surface-mounted SWA – earthing

You are making an assumption Andy, and that is that the sheath is undamaged. As it is only mechanical protection (the definition of a cable sheath) you cannot assume that. If it is damaged and there is a fault, two things which may well happen together as that is why you are using SWA, it is an exposed conductive part at a dangerous potential to external Earth. That is why I class it as containment and exposed. Real SWAs do get damaged, and do sometimes get Earth faults to the armour. If they didn't no one would use them!

You are making an assumption Andy, and that is that the sheath is undamaged.

Not quite. My assumptions are that the SWA sheath is not lesser than the sheath found on an insulated & sheathed (e.g. T&E) cable, and in this particular case, SWA has been employed in a situation where T&E would have been acceptable (which seems to be the case from the OP's description).


Yes, a single event could damage both the sheath and basic insulation at the same time - but that's exactly the same issue with T&E (if anything the mechanical properties of the armour in the SWA cables make simultaneous damage to the basic insulation somewhat less likely). In situations where we're relying on the armour for protection (underground, concealed in walls outside of zones, or in harsh environments) then yes clearly we can't rely on the sheath remaining intact. In this case however the situation seems no worse at all than if T&E had been used - as if that was acceptable, how can this one not be?


  - Andy.

The main difference between T&E and SWA is that damage may make the armour live along its whole length, compared to T&E where any "liveness" is just at the nail or exposed bit of conductor or whatever at the one point. Thus making any other minor damage to the sheathing or termination potentially far more dangerous