I really don't like the definition of an "exposed conductive part" - there are too many places like this where it doesn't really make sense - another being flush metal back boxes.
As well as underground, if you've picked SWA to provide safety because you think there's a reasonable chance of mechanical damage above ground, then it seems obvious that the armour still needs to be earthed - but the definition of an exposed-conductive-part doesn't really sit well with that (regardless of whether the sheath in insulating or not, it does prevent the armour itself being exposed to touch). Ditto for the foil in screened (e.g. BS 8436) cables.
We are a bit double standarded (is that a word?) though - on one hand we claim the sheath isn't an adequate insulator, but then when we create a TT island we typically rely on the sheath (and boot over the gland) to prevent contact between two different earthing systems (which under some conditions can differ by full mains voltage).
I really don't like the definition of an "exposed conductive part" - there are too many places like this where it doesn't really make sense - another being flush metal back boxes.
As well as underground, if you've picked SWA to provide safety because you think there's a reasonable chance of mechanical damage above ground, then it seems obvious that the armour still needs to be earthed - but the definition of an exposed-conductive-part doesn't really sit well with that (regardless of whether the sheath in insulating or not, it does prevent the armour itself being exposed to touch). Ditto for the foil in screened (e.g. BS 8436) cables.
We are a bit double standarded (is that a word?) though - on one hand we claim the sheath isn't an adequate insulator, but then when we create a TT island we typically rely on the sheath (and boot over the gland) to prevent contact between two different earthing systems (which under some conditions can differ by full mains voltage).
