How to control the electrical corrosion of ADSS optical cable?
As far as we know, all electrical corrosion faults occur in the active length zone, so the range to be controlled is also concentrated in the active length zone.
1. static control:
Under static conditions, for the AT sheathed ADSS optical cable working in 220KV system, the spatial potential of its hanging point should be controlled not more than 20KV (double-circuit and multi-circuit co-frame lines should be lower); working in 110KV and below systems For the PE sheathed ADSS optical cable, the spatial potential of the hanging point should be controlled to be less than 8KV. The spatial potential design of the static hanging point should take into account:
(1) System voltage and phase arrangement (dual loops and multiple loops are very important).
(2) The shape of the pole and tower (including the tower head and the nominal height).
(3) The length of the insulator string (the length varies according to the pollution level).
(4) The diameter of the conductor/ground wire and the split of the conductor.
(5) The safety distance between the wire and the ground and the crossing objects.
(6) Tension/sag/span control (under no wind, no ice, and annual average temperature, the load is not greater than the ES of the optical cable, which is 25% RTS; under design weather conditions, the load is not greater than the optical cable The MAT is 40% RTS).
(7) Jumpers (tension poles) and grounding bodies (such as cement pole cables) should be studied and their influence should be considered.
Under dynamic conditions, the space potential of the AT sheathed ADSS optical cable working in a 220KV system should be controlled to no more than 25KV; the PE sheathed ADSS optical cable working in a system of 110KV and below, the space potential of the hanging point should be Control it to no more than 12KV. Dynamic conditions should at least take into account:
(1) The system voltage is the nominal voltage, and under certain circumstances there will be an error of +/-(10～15)%, and the positive tolerance shall be taken;
(2) The string of fittings (mainly the hanging string) and the wind swing of the optical cable;
(3) Possibility of original phase transposition;
(4) Possibility of single-circuit operation of dual-circuit system;
(5) The actual situation of pollution transfer in the region;
(6) There may be new crossover lines and objects;
(7) The status of municipal construction and development plans along the line (it may raise the ground);
(8) Other conditions that will affect the optical cable.
Reminds that these must be paid attention to in the construction of ADSS optical cable wiring.
(1) The electrical corrosion of the ADSS optical cable sheath under tension during operation is caused by the ground leakage current of approximately 0.5-5mA and the dry band arc caused by the space potential (or electric field strength) through the capacitive coupling. If measures are taken to control the ground leakage current below 0.3mA and a continuous arc is not formed, electrical corrosion of the sheath will not occur in principle. The most realistic and effective method is still to control the tension and spatial potential of the optical cable.
(2) The static space potential design of AT or PE sheathed ADSS optical cable should be no more than 20KV or 8KV, respectively, and should be no more than 25KV or 12KV under the worst dynamic conditions. The fiber optic cable can be operated safely.
(3) The static space potential is 20KV (mostly 220KV system) or 8KV (mostly 110KV system). The anti-vibration whip separation hardware in the system is not less than (1～3)m or 0.5m, respectively, to improve ADSS One of the effective measures for electrical corrosion of optical cables. At the same time, the vibration damage of ADSS optical cable and other anti-vibration methods (such as applicable anti-vibration hammer) should be studied.
(4) The installation position of the optical cable (often called the hanging point) cannot be determined empirically based on the system voltage level and/or the distance from the phase conductor. The space potential of the hanging point should be calculated according to the specific conditions of each tower type.
(5) Although there have been frequent electrical corrosion failures of ADSS optical cables in recent years, a large number of practices have proved that ADSS optical cables can continue to be promoted and applied in 110KV systems; ADSS optical cables used in 220KV systems take full account of static and dynamic working conditions. Later, you can continue to promote the application.
(6) On the premise of ensuring the quality of ADSS optical cable, standardize engineering design, construction and operating conditions, and the electrical corrosion of ADSS optical cable can be controlled. It is recommended to formulate and implement corresponding norms/procedures as soon as possible.