Armour designations define the metallic protective layer applied over a cable’s inner sheath to provide mechanical resistance. SWA stands for Steel Wire Armour, utilizing galvanized round steel wires to deliver high tensile strength and impact resistance suitable for vertical drops and high-stress direct burial. STA (Steel Tape Armour) and DSTA (Double Steel Tape Armour) utilize helical steel tapes, offering superior protection against radial crushing, compression, and sharp mechanical impact. In cross-linked polyethylene (XLPE) insulated cables, N2XY represents an unarmoured power cable with a PVC outer sheath, whereas N2XBY integrates metallic tape armour (typically DSTA) for enhanced ground load endurance.
| Parameter / Feature | N2XY (Unarmoured) | N2XBY (Armoured) |
| Standard Designation | VDE 0276-603 / IEC 60502-1[1] | VDE 0276-603 / IEC 60502-1[1] |
| Conductor Options | Plain Annealed Copper (Class 1 Solid / Class 2 Stranded) | Plain Annealed Copper (Class 1 Solid / Class 2 Stranded) |
| Insulation Material | Cross-linked Polyethylene (XLPE) | Cross-linked Polyethylene (XLPE) |
| Armour Type | None | Double Steel Tape Armour (DSTA) |
| Rated Voltage () | 0.6/1 kV[2] | 0.6/1 kV[2] |
| Operating Temperature | 90°C Conductor Max / 250°C Short-Circuit[3] | 90°C Conductor Max / 250°C Short-Circuit[3] |
| Crush & Impact Resistance | Low (Requires Conduit / Duct) | High (Direct Underground Burial) |
| Tensile Load Capacity | Low | Moderate (Compression-focused, not for high tension) |
| Outer Sheath | Polyvinyl Chloride (PVC) | Polyvinyl Chloride (PVC) |
Breakdown of Metallic Armour Types: SWA vs. STA vs. DSTA
Armoured cables are classified by the structural geometry of the metallic protection applied over the bedding layer.
- SWA (Steel Wire Armour): Constructed with a helical layer of galvanized round steel wires (BS 5467[4] / IEC 60502-1[1]). Provides high mechanical protection alongside substantial longitudinal tensile capacity, making it the standard choice for direct burial, cable trays, underground ducts, and vertical shaft suspensions.
- STA (Steel Tape Armour): Utilizes a single layer of mild steel tape wrapped helically with an overlap. Designed to protect against heavy surface pressure and direct compression, though offering limited tensile pull resistance.
- DSTA (Double Steel Tape Armour): Consists of two layers of galvanized or black steel tape applied helically. The outer tape layer bridges the gaps of the inner layer, providing a 100% radial mechanical shield that resists crushing forces, rodent attacks, and direct soil impact.
CJDL CABLE Engineering Insight
For direct underground burial where crush and soil loading dominate, DSTA-armoured N2XBY is the sound choice, while N2XY suits ducted indoor runs where mechanical risk is low. All N2XY and N2XBY cables from CJDL CABLE are manufactured and routinely tested to VDE 0276-603 / IEC 60502-1. In buried-feed projects supplied by CJDL CABLE, DSTA armour has met demanding soil and crushing-load requirements without performance compromise.
References
[1] International Electrotechnical Commission. IEC 60502-1: Power cables with extruded insulation and their accessories for rated voltages from 1 kV up to 30 kV [EB/OL]. 2021-02-01.
[2] Wikipedia. Electrical cable [EB/OL]. 2026-01-15.
[3] Wikipedia. Cross-linked polyethylene [EB/OL]. 2025-11-20.
[4] British Standards Institution. BS 5467: Armoured cables for power distribution [EB/OL]. 2024-08-10.