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