ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades the 'electricaly safest' country?

Joe,
No way,the MEN(Multiple-Earthed Neutral)system we use over here, by it's virtue encourages very high Fault currents to flow, not only in the installation where there is a fault, but also, next door as well, if the installation Earthing in the faulty one is damaged, this often goes un-noticed, until the Neutral-Earth busbars are seperated for testing purposes.

Not that I want to stick up for my country, but in my eyes, after having read your stories, I really feel more and more that Belgium has the safest standard and better way of working. (no ring circuits, nice deep boxes in the walls, RCD's and MCB's, wires always in conduits, etc...)

Well, concerning codes there's not that much difference between Belgium and Austria. Unsupported cables are unknown (at least for electricians), even in attic spaces cables are always secured. 2nd: Nobody runs 1st or 2nd floor wires in the attic above! High quality work has a ring shaped conduit running around the room in the top 30cm of the walls, with j-boxes above the horizontal runs, light fixture wires are run in the concrete ceiling/ between the joists (conduit resting on the lathes, only secured by the fact it's embedded in plaster on both ends)/above drywall, ect. Really poor wiring (sometimes called "modern") has just cable trays in the ceiling, with 1 or 2 j-boxes per room accessible through trap doors. I really hate that, makes it hard to trace runs, and grants for lots of fishing, luckily I never saw that used in residential work). Any surface runs are always stapled (with plastic staples). Any new work has to be grounded and is usually RCD-protected (One for the whole house/appartment, but split arrangements are easier to do as there's no neutral bus, all neutrals are fused on 1ph systems). Grounding a receptacle by a jumper from the neutral to the ground terminal as not allowed here (but is in Germany for old work).
Old panels were usually Diazed fuses mounted on a metal frame, which was screwed on porcelaine distance blocks. Meter screwed to a wooden board. Smaller systems had the neutrals on top and the hots at the bottom of a 2-fuse row, larger systems had all phases to the left and all neutrals to the right. Surface mount light switches were mounted on flush wooden pattresses (instead of anchors), and were on an asbestos base if mounted on wood. This anchoring method was used well into the 60ies, sometimes it is still used for very soft and weak walls where you can't drill a decent hole. Wires are usually in conduit, sometimes just buried in plaster. Today NM is commonly buried in plaster (caught in the 50ies, back then a flat, zip-cord like NM, much later round style).

I would just like to point out that the type of cabling used in UK and Ireland is particularly tough stuff. I've seen French domestic cabling and it's a lot less heavily sheilded. I think perhaps this explains the lack of conduits.

It's a very heavy grey colour cable usually.

On the point of the MEN system (also known as PME in Britain/Ireland, and otherwsie identified as TN-C-S), what are everybody's feelings on the relative safety merits of each earthing arrangement?

In the U.K. we have a mixture of TN-S, TN-C-S, and TT systems. Although TN-C-S and TT are both used in Europe, it does seem as though many countries there have a definite liking for TT.

By contrast, TT isn't used at all in America (and in fact TT would be prohibited by the NEC).

Judging by the posts I read in this forum & the US forum, none of us have the safest system.

Like Joe, I also thought that New Zealand may have the edge due to enforcement of regs., use of RCD's, and until recently the prohibition of DIY electrical installations.

I believe that when correctly installed the UK system is very safe, as I guess are the systems of most developed countries.
However I would like to see some ammendments to UK regs & practices to improve safety, as follows:
1) Mandatory RCD protection for all general purpose sockets and certain other circuits, eg. electric shower, bathroom lighting.
2) Prohibiting the use of rewirable fuses. (Most other countries have already done this.)
3) Use of safety BC lampholders that only energize the pins when a bulb is inserted.
4) Change of specification for the general purpose BS6004 twin & earth sheathed cables, requiring: Insulated earth (CPC/ground) wire of same cross section as the L&N, preferably stranded. Thicker outer sheathing similar to Australian standard TPS cable, to provide improved resistance to mechanical damage.
5) Require an electrical safety certificate (Periodic Inspection Report) by a qualified electrician for all homes over 20 years old when they are sold. (Some mortgage lenders in this area require this now as a condition of mortgage.)

Re PME/MEN/TNC-S earthing system.
This seems to be a efficient safe method of earthing in the UK.
I suspect this is due to the fact that unlike many countries, most of our final distribution cables are run underground using concentric cables, which reduces the possibility of an open neutral. When PME earthing is used on overhead supplies in this area, the PoCo runs the final section from the last pole to the building underground in concentric cable with an earth electrode at the pole. Earth electrodes appear to be put in the ground everywhere the PoCo make underground cable joints near the consumers' premises.
The PME link in all UK installations is before the meter, unlike Australia, NZ & US. This reduces the possibility of a bad neutral connection in the installation main switchgear causing earthed metal work to rise to mains potential. In the UK we have fairly stringent bonding requirements for metallic service pipes of water, gas, heating etc. in PME installations.
PME earthing is not permitted in the UK for some types of installation, these are:
Building sites, caravan parks, petrol stations, farms etc.
New electricity supply regs. may require additional earth electrodes in certain circumstances.

Thought provoking thread you've started here Steve!

I guess it's easy to look at small, individual items to compare safety, but it's much harder to decide which system is safer/safest when looking at the whole picture.

David,
I have nothing against the expansion of GFI/RCD protection, but I would add a caveat to the way in which it is applied in the U.K.

We already commonly have whole-house RCD protection where TT earthing is employed, and split-bus RCD protection on some consumer units on TN-S and PME systems.

If we are going to require RCD protection for certain circuits on all systems, I would much rather see a move toward individual branch RCDs. I know it's a bit of a Catch-22 situation regarding the use/price of combined RCD/MCBs at the moment, but I think it would much better than the present arrangements.

Hear hear! These things have been deprecated (to use one of the IEE's favorite words!) for decades. The only mystery to me on these things is why they remained so popular for so long. I don't know of any manufacturer still making rewireable carriers except for Wylex with their "Standard Range." Full marks to them for continuing to make parts which will still interchange with a 40+ year old panel, and I have a particular liking for the Wylex Standard panels/fittings, but I think it's time that the rewireables were deleted.

Re PME and overhead lines, isn't it curious that when PME was being installed in the 1930s it was used almost exclusively in rural areas where at that time just about all distribution was overhead?

David,
I certainly hear you there, on the prohibition of Rewirable fuses.
They simply do not have the ability to interrupt the high PSC currents, and normally create a fire hazard more than anything, if a decent short circuit occurs.
I recently replaced a switch-board that was full of these fuse carriers, with it being a 3 Phase board and the fuses fitted side by side(Red, Yellow,Blue fashion), one fuse blew
and the whole board exploded, through flash- over, between the phases.
It's all MCB protected now, damn them porcelain fuses!.

well thank you Paul....some comparisson is always insightful.....would you know if a MEN , or other grounding system has ever been posted?

I've looked in the Technical ref area

The Main-Earth-Neutral system that Trumpy talked about is equivalent to British PME. It's diagram #2 in the U.K. Power thread.

Nick revised the CAD drawings a few weeks ago to add the appropriate TN and TT designations which I didn't include on the originals.

Basically, MEN/PME is the same as standard American practice where the neutral is bonded to ground at the service entrance, although as you can see in the diagram, the exact point of bonding varies. In the European/International coding system, a normal U.S. supply would be classified as TN-C-S.