ACCC conductor

ACCC (Aluminum Conductor Composite Core) is a registered trade mark for a type of "high-temperature low-sag" (HTLS) overhead power line conductor manufactured by 34 international (and authorized) conductor manufacturers.
Invention.
CTC Global (formerly Composite Technology Corporation) developed the patented technology. The ACCC conductor's composite core is manufactured according to ASTM B987 / B987M - 20 “Standard Specification for Carbon Fiber Thermoset Polymer Matrix Composite Core (CFC) for use in Overhead Electrical Conductors.” CTC Global manufactures ACCC core in the US and with partners in China and Indonesia. Finished ACCC conductor is produced by 34 conductor manufacturers worldwide under license. As of May 2021, the ACCC Condutcor has been selected by over 250 utilities in 60 countries for more than 1,000 projects ranging from 11kV (AC) to 1,100kV (DC). 
Advantages.
It is able to carry approximately twice as much current as a traditional 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:
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, 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 continuous and emergency, compared to continuous and 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.