A 3x240 mm2 XLPE-insulated copper power cable weighs 8.5 kg per meter in the unarmoured 0.6/1 kV 3+2-core configuration (with two 120 mm2 neutrals), and 9.96 kg per meter in the BS 6724 XLPE/LSF/SWA armoured build of the same conductor size, based on manufacturer datasheets published in 2025 and 2026 [S4][S5].
Selection depends on three variables: neutral core count (3+1 versus 3+2), armouring (none, SWA, DSTA), and voltage class (0.6/1 kV LV versus 3.6/6 kV to 18/30 kV MV). Each adds measurable mass, and the gaps between configurations are large enough to break a drum-lift plan if the wrong row of a weight table is used [S3].
What 8.5 kg/m Actually Represents on a 3x240 mm2 XLPE Cable
The 8.5 kg/m figure (8,500 kg per 1,000 m) is the published value for a 0.6/1 kV CU/XLPE/PVC unarmoured cable with three 240 mm2 phase conductors and two 120 mm2 neutral/earth conductors, tested at 3.5 kV for 5 minutes per the manufacturer datasheet [S4]. The same 8,500 kg/1,000 m appears for the 3+1-core variant (3x240+1x120 mm2) at 0.6/1 kV, with a phase DC resistance of 0.0754 Ω/km at 20°C and an earth conductor resistance of 0.5 Ω/km [S6]. These two datasheets confirm that adding the second reduced neutral (going from 1x120 to 2x120) does not shift the headline weight on this particular supplier's build, because the second 120 mm2 replaces material that the 3+1 design carried as filler or smaller earth [S4][S6].
Copper density is the dominant contributor: 8.96 g/cm³ versus 1.4-1.5 g/cm³ for PVC and 0.91-0.96 g/cm³ for XLPE, so roughly 70-75% of the cable mass is copper conductor metal alone, with the remainder split between XLPE insulation, PVC bedding, fillers, and the outer sheath [S3]. For reference, a single-core 300 mm2 XLPE copper conductor weighs about 2.68 kg/m using standard copper density, which scales linearly with cross-section for a sanity check on any vendor's per-meter claim [S1].
How Armouring Pushes Weight From 8.5 kg/m to 9.96 kg/m
Adding galvanised steel wire armour (SWA) under an LSF sheath to a 3x240 mm2 XLPE/LSF cable increases mass to 9,960 kg/km (9.96 kg/m) at 600/1000 V per the BS 6724 datasheet row BS6724-3C-2400, with an overall diameter of 55.1 mm and a minimum fixed-bend radius of 450 mm [S5]. That is a 1.46 kg/m (17.2%) uplift over the unarmoured 3+2-core 8.5 kg/m figure, and it comes almost entirely from the steel wires and the thicker LSF inner and outer sheaths required to bed the armour [S5][S3].
The same BS 6724 table shows the scaling clearly across the 3-core range: 3x25 mm2 sits at 1,720 kg/km, 3x95 mm2 at 4,320 kg/km, 3x150 mm2 at 6,630 kg/km, 3x185 mm2 at 7,980 kg/km, 3x240 mm2 at 9,960 kg/km, and 3x300 mm2 at 12,060 kg/km, a near-linear march with conductor copper area once the fixed armour overhead is absorbed [S5]. The 3-core BS 6724 cable carries a 90°C maximum conductor operating temperature, 600/1000 V or 1900/3300 V rating, and LSF sheath compliance to BS EN 60332-3-24 Cat. C for flame propagation, which is the standard reference for indoor, tunnel, and offshore-platform LV distribution in fire-sensitive zones [S5].
Comparison: Unarmoured vs SWA vs DSTA at 3x240 mm2
Engineers picking between the three main 0.6/1 kV constructions should match the following decision criteria, drawn directly from the cited datasheets [S4][S5][S3]:
Double steel tape armour (DSTA) typically lands between the two, heavier than unarmoured but lighter than SWA on a like-for-like 3-core build, because the tape adds concentric steel without the bulk of round wire [S3][S5].
Mechanical protection: SWA handles high impact and tension loads, suited to direct burial, outdoor trench, and areas where the cable may be disturbed after install. DSTA handles moderate crushing but limited tension, often used in indoor cable trays where crushing is the main risk. Unarmoured requires conduit, duct, or tray with no mechanical stress expected [S3][S5].
Fire performance: XLPE/LSF/SWA builds to BS 6724 meet BS EN 60332-3-24 Cat. C as a minimum, the right call for confined-space and life-safety circuits. Unarmoured CU/XLPE/PVC is the default for outdoor substation and industrial LV distribution where smoke toxicity is less critical [S5].
Bend radius and drum handling: SWA at 3x240 mm2 needs a 450 mm minimum fixed bend, against roughly 8-10x overall diameter for unarmoured equivalents, which on a 55.1 mm OD cable means around 440-550 mm anyway. The 17% mass penalty directly inflates drum weight: a standard 1,000 m drum of unarmoured 3x240+2x120 is 8.5 tonnes, while the SWA build is 9.96 tonnes, both above the 4-tonne single-lift threshold that most site cranes allow without a spreader beam and certified sling set [S4][S5].
Standards, Sourcing, and What Specifiers Should Verify
XLPE-insulated LV power cables to 0.6/1 kV are typically built to IEC 60502-1, with the 3+2-core 3x240+2x120 mm2 datasheet citing that designation directly, while the BS 6724 SWA cable adds BS 7655 insulation and sheath type references, BS EN 10257-1 for the galvanised steel armour wire, and BS EN 60332-3-24 for flame propagation [S4][S5]. Medium-voltage XLPE cables to 18/30 (36) kV follow IEC 60502-2 and BS 6622, and they sit outside the 0.6/1 kV weight figures discussed here, because MV designs add a thicker insulation screen, semi-conductive layers, and a metallic screen that each add their own per-meter mass [S2].
For cross-vendor comparison, the same 3x240 mm2 cross-section also appears in IEC 60228 maximum DC resistance at 20°C: copper and aluminum conductor tables, which sets the 0.0754 Ω/km DC ceiling that the 8.5 kg/m datasheet meets at full nominal area, a useful sanity check when an unfamiliar supplier submits a 3x240 mm2 datasheet with no test report attached. Specifiers working on utility and industrial LV distribution should also confirm the cable's power cable construction against the project's power distribution single-line diagram, because the 3+2-core 8.5 kg/m figure assumes a PEN or split-neutral arrangement, while a 3+1-core 3x240+1x120 typically feeds a separate-earth system and may need a different power meter CT ratio to balance correctly. The multifunction power meter class on the downstream panel should also be checked against the cable's 90°C XLPE rating, because conductor temperature under load changes both resistance and the meter's CT burden calculation.
Trackable Signals for the Next Spec Cycle
