ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades Love it or Hate it?

David and Paul,

you might like to be informed that the IEC has moved to ban the TT system worldwide. France and some other European countries doesn't like the idea, but it might still become reality.

Another topic. I've never understood supplimental bonding in bathrooms and other places where the wiring is protected by an RCD. Sweden doesn't require it. It turns out that I'm not the only one who doesn't understand. It was discussed at an international meeting some time ago, and might be dropped.

[This message has been edited by C-H (edited 07-22-2003).]

Here it is also required supplemental bonding in all bathrooms. The reason given is because of the eventual impendance of the earth wire and therefore can cause a difference of potential. But , personaly I find it far fetched and I don't buy it.

A different reason could be that Belgium has interests in selling as much copper (cables) as possible, since it still owns copper mines in a formal colonies of Congo or some other place. I heard this theory from a fellow Electrician. That might also be the reason why they require according to our code to use 4mm2 for washing machines!

Haha! A copper conspiracy.

Seriously, there is talk of creating a EN IEC 60364.

Warning, speculation from this point onwards

As I understand it, it would then replace the current national wiring regs. E.g. BS 7671 would be replaced with BS EN 60364.

This means that they'll have to go over the national codes and compare them. If there is no reason to require something, it should be removed from the wiring regs, and if there is reason to require something a rule should be added.

This doesn't rule out national specialities like ring mains: The BSI can add an extra chapter with rules specific for Britain. The point is that you know that the all difference between countries is to be found in the extra chapter(s).

This should make it easier for electricans working in other EU countries. You'd probably still need a license for each country, but the process to get an additional country could be greatly simplified. You only need to learn the special chapters and you previous experience in any member country counts.

[This message has been edited by C-H (edited 09-26-2003).]

We recently had a very strange situation here in Ireland where the ESB had a contractor working on upgrading the rural networks in the west of the country to 20KV and adding various more modern features to make the network more fault tollerant / resliant etc.

Anyway, the contractor had hired south african electricians who the ESB considered to be insufficiently qualified despite their insistance that they'd worked on such systems before and had the appropriate qualifications. (This was found during some ESB site inspection)

ESB came down like a ton of bricks on the issue, closed the site pending an investigation etc and the guys were left in Ireland with no work, no accomodation, no money etc etc.. was all over the TV news.

It seemed to be down to red tape, but I'm not 100% sure. They seemed quite concerned that these guys were working on stuff that wasn't the same as South African gear that they were familar with without appropriate certification and training.

There may well have been serious consequences for the contractor involved too.

It just underlines the need for some kind of international certification / standards etc for electricians as they are more mobile than ever thesedays.

[This message has been edited by djk (edited 07-22-2003).]

I hadn't heard about that IEC proposal to ban TT, but naturally it would get my vote. They do seem to like TT a lot in some areas of Europe though, so I imagine there will be as much opposition to that proposal there as there would be in Britain if it were proposed to ban the ring circuit or require Schuko outlets as standard.

Interesting on the HV lines in Ireland. I can see the point about not being trained sufficiently, but any decent electrician who has a thorough understanding of the basics should not have too much trouble adapting to different conditions.

Just look at the variations in HV techniques around the world: Delta vs. wye, solidly grounded neutral vs. floating or impedance-grounded, etc.

Question about TT systems—are ground detectors used with them? There are two good reasons for ground detection. One is that if a ground occurs somewhere in a normally ungrounded system, nothing happens overcurrent-wise, but then the second fault will likely cause two overcurrent devices to operate simultaneously.

Another consideration is that without some resistive load-to-ground in the ungrounded system, the normal phase-to-ground capacitance can charge up to much greater than line-to-line voltage, and cause severe arcing damage in the insulation. In cases in the US with intentionally ungrounded systems, this has been learned though {expensive} trial-and-error lessons.

A restriction in US ungrounded systems is that phase-to-neutral loads may not be served, as would be conceivable in an ungrounded 4-wire wye system.




[This message has been edited by Bjarney (edited 07-22-2003).]

Scott,
I think you're getting mixed up with the European designations: It is the IT system which has the supply floating, and apparently is used in parts of Norway.

The TT system, however, still has the neutral on the wye supply grounded. In fact in the U.K. the electricity supply regulations have required all LV public supplies to have one pole solidly grounded since about 1930.

Where TT differs from American practice is that the main ground busbar at the house has no bond to the neutral -- It is grounded solely to a local rod.

U.K. Supply Systems -- Diagram #3.


[This message has been edited by pauluk (edited 07-23-2003).]

Djk,

Something similar happened in Sweden (Gothenburg) with British electricians the other year.

[This message has been edited by C-H (edited 07-23-2003).]

Thanks for the update/reminder, paul. I'd forgotten scott35's illustrations were two mouseclicks away.

And to answer the question that Bjarney thought he asked: Yes, earth fault detection is used with IT systems for the reasons you list, at least in Norway. The abscence of neutral in this case means that you simply cannot have phase to neutral loads.

[This message has been edited by C-H (edited 07-23-2003).]