IEC Standard XLPE Insulated Low-Smoke Zero-Halogen Flame Retardant and Fire-Resistant Low Voltage Power Cable

Applicable International Standards (IEC Standard System)
This product is designed, manufactured, and tested in accordance with the following IEC standard system:

1. Basic Construction Standard
IEC 60502-1:2021 – Power cables with extruded insulation and their accessories for rated voltages from 1 kV up to 30 kV – Part 1: Cables for rated voltages of 1 kV and 3 kThis standard specifies the construction, dimensions, and test requirements for extruded solid dielectric power cables, applicable to fixed-installed power cables for AC rated voltages of 1 kV (Um = 1.2 kV) and 3 kV (Um = 3.6 kV), such as distribution networks or industrial installations. Cables rated at 1 kV designed and tested according to this standard may also be used in DC distribution systems (DC nominal voltage ≤ 750 V or ≤ 1500 V) upon manufacturer's declaration.

2. Flame Retardant Standard
IEC 60332-3 series – Vertical flame test for bunched cables, used to evaluate the ability of bunched cables to inhibit flame spread under vertical installation conditions. Different flame retardant classes are defined according to the total volume of non-metallic material, such as Category A (7 L/m), Category B (3.5 L/m), and Category C (1.5 L/m). This product meets Category B or higher flame retardant performance.

3. Halogen-Free (Low Corrosivity) Standards
IEC 60754-1 – Determination of halogen acid gas content. Specifies that the hydrogen chloride (HCl) release during combustion of cable materials shall not exceed 5 mg/g to be designated as halogen-free cable.
IEC 60754-2 – Determination of acidity and conductivity of gases evolved during combustion. Assesses corrosivity by measuring the pH and conductivity of an aqueous solution; for halogen-free cable materials, the pH shall be ≥ 4.3 and the conductivity shall be ≤ 10 μS/mm.

4. Low Smoke Standard
IEC 61034-1 / IEC 61034-2 – Measurement of smoke density. Measures light transmittance in a 3 m³ test chamber; low-smoke cables shall have a light transmittance of ≥ 60%. A higher transmittance indicates less smoke released during combustion of the material.

5. Fire Resistance (Circuit Integrity) Standard
IEC 60331-21 – Test for circuit integrity under fire conditions for cables with rated voltage up to and including 0.6/1 kSpecifies a flame temperature of not less than 750 °C and a recommended fire exposure time of 90 min. During the test, the rated voltage is applied to the specimen, and after the fire exposure period, the voltage is maintained for an additional 15 minutes. If the circuit remains intact, the fire resistance test is passed.

Product Structure
The product adopts a multi-layer composite structure design, where each layer cooperates to ensure reliable cable operation under extreme conditions such as fire. The following description takes the typical copper conductor XLPE insulated low-smoke zero-halogen flame retardant and fire-resistant power cable (e.g., type WDZN-YJY) as an example:

1. Conductor: High-purity oxygen-free copper or aluminium (aluminium conductor corresponds to type WDZN-YJLY), complying with IEC 60228. The conductor construction may be Class 1 solid conductor or Class 2 stranded conductor.
2. Insulation: Cross-linked polyethylene (XLPE) with outstanding electrical insulation properties and heat resistance. Maximum conductor operating temperature is 90 °C, with a maximum permissible short-circuit temperature of 250 °C (max. 5 seconds).
3. Insulation screen (optional): A semi-conductive screen may be applied to uniform the electric field distribution.
4. Inner covering / fillers: Low-smoke zero-halogen flame retardant filling materials are used to ensure cable roundness while enhancing flame retardant performance.
5. Armour layer (optional): Steel tape armour (indicated by suffix "22" in the type designation) or copper wire braided armour.
6. Outer sheath: Low-smoke zero-halogen polyolefin (LSOH/LSZH) material. This is the key layer that provides low-smoke, halogen-free, and flame retardant characteristics; it does not release toxic halide gases during combustion, produces very low smoke density, and maintains high visibility.

Product Type and Designation Rules
Common type examples are as follows:

- WDZN-YJY: Copper conductor, XLPE insulated, low-smoke zero-halogen polyolefin sheathed, flame retardant and fire-resistant power cable.
- WDZN-YJY22: Steel tape armoured, copper conductor, XLPE insulated, low-smoke zero-halogen polyolefin sheathed, flame retardant and fire-resistant power cable.
- WDZN-YJLY: Aluminium conductor, XLPE insulated, low-smoke zero-halogen polyolefin sheathed, flame retardant and fire-resistant power cable.

Meaning of each letter in the type designation:
- W – Halogen-free
- D – Low smoke
- Z – Flame retardant
- N – Fire-resistant
- YJ – Cross-linked polyethylene insulation (XLPE)
- Y – Polyolefin sheath
- 22 – Steel tape armour
- L – Aluminium conductor

Main Technical Parameters

1. Rated Voltage
0.6/1 kV
U₀ / U meaning: U₀ is the rated power-frequency voltage between conductor and earth (metallic screen), U is the rated power-frequency voltage between conductors.

2. Operating Temperature
- Maximum continuous conductor operating temperature: 90 °C
- Maximum permissible conductor temperature during short circuit (max. 5 s): 250 °C
- Installation temperature: not lower than -5 °C

3. Bending Radius
- Non-armoured cable: ≥ 6 × cable overall diameter
- Armoured cable: ≥ 12 × cable overall diameter

4. Fire Resistance Performance
- Flame temperature: not less than 750 °C
- Fire resistance duration: maintains circuit integrity for 90 minutes or more

5. Flame Retardant Class
- Category B or higher (classified according to IEC 60332-3 series)

6. Halogen-Free Indicators
- Halogen acid gas release: ≤ 5 mg/g (meets IEC 60754-1)
- pH value: ≥ 4.3 (meets IEC 60754-2)
- Conductivity: ≤ 10 μS/mm (meets IEC 60754-2)

7. Low Smoke Indicator
- Light transmittance: ≥ 60% (meets IEC 61034-1)

8. Reference Current-Carrying Capacity for Selected Cross-Sections
Example for WDZN-YJLY (aluminium conductor) cable (3+2 cores, installed in air at 25 °C):

Conductor cross-section 4 mm²: In air 37 A, In soil 25 A
Conductor cross-section 10 mm²: In air 65 A, In soil 44 A
Conductor cross-section 16 mm²: In air 85 A, In soil 57 A
Conductor cross-section 25 mm²: In air 115 A, In soil 77 A
Conductor cross-section 35 mm²: In air 140 A, In soil 94 A
Conductor cross-section 70 mm²: In air 215 A, In soil 144 A
Conductor cross-section 120 mm²: In air 300 A, In soil 201 A
Conductor cross-section 240 mm²: In air 465 A, In soil 312 A

Note: The current-carrying capacity of copper conductor cables is approximately 1.3 times that of aluminium conductors.

Key Performance Characteristics

1. Halogen-Free and Environmentally Friendly
No toxic halide gases (such as hydrogen chloride, HCl) are released during combustion, preventing secondary harm to personnel and equipment, and environmentally benign. Meets the requirements of IEC 60754-1 and IEC 60754-2.

2. Low Smoke Property
Smoke concentration generated is very low, with light transmittance ≥ 60%. High visibility is maintained during a fire, facilitating personnel evacuation and fire rescue.

3. Flame Retardant Performance
Passes the bunched cable flame test of IEC 60332-3, effectively inhibiting flame spread and slowing fire development, achieving Category B or higher flame retardant rating.

4. Fire Resistance Performance
Incorporates a special fire-resistant layer structure. Circuit integrity can be maintained for over 90 minutes in a flame at 750 °C, meeting the requirements of IEC 60331-21, ensuring continuous power supply to critical equipment under fire conditions.

5. Sound Electrical Performance
Cross-linked polyethylene insulation offers high temperature resistance, high insulation resistance, and low dielectric loss, with stable and reliable electrical performance.

Application Areas
This cable is widely applicable to the following locations:

- High-rise buildings: Residential, office buildings, shopping malls and other densely populated places.
- Underground transportation facilities: Subways, tunnels, underground car parks and other enclosed spaces.
- Transportation hubs: Airports, railway stations, bus terminals and other important transportation facilities.
- Medical facilities: Hospitals, emergency centres and other life-support establishments.
- Educational institutions: Schools, libraries, museums, etc.
- Large public buildings: Exhibition centres, sports venues, shopping centres, etc.
- Industrial facilities: Power stations, chemical plants and other industrial sites with high safety requirements.

Typical Structure Diagram
Taking WDZN-YJY22 (steel tape armoured) as an example, the layers from inside to outside are:

1. Copper conductor core
2. Cross-linked polyethylene insulation (XLPE)
3. Low-smoke zero-halogen flame retardant filling and binding tape
4. Low-smoke zero-halogen flame retardant polyolefin inner sheath
5. Steel tape armour layer
6. Low-smoke zero-halogen flame retardant polyolefin outer sheath