At present, ADSS optical cables in power systems are basically erected on the same tower as 110kV and 220kV transmission lines. ADSS optical cables are quick and convenient to install, and have been widely promoted. However, at the same time, many potential problems have also arisen. Today, let’s analyze what problems should be paid attention to when ADSS optical cables are added to high-voltage transmission line poles/towers?
For various pole/tower hanging points, the following factors should be considered:
1. The field strength of the hanging point should not be greater than 20kV/cm to reduce electrical corrosion and maintain the expected life of the optical cable.
2. Use low suspension as much as possible to reduce the additional bending moment of the pole and tower, reduce the amount of reinforcement and reinforcement of the pole and tower, and save project investment.
3. Try to avoid the cross of optical cables and wires to prevent the phenomenon of whiplash. The design to avoid the intersection of ADSS and wires in the side view and top view is a prerequisite for avoiding whiplash and ensuring that the optical cable does not contact the wires. It is unavoidable to cross, and the intersection should be placed as close to the poles on both sides as possible. At the same time, it is necessary to check that there will be no collision or contact when the wire and the optical cable swing asynchronously with the wind and when there is no wind with the seasonal sag (mainly refers to the intersection point in the top view). To meet the above requirements, it is mainly achieved by adjusting the position of the hanging point and properly selecting the sag of the optical cable.
4. The lowest point of the sag of the optical cable shall not exceed the lowest point of the sag of the wire to ensure the crossing distance and avoid external force damage.
5. The hanging point of the optical cable should be determined to facilitate the deployment of the optical cable, the installation of accessories, and the avoidance of collision with the supporting member when the wind is deflected, so as to avoid the optical cable from being worn.
6. When determining the position of the hanging point, special attention should be paid to the change of the wire arrangement, the cross-connection of the optical cable between the lines of different voltage levels, and the situation when the two ends of the line enter and exit the station. For example, when a double-circuit branch tower transitions to a single circuit, the conductors transition from a vertical arrangement to a horizontal or triangular arrangement; when the two sides of the stem tower are combined with different straight pole towers, the optical cables appearing on the stem tower are hung high on one side and hung on the other side. Situation; Cathead-shaped straight line towers are combined with poles in different arrangements; when optical cables are bridged between different lines; in short, enough attention should be paid to the above situation, and the appropriate position of the hanging cable should be determined by calculation and drawing. It is called a special hanging point in the design.
7. ADSS optical cable is a metal-free optical cable, and the sag basically does not change with temperature. In order to make the optical cable and the wire not collide, it is necessary to choose the optical cable sag, try to make the optical cable and the wire have no intersection in the side view, and determine the arc The vertical time should also satisfy that the tension of the optical cable under the conditions of the annual average temperature and the maximum design load is not greater than the maximum operating tension.
In general, after recent years of development, the safety of ADSS optical cable can be fully guaranteed after the various stages of production, transportation, construction, and acceptance. After market inspection and revision, more and more experience summed up, the role of ADSS optical cable in the power system has been highlighted.