Application & Operating Conditions
BS 6708 Type 621 is a heavy-duty 3800/6600 V (3.8/6.6 kV) pliable wire armoured flexible power supply cable engineered for high-capacity underground and surface mining excavators, primary rock-crushing stations, dragline auxiliary substations, and movable 6.6 kV main roadway distribution feeders in explosive gas and dust environments.
6.6 kV High-Capacity Primary Feeders
Delivers up to 320 A at 3.8/6.6 kV (over 3.6 MVA three-phase power on 4×150 mm²) to heavy excavating, crushing, and longwall transformer skids.
5.0 mm Heavy-Wall EPR + 15 kV AC Test
All four cores (three phases plus one full-cross-section pilot core) carry a uniform 5.0 mm radial EPR dielectric wall proven by a 15 kV AC routine withstand test.
Heavy 7/1.25 mm Pliable Steel Armour
Protected by 7/0.90 mm (4×35) and 7/1.25 mm (4×50 to 4×150) stranded galvanized steel pliable armour (0.35–0.70 Ω/km) beneath an extra-thick 6.0–8.3 mm PCP outer jacket.
6.6 kV Screened vs Unscreened Armoured Choice: BS 6708 Type 621 provides 4 unscreened 5.0 mm EPR cores (3 phases + 1 pilot) inside pliable steel armour. If your 3.8/6.6 kV network requires individually composite-screened MV phase cores inside pliable wire armour, specify BS 6708 Type 630 (3-core) or Type 631 (3-core + earth).
Cable Construction (BS 6708 Type 621 — 3.8/6.6 kV Armoured)
Built to withstand extreme underground rockfall crush forces and 15 kV dielectric stress while preserving Class 5 conductor and stranded pliable-armour handling flexibility.
| Layer / Component | Material & BS 6708 Engineering Specification |
|---|---|
| 1. Conductors (4 Equal Cores) | Electrolytic flexible stranded tinned copper wire, IEC 60228 Class 5 (4×35 mm² to 4×150 mm²; 276/0.40 mm up to 756/0.50 mm stranding) for three phase cores and one pilot core. |
| 2. Medium-Voltage Insulation | High-grade Ethylene Propylene Rubber (EPR) extruded to 5.0 mm nominal radial wall thickness across all cross-sections. |
| 3. Core Lay-Up | Three unscreened phase cores and one unscreened pilot core laid up in contact with each other in a symmetrical 4-core assembly. |
| 4. Inner Sheath / Bedding | Heavy extruded rubber-based inner bedding compound: 3.8 mm radial thickness on 4×35 mm²; 5.0 mm radial thickness on 4×50 through 4×150 mm². |
| 5. Pliable Wire Armour (PWA) | Helical galvanized steel pliable wire strand armour (7/0.90 mm on 4×35 mm²; 7/1.25 mm on 4×50 through 4×150 mm²) between inner and outer sheaths. |
| 6. Outer Sheath | Extra-heavy-duty black chloroprene (PCP) outer sheath (6.0 mm to 8.3 mm radial thickness), flame-retardant, oil-resistant, and tear-resistant. |
BS 6708 Type 621 Cross-Section: Four unscreened 5.0 mm wall EPR cores (3 phases + 1 pilot) cushioned in 3.8–5.0 mm rubber inner bedding, armoured with 7/0.90–7/1.25 mm galvanized steel pliable wire strands, and oversheathed in 6.0–8.3 mm black PCP.
Technical Characteristics
Electrical, routine 15 kV test, dimensional, and armour conductance parameters in accordance with BS 6708 Type 621.
| Parameter | BS 6708 Rated Value |
|---|---|
| Reference Standard | BS 6708 (Type 621 3800/6600 V Pliable Wire Armoured Mining Power Cable) |
| Rated Voltage (Uo/U) | 3800 / 6600 V AC (3.8 / 6.6 kV) |
| Routine AC Test Voltage | 15 kV AC |
| Cross-Section Range | 4×35, 4×50, 4×70, 4×95, 4×120, and 4×150 mm² |
| Insulation Radial Thickness | 5.0 mm EPR on all sizes |
| Pliable Armour Construction | 7/0.90 mm (4×35 mm²) | 7/1.25 mm (4×50 to 4×150 mm²) |
| Minimum Bending Radius | 752 mm (4×35 mm²) to 1076 mm (4×150 mm²) (10 × Max. OD) |
| Continuous Current & Armour Res. | 135–320 A (@ 25 °C) | Armour Max. DC Res.: 0.70 to 0.35 Ω/km (@ 20 °C) |
BS 6708 Type 621 Complete Specification & Electrical Tables (6 Sizes)
Complete conductor, insulation, inner/outer sheath, pliable armour, diameter, bend radius, weight, current, and DC resistance data for BS 6708 Type 621.
1. Core, Sheath, Pliable Armour & Overall Dimensions (4×35 to 4×150 mm²)
| Nominal Size (mm²) | Stranding (No./mm) | Cond. Dia. (mm) | Insul. Thick. (mm) | Inner Sheath (mm) | Inner Dia. Min–Max (mm) | Armour Size (No./mm) | Outer Sheath (mm) | Min. OD (mm) | Max. OD (mm) | Min. Bend Radius (mm) | Approx. Weight (kg/km) | Copper Weight (kg/km) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 4×35 | 276/0.40 | 8.40 | 5.0 | 3.8 | 53.8 – 56.8 | 7/0.90 | 6.0 | 71.2 | 75.2 | 752 | 8900 | 1350 |
| 4×50 | 396/0.40 | 10.10 | 5.0 | 5.0 | 60.5 – 63.5 | 7/1.25 | 6.3 | 81.0 | 85.3 | 853 | 11100 | 1950 |
| 4×70 | 360/0.50 | 11.90 | 5.0 | 5.0 | 65.6 – 69.4 | 7/1.25 | 7.0 | 87.1 | 91.4 | 914 | 13000 | 2700 |
| 4×95 | 475/0.50 | 13.90 | 5.0 | 5.0 | 70.7 – 74.5 | 7/1.25 | 7.5 | 93.2 | 97.5 | 975 | 14050 | 3700 |
| 4×120 | 608/0.50 | 15.50 | 5.0 | 5.0 | 74.3 – 78.1 | 7/1.25 | 7.8 | 97.4 | 101.7 | 1017 | 20600 | 4650 |
| 4×150 | 756/0.50 | 17.20 | 5.0 | 5.0 | 79.2 – 83.2 | 7/1.25 | 8.3 | 103.3 | 107.6 | 1076 | 22000 | 5800 |
2. Continuous Current Ratings & Conductor / Armour DC Resistance
| Nominal Size (mm²) | Continuous Current @ 25 °C (A) | Conductor Max. DC Res. @ 20 °C (Ω/km) | Armour Max. DC Res. @ 20 °C (Ω/km) |
|---|---|---|---|
| 4×35 | 135 | 0.565 | 0.70 |
| 4×50 | 170 | 0.393 | 0.50 |
| 4×70 | 205 | 0.277 | 0.43 |
| 4×95 | 250 | 0.210 | 0.39 |
| 4×120 | 295 | 0.164 | 0.38 |
| 4×150 | 320 | 0.132 | 0.35 |
Selection Guide: BS 6708 Pliable Wire Armoured Mining Feeders
Compare BS 6708 Type 621 (3.8/6.6 kV) against 1.9/3.3 kV Type 321/331 and 640/1100 V Type 20/21 & Type 201/211 armoured cables.
| BS 6708 Model | Core & Pilot Architecture, Earth Design & Primary Duty |
|---|---|
| BS 6708 Type 20 & Type 21 (640/1100V Unscreened PWA) | BS 6708 Type 20 & Type 21 (640/1100V Unscreened PWA): 3-core (Type 20) and 4-core (Type 21) unscreened EPR power cables (2.5–150 mm², 24 sizes) with 7/0.45–7/1.25 mm galvanized steel pliable wire armour. |
| BS 6708 Type 62, 63 & 64 (640/1100V Screened 4 mm² PWA) | BS 6708 Type 62, 63 & 64 (640/1100V Screened 4 mm² PWA): 2×4, 3×4, and 4×4 mm² individually composite-screened pliable wire armoured cables for 640/1100 V coalface lighting and auxiliary equipment. |
| BS 6708 Type 201 & Type 211 (640/1100V Yellow-Stripe Roadway) | BS 6708 Type 201 & Type 211 (640/1100V Yellow-Stripe Roadway): BS 6708:1998 3-core (Type 201) and 3+Earth (Type 211) copper/nylon screened MEPR roadway & quarry trailing cables (10–120 mm²) with yellow-striped black PCP jacket. |
| BS 6708 Type 321 & Type 331 (1.9/3.3kV Blue-Stripe Roadway) | BS 6708 Type 321 & Type 331 (1.9/3.3kV Blue-Stripe Roadway): BS 6708:1998 1900/3300 V medium-voltage pliable wire armoured roadway & quarry trailing cables (25–150 mm²; screened Type 331 / unscreened Type 321) with blue-striped black PCP sheath. |
| BS 6708 Type 621 (3.8/6.6kV Heavy MV Armoured) (This Product) | 3800/6600 V medium-voltage 4-core (3 phases + 1 pilot, 4×35–4×150 mm²) unscreened 5.0 mm EPR pliable wire armoured power cable tested at 15 kV AC. |
| BS 6708 Type 70 & Type 71 (320/550V Lighting PWA) | BS 6708 Type 70 & Type 71 (320/550V Lighting PWA): 4×4 and 5×4 mm² 320/550 V unscreened pliable wire armoured cables for low-voltage coalface lighting strings. |
Frequently Asked Questions (FAQ)
Engineering FAQs covering BS 6708 Type 621 earth-fault conductance, drum handling, and 15 kV dielectric testing.
How is the protective earth circuit carried in BS 6708 Type 621?
In BS 6708 Type 621, the four insulated cores serve as three 6.6 kV phase conductors plus one full-sized pilot core, while the heavy helical 7/0.90 mm or 7/1.25 mm galvanized steel pliable wire armour provides the main metallic earth-return path with a low maximum DC resistance of 0.70 Ω/km (4×35) down to 0.35 Ω/km (4×150) at 20 °C.
Why is the minimum bending radius 10 × OD on Type 621?
Because each core carries a thick 5.0 mm medium-voltage EPR dielectric wall plus 5.0 mm inner bedding, 7/1.25 mm steel strand armour, and up to 8.3 mm PCP outer sheath (up to 107.6 mm OD), maintaining at least 10 × Max. OD (752–1076 mm) prevents mechanical strain on the 6.6 kV insulation during reeling and installation.
Can TEBAOFLEX supply Type 621 on heavy-duty steel export drums?
Yes. With cable weights ranging from 8,900 kg/km to 22,000 kg/km, we supply BS 6708 Type 621 on reinforced flange steel drums engineered to project cut lengths, complete with 15 kV AC high-voltage test certificates.
Request a Quote for BS 6708 Type 621 3.8/6.6 kV Armoured Cable
Share your required cross-section (4×35 to 4×150 mm²), cut lengths, and project destination for direct TEBAOFLEX factory pricing and drum shipping weights.
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