In the power system, the exposed transmission lines regard the wind as a big “natural enemy”. In order to resist the strong wind, the designers fully armed the line to form a fine wind-resistant design.
What threats do strong winds pose to transmission lines?
1. Wind deflection tripping is the most common type of wind damage on transmission lines, which mainly refers to discharge tripping due to insufficient electrical clearance distance after the conductor deflects under the action of wind.
2. Under the action of the breeze, the fittings wear and tear, and under the action of the strong wind, the insulator fittings string bears a load exceeding the design allowable value, and there are failures such as breakage and string drop.
3. Under the action of breeze vibration and strong wind, the ground wire will cause fatigue damage, strand and wire breakage due to excessive tension, or flashover discharge will burn the ground wire.
4. The strong wind load exceeds the maximum load that the tower can bear, resulting in damage to the tower components, which in turn causes the tower head to break or the whole tower to fall. This kind of failure is the most serious disaster caused by the strong wind.
How to prevent the wind destruction?
1. Reasonably determine the design wind speed:
It is the basic condition to ensure the wind resistance capacity of transmission lines. When designing a new transmission line, the meteorological data of the area passing by the line should be collected, combined with the wind area map and operation experience, and the design wind speed should be reasonably determined according to the design recurrence period.
2. The suspensionstring of the straight tower adopts V-shaped strings:
The V-shaped insulator string and the cross arm of the iron tower form a fixed triangular plane to fix the wires, which can avoid the flashover tripping fault caused by the wind deflection swing of the I-type insulator string.
3. Reinforced Windproof Composite Insulators for Tension Towers:
The windproof fixed composite insulators changes the installation method of traditional products from “hinge type” to “cantilever type”, from swing to hard support, and changes the jumper string from dynamic to static, thus effectively limiting the swing of the jumper. Thus ensuring the electrical clearance of the jumper to the tower body.
4. Using low wind pressure wire:
When the low wind pressure conductor is within the wind speed range of 30~60m/s, its drag coefficient and wind pressure can be reduced to less than 70% of that of ordinary conductors, which can significantly reduce the tower load and reduce the wind deflection angle of the conductor.
5. Install anti-vibration damperto prevent vibration of ground wire:
When the overhead wire is subjected to a wind speed of 0.5~10 m/s and a stable horizontal uniform wind force, an airflow vortex that alternates up and down will be generated on the back of the wire, so that the wire is subjected to a force that alternates up and down. When the pulse force When the frequency is equal to the natural frequency of the conductor, a regular up and down wave-like reciprocating motion is formed, which is breeze vibration. Under the action of continuous breeze vibration, vibration fatigue damage occurred on ground wires, insulator fittings strings, etc. The anti-vibration damper can absorb the vibration energy of the ground wire and reduce the vibration intensity.
