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Three Core 12/20KV Medium Voltage Unarmored Cable
Voltage: 12/20kV (Um=24kV)
Conductor: Copper or aluminum, compacted circular Class 2
Conductor Screen: Extruded semi-conductive compound (per core)
Insulation: XLPE, 5.5mm per core
Insulation Screen: Extruded semi-conductive compound + Cu tape screen
Assembly: 3 screened cores + filler + binder tape
Outer Sheath: PVC Type ST2, PE, or LSZH (BS 7835)
Product Overview
Three Core 12/20kV (Um=24kV) Medium Voltage Unarmoured Cable is the higher-voltage sibling of the widely deployed 6/10kV three-core cable. With doubled insulation thickness per core (5.5mm vs 3.4mm) it serves the 20kV distribution class — standard in Continental European municipal and industrial networks, large-scale transformer connections, and high-power MV circuits where 10kV class cables would require an unacceptably large conductor cross-section to handle the same power. Three individually screened cores are assembled with filler and binder tape into a single cable, enclosed within a PVC Type ST2 outer sheath. For a given power throughput, a 12/20kV cable carries half the current of a 6/10kV cable — dramatically reducing copper losses (I²R) and enabling longer distribution distances without voltage drop exceeding acceptable limits.
6/10kV vs 12/20kV Three Core: When to Step Up
| Property | Three Core 6/10kV | Three Core 12/20kV |
|---|---|---|
| Insulation per Core | 3.4mm | 5.5mm — 62% thicker |
| Typical OD (3×240mm²) | 68.8mm | 78.5mm — ~14% larger |
| Weight (3×240mm² Cu) | 9,342 kg/km | 10,279 kg/km — ~10% heavier |
| Current at Equivalent Power | 2× higher current | Reference — half the current loss (I²R) |
| Max Distribution Distance | ~2-3 km at typical load | ~5-8 km at equivalent load — doubles reach |
| Typical Deployment | Local distribution, transformer connections | Regional distribution, long-distance MV transmission |
Cable Construction
1. Conductor — Stranded compacted circular copper or aluminium
2. Conductor Screen — Extruded semi-conductive compound
3. Insulation — XLPE, 5.5mm, 90°C rated
4. Insulation Screen — Extruded semi-conductive compound
5. Metallic Screen — Copper tape
6. Binder Tape — Non-hygroscopic
7. Filler — Non-hygroscopic
8. Outer Sheath — PVC Type ST2 (PE or LSZH option)
Technical Characteristics
| Rated Voltage U₀/U (Um) | 12/20kV (24kV maximum system voltage) |
| Insulation Thickness | 5.5mm per core (all cross-sections) |
| Max. Conductor Temperature | 90°C (continuous), 250°C (short-circuit, max 5s) |
| Min. Bending Radius | 15 × overall diameter |
| Core Identification | Red, Yellow, Blue tape between insulation screen and metallic screen |
| Conductor Types | Copper or aluminium, stranded compacted circular Class 2 |
| Sheath Options | PVC Type ST2, PE, or LSZH (BS 7835) |
| Partial Discharge | <5 pC at 1.73U₀ (20.8kV) per IEC 60840 |
Applicable Standards
| Standard | Scope |
|---|---|
| IEC 60502-2 | International standard for extruded insulation power cables 6kV to 30kV. 12/20kV is covered under this standard. |
| GB/T 12706.2 | Chinese national standard for power cables 6kV to 35kV. Governs 12/20kV three-core cable construction and testing for Chinese markets. |
| BS 6622 | British standard for XLPE insulated cables. Covers 12/20kV three-core unarmoured configuration. |
| IEC 60840 | PD testing at 1.73U₀. Each core individually tested and certified. Core-to-core screen isolation verified. |
| BS 7835 | LSZH sheathed MV cables. Specify for indoor public building and tunnel installations. |
| IEC 60228 | Conductors — Class 2 stranded copper and aluminium, compacted circular. |
Technical Specifications — Three Core 12/20kV
XLPE insulation: 5.5mm (all cross-sections). Ampacity pre-calculated for three-core bundled configuration. Air: 30°C. Soil: 20°C, 2.5 K·m/W, 0.7m.
| Cross Section (mm²) | Conductor Dia. (mm) | Insulation (mm) | Sheath (mm) | Overall Dia. (mm) | Weight Cu (kg/km) | Weight Al (kg/km) | Ampacity Air Cu | Al (A) | Ampacity Soil Cu | Al (A) |
|---|---|---|---|---|---|---|---|---|
| 3 × 25 | 6.0 | 5.5 | 2.6 | 49.9 | 2,491 | 2,025 | 125 | 96 | 135 | 105 |
| 3 × 35 | 7.0 | 5.5 | 2.7 | 52.3 | 2,922 | 2,269 | 150 | 115 | 160 | 125 |
| 3 × 50 | 8.4 | 5.5 | 2.8 | 55.5 | 3,537 | 2,604 | 175 | 135 | 190 | 150 |
| 3 × 70 | 10.0 | 5.5 | 2.9 | 59.1 | 4,314 | 3,008 | 220 | 170 | 235 | 185 |
| 3 × 95 | 11.5 | 5.5 | 3.0 | 62.6 | 5,244 | 3,472 | 265 | 205 | 285 | 220 |
| 3 × 120 | 13.0 | 5.5 | 3.1 | 66.1 | 6,142 | 3,904 | 305 | 235 | 320 | 250 |
| 3 × 150 | 14.5 | 5.5 | 3.2 | 69.5 | 7,211 | 4,413 | 350 | 270 | 365 | 285 |
| 3 × 185 | 16.2 | 5.5 | 3.3 | 73.4 | 8,423 | 4,972 | 395 | 310 | 410 | 320 |
| 3 × 240 | 18.4 | 5.5 | 3.5 | 78.5 | 10,279 | 5,802 | 465 | 365 | 475 | 370 |
| 3 × 300 | 20.5 | 5.5 | 3.6 | 83.3 | 12,248 | 6,652 | 530 | 415 | 535 | 420 |
| 3 × 400 | 23.5 | 5.5 | 3.9 | 90.2 | 15,418 | 7,957 | 615 | 485 | 605 | 480 |
DC Conductor Resistance & Short-Circuit Withstand at 20°C
| Cross Section (mm²) | Cu (Ω/km) | Al (Ω/km) | Cu Short-Circuit 1s (kA) | Al Short-Circuit 1s (kA) |
|---|---|---|---|---|
| 25 | 0.727 | 1.20 | 3.69 | 2.42 |
| 35 | 0.524 | 0.868 | 5.15 | 3.37 |
| 50 | 0.387 | 0.641 | 7.31 | 4.79 |
| 70 | 0.268 | 0.443 | 10.2 | 6.68 |
| 95 | 0.193 | 0.320 | 13.8 | 9.03 |
| 120 | 0.153 | 0.253 | 17.4 | 11.4 |
| 150 | 0.124 | 0.206 | 21.7 | 14.2 |
| 185 | 0.0991 | 0.164 | 26.7 | 17.5 |
| 240 | 0.0754 | 0.125 | 34.6 | 22.6 |
| 300 | 0.0601 | 0.100 | 43.1 | 28.2 |
| 400 | 0.0470 | 0.0778 | 57.4 | 37.65 |
Packaging & Delivery
Heavy-Duty Wooden Drum
Reinforced fumigated wooden drums. 12/20kV three-core is ~10% heavier than 6/10kV — drum flange diameter ≥25× cable OD recommended.
Moisture Protection
Triple-layer protection: individual core sealing + overall sheath end sealing + heat-shrink caps with desiccant. UV-resistant polyethylene drum wrap for outdoor storage up to 12 months.
Documentation
Per-core PD certificates to IEC 60840, core-to-core voltage test report, DC resistance measurement, material traceability per IEC 60502-2.
Typical Applications — Three Core 12/20kV
European Municipal Distribution
12/20kV three-core is the standard urban MV distribution cable in Continental Europe. One cable from 110/20kV substation feeds a neighbourhood ring of 4-8 distribution transformers.
Long-Distance MV Transmission
20kV class doubles the reach of 10kV for equivalent conductor size. Regional distribution from primary substation to distant load centres without intermediate substations.
High-Power Transformer Connections
Dedicated 12/20kV three-core cable from MV switchgear to transformers rated 5MVA and above where single-core cable grouping would be impractical.
Solar Farm MV Collection
20kV is a common solar farm MV collection voltage in Europe. Three-core cable simplifies trenching and reduces cable management in combiner boxes.
Industrial Park MV Ring Mains
Large industrial parks where 20kV ring main distribution provides higher capacity and longer reach than 10kV. Single three-core pull per section simplifies duct installation.
EU-Funded Infrastructure
European Commission-funded energy infrastructure projects. IEC 60502-2 certification mandatory. Three-core cable reduces installation cost — a key factor in EU tender evaluation.
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Frequently Asked Questions
As a factory, we offer flexible MOQ depending on the cable type. For standard stock items, MOQ is low; for customized specifications, please contact our sales team for a detailed quote.
Yes, Qiangli cables are manufactured in compliance with international standards such as UL, CE, TUV, and VDE. We provide full test reports and certificates upon request.
Absolutely. We have a dedicated R&D team that can customize cable structure, material, color, and printing to meet your specific project needs.
For standard products, lead time is usually 7-15 days. For large-scale project orders or customized products, it typically ranges from 20 to 30 days.
Yes, we provide free samples for most standard cables. You only need to cover the international courier costs. Contact us to arrange your sample shipment.