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"it is that pesky SY braided stuff again; so what's wrong with it"

psychicwarrior

More a discussion come question perhaps, but are there any really good reasons why a choice of SY would be made for a fixed wire low voltage power circuit  over something else ?

My understanding of the braiding,  is that it has nothing to do with armouring and is not acceptable as armouring;  but is it still an exposed conductive part to be earthed and if it is not [earthed], how much of a risk  ?

from reading Eland (who have a pdf on the SY stuff) to mention one manufacturer, is that it is a somewhat standards tested cable (https://www.elandcables.com/media/13rlt2rk/ec-statement-on-the-use-of-sy-cy-yy-cables-rina-18th-ed-with-summary.pdf)

In the case observed being a 3phs circuit, it was 5core (one as cpc) from a metal db (through plastic stuffing gland) to a plastic interlock socket, 16a 3pole mcb and it appeared the braiding was unterminated.   it was not on a run likely to be disturbed.   Nothing noted on the EIC about its use either.

regards

Habs

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    As a user of SY in experimental and mobile/luggable installations, I can say that whatever the nameplate voltage rating the actual impulse breakdown is in the tens of KV. Generally flash-over is determined by the way the core insulation has been (mis?) treated during the connection of the ends - it is simply not tested to any higher standard because there is little commercial appetite for a higher rated flex. I'd like one rated at 690v to ground/1k3 between phases at 400 and 800Hz, but I'm in a minority of one there I think..

    Actually the inner construction from some makes at least is certified to the same VDE norm as stuff sold in the UK as 'Arctic' flex but the outer plastic tends to be clear and has no great resistance to UV, so its use in sun such as the middle east is problematic, but there will be parts of the UK where it would be fine for years, perhaps decades.

    The question of no standard construction is  occasionally problematic, as the braid can vary from quite "whispy" and whole numbers of ohms per meter, to almost as good as the copper cores. Now EMP wise, oddly the lossy armour can be useful in terms of limiting surge currents into equipment, but from an EMC point of view that is a disaster and  a more closed braid window is better. But if folk do not actually terminate the screens, then really you have a length of arctic flex with a parasitic long wire radio antenna run beside it, which is often worse than not bothering.

    So in summary, it is useful stuff and has its place, but the strengths and limitations are not well under stood, even sometimes by the folk making it, who could probably sell more if they created a better datasheet for it.

    Mike

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    As a user of SY in experimental and mobile/luggable installations, I can say that whatever the nameplate voltage rating the actual impulse breakdown is in the tens of KV. Generally flash-over is determined by the way the core insulation has been (mis?) treated during the connection of the ends - it is simply not tested to any higher standard because there is little commercial appetite for a higher rated flex. I'd like one rated at 690v to ground/1k3 between phases at 400 and 800Hz, but I'm in a minority of one there I think..

    Actually the inner construction from some makes at least is certified to the same VDE norm as stuff sold in the UK as 'Arctic' flex but the outer plastic tends to be clear and has no great resistance to UV, so its use in sun such as the middle east is problematic, but there will be parts of the UK where it would be fine for years, perhaps decades.

    The question of no standard construction is  occasionally problematic, as the braid can vary from quite "whispy" and whole numbers of ohms per meter, to almost as good as the copper cores. Now EMP wise, oddly the lossy armour can be useful in terms of limiting surge currents into equipment, but from an EMC point of view that is a disaster and  a more closed braid window is better. But if folk do not actually terminate the screens, then really you have a length of arctic flex with a parasitic long wire radio antenna run beside it, which is often worse than not bothering.

    So in summary, it is useful stuff and has its place, but the strengths and limitations are not well under stood, even sometimes by the folk making it, who could probably sell more if they created a better datasheet for it.

    Mike

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