Low voltage overhead lines

Aerial bundled cable in Old Coulsdon, Surrey

Low voltage overhead lines may use either bare conductors carried on glass or ceramic insulators or an aerial bundled cable system. The number of conductors may be anywhere between four (three phase plus a combined earth/neutral conductor - a TN-C earthing system) up to as many as six (three phase conductors, separate neutral and earth plus street lighting supplied by a common switch).

Overhead lines or overhead wires are used to transmit electrical energy to trams, trolleybuses or trains. Overhead line is designed on the principle of one or more overhead wires situated over rail tracks. Feeder stations at regular intervals along the overhead line supply power from the high-voltage grid. For some cases low-frequency AC is used, and distributed by a special traction current network.

Вправа 3. Дайте відповіді на питання.

1. What is an overhead power line?

2. What does it consist of?

3. Of what are towers for support of the lines made?

4. Of what are the bare wire conductors on the line made?

5. How overhead power transmission lines are classified?

6. What do you know about the structure of overhead power lines?

7. What is the grounded cable?

8. What do you know about compact transmission lines?

9. How can we use low voltage overhead lines?

10. How are they designed?

Вправа 4. Перекладіть речення українською.

1. Overhead lines are also occasionally used to supply transmitting antennas, especially for efficient transmission of long, medium and short waves.

2. For this purpose a staggered array line is often used.

3. Along a staggered array line the conductor cables for the supply of the earth net of the transmitting antenna are attached on the exterior of a ring, while the conductor inside the ring, is fastened to insulators leading to the high-voltage standing feeder of the antenna.

4. Use of the area below an overhead line is restricted because objects must not come too close to the energized conductors.

5. Overhead lines and structures may shed ice, creating a hazard.

6. Radio reception can be impaired under a power line, due both to shielding of a receiver antenna by the overhead conductors, and by partial discharge at insulators and sharp points of the conductors which creates radio noise.

7. Construction of overhead power lines, especially in wilderness areas, may have significant environmental effects.

8. Environmental studies for such projects may consider the effect of bush clearing, changed migration routes for migratory animals, possible access by predators and humans along transmission corridors, disturbances of fish habitat at stream crossings, and other effects.