1. Eddy current problems caused by high current power cables
In the construction of power cables, steel brackets are used, steel protection pipes are used, and cable clamps and overhead laying are used. Any steel (iron) closed circuit formed around the power cable may cause eddy currents. Especially in high-current power cable systems, the eddy current is greater. During the construction of power cables, measures must be taken to prevent the formation of steel (iron) closed loops around the cables to prevent the occurrence of eddy currents caused by the cables.
2. It is the mechanical damage caused by the turning of the power cable
Due to the large outer diameter of the power cable, it is difficult to transport and lay, and the power cable has stricter requirements on the turning radius. During the construction of the power cable, if the turning angle is too large, the inside of the conductor may be mechanically damaged, and the mechanical damage will be reduced by the insulation strength of the cable until a failure occurs. A cable head failure is found during the construction. During the production of the cable head, three cables The length of the head is the same. Due to the restriction of the terrain when connecting with the equipment, the medium-phase cable head is too long and becomes arched, and the root of the cable head is damaged and discharged. Afterwards, measures were taken to appropriately shorten the connection length of the middle-phase cable head in the connection of the equipment, so that the three-phase cable head is not subject to external force. Practice has proved that the operation effect is good. It can be seen that in the process of cable construction, it is necessary to reduce the torsion force of the cable as much as possible. When the cable is turned and the cable is left, the cable is naturally bent to prevent internal mechanical damage.
3. It is the moisture-proof problem of the power cable
Operating experience has shown that most of the failures of medium and low-voltage power cables are cable intermediate joints and terminal head failures, while the majority of intermediate joints and terminal head failures are caused by poor sealing and moisture intrusion, which causes the insulation strength to decrease. The network mostly adopts tree-like power supply mode, and the number of cable terminal heads is large. Therefore, plugging and sealing the cable terminal head and the intermediate joint is one of the important measures to ensure the safe and reliable operation of the cable.
4. It is a grounding problem of medium and low voltage power cables
In the public medium and low voltage power cable network, because the three-phase load is not equal, if a cable with a metal sheath is used, the grounding problem of the metal sheath must be considered, and it must be ensured that the metal sheath is not grounded at any point The normal induced voltage shall not be greater than 100V. I think that in the medium and low-voltage cable network, all cable joints should be equipped with grounding electrodes (nets), and the metal protective layer should be reliably grounded.