Imagine this scenario: deep beneath the ocean's surface, a high-voltage power cable—like a vital artery—connects continents, delivering electricity to millions of homes and businesses. Then suddenly, this critical lifeline fails due to microscopic impurities, plunging cities into darkness and causing economic turmoil. The consequences are severe: repairing undersea cables is extraordinarily expensive and time-consuming, with losses mounting by the hour.

In this competitive market, how can cable manufacturers distinguish themselves and earn customer trust while ensuring stable power transmission? The answer lies in one uncompromising principle: the relentless pursuit of insulation material purity.

High-voltage cables, particularly medium and high-voltage cables, function like the heart of power distribution systems. The insulation material serves as their protective layer—a component of paramount importance. Currently, cross-linked polyethylene (XLPE) dominates as the primary insulation material for medium and high-voltage cables.

Cross-linked polyethylene (XLPE) is a thermosetting material derived from polyethylene through a cross-linking process. Under high pressure and with organic peroxides, polyethylene transforms from a thermoplastic into an elastic material, granting XLPE exceptional properties that make it ideal for high-voltage cable insulation:

• Minimal dielectric loss: XLPE's low dielectric loss means less energy dissipation during transmission, ensuring higher efficiency.
• Superior electrical properties: Excellent electrical strength, corona resistance, and arc resistance enable XLPE to withstand high-voltage fields.
• Outstanding physical properties: High mechanical strength, heat resistance, and chemical corrosion resistance allow reliable operation in harsh environments.
• Thermal deformation and aging resistance: XLPE maintains stable performance even at elevated temperatures.
• Higher current capacity: XLPE cables can carry more current than conventional alternatives of the same size.
• Easy installation: Lightweight and flexible, XLPE cables simplify deployment and reduce construction timelines.

Recently, Prysmian introduced innovative cables using high-performance thermoplastic elastomers (HPTE). While matching XLPE's performance, HPTE offers distinct manufacturing advantages:

• No cross-linking required: Eliminates byproducts from the cross-linking process, making it more environmentally friendly.
• Recyclability: HPTE cables can be reused, reducing waste.
• Shorter production cycles: Enables faster response to market demands.
• Reduced facility footprint: Requires less production space, lowering costs.
• Compatibility: Works seamlessly with existing network components, facilitating grid upgrades.

Both XLPE and HPTE serve as the "heart" of high-voltage cables, safeguarding power transmission reliability.

For high and extra-high voltage cables, insulation material purity is non-negotiable. Higher purity directly correlates with lower breakdown risks. Even a 50-micron metal impurity can compromise the final product, leading to exorbitant follow-up costs.

Consider an undersea cable operating flawlessly for decades—until a microscopic metal particle triggers partial discharges under electric stress. Over time, these discharges intensify, culminating in insulation failure and catastrophic cable failure.

• Astronomical repair costs: Contamination-induced undersea cable failures can cause weeks of downtime, with severe economic and social consequences.
• Industry-wide production impacts: Contaminated materials or defective cables that fail discharge tests disrupt manufacturing efficiency and inflate costs.

Extra-high voltage cables undergo rigorous withstand voltage tests at 2.5 times their rated voltage—a brutal examination of insulation integrity.

• Breakdown consequences: Typical production facilities experience 5-6 annual breakdowns during testing, each potentially costing €150,000 before delivery.
• Schedule disruptions: Breakdowns delay deliveries, creating contractual complications.
• Reputation damage: Unapproved splices may tarnish manufacturers' quality image and trigger penalty clauses.

To ensure cable reliability, industry standards impose strict purity requirements:

• High-voltage cable standards often mandate exclusion of contaminants exceeding 75 microns.
• The AEIC guidelines require cable designs to last at least 40 years, necessitating 100% material purity inspection—sample testing cannot reliably eliminate all contaminants.

Only comprehensive inspection guarantees every meter meets the highest quality standards.

Currently, cable manufacturers typically use mesh filters to capture impurities in XLPE and HPTE melts before they enter cables. These filters, positioned between the extruder and cross-linking head, face operational challenges:

• Clogging: Over time, filters accumulate scorched material or excessive contaminants, causing extruder pressure spikes.
• Production halts: Frequent filter replacements require production stoppages and subsequent splicing.
• Splice risks: Manually made splices represent critical weak points, especially in undersea applications. Manufacturers therefore aim to minimize splices in long cables.

Clogged filters reduce productivity, demanding more reliable impurity detection and sorting solutions.

Current particle detection systems primarily serve laboratory or production line monitoring. Most rely on optical technology to detect surface contaminants but cannot identify internal impurities.

While effective for surface defects in transparent or translucent materials, optical techniques cannot penetrate particles to detect internal contamination.

X-ray technology's penetration capability enables internal defect detection. As X-rays pass through materials, their attenuation varies with density, thickness, and atomic composition—allowing precise impurity identification.

Modern detection systems combine X-ray and optical technologies for 100% online quality assurance. Image processing software identifies, classifies, and automatically removes contaminants as small as 50 microns.

XLPE consists mainly of carbon (6 protons), while common steel contaminants contain iron (26 protons). This 20-proton difference creates stark X-ray contrast, enabling precise metal detection.

Advanced camera technology and lighting systems capture material flow at industrial speeds. Powerful algorithms then identify surface defects exceeding predefined thresholds.

This dual approach detects both internal and surface contaminants, including:

• X-ray: Metals, organic pollutants, and inhomogeneities (e.g., TiO2) in transparent, colored, or semiconductive materials
• Optical: Surface defects like black spots, foreign particles, and dissimilar materials

Installed between supply hoppers (containing octabins, bags, or silos) and extruder hoppers, these systems purify materials via gravity feed before extrusion begins.

Beyond online systems, modular solutions offer offline detection and analysis for pellets, flakes, and tapes—ideal for smaller throughputs, sampling, or incoming material inspection.

• Online detection: Real-time impurity removal during production
• Offline detection: Sample quality assessment

Systems deploy X-ray or optical sensors based on application needs, detecting contaminants above 50 microns during production or sampling.

X-ray lab equipment can analyze 3,000 pellets (200ml) in seconds, optically highlighting contaminants for easy removal—perfect for quality refinement.

Leading manufacturers combine online and offline systems for comprehensive process optimization:

• Online: Rapid bulk impurity removal
• Offline: Detailed analysis of removed contaminants

This interaction enables contamination source tracing through database creation, preventing future quality issues.

This examination underscores the critical importance of XLPE and HPTE purity for medium and high-voltage cable insulation. Modern quality control systems detect and remove contaminants before extrusion—whether originating from raw materials or introduced during handling.

Even with traditional filters, this technology prevents clogging by eliminating contaminated pellets, extending production runs while ensuring safety. The X-ray/optical combination guarantees 100% quality control by detecting both internal and surface defects.

Offline analysis of removed contaminants further enhances production processes through purity monitoring and preventive analytics.

• Quality foundation: High-purity materials enable cables with superior insulation and long-term reliability
• Cost efficiency: Eliminates expensive discharge test failures and boosts production line efficiency
• Market differentiation: Delivering premium-quality, high-reliability cables builds customer trust and competitive edge

In the high-stakes world of undersea power transmission, purity isn't just a specification—it's the ultimate differentiator.