Armoured Electrical Cable: Complete Guide to SWA, STA and AWA Types, Standards and Installation
What Makes a Cable "Armoured"?
An armoured electrical cable carries a metallic layer — steel wire, steel tape or aluminium wire — between the inner covering and the outer sheath. That layer is not decoration: it takes the mechanical loads that would otherwise crush, cut or stretch the insulation during handling, burial and service. Armoured cable is the default choice for direct burial, ducts under roads, shafts, river and lake crossings, and any route where a digger, a rodent or a settling backfill is a realistic threat.
Because the armour is metallic and continuous, it also provides a low-resistance path to earth. Correctly glanded, the armour becomes the circuit protective conductor for the cable, which is why armoured cable dominates underground distribution from 0.6/1 kV up to 26/35 kV.
Construction of an Armoured Power Cable
- Conductor — class 1 or class 2 copper or aluminium to IEC 60228, stranded compacted for sizes above 16 mm².
- Insulation — XLPE rated 90 °C, or PVC rated 70 °C for lower duty.
- Inner covering — extruded PVC bedding that protects the insulation from the armour wires and prevents galvanic contact.
- Armour — galvanised steel wire, steel tape or aluminium wire, applied helically with controlled coverage.
- Outer sheath — PVC ST2, PE or LSZH, black, with marking, drum number and metre length.
The Three Armour Types and When to Use Each
| Armour | Designation | Typical voltage | Best for |
|---|---|---|---|
| Galvanised steel wire (SWA) | YJV32, VV32 | 0.6/1 kV – 26/35 kV | Direct burial, shafts, river crossings, high tensile loads |
| Galvanised steel tape (STA) | YJV22 | 0.6/1 kV – 3.6/6 kV | Buried distribution where radial crush protection is enough |
| Aluminium wire (AWA) | YJLV72 | 3.6/6 kV and above, single-core | Single-core AC circuits where steel would cause induced losses |
The choice is not cosmetic. Steel armour on a single-core AC cable produces circulating currents in the armour that heat the cable and cut its rating; aluminium wire armour removes that problem. Conversely, aluminium armour has lower mechanical strength, so steel wire remains the standard for buried three-core feeders.
Standards to Specify
- IEC 60502-1 / -2 — the international reference for 1 kV and 6–30 kV extruded cables.
- IEC 60228 — conductor classes and maximum resistance.
- GB/T 12706.1 — the Chinese equivalent accepted on most Asian and African projects.
- BS 5467 / BS 6724 — the UK armoured cable standards frequently cited by consultants in the Middle East.
- IEC 60332-3 — flame propagation, when a flame-retardant design is requested.
Technical Data: 0.6/1 kV Copper Armoured Cable (Excerpt)
| Construction | Cross-section range | Insulation | Test voltage | Bending radius |
|---|---|---|---|---|
| YJV22, 4-core, STA | 1 – 630 mm² | XLPE, 90 °C | 3.5 kV / 5 min | 15 × OD |
| YJV32, 4-core, SWA | 1 – 630 mm² | XLPE or PVC | 3.5 kV / 5 min | 15 × OD |
| YJV32, single-core, SWA | 25 – 630 mm² | XLPE, 90 °C | 3.5 kV / 5 min | 20 × OD |
| YJLV72, 3.6/6 kV, AWA | 1.5 – 1000 mm² | XLPE, 90 °C | 12.5 kV / 5 min | 15 × OD |
Installation Rules That Decide Cable Life
- Bending radius — 15× overall diameter for multi-core, 20× for single-core. Violating this cracks the sheath at the point of the bend and lets water reach the armour.
- Burial depth and bedding — 0.7–0.9 m cover, 100 mm sand bed, protective tiles or warning tape, and a marker at every joint.
- Glanding and earthing — the armour must be terminated in a proper gland with an earth tag; the armour is the earth path, and a loose gland is an open circuit.
- No magnetic duct for single-core — a single-core armoured cable pulled through a steel pipe overheats; use PVC ducts and non-magnetic cleats.
- Pre-heating below 0 °C — PVC sheaths crack when bent cold; warm drums to at least 5 °C first.
Termination detail is where most site failures originate, so we covered it separately in armoured cable glanding and earthing. Cross-section choice is covered in the armoured cable selection guide.
Frequently Asked Questions
What is the difference between SWA and STA cable?
SWA uses galvanised steel wires for high tensile and impact resistance; STA uses two or more steel tapes for radial crush protection at lower cost. SWA suits long buried runs and crossings, STA suits ordinary distribution trenches.
Can armoured cable be laid directly in the ground?
Yes — that is its primary purpose. Provide a sand bed and mechanical protection above the cable, and keep the armour earthed at both ends of the run.
Is the armour a valid earth conductor?
For most LV circuits, yes, provided the gland is correctly installed and the armour cross-section satisfies the adiabatic check for earth-fault current. Where it does not, a separate CPC core or wire is required.
Why use aluminium wire armour on single-core cable?
Steel armour on a single-core AC conductor carries induced currents and loses ampacity. Aluminium wire armour is non-magnetic and removes that loss.
Buying Armoured Electrical Cable
Shanghai Shenghua Electric Wire & Cable Co., Ltd. manufactures armoured electrical cable under the Shenghua Cable brand, covering YJV22 steel tape, YJV32 and VV32 steel wire and YJLV72 aluminium wire constructions from 1 mm² to 1000 mm², in 0.6/1 kV to 26/35 kV, certified to ISO, CE, CCC, KEMA and TUV, with 100 km per week capacity and a ten-day standard delivery.
Send voltage grade, armour type, core configuration and destination port and we will return a technical offer with drum schedule and test documentation.
