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Aging causes of ADSS cable
Release Date: 2022-11-28

Use of ADSS Optical cables - all-dielectric self-supporting optical cables are widely used worldwide. Since its implementation, the extensive improvement of Z has been in the "arc resistant" sheath. The sheath material improves the performance of the cables and extends their life. However, even in cases where some degree of risk can be defined, it is not possible to predict the expected life of a cable in any given environment. In addition, some of the large numbers of cables that have been installed are at risk, but such problems are often not reported due to commercial sensitivities

The current along the ADSS cable acts as an aging factor for the sheath material. These currents along the cable are expected due to the potential gradient from three sources: through the conductor, the capacitive coupling between the ADSS cable and the ground; Through the voltage difference between the fixture and the mid-span position; And through the electrical conductivity of the surface of the cable. Normally, the potential Z of the mid-span is high, where the ADSS cable is positioned higher than the conductor (the cable is sagging), and the grounding potential is forced through the wire and the grounding metal clamp of the ADSS cable. Flattened to the ground. Electrical conductivity is affected by cable pollution and humidity. As the sheathing material ages, it becomes hydrophilic, and its resistance per unit length can be reduced to very low values of only a few hundred thousand ohms/m and current increases to a few milliamps. For 150kV laboratory measurement lines, the results show that the polyethylene limits are 1 mA and 1.5 mA.

Surface currents and discharges can cause joule heating of moisture and an increase in the surface temperature of the cable. After this heating effect, dry bands may therefore occur on the surface of the cable. Dry band Z may occur near a tower where the current is usually Z high. The dry strip has a higher linear impedance than the rest of the cable surface. This high impedance characteristic results in large voltage drops during short segments of dry cable and arc discharge. When the current is high enough to maintain an arc, an unstable discharge occurs on the dry strip. Uneven electrical conductivity on the cable surface caused by dry bands increases local electric fields and leads to corona and arc discharges that produce UV and ozone, both of which can damage the cable surface.

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