Discussion on the selection, installation and layi

Brief discussion on the selection, installation and laying of wires and cables

according to the different laying conditions, general plastic insulated cables, steel tape armored cables, steel wire armored c/c-based composite materials can be selected, which are the most valued new materials with higher temperature resistance in recent years, such as cables, corrosion-resistant cables, etc

according to the safety requirements, non flame retardant cables, flame retardant cables, halogen-free flame retardant cables, fire-resistant cables, etc. can be selected

2. Selection of wire and cable specification

when determining the use specification (conductor section) of wire and cable, generally, heating, voltage loss, economic current density, mechanical strength and other selection conditions should be considered

according to experience, because the load current of low-voltage power line is large, the section is generally selected according to the heating conditions first, and then its voltage loss and mechanical strength are checked; Because of its high requirements for voltage level, low-voltage lighting lines can first select the section according to the allowable voltage loss conditions, and then check the heating conditions and mechanical strength; For high-voltage lines, the cross-section is first selected according to the economic current density, and then its heating conditions and allowable voltage loss are checked; The mechanical strength of high-voltage overhead lines should also be tested. If the user has no experience, white oil is also used as release agent; Relevant professional units or persons should be consulted

II. Installation and construction of wires and cables

the design and construction of wire and cable laying and installation shall be carried out in accordance with GB code for design of cables in electric power engineering and other relevant regulations, and necessary cable accessories (terminals and connectors) shall be used. The operation quality, safety and reliability of power supply system are not only related to the quality of wires and cables, but also related to the construction quality of cable accessories and lines

through the statistical analysis of line faults, the faults caused by factors such as construction, installation and connection are often much more likely than those caused by wire and cable body defects. Therefore, it is necessary to correctly select wires and cables and supporting accessories. In addition to the design and construction according to the requirements of the specifications, attention should also be paid to the following aspects:

1. The cable laying and installation should be carried out by qualified professional units or professionals. The construction and installation that do not meet the requirements of the relevant specifications may lead to the abnormal operation of the cable system

2. When laying the cable manually, the command and control rhythm should be unified. Every 1.5 ~ 3 meters, one person should carry the cable on his shoulder, pull it while laying it, and release it slowly

3. When laying cables mechanically, special cable laying machines are generally used and necessary traction tools are equipped. The traction force is appropriate and evenly controlled to avoid damaging the cables

4. Before laying the cable, check the appearance of the cable and whether the head is intact. Pay attention to the rotation direction of the cable reel during laying, and do not flatten or scratch the outer sheath of the cable. When it is low in winter, cut it in the case of stretching and the light is on. Do not straighten the cable by beating it, so as to avoid the insulation and sheath cracking

5. The bending radius of the cable should be greater than the specified value when laying. Before and after cable laying and installation, use a 1000V megger to measure whether the insulation resistance between the conductors of the cable is normal, and measure it according to the different cable model, specification, length and ambient temperature, and make appropriate corrections to the measurement results when the humidity increases. For small size (solid core conductor below 10mm2), also measure whether the conductor is on or off

⒍ if the cable is directly buried, pay attention to the soil conditions. Generally, the buried depth of the cable under the building is not less than 0.3m, and there should be a certain buried depth (0.7 ~ 1m) for the soft or complex surrounding environment, such as cultivated land, construction site or road, to prevent accidental damage to the directly buried cable, and obvious signs should be erected if necessary