Here's something which is a rare sight in England. I found this pole-mounted xfmr on a back-road a few miles from my home. Anyone going to have a guess at what makes this so unusual?




{ Edited only because images moved to a different location - Paul }


[This message has been edited by pauluk (edited 06-09-2003).]

I’ve heard there’s a big problem with cars getting smuggled out of North America, but I didn’t know it had spread to poletop transformers, too. ;-)

Paul — Just how rural do you have to be to only rate a 2-wire span down the road?

ESB Ireland uses LOADS of those. They're all over the place once you get outside built up areas.

They use them to serve 1/2/3 homes max from 10KV distribution lines over here. They're a little squarer than that though.

Most farm houses are supplied like that here.
Pole top transformer supplying either single phase 220V or 3 phase 380 V for farm buildings etc.

Not used in the UK system normally?

I've never seen single phase distribution like that though. Even local low voltage final stage distribution is 380V each property just picks off 1 phase and neutral (domestic @ 220V) or all 3 phases & N commercial.

Sometimes there are very small ground mounted xFormers used for distribution in built up areas, kerb side box style. Rural areas are absolutely full of big/small green pole top xformers though, just like in the USA (Except green, it is ireland afterall!)

You occasionally also see larger pole top xformers mounted on a kinda wooden frame between two large wooden poles. Think they may feed a village / large farm complex.

Actually was just informed that 1-phase supply at up to 10KV isn't too unsual in rural areas to make it usable over long distances. In areas that have no small industry type customers and in older systems 3-phase was considered unnecessary and extra cost. Most farms used 220 V single phase as do all normal individual domestic properties. Rural 3-phase is a relatively new concept especially in remote spots. It was more common to split the load over multiple 220V supplies all originating from the same xformer and phase but all going to different buildings from the pole overhead each rated between 65 and 100 amp max. So for example a heavy milking machine might have its own 65-100amp 220V supply seperate from the house / other farm equipment same with heating etc. avoided 380V but still provides the necessary power. Closer to towns and even villages you get full 3-phase supply. These are extended where supply is required to feed large farms and small industry. there are thousands of miles of single phase 10KV though.

Here's the typical ESB single house supply xformer mounted on a pole top near a house in a rural area.

Apparently Paul's point is that single-phase distribution transformers are not in wide use in the UK.

On the other hand, there has been discussion here about “ 3 x 16A” and “3 x 25A ” 400Y/230V 3ø residential electric services in Europe, which is very interesting that distribution systems and engineering practices can vary from one extreme to the other.

Just to add a little info:

In Ireland the old original single phase distribution systems are 10KV, mostly being pushed up to 20KV to give extra capacity.

One upgrade method used by US utilities is to change, for example, 12kV circuits to 20.8kV with an added neutral span and larger insulators. Delta 3ø 12kV-primary transformer banks are changed to grounded-wye, and 12kV 1ø transformers are changed from ø-ø to ø-n.

Newer padmount transformers can then be specified with a non-loadbreak primary switch to swap between 12kV delta and 20.8kV wye.

Paul,
This actually looks like a Line- Stabilisation Xformer, as it feeds on to the next set of lines, head away to the right of the pic.
It's obviously a fair way out in the country, judging by the age of the pole?.
I take it that this is not a take off Xformer?.
Your thoughts please.
This is what we call a Can type Xformer, over here.

Distribution systems here in a lot of rural areas are just reaching capacity as the demand for electricity has been rapidly increasing as farmers add more automation and householders add more gagets

I'd say 10KV systems will gradually all move to 20KV and 38KV. Moving them all over to 3-phase sounds really expensive given the sheer length in KM's of 10 and 20 KV cable systems in use in rural areas here since the 1930s. They still seem to like wooden poles though. I think the metal and concrete ones used by EDF in France look horrible in comparison.

What does the UK use for rural supplies ? I can't see much alternative to medium tension lines and local step down transformers.

O.K., what I was getting at about this being an unusual sight is not that it's a single-phase line.

It's the point allured to in Scott's first post: The cylindrical-cased xfmr and method of mounting on the pole which look very much more American than anything else you'd be likely to see here. This is certainly the only xfmr of this type I've seen in the area, and in fact I don't recall ever seeing this type in England before. The xfmr in question looks fairly new and not badly weathered as yet, so it probably hasn't been there too long. I'm wondering if the PoCo is going to start using more of these when replacements become necessary.

Here's the more usual style of single-phase xfmr that you would see on poles to feed one or two houses:


The 3-phase pole-types feeding a 4-wire 240/415V wye system for distribution to a number of houses usually look something like this:




{Edited for moved images}

[This message has been edited by pauluk (edited 06-09-2003).]

Now to some of the other points raised.

BJ,
Although it would be hard to find single-phase lines running for miles here, there are certainly quite a few short 2-wire spurs around the area. This part of Norfolk (county) consists mostly of small towns and villages, interspersed with open countryside (we're not talking anything like as open as Nebraska or Wyoming of course, but it has a fairly low density of population by English standards ).

The road I took this picture on runs about 5 miles across open fields, with just an odd house or pair of houses, church etc. dotted along the way.

Going back to the photos at the top of the thread, there is a 3-phase line running almost at right-angles across the road about 300 yards to the left from which this 2-w spur is tapped. The HV lines going off the picture to the right finish about another quarter-mile further on at a xfmr which feeds two or three houses, so this particular 1-ph spur is under a half-mile long. There are more similarly short spurs along the route feeding homes on this road and the tiny lanes off to the sides.

Trumpy,
It's a standard step-down xfmr to provide a 2-wire 240V domestic supply. The house is actually out of the shot on the opposite side of the road to the pole.

DJK,
These are standard 11kV lines which are used for local distribution throughout Britain. Power comes into this area on 33kV feeders, which is another standard distribution voltage here. (According to the local utility, there are still a few old 6600V networks in this region, but they are few and far between.)



[This message has been edited by pauluk (edited 03-19-2003).]

The numbers are interesting. Remember that WebSparky's 95-year-old transformer in Cleveland showing a 6,600/11,400V primary on its nameplate? With external bushings {connections} and jumpers, it could be served with 6.6kV with primary in delta and 11.4kV connected in wye. https://www.electrical-contractor.net/ubb/Forum4/HTML/000256.html

Paul,
In your last pic, you showed a Pole-Mounted Tank Transformer, what type of Fuses are they on the side of the pole, to the front of the pic?.
I take it that the Neutral is Earthed at the Xformer?.
What is the VA rating of one of these trannys?, just curious.

Would one of the following guesses possibly apply to the item shown in the first images?:

<OL TYPE=A>

[*]Autotransformer?,

[*]Circuit Breaker / Motorized Cut-out?,

[*]Voltage Boosting Transformer?,

[*]Series Street Lighting Regulating Transformer?,

[*]Power Factor Correcting Assemblige (Caps + Inductors)?,

[*]Space People Bringing Stuff To Earth?
</OL>

Anything sound possible?

Scott35

ESB in Ireland seems to have used the US style mountings generally. Mostly round. I'm sure they're prob. from various manufacturers though. More than likely Siemens, AEG or GE.

Have you ever seen the French distribution poles with switches accessable from the bottom of the pole to reset trips or something, not quite sure what they're used for but there's a large lever at the end of the pole.

Any ideas?

Tramway poles in Vienna have padlocked disconnect levers. I have never seen them on residential power poles though. Rural areas still have wooden poles, only HV distribution is on steel grid poles. Street lighting here in Vienna are waterproof flourescent battens with 2 tubes strung on wires between houses or on octagonal galvanized steel poles. At midnight one of the tubes is shut off. Other cities use wood or concrete lighting poles. (I think in the outskirts of Vienna they also have wooden poles, but these areas can hardly be considered to be within city limits, they look _very_ rural and even have 230/400V overhead distribution, something otherwise unknown in Vienna, downtown overhead services were removed in the early 20th century). Old overhead services were done with 4 individual wires, modern installations use quadruplex, like the US triplex OH, only with insulated neutral, but even in very rural areas they're starting to switch over to underground distribution.

In Ireland there is still plenty of overhead distribution in suburban areas that would date from the 1920's - early 1950's. Any suburbs / housing developments built after the early 1950s have underground cabling for power, phones and often cable television. The vast majority of our "closer" and nicer suburbs date from the 1920's and 30s though.

Typically you'd have 400V (380V) distribution on twisted or individual cables with a twisted pair going to each home usually to the highest point on the house i.e. the chimney top. Phone service runs in a similar configuration and cable television typically ran house-to-house at roof level.

The only thing that does make it different from most of Europe is that our suburbs are very "leafy" and tend to have large front gardens and lots of tree lined streets so most of the power lines and poles disappear, you don't really notice them. Many areas also had the services run behind the houses in lanes so there are no overhead lines on the streets.

The ESB uses a LOT of wood, all distribution lines are on wooden poles, even new installations. Much of the 110KV parts of the transmission network, including new parts are on very high wooden poles with modern pylon style insulators on the top. They're considered to look better and have less impact on the scenery than metal pylons. 220KV and 400KV lines are all on metal pylons.

Rural distribution is all on 10/20KV lines with pole mounted transformers feeding houses/farms individually. All wooden poles, very "US style".

The Cable TV networks are a little off topic but they deserve a mention.

They're generally much older than anything i've seen elsewhere. Cable hit surburban Dublin and Cork in the late 1960s and there were even small cable systems in the 1950s relaying BBC from large communal antennas that picked up broadcasts from the UK and fed them by cable when RTE was either non-exsistant or very very boring ! Many people in Dublin particuarly still call cable tv "Piped Television" or even "the relays".

When it was installed initially they just ran thick co-ax from a "head end" house to house under the facia boards just below roof level. The cable company would often give someone free cable if they'd agree to have a small amplifier fitted to boost the signal en-route. Those systems initially carried 2 Irish channels and 2/3 british channels and expanded as satellite became available and more channels went on air in the UK and IRL some even carried their own local programming. None of the channels were encrypted in Dublin and Cork adopted a US type set-top-box with analogue encryption. These boxes even came with wood paneling to match the TV sets of their era.

They've been re-wired with better co-ax to give more capacity in the 1980s and during the 1990s and 2000s they've been gradually converted to digital systems and fiber's been layed underground along streets, however the coax house-to-house network still carries all of the basic 18 to 30 channels that are available free to air and usually unencrypted, you just plug the cable into the TV (VHF band I/II/III and UHF)

I've seen a few places here where a disconnect has an operating rod and handle lower down the pole.

Underground distribution is certainly becoming more common here, and virtually all new housing estates seem to be built with all services underground now.

Even ignoring the latest projects, one really noticeable difference between an average American town and an average British town is in the amount of cabling one sees overhead. British towns seem to be lacking in overhead cables (or American towns seem to have a lot, depending upon your point of origin! ).

Scott35,
Good points you raise there (Don't think I'll vote for the last one though! ), but this appears to be just a regular distribution xfmr. It might not be completely visible in the photo, but the 11kV lines are just looped from one side of the pole to the other with the HV bushings on the xfmr connected straight across. The 240V lines leaving the pole below the HV and going off to the right are actually the service drop to a house on the opposite side of the road.

Trumpy,
Not sure of the actual rating of that xfmr above, but this one is 100kVa:

It has the same type fuses as above, but you can see them a little more clearly here;

They're a cartridge fuse, though I'm not sure of the rating.

By the way, for anyone who wasn't with us, these photos were originally posted this thread , along with some others of local distribution equipment.

On the wooden vs. metal poles argument, wood wins here on all the local 11 and 33kV lines. Metal lattice towers become the norm here for transmission at 132kV and above.

DJK,
Cable TV has a rather obscure history in the U.K. There were a few cable systems installed way back in the 1950s, mostly as communal antenna systems operating over very small areas (e.g. a single block) in towns which had poor reception. But they were rare, and generally only carried the regular free-to-air signals (which at the time meant one BBC channel and one ITA channel, with maybe BBC2 added when it started in the sixties).

It's really only in the last few years that cable TV has become more widespread, and still only in large cities. As such, the cabling has followed the modern trends, so cable TV line strung up as you see them in America, or as you describe in parts of Ireland just don't exist.

BJ,
Yes, I've been following the thread with the 95-year-old General Electric xfmr. Fascinating!

{Edited for moved images}


[This message has been edited by pauluk (edited 06-09-2003).]

Paul,

My eyes are terrible!!! Looked as if the Primary Feeder on the left side (furthest from person taking pictures) was connected as a "Common" to both the Transformer and the Secondary side!!!
I need to be more careful!!!

With that in mind, it's the oddest looking Pot I have ever seen! Strange how the HV Bushings are mounted on the Cylindrical portion of the enclosure - as opposed to mounting on the top.

Must be some advantages (arc quenching, birds being caught between phases, maybe wind stabilization / harmonic vibrations transfered to pole better???).
Must find out what's up!!!

Scott35

p.s. Would the Apparent Power rating of this Animal be around 25 KVA, or 37.5 KVA? Trying to "Scale" it to common Pot sizes in US pole mount distribution applications - falls in the 25-37.5 KVA range (as viewed by my great bionic eyes!)
Primary is 11 KV? (11,000 even, or 11,000 + some loose change ;-)...), and Secondary is 240 VAC?

Sure can find some odd Electrical Power equipment in the rural areas!

As to the Polyphase ones (the 3Ø 3Wire Transformers), have seen a bunch of those types around here! Bushings from the top and the fronts! Even remember seeing some of those fused cutouts here and there!

Scott35

I dpn't work on this side of power, so I'm not very good at eyeballing the rating of these xfmrs, and as has been mentioned in here before the variation in design parameters can make a visual "guess-timate" difficult anyway.

Yes, the primary is 11kV, secondary 240V. This xfmr is feeding one house, and residential services these days are usually 100A, so 25kVA or thereabouts would be reasonable.

I think I see what you mean about the primary/secondary cabling. It's complicated by the fact that this being a pole where each run is terminated and tensioned there are the jumpers across the pole. The jumper on one side of the primary line is supported by an insulator above the cross arm while the other jumper is run belowp it. From the angle of the picture, it could appear as though that jumper is heading toward one of the secondary lines.



[This message has been edited by pauluk (edited 03-21-2003).]

Paul:

In Dublin and Cork pretty much every home is passed by those old co-ax systems. They're quite neatly done, generally neatly tacked tightly under the facia (just below the roof) and crossing overhead for short distances or else down and underground.. It's quite common in Cork that they run along the back walls of properties just below the cap stone at the end of the garden. They're extremely extensive networks (as extensive as the phone network), as far as I know we've some of the highest cable penetration rates in Europe, you don't see very many antennas on roofs in the cities here. The old coax systems are ok for plain old TV service either analogue or digital but often can't provide 2-way access for internet, voice and interactive services. Which is why, like sky, some of the digital cable systems require the set top box to have a phone line connection for interactive stuff.

Newer housing developments would have underground coax or coax-fiber hybrid and gradually those networks are being expanded to eventually phase out the old systems. NTL are in BIG trouble here though, they bought Cablelink and its 1.9 million customers from eircom (who were forced to sell it in an attempt to break its monopolistic practicies) and part of the licence they agreed to set out requirments for upgrading the network, however NTL worldwide is doing very badly so they stopped investing here. They may loose their Irish cable licences s they've failed to update 90% of the network.

The 2 cable companies also operate a digital terrestrial microwave broadcasting system with a mirror digital television service in the 2Ghz range.. it was originally fully analogue!

Antennas look like this:


or flat ones that look a little like this:


The horrible old analogue decoders used for both cable and microwave:

Visit the site below for the whatabouts of a 1960s era cable TV system in The UK.
http://web.ukonline.co.uk/uax13/cabletv.htm

A pretty in depth history, giving certain technical detail of the system.

{ Edited only to correct link syntax - Paul }

[This message has been edited by pauluk (edited 03-23-2003).]

Thanks for posting that link. The article makes for interesting reading.

Update:

It does indeed appear that these circular encased transformers are becoming more commonly used in Britain.

I had caused to travel down to Kent today (that's down in the southeast corner of England, three counties away from here), and I saw three or four very new-looking xfmrs of this type serving one or two houses in rural areas. That's a different utility company in Kent, so it looks as though they've started using them quite regularly.

Paul,
For your information, the can type single phase transformers are quite common up here.
They only seem to be used for 1 or 2 consumers in country areas. Possibly only 10 or 16KVA.

Thanks David. It just came as such a surprise to find this type of xfmr being used here. I'm keeping my eyes peeled down every Norfolk back-lane now looking for more.

The ones I saw in Kent were also feeding just one or two houses. I guess the utilities here have finally decided that it isn't "beneath" them to adopt some American-style techniques where it's beneficial.

Any idea how long these xfmrs have been installed in Scotland?

Update: It's now over year since I posted these pictures, and I've seen quite a few more of these transformers appearing on poles out in the boondocks.

It seems as though the local PoCo has indeed decided to use them for new single-phase xfmrs feeding an odd one or two houses out on their own.