High-performance, long-life wire

HIGH PERFORMANCE LONG-LIFE WIRE

1 Product Standard:

Ministry of Housing and Urban–Rural Development Industry Standard JG/T 441-2014 “Double-Layer Co-Extruded Insulated Radiation‑Crosslinked Halogen‑Free Low‑Smoke Flame‑Retardant Cables with Rated Voltage of 450/750 V and Below”

2 Scope of Use:

This product is suitable for applications with high flame‑retardant requirements, such as subways, high‑rise buildings, shopping malls, theaters, power stations, chemical plants, urban plazas, and other public‑utility facilities, where the rated AC voltage does not exceed 450/750 V. The cable’s halogen‑free, low‑smoke characteristics ensure slow flame spread, low smoke density, excellent visibility, and minimal release of harmful gases, facilitating safe evacuation. Its combustion gases are less corrosive, thereby protecting electrical equipment. Moreover, the halogen‑free formulation significantly enhances the cable material’s resistance to aging, ultraviolet radiation, and other forms of irradiation, extending its service life to typically over 70 years.

3 Usage Characteristics:

3.1 Rated voltage of the cable: UO/U = 450/750 V. 3.2 The maximum permissible long-term operating temperature of the cable is 90°C or higher. The ambient temperature during installation shall not be lower than 0°C. 3.3 Recommended bending radius: For cables with an outer diameter of 25 mm or less, the bending radius shall be no less than 4 times the outer diameter; for cables with an outer diameter greater than 25 mm, the bending radius shall be no less than 6 times the outer diameter. 3.4 Service life: ≥ 70 years.

4 Model Specifications:

5 Cable Structure Diagram:

In the figure: 1 denotes the conductor; 2 denotes the long-life internal insulation; and 3 denotes the long-life external insulation.

6 Cable Technical Parameters and Performance Requirements:

6.1 Cable Structure

In addition to complying with the provisions of JG/T 441-2014, the cable structure shall also meet the following requirements.

6.1.1 Conductor

The conductor surface shall be smooth, free of oil and grease, and free of burrs or sharp edges on the shielding and insulation, as well as any protrusions or broken strands. The conductor shall be round; otherwise, it shall comply with the requirements for Class 1 conductors (nominal cross-sectional area less than 10 mm²) or Class 2 conductors (nominal cross-sectional area equal to or greater than 10 mm²) as specified in GB/T 3956.

6.1.2 Fire-resistant Layer

Flame-retardant and fire-resistant materials shall be wrapped around the conductor with two layers of mica tape, each layer having a thickness of 0.14 mm.

6.1.3 Insulation

The insulation shall be a long‑life, cross‑linked, halogen‑free, low‑smoke, flame‑retardant polyolefin, extruded in a double‑layer co‑extrusion over the conductor. The insulation must be tightly extruded onto the conductor; during insulation stripping, neither the insulation nor the conductor, nor the tinning layer (if present), shall be damaged. Compliance shall be verified by inspection and manual measurement. The average insulation thickness shall not be less than the nominal value, and the minimum measured thickness at any point shall not be less than 90% of the nominal value tn minus 0.1 mm.

6.2 Cable Roundness Deviation

The eccentricity of any cross-section shall not exceed 10%. The insulation eccentricity of the cable shall comply with the following formula: $$(\text{tmax} - \text{tmin}) / \text{tmax} \le 10\%$$ where: tmax — maximum insulation thickness, in mm; tmin — minimum insulation thickness, in mm; tn — nominal insulation thickness, in mm. tmax and tmin are measured on the same cross-section of the insulation.

6.3 Flame-retardant and fire-resistant requirements for cables

When using flame-retardant and fire-resistant cables, their flame-retardant and fire-resistant characteristics and technical specifications must comply with the fire‑resistance test requirements stipulated in IEC 60332‑21 and GB/T 12666.21.

7 Requirements:

7.1 Structural Dimensions

7.1.1 Conductor Structure

The number of conductor strands and the maximum diameter of an individual strand shall comply with the requirements specified in Tables 1, 2, and 3 of GB/T 3956-2008; the outer diameter of the conductor shall conform to the provisions set forth in Tables C.1 and C.2 of GB/T 3956-2008.

7.1.2 Insulation Thickness and Outer Diameter Dimensions

The average total thickness of the insulation shall not be less than the nominal value, and the minimum thickness at any point shall not be less than 90% of the nominal value minus 0.01 mm.

7.2 DC Resistance of Conductors at 20°C

At 20°C, the maximum DC resistance of the conductor shall comply with the requirements specified in Tables 1, 2, and 3 of GB/T 3956-2008.

7.3 Insulation Resistance at Maximum Temperature

The insulation resistance at the conductor’s maximum operating temperature shall comply with the requirements specified in Table 2 of JG/T 441-2014.

7.4 Water-Immersion Voltage-Resistance Performance

The dielectric withstand voltage performance of wires is specified in Table 3 of JG/T 441-2014.

Table 3: Dielectric Strength of Wire After Water Immersion

7.5 Insulation Mechanical Properties Before and After Aging

7.5.1 Mechanical Properties Before Aging: The minimum tensile strength shall be 9.0 N/mm², and the minimum elongation at break shall be 150%. 7.5.2 Mechanical Properties After Aging: The rate of change in tensile strength shall not exceed ±30%, and the rate of change in elongation at break shall not exceed ±30%.

7.6 Thermal Elongation Performance: The elongation under insulation load shall not exceed 80%, and the permanent elongation after cooling shall not exceed 15%.

7.7 Insulation Water Absorption Performance: The increase in insulation weight shall not exceed 5 mg/cm².

7.8 Insulation Heat-Shrinkage Performance: The maximum heat-shrinkage rate of the insulation shall not exceed 4%.

7.9 Low-Temperature Performance 7.9.1 Low-Temperature Tensile Properties The elongation at break of the insulation shall be not less than 20%. 7.9.2 Low-Temperature Wrapping Performance The insulation shall remain free of cracks.

7.10 Combustion Performance 7.10.1 Vertical Flame‑Retardant Performance of Single Wires and Bundled Cables The vertical flame‑retardant performance of single wires and bundled cables shall comply with the requirements specified in Clause 5.1 of GB/T 19666‑2005. 7.10.2 Smoke Density For Class‑1 flame‑retardant wires and Class‑1 fire‑resistant wires, the minimum light transmittance of the smoke generated during combustion shall be no less than 80%; for all other types of wires, the minimum light transmittance of the smoke produced during combustion shall be no less than 60%. 7.10.3 Acidity of Combustion Gases The pH value of the combustion gases derived from wire materials shall be no less than 4.3; the electrical conductivity shall not exceed 10 mS/mm; the bromine and chlorine content (expressed as HCl) shall not exceed 5 mg/g; and the fluorine content shall not exceed 1 mg/g. 7.10.4 Fire‑Resistance Characteristics These characteristics shall comply with the provisions of Clause 5.2 of GB/T 19666‑2005; the required fire‑exposure temperature is specified in Table 4 of JG/T 441‑2014.

Table 4 Fire-Exposure Temperature Requirements

7.11 Toxicity Index: The toxicity index of the wire insulation material shall not exceed 5.

7.12 Service Life: Under an average operating temperature of 70°C, the service life of the wire shall be no less than 70 years.

7.13 For the calculation of circuit ampacity, refer to Appendix B of JG/T 441-2014; reference values for wire ampacity are provided in Table 5 of JG/T 441-2014 (note: ambient temperature is 30°C).

7.14 Marking Clarity and Abrasion Resistance: All markings on the wire surface shall be clearly legible, and printed markings shall be resistant to abrasion.

High-performance, long-life cable

HIGH PERFORMANCE LONG-LIFE CABLE

1 Product Standard:

The Ministry of Housing and Urban–Rural Development’s industry standard JG/T 442-2014, “Double‑Layer Co‑Extruded Insulated Radiation‑Crosslinked Halogen‑Free Low‑Smoke Flame‑Retardant Power Cables with a Rated Voltage of 0.6/1 kV,” stipulates that the flame‑retardant and fire‑resistant performance shall comply with GB/T 19666-2005, “General Requirements for Flame‑Retardant and Fire‑Resistant Wires and Cables,” and GB 12666.6, “Methods for Testing the Burning Characteristics of Wires and Cables.”

2 Scope of Application:

This product is suitable for transmission and distribution lines in AC systems with a rated voltage of U0/U up to 0.6/1 kV. Thanks to the use of special materials and advanced manufacturing techniques, the cable’s service life can exceed 70 years.

3 Usage Characteristics:

3.1 Cable rated voltage U0/U: 0.6/1 kV. 3.2 The cable’s maximum permissible long-term operating temperature is 90°C and above. 3.3 The ambient temperature during cable installation shall not be lower than 0°C. 3.4 Recommended bending radius: for single-core cables, the bending radius shall be no less than 15 times the cable’s outer diameter; for multi-core cables, the bending radius shall be no less than 12 times the cable’s outer diameter. 3.5 High current-carrying capacity; installation is not limited by elevation differences. 3.6 Service life: ≥70 years.

4 Production Scope:

5 Product Structure:

In the figure: 1 is the conductor; 2 is the long‑life inner insulation; 3 is the long‑life outer insulation; 4 is the filler; 5 is the cable‑laying wrap; and 6 is the long‑life flame‑retardant jacket.

6 Technical Parameters:

6.1 Cable Structure

In addition to complying with the provisions of JG/T 442-2014, the cable structure shall also meet the following requirements.

6.1.1 Conductor

The conductor surface shall be smooth, free of oil and grease, and devoid of burrs or sharp edges on the shielding and insulation, as well as any protrusions or broken strands. The conductor shall be round and compacted by stranding, with a compaction factor of not less than 0.9; other requirements shall comply with GB/T 3956.

6.1.2 Insulation

The insulation is produced by double‑layer co‑extrusion using a long‑life, cross‑linked, halogen‑free, low‑smoke, flame‑retardant polyolefin compound, followed by irradiation. The average insulation thickness shall not be less than the nominal value, and the minimum measured thickness at any point shall not be less than 90% of the nominal thickness tn minus 0.1 mm.

6.1.3 Lining Layer and Filling

The inner lining may be extruded or wrapped. For round insulated‑core cables, a wrapped inner lining is permitted only when the gaps between the insulated cores are tightly filled; prior to extrusion of the inner lining, the cable may be secured with an appropriate tape. The nominal thickness of the extruded inner lining shall comply with the relevant standards. When waterproofing is required, a PE inner lining is recommended. Fillers made of non‑hygroscopic materials compatible with the cable’s operating temperature shall be compact and uniformly rounded, ensuring that they do not become powdery after the additional aging test on the finished cable section. After multi‑core cabling, the cable’s outer profile shall remain round and well‑defined.

6.1.4 Outer Sheath

The outer jacket shall be extruded from a long‑life, cross‑linked, halogen‑free, low‑smoke, flame‑retardant polyolefin compound and subsequently irradiated. When special requirements apply, chemical additives may be used, provided that such additives do not contain substances harmful to human health or the environment. The average jacket thickness shall not be less than the nominal value; for non‑armored cables, the minimum thickness at any point shall not be less than 85% of the nominal value minus 0.1 mm. For armored cables, the minimum thickness at any point shall not be less than 80% of the nominal value minus 0.2 mm. The outer jacket is typically black or red, but other colors may be employed by mutual agreement between the manufacturer and the purchaser to suit the specific service conditions of the cable. The outer jacket shall pass the spark‑testing specified in GB/T 3048.10, “Methods for Electrical Performance Testing of Power Cables—Part 10: Spark Test for Extruded Jackets.” Flame‑retardant and fire‑resistant cables shall use flame‑retardant jacket compounds.

Sheath thickness TS = 0.035D + 1.0

D — Nominal cable diameter before the sheath is extruded, in mm.

6.1.5 Cable Out-of-Circle Deviation

The cable’s out-of-roundness shall not exceed 10%. The formula for calculating cable out-of-roundness is: $$\text{Cable Out-of-Roundness} = \frac{\text{Maximum Cable Outer Diameter} - \text{Minimum Cable Outer Diameter}}{\text{Maximum Cable Outer Diameter}} \times 100\%$$

6.1.6 Cable Flame-Retardant Requirements

When flame-retardant cables are used, their flame-retardant properties and technical specifications shall comply with the relevant provisions of GB/T 19666.

6.2 Seals and Pull Heads

Both ends of the cable shall be sealed with waterproof sealing sleeves, with an overlap length between the sleeve and the cable of not less than 200 mm. If a pulling head is required, it shall be connected to the conductor core by crimping and reliably sealed to the cable, ensuring that the cable seal remains intact during transportation, storage, and installation.

6.3 Requirements

Table 3 Insulation Thickness

6.3.1 Structural Dimensions The number of conductors and the maximum diameter of individual strands within each conductor shall comply with the requirements specified in Tables 1, 2, and 3 of GB/T 3956-2008, respectively. The outer diameter of the conductor shall conform to the specifications given in Tables C.1, C.2, and C.3.

6.3.2 Insulation and Outer Sheath Thickness The average total thickness of the insulation layer shall not be less than the nominal value, and the minimum thickness at any point shall not be less than 90% of the nominal value minus 0.1 mm; the insulation and outer sheath thicknesses shall respectively comply with the requirements specified in Table 3 and Clause 5.7.2.4.

6.3.3 Armored metal wires and metal tapes shall comply with the requirements specified in Clause 5.6.2 of JG/T 442-2014.

6.3.4 Outer Diameter If required by the sampling inspection, the cable’s outer diameter shall be measured.

6.4 DC Resistance of Conductors at 20°C The maximum DC resistance of conductors at 20°C shall comply with the requirements specified in Tables 1, 2, and 3 of GB/T 3956-2008.

6.5 Insulation Resistance Constant 6.5.1 At 20°C, the insulation resistance constant shall not be less than 3,670 MΩ·km. 6.5.2 Insulation Resistance Constant at Maximum Conductor Temperature: At 90°C, 105°C, and 125°C, the insulation resistance constant shall not be less than 3.67 MΩ·km.

6.6 4-hour voltage performance: The insulation shall show no breakdown.

6.7 Withstand Voltage Performance of Finished Products: The insulation shall exhibit no breakdown.

6.8 The tensile strength and elongation at break of aluminum alloy single wires shall comply with the requirements specified in Clause 5.1.1.2 of JG/T 442-2014.

6.9 Bending Performance of Aluminum Alloy Single Wire: The specimen shall be bent at least 10 cycles around a mandrel of the same diameter as the specimen, without any fracture occurring in the single wire.