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ACCC conductor

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Aluminium Conductor Composite Core or ACCC is a type of "high-temperature low-sag" (HTLS) overhead power line conductor manufactured by more than 20 international conductor manufacturers. CTC Global (formerly Composite Technology Corporation) developed the technology.

It is able to carry approximately twice as much current as a conventional aluminium-conductor steel-reinforced cable (ACSR) cable of the same size and weight, making it popular for retrofitting an existing electric power transmission line without needing to change the existing towers and insulators.

In addition to the labor and materials savings, such an upgrade can be performed as a "maintenance and repair" operation, without the lengthy permitting process required for new construction.

It does this by replacing the steel core in ACSR cable with a carbon and glass fiber strength member formed by pulltrusion. This composite strength member provides several advantages:

  • It is lighter. The weight saved can be used for more aluminium conductor. ACCC cable uses trapezoidal strands to fit more aluminium into the same cable diameter.
  • Softer, fully annealed aluminium can be used for the conductors. ACSR cable uses harder aluminium which contributes to the cable's tensile strength, but has about 3% less electrical conductivity.
  • It has a much lower coefficient of thermal expansion (CTE) (6991583622104687215♠1.6 ppm/°C) than ACSR (6992423126025898230♠11.6 ppm/°C). This lets the cable be operated at a significantly higher temperature without excessive sag between poles.

    • The first two factors result in roughly 30% greater conductivity than an equivalent ACSR conductor, allowing 14% more current to be carried at equal temperature. For example, 1.107 in (28.1 mm) diameter ACCC "Drake" conductor at 75 °C has an AC resistance of 106 mΩ/mile, while equivalent ACSR conductor has an AC resistance of 139 mΩ/mile, 31% higher.

    The remaining capacity increase is provided by an increased operating temperature of 180 °C (356 °F) continuous and 200 °C (392 °F) emergency, compared to 75 °C (167 °F) continuous and 100 °C (212 °F) emergency for ACSR.

    (The manufacturers rate the cable for continuous operation at 180 °C surface temperature, Operation at these temperatures implies high line losses, which may be uneconomical, but the ability to carry such current contributes to the redundancy of the electric grid (the high overload capacity can stop a potential cascading failure) and thus can be valuable even when rarely used directly. Even at higher operating temperatures, the ACCC conductor's added aluminum content and lower electrical resistance offers reduced line losses compared to other conductors of the same diameter and weight.

    Disadvantages

  • The primary disadvantage is cost; ACCC costs 2.5–3 time as much as ACSR cable.
  • Although ACCC has significantly less thermal sag than even other HTLS conductor designs, its core is quite elastic and sags more than other designs under ice load, although a ULS (higher modulus)version is available at a cost premium.
  • The conductor has a larger minimum bend radius, requiring extra care during installation.
  • The conductor requires special fittings, such as splice and dead-end connections.

    • References

    ACCC conductor Wikipedia
    (Text) CC BY-SA