PVC Steel Tape Armored Power Cable

Lowest Unit Cost in the Armoured Cable Family

VV22 is consistently the lowest-cost armoured power cable across all cross-sections: approximately 20-25 percent cheaper than YJV22 (XLPE STA), 30-35 percent cheaper than YJV32 (XLPE SWA), and 20-25 percent cheaper than VV32 (PVC SWA). On utility-scale distribution projects ordering tens or hundreds of kilometres, this is a significant budget difference. For projects in price-sensitive markets where the load and installation conditions genuinely do not require XLPE or SWA, VV22 is the correct engineering and economic specification.

Direct Burial Without Conduit in Stable Soft Soil

The double steel tape armour satisfies the mechanical protection requirement for direct burial in stable, soft-to-medium soil per IEC 60364-5-52. For horizontal runs in cable trenches with sand bedding at the required depth (600 mm without traffic, 900 mm under roads), no conduit is required — the tape armour provides the code-required protection. The conduit cost saving is typically 30-50 percent of the cable cost itself, making armoured direct-burial cable significantly cheaper than unarmoured cable in conduit.

Like-for-Like Replacement of BS 6346 STA Cable

Enormous quantities of BS 6346 PVC STA cable were installed globally across the UK, Commonwealth countries, and export markets from the 1950s through the 1990s. Much of this cable is now reaching end-of-life and requires replacement. VV22 / NYBY provides correct like-for-like jointing into BS 6346 STA installations: matching PVC insulation (avoiding the thermal mismatch at joints between 70°C PVC and 90°C XLPE), matching tape armour construction, and interchangeable terminations. The like-for-like replacement case is the strongest argument for VV22 in developed markets where YJV22 would otherwise be specified for new work.

Armour as Circuit Earth Path (Same as YJV22)

The double steel tape armour provides a low-resistance earth-continuity path between cable terminations when bonded to earth at both ends via STA armour cable glands. For LV installations, the armour is typically used as the circuit protective conductor (CPC), eliminating the need for a separate earth conductor in most 3-core and 4-core configurations. Verify the armour cross-sectional area satisfies BS 7671 Table 54.7 or IEC 60364-5-54 for the circuit’s earth-fault current and disconnection time. The armour earth path is a function of the steel tape construction, unchanged by the PVC vs XLPE insulation material.

Key Limitation: No Tensile Strength, 70°C Ampacity Only

VV22 has two clear limitations that must be understood before specification. (1) No tensile strength: the double tape layers separate under longitudinal tension — never specify VV22 for vertical shafts, submarine crossings, sloped terrain, or any installation imposing tensile loads. Use VV32 (PVC SWA) or YJV32 (XLPE SWA) for those applications. (2) 70°C ampacity limit: PVC insulation limits conductor temperature to 70°C, producing 30-40 percent lower ampacity than the 90°C XLPE-insulated YJV22 at the same cross-section. Always size from 70°C PVC tables — never XLPE tables.

IEC 60502-1 and BS 6346 Certified

Production certified to IEC 60502-1 as primary international reference for the VV22 / NYBY designation, plus BS 6346 for UK and Commonwealth replacement-installation acceptance and AS/NZS 5000.1 for the Australian and New Zealand market. For European projects, the cable can be designated NYBY (copper) or NAYBY (aluminium) per the VDE/IEC naming convention. Note that BS 6346 STA has been superseded by BS 5467 XLPE STA for new UK utility and industrial installations; BS 6346 certification is primarily requested for legacy replacement and repair.

STA cable requires armour cable glands — not standard PVC glands — that grip the steel tape layer and provide both a mechanical strain relief and an earth-bonding connection. The gland must contact the steel tape layer circumferentially to provide a low-resistance earth path. Pigtail connections from individual tape strips have high contact resistance and poor mechanical retention. Specify the gland size from the cable OD (VV22 OD at the same cross-section is similar to YJV22; verify actual OD before ordering glands). Brass glands for standard use; stainless for corrosive outdoor or marine environments.

The single most important VV22-specific practice. Every cable sizing calculation for VV22 must use the 70°C PVC conductor temperature tables in IEC 60364-5-52 (or BS 7671 Appendix 4 for UK projects). Using the 90°C XLPE tables that apply to YJV22 produces a cross-section 15-20 percent too small for PVC — the cable will exceed 70°C under continuous full-rated load and suffer accelerated insulation degradation. This error is most likely to occur when a project specification switches from YJV22 to VV22 for cost reasons without re-doing the ampacity calculation. Always re-size from scratch using 70°C tables when switching insulation specification.

For direct burial, prepare the trench with 100 mm sand or fine-soil bedding below the cable, remove all angular stones and foreign material from the cable zone, and lay the cable in a gentle S-curve (snaking) to allow 2-3 percent thermal expansion without pulling the terminations. Apply 150-300 mm fine-soil cover above the cable before backfilling with native soil. Warning tape or concrete tiles at 100-150 mm above the cable provides excavator warning. Cable route marker posts at changes of direction allow future locating without cable detection equipment. For soft waterlogged soil, check whether the soil thermal resistivity exceeds 1.0 K·m/W and apply the IEC 60287 correction if necessary.

STA cable minimum bending radius is 12× OD per IEC 60502 (tighter than 15× OD for SWA, because tape bends more readily than round wire). Bending tighter than 12× OD permanently kinks the tape layers and creates gaps in the armour coverage at the kink. Gaps in STA coverage leave the cable locally unprotected against compressive loads — an angular stone at the kink location could puncture the cable over time. Use proper cable rollers at duct bends during pulling, not manual force. The tighter bending radius of STA vs SWA is one of the installation advantages of the tape construction for conduit and duct work with tight bends.

The steel tape armour is not watertight — moisture enters through the inter-tape gaps. Apply heat-shrink end caps or self-amalgamating tape to cable ends immediately after cutting, before moving the cut section to the installation site. For cables in open trenches awaiting backfill, seal both ends before any rain event. For cables pulled into conduit or duct before final termination, seal the exposed end at the duct entry. PVC cable absorbs moisture more readily than XLPE — moisture in a VV22 cut end wicks more aggressively and degrades insulation resistance more rapidly. This makes end sealing particularly important for VV22 compared to YJV22 or YJV32.

Insulation resistance test (megger at 1 kV DC) between every conductor and earth (armour) and between adjacent conductors before energising. Expected reading for new VV22 is > 100 MΩ per km — lower than the > 1000 MΩ baseline for XLPE cable, because PVC has inherently higher moisture permeability. Readings below 20 MΩ per km indicate water ingress or damage requiring investigation. Document the baseline test results in the project handover; PVC insulation resistance decreases more with age than XLPE, making the baseline record essential for condition monitoring and maintenance planning over the cable’s 25-35 year service life.