Problems needing attention in
power cable construction
With the continuous promotion and use of
power cables in distribution networks, distribution networks can be divided into cable networks and overhead networks. Therefore, when the regional network of the distribution network adopts the wired network, new technologies and new equipment should be adopted according to the requirements of distribution automation. If possible, automated pilot work should be considered. If the conditions are not mature, there should be enough room for the selection of supporting equipment to lay the foundation for the realization of the automation scheme.
1. Eddy current power cable caused by large current
During the construction of the
power cable, some steel brackets, some steel protection pipes, some cable clips and overhead laying were used. No matter which steel (iron) closed loop is formed around the
power cable, eddy currents may be formed, especially in high-current power cable systems. During the construction of power cables, measures must be taken to prevent the formation of a closed loop of steel (iron) around the cables and prevent eddy currents from occurring in the cables.
2. Cable moisture problem
Operational experience shows that most of the faults of medium and low voltage
power cables are the faults of the intermediate joints and terminal heads of the cables, while the faults of the intermediate joints and terminal heads are mostly due to poor sealing and moisture intrusion leading to a decrease in dielectric strength. The medium and low voltage power cable network mostly adopts the dendritic power supply mode, and the number of cable terminals is large. Therefore, properly sealing the cable end and intermediate joint is one of the important measures to ensure the reliable operation of the cable.
3. Grounding problems of medium and low voltage
power cables
In the public medium and low voltage power cable network, since the three-phase loads are not equal, if the metal sheathed cable is used, the grounding problem of the metal sheath needs to be considered. The normal induced voltage of any non-grounding point of the metal sheath should not be greater than 100V. In the medium and low voltage cable network, all cable joints should be equipped with a grounding grid, and the metal sheath should be reliably grounded.
4. Mechanical damage caused by
power cable rotation
Due to the large outer diameter of the power cable, transportation and laying are difficult, and the power cable has strict requirements on the turning radius. During the construction of the
power cable, if the turning angle is too large, mechanical damage may occur inside the wire, but the mechanical damage is due to the reduction of the insulation strength of the cable until failure occurs. A faulty cable head was found during construction. When manufacturing cable heads, all three cable heads are the same length. Due to terrain restrictions, the mid-phase cable head is too long and arched, and the root of the cable head is damaged and discharged.
Then take measures to appropriately shorten the connection length of the middle-phase cable head in the equipment connection, so that the three-phase cable head is not subject to external force, and practice has proved that the operation effect is good. It can be seen that in the process of cable construction, the torsional force on the cable should be reduced as much as possible, and when the cable turns and leaves the cable, the cable is allowed to bend naturally to prevent internal mechanical damage.
