How to reduce the opgw cable to be struck by lightning

The damage phenomenon of OPGW cable after lightning strike is similar to that of overhead ground wire, which is mainly manifested in the formation of melting spots or melting fractures after the outer stranded wire is struck by lightning. How to reduce the lightning strike of opgw has the following aspects.

A. Design a certain air gap between the outer stranded wire and the inner stranded wire of the OPGW cable, which is conducive to the rapid dissipation of high-temperature heat generated by lightning strikes, prolonging the time for the heat to diffuse to the inner stranded wire and optical fiber, and avoiding overheating and burning the fiber. core.

B. Reduce the grounding resistance of the transmission line tower and improve the lightning resistance level of the transmission line. Within the range of 1-2km from the substation entry and exit line sections at both ends of the transmission line, the power frequency grounding resistance of the tower should not be greater than 10Ω, and other line sections should not be greater than 30Ω; this method is mainly to reduce the short-circuit current flowing through the OPGW. Connect the grounding of the first base tower to the grounding grid of the substation.

C. Select a good conductor ground wire that matches the OPGW optical cable or increase the cross-sectional area of the shunt ground wire to improve the shunt coefficient of the good conductor ground wire and reduce the lightning current flowing through the OPGW cable during lightning strikes.

D. Under the condition of meeting the requirements of S≥0.012L+1 and the load of the tower, the large cross-sectional area OPGW optical cable of the multi-layer structure should be selected as much as possible, and the single-layer structure OPGW optical cable should be avoided.

E. In the path selection of high-voltage transmission lines, try to avoid the surrounding mountains and middle concave areas in areas with frequent lightning activities, hillsides with large gradient changes, areas with metal deposits under the surface layer, and areas near ponds. In order to reduce the probability of lightning strikes on transmission lines;

F. The outer stranded wire of OPGW cable is mainly composed of aluminum alloy wire (AA wire) and aluminum clad steel wire (AS wire). The aluminum clad steel wire has good electrical conductivity, and its melting point and mechanical strength are higher than those of the aluminum alloy wire. , It is not easy to fuse under the high temperature of the arc, and it is not easy to be stretched and broken even if a certain degree of erosion occurs. Therefore, the outer layer of the OPGW optical cable adopts the full AS line, which is generally beneficial to improve the lightning resistance level of the OPGW optical cable and reduce the probability of the OPGW being struck by lightning.