Author Topic: 400 volts for power  (Read 600 times)
Keyless
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400 volts for power « on: June 12, 2019, 05:56:59 PM » Author: Keyless
Could 400 volts be used where 230 volts is used now? How would the construction of appliances and light bulbs change? Would it be more or less cost effective to build such appliances? Would losses for appliances go up or down over all? Safety? Anything else I'm forgetting?


I can see the concept saving copper and greatly simplifying the installation practice. 3 phase TN-C-S and TT can become TN-S without the neutral distributed eliminating the risks of broken neutrals and parallel current paths. Single phase circuits can now carry near double the power.


What do others think?   
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Medved
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Re: 400 volts for power « Reply #1 on: June 13, 2019, 12:39:13 AM » Author: Medved
First it wont save nearly anything, as across most of the distance the 3x230/400V goes there are nearly no currents in the Neutral and so these are wired as TN-C. Because the PE would needed to be wired anyway, it is 4 wires with 3 of them loaded like 4 wires with 3 of them loaded. Even today the Neutral uses to be significantly thinner anyway (I'm talking about distribution cables, not home installations), just because its function is practically just PE and load voltage balancing, so it is sized according to what its function as PE requires, so the same as it would be sized when 230V phase-to-neutral won't be used at all.
The end users would benefit only with 3 phase sockets (4 wires instead of 5), the single phase ones would still need 3 wires anyway.

The Neutral was placed there explicitly to allow more practical lower voltage for the end user, yet still benefit from the higher voltage for the ("last mile") distribution without need for any transformers on the consumer side. In fact the idea came from Edison, who was distributing the DC as 2x120V in such way customers get 120V, but the load was mainly across the 240V, so distribution losses were related to that voltage.

The optimum voltage depends on the power used and the distance to pass.
The thing is, the home power consumption is decreasing over time (more energy efficient everything), so there is no practical need to go higher anymore (contrast to the first half of the 20'th century, when the electricity use was booming so the 120V became too low so Europe transitioned to 220..240V end user voltage). This still alows nearly 3kW per socket, yet there are only very few devices needing that much of power (majority stays below 100W)

I see more and more often an installation with lighting circuits running 12V DC as the low power of LEDs allow that and it makes a battery backup very simple and cheap (in fact it is rather 13.5V during normal operation).
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Re: 400 volts for power « Reply #2 on: June 13, 2019, 09:20:57 PM » Author: Keyless
First it wont save nearly anything, as across most of the distance the 3x230/400V goes there are nearly no currents in the Neutral and so these are wired as TN-C.
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There is still some current, and if the neutral breaks you either have equipment over voltages and elevated voltages to remote earth at the building (ie outside spigot) associated with an open neutral- or TELCO shields, water mains, ect take over the function without indication.


TT solves the elevated neutral to earth voltage contingency, but not the over voltage appliances are subjected to.



Quote
Because the PE would needed to be wired anyway, it is 4 wires with 3 of them loaded like 4 wires with 3 of them loaded. Even today the Neutral uses to be significantly thinner anyway (I'm talking about distribution cables, not home installations), just because its function is practically just PE and load voltage balancing, so it is sized according to what its function as PE requires, so the same as it would be sized when 230V phase-to-neutral won't be used at all.
The end users would benefit only with 3 phase sockets (4 wires instead of 5), the single phase ones would still need 3 wires anyway.
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The end user would have about half the home runs for the same mm2 cable because any one circuit can now deliver near double the power- about twice the devices.



Quote
The Neutral was placed there explicitly to allow more practical lower voltage for the end user, yet still benefit from the higher voltage for the ("last mile") distribution without need for any transformers on the consumer side. In fact the idea came from Edison, who was distributing the DC as 2x120V in such way customers get 120V, but the load was mainly across the 240V, so distribution losses were related to that voltage.
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Indeed, but he had 110 volt lamps and not 220 volt lamps so he had to use such a system. What if we were to build 400 volt lamps today?

In any case a separate neutral would still be a good idea from a fault clearing perspective.

 

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The optimum voltage depends on the power used and the distance to pass.
The thing is, the home power consumption is decreasing over time (more energy efficient everything), so there is no practical need to go higher anymore (contrast to the first half of the 20'th century, when the electricity use was booming so the 120V became too low so Europe transitioned to 220..240V end user voltage). This still alows nearly 3kW per socket, yet there are only very few devices needing that much of power (majority stays below 100W)
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Ok- so if 230/400 is the set ceiling and we are good with it- why not just connect everything Line-Line? An 800 lumen led would in theory still draw 6 watts regardless if it was rated 120, 230 or 400 volts.


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Medved
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Re: 400 volts for power « Reply #3 on: June 14, 2019, 02:29:59 AM » Author: Medved
400V maz allow nearly twice of the power, but the thing is there is no need for such high power anymore, most devices are well below 1kW, where the 230V means currents way below 5A.
There are only very few devices needing anything close to the present maximum and for these it is enough. The higher load devices have fixed placement, so may easily get either thicker wires to just that place (cloth dryer and washer, dish washers) or use 3-phase connection (stoves,...), the other use the high power only for very brief time and usually would have no problem sufficing with even lower wattage (tea kettles,...; in the US they are 1500W rated instead of 2.2kW common in  Europe and people are happy with them. Moreover in countries like Britain the high peak power (when synchronized by TV show schedules - ending of a popular show makes many people to start making tea at exactly the same time) poses quite large problem for the grid operators to maintain the grid stability, so there comes the push for regulations to limit the power rating of devices like those tea kettles.

The wire gauge is indeed mainly dictated by the current load and resistance, but the mechanical integrity starts to play more and more significant role as well.
That means thinner wires are not likely to be used either.

Plus 400V is way greater problem for arc suppression, mainly in fuses and circuit breakers. Today the 230V connection suffices with just one trigger sensor per function and one arc loaded contact in a breaker (the Neutral is sufficient to design to break later in the sequence, hence not stressed by the far short circuit arc; the Neutral does not need any current sensing), the 400V across phases will need two such contacts per each circuit, so twice as expensive (you can not get away with a single, because there could be short circuit to ground). So twice as expensive fusing.

And the "6W LED is a 6W LED": That is not completely true. The thing is, these powers are quite low to design really efficient converter. Even the 230V ones used in LEDs have rarely efficiency above 75% (so the "6W LED" is actually 4.5W LED + 1.5W losses in the ballast), higher voltage would mean even lower efficiency (60% would be challenge), so the "6W" would become a 7.5W input power device.

Yes, at Edisons time they wanted to deliver 120V (because of the fusing/switching difficulties at DC), but the power was used virtually only for the lighting. Then over the 20'th century, when there was a promise for the electricity would become "too cheap to meter", the power use extended to heater devices, labor saving appliances and so on, so the demand grew. Then (end of 20'th century onwards) it became clear the electricity will in fact never be "cheap" (with a prospect to become more and more expensive instead), so push for efficiency started and the demand started dropping significantly. One exception would be car charging, but these would most likely be special sockets using complete 3 phase power (to limit grid disruption), but that would be just a single point (maybe with two sockets; the higher power justifying the more complex protection for the 3-phases connection) in a house, but nothing more.

So I don't believe the consumer electricity would go to any higher voltage.
I would rather guess in case of the decentralized power production with local generation and temporary storage, if there would be any change at all, there would be push to use directly the DC storage battery power at lower voltage, just to save the many conversion losses (DC battery -> AC mains -> DC for most of the modern equipment using electronic front end anyway even today)
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Re: 400 volts for power « Reply #4 on: June 15, 2019, 12:57:43 AM » Author: Keyless

400V maz allow nearly twice of the power, but the thing is there is no need for such high power anymore, most devices are well below 1kW, where the 230V means currents way below 5A.
There are only very few devices needing anything close to the present maximum and for these it is enough. The higher load devices have fixed placement, so may easily get either thicker wires to just that place (cloth dryer and washer, dish washers) or use 3-phase connection (stoves,...), the other use the high power only for very brief time and usually would have no problem sufficing with even lower wattage (tea kettles,...; in the US they are 1500W rated instead of 2.2kW common in  Europe and people are happy with them.


I understand, but you still have more then one circuit in a home. And the rating of each device dictates how many of each can be on a circuit.

By going from 230 to 400, you need less home runs leaving the panel. Meaning if you had a 2,000 watt washer and 2,000 watt tumble dryer (just as an example) my choices are two 1.5mm2 10amp circuits or one 2.5mm2 20 amp circuit. But at 400volts, I only need one 1.5mm2 circuit. Both 230 volt options require more copper then the 400 volt option.  

  





Quote
Moreover in countries like Britain the high peak power (when synchronized by TV show schedules - ending of a popular show makes many people to start making tea at exactly the same time) poses quite large problem for the grid operators to maintain the grid stability, so there comes the push for regulations to limit the power rating of devices like those tea kettles.

This is cultural issue unique to Britain. I don't think the government, code or electro standards should dictate anything outside of human safety and protection of property. A 3000 watt kettle isn't going to electrocute or burn down the property with proper isolation and thermal fusing.  


Quote
The wire gauge is indeed mainly dictated by the current load and resistance, but the mechanical integrity starts to play more and more significant role as well.
That means thinner wires are not likely to be used either.
\

Certainly. Which is why the IEC does not recommend conductors under 1.5mm2 be used in building wiring. But still, any conductor can run either 100 devices or 170 devices based on the voltage.      


Quote
Plus 400V is way greater problem for arc suppression, mainly in fuses and circuit breakers.


Not necessarily with an earthed star (Y) or center earthed source. Any one pole is going to interrupt 230 volts line to earth conductor. For a Line-Line fault both poles will share the arc about equally. Thus any 2 pole slash rated circuit breaker has to only take line to earth voltages into account.        


Quote
Today the 230V connection suffices with just one trigger sensor per function and one arc loaded contact in a breaker (the Neutral is sufficient to design to break later in the sequence, hence not stressed by the far short circuit arc; the Neutral does not need any current sensing), the 400V across phases will need two such contacts per each circuit, so twice as expensive (you can not get away with a single, because there could be short circuit to ground). So twice as expensive fusing.

Not necessarily. By having fewer circuits at 400 volts, you have fewer breakers at 400 volts. So instead of having 12 16amp single pole breakers, you have 7 16 amp double pole breakers. The cost increase is for only one extra double pole breaker in this example.



Quote
And the "6W LED is a 6W LED": That is not completely true. The thing is, these powers are quite low to design really efficient converter. Even the 230V ones used in LEDs have rarely efficiency above 75% (so the "6W LED" is actually 4.5W LED + 1.5W losses in the ballast), higher voltage would mean even lower efficiency (60% would be challenge), so the "6W" would become a 7.5W input power device.

I will agree with this, and it does make sense in that the ballast will have to drop more voltage for the same series of LEDs.  



Quote
Yes, at Edisons time they wanted to deliver 120V (because of the fusing/switching difficulties at DC), but the power was used virtually only for the lighting. Then over the 20'th century, when there was a promise for the electricity would become "too cheap to meter", the power use extended to heater devices, labor saving appliances and so on, so the demand grew. Then (end of 20'th century onwards) it became clear the electricity will in fact never be "cheap" (with a prospect to become more and more expensive instead), so push for efficiency started and the demand started dropping significantly. One exception would be car charging, but these would most likely be special sockets using complete 3 phase power (to limit grid disruption), but that would be just a single point (maybe with two sockets; the higher power justifying the more complex protection for the 3-phases connection) in a house, but nothing more.

So I don't believe the consumer electricity would go to any higher voltage.
I would rather guess in case of the decentralized power production with local generation and temporary storage, if there would be any change at all, there would be push to use directly the DC storage battery power at lower voltage, just to save the many conversion losses (DC battery -> AC mains -> DC for most of the modern equipment using electronic front end anyway even today)



Come reality I doubt anything will change. But from a practical standpoint its worth considering. Remember that at one point most of the world was 110-127 volts only latter going to 220-230.  
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Re: 400 volts for power « Reply #5 on: June 15, 2019, 12:23:45 PM » Author: Medved


I understand, but you still have more then one circuit in a home. And the rating of each device dictates how many of each can be on a circuit.

By going from 230 to 400, you need less home runs leaving the panel. Meaning if you had a 2,000 watt washer and 2,000 watt tumble dryer (just as an example) my choices are two 1.5mm2 10amp circuits or one 2.5mm2 20 amp circuit. But at 400volts, I only need one 1.5mm2 circuit. Both 230 volt options require more copper then the 400 volt option.

I have only one socket circuit (but it is a small apartment unit, built in the 60's), what I do not like most is by far not the power limit it imposes (I have all kitchen appliances include dish washer, cloth washer and dryer on the same, yet haven't faced any overload issues for more than 15 years I'm living here), but a single appliance problem at any place shutting down everything at once does make me thinking about finally to overhaul (well, not yet "maddened enough").
In fact the fault isolation is the main reason to split the installation among multiple circuits is the dominant "driving force" for many circuits and not the loading. Mainly the lighting circuits (which tend to use the minimum rating breakers on the market and a 1mm^2 cables for as low short circuit currents as possible) - to make a failing bulb more likely to trip just its own circuit so not to plunge whole home into darkness at once.
So even with 400V the number of circuits will stay, so no saving...
 


This is cultural issue unique to Britain. I don't think the government, code or electro standards should dictate anything outside of human safety and protection of property. A 3000 watt kettle isn't going to electrocute or burn down the property with proper isolation and thermal fusing.  

You forget one extra task: To not harm the grid reliability and the efficiency. Here belong all the EMC rules (power factor, harmonics), but as well things like load irregularity, when it becomes a problem e.g. due to the cultural reason. Any load variation means the electricity production becomes less efficient (with consequent excessive environmental impact vs the service it provides), even much worse when the changes are sudden and less accurately predicted. And becoming even worse with all the wind and mainly solar (speaking about Europe, with its geographical conditions) nonsense.

Of course, I would prefer this to be solved by the electricity becoming bloody expensive during those peak load (so many people would think twice to make the tea really at that moment and not a bit later), but that would require a lot of investment into the grid "becoming smart" (meters updating the rate based on the actual grid balance).
Beside of that the only option is to just startup more power plants power for such brief spikes (really wasting a lot of fuel) or making sure the equipment people are using does not cause these (=restricted power rating).
Yes, such restriction should ideally apply only to the countries where such problems are a real thing (so the tea kettles in the UK), but the "open market" means it has to be either everywhere or nowhere. That is why I would prefer the variable rate way (as a non UK, so I can enjoy the faster kettle here) - as that would be way more universal way for similar load distribution issues.



Certainly. Which is why the IEC does not recommend conductors under 1.5mm2 be used in building wiring. But still, any conductor can run either 100 devices or 170 devices based on the voltage.      

Well, if the reason for splitting is by far not the power but fault isolation, it wont go over 30 devices anyway, still being far below what power the 230V allows.
 

Not necessarily with an earthed star (Y) or center earthed source. Any one pole is going to interrupt 230 volts line to earth conductor. For a Line-Line fault both poles will share the arc about equally. Thus any 2 pole slash rated circuit breaker has to only take line to earth voltages into account.        

The most likely high current fault in present devices is across the inputs. Second is the fault from phase to ground.
For the first, either side interrupts first, takes the arc loading So making one side deliberately slower means you do not have to deal with an arc there.
For the second, any phase contact has to handle the full fat short circuit arc.

So with circuits between Phase and Neutral, just the phase contact needs "arc proofing" and the overcurrent triggers, so only one contact in the breaker.
With phase-phase connections both sides have to have both arc proofing, as well as overcurrent triggers, so way more expensive and complex.


Not necessarily. By having fewer circuits at 400 volts, you have fewer breakers at 400 volts. So instead of having 12 16amp single pole breakers, you have 7 16 amp double pole breakers. The cost increase is for only one extra double pole breaker in this example.

There won't be fewer circuits, because already today the power is not the driving factor for splitting to more circuits anymore, the separation is.

Come reality I doubt anything will change. But from a practical standpoint its worth considering. Remember that at one point most of the world was 110-127 volts only latter going to 220-230.  

The 120->230V change happened when the home power demand rose significantly due to the many appliances coming to daily use. Today the power demand per home is declining (no new high power appliances, the present ones have their power need reduced due to the efficiency improvements), so no such motivation exist anymore. Even in North America, where the power consumption per capita uses to be way higher, are no signs to even depart from the 120V (what Europe did nearly century ago), just because even there are no signs of need for higher power in a home.
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Re: 400 volts for power « Reply #6 on: June 15, 2019, 04:48:01 PM » Author: Keyless

I have only one socket circuit (but it is a small apartment unit, built in the 60's), what I do not like most is by far not the power limit it imposes (I have all kitchen appliances include dish washer, cloth washer and dryer on the same, yet haven't faced any overload issues for more than 15 years I'm living here), but a single appliance problem at any place shutting down everything at once does make me thinking about finally to overhaul (well, not yet "maddened enough").
In fact the fault isolation is the main reason to split the installation among multiple circuits is the dominant "driving force" for many circuits and not the loading. Mainly the lighting circuits (which tend to use the minimum rating breakers on the market and a 1mm^2 cables for as low short circuit currents as possible) - to make a failing bulb more likely to trip just its own circuit so not to plunge whole home into darkness at once.
So even with 400V the number of circuits will stay, so no saving...

 
No savings for a studio apartment. Try a 2,000sq foot home or better yet a school, mall, office building or high rise where a single floor may have in excess of 84 circuits.

You forget one extra task: To not harm the grid reliability and the efficiency. Here belong all the EMC rules (power factor, harmonics), but as well things like load irregularity, when it becomes a problem e.g. due to the cultural reason. Any load variation means the electricity production becomes less efficient (with consequent excessive environmental impact vs the service it provides), even much worse when the changes are sudden and less accurately predicted. And becoming even worse with all the wind and mainly solar (speaking about Europe, with its geographical conditions) nonsense.


I'll agree with solar and wind reducing critical clearing time among other things. But- I don't see kettles being that much of concern over all. Fault induced delayed voltage recovery from AC compressors is in orders of magnitude a greater risk IMO. 


Of course, I would prefer this to be solved by the electricity becoming bloody expensive during those peak load (so many people would think twice to make the tea really at that moment and not a bit later), but that would require a lot of investment into the grid "becoming smart" (meters updating the rate based on the actual grid balance).
Beside of that the only option is to just startup more power plants power for such brief spikes (really wasting a lot of fuel) or making sure the equipment people are using does not cause these (=restricted power rating).
Yes, such restriction should ideally apply only to the countries where such problems are a real thing (so the tea kettles in the UK), but the "open market" means it has to be either everywhere or nowhere. That is why I would prefer the variable rate way (as a non UK, so I can enjoy the faster kettle here) - as that would be way more universal way for similar load distribution issues.


I am deeply against restricting consumer goods in that way. Its the same idea that has lead to banning incandescent light bulbs. It looks good on paper, in the end its one more thing that ends up controlling people while creating a black market under the table. History has shown laws and restrictions only make things worse.   


Well, if the reason for splitting is by far not the power but fault isolation, it wont go over 30 devices anyway, still being far below what power the 230V allows.


Depends on the installation. If you have a store with 500 lights, 250 can go on one circuit 250 on another circuit in a checkerboard fashion. More scenarios call for splitting over power then everything going dark in terms of MWs consumed.   
 

The most likely high current fault in present devices is across the inputs. Second is the fault from phase to ground.
For the first, either side interrupts first, takes the arc loading So making one side deliberately slower means you do not have to deal with an arc there.
For the second, any phase contact has to handle the full fat short circuit arc.


It divides evenly. Take apart any 230/400Y 2 pole or 120/240 volt double pole breaker and the arc extinguishing mechanism is the same to that of a 230 volt or 120 volt breaker receptively. The 400 volt arc is shared across 2 poles essentially making the incident energy in each individual pole the same as a Line to ground fault.

So with circuits between Phase and Neutral, just the phase contact needs "arc proofing" and the overcurrent triggers, so only one contact in the breaker.
With phase-phase connections both sides have to have both arc proofing, as well as overcurrent triggers, so way more expensive and complex.



Its not way more expensive or significantly more complex. The price for a double pole MCB is about twice that of a single pole MCB. At least for me it is. A double pole MCB is simply two single pole MCBs with a tie and internal common trip bar.



There won't be fewer circuits, because already today the power is not the driving factor for splitting to more circuits anymore, the separation is.

Most places have more then two circuits. 

The 120->230V change happened when the home power demand rose significantly due to the many appliances coming to daily use. Today the power demand per home is declining (no new high power appliances, the present ones have their power need reduced due to the efficiency improvements), so no such motivation exist anymore. Even in North America, where the power consumption per capita uses to be way higher, are no signs to even depart from the 120V (what Europe did nearly century ago), just because even there are no signs of need for higher power in a home.


Try a 230 volt grill or kettle and the difference is night and day. I hate being limited to 1,800 watts, which is why I've treated myself to a few German appliances  Wink

But in any case the US is a horrific waste of copper and energy dealing with 120- but thats another story.

No matter what a 3 phase 3 wire system is much simpler then a 3 phase 4 wire system which is the point I am trying to make.     
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Re: 400 volts for power « Reply #7 on: June 16, 2019, 03:24:09 AM » Author: Medved


No savings for a studio apartment. Try a 2,000sq foot home or better yet a school, mall, office building or high rise where a single floor may have in excess of 84 circuits.

A single family home, regardless how large, wont still have more than a single stove, single washer and dryer or so. The only thing the larger will need higher power is the temperature management and that operates at all three phases (so 400V) anyway.
Mall is more an industrial installation.
Large apartment high rise has all units distributed across all phases, so effectively runs on 400V. And the number of circuit wont get reduced, as each apartment would need multiple circuits anyway. Because of the currents, the PEN busbar needs to be very thick there just for the PE function anyway (voltage drop during a short circuit), usually distributed among multiple channels (so the PEN connection gets redundancy), never heard about PEN problems with those conductor sizes.
Schools need a separate breaker for each class for fault isolation purpose, then the load within one such class is by far not that high (few 100's W for a computer and a projector), so again no benefit from higher voltage. Plus when distributed among the phases, the effective power delivery goes via 400V as well...


I'll agree with solar and wind reducing critical clearing time among other things. But- I don't see kettles being that much of concern over all. Fault induced delayed voltage recovery from AC compressors is in orders of magnitude a greater risk IMO. 

It is common for modern electronic thermostats to feature a random delay after power recovery to start the compressor (I won't be surprised it made it into the Codes as well, mainly for US market, where the AC is really everywhere; again a cultural thing...), just to make sure they won't start at once in the district after a power interruption there.
And with the kettles: Given the cultural environment in UK, it really is a problem there. It is indeed UK specific, but it is a problem for them.


I am deeply against restricting consumer goods in that way. Its the same idea that has lead to banning incandescent light bulbs. It looks good on paper, in the end its one more thing that ends up controlling people while creating a black market under the table. History has shown laws and restrictions only make things worse.

Well, you would be right, if the consumer would be really paying all the costs related to that. This is the main difference between incandescents vs high power tea kettles in UK:
The only thing the incandescents cause is high steady energy consumption. But it does not fluctuate, so easy to manage in the network, the related power generation could be very efficient, so the coal burned and CO2 release correspond just to the energy consumed. The users are billed for that, so indeed there is no other ground for further restriction.
The high power kettles in the UK are far different story: They cause very high load spike (for two minutes at once). In order to prevent network collapse, all generating equipment has to be ready to kick in in advance and able to deliver the power spike for that two minutes. But that means the coal burned corresponds not only to the two minutes of real delivery, but to all the time needed to "warm up" the equipment, so many times more. The problem is, nobody is actually paying for that extra coal consumption and related environmental impact, so it gets distributed over all customers, include those who do not cause such demand spike, quite unfair.
Agree, the true solution would be to let all the "tea makers" really pay for all that (if they want that tea just at that moment, they have to bear all it costs, that only would be fair). But that means really smart metering has to be installed. A simpler way is to restrict the power rating, so reduce the peak power and prolong the time, so make the extra costs (both financial, as well as environmental impact) related to that spike lower (diluting the spike from 2 to 3 minutes already means 50% savings on those extra costs). Yes, hurts those who do not cause the problem (longer wait time), so that is why this regulation should be limited to really where the problem is and only till it gets solved by e.g. the smart metering. But short term there is not much other UK may do to reduce that waste.


It divides evenly. Take apart any 230/400Y 2 pole or 120/240 volt double pole breaker and the arc extinguishing mechanism is the same to that of a 230 volt or 120 volt breaker receptively. The 400 volt arc is shared across 2 poles essentially making the incident energy in each individual pole the same as a Line to ground fault.

Well, in a fictional world where both contacts move exactly at the same time, yes. But the real world has tolerances and that means one contact would always be faster and that would be the one taking all the load, because the second would disconnect without any or with already very reduced current.
Two pole MCBs are sometimes made as two single pole MCBs with just a trigger interlink, so indeed cost twice a single pole breaker.
But an use on a single phase to N allows the N contact to be made way smaller, so the overall assembly could be made just a bit more expensive than a single pole breaker, so way cheaper than the full two pole system you need for phase-phase circuits. In fact in this way are made many "single module" RCD/MCB combos (that is, what I would use in any home wiring, instead of a common RCD and then many MCBs as many do in an attempt to lower the costs - then a single fault tripping the RCD plunges the whole house into darkness, completely defeating the main purpose of the "many circuit" arrangement)



But in any case the US is a horrific waste of copper and energy dealing with 120- but thats another story.

Well, actually the US system uses less copper/aluminum.
The key difference is, the "last mile" (so from the substation to your property border) in Europe is carried directly on the 3x230/400V level (then directly feeding the sockets), so needs to be sized accordingly. Here we are talking about 1..2km of cable.
On the other hand the US installations uses 5..15kV for that "last mile", so way thinner wiring with less material and serving more customers, then on the border of your property is a transformer turning that to the 2x120/240V going to your sockets.

So yes, US needs larger cross sections for the final 2x120/240V, but only for some 100m or so,
while Europe needs a bit thinner wires, but for 1..2km runs.
Again, I'm speaking about residential installations. Bigger commercial buildings tend to have their own "property border" 22kV->3x230/400V transformers even in Europe, but that is more an industrial installation.
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Re: 400 volts for power « Reply #8 on: June 16, 2019, 04:46:40 AM » Author: Roi_hartmann


Well, actually the US system uses less copper/aluminum.
The key difference is, the "last mile" (so from the substation to your property border) in Europe is carried directly on the 3x230/400V level (then directly feeding the sockets), so needs to be sized accordingly. Here we are talking about 1..2km of cable.
On the other hand the US installations uses 5..15kV for that "last mile", so way thinner wiring with less material and serving more customers, then on the border of your property is a transformer turning that to the 2x120/240V going to your sockets.

So yes, US needs larger cross sections for the final 2x120/240V, but only for some 100m or so,
while Europe needs a bit thinner wires, but for 1..2km runs.
Again, I'm speaking about residential installations. Bigger commercial buildings tend to have their own "property border" 22kV->3x230/400V transformers even in Europe, but that is more an industrial installation.

How is the amount of copper needed for transformers in these two installation styles? European one large transformer feeding multiple houses vs US many smaller transformer each feeding just a house or two.
« Last Edit: June 16, 2019, 04:55:45 AM by Roi_hartmann » Logged

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Re: 400 volts for power « Reply #9 on: June 16, 2019, 05:32:49 AM » Author: Medved
How is the amount of copper needed for transformers in these two installation styles? European one large transformer feeding multiple houses vs US many smaller transformer each feeding just a house or two.

That is not that much: The total transformer wights some 100kg or so, include the core, case and oil fill.
They usually use copper only for the rather thin primary, the thick secondary is usually made of sheet aluminum.
We are talking about just 5..10kW, it is not that much.
Well, even the poles wont be able to support much more, when there use to be 2..3 "cans" hanging on a single pole...

But it is system tailored for the US geography, mainly the long distances of the "last mile" (in the range of 10km or so).
The European much denser population make the "last mile" way shorter (virtually all below 1..2km), so easier to serve by directly the final socket voltage.
I think these aspect played significcant role in the mains specifications evolution in the past:
The long distances in the US mean the need for the customer point final transformer. That lead to use of more convenient lower voltage for the inhouse installation (mainly the higher efficacy and reliability of incandescents), the higher number of transformers made then the higher optimum frequency of 60Hz (allows smaller, so lighter and cheaper transformers for the same power and losses).
The higher population density in Europe meant it made sense to use larger HV/socket voltage transformers serving more people, with the "last miles" fed on the final "socket voltage". Because of the high currents there, it was beneficial to use lower frequency (50Hz), to limit reactance related parasitics in the wiring. And to not have these current that high, it made more sense to move to higher voltage, the 3x230/400V was the maximum manageable for common loads like incandescents (even though these were of lower efficacy than the 120V ones), still manageable for fusing, etc.
Today the standards are set, the potential benefit from switching to another one are so little if any it does not make sense to switch.

If something is going to alter some standards, it is the spread of the local power generation and mainly storage in the near future. Because the only low power (below MWh range) storage technologies we have are based on electrochemical batteries, as well as the solar generation are inherently DC, as well as most modern appliances are internally using DC too (induction stoves, direct drive washers, VFD AC compressors, all IT equipment,...) it may make sense in the future to get rid of the many conversions required and distribute directly the DC. But I don't think this is going to happen any time sooner than when these local generation/storage things will really be in wide spread use. So decades from now in the fastest scenario... Today this trend happens only when someone needs battery backup for some home systems (gas or wood burning heater auxiliaries), then the lighting (its power gets so small it allows it) is glued on that and so installed as 12V or 24V DC direct battery voltage...
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Re: 400 volts for power « Reply #10 on: June 16, 2019, 11:11:00 AM » Author: Keyless

A single family home, regardless how large, wont still have more than a single stove, single washer and dryer or so. The only thing the larger will need higher power is the temperature management and that operates at all three phases (so 400V) anyway.


Right, so, you would need more then once circuit even at 400 volts. Thus you will not be running more circuits solely upon fear of loosing the entire home.   




Mall is more an industrial installation.
Large apartment high rise has all units distributed across all phases, so effectively runs on 400V. And the number of circuit wont get reduced, as each apartment would need multiple circuits anyway.


And what factor would force the same number of circuits when a 16 amp 3,680 watt circuit now becomes a 6,400 watt circuit? A fuse board with 6 circuits and 6 single pole breakers will now have 3 circuits and 3 double pole breakers roughly. 



Because of the currents, the PEN busbar needs to be very thick there just for the PE function anyway (voltage drop during a short circuit), usually distributed among multiple channels (so the PEN connection gets redundancy), never heard about PEN problems with those conductor sizes.
Schools need a separate breaker for each class for fault isolation purpose, then the load within one such class is by far not that high (few 100's W for a computer and a projector), so again no benefit from higher voltage. Plus when distributed among the phases, the effective power delivery goes via 400V as well...



What code section requires each class room to have a dedicated circuit? The NEC and BS7671 does not care. I am on the side of any code which does not restrict the number of outlets or rooms on a circuit. Canada has that limit as well as France, very dumb if you ask me.   


It is common for modern electronic thermostats to feature a random delay after power recovery to start the compressor (I won't be surprised it made it into the Codes as well, mainly for US market, where the AC is really everywhere; again a cultural thing...), just to make sure they won't start at once in the district after a power interruption there.
And with the kettles: Given the cultural environment in UK, it really is a problem there. It is indeed UK specific, but it is a problem for them.


Some ACs do have brown out protection, but beyond that if someone wants a 3000 watt kettle or grill they should have it.   

Well, you would be right, if the consumer would be really paying all the costs related to that. This is the main difference between incandescents vs high power tea kettles in UK:
The only thing the incandescents cause is high steady energy consumption. But it does not fluctuate, so easy to manage in the network, the related power generation could be very efficient, so the coal burned and CO2 release correspond just to the energy consumed. The users are billed for that, so indeed there is no other ground for further restriction.
The high power kettles in the UK are far different story: They cause very high load spike (for two minutes at once). In order to prevent network collapse, all generating equipment has to be ready to kick in in advance and able to deliver the power spike for that two minutes. But that means the coal burned corresponds not only to the two minutes of real delivery, but to all the time needed to "warm up" the equipment, so many times more. The problem is, nobody is actually paying for that extra coal consumption and related environmental impact, so it gets distributed over all customers, include those who do not cause such demand spike, quite unfair.
Agree, the true solution would be to let all the "tea makers" really pay for all that (if they want that tea just at that moment, they have to bear all it costs, that only would be fair). But that means really smart metering has to be installed. A simpler way is to restrict the power rating, so reduce the peak power and prolong the time, so make the extra costs (both financial, as well as environmental impact) related to that spike lower (diluting the spike from 2 to 3 minutes already means 50% savings on those extra costs). Yes, hurts those who do not cause the problem (longer wait time), so that is why this regulation should be limited to really where the problem is and only till it gets solved by e.g. the smart metering. But short term there is not much other UK may do to reduce that waste.



Still seems silly to reduce the wattage of kettles over something that may change anyways down the road in terms of the culture of kettle use or the available reserve capacity like pumped storage or ultra caps. 



Well, in a fictional world where both contacts move exactly at the same time, yes. But the real world has tolerances and that means one contact would always be faster and that would be the one taking all the load, because the second would disconnect without any or with already very reduced current.
Two pole MCBs are sometimes made as two single pole MCBs with just a trigger interlink, so indeed cost twice a single pole breaker.


But it doesn't stop manufacturers from turning single pole breakers into double pole breakers more often then not.


But an use on a single phase to N allows the N contact to be made way smaller, so the overall assembly could be made just a bit more expensive than a single pole breaker, so way cheaper than the full two pole system you need for phase-phase circuits. In fact in this way are made many "single module" RCD/MCB combos (that is, what I would use in any home wiring, instead of a common RCD and then many MCBs as many do in an attempt to lower the costs - then a single fault tripping the RCD plunges the whole house into darkness, completely defeating the main purpose of the "many circuit" arrangement)


But think, why do we do this? Why switch the neutral? Is it because the neutral can break? Causing it to become live? If the fear of an energized neutral is so high, why not the over voltage associated with a broken neutral in a 3 phase system? An open neutral is a fire hazard and the cost it can create is substantial.   


Well, actually the US system uses less copper/aluminum.
The key difference is, the "last mile" (so from the substation to your property border) in Europe is carried directly on the 3x230/400V level (then directly feeding the sockets), so needs to be sized accordingly. Here we are talking about 1..2km of cable.
On the other hand the US installations uses 5..15kV for that "last mile", so way thinner wiring with less material and serving more customers, then on the border of your property is a transformer turning that to the 2x120/240V going to your sockets.


And what is done overhead on the NESC side is COMPLETELY offset by what happens on the NEC side. Every single installation uses at least 3-14 times more copper, even at 277/480.


Its not just the lower voltage, but the ampacity restrictions, 80% rule and load calcs for services which force every comparable installation to use substantially more copper and/or aluminum.

A few simple cases:


1.5mm2 is typically rated 16amps and is allowed higher when clipped direct. In the US a 15 amp circuit must use 2.08mm2 (despite using 90*C insulation) regardless of the installation method. 2.5mm2 is typically good for 20amps in Europe. In the US 3.31mm2 is required. Where 4mm2 would work 5.26 is required in the NEC. This goes on for every wire size.


In the UK a 4,500 watt water heater can use 2.5mm2 cable in contact with insulation or 1.5mm2 clipped direct. In the US, code would require 3.31mm2, but because the NEC wants 150 gallon and under water heaters to be considered a continuous load the breaker must be sized at 30amps and the circuit wired in 5.26mm2. 1.5 vs 5.26...  Embarrassed


Aside from the continuous rule requiring feeders and branch circuits sized at 125% of the already restricted ampacities you have load calcs which really take things to the extreme. Services and feeders that will never be loaded to more then 60amps end up being 225 amps. Where a 1000amp main will do code forces a 3000 or 4000amp main along with the conductors to support 3000 or 4000amps.




So yes, US needs larger cross sections for the final 2x120/240V, but only for some 100m or so,
while Europe needs a bit thinner wires, but for 1..2km runs.
Again, I'm speaking about residential installations. Bigger commercial buildings tend to have their own "property border" 22kV->3x230/400V transformers even in Europe, but that is more an industrial installation.



Bigger installations tend to be fed with 277/480, but you have 480-120/208Y transformers all over the place which waste energy and copper considering how over sized code makes them.


Trust me, the US is addicted to copper and aluminum lol.
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Re: 400 volts for power « Reply #11 on: June 16, 2019, 11:35:48 AM » Author: Keyless
That is not that much: The total transformer wights some 100kg or so, include the core, case and oil fill.
They usually use copper only for the rather thin primary, the thick secondary is usually made of sheet aluminum.
We are talking about just 5..10kW, it is not that much.
Well, even the poles wont be able to support much more, when there use to be 2..3 "cans" hanging on a single pole...


True, and correct about the secondary typically being AL.


But it is system tailored for the US geography, mainly the long distances of the "last mile" (in the range of 10km or so).
The European much denser population make the "last mile" way shorter (virtually all below 1..2km), so easier to serve by directly the final socket voltage.
I think these aspect played significcant role in the mains specifications evolution in the past:
The long distances in the US mean the need for the customer point final transformer. That lead to use of more convenient lower voltage for the inhouse installation (mainly the higher efficacy and reliability of incandescents), the higher number of transformers made then the higher optimum frequency of 60Hz (allows smaller, so lighter and cheaper transformers for the same power and losses).




Which is offset by the cyclic loading of those transformers. Because homes typically draw only a few amps during the day and several killo watts for about an hour or two when residents come home pole pigs often swing from little load to a 200 to 300% overload. The over load is done to economize the transformer when subjected to cyclic loading with the thermal inertia of the oil protecting the windings from over heating. But in the end you have thousands of transformers that never realize efficient loading. Energy wasted keeping them practically magnetized then driven in a state where they are essentially a heater.


With 230/400Y however the secondaries can travel 4x the distance and various voltage systems can be ignored (ie a restaurant needing 120/208 while the home across the street wants 120/240) This allows a greater diversity of costumer load and types. Meaning you can mix a business with many homes on a single transformer or bank leading to substantially more steady loading. Instead of a 300% over load, your talking about a 125% peak overload or even a 105% peak over load.         



The higher population density in Europe meant it made sense to use larger HV/socket voltage transformers serving more people, with the "last miles" fed on the final "socket voltage". Because of the high currents there, it was beneficial to use lower frequency (50Hz), to limit reactance related parasitics in the wiring. And to not have these current that high, it made more sense to move to higher voltage, the 3x230/400V was the maximum manageable for common loads like incandescents (even though these were of lower efficacy than the 120V ones), still manageable for fusing, etc.

I don't think 50 or 60HZ has much to do with that. Maybe I'm wrong. 

Today the standards are set, the potential benefit from switching to another one are so little if any it does not make sense to switch.

Didn't stop the Phillipines from doing it.


If something is going to alter some standards, it is the spread of the local power generation and mainly storage in the near future. Because the only low power (below MWh range) storage technologies we have are based on electrochemical batteries, as well as the solar generation are inherently DC, as well as most modern appliances are internally using DC too (induction stoves, direct drive washers, VFD AC compressors, all IT equipment,...) it may make sense in the future to get rid of the many conversions required and distribute directly the DC. But I don't think this is going to happen any time sooner than when these local generation/storage things will really be in wide spread use. So decades from now in the fastest scenario... Today this trend happens only when someone needs battery backup for some home systems (gas or wood burning heater auxiliaries), then the lighting (its power gets so small it allows it) is glued on that and so installed as 12V or 24V DC direct battery voltage...

Yes, but you still have Chillers, electric cars, ect need more then 12 or 24 volts. 
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Re: 400 volts for power « Reply #12 on: June 16, 2019, 11:18:13 PM » Author: Medved
Yes, but you still have Chillers, electric cars, ect need more then 12 or 24 volts. 

The 12 or 24V is, what is used today for lighting and heating control and circulation pump backup only. So not much above about 100..200W in total.

If the battery would be part of the main energy use pattern, it will definitaly have larger voltage, to support tzese higher loads.
The car charger will be most likely fixed installation, just because of the power involved.



The 60 vs 50 Hz plays very significant difference: It is about 40% transformer mass difference for the same losses.
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Re: 400 volts for power « Reply #13 on: June 19, 2019, 06:22:14 AM » Author: Keyless
Not 18% difference? Maybe I'm wrong.



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Re: 400 volts for power « Reply #14 on: June 19, 2019, 01:28:28 PM » Author: Medved
Not 18% difference? Maybe I'm wrong.

Assume 50 vs 60 is 20% (depends wha is the reference but that was not your point I guess).

So the same core could use 20% less turns.
When for the start assuming the same wire, it means 20% shorter, so 20% lower resistance, so 20% lower losses.
But that means 20% less wire in the winding window. So you may fit 20% thicker wire instead.
And that is the other 20% lower losses for the same core, so total "40%".
Well, it could mean about the same ratio smaller core when keeping the losses.
Well, to be exact (5/6)^2, agree the "40%" was a bit too much of rounding...
And the real life brings another caveat: The smaller core can not dissipate the same losses, so actually it should be designed for lower losses to keep the temperature equal with the same cooling technology. So in reality the core wont be that small, but still the savings is significant...
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