News:

"The phone is a remarkably complex, simple device,
and very rarely ever needs repairs, once you fix them." - Dan/Panther

Main Menu

Question for the UK folks about AC power

Started by Phonesrfun, August 31, 2009, 01:45:54 AM

Previous topic - Next topic

Phonesrfun

In the US, power is brought into most houses from the street as 220 volts between the two "hot" leads with 110 volts between each leg and ground.  Major appliances like electric ranges, dryers, hot water heaters, built-in air conditioners and the like are run off 220.  Other than that, the house is generally equally divided between each leg and ground to get 110 volts from the power outlets.

In the UK, and other European countries where 220 volts is the standard for house current, I am wondering if the 220 volts has any reference to ground or if it is isolated from ground?

-Bill G

Stephen Furley

#1
Quote from: Phonesrfun on August 31, 2009, 01:45:54 AM

In the UK, and other European countries where 220 volts is the standard for house current, I am wondering if the 220 volts has any reference to ground or if it is isolated from ground?
Bill, there are many differences between the electrical systems in the US and Europe.

You're not quite right about 220V; the situation used to be that Britain, and I think the Irish Republic, was 240V, and the rest of Europe was on 220V.  As part of the European harmonisation thing this has now been changed to a nominal value of 230V throughout Europe.  Nothing has actually changed as far as the supply is concerned, here it used to be 240 +/- 6% and this was changed to 230 +10 -6 %.  It was due to change again to 230 +/- 10%, but I'm not sure if this ever happened.  Similar changes to the tolerances in the rest of Europe were made, so that no change to the actual supply was necessary, but equipment makers generally made things to work on any Voltage within this range.  The main exception being incandescent light bulbs where the difference would result in a considerable change in life.  National standardisation on 240V only happened in fairly recent times; I can just remember being converted from 200V, in 1960 I think it was.  Odd frequencies, e.g. 40 Hz, and d.c. still survived in a few places until after the War (the one that ended in 1945).

Anyway, to answer your question, yes, there is a reference to ground, or earth as we would call it.  What we actually have is a 230/400V star (wye) three phase system.  All three phases are run down almost all streets, including purely residential ones.  Houses are normally supplied with one phase and neutral, with each phase being used in turn, so that if you are on on the first phase, then your neighbour on one side will be on the second, and that on the other will be on the third.  Few homes have a three phase supply, but you can get one if you want it, you would have to pay the cost of the installation, but it would generally only have to be brought in from the street just outside your house.  Since most of our supply cables are underground, except in rural areas, this would probably mean digging to run the new cable in.  In some cases all three phases are brought into the house, but only one of them is taken to the meter and beyond.  If you need more than a certain size of service, I think it's 100A in the UK, then you have to have three phase.  So, if you have single phase then its 230V to earth.  The earth wire may never be used as a normal return path, everything must be connected live to neutral.  Most non-residential buildings, except for very small shops, would get all three phases.  Unless you're running something very large, like a steelworks, this is what you would get, we don't have higher Voltages like your 480/277V or 340/600V systems.

There is one major exception to this, in the UK only, not the rest of Europe, most portable power tools, except those used in the home, have to be 110V.  This is actually a 55-0-55V centre-tapped system, basically a half-Voltage version of what you have over there, but equipment is only allowed to be connected across the full 110V, it cannot be connected between one side and earth.  This is supplied by local double-wound transformers, usually of 3kVA rating for intermittent use, which are yellow cube shaped boxes, of about 20cm, 8 inches.  These can be run from our standard 13A sockets, and usually have two 16A 110V yellow sockets which I still call BS 4343, though they have a new international number now which I can't remember.  Ther're the same as the 'pin and sleeve' connectors that you have over there, except that in Europe they're rated at 16, 32, 63 and 125A, while over there I think they're 20, 30, 50 and 100A.

Standard frequency throughout Europe is 50 Hz.

Except for isolated buildings, like farms in remote areas, we don't have the small pole mounted transformers that you have.  We have substations with large transformers which typically feed several streets.  Normal distribution Voltages are 6.6, 11, 22, 33 and 66 kV.  11 and 33 kV are the only common ones now, 6.6 kV is largely obsolete, though still in use in some places.  22kv is quite rare here, though it's widely used on the mainland.  The London Underground has a fair number of 22 kV substations, but they're unusual in the public supply.  The substation at the college where I work is fed from a 22/6.6 kV substation, but that is unusual these days, and would not be used for a new installation.  The whole area is heavily overloaded, and work is now taking place to upgrade the supply.

Transmission Voltages are 132, 275 and 400 kV, with 132 kV being largely obsolete.  There's a d.c. cable between England and France, which I think is 200 kV.

The standard for electric railways is 25 kV, industrial frequency, as it is in most of the world now. We still have 750V d.c. third rail in a couple of areas, but no low frequency systems; the last of these was phased out long ago, one in 1929, and the other some time in the '50s I think.

Phonesrfun

#2
Thanks, Stephen.  Quite a bit of information to digest.  We also have three phase power that runs to most places, including residential and rural.  In residential areas, the power company uses this to balance the load.  While I suppose a residential customer could request and pay for 3-phase, I don't know specifically of anyone who has this.  

Factories and businesses with large power needs do have three phase power brought in.  Even light manufacturing uses three phase 240 v power.  For instance sewing factories.  The sewing machines, although pretty light duty largely run off three phase.  Many commercial buildings use three phase power on their heating and air conditioning systems.

I think the reference to 110 volts and 220 volts is a misnomer and I frequently refer to standard power as 110 volts.  Power at my house is really about 122 volts at the socket in the wall.  So it is 120 and 240 as opposed to 110 and 220.

Here, as in England and Europe, there are tolerances in the absolute voltage provided, and most machines will handle a pretty wide variety.  I think the power companies are more anal about keeping the frequency at 60 Hz than they are at the voltages supplied.

So, in our case, the modern plug/outlet has three pins.  A "hot", a "neutral", and a "ground".  Neutral and ground are essentially at the same potential, but the code requires two separate physical wires to run to the breaker box.  I believe your plug, while quite a bit larger in physical dimensions than ours also has three pins.  Do you use the same configuration of the hot, neutral and earth?  I thought you may have answered this question, but I am just a little fuzzy about what you said when you said:

"The earth wire may never be used as a normal return path, everything must be connected live to neutral.  Most non-residential buildings, except for very small shops, would get all three phases.  Unless you're running something very large, like a steelworks, this is what you would get...."

-Bill G

Stephen Furley

#3
Quote from: Phonesrfun on August 31, 2009, 01:54:55 PM
I think the reference to 110 volts and 220 volts is a misnomer and I frequently refer to standard power as 110 volts.  Power at my house is really about 122 volts at the socket in the wall.  So it is 120 and 240 as opposed to 110 and 220.

Here, as in England and Europe, there are tolerances in the absolute voltage provided, and most machines will handle a pretty wide variety.  I think the power companies are more anal about keeping the frequency at 60 Hz than they are at the voltages supplied.

Pretty much the same here, where people talk about 220 or 230 or 240V.  The official figure is now 230, but at home I tend to get rather more, at the moment it's about 243V, while at work I've seen it as low as 217 on a bad day.

QuoteSo, in our case, the modern plug/outlet has three pins.  A "hot", a "neutral", and a "ground".  Neutral and ground are essentially at the same potential, but the code requires two separate physical wires to run to the breaker box.  I believe your plug, while quite a bit larger in physical dimensions than ours also has three pins.  Do you use the same configuration of the hot, neutral and earth?  I thought you may have answered this question, but I am just a little fuzzy about what you said when you said:

"The earth wire may never be used as a normal return path, everything must be connected live to neutral.  Most non-residential buildings, except for very small shops, would get all three phases.  Unless you're running something very large, like a steelworks, this is what you would get...."



Bill, let's look at this in a slightly different way.  Imagine that you and I each decide to take a test meter to investigate a single socket in our homes.  Your 15A Nema 5-15 socket is quite different in mechanical terms to my 13A BS 1363 one, http://en.wikipedia.org/wiki/BS_1363 , but let's just consider the electrical differences.  I would find roughly twice the Voltage that you would, and my frequency would be lower, but let's also forget about the frequency difference, as we will always be 50 Hz. and you will always be 60 Hz.  With most equipment this makes little difference.  Other than these differences we would both see pretty much the same thing, three pins, one earth (ground) which is there purely for safety purposes and should normally carry no current, one live (hot) and one neutral which form the circuit.  The neutral will be bonded to earth at some point, and should be very close to earth potential, although due to the current flowing in the neutral wire there may be a small potential difference between neutral and earth at the socket.  So, other than the difference in Voltage and frequency we're both seeing something very similar.

However, each of us is only seeing part of the story.  If you were to connect your test meter between different sockets in different rooms you would find the 120-0-120V centre-tapped system with which you're familiar.  For me to discover the whole story I would probably have to connect to sockets in three different houses, and I would find that my socket is in fact part of a 230/400V three phase  star (wye) system with the neutral connected to the star point which is earthed (grounded),

At this point each of us has the full story, at least as far as domestic installations are concerned.

Suppose the next day I take my test meter to work, and repeat the experiment; what do I find?  Exactly the same thing.  I could take it to a shop, large department store, office building, factory, shopping mall, bank, cinema, railway station etc. and in each place I would find the same thing.  In your case however, it would be different.  In a modern commercial or light industrial building you'd probably find that your 120V outlet was part of a 120/208V three phase wye system, basically a half-Voltage version of what we have, and quite different to what you have at home.  If you were to go to a large building, or heavier industrial setup you'd probably find that it's fed  at 277/480V three phase wye, with the 120V outlets fed from a local transformer.  Then again, if it was an older building it might be fed with 240V three phase delta, with one phase centre-tapped to provide the same 120-0-120 system that you have at home, with the third leg at 208V from the neutral.

While what we would each see at a single socket is very similar, apart from the Voltage and frequency, when we look at the whole picture there are important differences, and in the case of the US, there are several different complete pictures to look at.  Over here we really only have one, except for special cases like electric railways, or *very* heavy industry.

Yes, we get one or three live (hot) wires, one neutral and one earth (ground); the earth is never used to carry the normal current, and is only there for safety purposes.  We don't have anything like your 240V outlets, Nema 6-15, 6-20 etc. with two hot wires, other than the case I mentioned of 110V portable power tools on building sites, but this is not a mains supply, it's obtained from a small portable local transformer.

The 13A BS 1363 socket outlet is the only one which you'll find in the vast majority of homes today, and for many years.  The older BS 546 outlets with round pins are still allowed, but almost extinct except for stage lighting.  They came in 2, 5, 15 and 30A versions.  Two pin versions of these are no longer allowed.  Industrial socket outlets are not allowed in homes, as they are not shuttered.  There used to be many other socket types, D&S, Wylex etc. but they're now long obsolete.

Phonesrfun

Quote from: Stephen Furley on August 31, 2009, 05:24:54 PM
If you were to connect your test meter between different sockets in different rooms you would find the 120-0-120V centre-tapped system with which you're familiar. 

Yes, this I do know for a fact.  Several years ago I needed a source of 240 volts for a rented grinder I was using to smooth out a concrete floor in the basement of my house.  Using some extension cords, I was able to rig up a source of 240 volts by going around the house looking for outlets on different legs.  It worked perfectly.

You seem to know quite a bit about the subject, both from the UK perspective and the US perspective.

Thank you for all the information.

There is one thing that still puzzles me, and it is regarding the 60Hz, or the 50Hz in your case.  What I would like to find out some day is how power companies syncronize and/or create the stable frequency.  Here we have a huge nationwide power grid, which you must have also.  We have literally thousands of power sources.  Hydroelectric, coal, gas, and now wind power too.  Thousands and thousands of wind turbines, hundreds of dams; all chugging away generating power at various different levels and probably armature speeds on the individual generators.  I know power is power, but it seems to me that there must be some sort of syncronization.

How the Hell does the power company make sure everyone is exactly on frequency at the same nanosecond in time;  Otherwise to me it seems like there would be a hodgepodge of sine waves being genreated that when all blended together would effectively be DC.

That is something I have wondered about for years.

-Bill G

Stephen Furley

#5
Quote from: Phonesrfun on August 31, 2009, 06:13:58 PM
There is one thing that still puzzles me, and it is regarding the 60Hz, or the 50Hz in your case.  What I would like to find out some day is how power companies syncronize and/or create the stable frequency.  Here we have a huge nationwide power grid, which you must have also.  We have literally thousands of power sources.  Hydroelectric, coal, gas, and now wind power too.  Thousands and thousands of wind turbines, hundreds of dams; all chugging away generating power at various different levels and probably armature speeds on the individual generators.  I know power is power, but it seems to me that there must be some sort of syncronization.

How the Hell does the power company make sure everyone is exactly on frequency at the same nanosecond in time;  Otherwise to me it seems like there would be a hodgepodge of sine waves being genreated that when all blended together would effectively be DC.

That is something I have wondered about for years.

Since wind turbines don't turn at a constant speed the output from them is generally rectified to d.c. and this is used to drive a three-phase inverter which is locked to the grid in frequency and phase.

As far as conventional power stations are concerned I would guess that it's all computer controlled these days, but the traditional way to do it was with a large meter called a synchroscope connected between the alternator and the grid to which it was to be connected.  If the phase of the incoming machine was leading that of the grid then the needle would swing one way; if it was lagging the needle would swing the other way.  If the frequency was off then the needle would swing backwards and forwards as it went in and out of phase.  They would just adjust the steam slightly to get the needle as close as possible to the centre position, and then close the breakers to connect the machine to the grid.  There's another type where theneedle turms clockwise then the machine's running fast, and anti-clockwise when it's running slow; again, the aim it to get the needle steady at the top.  Scroll down this page:

http://www.nickelinthemachine.com/tag/power-station

for a picture of this type at Battersea 'A' in London, built in the '30s.

Since an alternator is basically the same thing as a synchronous motor, if the phase isn't quite correct a torque will be generated which tends to pull the machine into sync, so once it's synchronised it locks in, and stays that way.  If the machine was far out of sync when the breakers were closed then very heavy currents would flow.  You might get away with it with a very small generator, but not with a power station one.

McHeath

Holy shocker Batman!  You guys have serious power knowledge, I'm impressed.  Me, I know that if you hire a guy who knows what he's doing the rewire job will work, and if you don't you will get the breaker tripping all the time. 


Phonesrfun

I just re-wired a hot tub connection for my friend while in Seattle, then I went over to Brinybay's house to work on something a little less lethal.

The gist of my original question was whether or not power in the UK had one side grounded like it does here in the US.  From Stephen's description, it also does.  He is much more knowledgeable than I.  Heck, he also knows US stuff too, which sure impressed me!

The whole reason I was asking was from an earlier thread in one of the other forums regarding grounding when making a 130 volt DC source for returning or collecting coins from a US pay phone such as AE or WE.  Some would think that by just hooking a power source into the wall without isolation would do the trick.  This can work, but is frought with problems.   The main problem is that you absolutely need an isolated source, otherwise it can not only be a shocking experience, but also do damage to the phone line if something touches something else that it should not.

Any way, the whole discussion on the other forum piqued my curiosity, and I thought I would ask here because here there seems to be the "no questions are stupid" rules in effect.  On the other forums, you get shot down in a hurry for asking seemingly dumb questions.  Something I have experienced often.

By the way, I am experiencing the jumping text box issue again, even as I type this.  Grrrr.
-Bill G

Phonesrfun

Stephen:

I love those old meters!  The telecommunications museum in Seattle has a couple like that, although not quite so large that are associates with the power plant for their 1920's vintage panel office.

-Bill G

dsk

Europe isn't always fully harmonized.

Here in Norway, the trains runs on 20kV 16 2/3 Hz

Most older hoses has a 230V supply from an insulated transformer delivering 3 phase 230V  and having about 130V to ground. (Until the first error)  Approx like the US 208 V  (I believe this system was out from 1948 in UK)

The Hz problematics makes most 400 3 phase motors running well on US 480V :)

On the other hand we split the 50 Hz and uses 25Hz ringers on our telephones, US divides their 60 Hz on 3.

The trams uses 750V DC in Oslo, no exact standard.

You may find 3 phase 230 or 230/400 in almost all farms here, and at many residential buildings.

Actually we have a cabin with 3*230V  very suitable for our well 82 meters deep.

The grid may be weaker here, and water storage heaters are common, instant water heaters are extremely rare.
We want a constant power consumption, major domestic heating is electric.

dsk

HobieSport

#10
I find this thread fascinating although way beyond my meager comprehension, but must say that I am somewhat thankful of the American standards. At least I know a little about American household systems. I love Europe but it has me boggled, electricity-wise.

DSK; I am surprised that instantaneous hot water heaters are not common in Norway. Is that because of a weak grid?

You mentioned your cabin. Here in my vintage trailer in California (call it my cabin) I would normally run a 240 volt circuit with 30 amps. That would run a small instant hot water heater and make my electric space heating more efficient, I guess. But that would draw too much electricity from the main house, which has a 100 amp service.

So instead I ran 20 amps at 120 volts to the trailer, and with that I run an efficient little four gallon tank water heater for quick showers and washing dishes. I am running completely on electricity, but it works, because I only use one major appliance at a time. I didn't intend to do this, but I am living "light on the land" like some idealistic environmentalist or something, but I'm just doing it because I'm cheap and lazy with Scotch-Irish-Welsh blood. ;)

-Matt

bwanna

WOW i'm impressed!  i'm a little too ADD to comprehend all this at once. :(

just want to reiterate bill's comment of "no questions are stupid" here.
i was apprehensive at first, asking some basic questions. that didn't last long, tho. everyone here is great & so willing to share information. ;D



donna

dsk

I believe the limited use of instant water heaters are because of the supply system.

e.g. The cabin is approx 1000m (yds) from the transformer, and it is a lot other consumers at the same distance.  A great load causes blinking in the net when the load are turned on/off. 

I have noticed the American systems uses a lot smaller transformers but each quite near the consumer.

dsk

McHeath

Yeah, we've always had pole mounted transformers right before the feed is dropped into our houses.  (the places I've lived I should say)  My current home also has the pole mounted transformer in front of it, and a 200 amp box on the side of the house.  Those transformers do go bad every so often, this one did about 10 years ago, and one did at my folks house in the early 80's.  Not sure what the lifespan is of them, the poles here are all marked with a date spike so that we know when they were set, the one with my transformer is dated 1973, but that can't be original as the house was built in 66'.  Some of the poles across the street have dates from the mid 50's when the tract was put in. 

The Operator

20 years ago we had a pole mounted transformer right across the street. At least once or twice a year you'd hear this tremendous BANG! followed about an hour later by a PPL truck with yellow flashing light. Often it would be in the middle of a thunderstorm but sometimes completely out of the blue. This was a rural area, so finally they installed a new shiny gray transformer and after that, no more BANG! ~The Operator
Ever get the urge to call the number on the dial card and say "Hey, I have your phone."