What Is TR-XLPE?

Tree-Retardant Cross-Linked Polyethylene (TR-XLPE) is an advanced thermoset insulation material used in medium- and high-voltage cables, such as RHW-2 and RWU90 discussed previously. Unlike standard XLPE, TR-XLPE incorporates tree-retardant additives to prevent water treeing—dendritic microscopic cracks caused by moisture penetration that degrade insulation over time. Introduced in the early 1980s, TR-XLPE addresses the premature failure of early XLPE cables due to water treeing, offering enhanced durability, electrical performance, and longevity. It complies with standards like UL 44, UL 854, CSA C22.2 No. 38, and ICEA, making it a preferred choice for underground and wet-environment applications, similar to RWU90 or submarine cables.

Composition of TR-XLPE Cables

TR-XLPE cables are engineered for reliability in harsh conditions, with a composition that enhances their performance:

• Conductor: Stranded or solid copper or aluminum, typically 8 AWG to 750 kcmil, similar to 6 AWG or multi-conductor cables, providing high conductivity (59.6 MS/m for copper).
• Insulation: Cross-linked polyethylene (XLPE) with tree-retardant additives (approximately 2% proprietary compounds), forming a three-dimensional molecular structure for superior thermal, electrical, and mechanical strength.
• Tree-Retardant Additives: Proprietary compounds, such as those from Dow Chemical (HFDC-4202) or Borealis (LE4212), prevent water tree formation, enhancing insulation longevity in wet environments.
• Jacket: Polyvinyl chloride (PVC) or additional XLPE layers for protection against moisture, UV, and mechanical stress, akin to RWU90’s robust jacket.
• Shielding: Copper tape or concentric neutral for medium-voltage applications (5kV–35kV), reducing electromagnetic interference, similar to MV or submarine cables.

The cross-linking process ensures thermal stability up to 90°C (250°C short-circuit) and compliance with ASTM D6097 for water tree resistance testing.

Key Advantages of TR-XLPE

TR-XLPE cables offer significant benefits over standard XLPE and other insulations like PVC or EPR, building on the strengths of XLPE used in RHW-2 and RWU90:

• Water Tree Resistance: Tree-retardant additives prevent dendritic cracks, extending cable life to over 40 years in wet or underground environments, unlike standard XLPE’s 20–30 years.
• High Dielectric Strength: TR-XLPE maintains XLPE’s high dielectric strength, minimizing current leakage and ensuring safe, efficient power transmission, critical for solar farms or urban grids.
• Low Dielectric Loss: Minimal energy loss during transmission (lower than EPR or PILC), enhancing efficiency for long-distance applications, such as renewable energy installations.
• Thermal Stability: Operates at 90°C continuously and withstands short-circuit temperatures up to 250°C, outperforming PVC (70°C) and matching RHW-2/RWU90 ratings.
• Corrosion Resistance: Resists saline and chemical exposure, ideal for coastal or industrial settings, similar to marine or H07RN-F cables.
• Cost-Effectiveness: Balances performance and cost, with savings up to 50% in lifecycle costs compared to EPR, due to reduced maintenance and replacement needs.
• Mechanical Strength: Enhanced tensile strength and flexibility compared to PVC, facilitating installation in conduits or direct burial, akin to RWU90.
• Environmental Reliability: Performs reliably in humid, UV-exposed, or chemically harsh environments, reducing failure risks in applications like underground distribution.

Laboratory tests (e.g., ASTM D6097) and field performance since 1983 confirm TR-XLPE’s superior resistance to water treeing and electrical breakdown.

Applications of TR-XLPE Cables

TR-XLPE cables are widely used in scenarios requiring reliable power transmission, similar to RHW-2, RWU90, or 6 AWG cables:

• Urban Power Grids: Primary insulation for medium-voltage (5kV–35kV) underground distribution, ensuring reliability in densely populated areas.
• Renewable Energy: Connects solar panels or wind turbines to inverters, leveraging low dielectric loss and UV resistance, akin to RWU90 in solar applications.
• Industrial Facilities: Powers motors, control systems, and equipment in factories, with resistance to chemicals and heat, similar to trailing or multi-conductor cables.
• Underground Installations: Ideal for direct burial or conduit systems in wet environments, preventing water treeing, comparable to RWU90 or submarine cables.
• Utility Distribution: Supports long-distance power transmission with minimal losses, used in substations and service entrances, like MV or 6 AWG cables.

Their adoption in the U.S. as the predominant medium-voltage insulation underscores their reliability.

TR-XLPE vs. XLPE Comparison Table

The table below compares TR-XLPE and standard XLPE, highlighting key differences:

Note: Specifications based on NEC 2020, UL/CSA, and ASTM D6097 standards. Verify with manufacturers for specific conditions.

Tips for Selecting TR-XLPE Cables

Choosing TR-XLPE cables ensures optimal performance in demanding applications:

• Evaluate Environment: Select TR-XLPE for underground, wet, or coastal installations to leverage water tree resistance, similar to RWU90 or marine cables.
• Verify Voltage Rating: Ensure compatibility with 5kV–35kV systems, matching load per NEC ampacity tables (e.g., 65A for 6 AWG copper at 90°C).
• Check Manufacturer Quality: Opt for suppliers using Dow HFDC-4202 or Borealis LE4212 for proven performance, per ICEA and AEIC standards.
• Ensure Grounding: Include grounding conductors for safety, per NEC, as with RHW-2 or grounding wire applications.
• Assess Lifecycle Costs: Prioritize TR-XLPE for long-term savings despite higher initial costs, reducing maintenance compared to XLPE or PVC.
• Consult Professionals: Engage electricians for NEC-compliant sizing, shielding, and installation, akin to H07RN-F or MV cable practices.

These steps align with selecting reliable cables like LSOH, cold temperature, or RHW-2/RWU90.

Conclusion

TR-XLPE cables represent a significant advancement in medium- and high-voltage cable insulation, addressing the water treeing limitations of standard XLPE used in cables like RHW-2 and RWU90. With tree-retardant additives, TR-XLPE offers superior water tree resistance, high dielectric strength, low dielectric loss, and thermal stability, ensuring a lifespan exceeding 40 years in wet and harsh environments. Its applications in urban grids, renewable energy, and industrial settings highlight its reliability, while cost-effectiveness and compliance with UL, CSA, and ICEA standards make it a preferred choice. By selecting TR-XLPE for underground or high-stress installations, users achieve efficient, safe power transmission, building on the durability of cables like 6 AWG, H07RN-F, or RWU90 discussed previously.