Power cables are the medium of communication between power transmission equipment and power receiving equipment. The quality of the cable and the reliability of the cable connection directly affect the power transmission and the safety of the transmission and distribution equipment. Therefore, in the construction process, the quality control of power cable laying is also a focus of the supervision work.
1. Quality control of cable support and bridge access
In order to ensure the reliability of the quality of the cable support and bridge, the supervision engineer should focus on the following two points:
1. The specifications, models, bearing capacity, materials and corrosion resistance of cable brackets, bridges and accessories meet the design requirements;
2. The surface of the cable support, the bridge support device and the bridge is smooth and free of burrs, durable and stable, smooth in appearance, and free of rust.
2. Quality control during installation of cable support and bridge
1. The maximum allowable distance between two cable supports should meet the design requirements.
2. The cable support should be installed firmly, horizontally and vertically; the fixing method of the bracket support and hanger should be carried out according to the design requirements. The crosspieces of the same layer of each bracket should be on the same horizontal surface, and the height deviation is less than 5mm. The deviation of the bracket support and hanger along the rack direction should not be greater than 10mm. The cable support installed in the cable trench or building with a slope should have the same slope as the cable trench or building. The distance from the top and bottom of the cable support to the top of the trench, the floor, or the bottom of the trench, and the ground should meet the design requirements.
3. The vertical deviation of the assembled steel structure should be less than 2/1000 of the length; the horizontal error of the support cross brace should be less than 2/1000 of its width; the diagonal deviation should be less than 5/ of its diagonal length 1000.
4. The ladder frame (tray) should be firmly fixed on each support and hanger; the bolts of the ladder frame (tray) connecting plate should be tightened, and the nut should be located outside the ladder frame (tray). When the aluminum alloy ladder frame is fixed on the steel support and hanger, there should be measures to prevent electrochemical corrosion.
5. The turning radius at the turn of the cable bridge should be greater than the largest one of the minimum allowable bending radius of the cable on the bridge.
6. After the cable support is installed, ensure that the grounding is penetrated, and test that the grounding resistance is less than the requirements of national standards and specifications.
Third, the control of the quality of power cables entering the site
The supervisor first conducts quality control on the cable procurement process to ensure that the specifications and models of the power cables used in the project are consistent with the design drawings, the appearance of the cables should be free from damage, and the insulation should be good. When there is doubt about the sealing of the cables, a moisture judgment should be made, and Complete the "three certificates".
Fourth, the quality control of power cable laying
1. The cable channel is unblocked and well drained. The anti-corrosion layer of the metal part is complete.
2. The cable pay-off rack should be placed securely, and the strength and length of the steel shaft should match the weight and width of the cable reel.
3. Before laying, calculate the length of each cable according to the design and actual distance, and arrange the cable joints of each row reasonably.
4. Reliable safety measures should be taken for laying cables in live areas.
5. Quality control of cable connection production
(1) The whole connection process should be made strictly in accordance with the requirements.
(2) A spare length is reserved near the intermediate joint to provide convenience for maintenance in case of failure. Keep 1m at both ends of the middle joint
Both ends of the horizontal section should be fixed firmly.
(3) The two ends of the middle joint are equipped with steel armor, connected with soft copper wire, and tied to the steel armor with a copper wire of 2~3mm in diameter
And weld it firmly.
(4) The reserved length of the intermediate joint should be bent naturally and not less than the bend of the cable. Figure 5-3-2 Inside the tunnel
The radius of curvature, the curved part is not less than 2 cards to fix.
6. Quality control of cable joint arrangement:
(1) For cables laid in parallel, their joint positions should be staggered. Cable trench and machine room
(2) The cable connector on the bracket should be fixed with an insulating support plate, and the support plate should extend
7. Lay the cable on the corresponding support layer in strict accordance with the design requirements. The cable should be led out from the upper end of the tray, and the cable should not be dragged on the support or on the ground. Unremoved mechanical damages such as twisting on the cable and cracking of the protective layer;
8. The speed of mechanically laying cables should not exceed 15m/min.
9. When cables enter cable trenches, tunnels, shafts, buildings, panels (cabinets) and pipes, they will exit. 10. The net distance between cables and thermal pipes and thermal equipment should not be less than 1 when they are parallel. , Insulation protection measures should be taken.
11. When cables enter buildings, tunnels, through floors, outside walls, and other places that may be mechanically damaged, a protective tube with a certain mechanical strength or a protective cover should be installed.
12. There should be no water in the pipeline and no blockage by debris. When threading the cable, the protective layer must not be damaged, and non-corrosive lubricant (powder) can be used; the cable duct should be dredged before laying the cable to remove debris; the cross-section of the cable inserted into the pipe should meet the design requirements. 13. At the bend, be sure to ensure that the bending radius meets the relevant requirements.
14. After the cable is laid, the debris should be removed in time and the cover should be covered. If necessary, seal the cover gap.
15. Quality control of cable fixing point position:
(1) For cables laid vertically or inclined at an angle of more than 45°, the spacing between brackets or bridges is less than 2m;
(2) For cables laid horizontally, brackets or bridges should be provided at the first and last ends, turns and both ends of the cable joint;
(3) The cables laid along the roof of the tunnel shall be fixed firmly with rigid clips, and the distance between them shall not be greater than 1m.
Five, power cable test
After the power cable is laid, in order to ensure the safety of power transmission, the construction contractor must perform insulation resistance measurement, DC withstand voltage test, leakage current measurement and check the phase and connection of the cable line in accordance with the requirements of national and industrial standards and regulations. Supervision engineer Supervise the entire test process and approve the test results on site.