OT: american and european el. power system

U.S. power to dwellings if often called spit-phase:
http://en.wikipedia.org/wiki/Split_phase

Many early US power plants distributed AC at 25 hz. The Niagra generating station still generates 25 hz for some large customers.

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How are they doing this? Are there still separate transmission lines going to those companies? Seems very wasteful

darrenj said:

another thing...UK uses 220v

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No we don't, we use 230v though most of us still quote the 'old' 240v that we had before Europe harmonised supply voltages.

darrenj said:

on a constuction site all power tools are 110v This i was told, way back when, was for safety resons

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110v power tools are used for safety reasons. The on site transformers are 55-0-55, centre tapped earth, that means that any 'line' to earth is only 55v, not 110, so if you are to get a shock it would only be a 55v one.

Paul

rsdoran said:

2 phase is not the correct terminology, it is single phase with a neutral..ie 2 hots and a neutral. This is accomplished by various methods.

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What is correct terminology used in USA rsdoran?

The standard European (well, at least Continental European) multi-dwelling house service is four-wire: 380V three-phase plus neutral. Form the main house panel, each apartment gets one phase and the neutral, which provides 220V. The phase load is distributed as evenly as possible; if one of the phase circuit breakers trip, one may see a building where some (about one-third of the)apartments lost the power completely and the others are just fine.

The standard American house service is so-called "Edison circuit": the secondary of the supplying transformer is a 220V winding with a tap right in the middle. The tap is usually grounded and serves as neutral. All three wires are brought into the house panel, easily providing two voltages: 110V for general-purpose appliances and 220V for bigger stuff (large air-conditioners, elecric stoves and such).

I am not aware of any advantages or disadvantages of each system: both seem to work well. The longtime tradition and habit assure us that each system is here to stay.

The standard European (well, at least Continental European) multi-dwelling house service is four-wire: 380V three-phase plus neutral. Form the main house panel, each apartment gets one phase and the neutral, which provides 220V.

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As Paul has just told you, the standard within the EU is 230V, or 400V three phase. Previously, the UK was 415/240, and many continental European countries were 380/220. It's true that harmonisation was achieved more by changing the tolerance bands than the actual voltage, so what you measure may vary.

AutomaticLeigh said:

It's true that harmonisation was achieved more by changing the tolerance bands than the actual voltage, so what you measure may vary.

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I know Being a somewhat close to an old-timer, I am sticking to 380V athough I am aware it could be 400V or even 415V on the transformer secondary. To me, the confusing mix of 240, 230 and 220 represent the same voltage rating. Which I used to call "220V".

The machines I work with work equally well in 220V and older 208V plants, thanks to modern power supplies and servos.

LadderLogic said:

The standard European (well, at least Continental European) multi-dwelling house service is four-wire: 380V three-phase plus neutral.

...The longtime tradition and habit assure us that each system is here to stay.

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Do most europen single dwelling homes have three phase service?
In most places in the US (except rural areas) three phase service usually availalbe - you just pay a lot more for it.

I agree, each system is here to stay. US/European harmonization would be practically impossible.

TWControls said:

Many early US power plants distributed AC at 25 hz. The Niagra generating station still generates 25 hz for some large customers.

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How are they doing this? Are there still separate transmission lines going to those companies? Seems very wasteful

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I googled it and came up with a few brief history hits.

Up through 2001 the Rankine generating station at Niagra falls generated 75 megawatts of 25 hz electicity. Today the Adam Beck generating station produces 25 hz electricty with three generators.

I agree that is seems wasteful, but if it wasn't profitable they wouldn't do it. My guess is that there are a few customers in the area (remember it is heavily industrialized) who are still requesting the 25 hz service, though I have no idea who they might be. At 75 megawatts capacity I would guess its only a handfull of large customers.

In the late 40s and early 50s the 25 cycle power generators switched most of their systems to 60hz - with the power companies changing motors in millions of appliances.

The proper term for our household service is 3-wire single phase or split phase.

The systems at Niagara Falls provide two-phase power which has advantages for motor starting, I assume these are the same ones Alaric mentioned. Two phase is a system with the phases at 90 degrees.

I did find out that AEG in Germany was the first to build a generating facility and according to the story they did use 50hz because it fit into the metric system, since AEG dominated the field the rest followed this standard.

The metric system has been around for a long time, it was officially adopted by 17 states(countries) in May, 1875, today 95% of the world use it....guess who the 5% are that do not.

If they chose it to fit the metric system then why not choose 100 hz?

All I can state is what I have read, looking for something more in depth on the subject. There are always stories just like the one about Tesla and flickering but most of the books state he did "precise" calculations to come up with 60HZ. The 50hz choice because of metric makes as much sense as asking people about flickering lights.

For many years, up until about 1970 if I remember right, the Brooklyn IRT subway still ran on 25 or 30 Htz that they produced in their own power plant, using a pair of BIG Corlis steam engines.

I believe that at least one of these units is now a Pratt's steam museum.

Alaric said:

Do most europen single dwelling homes have three phase service?
In most places in the US (except rural areas) three phase service usually availalbe - you just pay a lot more for it.

I agree, each system is here to stay. US/European harmonization would be practically impossible.

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Most Uk ( i assume this would be the same for european) have a single phase 230vac 50Hz supply and not 3 phase.

You can have a three phase service fitted and some larger properties (mansion size) have this as standard but it costs more....

Standard UK is now 230 / 400V ac

Most Uk ( i assume this would be the same for european) have a single phase 230vac 50Hz supply and not 3 phase.

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Dave,

How is the grounding done in residential wiring in the UK? You say that the system voltage is "230/400 VAC". Does this mean that (for each home or apartment) there is somewhere a 3-phase transformer (perhaps feeding other residences) that has 400 volts phase-to-phase and 230 volts phase-to-neutral? Do the transformers have "wye" secondaries, with a grounded neutral?

For most homes in the US, the utility service transformer is a single-phase 2400 primary to 240 volts secondary, with a split secondary phase, with the center point grounded to earth.

The US electric utility companies buy raw generated power in 3-phase units, but most residential customers use single-phase power. To make this work, the local electric company has to run residential wiring in a series of triple circuits, with each trio of circuits (Phases A, B, & C) feeding roughly the same number of homes or businesses. When one phase becomes loaded much more heavily than the other two, then the voltage levels may go out-of-range.