The grid in the US does not run at 120V. The last 100 feet is 120V-240V in most places. Really the lines into the houses are 240V just split in two.
US has tornadoes, hurricanes, and earthquakes. Every few years the Mississippi river will flood -- as will its tributaries. It would be interesting to see, and the numbers are somewhere, if the Mississippi floods more frequently than the Rhine.
France uses concrete utility poles. An abundance of timber in the US allows this country to use wood.
(It looks like this will be the second year since 1994 that we haven't been able to visit FR)
In the Netherlands people live below sea level and 50 kV cabling still is used underground (with high groundwater level). Also counts for 25 and 10 kV cabling.
When I have work to be done on mid voltage cabling then a few pumps are necessary as it does not take long to create a small lake 🙂
When I have work to be done on mid voltage cabling then a few pumps are necessary as it does not take long to create a small lake 🙂
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Yes, every house built in the USA is fed from a 240 Volt CT transformer. The "small loads" are fun from one side to the CT for 120 volts. These are split nearly evenly throughout the house so that the CT (neutral wire) current is minimal. Large loads like AC, heating, cooking and clothes drying are fed from the two hot wires for 240 volts. Anyone desiring a 240 volt outlet only needs to put a breaker in the existing panel and run wires to it. For me, the panel is close to my bench.
Most industrial, shopping, or other high use locations are three phase at voltages from 208 to 600 volts. The plant where I worked had a 3 phase at 14.4 KV underground feed, as do most hospitals. It was back up after the storm as soon as the major transmission lines were fixed, about 1 week.
The US began using concrete poles 30 some years ago. I got out on my bicycle after hurricane Wilma trashed the place and found far more broken concrete poles than wooden poles. Most of the broken concrete poles had a street light that stuck out from the pole. That thing would start oscillating in the wind stressing the pole causing it to break right at the ground. Most of the broken wood poles broke near the middle.
In most of europe and even new houses here in backwards Norway, it's commonly TN 400v, so one neutral with three 240v phases.
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Rest of the world is also mostly some form or other of 220-240v on each and every socket in the walls.
US and Canada are stuck at 120v.
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Yes and in many countries just 1 of 3 phases connected per home. A well thought out and reliable system.
They were available before 1920. I seen them in old books. As said, historically North America had plenty of tall straight trees, and creosote preservative, so wood was the popular choice. Some places run tall 200KV lines on steel towers, but here in Maine we use wood for all but the tallest installations.
Kaffimann,
Distribution is done at higher voltages. The cables running down the street around here run 13,500 volts. This is stepped down to 240 volts with a center tap for the usual users.
In most residences there is the center tap conductor that is also grounded. The idea is that all the 120 volt loads should be balanced so that the center tap conductor carries a minimal current.
The result is that efficiency gets almost to as if all lines are 240 volts. The advantage is that 120 volts is considered below a fatal threshold. Next up is we use 60 hertz distribution frequency, thus transformer cores can be 20% lighter or the losses lower.
To confuse things even more the high voltage distribution mains are three phase and a single phase drivers a row of the 240 volt step down transformers.
Of course virtually none of the users understand this.
Also of note is that the final AC voltage is slowly being raised. I have seen 120 volt lines actually running 132 volts. Not from mismatch but in line with the electric code time/voltage schedule.
The reason for the lower voltages was the Edison - Westinghouse dispute. Among other stunts was the electrocution of an Elephant to show how dangerous high voltage AC power could be. Edison thought there would be multiple small local DC power plants.
Distribution is done at higher voltages. The cables running down the street around here run 13,500 volts. This is stepped down to 240 volts with a center tap for the usual users.
In most residences there is the center tap conductor that is also grounded. The idea is that all the 120 volt loads should be balanced so that the center tap conductor carries a minimal current.
The result is that efficiency gets almost to as if all lines are 240 volts. The advantage is that 120 volts is considered below a fatal threshold. Next up is we use 60 hertz distribution frequency, thus transformer cores can be 20% lighter or the losses lower.
To confuse things even more the high voltage distribution mains are three phase and a single phase drivers a row of the 240 volt step down transformers.
Of course virtually none of the users understand this.
Also of note is that the final AC voltage is slowly being raised. I have seen 120 volt lines actually running 132 volts. Not from mismatch but in line with the electric code time/voltage schedule.
The reason for the lower voltages was the Edison - Westinghouse dispute. Among other stunts was the electrocution of an Elephant to show how dangerous high voltage AC power could be. Edison thought there would be multiple small local DC power plants.
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Hi, that is outdated by decades. Voltages below 50V AC or 120V DC are considered safe. It is also current related.
60 Hertz may result in lighter transformer cores but the lower voltages sure result in needing a lot more copper 🙂 The transformers are also not ideal and losses should be taken into account. It would be more efficient to use the already available 240V. Lighter cabling and lighter switches so more optimal use of resources, half the current so less losses.
If one calculates one will find out that 3 phase 400V systems with 230/240V line voltages are far more efficient. The future will either be 250V or even 400V.
60 Hertz may result in lighter transformer cores but the lower voltages sure result in needing a lot more copper 🙂 The transformers are also not ideal and losses should be taken into account. It would be more efficient to use the already available 240V. Lighter cabling and lighter switches so more optimal use of resources, half the current so less losses.
If one calculates one will find out that 3 phase 400V systems with 230/240V line voltages are far more efficient. The future will either be 250V or even 400V.
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Well, as I uderstand it. each home in the US is delivered 220-240V, but with a center tap. The big power stuff runs off the 220, the little stuff shares one side or the other of the tap.
The transformer delivering this covers a couple-few houses and is either hanging on a pole or under a metal cover and that gets 4kV or so to transform down from.
Unsure if 220 gets into arc-flash territory, I know 440 definitely does from my training at Amazon. 440 is a nasty voltage level, but they use it so the cables arent so thick. Save that for speaker wiring...
The transformer delivering this covers a couple-few houses and is either hanging on a pole or under a metal cover and that gets 4kV or so to transform down from.
Unsure if 220 gets into arc-flash territory, I know 440 definitely does from my training at Amazon. 440 is a nasty voltage level, but they use it so the cables arent so thick. Save that for speaker wiring...
Edison and Westinghouse have been dead for a while. That was the historical reason for what was 110 volts AC distribution. Current electrical code only starts worrying above 25 volts.
As to copper use, the longer winding is a result of the distribution voltage. A 120 volt winding requires half the copper of a 240 volt one. No issue on that.
The limit to minimizing winding length has to do with current and core saturation. 60 hertz has the advantage for that.
The transformer design issue affecting efficiency is allowable temperature rise. There is some contribution to that from conductor size, number of turns, core size, lamination thickness and core material for the most significant issues. Cheaper transformers get hotter and are less efficient.
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You forget to mention that the transformer may need less copper but the whole country will need way more copper for the wiring, switches etc. And a 120 Volt winding may require half the copper of a 240 Volt winding but that won't matter when using 2 x 120V transformers with a CT 🙂 115/120V is an outdated system not available in most developed countries where high availability is the standard.
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Jean-Paul,
I am starting to see some 24 VDC home systems to run easily from solar panels and storage batteries.
Yes local 120 volt loads do draw more current. Most high current loads from heating, air conditioning and cooking are already 240 volts. Of course with the rising voltage standard most gear these days is supposed to run as high as 265 volts if I recall correctly.
Also every so often the local wiring is not copper! Some tried aluminum, but the increase in fires due to poorly done connections discouraged that. Currently some are trying copper clad aluminum.
Of course the biggest change is reducing power demand. Lighting used to be the largest portion of home loads. That has changed rather dramatically. I suspect entertainment systems may be next for those that cook and heat with natural gas. For reasons I don’t understand some places are trying to eliminate residential natural gas service.
When I was wiring my house it was clear that I could wire all of my lighting needs with 18 gauge wire, but none is available for such use and still follow the electrical code. Very silly to use wire rated for 15 amps with a 250 milliampere load! I also couldn’t find any main panel approved circuit breakers for a one amp load!
I am starting to see some 24 VDC home systems to run easily from solar panels and storage batteries.
Yes local 120 volt loads do draw more current. Most high current loads from heating, air conditioning and cooking are already 240 volts. Of course with the rising voltage standard most gear these days is supposed to run as high as 265 volts if I recall correctly.
Also every so often the local wiring is not copper! Some tried aluminum, but the increase in fires due to poorly done connections discouraged that. Currently some are trying copper clad aluminum.
Of course the biggest change is reducing power demand. Lighting used to be the largest portion of home loads. That has changed rather dramatically. I suspect entertainment systems may be next for those that cook and heat with natural gas. For reasons I don’t understand some places are trying to eliminate residential natural gas service.
When I was wiring my house it was clear that I could wire all of my lighting needs with 18 gauge wire, but none is available for such use and still follow the electrical code. Very silly to use wire rated for 15 amps with a 250 milliampere load! I also couldn’t find any main panel approved circuit breakers for a one amp load!
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The suggestion by the industry is to go to 400 V DC for solar systems to keep conversions out and losses down. 24 V DC would need very thick conductors. Switches would not last long. Homes will need to be completely rewired (how when cabling is in wall?) with more and thicker copper cabling and have polarized connectors. Copper is already harder to mine. I would classify it as "non green". Large battery arrays in laymen's homes is eh... interesting. I recently calculated such a project but I think I would not like to have a stack of LiFePO4 batteries somewhere in my home.
I see private initiatives doing low voltage DC but it is choosing for easy, not for optimal. The big elephant in the room with all alternative energy is of course storage of the energy but that will be solved (I hope).
I see private initiatives doing low voltage DC but it is choosing for easy, not for optimal. The big elephant in the room with all alternative energy is of course storage of the energy but that will be solved (I hope).
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JP,
24 volts is below what the electrical code regulates. Thus the popularity. Perhaps not very wise!
Also enormous lead acid batteries are easily available.
Of course the only such installations I have seen are in vacation homes that locally are called “camp.” Usually located in or near a forest, remote from utilities and with a local well and sewage system.
24 volts is below what the electrical code regulates. Thus the popularity. Perhaps not very wise!
Also enormous lead acid batteries are easily available.
Of course the only such installations I have seen are in vacation homes that locally are called “camp.” Usually located in or near a forest, remote from utilities and with a local well and sewage system.
Lead acid batteries in or near civilians homes... When done DIY it won't be covered by insurance when the house burns down (here).
It is odd that 24V DC is below what the electrical code regulates as the currents are way higher. We have 48V DC systems here for telecom and the UPS system for those is ... yes 4 x 12V lead acid batteries in series and that battery string in parallel with many other strings. These systems may be lowish in voltage but they are quite dangerous.
It is odd that 24V DC is below what the electrical code regulates as the currents are way higher. We have 48V DC systems here for telecom and the UPS system for those is ... yes 4 x 12V lead acid batteries in series and that battery string in parallel with many other strings. These systems may be lowish in voltage but they are quite dangerous.
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You know that lead acid batteries can produce a very explosive gas? One of the reasons here LiFePO4 is required. Densely populated areas, high availability/reliability required so 99.9% uptime, strict safety regulations, high involvement of governmental organizations, strict "green" requirements etc. The works. Mostly annoying but in general OK results. Power blackouts, where I live I only had it once in 9 years. A lightning strike and after new mid voltage fuses were installed things worked again except for the internet router. Too bad the energy production is exclusively in the hands of private companies today....
Anyway, with regards to energy losses... the higher the voltage the lower the losses. Be it AC or DC.
Anyway, with regards to energy losses... the higher the voltage the lower the losses. Be it AC or DC.
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......... Wiring is done with maximum available current of the house installation/group in mind. The cabling should be able to cope with a short circuit current as well..... The fuse of that group protects the cable not the load....