S.W.A. Armour Earthing.

The filler or bedding layer is outside the conductors to provide a smooth surface for the armour to lay on and has nothing to do with the sheath. If it were not there the armour would be variously corrugated and might damage the conductor insulation if the cable is moved. It ensures that all the armour strands are exactly the same length and thus can move freely. I pointed out why sheaths are not considered insulating above, it is because cables pass through a cooling water bath after extrusion which is used to also test that the insulation is complete with an insulation test. The sheath cannot be tested separately and so cannot be guaranteed to be complete, although it is rarely defective. Simple. I suppose the SWA sheath could be tested in the same way but I believe that it is not.


There is another point about the armour too, why would you not use this as the CPC? In sizes up to I thtink 95mm always has at least as much corrected cross section as the conductors, so is very suitable. I know that SWA in 3 core is often cheaper than the 2 core version, but this is not a reason to use the spare core as CPC, you would bet better off paralleling one of the live conductors fro reduced volt drop.

The filler or bedding layer is outside the conductors to provide a smooth surface for the armour to lay on and has nothing to do with the sheath. If it were not there the armour would be variously corrugated and might damage the conductor insulation if the cable is moved. It ensures that all the armour strands are exactly the same length and thus can move freely. I pointed out why sheaths are not considered insulating above, it is because cables pass through a cooling water bath after extrusion which is used to also test that the insulation is complete with an insulation test. The sheath cannot be tested separately and so cannot be guaranteed to be complete, although it is rarely defective. Simple. I suppose the SWA sheath could be tested in the same way but I believe that it is not.


There is another point about the armour too, why would you not use this as the CPC? In sizes up to I thtink 95mm always has at least as much corrected cross section as the conductors, so is very suitable. I know that SWA in 3 core is often cheaper than the 2 core version, but this is not a reason to use the spare core as CPC, you would bet better off paralleling one of the live conductors fro reduced volt drop.