What is XLPE? Features and applications of XLPE cables

1.1 What is XLPE?

XLPE stands for Cross-Linked Polyethylene, a type of polyethylene plastic that has undergone a cross-linking process to form a three-dimensional molecular structure. This network significantly enhances the material's ability to withstand high temperatures and mechanical stress.

Simply put, XLPE is polyethylene that contains organic peroxide compounds. Under high temperature and pressure conditions, in an inert gas environment, the peroxide initiates a chemical reaction with the polyethylene, forming cross-linked polyethylene (XLPE).

Unlike thermoplastic materials, which can be melted and reshaped multiple times without altering their chemical structure, thermoset materials like XLPE undergo a permanent transformation during the curing process. Once cured, the material becomes rigid and retains its shape under high thermal and electrical stress.

The cross-linking reaction in XLPE cables occurs after the polymer is extruded around the conductor. This post-extrusion curing process forms bonds between polymer chains, typically accelerated by heat and moisture. The result is an XLPE-insulated cable with improved tensile strength and superior physical properties.

1.2 What are XLPE cables?

XLPE cables are electrical cables with insulation made from cross-linked polyethylene. They are widely used in power transmission and distribution systems due to their excellent thermal resistance, moisture resistance, and chemical corrosion resistance - making them ideal for underground or underwater installations.

The XLPE insulation is produced by chemically cross-linking polyethylene molecules, resulting in a material with high mechanical strength, excellent thermal stability, and superior voltage resistance.

Compared to PVC-insulated cables, XLPE cables offer higher operating temperatures, longer service life, and greater safety in heavy-duty or high-specification industrial applications.

The cross-linking process not only enhances the strength of XLPE cables but also fundamentally transforms the material's performance. The robust molecular structure improves the cable's durability, operational efficiency, and lifespan.

2.1 Resistance to cracking and abrasion

XLPE insulation is highly durable and resistant to mechanical impact during installation. It maintains stable performance under harsh environmental conditions and fluctuating temperatures. XLPE also minimizes environmental stress cracking over long-term use.

2.2 Excellent stress resistance

XLPE cables can withstand high levels of mechanical and electrical stress, allowing them to be bent, pulled, or manipulated during installation without damage. The conductor and insulation can absorb compression and tensile forces while maintaining integrity.

This resilience extends to electrical stress, such as hotspots caused by high voltage. XLPE effectively disperses electrical stress, preventing damage and extending cable life.

2.3 Superior heat resistance

XLPE cables can operate at temperatures up to 120°C, and even above 150°C under specific conditions without degradation. The insulation also prevents heat transfer to nearby cables, improving the overall safety and efficiency of the electrical system.

These properties make XLPE ideal for extreme industrial environments like petrochemical or chemical plants.

2.4 Additional properties

The cross-linking process can be enhanced with catalysts that modify the insulation's properties. Depending on the additives used, XLPE can be made UV-resistant, flame-retardant, or oxidation-resistant, further extending its service life.

Additionally, XLPE can be manufactured as LSZH (Low Smoke Zero Halogen), making it suitable for installations requiring fire safety and low toxic emissions.

Due to their outstanding properties, XLPE plays a critical role in cable manufacturing. It is especially effective in harsh conditions such as underground or underwater installations, where exposure to moisture, heat, and pressure is significant.

Common applications include:

• Medium and high voltage power distribution: Widely used in utility grids due to superior insulation.
• Underground and overhead transmission: Suitable for both buried and overhead power transmission lines.
• Industrial installations: Preferred in chemical plants, substations, and high-temperature or chemically aggressive environments.
• High-temperature zones: Ideal for areas exposed to extreme heat or corrosive agents where conventional insulation degrades.