CC, CCT, Covered Conductor
Weatherproof (covered) line wire has been in use for many decades to provide weather ability to overhead conductors. The coverings helped to reduce outages due to the storms and wind, where objects might contact the lines or the lines would come in contact with each other .
Aerial spacer cables utilize a thicker covering than weatherproof wire. These covering thicknesses and the abrasion resistant outer layer provide a greater protection against faults due to incidental (or even sustained), contact by trees or other conductors. The dual-layer construction virtually eliminates the possibility of pinholes through the entire covering wall, minimizing the probability of a fault if contacted by a grounded object.