The selection principle of OPGW optical cable is generally considered and checked from the following aspects:

1. It is necessary to meet the requirements of meteorological conditions, the requirements of its own tensile strength and the requirements of the tower to allow design loads.

2. The main technical data to be considered in the design of OPGW cable are: fiber type, fiber core number, cable diameter, cable cross-sectional area, cable unit mass, ultimate tensile strength, short-circuit current, DC resistance, elastic modulus, thermal expansion coefficient , annual average operating stress, minimum bending diameter, maximum disk length, etc.

3. OPGW cable can be selected under the condition that the ambient temperature is +15 °C, no ice, no wind, and the same as the sag of another ground wire.

4. The OPGW cable allows the determination of the short-circuit current. First determine the short-circuit current equivalent time, generally 220kV line when the short-circuit current is large, the fault current equivalent time can be considered according to 0.3s. According to the short-circuit current provided by the system, calculate the total short-circuit current of the line into the ground, calculate the short-circuit current distribution of the OPGW and the other ground line at the exit of the substation by calculating the short-circuit current distribution of the OPGW and the other ground line. When a single short circuit occurs on the line, a short large current flows on the overhead ground line, and the heat generated by the current increases the temperature of the cable and the shunt line. Because the current duration is short, heat is not dissipated into the surrounding environment, causing the wire temperature to rise. When the temperature of the wire exceeds its allowable temperature, it will seriously affect the safe operation. Therefore, meeting the thermal stability requirements is an important condition for determining the OPGW cable and the shunt line. For the OPGW cable, the short-circuit current and the allowable temperature provided by the manufacturer are generally used. We only check it. The OPGW can select the type according to the short-circuit current everywhere.

5. The OPGW cable should have a good level of lightning resistance. When lightning strikes the OPGW cable, the communication quality should not be affected, and the metal part should not break.

6. Selection of another ground wire that matches the OPGW
In order to meet the requirements of short-circuit current, simply increasing the cross section of the OPGW cable is not only uneconomical, but also extremely uncoordinated and matched with another ground. The solution is to use a good conductor ground wire with better conductivity. Because of its low resistance and self-impedance, more current is distributed to the ground line, which reduces the current through the OPGW cable. A good shunt is achieved. Although the resistance of the shunt line can be lowered very low, the inductive reactance drops very slowly, so the effect of the shunt line has certain limitations. The shunt line, like the OPGW, can be segmented according to the short-circuit current throughout the line. It is necessary to pay special attention to the fact that in the place where the shunt line changes the model, the shunt line becomes thinner, and more current is distributed to the OPGW cable, so the current of the OPGW suddenly rises a lot, so the selection of the shunt line is carried out. Repeated calculations.
 
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