Air cable

An aerial cable or air cable is an insulated cable usually containing all conductors required for an electrical transmission system or a telecommunication line, which is suspended between utility poles or electricity pylons. As aerial cables are completely insulated there is no danger of electric shock when touching them and there is no requirement for mounting them with insulators on pylons and poles. A further advantage is they require less right of way than overhead lines for the same reason. 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 aerial 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.

Aerial cables are mostly used for telecommunication systems or for power transmissions with voltages below 1000 volts. Aerial 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 aerial 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 aerial 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 power lines the aerial 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 En BW) in Germany until the mid-1980s, where the aerial cable was installed like a garland on the ground conductor or an auxiliary rope.

For reasons of electromagnetic interference aerial cables running along power lines are most often of fibre optic types. As these are dielectric, it is even possible to install them directly in the conductors—see optical ground wire.

Aerial cables are also used sometimes for power transmission from the transmitter building to the antenna at radio stations.

Заняття 57

Тема: Заземлення і заземлювальні пристрої

Технічні скорочення та одиниці вимірювання

Вправа 1. Прочитайте та перекладіть слова за допомогою словника.

groundbed [groundbed]

install [ɪnˈstɔːl]

provide [ prəˈvaɪd]

ground rod [ ɡraʊnd rɒd]

bond [bɒnd]

bare copper wire [beə ˈkɒpə ˈwaɪə]

path [pɑːθ]

retain [rɪˈteɪn]

swell [swel]

sheathed type [ʃiːðd taɪp]

requirement [rɪˈkwaɪəmənt]

Вправа 2. Прочитайте та перекладіть текст.