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laying underground cable requirements

Release time:2017-08-04 11:08 hit:


laying underground cables
laying cable underground
 
Unlike elevated overhead lines, underground cables are often laid in cable trenches, tunnels, pipes or indoors. After entering the modern society, due to the urban land shortage, traffic pressure, city building and other reasons, the underground cable transmission mode is widely adopted in big cities. Relative to the overhead cable, has the advantages of small occupation, reliable transmission, strong anti-interference ability etc.
 
Basic requirements for underground cables
 
1. After cable laying must be megger insulation resistance with 500 volts, generally not less than 10 megohm.
 
2. The cable core shall be connected by round sleeve. The casing is generally divided into copper tube and aluminum casing, crimping copper tube copper core cable, copper sleeve is made of copper containing more than 99.9% of the copper pipe, wall thickness not less than 1mm, the length is 8-10 times the diameter of the casing; crimping aluminum casing aluminum core cable, aluminum aluminum casing wall thickness should be not less than 99.6%. Not less than 1.2mm, the length is 8-10 times the diameter of the casing of the same; if the cable is connected to the copper core and aluminum core cable should be used, and the need of copper aluminum transition joint, copper aluminum transition joint with wire crimping before annealing.
 
3, in the joint of buried cable lines and corners must set the hand hole wells or pegs, for ease of maintenance and inspection, hand hole spacing should be less than 50m.
 
4, in cable trench, hand hole wells and into the control box, cable distribution cabinet and head joints, the terminal shall be equipped with cable cable specifications, record the name of the line or loop number indicator.
 
5. The middle head or terminal head of the cable connection must be sealed and waterproof. The cut off cable line can not damage the core insulation sheath of cable. The construction of each cable line shall have an original record of construction, including: cable type, specification, length, date of installation, numbering of intermediate joint and terminal head. The benefits of doing so is to prevent the change and modification of cable lines, cable lines and ground survey to facilitate maintenance of each line underground cable change, should promptly correct the corresponding technical information and cable signs, ensure the accuracy of the data line.
 
Requirements of buried underground cable line:
 
1, underground cable lines should be used like armored cable. The buried depth of the ground to the cable sheath cable should be not less than 0.7m; cable sheath to the underground buildings, not less than 0.3m; distance between cable: close to the level of minimum 0.1M distance between different departments, cable 0.5m cable cross each other; the minimum net distance 0.5m; cable and heating pipeline, gas and oil pipeline near when the spacing is 2m, when the intersection spacing is 0.5m; and the trunk cable distance not less than 0.7m.
 
2, buried cable trench shall not have stones and other hard impurity, otherwise it should be covered with 100mm thick soft soil or sand, after cable laying above the spread to 100mm thick soft soil or sand, and then covered with plates or slabs of concrete protective cover, width should be beyond the cable on both sides of the 50mm.
 
3, buried cables enter the hand hole wells, Manholes, control box and distribution room should wear the protective tube, and the nozzle should be waterproof plug. And urban roads, bridges and other cross should be increased when the protection pipe, protection pipe top to the depth of the road is not less than 0.7m, the protection pipe at both ends of the road is not less than 0.5m. When the cable is pulling out of the ground, the ground shall be provided with a protective tube of 2.5m. The root of the pipe shall be extended into the ground 0.2m, and the protective tube shall be firmly secured.


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