Cross linked polyethylene cable is divided into chemical cross-linking and physical cross-linking. Cable manufacturer TST CABLES decrypts the manufacturing process and process of cross-linked polyethylene cable.
Introduction to cross-linked polyethylene cable
Cross-linked polyethylene cable (XLPE cable) is widely used in power transmission systems due to its excellent electrical properties, thermal stability and mechanical strength, especially in the application of medium and high voltage cables. Irradiated cross-linked polyethylene insulated control cable with AC rated voltage of 450/750V and below is used as control connection line in control, monitoring circuits and protection lines with flame retardant requirements. The core feature of cross-linked polyethylene cable is the use of cross-linked polyethylene as insulation material. XLPE is a modified material that transforms polyethylene molecular chains from linear molecular structures to three-dimensional mesh molecular structures by chemical or physical methods.
The manufacturing of cross-linked polyethylene cable is a complex process involving multiple steps and high-end equipment. By precisely controlling each manufacturing link, it can be ensured that the cable has excellent electrical properties, reliable mechanical strength and long life. These characteristics make XLPE cable an important part of modern power transmission systems. XLPE cables can be divided into several types according to the cross-linking process, of which the two main types are chemical cross-linking (commonly known as cross-linked polyethylene cable) and physical cross-linking (commonly known as irradiation cross-linked polyethylene cable). The following are the main differences between the two types of cables:
Chemical Cross-linked Polyethylene Cable
Cross-linking Principle: Chemical cross-linking is achieved by adding a cross-linking agent (such as peroxide or silane) to the polyethylene material, and then promoting the cross-linking reaction by heating to transform the linear polyethylene molecular chain into a three-dimensional network structure.
Cross-linking process: Usually after extruding the insulation layer, the cable is placed in warm water and heated, or heated in air to induce the cross-linking reaction.
Advantages:
The cross-linking process is relatively simple and low cost.
Suitable for large-scale production.
Disadvantages:
The cross-linking speed is slow.
There may be problems with residual cross-linking agents, which affect the long-term performance of the cable.
Physical Cross-linked Polyethylene Cable
Cross-linking Principle: Physical cross-linking (irradiation cross-linking) is to irradiate the polyethylene material with high-energy electron beams or gamma rays to break the molecular chains and then form a cross-linked structure under heating conditions.
Cross-linking process: After the insulation layer is extruded, the cable is irradiated through a device containing a high-energy electron beam or gamma rays to induce a cross-linking reaction.
Advantages:
The cross-linking speed is fast and the efficiency is high.
No cross-linking agent needs to be added, so there is no residue problem.
The electrical and mechanical properties of the cable are better.
Disadvantages:
The investment cost of irradiation equipment is high.
For cables with large cross-sections, a more complex irradiation process is required.
Characteristics of Cross-linked Polyethylene Cable (XLPE cable)
Thermosetting: XLPE material is thermosetting, which means that once cross-linked, it will not melt at high temperatures like ordinary polyethylene.
Heat resistance: XLPE has high heat resistance and can work at high temperatures for a long time, which enables the cable to maintain good performance under high load conditions.
Mechanical strength: The cross-linking process improves the mechanical strength of polyethylene, making the cable have better resistance to tension and tearing.
Electrical properties: XLPE has excellent dielectric properties, including low dielectric constant, low dielectric loss and high breakdown strength, which makes the cable have good electrical properties.
Conditions for use of cross-linked polyethylene cables:
- Rated voltage U0/U is 450/750V;
- The long-term allowable operating temperature of the cable conductor is 90℃; further, the operating temperature range of the cable: -40℃~105℃, which can reach 125℃ in a short time
- The laying temperature of the cable is not lower than 0℃, and the allowable bending radius of the cable without armor layer should be not less than 6 times the outer diameter of the cable; the cable with armor structure should be not less than 12 times the outer diameter of the cable.
- The structure is simple, easy to install and lay, and suitable for occasions with flame retardant requirements.
Structure of cross-linked polyethylene cable
Cross-linked polyethylene cable usually consists of the following parts:
Conductor: A conductor usually made of copper or aluminum, used to transmit current.
Insulation layer: Made of cross-linked polyethylene (XLPE), it is wrapped around the conductor to provide electrical isolation.
Shielding layer: In order to reduce electromagnetic interference and improve the electrical performance of the cable, a shielding layer is usually added outside the insulation layer.
Sheath: The outermost protective layer, usually made of materials such as polyvinyl chloride (PVC) or polyethylene (PE) to protect the cable from the external environment.
Cross-linked polyethylene cable manufacturing process
The manufacturing process of cross-linked polyethylene cable includes several key steps:
Conductor production: Copper or aluminum conductors are prepared by drawing and twisting.
Insulation extrusion: The insulation layer is extruded using three-layer co-extrusion technology, including the inner shielding layer, XLPE insulation layer and outer shielding layer.
Cross-linking: The XLPE material is cross-linked by chemical (such as silane cross-linking) or physical (such as radiation cross-linking) methods.
Sheath extrusion: A protective sheath is extruded outside the shielding layer or armor layer.
Application areas of cross-linked polyethylene cables
Power transmission: Suitable for power transmission of underground or overhead lines.
Industrial facilities: Suitable for industrial sites such as factories, mines, and oil platforms.
Construction field: Used for distribution systems in commercial and residential buildings.
Railway transportation: Used for power supply systems of rail transportation systems such as railways and subways.
Cross-linked polyethylene cable has become an important part of the power transmission and distribution field due to its excellent electrical properties, thermal stability and mechanical strength. Through strict manufacturing process and quality control, it can ensure that the cable maintains stable performance in various harsh environments. Whether it is chemical cross-linking or physical cross-linking, each process has its unique advantages and scope of application, and cable manufacturers can choose the most suitable manufacturing method according to specific needs.
Below, TST CABLES will explain the main process steps of cross-linked polyethylene cable manufacturing in detail:
Preparation of raw materials for cross-linked polyethylene cable:
Preparation of conductor materials (such as copper or aluminum).
Preparation of insulation materials (XLPE).
Preparation of shielding materials and sheath materials.
Manufacturing of cross-linked polyethylene cable conductors:
Wire drawing annealing: The copper or aluminum raw materials are stretched through a wire drawing machine to reduce their diameter, and annealing is performed at the same time to improve the softness and conductivity of the conductor.
Tight compression stranding: Multiple strands of fine wires are twisted together in a certain arrangement to form the required conductor structure.
Extrusion of cross-linked polyethylene cable insulation:
Three-layer co-extrusion: Using three-layer co-extrusion technology, the inner shielding layer, XLPE insulation layer and outer shielding layer are extruded at the same time. This process is usually completed on a special extruder head to ensure good insulation performance.
Drying and degassing: Remove air and moisture from the insulation layer through vacuum drying to improve the quality of the insulation layer.
Cross-linked polyethylene cable shielding layer production:
Wrapping buffer layer: Wrap a layer of buffer material outside the insulation layer to protect the insulation layer from mechanical damage.
Metal shielding layer: Add a metal shielding layer by wrapping or extruding to enhance the anti-interference ability of the cable.
Cross-linked polyethylene cable sheath extrusion:
Extruded aluminum sheath: Extrude an aluminum sheath outside the shielding layer to further improve the mechanical strength and waterproof performance of the cable.
Asphalt coating: Apply a layer of asphalt outside the aluminum sheath to improve its corrosion resistance.
Extruded outer sheath: Extrude a polymer sheath outside the aluminum sheath to protect the cable from the outside environment.
Cross-linked polyethylene cable finished product testing:
The cable is subjected to a series of tests, including electrical performance tests, mechanical performance tests, environmental adaptability tests, etc., to ensure that it meets the specified standards.
Packaging and storage of cross-linked polyethylene cables: Qualified cables are properly packaged for transportation and storage. Special manufacturing process of cross-linked polyethylene cables Warm water cross-linking: Some cables use warm water cross-linking process, that is, immersing the cables in hot water, and the heat in the water causes the XLPE material to undergo a chemical reaction to form a three-dimensional network structure. Radiation cross-linking: Radiation cross-linking is another commonly used cross-linking process. The XLPE material is irradiated with high-energy electron beams or gamma rays to cause its molecular chains to undergo a cross-linking reaction to form a cross-linked structure. Silane cross-linking: Silane cross-linking is a method of promoting the cross-linking of XLPE materials under heating conditions by adding silane cross-linking agents. Technical characteristics of cross-linked polyethylene cables Insulation layer: The XLPE insulation layer has high electrical strength, good thermal stability and long service life. Conductor structure: For cables with large cross-sections, the conductor usually adopts a compact circular structure to improve the heat dissipation capacity and electrical performance of the cable. Shielding layer: The metal shielding layer can effectively reduce electromagnetic interference and help improve the mechanical protection of the cable. Cooperate with TST CABLES to customize high-quality cross-linked polyethylene cable (XLPE cable)
In a rapidly changing world, stable and reliable power transmission is the cornerstone of connecting the future. The cross-linked polyethylene cable (XLPE cable) developed and produced by TST CABLES, with its excellent electrical performance and durable quality, ensures that the XLPE cable can operate stably in any extreme environment and will become the most solid backing for your equipment.
The above is the world’s leading XLPE high-temperature cable and wire production process. If you have a need for customized cables, further technical support or customized cable solutions, you can visit the TST CABLES official website or send an email to the professional cable engineer of TST cable manufacturer at any time (email: lixiangchao@testeck.com, please state your country, your industry, and your required specifications and quantity in the email).
This post is also available in:
English
