Factory-Direct Supply of Certified Wires and Conductors for Diverse Industrial Applications
Three Core 18/30KV Medium Voltage Unarmored Cable
Voltage: 18/30kV (Um=36kV)
Conductor: Copper or aluminum, compacted circular Class 2
Conductor Screen: Extruded semi-conductive compound (per core)
Insulation: XLPE, 8.0mm per core
Insulation Screen: Extruded semi-conductive compound + Cu tape/concentric wire screen
Assembly: 3 screened cores + filler + binder tape
Outer Sheath: PVC Type ST2, PE, or LSZH (BS 7835)
Product Overview
Three Core 18/30kV (Um=36kV) Medium Voltage Unarmoured Cable is a sub-transmission-class three-core XLPE-insulated power cable. At 18/30kV with 8.0mm insulation per core, this cable sits at the interface between medium voltage and high voltage — carrying the highest power density of any three-core unarmoured cable in the IEC 60502-2 framework. It connects 132/30kV or 110/30kV primary substations to downstream 30/10kV or 30/0.4kV secondary substation transformers, and serves as the backbone inter-substation cable in 30kV-class utility networks. The three individually screened cores are assembled with non-hygroscopic filler and binder tape, enclosed in a PVC Type ST2 outer sheath. At 90.0-101.8mm overall diameter, this is the largest three-core unarmoured cable in the standard product range — handled exclusively with mechanical pulling equipment and heavy-duty cable drums.
18/30kV: Where Three-Core MV Peaks
Three Core MV Cable Voltage Progression
| Voltage Class | Insulation/Core | Typical OD (3×240mm²) | Typical Application |
|---|---|---|---|
| 6/10kV | 3.4mm | 68.8mm | Local distribution, transformer connections |
| 12/20kV | 5.5mm | 78.5mm | Regional distribution, European municipal networks |
| 18/30kV | 8.0mm | 90.0mm | Sub-transmission, primary substation interconnection |
Cable Construction
1. Conductor — Stranded compacted circular copper or aluminium
2. Conductor Screen — Extruded semi-conductive compound
3. Insulation — XLPE, 8.0mm, 90°C rated
4. Insulation Screen — Extruded semi-conductive compound
5. Metallic Screen — Copper tape or concentric copper wires
6. Binder Tape — Non-hygroscopic
7. Filler — Non-hygroscopic
8. Outer Sheath — PVC Type ST2 (PE or LSZH)
Technical Characteristics
| Rated Voltage U₀/U (Um) | 18/30kV (36kV maximum system voltage) |
| Insulation Thickness | 8.0mm 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 |
| Metallic Screen Options | Copper tape (standard) or concentric layer of copper wires |
| Sheath Options | PVC Type ST2, PE, or LSZH (BS 7835) |
| Partial Discharge | <5 pC at 1.73U₀ (31.1kV) per IEC 60840 |
Applicable Standards
| Standard | Scope |
|---|---|
| IEC 60502-2 | International standard for extruded cables 6kV-30kV. 18/30kV is the highest voltage covered under this standard. |
| GB/T 12706.2 | Chinese national standard for power cables 6kV to 35kV. Governs 18/30kV three-core cable for Chinese projects. |
| BS 6622 | British standard for XLPE insulated cables 3.8/6.6kV to 19/33kV. 18/30kV three-core covered under Part 1. |
| IEC 60840 | PD testing methodology for cables up to 150kV. Factory PD test at 31.1kV per core — the highest test voltage in the MV range. |
| BS 7835 | LSZH sheathed MV cables. Important for 18/30kV cables in indoor substations where fire safety is critical at this power level. |
| IEC 60228 | Conductors — Class 2 stranded copper and aluminium, compacted circular. |
Technical Specifications — Three Core 18/30kV
XLPE insulation: 8.0mm (all cross-sections). Metallic screen: copper tape (standard) or concentric copper wire layer (specify at order). Ampacity: 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 | 8.0 | 3.0 | 61.5 | 3,650 | 3,184 | 125 | 98 | 135 | 105 |
| 3 × 35 | 7.0 | 8.0 | 3.0 | 63.8 | 4,153 | 3,500 | 150 | 115 | 160 | 125 |
| 3 × 50 | 8.4 | 8.0 | 3.1 | 67.0 | 4,836 | 3,903 | 180 | 140 | 190 | 145 |
| 3 × 70 | 10.0 | 8.0 | 3.2 | 70.7 | 5,671 | 4,365 | 220 | 170 | 230 | 180 |
| 3 × 95 | 11.5 | 8.0 | 3.4 | 74.1 | 6,657 | 4,885 | 265 | 205 | 275 | 215 |
| 3 × 120 | 13.0 | 8.0 | 3.5 | 77.6 | 7,645 | 5,406 | 305 | 235 | 315 | 245 |
| 3 × 150 | 14.5 | 8.0 | 3.6 | 81.0 | 8,773 | 5,975 | 345 | 270 | 355 | 275 |
| 3 × 185 | 16.2 | 8.0 | 3.7 | 84.9 | 10,070 | 6,619 | 390 | 305 | 400 | 310 |
| 3 × 240 | 18.4 | 8.0 | 3.9 | 90.0 | 12,003 | 7,526 | 455 | 355 | 460 | 360 |
| 3 × 300 | 20.5 | 8.0 | 4.0 | 94.8 | 14,060 | 8,464 | 525 | 410 | 520 | 410 |
| 3 × 400 | 23.5 | 8.0 | 4.2 | 101.8 | 17,365 | 9,903 | 600 | 470 | 590 | 465 |
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 Iron-Reinforced Drum
Massive reinforced wooden or steel drums. Single drum of 3×400mm² Cu can weigh 17+ tonnes — crane offloading required at both factory and site.
Triple-Layer Moisture Protection
Per-core heat-shrink sealing + overall sheath end sealing + dual-layer heat-shrink caps with desiccant. UV-resistant drum wrap for outdoor storage.
Comprehensive Documentation
Per-core PD certificate (31.1kV test), core-to-core voltage test, DC resistance, partial discharge fingerprint, material traceability, drum loading certificate.
Typical Applications — Three Core 18/30kV
Primary Substation Interconnection
18/30kV three-core cables connecting 132/30kV or 110/30kV primary substations to secondary 30/10kV substations. The standard inter-substation cable in 30kV utility networks.
Heavy Industry Private MV Networks
Steel mills, aluminium smelters, and petrochemical complexes operating 30kV private distribution networks. Three-core cable handles motor and transformer loads at the highest MV density.
Offshore Platform Power Supply
30kV submarine-to-onshore or platform-to-platform power cables. 18/30kV three-core simplifies the transition from subsea to topside cable routing.
Railway Traction Power
30kV three-core cables for railway traction substation interconnectors in 25kV AC and 30kV DC electrified railway systems.
Chinese Utility Projects
GB/T 12706.2 certified. 18/30kV is a common Chinese primary distribution voltage for industrial parks and urban utility networks.
Large Solar Farm Grid Connection
500MW+ solar farms aggregating at 30kV for grid connection. Three-core cable handles the high power concentration at the point of interconnection.
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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.