XLPE Steel Tape Armored Power Cable

Direct Burial in Stable Soil Without Conduit

The double steel tape armour satisfies the mechanical-protection requirement for direct burial in stable, soft-to-medium soil per IEC 60364-5-52 and BS 7671. No concrete encasement or plastic conduit is required — just sand bedding, the cable, warning tape above, and backfill. Eliminating the conduit cost and installation complexity is the economic argument that makes STA the default choice for the majority of underground distribution projects: typical conduit costs 30-50 percent of cable cost, so the armour more than pays for itself.

10-20% Lower Cost Than SWA at the Same Rating

Steel tape uses less steel per metre than steel wire armour — the tape is thinner and the flat cross-section contains less material per unit coverage than a round wire construction. Combined with a faster armouring line speed for tape vs wire, the STA construction consistently costs 10-20 percent less per metre than SWA at the same cable specification. For utility-scale projects ordering tens of kilometres, this is real money. Over-specifying SWA where STA would do is one of the most common unnecessary cost escalations in underground distribution projects.

Lighter and Easier to Handle Than SWA

A 4-core 95 mm² YJV22 typically weighs 5 to 8 percent less per metre than the equivalent YJV32 — the round wire armour adds more steel mass. On large cable runs, the weight difference matters to drum handling, cable-pulling crew sizing, and cable-tray load calculations. The STA bending radius (12× OD during installation) is also tighter than SWA (15× OD), allowing installation through tighter cable duct bends and around closer cable tray corners.

90°C XLPE = 30-40% More Ampacity Than PVC-Armoured

The XLPE insulation inside the STA construction is rated 90°C continuous, 130°C emergency, and 250°C short-circuit (5 seconds) — exactly the same thermal rating as any other XLPE cable. Where older STA cables used PVC insulation (70°C limit), modern YJV22 / YJLV22 with XLPE delivers 30-40 percent higher ampacity at the same cross-section. For replacement of ageing PVC-insulated armoured cable (WAVECON, old NYY22), the XLPE upgrade allows the same physical cable size to carry significantly more current.

LV and MV in One Product Family

The same STA armour construction applies at 0.6/1 kV (IEC 60502-1, YJV22) and at 3.6/6 kV through 26/35 kV (IEC 60502-2, YJV22 with MV insulation). Projects spanning LV and MV distribution use a single product family with consistent construction, specification, and manufacturer documentation. For MV, the triple-extruded XLPE core with copper tape screen is identical to the unarmoured YJLV / N2XSBY — only the STA and outer sheath are added over the completed MV core.

Multi-Market Certified: IEC + BS + VDE + AS/NZS + SASO

Production certified to IEC 60502-1/2, plus BS 5467 (UK LV STA), BS 6622 and BS 7835 (UK MV STA, including LSZH), DIN VDE 0276-603/620 (Germany), HD 603 S1 / HD 620 S1 (CENELEC harmonised European), AS/NZS 5000.1 / AS/NZS 1429.1 (Australia/NZ), SASO 1694 (Saudi Arabia and Gulf). BASEC, KEMA, and SGS test reports available. For the UK construction market specifically, BS 5467 BASEC-certified STA cable is the standard acceptance reference for NICEIC, JIB, and Part P-approved installations.

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 make 360-degree contact with the steel tape layer to provide a low-resistance earth path — pigtail connections from individual tape strips to a lug have high contact resistance and poor mechanical retention. Specify the gland size for the cable OD (STA cable is slightly smaller OD than SWA at the same cross-section) and the material (brass standard; stainless for corrosive environments).

For direct-burial applications, the trench preparation determines whether the cable survives ground movement and compaction over decades. Minimum 100 mm sand or fine-soil bedding below the cable; minimum 150-300 mm sand or fine-soil above before backfilling with native soil. Remove any large stones, glass, or other angular material from the cable zone — STA provides good protection against distributed compressive loads but can be punctured by a single angular stone edge at concentrated point load. Warning tape or concrete tiles at 100-150 mm above the cable depth; cable route marker posts at changes of direction.

STA cable minimum bending radius is 12× OD per IEC 60502 (smaller than the 15× OD of SWA, because the tape construction bends more readily than round wire). Bending tighter than 12× OD permanently kinks the steel tape layers and splits the tape edge, leaving a crack in the armour that provides no mechanical protection at that point and a potential corrosion initiation site. The kink is invisible from outside but creates a failure location under concentrated compressive load. The tighter STA bending radius (vs SWA) allows routing through tighter duct bends and into junction boxes where SWA would not fit.

Cable expands and contracts with temperature — particularly significant for XLPE cable which operates over a wide temperature range from cold ground (−5°C) to full load (90°C conductor). Laying the cable in a gentle S-curve (snaking) allows 2-3 percent excess cable length in the trench to accommodate thermal movement without pulling the cable straight and tensioning the terminations. For straight-run cable in conduit, leave a small service loop at each joint box. Pulling the cable perfectly straight and tight at ambient temperature means it will be under tension at operating temperature, potentially pulling conductor lugs out of terminations.

Insulation resistance test (megger) at 1 kV DC between every conductor and earth (armour), and between adjacent conductors, before energising any buried cable installation. Expected reading for new LV YJV22 is > 1000 MΩ per km; readings below 100 MΩ indicate water ingress, insulation damage, or a termination fault — investigate and repair before applying mains voltage. Document the test results in the project handover. For MV installations, conduct both megger testing and partial-discharge testing as described in the YJLV medium-voltage cable product page.

The steel tape armour is not watertight — moisture enters easily through the inter-tape gaps. Apply heat-shrink end caps or self-amalgamating tape to cable ends immediately after cutting, before moving the cut cable to the installation location. For cable lengths in open trenches awaiting connection, seal both ends before any rain event. For cable pulled into conduit or duct before final termination, seal the exposed end at the duct entry point. Moisture wicking into the cable during the construction period sits inside for years and slowly degrades the XLPE insulation, reducing insulation resistance and ultimately causing premature breakdown.