Anyone know why voltage 120/240 is referred to as 110/220

[kwired]

I thought 110 came bc it's alternating current and you could read 110,115,118 etc

I don't understand what you're getting at here. WE could easily have same voltages with DC.

 

[Besoeker]

Ok Im back:lol:

Once the conversion is finalized you could if we decided to feed resi with 240/415Y, which you be 3 or 4 times more efficient than a center tap. However I would really recommended a device to detect open neutrals since it is a real issue few power experts are willing to address. I know Im a safety freak:ashamed1:

Withe the 230V single phase that serves residential in UK, an open neutral means loss of supply. Sure, it leaves live live and that could be a potential risk if someone thought the absence of a supply meant absence of electrocution risk. But, unlike the 120-0-120 lost neutral, the possibility of applying up to double voltage to circuits doesn't exist.

But efficiency aside I think its safer to have 120 to ground instead of 240. Resi would be that in my world while commercial with qualified people would be 240/415Y.

Well, I wouldn't wish to be bitten by any of them.

Just wondering, don't EU job sights require an isolation transformer that's center tapped for 120-0-120 in case someone get a shock?

Some sites specify not more than 110V for portable tools. I haven't come across any that require 120-0-120.
My guys have a bunch of 230/110 isolation transformers.
They are infrequently used these days. Portable tools have gone battery powered.
Today, I fitted up the bits for my new weather station. Temperature, pressure, humidity, and rain gauge.
Just hand tools plus my electric screwdriver.

 

[mbrooke]

Why you think 240 is more efficient than 120/240? Especially 3 or 4 times more efficient?

Watts is still watts. If the 120 volt loads are relatively balanced you don't really have much for line loss on feeders or service conductors either as the line losses are essentially about the same as they would be if the same load were connected to straight 240 volts. Only the line losses from the imbalance flowing on the neutral is extra inefficiency.

240 allows for 3 phase 240/415Y, where as 120/240 is just that. 3 phase alone is more efficient, couple that with a higher voltage and its a win win for efficiency. 3 100 amp loads of 240 would mean 100amp and say #2 cu conductor. 100 amps of 240 single phase would mean 300 amps per 2 wires (400mcm cu) or 173 amps 3/0 cu on a 3 phase connected in delta. Plus the distance would need to be halved to reduce voltage drop.

 

[mbrooke]

Besoeker;1535352]Withe the 230V single phase that serves residential in UK, an open neutral means loss of supply. Sure, it leaves live live and that could be a potential risk if someone thought the absence of a supply meant absence of electrocution risk. But, unlike the 120-0-120 lost neutral, the possibility of applying up to double voltage to circuits doesn't exist.


But isn't the utility supply transformer (Dy11) a 3 phase unit with the single phase derived from it? If the pole neutral broke it could happen?

 

[AdrianWint]

Just wondering, don't EU job sights require an isolation transformer that's center tapped for 120-0-120 in case someone get a shock?

Not quite. Its actually 110V but arranged 55-0-55 with the centre point earthed thus making the L-G voltage at the hand tool to be 55V. This is only on the larger 'commercial' construction sites and only applies to hand held tools & lighting.

There is a common misconception here that this is the 'American Standard' and is at least part of the reason why us Brits think the States is 110V .............

Adrian

 

[AdrianWint]

Besoeker;1535352]Withe the 230V single phase that serves residential in UK, an open neutral means loss of supply. Sure, it leaves live live and that could be a potential risk if someone thought the absence of a supply meant absence of electrocution risk. But, unlike the 120-0-120 lost neutral, the possibility of applying up to double voltage to circuits doesn't exist.


But isn't the utility supply transformer (Dy11) a 3 phase unit with the single phase derived from it? If the pole neutral broke it could happen?

Yes, we do get our single phase supplies as one phase leg & neutral from a 3 phase TX. Steps have been taken in the design of the distribution system to try to prevent an open circuit neutral from occurring but, yes, if it is does the end result is that two residences can become effectively connected in series across a 400V supply. Its also possible that the load provided by three residences (one per phase) will almost balance & an artificial star point will be created with minimal shift of the N-G voltage. This can be hard to detect if the voltage shift is minimal but will change as the load in each residence varies.

One way that is used to help mitigate this is PME (protective multiple earthing). Here the supply neutral is grounded at many points along its path & at each residence. This is done by the DNO (Distribution network operator).

Adrian

 

[kwired]

240 allows for 3 phase 240/415Y, where as 120/240 is just that. 3 phase alone is more efficient, couple that with a higher voltage and its a win win for efficiency. 3 100 amp loads of 240 would mean 100amp and say #2 cu conductor. 100 amps of 240 single phase would mean 300 amps per 2 wires (400mcm cu) or 173 amps 3/0 cu on a 3 phase connected in delta. Plus the distance would need to be halved to reduce voltage drop.

That makes equipment cost less, inefficiency means energy is being consumed but is not being consumed directly by the intended load. Voltage drop gives up heat in conductors but can be reduced by using larger conductors, which becomes an equipment cost and not an cost because of energy efficiency.

Besides if we had no need for 120 volts like we do now we wouldn't have 120/240 or 208/120 systems, but all that means is a little different winding configuration of a transformer. There would likely still be 240 volt single phase transformers for isolated single phase services, and most three phase systems or areas with multiple single phase services would still utilize the 240/415Y systems.

I could also still (depending on how primary distribution is done) see an occasional open delta system in remote areas just for purposes of reducing installation costs.

Besoeker;1535352]Withe the 230V single phase that serves residential in UK, an open neutral means loss of supply. Sure, it leaves live live and that could be a potential risk if someone thought the absence of a supply meant absence of electrocution risk. But, unlike the 120-0-120 lost neutral, the possibility of applying up to double voltage to circuits doesn't exist.


But isn't the utility supply transformer (Dy11) a 3 phase unit with the single phase derived from it? If the pole neutral broke it could happen?

You still have less potential points of failure that will have such a wide range of impact on voltage delivered to loads. We could have similar results with what we do now by running separate neutral for each phase everywhere beyond the X0 point of the transformer, but that raises the installation costs.

Not quite. Its actually 110V but arranged 55-0-55 with the centre point earthed thus making the L-G voltage at the hand tool to be 55V. This is only on the larger 'commercial' construction sites and only applies to hand held tools & lighting.

There is a common misconception here that this is the 'American Standard' and is at least part of the reason why us Brits think the States is 110V .............

Adrian

So do construction companies that work on larger projects have two sets of electric powered equipment? One set they use on larger sites where 110 volts is all that is available, and their 240 volt equipment that they use most everywhere else?

Here they want 120 volt equipment with 15 or 20 amp cord connectors for almost everything, the idea is it will work almost anywhere they go. Problem is there are some heavier load tools/equipment that do have 15 or 20 amp 120 volt cord connectors that really would be better off with either a higher amp rated cord connector and corresponding higher rated supply circuit or else designed for 240 volts, but that means getting "special" outlets installed before they can use them, or get someone that thinks they know electricity to make it work somehow.

 

[Besoeker]

Not quite. Its actually 110V but arranged 55-0-55 with the centre point earthed thus making the L-G voltage at the hand tool to be 55V. This is only on the larger 'commercial' construction sites and only applies to hand held tools & lighting.

Reminds me of a story.
A fellow I knew stole an electric drill from a building site close to his house. He tried it and, not surprisingly the commutator put up a performance that would have been more appropriate to 5th November than a hand-held tool.
He brought to be to look at.
"Um, it's 110V, squire."
"What does that mean?"
"You need a transformer if you want to run from your mains supply."
"Oh."

The next day he came back with the transformer.
He'd only been back to the site and nicked the transformer as well.............

I told him in no uncertain terms to take it away and in no circumstances did I want to clap eyes on it ever again.

 

[mbrooke]

Yes, we do get our single phase supplies as one phase leg & neutral from a 3 phase TX. Steps have been taken in the design of the distribution system to try to prevent an open circuit neutral from occurring but, yes, if it is does the end result is that two residences can become effectively connected in series across a 400V supply. Its also possible that the load provided by three residences (one per phase) will almost balance & an artificial star point will be created with minimal shift of the N-G voltage. This can be hard to detect if the voltage shift is minimal but will change as the load in each residence varies.

One way that is used to help mitigate this is PME (protective multiple earthing). Here the supply neutral is grounded at many points along its path & at each residence. This is done by the DNO (Distribution network operator).

Adrian

Ok I get it now. Are most systems in Britain TN-C-S Or is there TN-S also? PME is similar to our multi grounded neutral system. Every transformer pole has a ground rod as well as other spans. Once the service in the US comes out of the meter at the first disconnect (usually in the main panel) the ground and neutral split, with a ground wire going to 1 or 2 ground rods. Another wire runs over to bond the plumbing pipe coming into the residence.

I am not a fan of TN-CS systems being used even though they are very common since a current carrying conductor becomes parallel with the earth. (see pic, I apologize for the differing language) Lots of different issues come up with MEN/MGN earthing.

That makes equipment cost less, inefficiency means energy is being consumed but is not being consumed directly by the intended load. Voltage drop gives up heat in conductors but can be reduced by using larger conductors, which becomes an equipment cost and not an cost because of energy efficiency.

Besides if we had no need for 120 volts like we do now we wouldn't have 120/240 or 208/120 systems, but all that means is a little different winding configuration of a transformer. There would likely still be 240 volt single phase transformers for isolated single phase services, and most three phase systems or areas with multiple single phase services would still utilize the 240/415Y systems.

I could also still (depending on how primary distribution is done) see an occasional open delta system in remote areas just for purposes of reducing installation costs.

You still have less potential points of failure that will have such a wide range of impact on voltage delivered to loads. We could have similar results with what we do now by running separate neutral for each phase everywhere beyond the X0 point of the transformer, but that raises the installation costs.

So do construction companies that work on larger projects have two sets of electric powered equipment? One set they use on larger sites where 110 volts is all that is available, and their 240 volt equipment that they use most everywhere else?

Here they want 120 volt equipment with 15 or 20 amp cord connectors for almost everything, the idea is it will work almost anywhere they go. Problem is there are some heavier load tools/equipment that do have 15 or 20 amp 120 volt cord connectors that really would be better off with either a higher amp rated cord connector and corresponding higher rated supply circuit or else designed for 240 volts, but that means getting "special" outlets installed before they can use them, or get someone that thinks they know electricity to make it work somehow.

I agree. I was thinking more on efficiency ease, but truth is if a utility decides to use #2 al on open spool racks for a 200 amp system while running it to the point voltage drop is 20% then it would compare to the efficiency of straight 240. If homes in the use were indeed 240 or say single phase 300, utilities would always connect those homes in wye since no matter the voltage wye is always the cheaper deal. Thinner wires plus longer runs are permitted or fewer transformers per street, however the savings are applied.

 

[Besoeker]

Ok I get it now. Are most systems in Britain TN-C-S Or is there TN-S also?

The TN-S system is also listed in BS7671.

I don't know which is more commonly used.
Installation isn't my bag.
Adrian might know.

 

[mbrooke]

The TN-S system is also listed in BS7671.

I don't know which is more commonly used.
Installation isn't my bag.
Adrian might know.

Don't sweat it. I know a lot about installs, but if someone wanted me to trouble shot a variable frequency motor drive or program logic PLC I wouldn't know where to begin:dunce:


Would this be the real BS7671 or is it a fake?:http://www.thailandlift.org/documents/BS7671-2008.pdf