3-Phase System

Convention.

Stands for Red - Yellow - Blue. Convention (as PWSlack said), and conventionally the wiring colours used.

It's perhaps worth pointing out that, since European harmonisation, Brown-Black-Grey phase conductors will be seen on new installations in the UK instead of Red-Yellow-Blue, and certainly since April 2006. This causes complications:

• Black used to be the neutral conductor, and now it is a phase conductor
• Blue used to be a phase conductor, and now it is the neutral conductor.

Installations with mixed conductor colour conventions occur, perhaps where new wiring has been added post April 2006 to a pre-existing installation, require a cautionary label to that effect to be placed at the distribution board.

I hope you're joking PW....??

A major change like that is going to cause all sorts of confusion.

I've always been told to make wiring inside an instrument to give the prime colours to voltage carrying wires and secondary colours to signal wires etc...

I am not an electrician by the way so Its possible I've missed out on this change, but it does seem alarming to me!!

John.

http://en.wikipedia.org/wiki/3-phase_power and British Standard 7671.

<I hope you're joking PW....??>

Not at all.

<A major change like that is going to cause all sorts of confusion.>

Quite.

I myself use Black Red Blue for 208v 3p (White 120v)and Brown Orange Yellow for 480v 3p (Grey 277v)

In Australia, just to be different......only slightly........Red ,White and Blue are the phase conductors, Black is the Neutral conductor and Green/Yellow (or green) the earth.

Were are you from? Can't be USA.

For all those people out there interested in the new colour system, it goes like this..

For power Applications such as sockets and motors etc.

Black-Phase colour for general single phase circuits

Brown and grey can be used to identify specific circuits

Three phase-Black, Brown, Grey

Blue-Neutral

Green/Yellow-Earth

For Lighting

Black-Permanent feed

Brown-switch wire

Grey-strappers or permanent feed to an Emergency light

Blue-neutral

Green/Yellow-Earth

Here in Spain, the new system is in use and yes, it has caused a problem when dealing with older buildings, but it's getting to the stage now were it's not a problem!

I've used both the colouring systems and after a few months, you can generally tell what is old style and what is new!

It's done to avoid ambiguity; to identify seperately each line which are out of phase from each other...

Hi all,

Why don't you refer UL 508A or NEC and come to a common platform.

I am not an electrical engineer or electrician; but as an instrument tech in the past, this really helped for identification purposes regardless of the color scheme. Once again I point you to the fact that it is only done to avoid ambiguity. Nobody sticks to colors. That's why you have all these different opinions!!!!!!!!!!!!!!!!!!!!!!!!!!!!

You will never see sextuplets with the same name!

Individuality!!!!!!!!!!!!!!!!!!!!!!!!!!!

Besides, the question refers to 3phase systems in general, nothing about teasers, 208, 277, 480, 220, delta, star...!!!!!!!!!!

I bet NATO (Royal, USA and others) Navy ships still use Red Yellow and Blue for their 3 Phases at 440 Volts, no neutral....!!!

The "best" system in marine applications, 414v ac, red, white and blue phases, may have neutral for 240v ac (red, white or blue phase to neutral) but NO earth. This makes life very easy in detection of earth faults with an earth leakage detection system. Three reasons for using these systems are safety, continuity of supply and less problems with stray electric current.

<I bet NATO (Royal, USA and others) Navy ships still use Red Yellow and Blue for their 3 Phases at 440 Volts, no neutral....!!!>

One cannot purchase red/yellow/blue SWA or flat-triple-and-earth cable in the UK any more unless to special order, as the latest edition of BS7671 says brown/black/grey is the way forward. It's a good recipie for making it easier for cross-border occupational migration across the EEC nations, though the 13A fused plug is here to stay in the UK for some time, methinks.

http://en.wikipedia.org/wiki/BS_1363

Are you really asking me if a British standard applies to NATO built warships?

My answer is no, it was not a BS, nor will the ships adhere to BS either......unless you meant Bull Shit of course, then you might be right!!

Crappy Isthmus to all readers.

I like Red , Yellow , Blue these colors are much easier to identify in a machine that has had a dirty existence, Black, Brown,and Grey will end up looking much the same and depending wether the colors were only skin deep it would be no good scraping the wires to identify them. On cheap cables the colors do not seem to last to well and there will always be cheap product around.

No doubt there is some deep and dare I say it logical reason for the new standard but it escapes me.

Two things that are painfully obvious from reading the above: There is no one standard and color coding is not regulated. Maybe we are just trying not to be discriminatory in regards to our color blind comrades.

I have had that exact problem here! After a couple of years in a pig farm (the cables I mean!!), the colours are very hard to identify due to the lack of colour definition! Fly, general insect secretions, and the sh!t that get plastered everywhere after high pressure cleaning, including inside IP65 rated connection boxes, tend to dry the same colours as the coding itself! The old colour coded cables had a far better chance of correct identification due to the high visibility! I suppose whatever colour code we opt for, it will annoy most of the electricians, just like picking a universal language! for me, English would be best, maybe also throw in a couple of Spanish words for good measure, but I'm 100% sure that a man from Trinidad and Tobago would be really quite upset that his language was not chosen! It makes sense to pick an international or EU colour system just so that we all have the same opportunity to work in each others country with confidence! It's just a shame they didn't pick RWB

The color code I recall using in my past life follows: In the US Navy, the 3-phase power and lighting system (450/117) is Black, White, Red=A,B,C. Three wire DC (240-120) was Black and Red hot, White the neutral. In the civilian low voltage world (450 nominal), 3-phase delta is Black, Red, Blue; and 3-phase wye (440/208) is Brown, Orange, Yellow, Grey=ABC and neutral. Delta-Delta with a center tapped secondary winding (440/380/277), Orange is always the high leg. Single phase 220/120 is Black, Red, White with white being the neutral. The NEC only calls out colors for neutral (white or grey), ground (green or green-yellow, and high leg (orange).

Honesty....We use all black wire and label both ends. Problem is, the labels sometimes come off while pulling. So, make sure to put three labels at each end or you can waste a lot of time ringing it all out. The benefit is, you don't have a lot of different color wire spools in inventory.

I am observing response more on easy and minor techinical Q's but people are silent on major issues. Lets us try to ans major issues.

My professor at Uni told me the tale that the colours in Britain were Red, White and Blue to match the flag. Hence the same colours in the "colonies".

He said they changed to red, yellow, blue because sunlight caused the early red dyes to break down and bleach white, making terminals confusing.

The companion tale that this was to alienate the French is purportedly untrue ;-)

More relevantly, note also that the phase order is also denoted; in certain installations the phase order can be reversed (for purely historical reasons, or sometimes by the power authority to offset the human nature of preferring red to other colours... ).

How can you trust an industry with billions of watts which can't even get 3 simple colours right??? I ask you!

<More relevantly, note also that the phase order is also denoted; in certain installations the phase order can be reversed (for purely historical reasons, or sometimes by the power authority to offset the human nature of preferring red to other colours... ).

How can you trust an industry with billions of watts which can't even get 3 simple colours right??? I ask you!>

According to folklore, a high-power major connection in the Liverpool area has been made incorrectly, with the result that phase rotation in some parts of that district is the opposite of what it is elsewhere in the UK. It would be quite easy to disconnect and reconfigure the phases to be correct at the high power end of the system. The mayhem that would ensue at each individual user's premises downstream as a result of so doing doesn't bear thinking about.......

It is quite common for the red phase to carry the most current. When splitting out the phases into a distribution board for single phase loads, the breakers are sometimes arranged red-at-the-top, yellow-in-the-middle, and blue-at-the-bottom. Along comes Herbert the electrician, and what does he do to connect his new circuits? He starts at the top left, just like reading a sheet of writing........

It happened in Southampton as well!

You will find the reason for phase reversion in your good cities of Liverpool and Southhampton is to do with shipping. In Belfast where I orginated we had (and still do to a lesser extent) a large shipping industry (Titanic anyone? It's highly embarrassing to have one of your largest products being the most famous disaster in the world...). For reasons which now escape me the generators and motors operated in the opposite direction and when "borrowed" from vessels and wired in the normal manner by on-shore sparks everything ran backwards. Reversing the phases solved the problem. To this day in Belfast we still have odd HV voltages too (like 6.6kV and 13kV), due to the use of "decommissioned" ship's transformers leading to a de facto standard.

This of course could be highly suspect information!

Firstly in a three phase system the phase are not called R-Y-B. The three Phases are called Line 1-Line 2-Line 3 or U-V-W. The colour coding used to distinguish Phases from each other and from Neutal and earth conductors differs widley around the world and despite attempts to standardise as mentioned here by a number of comentators still serves more to confuse than enlighten.

"the phase are not called R-Y-B" - I'm afraid they are, albeit erroneously.

You said:-

Firstly in a three phase system the phase are not called R-Y-B.

That is absolutely wrong, many of us have actually worked on ships (NATO) which use(d) exactly this style of naming!!!!

I have heard from enough others to be pretty sure that some shore connections around the world have used it too......

Sorry, but what you said is simply wrong, but have a happy xmas anyway!

Aside from the word "firstly" I totally agree with the coconut guy. And I reiterate: just use black wires, mark 'em, and let's move on.

How right you are coconutpete, on the right is a voltmeter with a phase to phase switch, used on ships when changing over from ship to shore power and this shows L1, L2 and L3. You can also use a voltmeter with the phase to phase switch on the left hand illustration, again showing L1,L2 and L3.

This is used to ensure that you have power on all three phases before changing over to shore power.

some times UVW is also used.Just mere convention

Dear,

Go through IEC 60034-8 for eliminating confusion with RYB or UVW,