The requirements for laying in the cable channel, what are the requirements for cable laying

Underwater laying of cables in cable channels belongs to cables.

National Standard GB50217-2007 "Code for Design of Electric Power Engineering Cables".

The regulations for underwater laying are:

Underwater laying. The selection of the underwater cable path should meet the requirements of the cable not being susceptible to mechanical damage, reliable protection, convenient laying operation, economic and reasonable, and should meet the following requirements:

1. The cable should be laid in the waters where the riverbed is stable, the flow rate is slow, the shore is not easy to be scoured, there are no obstacles such as rocky mountains or shipwrecks on the seabed, and there are few anchors and trawlers.

2. The cable should not be laid near the wharf, ferry, and hydraulic structures, and should not be laid in the dredging and dredging area and the planned port construction area.

Underwater cables should not be suspended in the water and should be buried underwater. In navigable waterways and other waters that need to be protected from external mechanical damage, the cable should be buried in a trench at an appropriate depth under the water, and should be firmly covered and protected; The buried depth in shallow water areas should not be less than 2m, and the buried depth of deep-water channels should not be less than 2m.

It is strictly forbidden to cross and overlap underwater cables. Adjacent cables should be kept at sufficient safety distance and should comply with the following requirements:

1. In the main channel, the cable spacing should not be less than the times of the average maximum water depth. The distance between the lead to the shore can be appropriately reduced.

2. In a small river with a non-navigable flow rate of less than 1 m, the spacing of single-core cables in the same circuit shall not be less than 5m, and the spacing of cables in different circuits shall not be less than 5m.

3. In addition to the above, it should be determined according to factors such as the flow rate of water and the buried depth of the cable.

The horizontal distance between the underwater cable and the industrial pipeline should not be less than 50m; When subject to conditions, it shall not be less than 15m.

The section of the underwater cable leading to the shore shall take protective measures suitable for the laying conditions, and shall comply with the following provisions:

1. When the shore is stable, the cable should be laid with protective pipe and trench, and the working well connection can be set up if necessary, and the lower end of the pipe trench should be placed at a place not less than 1m below the lowest water level.

2. When the shore is not stable, it is advisable to lay the cable in a roundabout form to reserve an appropriate spare length.

Conspicuous warning signs should be set up on both sides of the underwater cable.

1. The wire core and grounding wire are bundled by tinned copper single wire, and its performance and appearance should comply with the provisions of GB4910, and the pitch ratio of tinned copper wire bundle should not be more than 25 times.

2. The insulation layer is a mixture of high-voltage polyethylene and color masterbatch, and the insulation layer is tightly squeezed on the conductor, and it is easy to peel off without damaging the conductor, and the outer diameter of the insulation layer should conform to Table 1.

3. The color separation of insulated wire cores is: four cores (white-green, red-black), two-core (white-green), or multi-cores (attached).

4. The insulated wire has a shielding layer, and the shielding layer is made of thickness of aluminum-plastic composite tape wrapping shielding, which is a group of white and green, a group of red and black, and is shielded respectively, with a shielding rate of 100% and a wrapping overlapping rate of 10%.

5. After the insulated wire core is shielded, it is twisted together with the ground wire to form a cable, and the pitch ratio of the cable is not more than 14 times.

6. The outer sheath is tightly squeezed on the stranded core, and it is easy to peel off without damaging the insulated core. The surface of the outer sheath is flat, smooth, uniform in color, and there is no mechanical damage, and the outer diameter of the outer sheath should be in accordance with Table 1.

7. The finished cable can withstand the AC rated voltage 2000V test, and will not break down for 5 minutes.

8. The resistance of the insulated wire between each core and the ground wire of the finished cable should be in accordance with Table 1.

9. The finished cable can withstand the water pressure test, and under the condition that the water pressure at room temperature is 1MPa, it should be able to withstand pressure for 168 hours, and the measured value of the resistance of the insulated wire should not be reduced.

When the cable is fixed and laid, it is necessary to pay attention to the geological conditions, and choose the appropriate cable model and specifications, mainly to pay attention to the damage of rodent-proof, termite-proof, etc., depth, temperature, bending radius and other factors.

1. Armored cables should be used for underground directly buried cable lines. The buried depth of the cable should not be less than from the ground to the cable sheath; The foundation of the cable sheath to the underground building shall not be less than; The distance between cables is as follows: the minimum distance between cables in different departments when the level is close;

Minimum clear distance when cables cross each other; The net distance between the cable and the thermal pipeline, gas and oil pipeline is 2m when it is close, and the net distance when it crosses each other; The distance between the cable and the trunk of the tree is not less than.

2. There shall be no stones and other hard impurities in the directly buried cable trench, otherwise it should be paved with a 100mm thick soft soil or sand layer, and then a 100mm thick soft soil or sand layer will be laid on top of the cable after laying, and then covered with a concrete protection plate or brick, and the width of the coverage should exceed 50mm on both sides of the cable.

3. The directly buried cable should be worn in the protective pipe when entering the handhole well, manhole well, control box and power distribution room, and the nozzle should be made of waterproof plug. When crossing with urban roads and bridges, the protection pipe should be added, and the depth from the top of the protection pipe to the road surface should not be less than, and the two ends of the protection pipe should not be less than the lane.

When the cable is drawn from the ground to the ground, a section of protection pipe should be added to the ground, and the root of the pipe should be extended into the ground, and the protection pipe must be fixed firmly.

Requirements for laying cable lines in pipes and trenches:

1. The masonry of the cable trench should consider the segmented drainage, the bottom of the trench should have a good slope of scattered water, the cover plate of the ditch is generally covered with reinforced concrete, and the cable trench that often needs to be opened indoors is generally covered with steel cover plate. The entire cable trench should be equipped with a continuous grounding wire, and the two ends of the grounding wire and the grounding electrode are connected.

2. The cable laid on the bridge should be padded with a padding made of elastic material, and the cable slack part should be left at both ends of the bridge and the expansion joint to prevent the cable from being damaged due to structural expansion and contraction.

3. When the length of the cable through the protection pipe is less than 30m, the inner diameter of the straight section protection pipe shall not be less than the times of the outer diameter of the cable; When there is a bend, it is not less than 2 times; There are two bends when not less than times. When the length of the cable through the protection pipe is more than 30m, the inner diameter of the straight section protection pipe is not less than the times of the outer diameter of the cable.

Straight buried laying. In the area where the soil may be displaced, such as quicksand, backfill and accessories of large buildings and structures, steel wire armored cables that can withstand mechanical tension should be selected, or measures such as reserving lengths and reinforcing the soil with sheet piles or row piles should be taken to reduce or eliminate the stress on the cable due to soil displacement.

When the plastic cable is laid directly in the ground, when it may withstand greater pressure or there is a risk of mechanical damage in use, it should be selected with armor, and when there is no above situation, it is not necessary to wear armor.

--Manual, third edition, 488 pages.

The standards for directly buried compound cables are as follows:

1) The voltage level, model specification and path of the directly buried cable meet the design requirements, and the quality of the cable body is qualified.

2) The embedded depth of the cable should meet the following requirements:

The distance between the surface of the cable and the ground should not be less than 1m when crossing farmland, and the cable should be buried below the frozen soil.

In the cable into the building, and the underground building crosses.

3) In the cable path may cause the cable to be subject to mechanical damage, chemical action, underground current, vibration, thermal impact, humus, insects and other dangerous sections, should be in accordance with the requirements of the code to take protective measures.

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

1. Lay in the cable tray.

2. Lay along the steel cable.

3. Pipe laying.

4. Fix and lay along the wall with line cards.

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

Direct burial cable is in accordance with the requirements of the specification, after digging the direct buried cable trench, lay a sand cushion at the bottom of the trench, and remove the debris in the trench, and then lay the cable, after the cable is laid, it is necessary to fill the sand immediately, and cover a layer of bricks or concrete slabs on the cable to protect the cable, and then backfill a cable laying method.

The cable embedding depth shall meet the following requirements:

The distance between the cable surface and the ground should not be less. It should not be less than 1m when crossing farmland. Where the building is introduced, intersected with the underground building and bypassed the underground building, it can be buried shallowly, but protective measures should be taken.

The cable should be buried below the frozen soil, and measures should be taken to prevent damage to the cable when conditions are limited.

The minimum clear distance between cables, parallel and crossed between cables and other pipelines, roads, buildings, etc., shall comply with the provisions of the following table. It is strictly forbidden to lay the cable parallel above or below the pipe.

The upper and lower parts of the directly buried cable should be paved with a soft soil or sand layer not less than 100mm thick, and covered with a protective plate, the covering width should exceed 50mm on both sides of the cable, and the protective plate can be made of concrete cover or brick. There should be no stones or other hard debris in soft soil or sand.

Directly buried cables should be set up at 50 100m in straight sections, cable joints, turns, into buildings, etc., and obvious orientation signs or stakes should be set.

The main requirements for the laying of directly buried power cables are:

Directly buried cables should have armor and anti-corrosion protective layers.

The depth of the directly buried cable is generally not less than, not less than 1m in farmland, 35kv and above is not less than 1m, if the above requirements cannot be met, protective measures should be taken.

Directly buried cable should be evenly laid on the cable 100mm thick fine sand or soft soil, the upper side of the cushion should be covered with cement cover or brick connection, and bricks, stones and other debris should be removed when backfilling.

Directly buried cables should be set up with obvious azimuth markers at corners, joints, crossings, and in and out of buildings. Straight sections should be appropriately added with stakes. It is advisable to expose the stake 150mm above the ground.

When the cable passes through a place containing acid and alkali, slag, lime, etc., it should not be buried directly; When it is necessary to pass through the lot, anti-corrosion protection measures such as cylinder tile pipes and cement pipes should be adopted.

Directly buried cables should not be laid horizontally above or below various pipes;

When the cable is laid along the slope, the intermediate joint should be kept horizontal, and when multiple cables are laid in the same trench, the position of the intermediate joint should be staggered before and after.

When laying the cable, the cable should be prevented from spraining and excessive bending, and the ratio of the bending radius of the cable to the outer diameter of the cable should not be less than the following provisions: paper insulated multi-core power cable, lead clad 15 times, aluminum clad 25 times.

Before laying the power cable, check whether the model, specification and length of the power cable meet the design requirements and whether there is any external damage. Low-voltage power cables are used with a 1000V megohmmeter to measure the insulation resistance, and the insulation resistance value should generally not be less than 10m; High-voltage power cables are used with a 2500V megohmmeter to measure the insulation resistance, and the insulation resistance value should generally not be less than 400m.

1. The cable laying and installation should be carried out by qualified professional units or professionals, and the construction and installation that do not meet the requirements of the relevant specifications may lead to the normal operation of the cable system.

2. When laying cables by manpower, the rhythm of unified command and control should be unified, and there is a person carrying the cable on the shoulder every other meter, pulling while putting it and slowly putting it down.

3. When the cable is mechanically cast, a special cable laying machine is generally used and equipped with necessary traction tools, and the traction force is appropriate and evenly controlled, so as not to damage the cable.

4. When the cable is laid directly in the ground outdoors, the depth from the cable sheath to the ground should not be less, and the fine sand or soft soil with a thickness of 100mm should be evenly laid above and below the cable, and covered with concrete protective plate or similar protective layer.

5. The bending radius of the cable should be greater than the specified value when laying. Before and after the cable laying and installation, use a 1000V megohmmeter to measure whether the insulation resistance between the conductors of the cable is normal, and make appropriate corrections to the measurement results according to the different specifications, lengths and ambient temperatures of the cable, and whether the conductor is on or off should also be measured for small specifications (solid conductors below 10mm2).

6. If the cable is directly buried, it is necessary to pay attention to the soil conditions, and the buried depth of the cable under the general building is not less than meters, and the softer or the surrounding environment is more complex, such as cultivated land, construction sites or roads, etc., there should be a certain buried depth (meters) to prevent the direct buried cable from being accidentally damaged, and obvious signs should be erected if necessary.

7. In the soil with chemical corrosion or stray current corrosion, it is not allowed to use direct buried cables.

8. In cold areas, the cable should be buried below the frozen soil. When deep burial is not possible, measures should be taken to prevent damage to the cable.

Precautions for installing cable trays:

1.Before we choose the cable tray, we need to pay attention to the construction environment, in the selection of the cable tray that is suitable for the construction environment, if the cable tray we choose does not meet the environmental needs, then the cable tray will be seriously damaged by the environment after installation, and the entire line will be damaged.

2.Once the cable tray is installed, these requirements should be met when the main grounding circuit needs to be connected. The resistance connected at both ends of the cable tray should not be greater than ohms, and the grounding hole needs to de-energize the insulation layer.

When cutting off the power supply, the cross-sectional area in the direction of the size of the cable tray should not be less than the specified value.

3.When the fire protection requirements are required in the construction environment, the corresponding fireproof cable tray can be selected, and the overall fire performance requirements of the fireproof cable tray need to meet the requirements of the national light code or standard.

4.When you select a load class for a cable tray, the average load of the cable tray should not be greater than the rated average load of the selected cable tray. When the actual span of the cable tray support and hanger is not equal to 2m, the average working load should meet the requirements.

5.When the grounding trunk is laid along the full length of the bridge, at least part of the bridge (including non-straight sections) should be reliably connected to the grounding trunk.

6.When the grounding trunk is laid along the full length of the bridge, at least part of the bridge (including non-straight sections) should be reliably connected to the grounding trunk.

7.For the vibrating part, a spring coil should be installed at the connection of the grounding part.