At present, ADSS special power cable, as a network channel, is widely used in optical fiber communication in the power industry. With large capacity and good anti-interference performance, optical fiber communication can not only meet the needs of communication and automation in the power system, but also provide the society with surplus capacity.
Optical fiber communication can not only improve the reliability of power supply, but also obtain good economic benefits.
It is a very economical way to lay optical cable by using overhead power line corridor to set up on the line tower.
At present, there are two main types of optical cable in overhead transmission lines: optical fiber composite overhead ground cable (OPGW) and all-medium self-supporting optical cable (ADSS).
OPGW is usually chosen for newly built power lines and ADSS is often used for built power lines.
Compared with OPGW, ADSS cable has a small investment. It can be set up under the condition of power line without power failure, and its design, construction and maintenance are also more convenient. It has been widely used in the completed power line.
Application scope of ADSS cable
For new or already built 220 kv and above transmission lines, and as a communications line corridor, in order to ensure the communication lines and transmission line running life (more than 30 years) match, from the reliability of the optical fiber communication, construction and maintenance and so on into consideration, engineers should choose OPGW, trunk lines of 220 kv and above transmission lines is unfavorable choose ADSS cable.
For the established transmission lines of 220kV and below, especially the communication between regional substation, ADSS cable can be considered.
Engineers should first consider the reliability of ADSS cable on existing power lines, evaluate the running time of power lines, aging degree of towers, original design standards and other conditions, so as to determine the feasibility of erection.
Because the technical regulations of power line design have been modified, adjusted and supplemented over the years, it is difficult to check the strength of the power line tower that has been in operation for many years, which becomes a key problem in the establishment of ADSS optical cable.
The general principle is not to affect the safe operation of power lines, not to reduce the reliability of the premise, can set up ADSS cable.
Therefore, the author suggests that the ADSS cable should be set up as far as possible to choose the power line with better tower conditions.
In terms of products, currently has domestic ADSS cable products and inspection standards, such as the national standard GB/T18899 totally medium messenger cable and electric power industry standard DL/T788 totally medium messenger cable, main international IEEE P1222 - "all medium messenger for overhead transmission line cable IEEE standard (draft) and IEC60794-4 specification - the cable part 4: points along the cable of power line erection.
In engineering, domestic electric power industry standard DL/T5344 the acceptance of electric power optical fiber communication engineering and DL/T767 the whole medium messenger cable (ADSS) with a hinge hardware technical conditions and test methods, but so far no mature and effective for ADSS cable line engineering design regulations/procedures and specifications, so the ADSS cable installation design, only by reference to the current power industry standard DL/T5092 "technical code for design of 110-500 kv overhead transmission lines".
Two, ADSS cable choice
(1)ADSS fiber optic cable structure
The STRUCTURE of ADSS fiber optic cables is divided into two categories: central beam tube and layer stranded beam tube. In addition to some power lines with good conditions in all aspects, ADSS fiber optic cables with layer stranded beam tube structure should be generally selected.
The optical fiber in ADSS cable is introduced into the beam tube in a wavy shape, and then the beam tube is twisted to produce twisted residual length. The optical fiber has an appropriate residual length, which ensures that the optical fiber is not stressed when the cable is under normal working mechanical load (namely the optical fiber zero tension design), and will not increase the loss of the optical fiber.
(2) ELECTRICAL performance of ADSS
ADSS cable types to choose the first thing to consider electrical performance requirements, namely the ADSS are space the size of the induced electric field (potential), because the ADSS cable work near the high voltage line wire, wire surrounding space electromagnetic fields, fiber optic cable to the cable capacitance coupling between conductors and ground in the position of the potential of a space, because of the fog, dew or light rain, wet the filth of the resistance in the cable outer sheath surface to form a layer.
Under the action of space potential, sheath flow between the surface of the fiber optic cable on the tower grounding hardware have current, current fever caused by moisture to evaporate, make form small section of the surface of the fiber optic cable outer sheath dry zone, blocking the current, when dry, with potential to reach a certain height, it happened form arc discharge, this is the dry band arc.
The heat generated by it can cause the crosslinked polymer to gradually lose its binding force and form corrosion, and the sheath will melt into holes.
This phenomenon, or failure, is called sheath corrosion or electrical marking, which can lead to cable breakage in severe cases.
The type of outer sheath used in ADSS depends on the space potential of the cable installation location, and is related to the voltage class of power lines, tower structure, wire arrangement and phase arrangement, etc.