Power supply system operation quality, safety and reliability is not only related to the quality of the wire and cable itself, but also with the cable accessories and line construction quality.
1. Cable laying method
Cable laying methods are as follows: direct burial laying, through the pipe laying, shallow groove laying, cable trench laying, cable tunnel laying, overhead laying several ways have advantages and disadvantages, generally take into account the urban development plan, the density of the existing buildings cable line length laying the number of strips and their impact on the surrounding environment, and so on. From the technical comparison, cable tunneling and cable trench laying way to facilitate the construction, maintenance and repair of the cable. In some developed cities, urban planning and construction, has considered the public tunnel. Practice has proved that public tunnels run well, greatly reducing the number of repeated investment and the phenomenon of repeated excavation of the road surface, but the initial investment is huge, construction materials cost gold, in the country, due to a variety of factors, the laying of this way is very little. In contrast, direct burial laying and shallow groove laying belongs to the economic type of laying, direct burial cable is the most economical and extensive Department of electricity laying, it is used in suburban areas and vehicle traffic is not too frequent place. But is not conducive to the maintenance and repair of the cable, once encountered cable failure, even if the use of a tester to measure the failure point, but also to re-excavate the cable trench, extremely inconvenient. Therefore, the choice of cable laying method, combined with the actual situation, according to engineering conditions, environmental characteristics, cable type and number of factors, with the development of vision, in accordance with the requirements of meeting the operational reliability, ease of maintenance and technically and economically rational principle of determination.
2. Cable selection
Commonly used power cables are oil-immersed cable, PVC-insulated cable, cross-linked polyethylene cables, etc., according to the use of different occasions, but also extends to different types of special cables. At present, with the continuous improvement of production technology and production process, cross-linked polyethylene cable has become the most widely used cable products, cable selection, should be based on the use of different environments and conditions, combined with the specific circumstances of the choice, minimize the crossing of a variety of pipeline railroads, highways and communication cables; such as the use of direct burial and shallow groove laying mode, should consider the use of steel armored cable.
3. Selection of cable cross-sectional area
Cable cross-sectional area of the choice, the relationship between the investment, line loss and voltage quality, the service life of the cable and so on. If the choice of cross-sectional area is small, will lead to voltage quality decline, line loss is too large, will make the initial investment is too high. Therefore, according to the results of load forecasting, development planning, select the appropriate cross-sectional area, so that the power cable to meet the maximum operating current under the core temperature requirements and voltage drop requirements, the maximum short-circuit current under the thermal stability requirements. Due to the high difficulty and low accuracy of load forecasting work, therefore, the selection of cable cross-sectional area, but also to meet the "urban low-voltage distribution network transformation technology guidelines" and "urban power network planning guidelines" requirements.
In the three-phase four-wire low-voltage power grid selection of power cables, but also consider the choice of the zero line cross-sectional area, in the public low-voltage network, due to the user factors have a greater impact on the three-phase load balance is difficult to control, in order to improve the quality of the voltage, reduce line losses, the zero line cross-section should be the same cross-section with the phase line.
4. About cable network and cable network automation
With the continuous promotion of power cables in the distribution network and the use of power distribution network can be divided into cable network and overhead network (including overhead, cable mixed network). On the "urban medium and low-voltage distribution network transformation technical guidelines" of the implementation of the "and supplemental comments" on the cable distribution network automation has also put forward specific requirements. Therefore, in the distribution network area network using cable network, should be in accordance with the requirements of power distribution automation, the use of new technologies, China Wire and Cable Network www.xianlan315.com new equipment, the conditions to consider automation pilot work, the conditions are not ripe for supporting equipment selection, consider a sufficient margin for the realization of automation programs to lay the foundation.
5. Power cable construction should pay attention to the problem
1), is the eddy current problem caused by high-current power cable
Power cable in construction, there are steel bracket, there are steel protection tube, there are cable cards and overhead laying, where the power cable around the formation of steel (iron) closed loop, are likely to form eddy currents, especially in the high-current power cable system, eddy currents are greater. In the construction of power cables, must take measures so that the cable can not form around the steel (iron) closed loop, to prevent the cable caused by eddy current phenomenon.
2), is the power cable turn caused by mechanical damage problems
As the outer diameter of power cables is large, transportation, laying is more difficult, power cables on the turning radius requirements are also more stringent. Power