There are generally four ways to lay cable lines: direct buried cable laying, pipe cable laying, cable trench or tunnel laying, and bridge cable laying. The construction requirements for these four laying methods are summarized as follows:

   1. Direct buried cable laying requirements

   1. The bottom of the excavated ditch must be a soft soil layer. If it is stone or hard debris, a 100mm thick soft soil or sand layer should be laid. If the soil around the cable contains corroded cable metal sheath, it should be removed and replaced. The buried depth should not be less than 0.7m, and it should not be less than 1m when crossing the farmland. Shallow burial can be used at places leading in buildings, intersecting with underground buildings, and bypassing underground buildings, but protective measures should be taken. Cables should be buried below the frozen soil layer. When conditions are limited, precautions should be taken to prevent cables from being damaged. measure.

   2. After the cable is laid, it should be covered with 100mm thick soft soil or fine sand, and then covered with a concrete protection board. The coverage width should exceed 50mm on both sides of the cable, or use bricks instead of the concrete protection board.

   3. There must be a cast iron or concrete protective box outside the intermediate joint box.

   4. A concrete base plate should be placed under the joint, and the length should extend 600~700mm from both ends of the joint protection box. When the cable is introduced into the tunnel, manhole and building from the soil ditch, it must be passed through the pipe and the mouth of the pipe should be blocked. Prevent water seepage.

   5. Cables cross each other, cross non-thermal pipes and pipes, and when crossing roads and walls, they must be worn in protective tubes. The length of the protective tube exceeds the intersection point by 1m. The crossing clearance should not be less than 250mm, and the inner diameter of the protective tube should not be less than 1.5 times the outer diameter of the cable.

   6. Directly buried cables generally use armored cables. Both ends of the metal sheath of the armored cable must be reliably grounded, and the grounding resistance shall not exceed 10Ω.

   7. Directly buried cables should be provided with obvious azimuth signs or stakes at every 50-100m in the straight line, at the cable joints, at the turns, at the places where they enter buildings, etc.

   8. The minimum clear distance between the cable and other pipelines, roads, buildings, etc. when parallel and crossing shall comply with the regulations. It is strictly forbidden to lay cables in parallel above or below the pipeline.

   2. Requirements for pipe and cable laying

   1. Cable pipe laying

   1) Cable pipes can be made of steel pipes, plastic pipes, ceramic pipes, asbestos cement pipes or concrete pipes, but the inside of the pipes must be smooth;

   2) Arrange the pipes into a certain form according to the number of holes required, the pipe joints should be staggered, and poured with cement to form a whole, generally divided into 2, 4, 6, 8, 10, 12, 14, 16 holes and other forms;

   3) The aperture should generally not be less than 1.5 times the outer diameter of the cable, the aperture of the pipe for laying power cables should not be less than 100mm, and the aperture of the control cable should not be less than 75mm;

   4) The distance from the top of the buried underground pipe to the ground should not be less than 500mm on the sidewalk; it should not be less than 700mm in general areas;

   5) Pipeline cable wells should be installed at the straight-line distance of more than 100m, at the turn and branch of the pipe; the pipe leading to the well pit should have a slope of not less than 0.1%, so that the water in the pipe can flow into the well pit;

   6) The cables laid in the pipes shall be armored cables.

   2. Cable protection pipe laying

   Where cables enter buildings, tunnels, pass through floors and walls, lead from the ground to electric poles, equipment, the outer surface of walls or places easily accessible by pedestrians, a section below 2m above the ground, and other places that may be mechanically damaged should have A protective tube with a certain mechanical strength or a protective cover is installed. The depth of the protection pipe buried in the non-concrete ground shall not be less than 100mm, the length extending out of the water slope of the building shall not be less than 250mm, and the root of the protection cover shall not be higher than the ground.

   3. Cable laying requirements in cable trenches or tunnels

   1. Arrangement of cables

   1) Power cables and control cables should not be arranged on the same layer of support;

   2) High and low voltage power cables, strong current and weak current control cables should be arranged in layers in order, generally from top to bottom; but when cables with voltages above 35kV are introduced into the cabinet, in order to meet the bending radius requirements, they can be arranged from bottom to top configuration.

   2. The cable is laid on the bracket

   1) The control cable should not exceed 1 layer on the ordinary support; it should not exceed 3 layers on the bridge.

   2) AC three-core power cables should not exceed one layer on ordinary supports and hangers, and should not exceed two layers on bridges.

   3) AC single-core power cables should be arranged on the same side brackets, and when arranged in a close-fitting equilateral triangle, they should be fastened with straps every lm.

   4) For cables laid side by side, the clear distance between them should meet the design requirements.

   5) The net distance between cables, thermal pipes and thermal equipment should not be less than 1m when laid in parallel, and heat insulation protection measures should be taken when conditions are limited.

   6) After the cable is laid, the debris should be removed in time and the cover should be covered. Cover gaps should also be sealed if necessary.

   Fourth, cable laying requirements

   1. Anti-corrosion treatment should be carried out on the bridge frame. Generally, the surface of the bridge frame should be galvanized, plastic-plated, coated with oxidized resin, and painted. In a highly corrosive environment, the bridge frame can be made of corrosion-resistant materials such as aluminum alloy, plastic, and low-standard stainless steel.

   2. Cables can be laid in a single layer on the pallet. Small cables can be fixed on the pallet with plastic straps, and large cables can be fixed with metal clips.

   3. Set up a support and hanger every 1.5~3m in the horizontal section of the bridge frame; set up a support every 1~1.5m in the vertical section; set up a support and hanger at 1m from both ends of the tee, cross, and elbow. shelf.

   4. When the bridge frame passes through the expansion joints of the building, the distance of 100~150mm should be disconnected, and the two ends of the distance should be grounded and bridged.

   5. The installation of the bridge frame should be conducive to the insertion and release of cables. After the bridge frame is installed, it should be straightened, and the bridge frame should be fixed on the bracket with pressing pieces.

   6. The length of the supports and hangers supporting the bridge should be consistent with the width of the bridge, and there should be no difference in length.