What Is OPGW Optical Ground Wire?

OPGW is primarily used by the electric utility industry, placed in the secure topmost position of the transmission line where it “shields” the all-important conductors from lightning while providing a telecommunications path for internal as well as third party communications. Optical Ground Wire is a dual functioning cable, meaning it serves two purposes. It is designed to replace traditional static / shield / earth wires on overhead transmission lines with the added benefit of containing optical fibers which can be used for telecommunications purposes. OPGW must be capable of withstanding the mechanical stresses applied to overhead cables by environmental factors such as wind and ice. OPGW in transmission line must also be capable of handling electrical faults on the transmission line by providing a path to ground without damaging the sensitive optical fibers inside the cable.

The characteristics and application environment of OPGW optical cable are:

1. The OPGW cable is metal armored, which has no effect on the corrosion and degradation of high pressure marks;

2. The OPGW cable shall not run live during the construction, and the power failure loss is large. Generally, the OPGW cable should be used in the new 110kV high-voltage line;

3. For high-voltage lines above 110kV, the span is large (generally above 250M);

4. It is easy to maintain and easily solve the problem of wire passing, and its mechanical characteristics can meet the requirements of large wire passing.

According to Q=I2t, the heat resistance of OPGW cables can also be improved by limiting the magnitude and duration of the actual short-circuit current. The OPGW cable is affected by the short-circuit fault. When the line fault short-circuit current impacts the OPGW cable, the stainless steel unit becomes high temperature instantly. The short-circuit current capacity of the cable must be increased to reduce the impact of the short-circuit fault on the cable.

The main fault in the application of OPGW optical cable is the broken strand caused by lightning strike. The current solutions mainly include the following:

1. Develop new lightning protection outer layer materials. The high lightning protection OPGW developed in Finland in 2001 uses high-grade galvanized steel wire and aluminum tube to protect the optical fiber. High-grade galvanized steel requires more energy to melt under a lightning strike.

2. Use aluminum-clad steel wire as much as possible for the outer layer to increase the thickness of the aluminum-clad steel wire.

3. Try to increase the design air gap between the outer strand and the inner strand to avoid heat transfer.

4. Under the same material, use a larger outer strand diameter. After the material and structure of the OPGW optical cable are determined, its lightning protection performance is determined.