The Aluminium Conductor Steel Supported (ACSS) represents a category of High-Temperature-Low-Sag (HTLS) conductors,  offering distinct advantages over conventional ACSR conductors. ACSS conductors feature the incorporation of 1350-O annealed  aluminium wires in contrast to 1350-H19 variant used in ACSR conductors. This substitution results in noteworthy enhancements.  Notably, annealed aluminium wires boast a higher electrical conductivity of 63% IACS, compared to the 61.2% IACS conductivity of  drawn, hardened aluminium wires utilized in ACSR conductors. Consequently, ACSS conductors are capable of carrying increased  electrical current. 

A key distinction lies in the operational temperature range. While ACSR conductors are suitable for operation at 70 °C, ACSS  conductors excel by achieving elevated operating temperatures of up to 210 °C, courtesy of the annealed wires. This heightened  temperature tolerance significantly augments the electrical current carrying capacity by up to 200%. An additional benefit emerges under high temperature conditions (above 75 °C). In ACSR conductors, the ultimate tensile strength  (UTS) experiences a decline under high operating temperatures. However, ACSS conductors, utilizing annealed aluminium wires,  maintain a consistent UTS at elevated temperatures, enabling effective operation. 

To enhance the tensile strength of ACSS conductors, high-strength steel cores are employed, available in galvanized, GalfanCoated, or aluminium-clad types. The utilization of aluminium-clad steel cores offers substantial advantages, including a significant  reduction in wire corrosion, extension of wire lifespan, and a decrease in electrical resistance. Notably, the preference leans  towards the use of aluminium-clad or Galfan-Coated steel wires over galvanized steel wires due to their heightened thermal  resistance properties.

ACSS conductors offer the following benefits:

► Elevated electrical conductivity

► Appropriate self-damping 

► Abundant electrical current transmission capability 

► Robust resistance to vibrational fatigue

While conventional ACSR conductors employ circular aluminium strands, the utilization of trapezoidal-shaped strands offers two  primary advantages:

1- Enhanced Current Transmission and Reduced Energy Loss:

In comparison to conductors with circular aluminium strands of the same diameter, those equipped with trapezoidal aluminium  strands boast a larger cross-sectional area. This unique property translates to an increased capacity for current transmission or,  conversely, a reduction in energy loss. Additionally, the adoption of trapezoidal aluminium strands leads to a notable decrease of  around 10% to 15% in electrical resistance of the conductor.

2- Compact Design and Reduced Diameter:

When considering conductors with an equivalent cross-sectional area, the incorporation of trapezoidal aluminium wires results in a  more compact conductor configuration. Consequently, the overall diameter of ACSS/TW (Aluminium Conductor Steel Supported/ Trapezoidal Wires) conductors is notably smaller—approximately 10% to 15%—compared to conductors utilizing circular aluminium  wires. This reduction in diameter yields several benefits: mitigated effects of ice and snow mass, diminished aerodynamic forces  acting on the conductor, decreased conductor sag, reduced tower weight, and the potential for longer span lengths. These  combined advantages contribute to cost savings in the line’s construction and maintenance.

Furthermore, the compact arrangement of trapezoidal aluminium wires results in minimal gaps between strands and layers.  This compactness serves to limit the ingress of dust, aerosols, and other foreign particles into the conductor. This reduction in  penetration helps extend the conductor’s lifespan and contributes to its overall durability.