Underground Distribution Cable 3 Core 35mm² YJV22 8.7/15kV Armored XLPE

Cable Designation & Meaning

Construction: XLPE insulated, steel-tape armoured, PVC sheathed, three-core medium-voltage power cable.

YJV22-3×35 mm² 8.7/10 kV (and 8.7/15 kV) — Cable Specification & Engineering Data 

1. Product Overview & Rating Summary. YJV22-3×35 is a medium-voltage (MV) power cable rated 8.7/10 kV (Um = 12 kV) at 50 Hz, built around three 35 mm² compacted-stranded copper conductors, each with a triple-extruded semi-conducting screen / XLPE insulation / semi-conducting screen system, a lapped copper-tape screen, and an overall double-galvanised-steel-tape armour (type 22) with a black PVC outer jacket. The same construction is also manufactured in the 8.7/15 kV grade (Um = 17.5 kV) with thicker 5.5 mm XLPE insulation. The cable is designed for 10 kV distribution feeders serving 630–1000 kVA distribution transformers and larger industrial MV loads. Finished diameter is about 58 mm (10 kV) and nominal mass about 4700 kg/km (≈ 470 kg per 100 m). With all three cores loaded, the cable carries about 150 A in free air at 25 °C (engineering estimate).

2. Layer-by-Layer Construction (Conductor to Outer Jacket).

3. Electrical Characteristics. Each 35 mm² conductor is held to a maximum DC resistance of 0.524 Ω/km at 20 °C, rising to about 0.68 Ω/km at the 90 °C operating point. Every length survives the routine 21.5 kV AC power-frequency proof held for five minutes (30.5 kV for the 15 kV grade). Partial discharge at 1.5 U0 must not exceed 20 pC. Dissipation factor tan δ ≤ 0.001 at U0. Insulation resistance ≥ 1000 MΩ·km, typical capacitance ≈ 0.36 μF/km. Impulse withstand (BIL) is 75 kV for the 10 kV grade and 95 kV for the 15 kV grade. With all three cores energised, reference loading is about 150 A in free air at 25 °C, about 145 A direct-buried.

Insulation Data

Electrical Parameters

Reference values: 35 mm² at 145 A, 3-phase 10 kV → max balanced load ≈ 2.51 MVA. Voltage drop at 145 A ≈ 9.7 V/km per core (≈0.097% per 100 m).

Temperature Characteristics

4. Thermal Response & Flame Behaviour. XLPE insulation sustains a 90 °C continuous conductor temperature, with short-circuit capability up to 250 °C for ≤ 5 s. The cable is rated for service ambients between −20 and +50 °C. PVC jacket provides flame-retardant performance per GB/T 18380.34 class A. Short-circuit rating at 250 °C for 1 s is about 5.1 kA for the 35 mm² copper conductor. Thermal resistance of reference burial soil is 1.2 K·m/W.

Fire Performance (YJV22 — Standard)

5. Installation Practice & Handling. Bends must not fall below 15 times the actual outer diameter — about 870 mm for this size. The steel armour must be earthed at both ends; the copper-tape screen must be bonded per MV practice (both ends, or cross-bonded for longer routes). MV heat-shrink or cold-shrink termination kits are mandatory — do not treat this as an LV cable. Laying temperature must not fall below 0 °C; reels must be pre-heated in cold weather. At about 470 kg per 100 m, the cable requires drum jacks and rated pulling gear.

Mechanical & Installation Parameters

6. Typical Service Applications. This YJV22-3×35 MV cable is used in 10 kV / 15 kV distribution networks serving medium-load feeders: 630–1000 kVA distribution transformer primary feeds, industrial plant 10 kV power distribution to medium-load MCCs, substation to factory main 10 kV switchboard links, 10 kV motor branch feeds for medium-voltage motors up to about 200 kW, commercial building 10 kV incoming and floor main feeders, hospital 10 kV emergency / normal switchboard inter-ties, data-centre 10 kV UPS / switchgear feeders, mining and quarry 10 kV power supply lines (armour permits mechanical abuse), direct-buried urban 10 kV secondary network feeders, and any circuit where mechanical protection against crush or impact is required. Approved installation methods include direct burial, cable tray, concrete duct, and indoor MV cable trench.

7. Testing & Quality Assurance Regime. Routine tests on every length include conductor DC resistance ≤ 0.524 Ω/km at 20 °C, the 21.5 kV AC / 5 min withstand (30.5 kV for 15 kV grade), partial discharge ≤ 20 pC at 1.5 U0, tan δ ≤ 0.001, insulation resistance ≥ 1000 MΩ·km, conductor continuity across all three cores, steel-armour and copper-screen continuity, and dimensional inspection. Sample and type tests comprise impulse withstand at ±75 kV (or ±95 kV for 15 kV), heating-cycle load-loss test, bending at 15 × OD, short-circuit to 250 °C, flame spread GB/T 18380.34 class A, and voltage re-test after thermal ageing. A factory test certificate accompanies each drum.

Cable Parameters

Cable Test Parameters

Cable Cross Section Structure

Cable Construction Description

8. Standards & Conformity. Design and production are governed by GB/T 12706.2-2020 (IEC 60502-2) for extruded-solid-insulation power cables from 1.8/3 kV to 26/35 kV. Conductors satisfy GB/T 3956 Class 2. Flame performance follows GB/T 18380.34. Surface marking complies with GB/T 6995. Cables can also be supplied to IEC 60502-2, BS 6622 or NFC 32-322 requirements on request.

9. Packaging, Storage & Logistics. Standard delivery is 500 m or 1000 m per wooden-steel drum, with bespoke cut lengths available on request. Each drum carries type, voltage, size, supplier identity, production year and sequential metre marking per GB/T 6995. Storage should be in dry, covered premises at −20 to +40 °C, shielded from direct sunlight and moisture; drum end seals must remain intact until installation. MV cable terminations and joints should be scheduled immediately after laying to avoid prolonged exposure of cut ends.

10. Procurement Specification. State "YJV22-8.7/10 kV-3×35" (or "YJV22-8.7/15 kV-3×35" for the thicker-insulation grade) together with the required length or drum arrangement. Always order the matching MV termination kits (indoor/outdoor / separable connectors) and field-joint kits at both ends. Always request the factory test certificate, which must include the partial-discharge and impulse-withstand reports, to confirm the actual diameter, weight and conductor resistances for the production batch.

11. Cable Industry FAQ.

• Q1: How does 35 mm² differ from 25 mm² in 10 kV service? 35 mm² raises the reference ampacity from about 120 A to about 150 A, and the short-circuit rating from about 3.6 kA to about 5.1 kA. It is the standard feeder for 630–1000 kVA transformers and 10 kV motors up to about 200 kW, whereas 25 mm² serves 315–500 kVA transformers and smaller motor branches.
• Q2: What does the "22" in YJV22 mean? The first "2" = double-steel-tape armour; the second "2" = PVC outer sheath. YJV22 is therefore a Cu conductor / XLPE insulation / double-steel-tape armour / PVC jacket MV cable. Without the "22" suffix, YJV would be unarmoured.
• Q3: When do I choose 8.7/10 kV vs 8.7/15 kV? Choose 8.7/10 kV for nominal 10 kV distribution networks (Um = 12 kV). Choose 8.7/15 kV for nominal 15 kV networks (Um = 17.5 kV) or where the system may be up-rated — the thicker 5.5 mm XLPE gives a larger safety margin.
• Q4: Why is there no separate neutral core? At MV distribution voltages, three-phase currents are balanced and the system is typically solidly or resistance-earthed; the copper-tape screen provides the earth path. A separate neutral is not required in standard 3-core MV construction.
• Q5: Why is the triple-extrusion process important? Conductor screen, XLPE insulation and insulation screen are co-extruded in one pass to avoid air gaps and contamination at the interfaces. Even tiny voids cause partial discharge at MV voltages and lead to early insulation failure.
• Q6: Why is there a copper-tape screen? The copper tape (0.1 × 25 mm lapped) provides an equipotential outer surface around each core, equalises the electric field, and carries capacitive and fault currents to earth.
• Q7: Can this cable be directly buried? Yes — the double-steel-tape armour provides crush protection, and the PVC jacket is moisture-resistant. Direct burial depth and covering must follow the local MV cable installation code.
• Q8: What is partial discharge and why is it tested? Partial discharge (PD) is tiny electrical sparks inside the insulation caused by voids or contaminants. At 1.5 U0, PD must be ≤ 20 pC. High PD values predict early insulation failure and are the most sensitive factory-quality indicator.
• Q9: Why is the routine test 21.5 kV and not 10 kV? Routine tests apply a power-frequency withstand voltage higher than the rated voltage (typically 2.5 U0 = 21.75 kV, rounded to 21.5 kV) to catch manufacturing defects before site installation.
• Q10: Can the steel armour be used as the earth? The steel armour provides mechanical protection but is not sized or certified as the primary fault-current earth conductor. The copper-tape screen and dedicated earthing conductors carry fault currents; the armour must be bonded to earth for safety.
• Q11: What service life can be expected? When installed, terminated and operated within the stated temperature, voltage and current ratings, XLPE-insulated MV cables are designed for a service life of around 30 years in fixed installation. The dominant failure mode is moisture or PD at terminations, so professional jointing is critical.