Today, we mainly share Five measures to improve the electrical resistance of ADSS optical cables.
(1) Improvement of tracking resistant optical cable sheath
The generation of electrical corrosion on the surface of the optical cable depends on three conditions, one of which is indispensable, namely electric field, moisture and dirty surface. Therefore, it is recommended that all OPGW optical cables be used on newly-built 110kV and above transmission lines; the lines below 110kV use ADSS optical cables with anti-track AT sheath.
(2) Improve the design and production of optical cables
In order to further improve the safety performance of the ADSS optical cable on the transmission line, it can be considered to reduce the sag of the ADSS optical cable erection, that is, to increase the tensile strength of the ADSS optical cable while reducing its creep value. When under severe conditions such as strong wind and sand, the creep and elongation of the optical cable will not be caused by the effect of wind, which will reduce the safety distance between it and the transmission line and cause electrical corrosion.
In the design of optical cable, three aspects are emphasized:
1. Increase the amount of aramid yarn to reduce the sag of the ADSS optical cable;
2. Using the high modulus and high strength aramid fiber newly researched by DuPont, its modulus is 5% higher than that of conventional aramid fiber, and its strength is about 20% higher than that of conventional aramid fiber, which further reduces the creep of ADSS optical cable;
3. Increase the thickness of the anti-tracking sheath from the conventional 1.7mm to more than 2.0mm, and at the same time ensure the tightness and smoothness between the molecules of the optical cable extruded sheath in the production to improve the electrical corrosion resistance of the optical cable.
(3) Choose a suitable optical cable hanging point
Choosing a suitable optical cable hanging point can effectively reduce the occurrence of electrical corrosion.
If there is no suitable hanging point on the line or the hanging point must be high for special reasons, certain remedial measures should be taken. The recommended remedial measures can be considered as follows: ①Add a metal sheet or metal ring as a shield near the end of the pre-twisted wire fittings, which can greatly improve the uniform distribution of the electric field and reduce the probability of corona discharge: ②The optical cable near the fixture Use arc-resistant insulating tape to wrap around the surface to control the repeated occurrence of arcs; ③Spread non-linear silicone insulating paint on the surface of the optical cable near the fixture. The function of the insulating paint is to slowly change the electric field at the coating position to reduce the possibility of corona and pollution flashover.
(4) Improve the installation method of fittings and shock absorbers
Improving the installation method of fittings and shock absorbers can improve the induction electric field environment near fittings and reduce the occurrence of electric corrosion. Install an anti-corona ring on the fitting about 400mm away from the end of the inner stranded wire, and install a tracking-resistant spiral shock absorber at about 1000mm from the end of the anti-corona ring. Under the induced electric field strength of 15-25kV, the distance between the anti-measuring ring and the spiral shock absorber should be kept above 2500mm to reduce the occurrence of electrical corrosion at the tightened contact position of the ADSS cable and the spiral shock absorber. The number of spiral shock absorbers used is determined by the pitch of the line.
Through this improved installation method, the anti-corona ring can greatly improve the electric field condition at the end of the pre-twisted wire fittings, and can increase the corona voltage by more than one time. At the same time, the anti-tracking spiral shock absorber can prevent the electric corrosion of the shock absorber. Damage to the fiber optic cable.
(5) Reduce damage to the cable sheath during construction
In the installation of optical cable racks, it is recommended that when selecting optical cable fittings, the hardware manufacturers must be required to strictly customize the outer diameter of the ADSS optical cable, so as to ensure that after installation, the gap between the strands of the fittings and the optical cable is minimized, and the salt is reduced. The ash enters the seam between the twisted wire fittings and the optical cable. At the same time, for tensile hardware, drape hardware, protective wire, etc., the product provided by the hardware manufacturer must be smooth at both ends of the twisted wire to prevent scratches on the cable sheath. The end of the twisted wire should be ground flat when the construction personnel are working to prevent damage to the cable sheath. These measures can reduce the accumulation and breeding of dirty dust in the cracks of the fittings and the broken skin on the surface of the optical cable, and reduce the inducement of electric corrosion.