What is Cross-Linked Polyethylene (XLPE)? How is it Used?

Wire and cable can sometimes be confusing, especially when discussing insulation materials.  

Shenxing Cable Product Page

One insulation type is cross-linked polyethylene (XLPE), which can be based on either low-density polyethylene (LDPE) or high-density polyethylene (HDPE) and is used to insulate conductors. XLPE uses a grafted polymer combined with a catalyst to speed up the crosslinking reaction and provide other properties. Several different catalysts can be used with the same graft, depending on the application or specification. 

Unlike thermoplastic materials that can be reheated and remolded without changing their chemical makeup, you only get one chance with thermosets. This is because materials like XLPE change and become stronger during the post-extrusion curing process.  

In even simpler terms, thermosets feature crosslinked chains while thermoplastics don’t.  

When the crosslinking reaction occurs, like those in XLPE wires, it changes the physical properties of the plastic. Crosslinking occurs after the material has been extruded onto the conductor and begins to cure, building links between chains. Curing (hardening) is accelerated by exposure to heat and moisture. 

The result is an XLPE insulated cable with high tensile strength and other benefits.  

Why Do We Use XLPE Cable?  

The cross-linking process does more than make the cable stronger – it fundamentally changes its makeup to produce a remarkably impressive insulation.  

Because of this super-strong insulation, cross-linked polyethylene has become a common choice across many industries, including power transmission, industrial applications like power, lighting control and signaling, oil and gas, and aerospace use.  

Crosslinking reactions change the polymer’s molecular weight, making XLPE insulation more rigid and durable. This makes it excellent for underground or underwater applications and where stress is expected. The stronger bonding in the plastic also lends itself to several other improvements.  

Crack and Abrasion Resistance  

Stronger insulation means the cable offers better protection during installation and holds up better in harsh environments or varying temperatures. The wire is also better equipped to withstand long-term use by reducing environmental stress cracking.  

Stress Resistance  

Higher stress tolerance means the cable can be manipulated more without showing signs of damage. This means conductors can stretch, have better physical strength, and absorb crushing better than other insulation types.  

Stress resistance also applies to electrical stress, which happens when voltage flowing through the conductor creates hot spots in the wire. If enough damage occurs in these spots, the cable could eventually fail. XLPE insulation helps distribute electrical stress more evenly, preventing hot spots from forming and extending the wire’s lifespan.  

Oil and Gas Resistance  

LDPE and HDPE are already good at resisting oil and gas damage, but crosslinking them boosts those properties even more, including at higher temperatures. As a result, crosslinked polyethylene can be used in harsher environments.  

Heat Resistance  

Once crosslinked, XLPE does not melt, so it excels in areas where the temperatures can get hot. Insulated conductors can withstand operating temperatures up to 120°C and even above 150°C in some cases without suffering damage.  

The insulation also protects other nearby wires and cables from heat generated by electrical currents traveling through a copper wire.  

Different Catalysts, Different Strengths  

One major piece of the XLPE production process is adding a catalyst to help facilitate cross-linking. By adding different catalyst compounds to the polymer mix, the insulation can take on other properties like sunlight resistance, flame retardance, and anti-oxidation characteristics that increase the usable lifespan of the wire.  

XLPE is also available in a low-smoke, zero-halogen (LSZH) product if it’s used with a halogen-free flame-retardant material. The wire’s characteristics depend on the catalyst masterbatch used and what properties the wire needs.  

Where is XLPE Insulation Common?  

You can typically find XLPE used as insulation on low-, medium-, and high-voltage cables across many industries. At Kris-Tech, we use XLPE insulation for several products, including:

• VNTC and XPTC tray cable  
• Photovoltaic (PV) wire  
• XHHW-2  
• RHW-2  
• USE-2  
• RHH  
• SIS  

The insulation is also commonly used for medium voltage applications ranging from 2-5kV or made into a halogen-free product for use in office spaces, closed areas, mass transit, and other high-traffic locations. 

One Insulation, Many Uses  

No matter the industry, you’re likely to find XLPE insulation used in some form – sometimes not even as insulation. For example, PEX (polyethylene–crosslinked) tubing has been a popular alternative for copper and Polyvinyl Chloride (PVC) tubing in plumbing applications for decades, thanks to its durability and ability to withstand stress.  

Next time you need wire insulation capable of surviving nearly anything thrown at it, think of XLPE and install it confidently!

Ⅰ. Advantages of Cu cables over aluminum cables

1. Low resistivity

The resistivity of aluminum core cable is about 1.68 times higher than that of copper core cable.

2. Good ductility

The ductility of copper alloy is 20-40%, the ductility of electrical copper is more than 30%, while the ductility of aluminum alloy is only 18%.

If you want to learn more, please visit our website Copper core cross-linked polyethylene insulated power cable.

3. High strength

As for allowable stress at room temperature, copper is 7~28% higher than aluminum. Especially the stress at high temperature, the difference between the two is even greater.

4. Anti-fatigue

Aluminum is easy to crack after repeated bending, while copper is not easy. In terms of flexibility targets, copper is also about 1.7 to 1.8 times higher than aluminum.

5. Good stability and corrosion resistance

The copper core is resistant to oxidation and corrosion, while the aluminum core is simply oxidized and corroded.

6. Large current carrying capacity

Because of the low resistivity, the Cu cable of the same cross-section is about 30% higher than the allowable current carrying capacity (the maximum current that can pass through) of the aluminum core cable.

7. Low voltage loss

Because the resistivity of the copper core cable is low, the same current flows in the same section. The voltage drop of the copper core cable is small. The same transmission interval can ensure higher voltage quality; under the agreed voltage drop condition, the copper core cable transmission power reaches a longer interval, that is, the power supply coverage area is large, which is conducive to network planning and reduces the number of power supply points.

8. Low heating temperature

Under the same current, the copper core cable with the same cross-section has much smaller heat than the aluminum core cable, which makes the operation safer.

9. Low energy consumption

Because of the low electrical resistivity of copper, it is clear that copper cables have low power loss compared to aluminum cables. This is conducive to improving the utilization rate of power generation and protecting the environment.

Ⅱ. The advantages of aluminum cables over Cu cables

1. The price of aluminum cables is cheap

Copper rods are more than 3 times the price of aluminum rods, and the proportion of copper is 3.3 times that of aluminum. Therefore, aluminum core cables are much cheaper than copper core cables and are suitable for low-cost projects or temporary electricity use.

2. The cable is very light

The weight of the aluminum core cable is 40% of the copper core cable, and the construction and transportation costs are low.

3. Anti-oxidation

Aluminum quickly reacts with oxygen in the air to form an oxide film, which can prevent further oxidation. Therefore, aluminum wire is a necessary material for high-voltage, large-section, and large-span overhead power transmission.

PVC-Insulated Cables

PVC-Insulated Cables are widely used and have a long term permissible operational temperature of up to 70°C. These cables have perfect bending properties for easy installation and maintenance, which makes them a popular choice for indoor and outdoor uses for voltage requirements of 1kV and below. Should there be a requirement for ground emplacement, the armoured cable is preferred for higher electrical and mechanical protection.

XLPE-Insulated Cables

XLPE (Cross-linked polyethylene) is an excellent insulation material that has several advantages over conventional thermoplastic insulating material. Some advantages included zero halogen & permissible operational temperature up to 90°C, allowing the cables to with stand a greater current rating compared with PVC cables. The variance gets wider as the conductor size increases, which is also the reason XLPE insulated cables are widely chosen where bigger cables are required for main power supply.

Contact us to discuss your requirements of Medium Voltage Power Distribution Cables. Our experienced sales team can help you identify the options that best suit your needs.