Screening control cables

[shanky887614]

Don't try telling the Germans that!

I'm back at a job we installed a few months ago, ripping out Swa to control panels and replacing it with NYY because they don't recognise this cable type as a product which complies with Vde

It's really a case of sour grapes, the German contractors that normally do work for this company lost out on price ( to us ) to supply power to the equipment we're installing, and as he is actually testing the job and signing it off he says that it has to be done with a cable he is familiar with !
His colleague said he was impressed with the standard of work we'd done, but it was out of his hands!

wouldnt sy have been better?

 

[edexlab]

Not my decision ! We have 5 engineers inc the Md above us , we just have to install to plan and sort things out on site ourselves,
They decide everything, which is a bit frustrating sometimes as I'm used to doing this for myself and as they are all controls biased ,they lack imagination/practical experience it comes to distribution, final circuits
I know for a fact I have a lot more experience /knowledge in this area.
He quibbled over the lights which were Swa to the switch and SY to each fitting , obviously he's not keen on Swa but after he said no to SY I asked him for a detailed explanation of why it wasn't acceptable, he just said in Germany we don't do this, so I asked him what difference there was between our SY lighting circuit and one his company had installed in the adjacent part of the building. ...
No answer! Which I think proves my theory

 

[shanky887614]

Not my decision ! We have 5 engineers inc the Md above us , we just have to install to plan and sort things out on site ourselves,
They decide everything, which is a bit frustrating sometimes as I'm used to doing this for myself and as they are all controls biased ,they lack imagination/practical experience it comes to distribution, final circuits
I know for a fact I have a lot more experience /knowledge in this area.
He quibbled over the lights which were Swa to the switch and SY to each fitting , obviously he's not keen on Swa but after he said no to SY I asked him for a detailed explanation of why it wasn't acceptable, he just said in Germany we don't do this, so I asked him what difference there was between our SY lighting circuit and one his company had installed in the adjacent part of the building. ...
No answer! Which I think proves my theory

why sy to lights? it doesn't really offer any more protection than yy.

or do you lights have somekind of 0-10 control etc?

 

[edexlab]

Nope nothing fancy , just someone upstairs's idea on how it should be done ......
Like I said. ........

 

[netblindpaul]

SWA does not provide adequate EMC screening.
End of.

 

[edexlab]

SWA does not provide adequate EMC screening.
End of.

Obviously I'm here asking about this subject, so I'm not an expert, still reading up on it
I wouldn't have used SWA with EMC screening in mind.....
but as a cable for power ie to motors etc , wouldn't it be better than something like NYY when run in close proximity?
I know ideally there should be some separation, but often cables of all types are in the same containment , which is often going to be a potential problem.

 

[netblindpaul]

If you are working to EMC reg's then they will take priority over BS7671, even if BS7671 applies.
SWA is a "BS7671" cable.
It is about as good as a collander at keeping water in as regard to EM emissions.

 

[edexlab]

I've been reading an ebook/guide to EMC and methods of minimising effects using components or screen techniques , interesting stuff!

Yet it seems to me on jobs I've been on or seen (exception being data centres) that apart from larger installations it's pretty much ignored .....

Separation within the same containment ie using one side of basket/tray for signal/control a small gap and the remaining side for power and screens connected at one end is the main method used although the actual "Separation" gap used I think is questionable sometimes

 

[netblindpaul]

I've been reading an ebook/guide to EMC and methods of minimising effects using components or screen techniques , interesting stuff!

Yet it seems to me on jobs I've been on or seen (exception being data centres) that apart from larger installations it's pretty much ignored .....

Separation within the same containment ie using one side of basket/tray for signal/control a small gap and the remaining side for power and screens connected at one end is the main method used although the actual "Separation" gap used I think is questionable sometimes

Yep that explains why I end up picking up the pieces when these things go wrong because the muppets who design and install them don't understand the requirements and why these requirements are in place.

 

[edexlab]

Shouldn't be too bitter Paul!
I bet you make a half decent living out of these mistakes,
but I'm surprised that nowadays with technology moving on that there's very little taught about this at colleges etc , I remember touching on it vaguely and being told " Don't worry too much about it"
My last apprentice had the same advice!

 

[shanky887614]

Shouldn't be too bitter Paul!
I bet you make a half decent living out of these mistakes,
but I'm surprised that nowadays with technology moving on that there's very little taught about this at colleges etc , I remember touching on it vaguely and being told " Don't worry too much about it"
My last apprentice had the same advice!

vsd were mentioned less than micc when i did my 2330.

 

[SheffSimon]

SWA does not provide adequate EMC screening.
End of.

I have read a number of sources that SWA is perfectly adequate, and have been told the same by both ABB, and on a Control Teqhniques training course many moons ago, so I would be interested to know why you think otherwise?

 

[netblindpaul]

Because I was told exactly the opposite, during my training, and it was in our documentation when I worked for the drive and control company.

 

[davesparks]

I have read a number of sources that SWA is perfectly adequate, and have been told the same by both ABB, and on a Control Teqhniques training course many moons ago, so I would be interested to know why you think otherwise?

At a basic and simplified level it is due to the armour strands all being laid up in the same direction and occasionally having gaps between the strands.
SY or DWA offer better screening as they have aver lapping strands in the screenso that gaps are much smaller.
The best screening is afforded by a complete metal covering such as a foil screen, steel conduit or micc

 

[Darkwood]

In reference to VSD motor cables then I have to agree with the fact that they are poor choice for screening, the armour will provide some screening protection at low frequencies hence your volt-stick won't see if the cable is live but due to the nature of harmonics and the high frequencies that are seen in relation to using VSD's then SWA serves little if any EMI protection.

I only ever use SY, Lapp or Igus which comes in many formats but as I'm usually handling these cables alot I know where to get them, although SY has snuck into the standard wholesaler been sold (mis-sold) as a armoured flex which it is then put to so many incorrect uses.

If you search hard enough you can get screened SWA although most of what I have seen is for signal and data use and HV/MV power cables.

So as a solution for screening IMO then standard SWA doesn't qualify and not only can this see illegal EMI but can cause drives and motors to prematurely fail... also another very big issue with harmonic noise is rcd masking where it can stop rcd within the same installation from actually seeing earth leakage faults.