The NA2XSY, NA2XS2Y, NA2XS(F)2Y, and NA2XS(FL)2Y series represent a family of specialized underground medium voltage (MV) aluminium power cables, engineered with advanced watertight and water-blocking technologies to thrive in moisture-prone, underground environments. Designed primarily for MV power transmission (typically 10kV, 20kV, and 35kV), these cables leverage aluminium conductors to balance electrical performance, cost-efficiency, and weight advantages, making them ideal for large-scale underground power distribution networks, industrial zones, and infrastructure projects where water ingress and environmental durability are critical concerns. At the core of all four models is the aluminium conductor, a material selected for its optimal blend of conductivity (≈37MS/m at 20°C) and cost-effectiveness. Compared to copper conductors, aluminium reduces material costs by approximately 40% while maintaining sufficient current-carrying capacity for MV applications—critical for projects with tight budgets or large cable lengths. The conductors are typically stranded (Class 2 stranded per IEC 60228) to enhance flexibility, allowing easier installation in underground trenches or confined spaces, and are treated with anti-corrosion coatings to prevent oxidation, a key requirement for long-term underground service. A defining feature across the series is their watertight and water-blocking design, a non-negotiable attribute for underground use where soil moisture, groundwater, or accidental water seepage poses risks to electrical performance. This design incorporates multi-layer protection: inner water-blocking tapes (impregnated with water-swellable polymers) wrapped around the conductor to stop moisture from spreading along the cable core, and a semi-conductive water-blocking buffer layer between the conductor and insulation to seal any micro-gaps. Additionally, the outer sheath (varies by model) is extruded with a dense, moisture-resistant compound that prevents water penetration from the external environment. This comprehensive water-blocking system ensures the cables maintain stable insulation resistance (exceeding 1000MΩ·km at 70°C) and avoid electrical breakdown even in permanently damp or flooded underground conditions. While sharing core watertight and aluminium conductor features, the four models differ in structural design and performance enhancements, tailored to specific application needs: NA2XSY: As the base model, it features a single outer sheath (typically PVC or PE) and standard XLPE (cross-linked polyethylene) insulation. Its design focuses on basic water resistance and underground durability, making it suitable for general underground MV distribution in residential areas, small industrial parks, or non-hazardous zones where fire safety requirements are moderate. The single sheath balances protection and cost, offering a reliable, economical solution for standard moisture-prone environments. NA2XS2Y: Distinguished by its double outer sheath (denoted by the “2Y” in the model name), this variant adds an extra layer of protection against mechanical damage and water ingress. The dual sheaths—often a combination of XLPE inner insulation and a tough, impact-resistant PE outer sheath—enhance resistance to soil pressure, rodent bites, and chemical corrosion (e.g., from acidic or alkaline soils). It is ideal for high-traffic underground areas (e.g., beneath roadways, commercial districts) or regions with harsh soil conditions, where the risk of sheath damage during installation or operation is higher. NA2XS(F)2Y: Integrates flame-retardant properties (indicated by “F”) into the double-sheath design. The sheath and insulation materials are formulated with halogen-free flame-retardant additives (compliant with IEC 60332-1 for vertical flame propagation), ensuring the cable self-extinguishes within 60 seconds if exposed to fire and limits flame spread. This makes it suitable for underground installations near high-risk areas such as industrial facilities with flammable materials, residential complexes, or public infrastructure (e.g., subway power tunnels), where fire safety is a top priority. NA2XS(FL)2Y: The most advanced model, incorporating low-smoke flame-retardant features (marked by “FL”). In addition to flame retardancy, its materials (including the sheath and insulation) are engineered to release minimal smoke and toxic gases (e.g., chlorine, hydrogen chloride) during combustion—compliant with IEC 61034 for smoke density and IEC 60754 for halogen acid gas emission. This is critical for confined underground spaces like utility tunnels, subway stations, or underground shopping mall power lines, where smoke accumulation or toxic fumes could endanger human life or delay emergency response in case of a fire. All four models share key performance advantages beyond water resistance and structural differences. Their XLPE insulation (common across the series) provides excellent high-temperature stability (long-term operating temperature: 90°C, short-circuit temperature: 250°C for 5 seconds) and aging resistance, ensuring a service life of 25+ years. The underground-specific design also includes resistance to soil corrosion, UV radiation (for above-ground sections near trench openings), and mechanical impact—tested to withstand 50J impact forces (per IEC 60811-1-1) without sheath damage. In terms of applications, the series is widely deployed in urban underground MV distribution networks, where it connects substations to residential and commercial areas while avoiding overhead cable clutter. NA2XSY and NA2XS2Y are staple choices for general urban and industrial trench installations, while NA2XS(F)2Y and NA2XS(FL)2Y are preferred for high-safety zones like airports, hospitals, and chemical industrial parks. Additionally, all models support renewable energy integration, such as connecting underground solar farm inverters to MV grids or powering underground wind farm auxiliary systems, where their water-blocking capability protects against groundwater in remote or coastal locations. Collectively, the NA2XSY, NA2XS2Y, NA2XS(F)2Y, and NA2XS(FL)2Y series fill a critical niche in underground MV power transmission, offering tailored solutions for diverse environmental and safety requirements. By combining aluminium’s cost-efficiency, robust water-blocking technology, and model-specific enhancements (double sheaths, flame retardancy, low smoke), these cables deliver reliable, long-lasting performance while addressing the unique challenges of underground power delivery.