ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
Increasing demand factors in residential
by tortuga - 03/28/24 05:57 PM
Portable generator question
by Steve Miller - 03/19/24 08:50 PM
Do we need grounding?
by NORCAL - 03/19/24 05:11 PM
240V only in a home and NEC?
by dsk - 03/19/24 06:33 AM
Cordless Tools: The Obvious Question
by renosteinke - 03/14/24 08:05 PM
New in the Gallery:
This is a new one
This is a new one
by timmp, September 24
Few pics I found
Few pics I found
by timmp, August 15
Who's Online Now
0 members (), 265 guests, and 15 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 4 of 8 1 2 3 4 5 6 7 8
Joined: Aug 2001
Posts: 7,520
P
Member
Hi there studentlearner, and welcome to ECN.

I'll take your question as an opportunity to re-post some images of British apparatus to give you an idea.

Compared to the U.S., final distribution here tends to have a smaller number of larger transformers. Like Ireland, Britain also has sub-stations in towns and villages, with a 3-phase 4-wire distribution network at 240/415V. The majority of homes take just a 2-wire 240V feed from this system.

Here's what a typical small sub-station looks like from the outside:

[Linked Image]

And here's the apparatus within:
[Linked Image]

In rural areas, or the edge of town where a group of houses stand on their own, you might see a 3-phase pole transformer, like this one:
[Linked Image]
[Linked Image]

Single-phase transformers are normally found only in rural areas where just one or two houses need to be fed:
[Linked Image]



[This message has been edited by pauluk (edited 08-19-2003).]

Joined: Aug 2001
Posts: 7,520
P
Member
I received the following by e-mail from a Mr. Jerry Hayward:
Quote
I have really enjoyed your recent postings along with djk and JohnS.

I would submit for JohnS information that both Westinghouse and AEG transmitted ac power in 1891; Westinghouse at 133 1/3 Hz and AEG at 50 Hz.

The Westinghouse history says that by the end of 1892 it had chosen 60 Hz for lighting and 30 Hz for applications where the power was turned into dc.

25 Hz was used at Niagara Falls because the general contractor had already chosen 250 rpm turbines. With 12 poles this got the frequency to 25 Hz which was between what Westinghouse wanted (30 Hz) and what an outside constultant recommended 16 2/3 Hz. This was long before the synchronous clock was invented in 1916. That inventor made a big effort to get the frequency exact so his clocks could be used and this might be what JohnS relates in his posting.

Westinghouse had earlier used 133 1/3 Hz for ac work because his first generator ran at 2000 rpm (Steam engineers liked to have round numbers for the rpm by this time) and had 8 poles. The resultant 8000 cycles per minute or 133 1/3 Hz was good for lighting. But when Tesla came along with his ac induction motor which was optimised for 60 Hz, Westinghouse changed to 60 Hz.

The one thing that I don't know for certain is why Westinghouse/Tesla chose 60 Hz. The Westinghouse history indicates that other engineers chose the frequency rather than Tesla but if true I haven't seen the reasons why they chose as they did. Various things I have read on Tesla suggest that a) he
did a study and decided that 60 Hz was the best frequency and/or b) he was somewhat of a mystic and kook who considered this as part of the fundamental frequency of the universe or what ever.

GE and Westinghouse cross licensed their patents so it makes sense that both worked the same frequencies here in North America.

In Germany 50 Hz was chosen. I don't know why but I could guess that with a 3000 rpm machine (same idea of round numbers for steam engine rpm) it was easy to go to 50 Hz with no Tesla/Westinghouse to insist on 60 Hz. 50 or 60 Hz both work well and once chosen there may not have been enough reason to change to the other frequency for either company. Any thoughts on this?

{Edited to correct name -- My apologies! [Linked Image]}

[This message has been edited by pauluk (edited 09-13-2003).]

Joined: Dec 2002
Posts: 1,253
D
djk Offline
Member
The one thing that always supprises me is how uniform European Electrical systems actually are.

All of Europe, with the historical exception of the UK, Cyprus, Malta and Gibraltar, used 220V 50 Hz

The UK settled on 240V also at 50Hz.

Making it easy to jump to 230V 50Hz as a harmonised nominal standard.

I just find it amazing that unlike in many other areas that we didn't end up with 5/6 different frequencies.

With the UK on 66.6666 Hz and France on 100 Hz or something along those lines [Linked Image]


[This message has been edited by djk (edited 09-14-2003).]

Joined: Aug 2002
Posts: 1,691
S
Member
DJK:

Are the European countries interconnected electrically?

I think the USA and Canada are. I don't know about the USA and Mexico (even though both have roughly the same nominal voltage and use 60 hertz as frequency).

Joined: Dec 2002
Posts: 1,253
D
djk Offline
Member
Yeah, most EU countries are interconnected these days (in many cases have been for many years) and power is bought and sold all over the place between generators and distributers etc. (Within the European Union a fully deregulated power market is supposed to operate in theory anyway.. or at least that's the plan!)

Depending on which countries you're talking about the interconnectiors may be at 50Hz or DC. Generally EU countries have very similar frequency tollerances but I would suspect that for much of contenental Europe you're more than likely getting the same 50Hz.

However, perhaps unlike North America, the system would tend to consist of national grids which are interconnected at points rather than one pan European grid. I don't think you could get the cascade effect that happened in the North East of the US / South East of Canada.

Although are there state/regional grids in the US too?

Ireland's one of the few exceptions (being an island), ESB Networks only recently having opened a number of high tension interconnectors to Northern Ireland and until very recently Northern Ireland wasn't connected to the rest of the UK, however a major underwater DC interconnector is now in operation.

There is a proposal to run an interconnector from the Republic of Ireland to the UK, also very high voltage DC but as yet its cost far outweights any benefits it might bring as there is adequate capacity and a lot of new generating capacity from various companies coming online here.

Interconnectors from the UK to other EU countries are only relatively recent too. Again, being an island there are massive cost implications to large underwater interconnectors so the benefits have to be very clear before any company will invest in such a venture.

Joined: Aug 2001
Posts: 7,520
P
Member
I know there has been a DC interconnector between England and France since at least the 1950s, possibly earlier. The one-hour time difference between us, along with French working/dining hours tending to be a little different to ours meant that our peak demand times don't coincide, so the mutual benefits were recognized quite early on.

I've tried to track down some information on the net as to when it went into service, the original power capacity, and so on, but haven't been able to find anything.

Joined: Sep 2002
Posts: 1,498
Likes: 1
C
C-H Offline
Member
Quote

However, perhaps unlike North America, the system would tend to consist of national grids which are interconnected at points rather than one pan European grid. I don't think you could get the cascade effect that happened in the North East of the US / South East of Canada.

Yup. The UCTE has strict requirements for grids that wishes to be connected to the UCTE grid (which simply consists of the national grids of UCTE countries). If you don't have enough reserve power (long term), you'll be refused connection. I don't know what they do with countries that are already connected but starts to cheat.

Some countries are split between different grids: Half of Denmark is connected to Germany (UCTE), the other half to Sweden (Nordel). Ukraine is split between the grid of the former Soviet Union (CIS) and the UCTE grid.

[This message has been edited by C-H (edited 09-15-2003).]

Joined: Apr 2002
Posts: 2,527
B
Moderator
Some minor followup US references...
djk, a couple of maps on the US system… http://www.nerc.com/regional/ http://www.wecc.biz/maps_diagrams/nerc_int.pdf

Sven, on your question about Mexico’s involvement in the North American system, officially it’s described as “…a portion of Baja California Norte, Mexico.” The 1997 NERC transmission map shows 230kV lines in far NW Mexico extending south ~25-50 miles to Cipres and Cerro Prieto (could be city or substation names.) There are probably some southern New Mexico and Texas towns that are electrically interconnected [<69kV] to a few border cities in Mexico, as are some local telephone exchanges.

Joined: Aug 2001
Posts: 7,520
P
Member
Some more from Mr. Hayward:
Quote
In response to djk post on standardization I agree with him for the most part although standardization seems to have been painfully achieved as systems interconnected with each other.

Here in North America Southern California was a 50 Hz system until after World War 2 when it converted to 60 Hz to be similar to the rest of North America. The power company bought new clocks for its customers and helped business and residents achieve the changeover.

In 1918 in London alone there were 70 electric authorities with 50 different types of systems and 10 different frequencies and 24 different voltages. Great Britain didn't get relatively standardized until just before World War 2 when East Anglia, which was on 40 Hz, changed to 50 Hz.

Hungary in 1911 had forty-two dc power plants, nineteen 42 Hz, and twelve 50Hz plants.

Krakow Poland converted from dc to 50 Hz in 1912.

Western Australia was 40 Hz until 1958 when it changed to 50 Hz like the Eastern part.

AEG seems to have chosen 50 Hz as the main frequency in Germany and with Siemens as one of the largest electrical companies in the world I wonder if this isn't one reason why eventually everything in Europe and later the rest of the world except North America and other small exceptions became 50 Hz.

Some interesting points there. I knew of the vast variety of systems in use in the London area around 1918, but I hadn't realized that parts of East Anglia (in which I have lived for six years!) didn't convert to 50Hz until so late.

Standardization of voltages to 240/415V took even longer in Britain, the process being completed only in the early 1970s.


[This message has been edited by pauluk (edited 09-15-2003).]

Joined: Aug 2003
Posts: 24
K
Member
In my first apartment as an adult in NYC the power was 110V DC, powered from a generating plant around the corner! Had to get a noisy inverter to play my 78 rpm records. (For those who know New York, it was the lower east side, Ave. C and Stanton).

Edison's DC power plants were placed all over the city since it was not economical to transmit 110V DC at distances.

One frequency note: I have read that 25Hz is more efficient for large motors, and that parts of the European rail system uses it today. 60 Hz gets you beyond the noticeable flicker frequency for lighting.

Karl

Page 4 of 8 1 2 3 4 5 6 7 8

Link Copied to Clipboard
Powered by UBB.threads™ PHP Forum Software 7.7.5