Adding ADSS cables to the 110kV line that has been in operation, the main problem is that in the original design of the tower, there is no consideration at all to allow the addition of any objects outside the design, and it will not leave enough space for the ADSS cable. The so-called space not only includes The installation point of the optical cable also includes the mechanical strength of the tower and other related factors. In other words, ADSS optical cables can only adapt to the original towers as much as possible.
1. Load-bearing tower
This kind of poles can withstand the normal longitudinal tension of the line and the tension of the broken line in the event of an accident. According to the purpose, it can also be divided into towers such as tension, corner, terminal, and branch. Usually, ADSS optical cable lines are equipped with strain-resistant (also called "static end") fittings on these towers. The load-bearing pole tower is an important basis for the position of the optical cable distribution and joints. The load-bearing pole tower of the additional optical fiber cable must be checked for strength to confirm that the additional tension of the optical fiber cable is still safe for the tower under extreme weather conditions.
2. Straight pole tower
This is the largest number of poles in the transmission line. It is used on the straight section of the line to support the vertical (such as gravity) and horizontal loads (such as wind load) of the line. According to the purpose, it can also be divided into towers such as corners, transpositions, and spans.
ADSS cable lines are usually not used as optical cable joints on straight poles and towers. In principle, straight (or "hanging") fittings are used. Under special circumstances, if it is necessary to connect the straight pole tower, specially designed fittings must be used.
3. Tower type
The tower type is related to factors such as the voltage level of the transmission line, the number of circuit loops and the conductor structure, meteorological conditions, topographical geological conditions and other factors. There are many types of poles and towers in our country and they are very complicated. Optical cable and tower type are directly related to the choice of hanging points and directly affect the service life. The idea that the ADSS cable can be installed at a certain distance from the wire is wrong, at least not strictly.
The tower body will determine the installation height of the optical cable, and must meet the safe distance between the lowest point of the optical cable sag and the ground or structures under extreme weather conditions. The tower head will determine the position of the hanging point of the optical cable, at which the electric field strength should be the smallest or relatively small, and meet the requirements of the anti-tracking level of the outer sheath of the optical cable.
The aerodynamic performance of ADSS cable is mainly related to the mechanical performance of ADSS optical cable, tower conditions and meteorological conditions. The mechanical properties of ADSS cables include cable diameter, cable weight, tensile strength, elastic modulus, etc.; poles and towers mainly refer to span, installation sag, etc., and meteorological conditions refer to wind speed and ice thickness, which can be equivalent to optical cable Wind load and icing load to withstand.
The ADSS cable is set up in the strong electric field environment of the high-voltage line. The potential generated by the coupling capacitor between the ADSS optical cable and the high-voltage phase line and between the ADSS optical system and the earth generates current on the surface of the wet optical cable. When the surface of the optical cable is half-dry and half-wet At this time, an arc will occur in the dry area, and the heat caused by the arc will erode the outer sheath of the ADSS light environment. In order to prevent the occurrence of the above phenomenon, the international standard of ADSS optical cable requires that the optical cable can work normally in the field strength of 12kV/m. If the electric field strength is greater than 12kV/m, ADSS cables with anti-corrosion sheaths should be selected.