How lightning protection cable line

The lightning protection cable line

Optical performance makes it a good lightning protection work like coaxial cable and open wire circuits as obvious, and thus the rapid development in fiber-optic cables in the process, safety ground is often misunderstood, and even forgotten. With the extensive use of fiber optic cable, fiber optic lines in recent years, lightning strikes have occurred. Communication cable line has great capacity, and the most vulnerable to lightning is buried lines, repair more difficult, so in the event of obstacles, will result in huge losses. In this paper, the domestic norms of communication lines, lightning protection, lightning protection cable line to talk about. 

A fiber-optic cables causes lightning

       Optical fiber is not conductive nature, can be free from the impact of current. However, in order to make high-capacity fiber from environmental events (such as animal bite, rock, metal accessories for the collision damage to overhead and other natural and man-made events, etc.) the impact of cable must be armored elements are metal armor loading level, strengthening the core and copper and other business, they are metallic conductors. When the power lines close to short circuit or lightning metal components, the AC will be induced or surge current, injury or damage to personal safety line device.

Lightning has a minimum impedance path to find the charge and discharge thundercloud and the ground floor opposite charge in the trend. When lightning strikes the earth or near buildings, lightning point of potential rise, and fiber optic cable extends to the far, remote potentiometer can be regarded as 0, so the potential of lightning near the cable is also regarded as 0. This lightning-point fiber optic cable between the great and the potential difference, the potential difference in excess of Jiang Lei point between the cable outer sheath of the compressive strength, it will breakdown the outer protection layer formed from the lightning point to the metal components arc channel, so a lot of lightning current flock to the cable, causing serious damage to the cable. Fiber-optic cables in the construction inevitably damage the PE (polyethylene) sheath, the other rat-bite, external staff may result in cable in the metal components exposed. The exposure point is easy to load into a strong electrical or lightning cable, causing damage.

       I have participated in a provincial trunk buried fiber optic cable lightning fault repair work. The lightning Pitch Relay Board cable 800m, 20m apart, there are two lightning point, the situation is basically the same damage, cable jacket and sheath were burned, the fiber is fully blown. Relay Board Terminal Box (the line cable connectors for the electrical disconnect at the metal component processing) in the fixed core and metal sheath to enhance the nut is part of the melt, the fiber coating was all burned, exposed core, of which 6 core has been blown. Terrain from the lightning point of view, the area is hilly, there are about 10m away from the cable parallel to a river close to the river there is a row of trees from the cable close. The analysis that lightning is introduced by means of trees or other land breakdown of soil from the point of cable outer jacket damage and strengthen the core into the metal sheath (the structure of the fiber optic cable in the cable on both sides to strengthen the core). Data indicate that, in the following cases, fiber-optic cables are vulnerable to lightning strikes:

① metal sheath, strengthening the core or low copper ground cable insulation.

② mutation terrain, soil resistivity changes in the larger area.

③ cable or high-rise buildings and single-tree gauge is not enough.

References: www.chinaopticcable.com