We use 110-0-110 for residential installations where you get 220 between the two lives and 110 between each live and neutral.

Does Europe use something similar in residential installs? Something like 220-0-220?

Is this a mono-phase distribution or is it two-phase?

Thanks.

Sven,
Technically the 120/240V service to a American home is only single-phase, because the transformer has only a single-phase input, not three phases. The primary may be connected between phase and neutral or between two phases of the high-voltage lines, but because it is only a single primary winding it is only a single-phase transformer.

I'm not aware of anywhere on this side of the Big Pond using a 220/440V single-phase 3-wire AC system. We used to have 3-wire DC in Britain, the nominal levels being from 200/400 to 250/500V. I believe that such DC systems are still used in parts of India.

NO, Sven, NO! There have been newer-ending threads in some newsgroups on this issue.

My attempt to prevent open warfare:

It should not/can not be referred to as just "two-phase". Two-phase means a system with 90° between the phases. You then need four wires plus earth. The phase-phase voltage is then sqrt(2) of the phase-neutral voltage, not sqrt(3) as with three phase.

Some people will then argue that any phase angle, be it 60°, 90°, 120° or 180°, between two wires and neutral is per definition two-phase. I agree only under condition that you specify the phase angle if this differs from 90°. Thus the 110-0-110V could be called "180° two phase". Two phases plus neutral from a three phase system would then become "120° two phase".

The other group of people will argue that the 110-0-110 is single-phase since it comes from a single transformer. Then the first group will say that single phase means two wires. In my opinion, the term "center-tapped single phase" should be used to describe this system. "Single phase" used alone means two wires. You could call it an Edison system, but then it sounds like a DC system. (Note: You can get three phase from two transformers in open delta configuration. Hence, number of transformers and number of phases need not correspond)

The second group call a service made up of two phases and neutral from a three phase system "network service". I dislike this non-descriptive name, and would prefer to use "120° two phase".

(I wonder if I have added water or gasoline to the fire...)

Yes, I think 230-0-230V is used in a few places, e.g. Australia. (It's on the homepage of some Australian power company)

[This message has been edited by C-H (edited 11-14-2002).]

[This message has been edited by C-H (edited 11-16-2002).]

I think there was a thread in the general area some months ago about whether the term "Edison" should be applied to the AC 3-wire system.

I'm sure that Edison himself would have hated his name being associated with an AC distribution system.

Sven
I now have a more precise answer. Yes, 230-0-230V is used rather extensively in rural areas in developing countries. Also developed countries that were late in bringing electricity to farms, e.g. Australia and New Zealand, have used it.

Today the Single Wire Earth Return and the American style single phase + neutral has become popular for rural areas, using 10-25kV primary and 230-0-230V as secondary. I think the 120V system is a dying breed, as the cost of the LV distribution is higher than for 230V.

[This message has been edited by C-H (edited 02-04-2003).]

C-H,
Good point, mate.
The SWER system over here uses 6600V and 11kV
to supply a transformer at 230-0-230V.
Just ask any Helicopter Pilot over here what they think of the SWER system, at least with a pair of lines, you can see at least one of them wires.
I caught one going throgh a valley one day, no markers, nothing, lost one rotor, 2nd
Emergency landing I've done, all passengers shaken, but unhurt!.

That's one problem I would never have thought of. Glad you made it! A helicopter with a lost rotor must be nearly impossible to control.

How is the wire supposed to be marked?