Air cable redirects here. Distinguish from usage in subscription television services.
An air cable is an insulated cable usually containing all conductors required for an electrical transmission system or a telecommunication line, which is spun between utility poles or pylons. As air cables are completely insulated there is no danger of electrical shocks when touching them and there is no requirement for mounting them with insulators on pylons and poles. A further advantage of air cables is, that they require less right of way than overhead lines for the same purpose. They can be designed as shielded cables for telecommunication purposes. If the cable falls, it may still operate if its insulation is not damaged.
As air cables are installed on pylons or poles, they may be cheaper to install than underground cables as no work for digging is required, which can be very expensive in rocky areas.
Use
Air cables are mostly used for telecommunication systems or for power transmissions with voltages below 1000 volts. Air cable for voltages around 10000 volts have also been built, for the supply of farms, waterworks, transmitters and other facilities outside urban areas. A further common use is the replacement of overhead telecommunication lines, for example, along railway line, by air cables as they can be installed on existing poles and make the facility more reliable.
Telecommunication systems running along power lines or aerial tramways are often built as air cables as they can be easily installed on the pylons or tramway support towers. However these cables must be designed for higher forces as span lengths are longer.
As powerlines the air cable can serve also as ground conductor on the top of the pylon. It can be also installed in form of a separate strand on the conductor. A special method was used at former EVS ( now EnBW)in Germany until the mid 1980s, where the air cable was installed like a garland on the ground conductor or an auxiliary rope.
Air cable spun like a garland on a 110kV-powerline of EnBW AG near Leonberg in Germany
For reasons of electromagnetic interference air cables running along powerlines are most often of fibreoptic types. As these are dielectric, it is even possible to install them directly in the conductors.
Air cables are also used sometimes for power transmission from the transmitter building to the antenna at radio stations.
See also
overhead powerline
Categories: Power cables | Electricity distribution
