SWA Cables BS5467, BS6724

SWA Cables

SWA Cable - Steel wire layer

SWA Cable with and without sheath, showing steel wire armour


What is SWA?
SWA stands for steel wire armour – the material used to provide mechanical protection for multicore power cables such as SWA Cable (BS5467 and BS6724), 11kV Cable and 33kV Cable. Cable with SWA can also withstand higher pulling loads. Electrical cables with this layer of protection are referred to, more generally, as armoured cables.

What is SWA Cable?
SWA Cables are versatile mains electricity cables, found in power networks, cable ducting and external and underground projects.

There are two different types of SWA Cable – PVC (Polyvinyl Chloride) and Low Smoke Zero Halogen or LS0H. Each SWA Cable has class 2 stranded copper conductors, XLPE (Cross-Linked Polyethylene) insulation, steel wire armour and a black sheath. The PVC version – with PVC bedding and a PVC sheath – meets the requirements of BS5467, and the LS0H version – with LS0H bedding and a LS0H sheath – is produced to BS6724. steel wire armoured Cable or SWA Cable is sometimes called Booklet Armoured Cable, Mains or Power Cable.

What are BS5467 and BS6724 in relation to SWA?
BS5467 and BS6724 are British Standards that specify requirements for construction, and describe methods of testing for thermosetting insulated, armoured cables with rated voltages of 600/1000V and 1900/3300V. BS6724 focuses on those cables that produce lower levels of smoke and corrosive products when exposed to fire in specified tests. Cables from both standards are used in fixed installations in industrial areas and buildings.

When is LS0H SWA Cable specified?
LS0H SWA Cable is used in projects involving public areas. This is because the LS0H sheath emits very low levels of smoke and non-toxic levels of halogen gas when exposed to fire (usually under 0.5% HCl emission).

Is steel wire armour (SWA) used for all armoured cables?
A single core armoured cable uses Aluminium Wire Armour (AWA) instead of steel wire armour (SWA). The steel in SWA has a much lower conductivity – and therefore higher resistance – than aluminium. If it were used in a single core cable the magnetic field generated would induce an electric current in the armour (eddy current) and, combined with the increased resistance, would have a heating effect. AWA is non-magnetic and has a much better conductivity (lower resistance), so can conduct these induced currents to earth more efficiently than steel. SWA is used in multicore armoured cables because the electromagnetic fields from the neighbouring cores effectively cancel each other out – meaning less current is induced into the armour.


Which cable glands are used with SWA Cable?
BS7211 Cables SWA Cable uses brass glands CW and BW. CW Glands are for external use and BW Glands for internal. The sizes vary according to the number of cores and overall diameter of the cable. A 2 core x 2.5mm SWA cable, for example, will use gland size 20S for both CW and BW glands.

More information on SWA Cable



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