ACCC (Aluminium Conductor Composite Core)

The CTC Global ACCC conductor utilizes a hybrid carbon and glass fiber core embedded in a high-performance thermoset epoxy matrix. The central carbon fiber core consists of tens of thousands of high-strength, high-modulus unidirectional carbon fibers that are surrounded by a protective layer of glass fibers. The outer glass fibers improve toughness and flexibility while also providing a galvanic barrier to prevent corrosion with the conductive aluminum strands.

The ACCC Conductor hybrid core is not only twice as strong as steel, it is also 70% lighter.

The lighter weight of the ACCC allows to utilize about 28% more aluminum without a weight or diameter penalty. The compact trapezoidal strands and smooth surface composite core work in unison to dissipate wind-induced vibration. From one side the aluminum strands are fully annealed, offering the highest degree of conductivity for any aluminum available today, from the other side the composite core offers a coefficient of thermal expansion about ten times less than steel.
The low coefficient of thermal expansion mitigates conductor sag under heavy electrical load conditions. 

Sag / temperature comparison of several conductors

Figure: Sag / temperature comparison of several conductors tested by Ontario Hydro at Kinectrics lab

The composite core is fully elastic and will not plastically deform and its elastic modulus is lower than that of steel. The lower modulus allows the ACCC conductor to stretch degree during extreme ice and wind loading events. However, when the event subsides, the composite core fully returns to its pre-stressed condition allowing the aluminum strands to subsequently relax.
This type of event further improves the ACCC conductor’s self-damping characteristics and reduces the conductor’s thermal knee-point to further reduce conductor sag under heavy electrical load conditions.