The requirement for the height of the transmission line is fundamentally the wire, which is to ensure that the wire has a sufficient safety distance from the ground or the crossing. Of course, it can also be said that there is an indirect requirement on the height of the tower, because the final height of the wire is basically, or most of it, provided (or determined) by the height of the tower.
The specific height requirements are mainly determined by the following factors:
1. Line voltage level: The minimum distance to ensure safety is also called electrical clearance. It is a circle drawn on the cross-sectional diagram, so it is also called clearance circle. The higher the voltage level, the greater the distance.
2. For different types of land or intersecting objects, in addition to the requirements of Article 1 above, a certain safety margin is added: for example, the same is the same land, the requirements for cultivated land and inaccessible land in mountainous areas are different, and crops should be considered for cultivated land , Personnel agricultural machinery activity height. Another example is the same river. In addition to the highest flood level once in 50 years, the navigable river also needs to add the highest mast height of the ship. Electrified railways have different requirements from ordinary railways. When crossing forest areas and trees, different tree species have different height requirements, which should be considered according to their respective limit heights.
3. The strength of the wire. The tension, or stress, of the wire determines the sag of the wire (the sag determines the position and height of the lowest point of the wire). The maximum service stress of the conductor is 40% of the ultimate stress of the conductor (the regulations stipulate that the safety factor of the conductor is not less than 2.5), the strength of the conductor is high, the stress of the conductor is high, and the sag of the conductor is small, because it can be approximately considered in engineering calculations, Wire sag is inversely proportional to the square of the stress. The sag of the wire is small, and the height of the tower can be reduced.
4. There are other effects: such as air temperature, air pollution degree (pollution level), and altitude have an effect on the length of the insulator, and its length also has an effect on the height of the tower, and so on.
