Armour is a layer of metal wire or strip under the outer sheath. It does two jobs: it protects the cable from mechanical damage (excavation, rodents, crushing), and it provides an earthed metallic path along the cable.
When armour is required
- Direct burial — armoured cable is the default for anything laid in the ground without a duct.
- Outdoor and industrial routes with mechanical risk — trays with traffic, walls prone to impact, farms and yards.
- Unarmoured is fine indoors, in conduit or duct, and anywhere the route is mechanically protected already.
Why single-core armour is different
A steel layer around a single core behaves like a transformer core — the alternating field induces losses in it. Single-core cables are therefore armoured with non-magnetic aluminium (round wire, flat strip or tape), while multicore cables use galvanised (GI) steel wire or strip, because the fields of the cores cancel.
Common designations
- SWA — steel wire armour, the standard for multicore power and control cable.
- AWA — aluminium wire armour, used on single core.
- Type 1 / Type 2 (BS 5308 instrumentation) — Type 1 is unarmoured, Type 2 adds single wire armour.
APAR supplies LV power, control, MV/HV and instrumentation cables in both armoured and unarmoured builds — the product pages carry the dimensional differences.