Galvanic corrosion caused by dry-band arcing

In the 110-220kv high-voltage power grid, the optical cable runs in a high electric field and a dirty environment for a long time. The surface of the optical cable has a high potential, and the surface is affected by the dirty environment to form a semi-conductive layer. In this way, the ADSS cable and the grounded fittings generate a certain leakage current, and the heat generated by the current flowing from the middle of each cable to both ends causes the water on the surface to evaporate to form a local dry area. When this potential is accumulated to a high enough level, the ADSS cable discharges and forms Arc, with the increase of the number of discharges, the outer sheath of the optical cable is ruptured or even broken. It can be seen that the main culprit of electrical corrosion of ADSS optical cable is this dry-band arc [2].

Electrocorrosion caused by corona discharge

Because ADSS optical cable is a non-metallic material and has a small wire diameter, although the anti-vibration whip is added 15-20cm outside the pre-twisted wire during the construction of the optical cable, the vibration frequency and vibration amplitude of the breeze are higher than those of the metal wire with a larger diameter. a lot of. Therefore, the contact surface between the end of the pre-twisted wire and the end of the anti-vibration whip or the anti-vibration hammer is small, resulting in uneven distribution of the electric field; secondly, the induced voltage changes much faster along the direction of the optical cable than in other places; when the field strength reaches a certain height, the pre-twisted wire The end and the end of the anti-vibration whip become the discharge electrode to generate corona discharge. The electrical corrosion caused by corona discharge will make the outer sheath of the optical cable crack, the inner aramid yarn will be carbonized and deteriorated, and the tensile strength of the optical cable will be reduced. Z eventually caused the phenomenon of cable break

Design and construction of optical cable

The design position of the hanging point

By calculating the field strength, choose to set the hanging point in the place where the field strength is small. At present, field strength calculation software is basically used, a static mathematical model. Calculate the field strength under several extreme states and select the appropriate optical cable hanging point. These software do not consider the tower for calculation. In fact, the tower acts as a ground electrode, which will have a great impact on the calculation results. Therefore, it should also be combined with the on-site Actual situations should be handled with caution.

Construction

Compared with other factors, the electrical corrosion caused by the construction of the optical cable has less influence, but it also exists. During the construction process, there are three main reasons why the outer sheath of the optical cable may be damaged or worn: 1. The tension release line is not adopted in accordance with the construction specifications of the power optical fiber communication project, so that the optical cable is scratched by the ground stones or branches; 2. When the cable is released , the pulley does not match the outer diameter of the optical cable; three, the hardware scratches the outer sheath of the optical cable. Once the outer skin of the optical cable is scratched, it is very likely that electrical channels will appear over time, and electrical corrosion will occur.