Application & Operating Conditions
BS 6708 Type 307, Type 307M, and Type 307S are unarmoured 1900/3300 V (1.9/3.3 kV) heavy-duty flexible trailing cables engineered to power high-output longwall shearers, coalcutters, continuous miners, roadheaders, and mobile excavating or crushing equipment in deep underground coal mines where explosive methane and coal dust accumulate, as well as surface quarries.
Type 307: Standard Single Pilot (25–150 mm²)
Combines 3 composite-screened 3.3 kV phase cores with 1 unscreened EPR pilot core (16–95 mm²) and a central bare tinned copper earth conductor across 7 standard cross-sections.
Type 307M: Screened Full-Size Pilot (25–120 mm²)
Upgrades the single pilot conductor to match the full phase cross-section and encloses it in a fourth composite copper/nylon braided screen (0.25–0.45 Ω/km parallel screen+earth resistance).
Type 307S: 3-Core Pilot Unit (50–120 mm²)
Replaces the single pilot core with a jacketed 3-core pilot sub-assembly (3×4, 3×6, or 3×10 mm² tested at 2.5 kV AC) for multi-channel cutter telemetry, water-spray interlock, and remote stop.
1.9/3.3 kV vs 640/1100 V Family Equivalent: The BS 6708 Type 307 / 307M / 307S series is the direct 1900/3300 V medium-voltage counterpart to our 640/1100 V Type 7, Type 7M, and Type 7S coalcutter trailing cables—retaining identical pilot-interlock topologies while stepping up to heavy-wall 7.5 kV-tested EPR insulation.
Cable Construction (BS 6708 Type 307, Type 307M & Type 307S)
All three models share a symmetric 4-lobe core lay-up around a central uninsulated tinned copper earth conductor, ensuring every composite metallic screen stays in continuous electrical contact with earth throughout cable flexing.
| Layer / Component | Material & BS 6708 Engineering Specification |
|---|---|
| 1. Phase Conductors | Electrolytic flexible stranded tinned copper wire, IEC 60228 Class 5 (25 mm² to 150 mm²; 196/0.40 mm up to 756/0.50 mm stranding). |
| 2. Phase Insulation & ID | Medium-voltage Ethylene Propylene Rubber (EPR) dielectric rated for 1900/3300 V (7.5 kV AC test), wrapped with coloured textile identification tape. |
| 3. Phase Core Screens | Individual composite tinned copper wire and nylon yarn braided screen applied over all three phase cores. |
| 4. Pilot Core / Sub-Unit | Type 307: 1 unscreened EPR pilot core (16–95 mm²). Type 307M: 1 composite-screened EPR pilot core equal to phase size (25–120 mm²). Type 307S: 1 unscreened 3-core EPR pilot sub-unit (3×4, 3×6, or 3×10 mm², sheathed to 17.80–23.60 mm dia.). |
| 5. Central Bare Earth & Lay-Up | Uninsulated stranded Class 5 tinned copper earth conductor (25–95 mm²) positioned at the cable centre in direct contact with the surrounding screened cores. |
| 6. Inner Bedding & Outer Sheath | Extruded rubber-based inner bedding compound followed by a heavy-duty black chloroprene (PCP) outer sheath resistant to coalface abrasion, hydraulic oils, water, and flame spread. |
BS 6708 Type 307 (25–150 mm²): 3 composite-screened phase cores + 1 unscreened single pilot core + central bare earth.
BS 6708 Type 307M (25–120 mm²): 3 composite-screened phase cores + 1 composite-screened full-size pilot core + central bare earth.
BS 6708 Type 307S (50–120 mm²): 3 composite-screened phase cores + 1 unscreened 3-core pilot unit (3×4 to 3×10 mm²) + central bare earth.
Technical Characteristics
Electrical test levels, continuous and intermittent current ratings, reactance, insulation resistance, and mechanical limits per BS 6708.
| Parameter | BS 6708 Rated Value |
|---|---|
| Reference Standard | BS 6708 (Types 307, 307M & 307S 1900/3300 V Flexible Coalcutter Trailing Cables) |
| Rated Voltage (Uo/U) | 1900 / 3300 V AC (1.9 / 3.3 kV) |
| Routine AC Test Voltage | 7.5 kV AC on 3.3 kV Cores (2.5 kV AC on Type 307S 3-Core Pilot Conductors) |
| Continuous / Intermittent Current (@ 25 °C) | 110–320 A Continuous | 130–385 A Intermittent |
| Minimum Bending Radius | 399 mm (25 mm²) to 640 mm (150 mm²) (approx. 8 × Max. OD) |
| Maximum Pulling Tension | 640–642 kgf (25 mm²) up to 2000 kgf (95–150 mm²) |
| Minimum Insulation Resistance (@ 20 °C) | 600 MΩ·km (150 mm²) up to 1250 MΩ·km (25 mm²) |
| Nominal Reactance (50 Hz / 60 Hz) | 0.098–0.125 Ω/km (50 Hz) / 0.118–0.150 Ω/km (60 Hz) |
BS 6708 Type 307, Type 307M & Type 307S Complete Specification Tables (17 Sizes)
Use the architectural comparison matrix and individual model specification tables below to verify exact conductor stranding, screen diameters, overall diameters, weights, current ratings, and impedances.
0. Architectural Comparison: BS 6708 Type 307 vs Type 307M vs Type 307S
| BS 6708 Model | Phase Size Range | Phase Screen Design | Pilot Core Architecture | Central Earth Conductor | Parallel Screen + Earth Res. (Ω/km) | Routine AC Test |
|---|---|---|---|---|---|---|
| Type 307 (7 Sizes) | 3×25 to 3×150 mm² | 3 Composite Copper/Nylon Screens | 1 Unscreened Single Pilot (16–95 mm²) | Bare Class 5 Tinned Copper (25–95 mm²) | 0.14 – 0.50 | 7.5 kV |
| Type 307M (6 Sizes) | 3×25 to 3×120 mm² | 3 Composite Copper/Nylon Screens | 1 Screened Equal-Size Pilot (25–120 mm²) | Bare Class 5 Tinned Copper (25–70 mm²) | 0.25 – 0.45 (4 Screens + E) | 7.5 kV |
| Type 307S (4 Sizes) | 3×50 to 3×120 mm² | 3 Composite Copper/Nylon Screens | 1 Unscreened 3-Core Pilot Unit (3×4–3×10 mm²) | Bare Class 5 Tinned Copper (35–70 mm²) | 0.28 – 0.35 | 7.5 kV / 2.5 kV |
1. BS 6708 Type 307 (Unscreened Single Pilot) — Dimensions, Bend Radius, Pull & Weights (7 Sizes)
| Designation (Ph+E+Pi) | Phase Strand (Dia. mm) | Phase Insul. / Screen Dia. (mm) | Earth CSA & Strand | Pilot CSA & Insul. Dia. (mm) | Min. OD (mm) | Max. OD (mm) | Min. Bend (mm) | Max. Pull (kgf) | Approx. Weight (kg/km) | Copper Weight (kg/km) |
|---|---|---|---|---|---|---|---|---|---|---|
| 3×25+25+16 | 196/0.40 (7.00) | 13.10 / 15.50 | 1×25 (196/0.40) | 1×16 (11.60) | 47.4 | 49.9 | 400 | 640 | 4000 | 1654 |
| 3×35+25+16 | 276/0.40 (8.50) | 14.70 / 17.10 | 1×25 (196/0.40) | 1×16 (11.60) | 51.6 | 54.6 | 440 | 830 | 4800 | 1948 |
| 3×50+35+25 | 396/0.40 (10.00) | 15.70 / 17.70 | 1×35 (276/0.40) | 1×25 (13.10) | 56.8 | 59.8 | 480 | 1200 | 6150 | 2666 |
| 3×70+50+35 | 360/0.50 (11.70) | 17.70 / 19.70 | 1×50 (396/0.40) | 1×35 (14.70) | 62.8 | 65.8 | 525 | 1680 | 7600 | 3482 |
| 3×95+50+50 | 475/0.50 (13.50) | 19.10 / 21.10 | 1×50 (396/0.40) | 1×50 (15.70) | 68.9 | 72.7 | 580 | 2000 | 9250 | 4346 |
| 3×120+70+70 | 608/0.50 (15.40) | 21.40 / 23.40 | 1×70 (360/0.50) | 1×70 (17.70) | 73.4 | 77.2 | 615 | 2000 | 11200 | 5450 |
| 3×150+70+95 | 756/0.50 (17.20) | 23.00 / 25.00 | 1×70 (475/0.50*) | 1×95 (19.10) | 75.9 | 79.7 | 640 | 2000 | 13000 | 6000 |
2. BS 6708 Type 307 — Current Ratings, DC Resistance, Reactance & Voltage Drop
| Designation (Ph+E+Pi) | Cont. Current @ 25 °C (A) | Interm. Current @ 25 °C (A) | Phase DC Res. (Ω/km) | Pilot DC Res. (Ω/km) | 3 Screens + Earth DC Res. (Ω/km) | Reactance 50/60 Hz (Ω/km) | Min. Insul. Res. (MΩ·km) | 3-Ph Volt. Drop (mV/A/m) |
|---|---|---|---|---|---|---|---|---|
| 3×25+25+16 | 110 | 130 | 0.795 | 1.240 | 0.50 | 0.125 / 0.150 | 1250 | 1.69 |
| 3×35+25+16 | 135 | 155 | 0.565 | 1.240 | 0.50 | 0.117 / 0.141 | 1100 | 1.21 |
| 3×50+35+25 | 170 | 210 | 0.393 | 0.795 | 0.35 | 0.113 / 0.136 | 950 | 0.85 |
| 3×70+50+35 | 205 | 255 | 0.277 | 0.565 | 0.35 | 0.108 / 0.129 | 820 | 0.61 |
| 3×95+50+50 | 250 | 315 | 0.210 | 0.393 | 0.28 | 0.105 / 0.126 | 720 | 0.48 |
| 3×120+70+70 | 295 | 360 | 0.164 | 0.277 | 0.28 | 0.101 / 0.121 | 660 | 0.39 |
| 3×150+70+95 | 320 | 385 | 0.132 | 0.210 | 0.14 | 0.098 / 0.118 | 600 | 0.32 |
3. BS 6708 Type 307M (Screened Full-Size Pilot) — Dimensions, Bend Radius, Pull & Weights (6 Sizes)
| Designation (Ph+E+Pi) | Phase & Pilot Strand (Dia. mm) | Insul. / Screen Dia. (mm) | Earth CSA & Strand | Min. OD (mm) | Max. OD (mm) | Min. Bend (mm) | Max. Pull (kgf) | Approx. Weight (kg/km) | Copper Weight (kg/km) |
|---|---|---|---|---|---|---|---|---|---|
| 3×25+25+25 | 196/0.40 (6.75) | 13.10 / 15.50 | 1×25 (196/0.40) | 47.4 | 49.9 | 399 | 642 | 4200 | 1664 |
| 3×35+25+35 | 276/0.40 (8.35) | 14.75 / 17.10 | 1×25 (196/0.40) | 51.6 | 54.6 | 437 | 834 | 5000 | 2048 |
| 3×50+35+50 | 396/0.40 (9.40) | 15.80 / 18.20 | 1×35 (276/0.40) | 56.8 | 59.8 | 478 | 1200 | 6500 | 2866 |
| 3×70+50+70 | 360/0.50 (11.35) | 17.80 / 20.15 | 1×50 (396/0.40) | 62.8 | 65.8 | 526 | 1680 | 8100 | 3682 |
| 3×95+50+95 | 475/0.50 (12.75) | 19.20 / 21.60 | 1×50 (396/0.40) | 68.9 | 72.7 | 581 | 2000 | 9800 | 4546 |
| 3×120+70+120 | 608/0.50 (15.10) | 21.60 / 23.95 | 1×70 (360/0.50) | 73.4 | 77.4 | 617 | 2000 | 11600 | 5650 |
4. BS 6708 Type 307M — Current Ratings, DC Resistance, Reactance & Voltage Drop
| Designation (Ph+E+Pi) | Cont. Current @ 25 °C (A) | Interm. Current @ 25 °C (A) | Phase DC Res. (Ω/km) | Pilot DC Res. (Ω/km) | 4 Screens + Earth DC Res. (Ω/km) | Reactance 50/60 Hz (Ω/km) | Min. Insul. Res. (MΩ·km) | 3-Ph Volt. Drop (mV/A/m) |
|---|---|---|---|---|---|---|---|---|
| 3×25+25+25 | 110 | 130 | 0.795 | 0.795 | 0.45 | 0.125 / 0.150 | 1250 | 1.69 |
| 3×35+25+35 | 135 | 155 | 0.565 | 0.565 | 0.45 | 0.117 / 0.141 | 1100 | 1.21 |
| 3×50+35+50 | 170 | 210 | 0.393 | 0.393 | 0.31 | 0.113 / 0.136 | 950 | 0.85 |
| 3×70+50+70 | 205 | 255 | 0.277 | 0.277 | 0.31 | 0.108 / 0.129 | 820 | 0.61 |
| 3×95+50+95 | 250 | 315 | 0.210 | 0.210 | 0.25 | 0.105 / 0.126 | 720 | 0.48 |
| 3×120+70+120 | 295 | 360 | 0.164 | 0.164 | 0.25 | 0.101 / 0.121 | 660 | 0.39 |
5. BS 6708 Type 307S (Unscreened 3-Core Pilot Unit) — Dimensions, Bend Radius, Pull & Weights (4 Sizes)
| Designation (Ph+E+3Pi) | Phase Strand (Dia. mm) | Phase Insul. / Screen Dia. (mm) | Earth CSA & Strand | Pilot Unit CSA & Sheath Dia. (mm) | Min. OD (mm) | Max. OD (mm) | Min. Bend (mm) | Max. Pull (kgf) | Approx. Weight (kg/km) | Copper Weight (kg/km) |
|---|---|---|---|---|---|---|---|---|---|---|
| 3×50+35+3×4 | 396/0.40 (9.40) | 15.80 / 18.20 | 1×35 (276/0.40) | 3×4 (17.80) | 56.8 | 59.8 | 478 | 1200 | 5850 | 2685 |
| 3×70+50+3×6 | 360/0.50 (11.35) | 17.80 / 20.15 | 1×50 (396/0.40) | 3×6 (19.80) | 62.8 | 65.8 | 526 | 1680 | 7150 | 3319 |
| 3×95+50+3×6 | 475/0.50 (12.75) | 19.20 / 21.60 | 1×50 (396/0.40) | 3×6 (21.20) | 68.9 | 72.7 | 581 | 2000 | 8600 | 4039 |
| 3×120+70+3×10 | 608/0.50 (15.10) | 21.60 / 23.95 | 1×70 (360/0.50) | 3×10 (23.60) | 73.4 | 77.2 | 617 | 2000 | 10500 | 4951 |
6. BS 6708 Type 307S — Current Ratings, DC Resistance, Reactance & Voltage Drop
| Designation (Ph+E+3Pi) | Cont. Current @ 25 °C (A) | Interm. Current @ 25 °C (A) | Phase DC Res. (Ω/km) | Pilot Unit DC Res. (Ω/km) | 3 Screens + Earth DC Res. (Ω/km) | Reactance 50/60 Hz (Ω/km) | Min. Insul. Res. (MΩ·km) | 3-Ph Volt. Drop (mV/A/m) |
|---|---|---|---|---|---|---|---|---|
| 3×50+35+3×4 | 170 | 210 | 0.393 | 5.09 | 0.35 | 0.113 / 0.136 | 950 | 0.85 |
| 3×70+50+3×6 | 205 | 255 | 0.277 | 3.39 | 0.35 | 0.108 / 0.129 | 820 | 0.61 |
| 3×95+50+3×6 | 250 | 315 | 0.210 | 3.39 | 0.28 | 0.105 / 0.126 | 720 | 0.48 |
| 3×120+70+3×10 | 295 | 360 | 0.164 | 1.95 | 0.28 | 0.101 / 0.121 | 660 | 0.39 |
Selection Guide: BS 6708 Medium-Voltage (1.9/3.3 kV & 3.8/6.6 kV) Mining Cables
Compare unarmoured 3.3 kV coalcutter trailing cables (Type 307/307M/307S) against 3.3 kV armoured roadway cables (Type 321/331) and 6.6 kV feeders (Type 621, Type 630/631, Type 730).
| BS 6708 Model | Core & Pilot Architecture, Earth Design & Primary Duty |
|---|---|
| BS 6708 Type 307 / 307M / 307S (1.9/3.3kV Coalcutter Trailing) (This Product) | Unarmoured 1900/3300 V flexible coalcutter trailing cables (25–150 mm², 17 sizes) with 3 composite-screened EPR phases, central bare earth, and single (307), screened (307M), or 3-core (307S) pilot options. |
| BS 6708 Type 321 & Type 331 (1.9/3.3kV Blue-Stripe Armoured) | BS 6708 Type 321 & Type 331 (1.9/3.3kV Blue-Stripe Armoured): BS 6708:1998 1900/3300 V pliable wire armoured roadway extension & quarry trailing cables (25–150 mm²) with blue-striped black PCP sheath. |
| BS 6708 Type 621 (3.8/6.6kV Unscreened Armoured) | BS 6708 Type 621 (3.8/6.6kV Unscreened Armoured): 3800/6600 V pliable wire armoured 4-core (3 phases + 1 pilot, 4×35–4×150 mm²) unscreened 5.0 mm EPR power feeder. |
| BS 6708 Type 630 & Type 631 (3.8/6.6kV Screened Armoured) | BS 6708 Type 630 & Type 631 (3.8/6.6kV Screened Armoured): 3.8/6.6 kV individually composite-screened pliable wire armoured mining power cables (Type 630 3-core 35–150 mm²; Type 631 3+Earth 50–70 mm²). |
| BS 6708 Type 730 (3.8/6.6kV Unarmoured Screened Trailing) | BS 6708 Type 730 (3.8/6.6kV Unarmoured Screened Trailing): Unarmoured 3800/6600 V flexible screened trailing cable (3×35 to 3×150+16 mm²) for large mobile mining excavators and primary crushers. |
| BS 6708 Type 7 / 7M / 7S (640/1100V Coalcutter Trailing) | BS 6708 Type 7 / 7M / 7S (640/1100V Coalcutter Trailing): Low-voltage 640/1100 V unarmoured coalcutter trailing cables (16–150 mm²) for standard face shearers and roadheaders. |
Frequently Asked Questions (FAQ)
Engineering FAQs covering pilot option selection (307 vs 307M vs 307S), coupler compatibility, and intermittent shearer load ratings.
How do I choose between BS 6708 Type 307, Type 307M, and Type 307S for a 3.3 kV longwall shearer?
Select Type 307 when your 3.3 kV gate-end contactor uses a standard single intrinsically safe pilot-earth continuity loop. Select Type 307M when mine electrical standards require full-cross-section radial screening over the pilot core itself so pilot-to-phase faults cannot occur without first intercepting an earthed screen. Select Type 307S when the shearer requires three independent pilot/control cores (3×4 to 3×10 mm²) inside the main power cable.
Do Type 307, Type 307M, and Type 307S share identical outer diameters for 3.3 kV plug/socket glands?
Yes! BS 6708 engineers all three variants to identical overall diameter envelopes at each phase size—for example, at 3×95 mm² all three variants measure 68.9–72.7 mm OD, and at 3×50 mm² all three measure 56.8–59.8 mm OD—ensuring seamless gland interchangeability across standard 3.3 kV flameproof mining couplers.
What is the difference between the continuous and intermittent current ratings?
Continuous ratings (110–320 A at 25 °C ambient) apply to uninterrupted full-shift load, whereas intermittent ratings (130–385 A) apply to cyclic longwall coalcutter/shearer cutting passes followed by flitting or haulage pauses.
Need BS 6708 Type 307, Type 307M or Type 307S 3.3 kV Cable?
Specify your required model (307, 307M, or 307S), cross-section (25–150 mm²), and cut drum lengths for direct TEBAOFLEX factory pricing and 7.5 kV test reports.
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