Voltages used in "neighborhood" power distribution



Ah, double dipping Don? I have hacked it's domain as well....
The world is ruled by BS as it is, you are a slave to it, you started believing once in your Schooling days. Then you became a Warrior for it after you graduated, now, Who Cares! It's what all civilized people do :) ain't that a whoot '
The only way people and Other Humans:) will be happy together in an World of Electricity is if they can own & have a small atomic plant right in their backyard, and they fuel it from refuse from their daily consumption...lol
RR
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writes:

Ah, yes, Randy or proteusiiv No capitals or" I am Proteus"?
You can't be Proteus(n) - you make marginally more sense than he/she/it does. However sensible engineering doesn't compete with BS in ruling the world.
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I do this very carefully. you never know when any freaking contraption we devise is going to become a hazard, or turn against you.
It seems essential People All Over The World consort and abide in Common Belief., One Mishap and KKKKKKaPuuueee!
No! no' the truth is that That! can/shan't won't ever happen. Well, maybe......like in a Cinegraphic Reproduction for The Common People of The World.
Hahaha you're all insane;-)
RR
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I still wonder if there is some error in this.
Do the math. 1-2 MVA distribution transformer @ 240v (or is it a 220 or 230V system?) - first think of the size of this transformer at 50Hz. The laminations required are twice the size of 60Hz transformers. Sitting on somebody's street corner or front lawn??? This could take up half a property in N.America.
- current at F.L = 2MVa / 240V = 8333 amperes (OK if three phase system wye then divide by 3) = 2777 amperes. - Cable size for 2777 amperes? Not knowledgabel about cable sizes that big in aluminum. Possibly 3000 MCM?? Who could even lift or pull that cable in a trench? (need wire charts and weight) - Now think about all the small cables spliced to this monster going to house and the fault current available.
This whole thing doesn't sound logically feasible
Andrew: You sure about this engineering monster there? Any references/cites/ pictures? I would be interested in how this is done.
We typically would use a 2-5MVa transformer as a substation every few km and 25, 50, 75, 150 kVA transformers every 8-13 houses. We use the same voltage 240v (centre tapped; Center tapped for Don...LOL) to our homes as UK. Our homes have 100 or 200 ampere services at that voltage and I understand our load density may be higher (or was years ago) The odd home will have a 400 or 600 ampere service..you know the ones with bowling alleys like most of UK has? (just kidding...LOL)
There are many different voltage levels and schemes in effect. it depends on where you are, North America, UK or elsewhere as well as load density (roughly houses per km along the line) and single/three phase distribution. Different strokes for different people or conditions. Beyond the technical factors there are historic factors which which have generated a lot of inertia, attitude problems as well as economic problems in making changeover to a world wide uniform approach. Pity Japan with both 50 and 60 Hz systems -cheapest solution is an asynchronous back to back DC link. :)
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I still wonder if there is some error in this.
Do the math. 1-2 MVA distribution transformer @ 240v (or is it a 220 or 230V system?) - first think of the size of this transformer at 50Hz. The laminations required are twice the size of 60Hz transformers. Sitting on somebody's street corner or front lawn??? This could take up half a property in N.America.
- current at F.L = 2MVa / 240V = 8333 amperes (OK if three phase system wye then divide by 3) = 2777 amperes. - Cable size for 2777 amperes? Not knowledgabel about cable sizes that big in aluminum. Possibly 3000 MCM?? Who could even lift or pull that cable in a trench? (need wire charts and weight) - Now think about all the small cables spliced to this monster going to house and the fault current available.
This whole thing doesn't sound logically feasible
Andrew: You sure about this engineering monster there? Any references/cites/ pictures? I would be interested in how this is done.
We typically would use a 2-5MVa transformer as a substation every few km and 25, 50, 75, 150 kVA transformers every 8-13 houses. We use the same voltage 240v (centre tapped; Center tapped for Don...LOL) to our homes as UK. Our homes have 100 or 200 ampere services at that voltage and I understand our load density may be higher (or was years ago) The odd home will have a 400 or 600 ampere service..you know the ones with bowling alleys like most of UK has? (just kidding...LOL)
There are many different voltage levels and schemes in effect. it depends on where you are, North America, UK or elsewhere as well as load density (roughly houses per km along the line) and single/three phase distribution. Different strokes for different people or conditions. Beyond the technical factors there are historic factors which which have generated a lot of inertia, attitude problems as well as economic problems in making changeover to a world wide uniform approach. Pity Japan with both 50 and 60 Hz systems -cheapest solution is an asynchronous back to back DC link. :)
--
Don Kelly
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Really?
Yes, the plot is normally about half the size of a house plot. Sometimes the transformer and switchgear are out in the open, sometimes in a brick building which looks like a large garage. http://www.electrospec.co.uk/substation.html Can't find an online picture of an open one at the moment, but I can go and take a picture of the one which feeds me, which is about 200yds down the road (when it's not raining).

Several 240/415V circuits, heading off down different streets, separately fused. It's quite common that an individual circuit is what's called a "ring main", i.e. it leaves the distribution panel, runs up a street and then loops back down the other side (or another street) back to the same terminals. This provides some redundancy if the cable breaks (providing it breaks into an open circuit), and the repair can be scheduled as a non-emergency.

It's not really - you care about the 120V regulation, or you have light bulbs flickering. We're 240/415V, but again it's the 240V regulation which matters, not just 415V.
(Actually, we're notionally 230/400V now with EU harmonisation, but the tollerance has been changed so we actually stay on 240/415V as measured.)

Most UK houses are 100A max, and splice only one of the three phases. If you want 3-phase, you can have it, and if you want more than 100A, then you _have_ to take a 3-phase supply (and a 3-phase supply is not limited to 100A).
Most EU countries are similar rules, except the 100A single phase limit varies. In some countries, it's as low as 20A, so almost everyone has to have a 3-phase supply.
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Andrew Gabriel
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OK to understand this better.
You use 240v/415v secondaries in a substation type building with some switchgear or fusing to down limit fault current damages into multiple neighbourhood feeds, using a ring main bus, mostly. This would allow smaller conductor sizes to neighbourhood feeds. It still sounds liek some long runs for the low voltage in far properties.
In my area(in Canada) we do this same thing at the 8/13.8kV level or 16.1/27.6kV level throughout the neighbourhood. My area used to use another transformation step in out substations and feed 2400/4160v in this matrix type feed but that has been eliminated in many parts (losses are less and insulation technology is better).
Then we have the "street transformer" that step the 8kV or 16.1kV(rural O/H) down to the 120/240volt residential voltage. No voltage regulation is typically done past the transformer output of the 8kV. None is typically needed. The "street transformers". would feed up to about 13 homes at about 50-200kVA and be the size of a short grave site or padmount above ground less than a metre cubed. (60Hz takes half the laminations). The longest feed typically would be a hundred metres for a 200A service and use 3/0 AWG. copper (forgetting the sizes now...LOL). This permits less than the 10% total voltage variance laws and typically is within a few percent of the 240. The 120v that we cherish so much is never "off centre" by more than a volt so we experience no flickering lights (you mentioned) unless a loose neutral is encountered (system defect).
With electrically heated home areas the distribution is less, say about 4-8 homes. The voltage drops would be too high for any length and not everybody wants a transformer on the front of their lawn. It devalues the property somewhat and may attract children.
So in the end we both use the same voltage distribution to most residences (240v), although different source style behind them. Most of our major loads use 240v and do not use the 120v, much...clothes dryers, electric stoves, hot tubs with heaters and 10hp pumps, etc... Lighting, small fans and recepticals typically are all 120v.
Nice to compare systems with you!
writes:

Really?
Yes, the plot is normally about half the size of a house plot. Sometimes the transformer and switchgear are out in the open, sometimes in a brick building which looks like a large garage. http://www.electrospec.co.uk/substation.html Can't find an online picture of an open one at the moment, but I can go and take a picture of the one which feeds me, which is about 200yds down the road (when it's not raining).

Several 240/415V circuits, heading off down different streets, separately fused. It's quite common that an individual circuit is what's called a "ring main", i.e. it leaves the distribution panel, runs up a street and then loops back down the other side (or another street) back to the same terminals. This provides some redundancy if the cable breaks (providing it breaks into an open circuit), and the repair can be scheduled as a non-emergency.

It's not really - you care about the 120V regulation, or you have light bulbs flickering. We're 240/415V, but again it's the 240V regulation which matters, not just 415V.
(Actually, we're notionally 230/400V now with EU harmonisation, but the tollerance has been changed so we actually stay on 240/415V as measured.)

Most UK houses are 100A max, and splice only one of the three phases. If you want 3-phase, you can have it, and if you want more than 100A, then you _have_ to take a 3-phase supply (and a 3-phase supply is not limited to 100A).
Most EU countries are similar rules, except the 100A single phase limit varies. In some countries, it's as low as 20A, so almost everyone has to have a 3-phase supply.
--
Andrew Gabriel
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On Thu, 26 Aug 2010 10:45:55 +0000 (UTC), snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote:

How far is it when it is raining?
Sorry ;-)
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------------------------------ I have a quibble here. Core size(Laminations) at 50Hz twice the size of that for 60Hz.? Are you assuming the same voltage, turns and max flux density in both cases? If so, I disagree on the basis of fundamental principles. I agree that Canadian usage in residential areas is not 1-2MVA transformers with 240V secondaries -partially because the typical load densities mean that that is prohibitively expensive and complex as you indicate. In high density areas- , I could see a 1-2MVA sub within a specific apartment/condo unit.
As for center vs centre- (US vs UK) both are valid according to the Canadian Oxford Dictionary- so being neither a Brit or a Yank, my choice is dependent on the colour/.color of my mood.
In terms of electrical supply as with language details - what exists in different regions is a rational approach (mostly) based on historical choices (right or wrong- the conversion in the latter case becomes irrationally prohibitive).
Cheers
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The only live experience I have with 50/60Hz transformers is on smaller va units....say under 300va units. The lamination sizes were always aprox double the weight of same iron gauge. I have been told by design engineers that on larger units this still roughly applies but have actual experience with the figures. I have torn apart 33MVA transformers but have no size comparison for 50Hz, never being in the UK or other countries with the S-L-O-W-E-R frequencies.
It would surprise me the Can Oxford Dictionary would state both spellings are OK as "center" was never an acceptable spelling for the word in Canada.
However, somebody has now edited the "Billion" definition on wikipedia to state that Engilsh Canada uses the 10^9 and French (should be french) Canada uses the 10^12 definition, similar to most of Europe. I was educated to believe that a billion was always 10^12 (bi-million) and that only the USA used the 10^9 billion definition. Now I am reading that Britain converted in 1974 on a flippant remark from parliament and Canada has also, except there is no back-up reference of when, who, what or why. **SIGH**
We sit in the middle of it all between the US and the Brits, confused how to say "Z" and still make the nursery rhymes rhyme....LOL
I hope this doesn't change GigaBytes or TeraBytes! Those big quantities are changing things to be common place faster than we like sometimes.
On that note: a question???
What is the quantity "milliHelen" (see bottom of post for definiton)

------------------------------
"milliHelen" is a measurement of beauty! The quantity of beauty it takes to launch one ship.
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For a given voltage, maximum flux density and turns per winding, the core cross section is increased by a factor of 1.2 so the core side length is increased by a factor of nearly 10% (square cross section). Assume a square core window (not true in general) and the same winding window area, the average core length and width increase by a factor of 1.2 leading to a volume/weight less that 1.5 times that at 60 Hz. Twice the weight is a conservative estimate and may involve factors other than frequency dependence. The core dimensions of 300VA transformers (50/60 Hz) are affected by a number of factors-of which cost and customer reaction are dominant. Hammond put out reasonably priced transformers which sacrificed core losses in order to have better voltage regulation [balance between core and copper losses for a given price]

--
I checked my Canadian Oxford Dictionary before I made this statement. It
also accepts color/colour, meter/metre , center/centre , etc and some other
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There isn't really any accurate math formula to compute the output winding. For instance, you guys like to wind your transformer using inner window area, I get more output power using outer core. 150V as supposed to get 100V.
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On Wed, 1 Sep 2010 10:43:25 -0700, "Edmond H. Wollmann"

Boy are you ever lost...
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---------------- It is the interior window area that physically limits the winding net cross section (turns, conductor cross section and insulation) -either HV or LV- half the winding is inside the window. So we have a balance between conductor cross section (i.e allowable current) and number of turns( voltage) for a given rated power. Once the voltage and KVA ratings are fixed, then it is a choice of balance between of core and copper losses for a given $ input and load profile (is the average load going to be 50% of rating or 90%- it makes a difference).
Possibly you could clarify "outer core" vs "inner window" which are two different things-neither of which determine power. (100V vs 150V is not power).
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After all that cunning display of accuracy and knowledge I doubt you meant to type 10^6 twice (Two times for the USanians)...LOL
My family has been in Canuckistan since the early 1700s when a ship from "jolly old" sank off the banks of Newfoundland...4 miles out. Only one survivor swam ashore. Fiance (sp?) came years later and we had offspring in rabbit succession. Funny thing is, we have a long list of swimmers in our family. One cousin was set to take gold in the Russian olympics that were boycotted years back. Son swam for the Ontario championships. Funny coincidence but I hate my webbed feet!
As to billion - In general usage in Canada, economically and in general ,the 10^6 value is what is used. Do you think that Quebec uses a different value? Does the world of economics use a different value? I recognize (recognise) that these differences exist so kilo/mega/tera make more sense. For Canada,within my memory (I am approaching 79) the 10^6 value was a billion.
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Officially, I have an edge- Newfoundland wasn't part of Canada until 1949. There is also the possibility, not proven (damn, no tax benefits) that some of my ancestors were complaining about illegal immigrants.
I like the "rabbit succession" a common factor!
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So you were a foreigner until Newf joined into our great country?...LOL

Officially, I have an edge- Newfoundland wasn't part of Canada until 1949. There is also the possibility, not proven (damn, no tax benefits) that some of my ancestors were complaining about illegal immigrants.
I like the "rabbit succession" a common factor!
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Hey, we sent you the moose as an alternative to salt cod, in return for Newfie jokes! :>))
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I like a nice rack!
Hey, we sent you the moose as an alternative to salt cod, in return for Newfie jokes! :>))
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snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) writes:

Yes, but being on the end of a 500m run from the transformer would cause quite a bit of drop between the transformer and you, esp. with your neighbors also present as loads. You must have serious sized conductors running down your streets.
It would be 4 times worse (that is, intolerable) at 120V vs, 240V, true, but at such distances even 240V would have problems.
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