Les lignes aériennes sont soutenues par des sections de pylônes de transmission.
Des pylônes électriques sont utilisés pour les lignes à plus haute tension.
Et les poteaux en bois ou en béton sont généralement utilisés pour les lignes à faible tension..
En effet, les lignes à tension plus élevée (ligne de tension la plus élevée) doit être installé à une grande hauteur, car ils nécessitent une plus grande distance de sécurité.
Seuls les pylônes électriques peuvent permettre de transporter des lignes de plusieurs dizaines de tonnes.
What you see along the road on the suburbs are usually transmission towers.
As for the types of towers, there are cat-head towers, wine-glass towers, gate-shaped towers, V-shaped towers, etc.
Voltage on overhead transmission lines
Rated voltage refers to the voltage between any two of the three ABC phases.
The standard domestic voltage of 220 volts is the voltage between any of the three phases to ground.
In reality, the line that transmits electricity to the house is 380 volts.
And the three phases are separated before entering the house.
Par exemple, each of the three ABC phases is connected to each of the units in a building.
Overhead ground lines
Transmission lines are also divided into direct current and alternating current (DC and AC).
Un AC circuit is composed of phases A, B and C.
The top of the transmission tower is the lightning line, also called overhead ground wire.
Lines located in areas with many storms or high voltage have two lightning lines.
Lines with fewer storms or low voltage may use only one lightning line.
Lightning lines are connected to poles to direct the lightning current to the ground.
Overhead transmission lines
Below the lightning lines are the transmission lines.
The number of wires are all multiples of 3. The single-circuit line contains 3 fils, the two-circuit line contains 6 fils, and the four-circuit line contains 12 fils.
In each circuit there are three wires for each of the three phases A, B and C.
The reason why there are several circuits in a tower is mainly due to the consideration of transmission capacity and footprint. This is why the concepts of “line length” et “circuit length” have also been developed.
For two-circuit lines, the circuit length is twice the line length and so on.
In the case of different voltage levels, the voltage of the upper conductor is higher than that of the lower conductor.
This is because the higher the voltage, the greater the required safety distance to ground.
Lightning lines are well distinguished from transmission lines.
The former is directly on top of the tower, while the latter must be suspended from the tower by insulators.
If there are no insulators, the conductor is shorted directly to the tower.
The insulator is an accessory for overhead wires (alambres aéreos) used to support and secure the conductor.
It can ensure proper distance and insulation between conductors or between conductors and ground.
Insulators should have sufficient electrical insulation strength and moisture resistance.
We hope this article will help you to understand overhead line and electric tower properly.
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