What Is a Direct-Buried Cable?

Direct burial cable is in accordance with the requirements of the specification. After digging the direct buried cable trench, lay a sand cushion on the bottom of the trench and remove debris in the trench, and then lay the cable. After the cable is laid, you must fill the sand immediately. A cable laying method is to cover the cable with a layer of brick or concrete slab, and then backfill the cable.

Buried cable

Right!

Direct burial cable is in accordance with the requirements of the specification. After digging the direct buried cable trench, lay a sand cushion on the bottom of the trench and remove debris in the trench, and then lay the cable. After the cable is laid, you must fill the sand immediately. A cable laying method is to cover the cable with a layer of brick or concrete slab, and then backfill the cable.

In addition to direct buried cables, there are the following common cable laying methods:

1.Lay in the cable tray

2.Lay along the steel cable.

3, laying pipe.

4.Fix it along the wall with a line card.

5.The cable trench (tunnel) is laid along the cable support.

1.1 Purpose: In order to standardize the construction of cable line sub-projects, promote the progress of construction technology, and ensure the quality of construction, develop this construction process standard. 1.2 Scope of application: This process standard is applicable to the construction work of the cable circuit sub-item of the building electrical branch in the industrial and civil building installation engineering. For special site construction operations that have special professional requirements, it should be carried out in accordance with regulations.

1.3 Construction Operation Conditions 1.3.1 The construction technical documents related to sub-items shall be complete and valid, such as construction drawings, minutes of review of construction drawings, construction organization design, quality plan, process evaluation standards, and related technical standards, specifications, standard drawings, etc.

1.3.2 The operators involved in the construction shall have the corresponding qualifications for construction technology, and when necessary, adaptive training for the construction operation shall be arranged so that those who pass the assessment can be permitted to take up jobs. 1.3.3 The performance of the equipment to be used in this construction operation must meet the requirements of construction characteristics, and the operation is safe and reliable. The range and accuracy of the measuring instrument used for testing shall meet the requirements of the measurement object, and within the prescribed regulatory inspection cycle.

1.3.4 Construction environment

(1) The buried cable trench is controlled according to the construction drawings, and its depth should meet the requirements of the specification. The bottom sand is paved and there is no debris in the trench. (2) The laying of cables should be carried out without rain, and the temperature should be above 0 . 2.Operating process 2.2

2.2.1 Preparations (1) Conduct detailed inspection of cables used in construction projects, and their models, voltages, specifications, etc. should be consistent with the design of the construction drawings; the appearance of the cables should be free of distortion, damage, oil leakage and oil leakage. (2) The cable should be tested for insulation resistance or withstand voltage. a. For 1KV and below cables, use a 1000V megohmmeter to measure the insulation resistance between the wires and the ground should not be less than 10M.

b. 6-10KV cables shall be tested for insulation resistance, DC withstand voltage and leakage. The test standards shall comply with national standards. c. Oil-paper insulated cables. Those who fail the test should check whether the core wire is wet. If it is wet, it can be sawed off for a while and then tested until it passes. The inspection method is: peel off a piece of insulation paper of the core wire, and light it with fire. If a bang sound is made, the cable has been damp.

d. After the cable test is completed, the oil-paper insulated cable should be sealed with solder (lead-tin alloy) immediately. Other cables should be sealed with rubber and plastic materials. (3) Calculate the length of each cable according to the design and actual path, arrange each cable reasonably, and reduce cable joints.

(4) The cable protection tube required for the cable line shall be processed and placed on site. The processing of the cable protection tube should meet the following requirements: The nozzle should be free of burrs and sharp edges, and the nozzle should be made into a horn shape. After the cable tube is bent, there should be no cracks and notches; the bending radius of the cable tube should not be less than the minimum allowable bending radius of the cable. Metal pipes should be painted with anticorrosive paint or asphalt. (5) The cable pay-off stand should be placed securely, and the strength and length of the steel shaft should match the weight and width of the cable reel. 2.2.2 Cable laying (1) Cable laying can be manually pulled or mechanically towed. The maximum traction strength of the machine should meet the requirements of Table -1, its speed should not exceed 15m / min, and a twist preventer should be installed between the traction head or wire mesh sleeve and the traction steel cable.

Cable maximum traction strength (N / mm2) Table-1

Traction method: Traction head, steel wire mesh sleeve, copper core, aluminum core, lead sleeve, aluminum sheath, plastic sheath, allow traction strength. (2) When the cable is laid, the cable should be pulled out from the upper end of the disk, and the cable should not be dragged by friction on the ground. The cable must not have unremoved mechanical damage such as squashing of the armor, twisting of the cable, or cracking of the sheath.

(3) The bending radius of the cable shall meet the requirements of the specification. Appropriate serpentine bends shall be laid in the trench. Appropriate residual changes shall be left at the two ends of the cable, at the intermediate joints, at the pipe, and at the vertical offset.

(4) The minimum clear distance between cables and between other cables: roads, buildings, etc. in parallel and crossing shall meet the requirements of the code. (5) When laying the cable in winter, if the temperature does not meet the requirements of the specification, the cable should be heated in advance. (6) The cable laying system should be equipped with a communication and command system. It is advisable to communicate with a radio intercom and hold the speaker. 2.2.3 Sand-covered bricks (1) After the cable is laid, the construction unit, supervision and quality supervision department shall be required to make a hidden project acceptance, make a record and sign. (2) The top of the cable is the same as the bottom of the cable, covered with 10cm of sand or soft soil, and then covered with a brick or cable cover. The width of the cable should exceed 5cm on both sides of the cable.

2.2.4 Backfilling (1) Before backfilling for directly buried cables, they shall pass the concealed engineering acceptance.

(2) Backfill soil should be compacted in time and in layers. 2.2.5 Buried Standard Pile

Cables should be marked with obvious azimuth piles at turns, joints, crossings, and in and out of buildings. Appropriately spaced path marking piles shall be installed at every 50-100 points of the straight line of the cable. The stake should be firm and the sign should be clear. It is advisable that the stake should be 15cm above the ground.

2.3 Standards to be achieved by quality inspection and testing instruments and methods 2.3.1 Standards to be achieved by quality inspection and inspection (1) The voltage level, model specifications and path of the buried cable meet the design requirements, and the quality of the cable body is acceptable.

(2) The buried depth of the cable should meet the following requirements: The distance between the cable surface and the ground should not be less than 0.7m, and it should not be less than 1m when crossing farmland, and the cable should be buried below the frozen soil layer. When the cable is introduced into the building, intersects with the underground structure, and bypasses the underground structure, it may be shallowly buried, but protection measures shall be taken. (3) Protective measures shall be taken in accordance with the requirements of the code on the cable route where the cable may be subjected to mechanical damage, chemical action, underground current, vibration, thermal influence, humus, pests and other dangerous areas. 2.3.2 Testing instruments and testing methods

(1) Detection of insulation resistance: ZC type megohmmeter (2) Suitable current withstand voltage and leakage test: High voltage test equipment 2.4 Safety production, civilized construction requirements and measures

(1) Construction personnel should wear safety helmets and canvas gloves. During the construction process, they should concentrate their energy, obey the command, obey dispatch, and ensure safe production. (2) The excavation of cable trenches until the completion of backfill soil shall be carried out in a balanced and continuous manner as much as possible to shorten the construction period; for construction in places with pedestrians, there shall be a warning sign after excavation of cable trenches and a red light at night. 3. The quality record adopts the hidden engineering record form.

4.Appendix

Related technical specifications and standards:

"Code for Construction and Acceptance of Cable Installation of Electrical Installation Engineering" "Standard for Handover Test of Electrical Equipment for Installation of Electrical Installation" "Code for Acceptance of Construction Electrical Engineering Construction Quality"