Three Phase AC Phase Conductor Colours - Mandatory?

Many thanks Graham ... all noted! Best regards - Fraser

Thanks Graham. The installation has been completed and is commissioned now (with no known phase rotation / sequencing issues). I think your hypothesis (a) is the root cause; the panels were incorrectly wired (Grey, Black, Brown) not i.a.w. the designer's schematic (Brown, Black, Grey). As you can imagine, we've asked the panel manufacturer to explain the inconsistency and I await their response! From your responses and my own research, and given the very good conductor labelling, I'm minded to have the schematics updated to match the 'as built' situation rather than have every panel re-wired (!) ... and I would also seek a bold notification on each schematic informing the maintainer of the colour code in use within the panel. Regards - Fraser

Indeed - it's important to lots of people, yet BS 7671's precise colour coding scheme doesn't actually help at all. If your company had two sites, one in York and another in Kent, both installations wired identically using the precise L1=brown, L2=black, L3=grey notation consistently throughout, you'd still run the risk of a motor running backwards if you transferred it between the two sites.

From my local DNO (https://www.northernpowergrid.com/asset/0/document/103.pdf )

The phase sequence at each system voltage is represented vectorially by R-Y-B anticlockwise rotation with the exception of the 11kV and LV system in the City of York and the LV (fed from 11kV) system in Middlesbrough, which are represented by R-Y-B clockwise rotation.

I guess other areas have their own examples.

  - Andy.

Cheers Andy - the NPG pdf is interesting! It's not something I've ever considered but is a great example showing that the phase rotation can differ from location to location. I guess this is very much an inheritance from 'pre-history' that can never be practically standardised due to the high cost; e.g. on the Foss Islands Retail Park! Thank you again - F

In the U.K. L1 should be RED, L2 should be YELLOW and L3 should be BLUE as seen on millions of external transformers nationwide.. Obvious bright and logical colours, not dinghy dark similar and often misidentified colours.

www.youtube.com/watch

M.E.M. ruled....O.K. and still does.

Z.

I have just been reading 514 in the regs, and I think it is probably rather misleading. I think that its connection of L1..3 as labels to colours needs very careful explanation. In the table 51, these are connected as cable identifications only, in other words L1 as a cable marker is interchangable with brown as a cable colour. Many accessories and products for 3 phase equipment are labeled on terminals with L1, L2, and L3, and perhaps N, which seems to imply with 514 that only a brown wire should be connected to L1 etc. There is no logical or operational requirment as to why this needs to be true, although it may be used on wiring drawings or schedules to ensure correct wiring. Lots of items, such as rotary switches avoid this ambiguity by numbering the terminals, and wiring schedules for panels or similar simply say brown wire (Br) connected to item 1 terminal 8 and item 2 terminal 6.

Idealy I suggest thet L1..3 is ONLY used as wire identification of wires with other sheath colours, and not as indicators of actual connections on other items. Some items such as motors have markings of W1..6, others have the illogical L1..6! I feel that this has been missed in the IEC and BS7671 standards, and we have ended up with all manner of terminal designations that can be confusing. It has also caused this thread!

David Stone said:

Many accessories and products for 3 phase equipment are labeled on terminals with L1, L2, and L3, and perhaps N,

Shouldn't terminals on three-phase equipment be labelled "U", "V" and "W" in accordance with BS EN IEC 60445, to avoid this confusion?

This isn't new, by the way !

Also worth noting for some panels, if BS EN IEC 60204-1 applies (machinery as defined in the Machinery Directive, including machinery control panels and drives), colours are different to BS 7671, and the standard has some requirements that over-ride BS EN IEC 60445.

This is a good article which discussed the differences regarding FE and line conductors: www.gt-engineering.it/.../shall-a-basic-safety-standard-be-applied-to-machineries-the-case-of-pink-functional-grounding-cable

Be careful Graham, you are opening another huge can of worms, leaving one with the impression that no two "standards" are in any way standard with one another, and the whole lot is a massive mess! I will make no opinion, but from experience this pretty much applies across the whole gamut of EU alleged "standards". On the whole BS7671 is comparitively good to excellent, although still suffers from feature creep in unintended ways. This is probably because a single committee (JPEL/64) has the final say and others like you keep up the reminders about all the interacting standards, thanks!

David Stone said:

Be careful Graham, you are opening another huge can of worms

I'm just sharing what I know

David Stone said:

leaving one with the impression that no two "standards" are in any way standard with one another

If you're referring to BS EN IEC 60204-1, well, there are some very good reasons why the standard should be the way it is, and each part of the machinery (including control panel) should be supplied with a schematic, and wiring numbered to avoid confusion. A control panel would be equally confusing in terms of "uncontrolled mains in" vs "mains out per phase" (e.g. to motors) and "auxiliary per phase" (AC controls).

However, it might surprise you to know that, whilst BS EN IEC 60204-1 might look slightly different (e.g. all black conductors for each phase or line conductor in single phase systems), it does actually align with BS EN IEC 60445, in that black is a permitted line conductor colour - neutral is still blue, protective conductors still green-and-yellow, and the other colours identify specific functions of the conductor relative to the machinery or control panel.

However, not sure what all that has to do with the fact that you're seeing L1, L2 and L3 on equipment terminals, when the standards say they should be U, V and W? That goes for BS EN IEC 60204-1 as well as BS EN IEC 60445 and BS EN 61666 (the latter two being referenced from BS EN IEC 60204-1). BS EN 61666 is terminal identification in industrial equipment, and aligns with BS EN 60445 on the use of U, V and W.