Concentric cable is a cable consisting of two or more concentric conductors, in particular one of the neutral wires coiled around the inner conductor. The allowable bending radius of concentric cables shall be: a single-core cable shall not be less than 20 times the outer diameter of the cable; The multi-core cable shall not be less than 15 times the outer diameter of the cable. The reactance of the concentric conductor is much lower than that of the fourth conductor of the common four-core cable in the zero-sequence working state, which is conducive to the sensitive action of the short-circuit automatic protection device, thus ensuring the safe operation of cable-related equipment. Cable has strong anti – electromagnetic interference and anti – lightning characteristics. Concentric cable has low and uniform positive (inverse) sequence and zero sequence impedance, which is beneficial to improve power supply quality.
This product is suitable for power transmission in power lines with rated voltage of 0.6/1kv and below.
The products of concentric cables can be divided into two categories according to different conductors: aluminum concentric cables and copper concentric cables.
Cable characteristics:
- The rated voltage uo / u is 0.6/1kv.
- The maximum allowable working temperature of cable conductor for a long time: 90 ℃ for XLPE insulation and 70 ℃ for PVC insulation.
- When the cable is short circuited (the longest duration is not more than 5S), the maximum temperature of conductor is 250 ℃ for XLPE insulated cable and 160 ℃ for PVC insulated cable.
- The ambient temperature for laying shall not be lower than 0 ℃, and the temperature lower than 0 ℃ shall be heated in advance. The allowable bending radius of the cable is not less than 20 times of the outer diameter of the single core cable; The multi-core cable shall not be less than 15 times of the outer diameter of the cable.
- The finished cable shall withstand 3500v power frequency voltage test for 5min without breakdown.
- The cable has low and uniform positive (negative) sequence and zero sequence impedance, which is conducive to improving the quality of power supply.
- The reactance value of the concentric layer conductor is much lower than that of the fourth core of the common four core cable in the zero sequence working state, which is conducive to the sensitive action of the short-circuit automatic protection device, so as to ensure the safe operation of the cable related equipment.
- It has strong anti electromagnetic interference and anti lightning performance.
- Combustion characteristics of cables: flame retardant cables shall be able to withstand bundle combustion test specified in (1EC332-3). Fire resistant cables shall be able to withstand the fire resistance test specified in (1EC331).
