Introduction
Any cable line needs protection against mechanical impacts. One of the main questions when designing is whether to take an armoured power cable or to get by with an unarmoured one. The former is equipped with metal armour made of two galvanised steel tapes, the latter has only a sheath of PVC compound or polyethylene. The difference between them determines where and how to lay the line, whether additional protection with pipes is required, and how significant the installation costs will be.
Armoured grades — VBbShv, AVBbShv, VBShvng(A)-LS and their analogues — are designed for laying in the ground, on overpasses and in places with a risk of mechanical damage. Unarmoured — VVG, AVVG, VVGng — are used inside buildings, in trays, boxes and channels where there are no compressive or tensile loads. To understand which type to choose, it is worth comparing their properties in detail. Basic information on the design of power lines is given in the review about power cables.
Comparative table of armoured and unarmoured cables
| Parameter | Armoured (VBbShv, AVBbShv, etc.) | Unarmoured (VVG, AVVG, etc.) |
| Armour construction | Two galvanised steel tapes applied in a spiral | No armour |
| Mechanical protection | Withstands compression, impacts, tensile forces in the ground | Only PVC sheath, requires additional protection if there is a risk of damage |
| Laying in the ground | Permitted without pipe ducting | Prohibited without protective pipes or boxes |
| Laying outdoors | Allowed; UV resistance is limited (unless the sheath is special) | Allowed with UV protection or using a polyethylene sheath |
| Bending radius | At least 10 outer diameters for single‑core, 7.5 for multi‑core | At least 7.5 diameters |
| Flexibility | Lower due to tapes, stiffer on bends | Higher, especially for multi‑core with stranded conductors |
| Stripping and termination | Requires cutting and removing armour, earthing the armour through a joint or cable entry | Simple stripping of sheath and conductor insulation |
| Need for additional protection | None, except for aggressive soils (then cables with plastic insulation are used) | In ground and outdoors, pipes, trays, boxes are mandatory |
| Cable cost | Higher due to armour and the production process | Lower |
| Total line cost | Savings on pipes and earthworks | Additional costs for protective structures |
| Service life | 30 years or more with proper laying | At least 25 years under normal conditions |
| Main grades | VBbShv, VBbShvng(A)-LS, AVBbShv, AVBShv, VBShvng(A)-LS | VVG, VVGng, VVGng-LS, AVVG, AVVGng |
Analysis of key differences
Mechanical protection and steel tape armour
Armour made of two galvanised steel tapes, applied spirally with an overlap, forms a reliable shell. It protects the conductors from soil compression, point impacts from a shovel or stones. An unarmoured cable lacks such protection — the slightest damage to the sheath leads to moisture ingress and a short circuit. Therefore, for laying in the ground, an armoured cable with tape armour is a direct requirement of the PUE.
When laying an unarmoured line underground, plastic pipes or double‑wall corrugated structures have to be used, which increases the volume of earthworks and the estimate. An armoured cable, on the other hand, is laid directly in a trench on a sand bed. The difference in labour costs is especially noticeable on long routes with several bends.
Installation, joints and termination
Stripping an armoured cable is more difficult: after removing the outer sheath, the steel tapes must be carefully cut and removed without damaging the conductor insulation. The armour must be earthed at both ends of the line, for which cable joints or special entry devices are used. The joint itself for an armoured cable must ensure sealing and contact with the metal armour screen. Without this, in the event of a fault on the armour, it will become live.
An unarmoured cable is installed faster: it is enough to strip the sheath to the required length and connect the conductors. Indoors, this gives a noticeable time saving, especially with a large number of switchboards. The installation technology for both types, observing bending radii and fixing methods, is detailed in the guide cable laying.
Grades of armoured and unarmoured cables
Armoured power cables are represented by copper VBbShv, VBShvng(A)-LS and aluminium AVBbShv, AVBShv. The marking “VBbShv” stands for: PVC insulation, armour of two steel tapes, outer PVC hose. The abbreviation “ng(A)-LS” adds non‑flammability in group laying and low smoke emission. Examples of sizes: VBbShv 3×2.5, VBbShv 4×10, VBbShv 5×10, VBShvng(A)-LS 3×6, VBShvng(A)-LS 5×10. Aluminium: AVBbShv 4×16, AVBbShv 4×25, 4×35, up to 4×120. Aluminium armoured cable AVBbShv 4×16 is one of the most common for building entries and underground laying.
Unarmoured cables: copper VVG, VVGng, VVGng-LS; aluminium AVVG, AVVGng. For fire‑resistant lines, special versions are used, described in the review fire‑resistant cable. All grades are manufactured according to GOST 31996, and the conductors comply with GOST 22483. Plastic insulation and PVC sheath are standard for most models, providing resistance to moisture and chemical influences.
More details on copper versions — in the section with copper conductors. Aluminium versions are collected in the catalogue with aluminium conductors. There you can also find cross‑sections from 4×6 to 4×120. The choice of conductor material — copper or aluminium — is a separate broad topic, covered in detail in the material difference between copper and aluminium cable.
Commonly requested cross‑sections of armoured cables
| Grade | Typical cross‑sections | Number of cores |
| VBbShv (copper) | 3×2.5, 3×4, 3×6, 4×6 copper, 4×10, 4×16, 4×25, 4×35, 5×4, 5×6, 5×10, 5×16 | 3, 4, 5 |
| VBShvng(A)-LS | 3×2.5, 3×6, 5×10 | 3, 5 |
| AVBbShv (aluminium) | 4×16, 4×25, 4×35, 4×120 | 4 |
| AVBShvng | 4×16, 4×35 | 4 |
When an armoured power cable is needed
- Laying in the ground. Trenches, building entries, cable ducts under roads — everywhere where soil exerts pressure and mechanical impacts are inevitable. Armoured cables VBbShv and AVBbShv are specifically designed for these conditions.
- Outdoor overpasses and open routes. If there is no protection against falling objects, wind loads and ice formation, armour protects the conductors from rupture.
- Laying in places with vibration and possible impacts — for example, on bridges, overpasses, near railway tracks.
- Industrial sites with heavy machinery traffic, where the cable is laid in low trays or in the floor.
- Facilities with high requirements for line survivability, where cable damage is unacceptable for safety reasons. Here, VBShvng(A)-LS versions are often used, which do not propagate combustion and do not emit dense smoke.
When an unarmoured cable is sufficient
- Internal wiring in apartments, houses, offices. There are no compressive loads, and concealed laying in chases or behind plasterboard does not require armour.
- Installation in cable channels, trays, boxes, provided there is no risk of mechanical damage.
- Connection of stationary equipment in workshops, if the cable is protected by metal sleeves or laid at height.
- Lighting networks and socket groups, where cross‑sections usually do not exceed 4×6 or 5×4, and routes do not go outside.
- Objects where flexibility and installation speed are important: unarmoured cables are lighter, take up less space and do not require armour earthing.
Typical mistakes when choosing
- Laying an unarmoured cable in the ground without pipes. Even the strongest PVC sheath will not withstand soil pressure and point impacts — after a few years, insulation breakdown will occur.
- Using an armoured cable indoors without necessity. This complicates stripping, requires more space on bends and increases the estimate.
- Forgetting to earth the armour. The tape armour must be reliably connected to the earthing system at both ends of the line, otherwise, in the event of insulation damage, it will be at a dangerous potential.
- Incorrectly choosing the grade for a wet environment. For damp places and soils with high corrosion activity, cables with reinforced polyethylene or special plastic sheaths are selected, not standard PVC.
- Saving on joints when connecting armoured cables. Direct twisting without a sealed joint is unacceptable — moisture penetrates under the sheath and destroys the armour from the inside.
- Ignoring the bending radius. For armoured cables it is larger; excessive bending leads to tape buckling and damage to conductor insulation.
Frequently asked questions
What is the difference between VBbShv and VBShv?
VBbShv — with armour of two steel tapes and extruded filling between cores. VBShv — tape armour without filling or with a different core design. The first type is more resistant to compression and is preferred for laying in the ground.
How is VBShvng(A)-LS deciphered?
V — PVC insulation, B — armour of two steel tapes, Shv — outer PVC hose, ng(A) — does not propagate flame in group laying, LS — low smoke and gas emission. Such a cable is laid in fire‑safe areas and on escape routes.
Can aluminium armoured cable be laid in the ground?
Yes, AVBbShv 4×16, 4×25 and larger sections are used for building entries and distribution networks. Aluminium reduces weight and line cost. At the same time, contact connections are made with bimetallic lugs.
Is a joint required when connecting armoured cables?
Yes, absolutely. The connecting joint ensures sealing of the connection and continuity of the armour earthing circuit. For armoured lines, heat‑shrink or resin‑filled joints are used, matching the voltage and conductor cross‑section.
Where is VBbShv 4×10 cable used?
Mainly for three‑phase circuits with a rated current of up to 50‑60 A when laid in the ground or in air. For example, power supply to a small production building, outdoor lighting, a pumping station.
How to distinguish an armoured cable from an unarmoured one visually?
An armoured cable is noticeably stiffer, and a spiral relief of the tapes can be felt under the sheath. The marking on the sheath contains the letter “B” — VBbShv, AVBbShv. Unarmoured grades start with VVG or AVVG.
Conclusion
An armoured power cable is the uncontested solution for underground laying, open outdoor routes and sections with a risk of mechanical damage. An unarmoured cable wins indoors, where a plastic sheath is sufficient. Both types are produced with copper and aluminium conductors, in a wide range of cross‑sections — from 3×2.5 to 4×120. When choosing, consider the laying conditions, the requirements of the PUE and the technical characteristics of the grades according to GOST 31996. Observing these criteria guarantees reliable and durable operation of the cable line.
