The voltage level of the coaxial grounding cable should be determined according to the induced potential of the cable line. According to the past design experience, the voltage level of the coaxial grounding cable is generally 10kV; the cross-section of the coaxial grounding cable should be strictly selected according to the grounding current of the cable line. However, in actual work, due to the lack of data and the complexity of calculation. The main models are VOV, YJOV, and YOY.
High-voltage cables are designed according to single-loop, double-loop, or even more loops. If the length of a single cable is longer, the induced potential will be larger. It is best not to exceed 50v, that is, the voltage of 50 volts without protection devices. But if there are protective devices, such as return lines, coaxial cables, etc., it should not exceed 300v.
The coaxial grounding cable is generally used for the lead wire of the arrester and the grounding wire of the lightning protection, and the grounding box of the line sheath insulation protection device of the cross-linked cable is connected. Impedance, coaxial ground cables have low impedance characteristics for transients.
VOV (YOV YJOV) is generally used for cross-connection of high-voltage cables to reduce the induced potential of the metal sheath. The protection box used for the 110KV～220KV cross-linked cable line sheath insulation protection device is connected with the transposition box. It is used for ground connection in transmission and distribution lines, and connection in cross-connect boxes. The inner and outer conductors of the coaxial cable are connected reasonably and conveniently and are reliable in use.
1. The maximum allowable working temperature of the conductor: is 90℃.
2. The bending radius is not less than 20 times the outer diameter of the cable.
3. The ambient temperature should not be lower than 0℃ when laying the coaxial grounding power cable.
4. The power frequency rated voltage 8.7/10KV transmission and distribution line (110kv ~ 220KV) is grounded.
5. The connection wire between the metal sheath of the cable or the voltage limiter of the shielding layer shall meet the following requirements: First, the connecting line should be the shortest, and coaxial cable should be used above 3m. Second, the insulation level of the connecting wire shall not be less than the insulation level of the outer sheath of the cable. Thirdly, the cross-section of the connecting line should meet the thermal stability requirements when the single-phase grounding fault current of the system passes through.
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