introduction
The all-media self-supporting ADSS cable has been widely used in China's power communication because of its light weight, anti-interference and lightning protection. It is half of the power communication in China. Due to the vast land mass in China, the north and south of the Yangtze River, the mountains and mountains, the topography and landforms are very complicated, especially in some high mountain areas, the rock and phosphorus are listed, and the construction environment is extremely poor. At the same time, due to the structure and use characteristics of the ADSS cable, its construction method and requirements are significantly different from ordinary fiber optic cables. If the structural design and construction are carried out according to the conventional method, it is easy to cause unexpected failure. At present, there are widespread accidents in the industry due to improper construction or design defects, which may cause accidental failure after cable construction, which may cause fiber breakage or high attenuation. The opinions of the engineering team are different, and the responsibilities are unclear. Similar to these situations, the manufacturers are taking responsibility and carrying out the black pot. Therefore, it is very important to jointly strengthen research in this area and avoid failures in engineering construction. The following are some of the research and discussion we have done on structural improvement and construction methods, and some rules and measures have been found for reference by peers.
1. Optical cable structure and process method
As we all know, the design of the cable structure is directly related to the structural cost of the cable and the performance of the cable, and the reasonable structural design will bring two benefits. Achieving optimal performance metrics and the best structural cost are common goals.
Generally, the structure of the ADSS cable is divided into two types: a layer twist type and a center bundle tube type, and the layer twist type is more, and the structure is as shown in FIG.
As can be seen from the figure, the layered ADSS is characterized by an FRP center reinforcement, which is mainly used for central support, and some people call it a central anti-folding bar, but the beam tube type does not. For the determination of the size of the center FRP, it is relatively slightly better, but considering the cost factor, it is not the bigger, the better, here is a degree. For the conventional layer-twisted structure, the 1+6 structure is generally used, and in the case where the number of the optical fiber cores is not too large, the 1+5 structure is also adopted. Theoretically speaking, in the case that the number of structural cores is satisfied, the cost will be reduced by using a 1+5 structure, but if the same diameter is used, the diameter of the center FRP is only 70% of the 1+6 structure. The cable will be softer and the bending strength of the cable will be less, which will increase the difficulty of construction. If the structure of 1+6 is adopted, the pipe diameter must be reduced without increasing the cable diameter, which will cause difficulties in the process, because the cable must have sufficient length, and the necessary pipe diameter cannot be small. Therefore, the value must be moderate. Through the comparative analysis of the test results of samples of different process structures, such as the use of φ2.2 tube, 1+5 structure, and the use of φ2.0 tube, 1+6 structure cost is similar, but this 1+6 structure The center FRP is relatively thick, which will increase the rigidity of the cable, make the performance of the cable more reliable, the security is stronger, and the roundness of the structure is better. The choice of this structure and the choice of the number of cores in each tube depends on the level of craftsmanship. Under normal circumstances, it is better to use a layered type of large core size. The length of this structure can be relatively large. It is also the mainstream structure, and the most suitable for trunk use.
For the central tubular ADSS cable, the structural cost is relatively low, and it is an economical structure. The outer diameter of the cable is also relatively small, and the self-weight is also light, which is also beneficial to reduce wind load and ice load. However, due to the lack of a central anti-folding bar, the cable will appear softer, especially when installing the fittings, be sure to pay attention to the operation method, otherwise the cable will be damaged. Here to remind you that the production of this central tubular ADSS cable, production must pay attention to the control of the production process, one is the length, and the second is the cable sheathing process. Typically, this structure is used under small span or small load carrying conditions and is an economical and practical option. The number of cores of the cable can be 48 cores, which can be completed at one time from fiber to finished product. Rural network transformation is the best choice.
2, construction method
The formal construction method for ADSS optical cable must use the tension method to release the line, but some construction units, due to the lack of special construction equipment, use artificial traction to release the line, the construction hazard is very large, because many people, due to uneven force, will The cable is laid under the condition of non-constant tension. The local strain of the cable is inconsistent, and the change of the remaining length is different, which will bring long-term hidden danger to the cable. If it is artificially laid, be sure to pay attention to the uniformity of the force. The biggest advantage of mechanical payoff is that the tension is constant and the strain of the cable is always within a stable range. Moreover, due to the controllability of the tension, different take-up tensions are adopted for cables of different specifications to ensure that the construction quality meets the design requirements. Figure 2 is a simplified diagram of the process principle of a conventional construction equipment.
Among them, the tractor has two types of traction wheel type and reel type, and the traction wheel type is usually adopted. For the requirements of the traction wheel, the minimum outer diameter of the traction wheel should be at least 70 times the outer diameter of the cable, as large as possible. It is recommended to have a layer of elastic rubber as a buffer in the groove of the traction wheel to avoid scratching the cable. During the pay-off process, the traction and braking systems should operate smoothly to prevent any sudden pull or impact on the cable. These systems should be able to adjust and maintain a constant tension and line speed at all times. On the pay-off machine, there should be tension display and restriction device. The tension machine and the pay-off machine are determined according to the requirements of the tension release line and the weight and span of the installed cable. The tug of the tension machine should have a brake device. The cable can maintain a specific tension value at various traction speeds. The tensioner and the pay-off machine should have a flexible braking mechanism to maintain the tension on the cable when the line is suspended. It is best to use automatic protection. Type of device.
For the diameter of the pulley, there is also a requirement, usually the diameter of the bone wheel is required to be 40 times or more the diameter of the cable. The minimum radius of the pulley groove should be no less than 55% of the cable diameter and no more than 25% of the cable diameter.
In individual constructions, we also found improper tightening methods and tightening devices to damage the cable. The purpose of the tight line is to carry out the cable sag and tension adjustment. The cable cannot be damaged due to the tightener. The tension required by the tightener should be greater than the maximum traction tension of the cable.
When installing the fittings, it is also very likely to cause damage to the cable. Therefore, when installing the fittings, especially the pre-twisted wire fittings, it is necessary to use a pre-twisted special installation fitting, and it is forbidden to use a screwdriver or the like. Due to improper operation, some will break the fiber or cause high loss points at the metal fittings, sometimes causing the surface of the cable to be rough, and the metal end, it is easy to induce electrical corrosion of the cable. These are very serious problems, and must be highly valued by construction workers and supervisors and supervisors.
The control of the laying speed of the construction is also an important parameter. Under normal conditions, the speed of the line should not exceed 30 m/min. There must be someone on each pole.
Since the ADSS cable is different from the ordinary cable, the flexural performance of the cable is not very good. Therefore, during the construction process, the cable is cut and folded. The folding phenomenon is usually that the FRP is broken, the loose tube is broken, and the fiber is tested by OTDR. There will be high attenuation areas or high attenuation points. Due to the toughness characteristics of the sheath material, there will be no too much scar on the surface of the sheath. More serious will cause the FRP to puncture the loose tube and damage the fiber, resulting in fiber breakage.
These are caused by improper construction. As owners and optical cable manufacturers, it is necessary to strengthen supervision and supervision of the construction site. At many sites, we found a lot of construction teams. Because of the lack of knowledge of ADSS cable, the lack of construction experience of ADSS cable, sometimes the cable construction experience to deploy fiber optic cable; some also lack qualifications in this area, Dongla A few migrant workers in the west, Hu Hu to play; some equipment is not complete, the law is on the ground, the work is not standardized. These all pose risks to the safe deployment of the cable.
Unreasonable structural design and irregular operation are the root causes of optical cable anomalies after construction. As our cable manufacturers, we should first start with the structural design. Different laying environments, meteorological conditions, load sizes, and design methods should be different. In engineering, as a cable manufacturer, it is necessary to strengthen the supervision of the project to avoid and prevent the occurrence of anomalies.
3. Common accident phenomena and prevention methods
3.1 Appearance damage
Because some optical cable lines pass through hills or mountains, rocky shovel, and thorns, the cable is easy to rub on the trees or on the rock, which is very easy to be scratched or bent, especially the cable sheath is worn and the surface is not It is smooth and can be easily corroded due to dust and salty environment during use, which is extremely harmful to the service life. There must be multiple guardianship during construction, and the preparation should be carefully checked before pulling.
3. 2 fiber and high loss points
The phenomenon of fiber breakage and high loss point is due to the local force caused during the construction of the line. During the deployment process, the cable jumper, the speed is not uniform, the force is not constant, the diameter of the corner guide wheel, and The phenomenon of ringing of the cable will cause it. Sometimes it will be found that the center FRP is broken. Since the center FRP is a non-metallic material, the cable is retracted after being stretched, the disconnection will be misplaced, and the broken FRP will damage the fiber loose. Casing, even to the fiber, lightly caused high loss points, severe cases will break. This phenomenon is also a relatively common fault. Many people think that the quality of the optical cable is actually caused by accidents during construction. Therefore, constant tension control during construction is important, and it must be uniform.
3.3 End-end fiber breakage failure
The end-of-line breakage failure is also one of the more frequent accidents. It often occurs near the end of the sheet metal (pre-twisted wire), within 1 meter from the end of the metal fitting, and also has the part that is led from the tower behind the fitting. The former is often Due to improper man-made operation when pre-twisting the wire, the latter is often due to inconvenient terrain, the angle of the traction end is too small when the wire is tight, or the force is bent for a short time with the tower (rod). The radius causes the cable to be partially stressed. During construction, it should be noted that the direction of traction should be consistent with the direction of the cable, so that the cable is subjected to linear force.
Since the cable sheathing material and the force-receiving component have good elastic properties, after the cable is subjected to a short-term force, the surface of the sheath does not have obvious scratches, and the optical fiber component inside is damaged. At this time, most people will think that it is the quality problem of the cable itself, which will cause misunderstanding of the problem. I hope that I can give a judgment when analyzing and dealing with such phenomena.
For either side of the cable construction, the construction side, the owner or the cable manufacturer, do not want to have an accident, as long as the construction is strengthened, pay attention to the construction method, pay attention to every detail, and avoid abnormal phenomena. For the pre-construction survey, the supervision during the construction, all according to the procedures, to reduce mistakes.
4. Conclusion
Due to its use environment and its own characteristics, ADSS cable is not optimistic in the market prospects, especially in the saline-alkali area, the use of high field strength environment, the phenomenon of electrical corrosion is more serious, this is its weakness, but in other air environment comparison In a good area, the voltage level is not too high, or it has its advantages. As the price of fiber optic cable decreases, the process continues to mature and improve, the performance of the cable is further improved, and the structure and environment of the cable are improved. Organic combination to avoid irregular behavior during construction, economical ADSS cable still has a certain market space.
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