MEDIUM VOLTAGE · 26 / 35 kV · GB/T 12706.3
35 kV XLPE Cable
Highest MV class before HV substation — generator outlet connections and utility inter-ties. Three-core or single-core construction, copper or aluminium conductor, manufactured against GB/T 12706.3 with project-specific screen sizing, armour and sheath.
§01 — Cable construction
The reference construction, layer by layer.
26/35 kV is built under GB/T 12706.3 with a 10.5 mm XLPE wall — the top of the MV range before HV classes begin. Screen sizing, drum test records and marking follow generator-duty expectations: every drum leaves the factory with its full routine test report, including the 91 kV / 5 min withstand and the PD record at 45 kV.
| # | Layer | Reference detail |
|---|---|---|
| 01 | Conductor | Cu class 2 stranded (RM). Sector-shaped (SM) for 3-core ≥ 185 mm². |
| 02 | Conductor screen | Extruded semiconducting compound, ≤ 0.5 mm nominal thickness. |
| 03 | XLPE insulation | Extruded XLPE, 10.5 mm nominal at 26/35 kV per GB/T 12706.3, table 6 (50–1 600 mm²). |
| 04 | Insulation screen | Extruded semiconducting, strippable or bonded per requirement. |
| 05 | Metallic screen | Cu wire screen per GB/T 12706.3, sized against the generator or grid earth-fault duty stated in the cable schedule. |
| 06 | Inner sheath | PVC ST2, extruded bedding. |
| 07 | Armour | Double steel tape (STA) for direct burial; SWA for higher tensile load; AWA for single-core. |
| 08 | Serving | Anti-corrosion wrap on certain designs (optional). |
| 09 | Outer sheath | PVC ST2 black; PE or LSZH on request. |
§02 — Technical specifications
Electrical parameters — 26 / 35 kV class.
| Conductor (mm² Cu) | Insulation thickness | DC resistance @20 °C (Ω/km) | Indicative current, direct burial 25 °C (A) |
|---|---|---|---|
| 3 × 35 | 10.5 mm | 0.524 | ~170 |
| 3 × 50 | 10.5 mm | 0.387 | ~205 |
| 3 × 70 | 10.5 mm | 0.268 | ~250 |
| 3 × 95 | 10.5 mm | 0.193 | ~300 |
| 3 × 120 | 10.5 mm | 0.153 | ~345 |
| 3 × 150 | 10.5 mm | 0.124 | ~385 |
| 3 × 185 | 10.5 mm | 0.0991 | ~435 |
| 3 × 240 | 10.5 mm | 0.0754 | ~500 |
| 3 × 300 | 10.5 mm | 0.0601 | ~560 |
| 3 × 400 | 10.5 mm | 0.0470 | ~640 |
DC resistance values per IEC 60228. Indicative current: ground 25 °C, soil thermal resistivity 1.5 K·m/W, depth 1.0 m, flat formation — reference only; final ampacity is calculated against your installation conditions. Overall diameter and weight for this voltage class are issued in the project datasheet with the formal offer.
§02B — Worked example · 26 / 35 kV
What the 35 kV test numbers mean on the drum card.
Routine voltage test AC 91 kV / 5 min = 3.5 · U₀ applied to every drum; partial discharge ≤ 10 pC at 45 kV = 1.73 · U₀; impulse type test 250 kV per GB/T 12706.3. These three numbers are the acceptance basis most generator and utility specifiers ask for — quote them back to us with your project and we return the matching routine test report layout with the offer.
§03 — Standards
Standards printed on the sheath and on the drum card.
§04 — Applications
Where 35 kV cable from Lulian is in service.
Generator outlet connection
26/35 kV cable from generator step-up transformer to the plant switchyard at hydro and thermal plants.
Generator step-up connections →35 kV utility inter-ties
Short interconnection feeders between adjacent 35 kV substations.
Medium voltage cable range →Large renewable plant export
35 kV export feeders from large solar / wind plants to the grid connection point.
Renewable export cable specification →Not sure which voltage class your network needs? See all cable applications and sector solutions, or send the system voltage and the earthing method — we confirm the class and the construction in the offer.
§05 — Quality testing
What we test on every drum.
Routine tests run on every drum; sample tests on each batch; type tests on new constructions witnessed by CNAS-accredited third-party labs.
- Conductor DC resistance at 20 °C (routine)
- AC voltage withstand AC 91 kV / 5 min (routine)
- Partial discharge ≤ 10 pC at 45 kV (1.73 U₀) (sample)
- Insulation thickness & eccentricity (sample)
- Metallic screen cross-section (routine)
- Armour coverage & bedding integrity (routine)
- Sheath thickness + spark test (routine)
- Bending test + voltage after bending (type)
- Impulse voltage 250 kV (type)
§06 — Packaging & delivery
Drums sized for the cable, not for the workshop.
35 kV drums include the full routine test report — the 91 kV / 5 min withstand and the PD record at 45 kV — as required for generator-duty acceptance. Wooden drums with fumigation marks for export; steel-plywood drums for heavy cross-sections. Cable ends sealed with heat-shrink caps; shipping marks per the buyer’s format.
Standard drum lengths: 500 / 1000 / 1500 / 2000 m. Lead time: 25–35 working days for stocked constructions; 40–55 working days for project-specific builds.
§07 — FAQ
Common questions on 35 kV cable procurement.
What is the U₀/U rating of 35 kV XLPE cable?
26 / 35 kV, Uₘ = 40.5 kV per GB/T 12706.3 — this class sits above the IEC 60502-2 range, which ends at Uₘ 36 kV. It is the standard class for 35 kV utility and generator-duty circuits.
What conductor cross-sections are available?
Three-core: 25–400 mm². Single-core: 25–630 mm². Copper or aluminium, class 2 stranded; sector-shaped conductors for large 3-core sizes.
Can the cable be direct-buried?
Yes. The armoured construction (STA) with PVC ST2 outer sheath is rated for direct burial. SWA is recommended where tensile load or rodent risk is high.
What is the partial discharge limit?
≤ 10 pC measured at 45 kV (1.73 U₀) per IEC 60502-2. PD is measured on every drum and documented on the routine test report.
What routine and type tests are performed?
Routine on every drum: conductor DC resistance, AC voltage withstand AC 91 kV / 5 min, sheath spark test. Sample: PD, insulation thickness, screen check. Type: bending + voltage, load cycle, impulse voltage 250 kV.
Can the cable be supplied with LSZH sheath?
Yes, for tunnel, metro, data centre and indoor substation use. Verified against IEC 61034 (smoke density) and IEC 60754 (acid gas).
Why does the 35 kV drum test at 91 kV?
The routine test applies 3.5 · U₀ = 3.5 × 26 kV = 91 kV for 5 minutes to every drum per GB/T 12706.3. It is a deliberate over-voltage that proves the insulation wall and screen system with margin; the PD limit of 10 pC at 45 kV (1.73 U₀) is measured on the same drums.
Send the cable schedule. We confirm the construction in 24 hours.
Share voltage class, conductor material & size, core count, armour, sheath, installation method, total length and drum preference.
§08 — Related
Other voltage classes & adjacent products.
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