The good protective performance of optical fiber makes its lightning protection work less obvious than that of coaxial cable and bright line circuit. As the large number of optical cables is adopted, lightning strikes have occurred in the optical cable line in recent years. The cable has a lot of communication capacity, and the most vulnerable to lightning is the direct buried line, which is difficult to repair, so there will be huge losses if there is an obstacle.
Optical fiber is not conductive and can be protected from shock current. But in order to make high capacity optical fiber from environmental events (such as animal bite, rocks, aerial collision metal accessories, shotgun damage, and other natural and man-made events, etc.), the influence of fiber optic cable must be armoured components, mainly metal armoured layer, strengthen the core, they have a plenty of the metal conductor.
Lightning has a tendency to find the minimum path of impedance to discharge thundercloud charge and the underground charge neutralization. In the construction of the optical cable, PE (PE) sheath can be damaged. In addition, rat bite and external force may cause the exposure of metal elements in the fiber optic cable. These exposed points are liable to lead to damage caused by the introduction of strong or lightening charges.
According to the relevant data, in the following situations, the optical cable line is vulnerable to lightning: the metal sheath, reinforced core or copper wire to the ground insulation lower fiber cable. Terrain mutation and soil resistivity vary greatly. The optical fiber cable is not enough distance between a single tree or tall building.
According to the above analysis, the cable line should also pay attention to its lightning protection work. Lightning protection of the cable line can be targeted at local weather and terrain and other natural conditions.
The following problems should be paid attention to in the construction and maintenance of optical cable.
1. for aerial optical cable, connector box usually have to strengthen the structure of the core can be broken even, whether using electrical connections or disconnect, metal pressure plate structure is superior to the self-contained bolt connection, and the self-contained horizontal hole is better than vertical slot structure, it is a problem that should be paid attention to when choosing connector box.
2. for buried cable line lightning protection: first, the station grounding method, in the joint of the metal part of the cable shall be connected, the relay length of cable, moistureproof layer, strengthen core armoured layer connected state. At both ends of the board (station), the fault layer should be strengthened, and the moisture-proof layer should be grounded through the arrester.
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