Armoured Cable Options for Outdoor Direct Burial
Direct burial installation requires heavy-duty mechanical protection and moisture resistance to withstand soil compression, moisture ingress, stone impact, and ground movement. The primary armoured cable options available are Steel Wire Armoured (SWA) cables, Steel Tape Armoured (STA) cables, and Aluminum Wire Armoured (AWA) cables. SWA cables (e.g., BS 5467 / IEC 60502-1) utilize galvanized steel wires wrapped around the inner sheath, offering superior tensile strength and crush resistance for multi-core power circuits. STA cables utilize double steel tapes to block mechanical impact and rodent penetration, ideal for low-tensile underground runs. For single-core AC circuits, non-magnetic AWA cables must be used to prevent induced magnetic eddy current losses.
Direct Burial Armoured Cable Technical Comparison Matrix
| Specification / Feature | SWA (Steel Wire Armoured) | STA (Steel Tape Armoured) | AWA (Aluminum Wire Armoured) |
| Applicable Standards | IEC 60502-1, BS 5467, BS 6724 | IEC 60502-1, GB/T 12706 | IEC 60502-1, BS 5467 |
| Core Configuration | Multi-Core (2-core to 5-core+) | Multi-Core (2-core to 5-core+) | Single-Core Only (AC Circuits) |
| Mechanical Protection | High tensile strength & impact protection | High crush resistance & rodent defense | Moderate tensile & mechanical protection |
| Conductor Material | Class 2 Stranded Annealed Copper / Aluminum | Class 2 Stranded Annealed Copper / Aluminum | Class 2 Stranded Annealed Copper / Aluminum |
| Insulation Material | XLPE (90°C) or PVC (70°C) | XLPE (90°C) or PVC (70°C) | XLPE (90°C) or PVC (70°C) |
| Maximum Rated Voltage | 0.6/1 kV up to 18/30 kV | 0.6/1 kV up to 18/30 kV | 0.6/1 kV up to 18/30 kV |
| Outer Sheath Options | Heavy-duty PVC / LSZH (ST2/ST8) | Heavy-duty PVC / PE / LSZH | Heavy-duty PVC / LSZH (ST2/ST8) |
| Primary Underground Application | High-risk ground, pulling, direct trench | Static underground direct burial | Single-core feeder lines in AC systems |
Key Material Breakdown for Direct Burial Resistance
XLPE Insulation (Cross-Linked Polyethylene)
Underground cables are subject to moisture buildup and thermal retention within backfill soil. XLPE offers superior dielectric strength, low water absorption, and high thermal endurance compared to traditional thermoplastic insulation.
Galvanized Steel Wire Armour (SWA)
Comprising round galvanized steel wires helically wrapped around the inner bedding, SWA absorbs axial tension during cable pulling through underground ducts and trenches while offering robust protection against ground settling and excavation equipment.
Low Smoke Zero Halogen (LSZH) vs. Heavy-Duty PE Sheathing
While standard PVC outer sheathing (ST2) suffices for general burial, selecting a High-Density Polyethylene (HDPE) outer jacket provides maximum resistance to soil acids, alkalis, and moisture penetration. For underground runs entering building basements, specify LSZH (BS 6724) to comply with indoor fire safety and toxic fume regulations.