Alternating current & neutral wire

[willawake]

Re: Alternating current & neutral wire



its mostly schuko here (German)

[starfury1]

Re: Alternating current & neutral wire

All my before posts were based on the Australian system were we use
a a single phase (mostly) to homes.
(not sure but this maybe changing now but thats another story)

This could result in some confusion for USA and Canada readers
which I have since found out use a rather unique and interesting delivery system
(and others like me of their system...confusion)

Its called Single Phase 3 wire or Split Phase * system (*not good to use cause it can be confused with motors)

They do in fact have 240 Volts Available but its designed so they have the best of both worlds
Either 120VAC or 240VAC. depending on the current demands of the devices used, this also somewhat increases the safety aspects by having a lower more generally used voltage of 120VAC for lower powered devices

Hows it Done?

The Key is that the last step down transformer secondary, rather then just use one side as Active and call the other Neutral and tie it to Earth

Its is center tapped.

The center tap then becomes the Neutral (which gets tied to earth)
and you end up with effectively 2 ACTIVE lines from either end of the secondary winding.

like the following.



it is used else were in the world but on a more limited basis

It does result in 2 Actives running in opposite directions so some wrongly think of it as 2 phases, its not
(there was in time passed a 2 phase system which I think helps add to the confusion)

some links

Split phase

The more interesting bit is near the bottom of the page (below)

Single Phase power systems

On Shared neutral

if you think carefully about it with the 2 Actives
they are going at the same Rate of change in an equal but opposite directions with respect to each other
Now with respect to the Neutral even though heading in opposite directions they are at the same point in their cycle so are in phase.

I think a trap to watch out for is the colours used too....Red and Black are Actives and white is Neutral

(So dont make the mistake of thinking a Black wire in the USA or Canada is neutral..its not...ditto if you are in OZ dont make the mistake in thinking white is Neutral its not...its a Switched Active or a Phase 240VAC wire)

So you Have
120VAC "A + Red" Active
120VAC " B - Black" Active

with respect to Neutral (White)

240 VAC between the Red Active and Black Active,
Active to Active is 240 VAC


So if someone mentions in a post about red active A active or + Active etc and they are from the USA or Canada you will know what they are talking about.

HTH

Cheers

[Per Hansson]

Re: Alternating current & neutral wire

starfury1; aren't the two system quite equal?

I mean, in "the world" we have 230v AC when we connect something to neutral/ground
And we get 460v when we connect two phases together...

In the US it's the same just lower voltages and different frequencies?

[starfury1]

Re: Alternating current & neutral wire

in Answer Yes if you use a Split phase system, but here I dont think its used at all

starfury1; aren't the two system quite equal?

I mean, in "the world" we have 230v AC when we connect something to neutral/ground
And we get 460v when we connect two phases together...

In the US it's the same just lower voltages and different frequencies?

not sure on your neck of the woods Per
but as far as I am aware, here its 240 VAC (NOW 230 Volts nominal) single phase buddy, thats all you get unless they bring another phase line to the house.

it was 415 Volts AC between phases here so its from a 3 phase system
(not a split winding) with 120 degree phase shift. (phase to phase)
(it wont be quite that now we have changed to 230 VAC)

You system may use a single phase (split winding) like the US
I dont know, it is used in Eroupe according to the the diagram and the info but I have no idea to what extent.

I don't think its used at all here but I could be wrong...not the Guru on world power delivery systems.

It was enough to add confusion to the mix which is why I posted it so people would be aware...its sounding like we are the "odd man out" if you get what mean LOL

anyway may have put this link up before but here it is again wiki

http://en.wikipedia.org/wiki/Three-phase_electric_power

another site I found that may be worth having a look around
(although its one of those take your slide rule with you)

http://www.physclips.unsw.edu.au/jw/power.html

there is some related stuff that might be of interest, have a browse around



from the Gov site

http://internet.aca.gov.au/WEB/STANDARD/pc=PC_1988#

power System

Australia uses a four wire, three phase, 240/415 volt, multiple earthed neutral (MEN) distribution system. There is no inherent overvoltage level protection and additional protection in equipment may be required. However, three phase 415 volt system is generally considered to be Category III level whilst single phase, 240 volt general purpose outlets are considered to be Category II; (see International Electrotechnical Commission standard, IEC 60664 for definitions)
Frequency is 50 Hertz

Hope that makes sense to somebody

Like I said the exact details of how its all done is quite involved...it was really meant to give people a grasp of the idea ..the details on how its done you will have to search out for whatever country you live in.

Cheers

[davmax]

Re: Alternating current & neutral wire

Sorry Starfury1. Your comparison of 230/460VAC system with the American system is not correct , it is way off. The American system is a single phase 240VAC with a centre tap taken to neutral, and neutral is typically connected to ground so that maximum voltage to ground is 120VAC.
The system in Australia and and other parts of the world is based on a three phase generation. Each phase is seperated by 120 degrees phase angle and each is 230VAC above ground. The voltage across any two phases in 440VAC , not twice the voltage because of the phase reslationship. Many dwellings are supplied one phase only ie 230VAC, the street wiring is most often three phase and different dwellings are connected to different phases to spread the load. Major buildings/factories are supplied with three phases for motors that can utilise the benefit of three phasepower. The single wire colours in Australia are: RED = active, BLACK = Neutral and GREEN/YELLOW striped = Earth. Typically as in the US the neutral in a building is tied to ground at one point only, insuring no voltage is higher than 230VAC above ground. Three phase wire colours are RED, YELLOW and BLUE as seen on three phase equipment. We in Australia follow the UK standard.
Link: http://www.3phasepower.org/3phasewiring.htm

Just seen your latest post. That is much better.

[starfury1]

Re: Alternating current & neutral wire

Yes the first one was to make the point the USA/Canada is done differently
Since all my older posts were based on our system
(3 phase, or rather a single phase of ours with reference to neutral)

The idea was to make people aware of this fact...that it is done differently cause of the confusion that might arise from it.

I didn't touch much on our system at all in it.

The second post was in answer to Per question and it would be yes "IF" they use a split phase system.

It does mention Europe on the Diagram and I thought I did find a mention to the UK in limited use in out laying (like farmland)

In the UK and Europe, 230/460 V, 3-wire, single-phase systems are used to run farms and small groups of houses when only two of the three-phase high voltage conductors are available

Here in Australia I understand we would use SWER (Single Wire Earth Return) system and dont think that an isolated farm house would be the only thing that runs that way...there are towns more like cities that have this method of power delivery

http://en.wikipedia.org/wiki/Single_wire_earth_return

OK I could be wrong (to a point) that its not used here
have a look at this in that system




==========================================================

My assumption was that our 3 phase system is like the rest of the world but there is mention of a split phase system being used in a limited way else were outside of the USA/Canada so you would actually have to check your area yourself to be sure of exactly how the grid is being distributed to you.

Thanks Davmax That sums up our system nicely.

Thanks for the link too, I actually had that one ready to put in and lost it...(too many pages open in browser)

just on the colour thing it was a bit tounge in cheek, saying never trust the colour to be what you think it is!

Err just one thing I thought yellow was changed to white?.
(maybe it was the other way?)


Now since I can't edit the above posts to make it clearer


MY POST ABOVE with "Diagram" is purely in REFERENCE to the USA\CANADA SYSTEM.

The one after is in answer to Pers Question and on the 3 PHASE system used in Australia and (mostly) the rest of the world

Per just so we got it right you are correct "IF" it is a single phase 3 wire (Split phase) System

Mostly the world is 3 PHASE so no it would be incorrect if was 3 phase system as Davmax said and I said above

120 deg phase shift will result in a different voltage level between the phases.
(you will find the maths in those links somewhere I am sure)


As I said the reality of the whole thing can get very complex.

So you really need to check locally of exactly what goes on with your power in your area.

Hope this is a bit clearer

Cheers

[davmax]

Re: Alternating current & neutral wire

I jumped in too quickly tryimg to correct an apparent error. Made some mistakes doing so.
1. Australia moved away from UK standard and adopted a WHITE phase wire instead of YELLOW.
2. Voltages need correcting from 230/440V to 230V/405V and 240v/415V

It seems I misunderstood your intent.

Well done.

[starfury1]

Re: Alternating current & neutral wire

yeh but if you did so may others so I hope I clarified it a bit better.

Yes thanks again cause I knew we had gone to 230VAC nominal (in 2000 I think it was)
inline with the world but wasn't sure what the between phase voltage was so thanks for that that needed to be stated too and I hadn't got around to that yet.

I should just add one thing on colours used. In AUSTRALIA

Red, Black.. Green/Yellow you will usually find in Mains "twin and earth"..(flat white stuff) the wiring used to run from your electrical box to GPO's (power points) and lights etc

On Lights the *Switched Active is suppose to be white (but done count on it you will find black being used in DIY jobs although none but a licensed Electrician is suppose to touch the our system (situation is a lot stricter in QLD now in respect to this)
(single phase stuff)
(*As black, I am not sure but in the old days it may have been that way due to the wire being made or possibly the code allowed for it... I am talking 40 50's and before, pre history to most people)

our mains Flex (the 3 core stuff find off appliances) is
Brown=Active
Blue=Neutral
Green/Yellow Earth

It is an international code I believe, used so "colour blind" people can tell which is which. That is my understanding

The above information is to make you aware and perhaps a little safer by knowing somewhat how it works. its not a license to go wiring up your houses, that is the domain of "Licensed Electricians" who have done the hard yards

probably posted something like this before but a re-post wont hurt

HTH

Cheers

[davmax]

Re: Alternating current & neutral wire

Heres a good link covering the Aussie appliance cable colours and connections.

http://www.accesscomms.com.au/Reference/powerplug.htm

[Per Hansson]

Re: Alternating current & neutral wire

Yea, sorry, we use a 3-Phase with Neutral

Each phase is 120° out of phase

Big industries and farms have 3-Phases and Neutral to their location

Smaller homes etc that don't need allot of current have 1 phase and Neutral, thus max 230VAC

[Logistics]

Re: Alternating current & neutral wire

Let me see if I get this straight. From a diagram I've seen of house wiring, at the box specifically, and from what I've read on Wikipedia, it appears a circuit could be created simply by having the HOT wire, which is the 110V, and a ground wire, since the Neutral wire is actually tied to ground, anyway. But from what I understand, the addition of a GROUND wire as a third conductor, is simply a safety precaution, giving spikes or whatever caused by lightning or equipment malfunction a place to go OTHER than the neutral wire, which would cross many other pieces of equipment in the circuit before reaching the Earth ground that is tied to the neutral wire somewhere in the system. Although, I would imagine this can only work if the GROUND conductor has more potential than the Neutral wire... which I'm not sure how it achieves aside from being a shorter path or thicker gauge.

Is this correct?

[Logistics]

Re: Alternating current & neutral wire



This is also interesting, but doesn't really help me have a full understanding.

[shadow]

Re: Alternating current & neutral wire

But from what I understand, the addition of a GROUND wire as a third conductor, is simply a safety precaution, giving spikes or whatever caused by lightning or equipment malfunction a place to go OTHER than the neutral wire, which would cross many other pieces of equipment in the circuit before reaching the Earth ground that is tied to the neutral wire somewhere in the system.

Actually I do not think anything will protect you from a lightning strike. The third ground wire is typically used to protect against equipment malfunction. Especially appliances with exposed metal casing.

The ground wire is attached to the metal chassis of the appliance. Therefore if the appliance malfunctions horribly and the metal case becomes live with 230V AC or 110V AC (whatever you use in your area), if you touch the metal casing even thou it is live then you should not get electrocuted because the current will flow through the ground wire and not through your body (current will mostly flow down the path of least resistance).

Another possible safety precaution that may be implemented in your area is that a fuse burns out or a safety switch changes state if there is excessive current present on the ground path (ie. there has been some device failure). I am not sure if this is actually present, however it is a possibility.

[starfury1]

Re: Alternating current & neutral wire

Let me see if I get this straight. From a diagram I've seen of house wiring, at the box specifically, and from what I've read on Wikipedia, it appears a circuit could be created simply by having the HOT wire, which is the 110V, and a ground wire, since the Neutral wire is actually tied to ground, anyway.

In short.... Yes.... it should work
(since neutral and Earth are effectively at the same potential and connected together)

But you would never do something like that and legally it would be a big No No

But from what I understand, the addition of a GROUND wire as a third conductor, is simply a safety precaution

Its main purpose I believe is as a SAFETY measure (as Shadow) said
with regards to your household

giving spikes or whatever caused by lightning or equipment malfunction a place to go OTHER than the neutral wire, which would cross many other pieces of equipment in the circuit before reaching the Earth ground that is tied to the neutral wire somewhere in the system.

Not 100% on this since its from memory
but this would really more apply to the Electrical Grid as a whole not specifically your house

As shadow said, an earth will not protect your equipment from a lightning strike
There are special "arrestors" you can get for this thought.
Some equipment is fitted with them.

Again not 100% sure but I think you can get surge protectors (of some kind)
fitted at the electrical box (by an electrical)

Although, I would imagine this can only work if the GROUND conductor has more potential than the Neutral wire... which I'm not sure how it achieves aside from being a shorter path or thicker gauge.

It is lest wise here suppose to be a thinker wire the earth and being earthed via Earth Stake and or water pipe (rules have changed here) should have a lower resistance to true ground then the Neutral which has to travel back to a point in the grid were it is then Earthed (to put it simply)

You can (depending) measure a voltage between the Earth and Neutral
think from memory you will find about 2 ~5 volts beyond that I think it needs to be looked at by an Electrician but not sure on this point voltage wise.

How Earthing is done, will depend on what the regs are for your location

Also I am taking Aust system but in the above regard I don't think the USA system differers really
(just you have a split phase system with 2 Actives and a Neutral)

Earth and Neutral still follow the same guides (use) as here.
Neutral as "Return" and Earth for "Safety"
(without getting into which way electrons flow or whats positive and whats negative)

Hope that clears it up a bit better for you,
as I said it can get quite complex when you start trying to understand the whole power grid and to be honest I don't fully understand it myself.

Cheers

[severach]

Re: Alternating current & neutral wire

>it appears a circuit could be created simply by having the HOT wire, which is the 110V, and a ground wire, since the Neutral wire is actually tied to ground, anyway.

Yes, but as soon as the wire carries current is no longer safe to touch. All of the devices that are safety grounded by that ground wire all the way to the fuse box become unsafe.

giving spikes or whatever caused by lightning or equipment malfunction a place to go OTHER than the neutral wire

That wire is not useful for shunting lightning surges though advertising would want you to believe so. That is a low frequency safety ground only. When your drill leaks current into the metal casing, the ground wire carries most of the current leaving you safe.

Although, I would imagine this can only work if the GROUND conductor has more potential than the Neutral wire... which I'm not sure how it achieves aside from being a shorter path or thicker gauge.

It is the same length and sometimes is a slightly smaller gauge, something that may return with the high price of copper. Many installers use crimp connectors or just wind them up instead of using wire nuts. It is usually left out when metal conduit interconnects metal boxes. How can it be so effective when the workmanship in grounding seems so slipshod? It never carries a current.

Actually I do not think anything will protect you from a lightning strike.

It is possible to protect against any lightning strike but for the cost you could buy a new house and all of the contents several times over all for a lightning strike that may never occur. Unless you're a TV station, a power station, or a telephone installation that needs lightning hardened power you can choose "almost" all for $100 or like most, no protection at all often for a similar price.

[hardwareguy]

Re: Alternating current & neutral wire

Go and look up a book online called "Lessons In Electric Circuits". It's a free e-book.

[starfury1]

Re: Alternating current & neutral wire

I think I posted a link on this in another thread but yeah I suppose it should be here as well.
not the total as an Ebook? (this link, if thats what you meant HWGuy)
Thanks for pointing it out

but in Volumes with a PDF of each Volume (Adobe PS too)
(click on the volume a pdf is a bit further down the page)

Well worth it to the budding electronics/electrically interested people.

Good Tech books tend to cost heaps so you cant complain about the price

"Lessons In Electric Circuits"

Id book mark the link for further reference while your there

Just beware, like everything errors may creep in so counter check if something don't make sense

(should add it does tend to get into the nitty gritty a fair bit)

HTH

Cheers

[Krankshaft]

Re: Alternating current & neutral wire

I would say yes will, when my body offers a lower resistance ground than what is offered at the socket. I have been shocked by electric drills and impact wrenches that had metal bodies but only when the hot & common were reversed. My feet / boots were wet as were my hands.
Over at AnandTech a fello had the hot / common reversed and was getting buzzed by his comp case. The wall socket was ungrounded.

On a related note I just got lightly buzzed by a AOpen Computer PSU I was using to test a tabletop HD radio I was powering after the repair the radio worked fine.

I had the device drawing its 12 volts off one of the yellow HDD connectors and the other going to the black ground wire on that connector.

I also jumpered the Green wire to the black ground wire to turn on the PSU.

I also had a HDD connected to be a dummy load since I was only using the 12 volt rail and without it the 5 volt rail would be unloaded.

Anyhow so I touch the case on the PSU and I think that I feel something so I touch it again and I feel an extremely light tingle. So I pull the plug.

My question is this a problem with the PSU, the load, or the outlet?

The load (the radio) doesn't have a ground connector just a standard 2.1mm barrel plug.

Is this a sign of a bad ground on the PSU?

[Ste]

Re: Alternating current & neutral wire

The centre point of a 3 phase star-wirred transformer is 0V no matter where you are in the world.

One of the 3 phases supplies your home. The neutral in your home runs back to the centre point of the transformer and also to earth.

Put an ammeter on the neutral of a light bulb and you will see that current is flowing. It you touch the neutral you will not be shocked because the path of least resistance is through the neutral back to the centre point of the traffo.

If you disconect the neutral and touch the lightbulb terminal you will be shocked as current will flow from the traffo, to the bulb, to you, to the ground (literaly) and back to the centre point of the traffo.

For the people wondering why power lines in their area only have 3 cables it is because the electricity provider is very clever. They supply 3 phase power in a delta configuration. At your local transformer, the voltage is stepped down via a delta to star transformer. As we've already seen the centre point of a star transformer is always 0V. Why run four cables when you can run three.