Standard Specification for Thermal-Resistant Aluminum-Alloy Conductors, Steel Core Reinforced for Overhead Transmission Line (TACSR & TACSR/AW) — high-ampacity overhead transmission conductors that operate continuously at up to 150 °C, combining heat-resistant aluminum-zirconium alloy outer strands with a galvanized steel or aluminum-clad steel core for capacity upgrades and long-span transmission lines.
NB/T 42060 defines the product designation, technical requirements, test methods, packaging and marking of concentric-lay-stranded conductors in which a galvanized steel or aluminum-clad steel core is reinforced with thermal-resistant aluminum-zirconium alloy (TAL) outer strands. Two product families are covered: TACSR (thermal-resistant aluminum alloy conductor, steel reinforced) with a galvanized steel core, and TACSR/AW with an aluminum-clad steel core for enhanced corrosion resistance.
The distinguishing characteristic is the use of zirconium-doped aluminum alloy wires that retain their mechanical and electrical properties at sustained operating temperatures up to 150 °C — well above the 70–90 °C limit of conventional EC-grade aluminum. This enables TACSR conductors to carry substantially higher current in the same physical envelope, making them the preferred solution for capacity upgrades of existing transmission corridors, UHV and EHV backbone lines, long-span crossings, and projects where new right-of-way approval is infeasible.
NB/T 42060 conductors are concentric-lay-stranded composite conductors with a central reinforcing steel (or aluminum-clad steel) core surrounded by one or more concentric layers of hard-drawn thermal-resistant aluminum-alloy wires. The core carries the mechanical tension; the outer alloy strands carry the majority of the electrical current and deliver the elevated-temperature performance.
Hard-drawn aluminum-zirconium alloy wires per GB/T 30551-2014. Two grades are specified: NRLH1 (standard thermal-resistant, min. conductivity 60% IACS) and NRLH2 (high-strength thermal-resistant, min. conductivity 57% IACS). Both rated for 150 °C continuous operation.
Five tensile-strength grades per GB/T 3428-2012: G1A (standard), G2A, G3A, G4A, G5A (up to 1,830 MPa). Zn-5% Al-MM or 55% Al-Zn alloy coatings are permitted as alternatives to pure zinc for aggressive environments, subject to order agreement.
Bimetallic core wires per GB/T 17937-2009: LB14 (14% IACS) and LB20A (20.3% IACS). Continuously bonded aluminum cladding delivers superior corrosion resistance over galvanized steel in coastal, industrial, and high-pollution environments.
Typical configurations include 6+1, 7+7, 18+1, 24+7, 26+7, 30+7, 45+7, 48+7, 54+7, and 54+19. Model designation follows J[alloy code]/[core code], e.g. JNRLH1/G1A for standard TAL + G1A steel, JNRLH2/LB20A for high-strength TAL + 20.3% IACS Al-clad steel.
Representative sizes for standard-grade TACSR using NRLH1 thermal-resistant aluminum alloy and G1A galvanized steel core. Rated breaking strength (RBS) shown is for the G1A configuration; higher values are obtained by specifying G2A–G5A steel grades. DC resistance corrected to 20 °C.
| Nominal Area (mm²) | No. of Wires (TAL/St) | Wire Dia. TAL/St (mm) | OD (mm) | Mass (kg/km) | RBS (kN) | DC Resist. (Ω/km @ 20 °C) |
|---|---|---|---|---|---|---|
| 150/20 | 24 / 7 | 2.78 / 1.85 | 16.70 | 549.0 | 46.20 | 0.2014 |
| 185/30 | 26 / 7 | 2.98 / 2.32 | 18.97 | 732.0 | 63.11 | 0.1619 |
| 240/30 | 24 / 7 | 3.60 / 2.40 | 21.69 | 921.5 | 75.68 | 0.1201 |
| 300/40 | 24 / 7 | 3.99 / 2.66 | 23.91 | 1,132.0 | 92.06 | 0.0977 |
| 400/35 | 48 / 7 | 3.22 / 2.50 | 26.81 | 1,348.7 | 102.5 | 0.0752 |
| 400/65 | 26 / 7 | 4.42 / 3.44 | 28.00 | 1,610.0 | 135.0 | 0.0736 |
| 400/95 | 30 / 19 | 4.16 / 2.50 | 29.10 | 1,857.9 | 171.2 | 0.0726 |
NB/T 42060 specifies type tests, sample tests, and routine tests covering both the individual component wires (per their respective single-wire standards) and the completed stranded conductor:
TACSR and TACSR/AW conductors per NB/T 42060 are the workhorse high-temperature low-sag (HTLS) option deployed extensively across China's 110 kV, 220 kV, 330 kV, 500 kV, 750 kV, and ±800 kV to ±1,100 kV UHV transmission networks. Where new transmission corridors are difficult to approve because of land-use, environmental, or permitting constraints, utilities re-conductor existing lines with TACSR to approximately double ampacity without rebuilding towers or foundations. The zirconium-stabilised aluminum alloy withstands sustained operation at 150 °C with minimal annealing, making TACSR especially well-suited to long-span river and valley crossings, lines exposed to heavy ice loading, and heavily loaded metropolitan backbone circuits. The TACSR/AW variant further extends service life in coastal, tropical, and industrially polluted environments where galvanized steel would be susceptible to corrosion over decadal asset lifetimes.
Official Standards & References
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