HTLS Conductor Manufacturer — High Temperature Low Sag
HTLS (High Temperature Low Sag) overhead conductors are designed to carry 1.5–2 times more current than conventional ACSR at operating temperatures up to 210 °C, with reduced sag at high temperatures.
We manufacture ACCC, ACCR, TACSR, and GAP-type conductors per IEC 61089, ASTM B232, and EN 50182, for transmission line uprates and new high-capacity lines.
What Is an HTLS Conductor?
HTLS (High Temperature Low Sag) conductors are overhead power lines designed to operate at higher temperatures (up to 150–250 °C) with less thermal sag than conventional ACSR. They are primarily used to uprate existing transmission lines — replacing ACSR on the same towers without rebuilding corridors — and for new high-capacity lines.
We manufacture the main HTLS conductor families
- ACSS / ACSS/TW (Aluminum Conductor Steel-Supported) — annealed aluminum over galvanized steel, operates to 200 °C
- TACSR / G(Z)TACSR (Thermal Aluminum Conductor Steel-Reinforced) — heat-resistant aluminum alloy over steel or invar core, operates to 150–210 °C
- ACCC / ACCC/TW (Aluminum Conductor Composite Core) — carbon-fiber composite core, operates to 200 °C, highest ampacity per diameter
- ACCR (Aluminum Conductor Composite Reinforced) — aluminum-zirconium over aluminum-steel composite core, operates to 210 °C
Key Advantages of HTLS Conductors
- Low sag at high temperatures — the core (invar, carbon composite, or steel) maintains mechanical strength at operating temperatures where ACSR would sag excessively
HTLS Conductor Specification & Technical Parameters
The HTLS cables produced by the ZMS manufacturer offer a wide range of advantages across a wide range of options. Today’s increased demand for electricity, the increasing difficulty of erecting the line corridors required for new overhead lines, and the rapid rise of renewable energy generation. There is an urgent need for transmission upgrades and transmission expansion.
High-temperature low sag conductors (HTLS conductors) are a new technology for upgrading transmission lines to increase the thermal rating to improve transmission capacity. HTLS conductors can operate at high temperatures (100 °C and above) for extended periods without significant deterioration in tensile strength or other mechanical, electrical, or chemical properties. The tensile length at the same temperature is significantly lower than that of conventional aluminum or steel core aluminum conductors.
Characteristics of HTLS Core Materials
1. ACSS / ACSS/TW (Aluminum Conductor Steel-Supported / Trapezoidal Wire) — Annealed (soft) aluminum strands over a conventional galvanized steel core. ACSS/TW uses trapezoidal-shaped aluminum wires for a compact, larger aluminum cross-section. Continuous operating temperature: 200 °C; short-time: 250 °C.
2. G(Z)TACSR (Gap-type Thermally-Resistant Aluminum Alloy Conductor Steel-Reinforced) — Heat-resistant aluminum alloy strands with a gap around the galvanized steel core. The gap allows the core to carry most of the tensile load at high temperatures. Continuous operating temperature: 150 °C; short-time: 180 °C.
3. Invar Conductor (ZTACSR) (Extra-Heat-Resistant Aluminum Conductor Invar Steel-Reinforced) — Extra-heat-resistant aluminum alloy over an invar (low-expansion nickel-steel) core. The invar core minimizes thermal sag. Continuous operating temperature: 210 °C; short-time: 240 °C.
4. ACCR (Aluminum Conductor Composite Reinforced) — Aluminum-zirconium strands over an aluminum-steel composite core. Lightweight core with high strength and low thermal expansion. Continuous operating temperature: 210 °C; short-time: 240 °C.
5. ACCC / ACCC/TW (Aluminum Conductor Composite Core) — Annealed aluminum strands over a carbon-fiber composite core. Highest ampacity per unit diameter; ACCC/TW uses trapezoidal aluminum for even more aluminum area. Continuous operating temperature: 180 °C; short-time: 200 °C.
Core Material | Min Tensile Strength (MPa) | Modulus of Elasticity (GPa) | Min Elongation (%) | Coeff. of Linear Expansion (10⁻⁶/°C) | Continuous Temp (°C) | Short-time Temp (°C) |
|---|---|---|---|---|---|---|
Galvanized Steel (Class A) | 1379–1448 | 206 | 3.0–4.0 | 11.5 | 180 | 200 |
Zn-5Al-MM Steel (B802) | 1379–1448 | 206 | 3.0–4.0 | 11.5 | 250 | 350 |
High-Strength Galvanized Steel (B606) | 1517–1620 | 206 | 3.0–3.5 | 11.5 | 180 | 200 |
Zn-5Al-MM Steel (B803) | 1517–1620 | 206 | 3.0–3.5 | 11.5 | 250 | 350 |
Ultra-High Strength Galvanized Steel | 1827–1965 | 206 | 3–3.5 | 11.5 | 180 | 200 |
Zn-5Al-MM Ultra High Strength Steel | 1827–1965 | 206 | 3–3.5 | 11.5 | 250 | 300 |
ACCC/TW Carbon Composite Core | 2137–2482 | 114 | 2.0 | 1.6 | 180 | 200 |
ACCR Composite Core | 1379 | 220 | 0.64 | 6.0 | 210 | 240 |
Aluminum-Clad Steel (ACS, 20.3% IACS) | 1034–1344 | 162 | 3.0 | 13.0 | 150 | 200 |
Aluminum-Clad Invar (14% IACS) | 1207–1276 | 152 | 3.0 | 3.7 | 210 | 240 |
Types of HTLS Conductor
ACSS / ACSS/TW — Aluminum Conductor Steel-Supported
ACSS uses fully annealed (1350-0) aluminum strands over a galvanized or Galfan (Zn-5% Al) steel core. Because the aluminum is fully annealed, ACSS operates at high temperatures with the same sag as ACSR at normal temperatures. ACSS/TW uses trapezoidal-shaped aluminum wires for a more compact cross-section and 10–15% more aluminum area. Continuous rating: 200 °C; short-time: 250 °C. Suitable for line uprating where existing towers can accept moderate additional load.
ACCC / ACCC/TW — Aluminum Conductor Composite Core
ACCC uses annealed aluminum strands over a carbon-fiber/glass-fiber composite core. The core has 1/5 the thermal expansion of steel and half the weight, enabling 1.5–2× the ampacity of ACSR on the same tower. The glass-fiber outer layer prevents galvanic corrosion between the carbon core and aluminum strands. ACCC/TW increases aluminum area by ~30% versus equivalent-diameter ACSR. Continuous rating: 180 °C; short-time: 200 °C. Best for maximum uprating on existing corridors.
ACCR — Aluminum Conductor Composite Reinforced
ACCR uses AT3 aluminum-zirconium strands over an Al2O3 ceramic particle-reinforced aluminum matrix core. The core has steel-like strength at near-aluminum weight, with half the thermal expansion of steel. Continuous rating: 210 °C; short-time: 240 °C. Suited for heavy-ice areas where high-temperature sag must be minimized without tower upgrades.
G(Z)TACSR — Gap-type TACSR
A gap between the galvanized steel core and the heat-resistant aluminum-zirconium alloy strands allows the steel core to carry full tension at high temperatures. The gap design eliminates aluminum core compression at high temperatures. Continuous rating: 150 °C; short-time: 180 °C. Note: gap-type conductors require factory-assembled terminations — we supply pre-fitted joints and dead-ends to simplify installation.
HTLS Conductor Size Range
We manufacture HTLS conductors across the following size range, with standard stranding designs per IEC 61089 and ASTM B232. Custom sizes and stranding configurations are available on request.
HTLS Type | Aluminum Area Range | Equivalent ACSR | Core Option |
|---|---|---|---|
ACSS / ACSS/TW | 100–900 mm² | Dog to Bison | Galvanized / Galfan |
TACSR / G(Z)TACSR | 100–800 mm² | Dog to Rail | Steel / Galfan |
ZTACSR (Invar) | 150–700 mm² | Panther to Zebra | Invar steel |
ACCC / ACCC/TW | 100–1000 mm² | Dog to Overhead | Carbon composite |
ACCR | 150–800 mm² | Panther to Bison | Aluminum-steel composite |
HTLS Conductor Current Carrying Capacity
HTLS conductors carry significantly more current than conventional ACSR of the same diameter because they operate at higher temperatures. The table below compares typical current carrying capacity for equivalent outer diameters at 20 °C ambient, 40 °C maximum conductor temperature rise (per IEC 61089 / IEEE 738).
Equivalent ACSR size | ACSR ampacity (A) | ACCC ampacity (A) | Increase |
|---|---|---|---|
ACSR Dog (4/0) | ~320 | ~580 | +81% |
ACSR Panther (550 kcmil) | ~420 | ~780 | +86% |
ACSR Zebra (795 kcmil) | ~520 | ~950 | +83% |
ACSR Bison (1590 kcmil) | ~750 | ~1,350 | +80% |
Reference values for free-air installation, 20 °C ambient. Actual current carrying capacity depends on span, height, wind speed, solar radiation, and allowable conductor temperature. Contact us for a project-specific ampacity calculation.
Traditional ACSR vs. ACCC HTLS Conductor — Key Differences
Comparison Item | Traditional ACSR | HTLS (ACCC) |
|---|---|---|
Continuous operating temperature | 75–90 °C | 180 °C (short-time 200 °C) |
Ampacity (same diameter) | Baseline | 1.5–2× (+50–100%) |
Thermal expansion coefficient | ~11.5 × 10⁻⁶/°C | ~1.6 × 10⁻⁶/°C (1/7 of ACSR) |
Sag at high temperature | Significant sag as temperature rises | Minimal sag even at 180 °C |
Weight (same ampacity) | Heavier (larger diameter needed) | ~25–40% lighter |
Core material | Galvanized steel | Carbon-fiber composite |
Upfront cost per meter | Lower | Higher (~2–3×) |
Best application | New lines with standard loading | Line uprating on existing towers, limited corridors |
HTLS Conductor Manufacturing
Our factory manufactures HTLS conductors on tubular stranding and closure lines, with in-process testing for conductor resistance, dimensional checks, and tensile testing on every batch. We supply ACSS, ACCC/TW, ACCR, and G(Z)TACSR conductors to utilities and EPC contractors in over 30 countries.
Tell us your project requirements and we will recommend the right conductor:
- Conductor type (ACSS, ACCC, ACCR, TACSR — or let us recommend)
- Nominal area / equivalent ACSR size
- Core material requirement (galvanized steel, Galfan, invar, composite)
- Maximum continuous operating temperature
- Installation span, ice and wind loading conditions
Manufactured per IEC 61089, ASTM B232, and BS 215. Quality system certified ISO 9001:2015 and ISO 14001:2015. Mill test certificates supplied with every shipment.