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#136159 - 03/17/03 03:03 PM Unusual transformer
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
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).]

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#136160 - 03/17/03 04:58 PM Re: Unusual transformer
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
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?

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#136161 - 03/17/03 05:38 PM Re: Unusual transformer
djk Offline
Member

Registered: 12/26/02
Posts: 1269
Loc: Ireland
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.

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#136162 - 03/17/03 06:04 PM Re: Unusual transformer
djk Offline
Member

Registered: 12/26/02
Posts: 1269
Loc: Ireland
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.


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#136163 - 03/18/03 02:24 PM Re: Unusual transformer
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
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.

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#136164 - 03/18/03 04:24 PM Re: Unusual transformer
djk Offline
Member

Registered: 12/26/02
Posts: 1269
Loc: Ireland
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.

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#136165 - 03/18/03 07:47 PM Re: Unusual transformer
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
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.

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#136166 - 03/18/03 11:12 PM Re: Unusual transformer
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
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.
_________________________
Let's face it, these days if you're not young, you're old - Red Green grin

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#136167 - 03/19/03 07:23 AM Re: Unusual transformer
djk Offline
Member

Registered: 12/26/02
Posts: 1269
Loc: Ireland
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.

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#136168 - 03/19/03 04:15 PM Re: Unusual transformer
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
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).]

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