Cables are arguably the foundation of our lives. Without them, households wouldn't enjoy the convenience of electricity as they do today. To enhance understanding of cables, this article will introduce their safety requirements, protection measures, and storage methods. If you're interested in cables, please read on.
I. Cable Safety Requirements
1. When cables cross each other, the high-voltage cable should be below the low-voltage cable. If one of the cables is protected by a conduit or separated by a partition within 1m before and after the crossing point, the minimum allowable distance is 0.25m.
2. When cables are close to or cross heating pipes, if there are insulation measures, the minimum distances for parallel and crossing cables are 0.5m and 0.25m, respectively.
3. When cables cross railways or roads, they should be protected by conduits, and the protective conduits should extend more than 2 meters beyond the rails or road surface.
4. The distance between the cable and the building foundation should be sufficient to ensure that the cable is buried outside the building's drainage system; when the cable is introduced into the building, it should be protected by a conduit, and the protective conduit should also extend beyond the building's drainage system.
5. The distance between cables directly buried underground and the grounding of general grounding devices should be 0.25~0.5m; the burial depth of cables directly buried underground should generally not be less than 0.7m, and should be buried below the frost layer.
II. Cable Protection Measures
With the rapid development of underground power cable laying projects, higher requirements have been placed on cable protection. Cable protection conduits are made of polyethylene (PE) and high-quality steel pipes through pretreatment processes such as sandblasting and shot blasting, dip coating or painting, and heat curing. It is one of the most commonly used electrical insulation conduits for protecting wires and cables. It is widely used due to its excellent insulation performance, high chemical stability, rust resistance, non-aging properties, and adaptability to harsh environments.
Using cable protection conduits to protect cables offers the following advantages: 1. Excellent corrosion resistance and long service life; suitable for use in humid and saline-alkali areas. 2. Good flame retardancy and heat resistance; can be used for extended periods at 130 degrees Celsius without deformation and does not burn when exposed to fire. 3. High strength and rigidity. Direct burial under roadways eliminates the need for a concrete protective layer, accelerating cable construction progress. 4. Both the conduit material and fittings possess a degree of flexibility, resisting damage caused by external pressure and foundation settlement. 5. Excellent resistance to external signal interference. 6. Smooth inner wall prevents cable scratches. The design employs a socket-type connection method for easy installation. Rubber sealing rings at the joints accommodate thermal expansion and contraction while preventing the ingress of mud and sand.
III. Cable Storage Methods
If cables are to be stored for a long period of time, the following considerations should be taken into account depending on the location of the cables:
1. Under the eaves. Standard LAN cables can be used as long as they are not directly exposed to sunlight or extremely high temperatures; it is recommended to use conduits.
2. On the exterior walls. Avoid direct sunlight and human-caused damage to the walls.
3. Inside pipes (plastic or metal). If inside pipes, be aware of potential damage to plastic pipes and the heat conductivity of metal pipes.
4. Suspended/Aerial Cables. Consider cable sag and stress, the intended bundling method, and whether the cable will be exposed to direct sunlight.
5. Laying cables directly in underground trenches offers the least control over the environment. The cable trench installation requires regular checks to ensure it is neither too dry nor too damp.
6. Underground Pipelines. For future upgrades, cable replacements, and isolation from surface pressure and the surrounding environment, laying underground pipelines is a good method. However, don't expect the pipelines to remain dry forever, as this will affect the selection of cable types.
IV. Cable Quality Identification
How to distinguish between good and bad quality electrical wires when purchasing them
The state has mandated the use of copper wires in newly constructed residential buildings. However, even among copper wires, there are inferior products. These inferior wires use recycled copper for their cores, containing many impurities. Some even have lower conductivity than iron wire, posing a significant risk of electrical accidents. The market offers a wide variety of wire types, specifications, and prices, making it difficult for consumers to choose. For example, the price of a single roll of 2.5 square millimeter and 4 square millimeter copper core wire, commonly used in home renovations, can vary by 20% to 30% depending on the manufacturer. Furthermore, consumers often find it difficult to determine the quality or whether the length meets standards.
Industry insiders revealed that the significant price differences in electrical wires are due to the different raw materials used in the production process. The main raw materials for producing electrical wires are electrolytic copper, insulation materials, and sheathing materials. On the raw material market, electrolytic copper costs around 50,000 yuan per ton, while recycled copper costs only around 40,000 yuan per ton. High-quality insulation and sheathing materials cost between 8,000 and 10,000 yuan per ton, while substandard products only cost 4,000 to 5,000 yuan per ton, a much larger price difference. In addition, insufficient length and inadequate adhesive content in the insulation are also important reasons for the price differences. Each spool of wire is 100 meters long for superior products, while substandard products are only about 90 meters long; the adhesive content in the insulation of superior products is 35% to 40%, while that of substandard products is only 15%. Through this comparison, consumers can easily see that the price differences in finished electrical wires are due to discrepancies in the materials used.
