Definition and Technical Meaning of SWA and DSTA Armoured Cables
SWA stands for Steel Wire Armour, and DSTA stands for Double Steel Tape Armour. Both terms designate specific mechanical protection layers applied to electrical power and control cables to safeguard the underlying insulation and conductors from mechanical stresses, external impacts, and environmental hazards.
According to global standards such as IEC 60502-1 and BS 5467, these armours function as a physical barrier and can also serve as an earth continuity conductor (primarily SWA). SWA utilizes a helical layer of galvanized steel wires, providing exceptional tensile strength and high impact resistance, making it suitable for pulling through conduits or deep vertical drops. In contrast, DSTA consists of two layers of steel tape wrapped helically over an inner bedding layer, designed to offer superior coverage and protection against crushing forces and rodent penetration in direct-burial applications, though with minimal tensile load capacity.
Technical Parameter Matrix: SWA vs. DSTA
The following data matrix compares the structural performance, mechanical properties, and compliance profiles of SWA and DSTA configurations for multi-core cables.
| Technical Parameter | Steel Wire Armour (SWA) | Double Steel Tape Armour (DSTA) |
| Primary Standard Compliance | BS 5467, IEC 60502-1, VDE 0276 | IEC 60502-1, IEC 60228 |
| Armour Material | Galvanized Low-Carbon Steel Wires | Galvanized or Cold-Rolled Steel Tapes |
| Mechanical Strength Profile | High Tensile Strength, High Impact | High Crush Resistance, Low Tensile |
| Flexibility | Rigid, limited bending radius | Semi-flexible, allows easier bending in specific planes |
| Earth Path Capability | Excellent (Can function as a protective CPC) | Poor (Requires separate earth core/screen) |
| Rodent & Pest Protection | High | Maximum (100% gapless tape coverage) |
| Typical Minimum Bending Radius | 12 × D to 15 × D (where D = Outer Diameter) | 10 × D to 12 × D (where D = Outer Diameter) |
| Primary Lay Method | Helical wire wrapping with minimum 90% coverage | Helical tape wrapping with overlapping joints |
Atomic Structural and Material Profiles
SWA: Steel Wire Armour Engineering
SWA cables feature a circular layer of galvanized annealed steel wires applied over an extruded PVC or LSZH (Low Smoke Zero Halogen) inner bedding. For single-core cables used in AC circuits, non-magnetic Aluminum Wire Armour (AWA) is substituted for SWA to prevent magnetic hysteresis heating. The wire diameter is strictly governed by cable size, typically ranging from 0.8 mm to 2.5 mm. SWA provides the longitudinal tensile strength required to withstand high pulling tensions during heavy industrial installations.
DSTA: Double Steel Tape Armour Engineering
DSTA cables utilize two layers of galvanized steel tape applied helically over the bedding. The outer layer of tape is positioned precisely to overlap the gaps or joints of the inner tape layer, ensuring an unbroken metallic shield. Because the tape is thin (typically 0.2 mm to 0.5 mm), it provides virtually no tensile strength. However, the overlapping structure offers absolute perimeter coverage, preventing sharp rocks, construction tools, or burrowing rodents from piercing the XLPE (Cross-linked Polyethylene) or PVC insulation layers during direct ground burial.