ACSR-IEC61089
ACSR Aluminium Conductor Steel Reinforced to IEC 61089 / ASTM B232
Aluminium carries the current, the galvanised steel core carries the tension, and the span can be as long as you like.
ACSR splits the two jobs an overhead conductor has to do. The aluminium wires around the outside carry the current, because aluminium is the best conductor per kilogram available at the price. The galvanised steel wires at the centre carry almost all of the tension, because steel is three times stronger than 1350-O aluminium. That is the entire reason the composite conductor exists, and it is why a 300 m river crossing is strung with ACSR rather than with AAC.
The specification has to name the split, which is what the area notation does: 120/20 mm² means 120 mm² of aluminium over 20 mm² of steel. The aluminium sets the electrical performance; the steel sets the breaking load and the sag. Voltcore supplies ACSR to IEC 61089 and to ASTM B232, with the zinc coating on the core wires at Class A minimum and the breaking load tabulated per construction.
Specification
| Item | Value |
|---|---|
| Type | Concentric lay aluminium conductor with galvanised steel core |
| Aluminium | 1350-O, 61% IACS conductivity |
| Steel core | Galvanised steel wire, Class A zinc coating minimum, 1300 MPa grade |
| Area notation | Aluminium area / steel area in mm², for example 120/20 |
| Area range | 25/4 to 800/100 mm² |
| Resistivity at 20 °C | 28.264 nΩ·m for the aluminium component |
| Maximum operating temperature | +90 °C continuous, +120 °C short-term |
| Grease | Core grease available for corrosion protection |
| Standard | IEC 61089, ASTM B232 |
| Core construction | 1, 7, 19 or 37 steel wires depending on size |
| Lay | Concentric, aluminium layers laid converse to the layer beneath |
| Supply form | Wooden drums with steel-tyred flanges, lengths to 3500 m |
Layer-by-layer construction
Listed from the conductor outward. Read this alongside the specification table — the two together tell you whether the cable will survive its installation method.
- 1. Steel core1 to 7 galvanised steel wires, Class A zinc coating, 1300 MPa grade, the tension-carrying member
- 2. First aluminium layer6 aluminium wires laid over the steel core, 1350-O alloy
- 3. Outer aluminium layers12 to 24 further aluminium wires, lay direction reversed to the layer beneath
- 4. Lay and finishConcentric lay to IEC 61089, outer lay ratio 10 to 14, smooth surface with no crossed or broken wires
- 5. Corrosion protectionCore grease applied between the steel and the first aluminium layer where the atmosphere requires it
- 6. PackingContinuous length on a wooden drum with steel-tyred flanges, sealed and tagged with area, length and construction
Reference dimensions and weights
| Nominal area — Al/St (mm²) | Aluminium stranding (n×mm) | Steel stranding (n×mm) | Approx. overall diameter (mm) | Approx. mass (kg/km) | Rated breaking load (kN) | Max. DC resistance at 20 °C (Ω/km) |
|---|---|---|---|---|---|---|
| 25/4 | 6 × 2.30 | 1 × 2.30 | 6.9 | 101 | 8.9 | 1.13 |
| 35/6 | 6 × 2.72 | 1 × 2.72 | 8.2 | 143 | 12.9 | 0.808 |
| 50/8 | 6 × 3.25 | 1 × 3.25 | 9.8 | 200 | 17.4 | 0.566 |
| 70/12 | 26 × 1.85 | 7 × 1.44 | 11.7 | 283 | 25.4 | 0.404 |
| 95/15 | 26 × 2.15 | 7 × 1.67 | 13.6 | 375 | 33.1 | 0.298 |
| 120/20 | 26 × 2.42 | 7 × 1.88 | 15.3 | 474 | 42.0 | 0.236 |
| 150/25 | 26 × 2.70 | 7 × 2.10 | 17.1 | 592 | 52.5 | 0.189 |
| 185/30 | 26 × 3.00 | 7 × 2.34 | 19.0 | 731 | 65.0 | 0.153 |
| 240/40 | 26 × 3.42 | 7 × 2.66 | 21.7 | 948 | 84.0 | 0.118 |
Reference figures for preliminary sizing and drum planning. Overall diameter and weight vary with strand construction and sheath thickness tolerance; certified drawings are issued with each quotation.
Engineering characteristics
- The steel core carries the tension, so the aluminium is sized for current and the conductor is sized for the span.
- Breaking load tabulated per construction: 8.9 kN at 25/4 mm² rising to 84 kN at 240/40 mm².
- Galvanised steel wires at Class A zinc coating minimum, to the coating requirements of IEC 60888.
- Area notation on every drum tag, so the aluminium and steel content is visible before the price is agreed.
- Core grease available between the steel and the aluminium for coastal and industrial atmospheres.
- Resistance figures come from the aluminium area alone, which is what the drop calculation uses.
- Supplied to IEC 61089 and to ASTM B232, so either specification system can be met from one line.
Typical applications
- Transmission and sub-transmission lines on long spans
- River, valley and motorway crossings where sag is the governing limit
- Rural electrification trunk feeders with wide pole spacings
- Lines subject to heavy wind or ice loading
- Re-conductoring projects that need more tension capacity on the same towers
Ordering options
- 25/4 to 800/100 mm² constructions
- IEC 61089 or ASTM B232 designation on the drum tag
- Core grease for corrosive atmospheres
- Drum lengths to 3500 m, packed to a stringing schedule
- Higher zinc coating classes available on the steel core
Standards manufactured to
- IEC 61089
- ASTM B232
- IEC 60888
- IEC 61232
Manufactured to other standards on request. Send the standard number with your RFQ and we will quote against it rather than against a near-equivalent.
Price and availability for ACSR Aluminium Conductor Steel Reinforced
Include cross-section, core count, voltage grade, route length and installation method — those five determine price more than anything else on the page.
- Engineer-reviewed before pricing
- Reference drawings issued with the quotation
- Free sample up to free sample up to 5 m
ACSR Aluminium Conductor Steel Reinforced — frequently asked questions
Why choose ACSR over AAC or AAAC?
Tension. The galvanised steel core carries most of the mechanical load, so ACSR strings at a lower sag and over a longer span than either all-aluminium design at the same diameter. On a short distribution span that strength costs more than it is worth; on a 200 m span or a river crossing it is the difference between four towers and six.
What does 120/20 mean?
It is the area notation for the construction: 120 mm² of aluminium and 20 mm² of steel. The first number sets the electrical performance, because the aluminium carries virtually all the current. The second sets the breaking load, because the steel carries the tension. Always specify both, because 120/20 and 120/70 are different conductors with different spans.
How does the steel core affect the current rating?
Very little. At power frequency the current flows almost entirely in the aluminium; the steel core contributes a small amount of inductive and magnetic loss. So a 120/20 construction is rated essentially as a 120 mm² aluminium conductor, and the DC resistance table reflects that. Size the current on the aluminium area and the span on the breaking load.
What corrosion protection do you offer on the core?
The standard construction carries Class A zinc coating on the steel wires, which is adequate inland. For coastal or industrial routes Voltcore supplies a greased construction with the compound applied between the steel core and the first aluminium layer, and higher zinc coating classes on request. That is the difference between a 10-year and a 30-year core life in a marine atmosphere.