, if that is the case then it's something you should really get rectified.

It may be possible to switch from a TT system to a TN-C-S system, but this should only be done with an understanding of local regulations and, if-appropriate, the approval of the local electricity supplier, it's not something that should be done willy-nilly.

So this setup is NOT equipment grounding conductor (EGC,) if I understand correctly.

"equipment grounding conductor" is an american term. If you are reading documents that use the term you are probablly reading documents that assume the american way is the "one true way".

Americans don't use TT systems and turn their noses up at them.

* There are also "IT" systems, but those are only used in specialist situations.

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I suggest that if you are really concerned about electrical safety, hire a professional to look at your electrical installation.

You going around with a tester screwdriver and seeing it light up MEANS NOTHING as these testers are very sensitive and light up at the smallest of signals. Capacitive coupling between wires is enough to make it light up. That means an unconnected wire (which is perfectly safe to touch, it is not connected to anything) running next to a live wire is already enough to make the tester light up when you test the unconnected wire.

Also nearly all power adapters and phone chargers can make that tester light up while they're perfectly safe to use. Power adapter also have some capacitive coupling to the mains which these devices need to prevent them from disturbing other devices.

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    No professionals here, i mean everyone has their own theory as to what is and isnt. I cant hire someone but I need to know what has to be done. Thanks for clearing up about the tester thing.
    – Roony
    Jan 27, 2020 at 13:00
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    First, "hire a professional" answers could be deployed on almost any answer, so they should be given very, very reluctantly otherwise they become noise. Second, OP has expressed being in a low-Code-compliance country where most work is done slapdash, meaning a competent electrician will be very hard to find domestically. Ever get a work visa for a skilled professional? Jan 27, 2020 at 18:05
  • @Harper-ReinstateMonica This question was in a different section where "Hire a professional" isn't a common answer. When I wrote the answer I did not know (and did not care either) the location and it is still irrelevant, electricity is as deadly anywhere in the world. I'm not going to answer "oh but you're in xyz, then sure messing around with mains wiring while hardly understanding the consequences is perfectly safe". I also invite you to write a better answer. Jan 27, 2020 at 18:37
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    @Bimpelrekkie Oh, quite right, I didn't spot that. Yes, on EE that's a fair comment. (although, mains questions appearing on ee.se are almost inevitably migrated here, and you should flag them for mod intervention for that treatment). Unfortunately our best option in places like Thailand or Africa is to up-educate them. Jan 27, 2020 at 20:18

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