LV armoured cables: laying and handling

Laying temperature and pre-warming

• The limit is the temperature of the cable itself, not of the air: a drum stored in the cold stays cold after the air warms.Sources: HD 620 Part 1 A.4.12; HD 603 3-G, 5-G, 3-I, 4-B; Nexans 2021 p. 11 (read in the standard text)
• Colder than its minimum: warm the whole drum for 1 to 2 days (at least 24 hours in HD 620 10-B). A full drum near the limit can take 20 to 30 hours to warm through (10-F).Sources: HD 620 Part 1 A.4.12; 10-F-20; 10-B-36 (read in the standard text)
• Nexans: Warm at +10 °C or more for at least 24 hours, then unreel within 2 hours at about 20 m/min; below -5 °C outside, postpone the pull or warm the drums first.Sources: Nexans 2021 p. 11 (maker's document)
• A cable stored below its minimum laying temperature takes no shocks, impacts, bending or twisting.Sources: HD 620 Part 1 A.3.1; HD 603 3-I 3.3; Nexans Belgium 2022 (read in the standard text)
• HD 603 3-G, 5-G · HD 620 10-A, 10-C, 10-F: Cable temperature while laying and fitting accessories: at least -5 °C with a PVC sheath, -20 °C with a PE sheath; warm the cable when it is colder.Sources: HD 603 3-G-15 item 2; 5-G-15 item 2; HD 620 10-A-25 item 14; 10-C-26 item 14; 10-F-21 (read in the standard text)
• Anixter: PVC and thermoplastic LSF turn brittle near 0 °C; elastomers stay flexible to -20 °C, but do not bend them to the minimum radius below -15 °C.Sources: Anixter Sec. 20 p. 20-43 (maker's document)

National rules

• India IS 1255: Warm a cable colder than 3 °C, whatever its insulation, in a heated building or a hot-air tent for at least 24 hours to about 10 °C, and lay it swiftly.Sources: IS 1255 8.4, p. 26 (read in the standard text)
• United Kingdom BS 6622, BS 5467, BS 7846: Cable and air above 0 °C for the previous 24 hours, or special precautions that keep the cable above 0 °C.Sources: BS 6622 C.1; BS 5467 B.2; BS 7846 A.7.2; HD 620 10-O-23; Anixter Sec. 20 p. 20-43 (read in the standard text)

Laying in winter? Pro checks your town and month against this limit. See Pro

Bending radius

• IEC 60502-1: Gives no installation bending radius; the values below come from HD 603.Sources: IEC 60502-1 text searched (read in the standard text)
• D is the cable's outer diameter. One controlled bend: a single bend next to a joint or termination, made by skilled workers over a template, the cable at or warmed to 30 °C.Sources: HD 620 Part 1 A.4.6; HD 603 3-G-16 (read in the standard text)
• HD 603 3-G, 5-G: While laying 15 D single core, 12 D multicore; for one controlled bend 7.5 D and 6 D.Sources: HD 603 3-G-16, 5-G-16 (read in the standard text)
• Prysmian UK: BS 5467, BS 6724, BS 7846: 8 D while laying.Sources: Prysmian UK p. 2 (maker's document)

National rules

• India IS 1255: PVC and XLPE: single core 15 D up to 11 kV, 20 D above; multicore 12 D up to 1.1 kV, 15 D above. Cores at joints and terminations: more than 12 times the diameter over the insulation.Sources: IS 1255 5.3, Table 5, p. 14; 5.3.2 (read in the standard text)
• Türkiye EKAT Çizelge-20: Three-core LV (XLPE or PVC) 12 D; three-core MV 15 D; armoured 15 D; single core 15 D.Sources: EKAT Madde 58 b) 9 (read in the standard text)
• Türkiye TEDAŞ: As printed by HES Kablo: unarmoured LV 12 D single core, 10 D multicore; unarmoured MV 14 D and 12 D; armoured 15 D and 12 D. It differs from EKAT Çizelge-20.Sources: HES Kablo p. 388 (maker's document)
• United Kingdom BS 5467, BS 6724: Installation radius: 6 D with circular copper conductors, 8 D with solid aluminium or shaped copper.Sources: BS 5467 Table B.1; BS 6724 Table B.1 (read in the standard text)
• United Kingdom BS 7846: 8 D while laying.Sources: BS 7846 A.7.3 (read in the standard text)

Pulling force and method

• On the conductors, with a pulling eye or head: at most 50 N/mm² for copper and 30 N/mm² for aluminium, over the main conductors' total section.Sources: HD 603 3-G-16 and the other guides to use; HD 620 Part 1 A.4.13 a; 10-C-26; IS 1255 5.4.2, p. 15; EKAT Madde 58 b) 10; Nexans 2021 p. 13; HES Kablo p. 391 (read in the standard text)
• Gather all conductors in the pulling head and clamp them together, so the force spreads evenly.Sources: HD 603 3-I; EKAT Madde 58 b) 10 (read in the standard text)
• A swivel between the cable grip and the pulling rope.Sources: HD 620 10-R item 15; Draka p. 6 (read in the standard text)
• Watch the tension all through a machine pull and keep the record with the as-laid documents. Prysmian: a winch with a dynamometer, a preset maximum and automatic stop; Draka: without a tension record the maker may refuse a claim.Sources: HD 620 Part 1 A.4.4; HD 603 3-G 3.3; IS 1255 10.3.5; Prysmian 2024 p. 10; Nexans 2021 p. 16; Draka p. 8 (read in the standard text)
• Rollers on straight runs every 2 to 4 m (Prysmian) or 3 to 4 m (Nexans for direct burial, IS 1255); at bends several rollers forming a radius larger than the minimum bending radius (IS 1255: corner rollers and at least three solid plates).Sources: HD 620 Part 1 A.4.4; HD 603 3-G 3.3; IS 1255 10.2.2, p. 30; Prysmian 2024 p. 10; Nexans 2021 p. 16, 17 (read in the standard text)
• Sidewall pressure: the maker's limit, checked before the pull at every bend, roller and deflection point; too much tears the sheath.Sources: BS 7846 A.7.4 d); Nexans 2021 p. 17; Anixter Sec. 20 p. 20-44 (read in the standard text)
• Guide the cable into a duct along its axis, with a bell mouth at the duct end, in one continuous arc without a reverse bend.Sources: BS 7846 A.7.4 f); IS 1255 6.3.4.4, 6.4.1; Nexans 2021 p. 17; Southwire 2005 p. 3 (read in the standard text)
• Cable laid out on the ground goes down in a figure of eight, never in rings: rings twist it.Sources: IS 1255 10.2.4.6, p. 32; Draka p. 9; Nexans 2021 p. 19 (read in the standard text)
• HD 603: On a cable grip: as on the conductors for unarmoured cables without a metal sheath (3-G, 5-G); 3 × D² N (3-I); 5 × D² N (3-L, 5-O, 5-P); at most 1000 N (4-B, 5-I, 6-A); at most 10 000 N (7-A, 7-B).Sources: HD 603 3-G-16, 3-I-20, 3-L-19, 4-B-18, 7-A-23, 7-B-20 (read in the standard text)

National rules

• India IS 1255: On a stocking: 9 × D² N for armoured PVC or XLPE cables, 5 × D² N unarmoured, 3 × D² N for armoured paper cables. For armoured cables that is three times the HD 620 value.Sources: IS 1255 5.4.1, p. 15; HD 620 Part 1 A.4.13 c (read in the standard text)
• India IS 1255: Expected winch force: 15 to 20 % of the cable's weight in a trench without large bends, 20 to 40 % with one or two 90° bends, 50 to 60 % with three, up to 100 % in ducts with bends totalling 360°.Sources: IS 1255 5.5, p. 16 (read in the standard text)
• United Kingdom BS 5467, BS 7846: The maximum tension is the maker's value.Sources: BS 5467 Q.4.2; BS 7846 A.7.4 c), d) (read in the standard text)

Work out the pull for your route: the verdict is free, the numbers and the PDF come with Pro. Pull calculation in the cable designer · See Pro

Depth, cover and laying

• Choose the way of laying and the bedding for the oversheath; trench walls smooth and free of stones.Sources: HD 620 Part 1 A.4.2 d), A.4.4; HD 603 3-G 1.2 d) (read in the standard text)
• Single-core cables: all three phases of one system through the same steel pipe or hole; fixings must not form a magnetic ring round one core.Sources: HD 620 Part 1 A.4.9 b); HD 603 3-G 1.4; 3-L 5.1.3; IS 1255 6.3.4.6, 8.8.4; EKAT Madde 58 b) 3, 7 (read in the standard text)
• Duct inner diameter at least 1.5 D in most HD sections and IS 1255, 1.5 to 2 D in HD 603 3-L, 5-O and 5-P, at least 1.4 D in the Italian sections; keep sand out of the duct.Sources: HD 603 3-G, 5-G, 3-L, 5-O, 5-P, 7-A; HD 620 10-A, 10-B, 10-C, 10-F, 10-I1, 10-R, 12-I; IS 1255 6.3.4.3, p. 18 (read in the standard text)

National rules

• Australia and New Zealand AS/NZS 3000: Armoured cable buried direct 500 mm (gardens, footpaths); conduit 300 mm in gardens, 750 mm under driveways. Summarised by a supplier: check AS/NZS 3000.Sources: AS/NZS 3000 (Wilken) (secondary source)
• France NF C 15-100, NF C 13-200: LV at least 0.50 m, HTA (MV) 0.80 m, 0.85 m under vehicle ways and pavements; a warning grid at least 0.20 m above the cable or its protection.Sources: Prysmian France pp. 1 to 2 (secondary source)
• Germany HD 603 3-G, 5-G · HD 620 10-A, 10-C: At least 0.6 m deep, 0.8 m below roads; shallower only with other protection.Sources: HD 603 3-G-15 item 1.3, 5-G-15; HD 620 10-A-25 item 11, 10-C-26 item 11 (read in the standard text)
• Hong Kong Code of Practice 25C(3)(a): Armoured or metal-sheathed cables only: at least 450 mm (category 1 and 3 circuits) or 750 mm (category 4); sand or fine soil at least one cable diameter below and 100 mm over, then cover tiles.Sources: Hong Kong CoP 25C(3)(a), p. 159 (read in the standard text)
• India IS 1255: At least 0.75 m to the top of the cable for LV and control cables, 0.9 m for 3.3 to 11 kV, 1.05 m for 22 and 33 kV, 1.0 m at road and railway crossings; at least 75 mm of riddled soil or sand below and above, then tiles, bricks or slabs.Sources: IS 1255 6.3.1, 6.3.2, 6.3.6, pp. 16, 19 (read in the standard text)
• Türkiye EKAT: At least 0.80 m under streets and squares, 0.60 m elsewhere, about 20 cm less with special protection where it cannot be avoided; road and rail crossings in pipes or channels, the top at least 1 m below the road surface or rail foot.Sources: EKAT Madde 58 b) 11, 16 (read in the standard text)
• Türkiye EKAT: About 10 cm of sieved sand below and above the cable; brick, a concrete slab of at least 6 cm or a plastic cover over the sand along the whole route; a PE warning tape at least 10 cm wide about 30 cm above the cover.Sources: EKAT Madde 58 b) 13 (read in the standard text)
• United Kingdom NJUG: Depth to the top of the cable: LV 450 mm under footways and verges, 600 mm under carriageways; HV 450 to 1200 mm and 750 to 1200 mm. Yellow marker tape directly above (HV: black and red legend, or concrete tiles).Sources: NJUG Table 1, p. 6 (read in the standard text)

Drum handling

• Keep the drum upright, its axis horizontal, in storage and in transport; never lay it flat on a flange.Sources: HD 620 Part 1 A.3.2.5, A.3.3.2; IS 1255 7.7, p. 25; Prysmian 2024; Reka (read in the standard text)
• Never drop a drum. Without lifting gear, use a ramp of about 1:4 (IS 1255: 1:3 to 1:4) with ropes or a winch and a sand bed at the foot.Sources: HD 620 Part 1 A.3.3.3; HD 603 3-I 3.3; IS 1255 7.3, p. 24; Prysmian 2024 p. 6; Reka p. 6; Nexans 2021 p. 4 (read in the standard text)
• Roll it only short distances on firm ground, in the direction of the arrow on the flange.Sources: HD 620 Part 1 A.3.3.4; HD 603 3-I, 3-L; IS 1255 7.4, p. 24; Prysmian 2024 p. 7; Nexans 2021 p. 3 (read in the standard text)
• Store it on level, firm, well-drained ground and turn it 90° every 3 months.Sources: IS 1255 7.5, 7.6, pp. 24 to 25; Prysmian 2024 p. 8, 9; Nexans 2021 p. 8, 9; Prysmian Türkiye 3.3 (read in the standard text)
• Leave the battens on until the cable is about to be laid: they keep off sun and knocks.Sources: HD 620 Part 1 A.3.2.5; BS 6622 D.5.2; IS 1255 7.8, p. 25; Nexans 2021 p. 11 (read in the standard text)
• Cable ends sealed with caps in transport, storage and laying. A cap missing for over a month, or a wet end: cut back 300 mm, check for moisture and cap again.Sources: HD 620 Part 1 A.3.2.3, A.4.7; HD 603 3-I 3.2; BS 6622 C.3; BS 5467 B.4; BS 7846 A.7.4; IS 1255 7.2, p. 24; Nexans 2021 p. 7; Draka (read in the standard text)
• Pay out tangentially, never over the flange, with the drum on an axle and jacks and braked. Top or bottom: IS 1255 says off the top; Southwire chooses by where the cable goes (the bottom into a floor conduit, the top into a tray); Nexans Belgium says the bottom, for safety.Sources: HD 620 Part 1 A.4.5; IS 1255 8.2, 8.3, 10.2; Southwire 2005 p. 2 to 3; Nexans Belgium FAQ; Prysmian 2024 p. 10; Draka p. 5, 9 (read in the standard text)
• HD 620 10-A, 10-C, 10-K · HD 603 3-L: Flange over 1.0 m: the drum axis horizontal in transport; in HD 603 3-L, drums over 2.5 t.Sources: HD 620 10-A-24 item 6; HD 603 3-L; Prysmian 2024 (read in the standard text)

Every rule for a chosen drum, with its lagging, weight and return terms: Cable drum calculator

Sheath test after laying

• HD 603 3-G, 5-G · HD 620 10-A, 10-C, 10-R: At most 3 kV d.c. on a PVC sheath, 5 kV d.c. on a PE sheath; faults usually show within 1 minute.Sources: HD 603 3-G 1.6, 5-G 1.6; HD 620 10-A 3.5, 10-C 3.5, 10-R 3.5 (read in the standard text)
• Look the cable over before burying it, trace it with a locator afterwards, and check the end caps after the pull.Sources: HD 620 10-R-18 item 1; IS 1255 8.7, p. 27; Nexans 2021 p. 13; Draka p. 8 (read in the standard text)

National rules

• India IS 1255: A d.c. test of the insulation after installation, 5 minutes, conductor to sheath: 3 kV (0.65/1.1 kV), 18 kV (6.35/11 kV), 37.5 kV (12.7/22 kV), 60 kV (19/33 kV). This goes against the HD 620 and BS 6622 advice not to test the insulation with d.c.Sources: IS 1255 14.2.4, Table 6, p. 60; HD 620 10-F, 10-K, 12-K; BS 6622 (read in the standard text)

The tests after installation for one cable, with their voltages, in the cable designer: Test after installation

Get the commissioning sheet for your own cable with Pro. See Pro