Cable laying requirements and how to deal with cable laying thermal expansion and contraction

**What Are the Requirements for Cable Laying?** Before laying cables, it's essential to verify that the model and specifications meet the required standards. The insulation should be in good condition, with no visible damage or defects on the surface. In a three-phase four-wire system, using a three-core cable alone is not recommended. Instead, a single-core cable or a metal-sheathed cable should be used as the neutral conductor. This helps maintain electrical balance and safety. When multiple power cables are laid in parallel, they should have the same length to ensure even current distribution and prevent overheating. Spare lengths must be reserved near cable terminations and at intermediate points. For buried cables, these spare sections should be laid in a wavy pattern to allow for flexibility and movement. The spacing between supports should follow the design specifications. If no specific guidelines are provided, the maximum distance between supports should not exceed 1 meter for horizontal installations, 2 meters for vertical runs, and 0.75 meters for suspended cables. The bending radius of the cable should not be less than 10 times the outer diameter of the cable, especially for armored or non-armored multi-core plastic-insulated power cables. During installation, the cable should be pulled from the top of the reel to avoid friction against brackets or the ground, which could cause damage. Cables should not cross each other during installation. They should be neatly arranged, properly secured, and clearly labeled with identification tags. At corners where buried cables change direction, sturdy stakes should be placed to prevent shifting and potential damage. When cables enter trenches, tunnels, buildings, or pipes, the entry points must be sealed properly. Additionally, any fixtures used for single-core cables should not form a closed magnetic circuit with iron components, as this can cause unwanted electromagnetic interference. **How to Handle Thermal Expansion and Contraction During Cable Installation?** To minimize thermal expansion in large-section cables, split conductors are often used. This not only reduces core losses but also generates lower thermo-mechanical forces per unit area. The design of cable accessories must account for these forces to prevent damage. There are two main types of cable sheathing: aluminum and aluminum alloy. Aluminum sheathing offers better performance compared to aluminum alloy, making it more suitable for most applications. For directly laid cables, a serpentine (wavy) layout near the terminal can help absorb thermal expansion and reduce end thrust. These cables should be rigidly fixed at the support brackets to prevent displacement that could damage the termination. When installing large-section cables in conduits, bentonite can be used to fill the conduit, reducing the risk of bending or deformation. The conduit exit should be securely fastened, and both sides of the cable joint must be rigidly fixed to protect the connection. In tunnels, cables can be laid in a serpentine pattern to accommodate thermal expansion and contraction. When installed on slopes, cables must be fixed in place, and the cables on either side of the joint should also be rigidly secured to ensure the joint remains safe and intact. By following these guidelines, you can ensure a safe, efficient, and long-lasting cable installation that meets all technical and safety requirements.

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