3-phase on the continent

[SparkyTris]

Having read some previous posts, I now realise that "the continent" means several different wiring/supply regimes, However:

I have a "floating" supply such as you might find in Europe: what I mean is, neutral is not connected to earth.

Assuming that this is true for all phases (?),...

How do I get a three-phase supply to use for industrial tools etc?

We have assumed that you would need to use a big isolating transformer to keep the industrial equipment from grounding the supply.

Comments?

 

[plugwash]

can you provide more detail.

Is the supply from a generator or an electricity supplier?

how many wires come into your house and how are the appliances connected between them?

 

[Paul_C]

Hmm..... More details certainly needed. I know that a few areas in Norway use an IT supply system (isolated from earth), but as far as I'm aware everywhere else in Europe uses system with a solidly grounded neutral.

 

[IanDB]

On your other post you had quite a few replies, one of which showed the standard four wire system with neutral grounded. If you remove the earth, the whole supply floats.

If you believe you have a "floating" supply (although nobody appears to have heard of this in standard electricity supply situations) then indeed you will need an isolating transformer. Then you can take the appropriate grounding precautions on the load side.

It would help if you could give us a bit more info as to your aplication.

 

[SparkyTris]

It's purely academic; a few of us were having a discussion today about how 3-phase stuff works "on the continent", based on someone's assertion that the continental supply is ungrounded. But maybe this is fundamentally wrong?
judging by the standard european domestic plug/socket arrangement, the supply *is* balanced and ungrounded because you can put the plugs into the sockets in 2 ways. (ie, it goes in one way, and if you rotate the plug through 180d it goes in the other way)

 

[Paul_C]

Most of the plugs are reversible, but that doesn't mean that the supplies are balanced and ungrounded. Look at the old 2-pin British plugs -- Also non-polarized but used extensively in the past on grounded systems.

A contact in Belgium has told me that there are still a few areas served by old 127/220V wye systems. They are no longer feeding 127V loads, but just have all 220V outlets across two phases, so in these systems the lines are balanced (but the neutral is still grounded).

These and the Norwegian IT systems are the exceptions. The majority of European outlets have a grounded neutral and a hot line at 220/230V. It's just that once you get to the appliance side of the socket, you can't guarantee which is which.

 

[SparkyTris]

OK, that clears that up then! thanks. Where can I go to learn more about these abbreviations - Norwegian IT for example; I have also heard C-IT and similar to describe transmission systems.
Cheers

 

[SparkyTris]

No - hang on! not all right!

If the european supply is grounded, and the plugs/sockets are not polarised, then sooner or later you can plug something in and make the case live. ??

Which pin on a european plug is live? the left one or the right one?

 

[Paul_C]

If the european supply is grounded, and the plugs/sockets are not polarised, then sooner or later you can plug something in and make the case live. ??

No, because the casing is never grounded to the neutral. It is connected to the separate earthing conductor which goes to the earth contact on the plug (e.g. the side earth contacts on a Schuko plug).

Which pin on a european plug is live? the left one or the right one?

For the commonly used Schuko connectors, it could be either. As the plugs are all reversible, then there's really no point in trying to define which is which. Thus when wiring up the sockets, you connect line and neutral to whichever side you like. Ditto when wiring a Schuko plug.

Some countries do use polarized plugs, e.g. Switzerland, Denmark, France, but the polarization on these only applies when a 3-pin (grounding-type) plug is used. The 2-pin "euro" plug is still reversible. And in France, even though grounding plugs are polarized, electricians still seem to just wire line & neutral to sockets as it suits them.

On the system designations, the basic coding found in public supplies can be deciphered as follows:

First letter: Earthing arrangement of supply
T = Neutral is solidly earthed (T=terre, French for earth).
I = Isolated from earth (or earthed via a high impedance)

Second letter: Protective earthing arrangement
T = Equipment is grounded by way of a local earth rod only
N = Equipment is grounded by being connected to the neutral at some point

Subsequent letter(s): Path of protective earth
S = Protective earth path is separate from neutral path
C = Protective earth path is combined with neutral path

Thus the three common UK systems are:

TT Earth to local rod only

TN-S Earth is by a separate conductive path (usually the armor of an old underground cable) right back to the transfomer, at which point it is bonded to neutral.

TN-C-S Earth is kept entirely separate within the building circuits, but is bonded to the neutral at the supply intake and therefore shares a path with the neutral back to the transformer.

Most European systems are either TT or TN-C-S. The isolated Norwegian system is classed as IT because the protective ground is to a local rod only, but the actual supply conductors are floating.