Cable laying methods, 20 common problems

What should be paid attention to when laying directly?

For direct buried laying, it is necessary to consider whether the cable is susceptible to damage caused by external impact.

1. If there is no big impact, it is possible to lay it directly.

2. If it is possible to receive some relatively large impacts, but the strength can be controlled within a certain range, you can consider armored direct burial.

3. If the external force is greater, it is necessary to use a protective sleeve, which can be set locally (such as a place through a highway).

Advantages and disadvantages of direct buried cable laying
Advantages: easy to lay, saving materials and labor,
Disadvantages: maintenance is inconvenient. If maintenance is required, the overburden needs to be excavated. It is only recommended to use in places where maintenance is not considered or can be accepted. Generally, yellow sand is required for direct burial.

Question 1
Directly buried cables are grounded, how to find the fault point?
Answer: Use the patrol cable tester.

Question 2
Do cable wells need to be built for directly buried cables?
Questions added: Cable laying in the factory area is directly buried with armored cables. Do you need to add cable wells at crossings and entering the power distribution room of the workshop? Is it necessary to add cable wells when municipal 10KV cables enter the factory?

Answer: Cable wells are not required for cables with 6 or less. There are many wells for cables, which is easy to replace and add cables. The municipal 10KV cable does not need to set up a cable well when it enters the factory area, it can be directly buried from the terminal pole to the high-voltage power distribution cabinet.

Question 3
How to lay temporary cables on site?
Supplement to the problem: The unit builds a new factory building, and the transformer and high-voltage line are far away from the construction center. Because it is a steel structure factory building, overhead lines cannot be used to avoid conflicts with steel structure installation. Only low-voltage cables can be used to lead from the transformer to the construction site. Class-level distribution box, and then allocated to the second-level distribution box of each construction unit on site. How to lay this section of low-voltage cable? Is it buried directly or placed directly on the ground?

Answer: It is strictly forbidden to lay directly on the ground. This low-voltage cable is directly buried.

What should I pay attention to when laying through a pipe?

Compared with direct burying, cable laying through pipes is more convenient for later maintenance and adding lines. For cables laid through pipes, some spare pipes can be considered to prepare for future line maintenance and capacity expansion.

1. When laying through pipes, it is necessary to consider setting up cable wells when the turning angle of the line is large or the distance of the straight section is long.

2. When the number of cables is small and the wire diameter is small, the cable hand well can be used;

3. In the case of more cables and larger wire diameters, it is necessary to consider setting up cable manholes. The cable well can be done in accordance with the atlas. In addition to the atlas approach, many small passage wells can also be directly built by brick or concrete. At this time, it is necessary to consider setting up water seepage holes at the bottom.

4. There are more pipes that wear pipes, such as cast iron pipes, steel pipes, polyethylene pipes, nylon pipes, carbon pipes, etc., which can be selected according to needs. Pay attention to the influence of eddy current when single-core cables pass through metal pipes.

What should be paid attention to when laying pipes?

Pipe laying is mainly used in areas with more lines and concentrated routes. Relatively speaking, pipe laying is more convenient and saves materials.

Question 1
Is it one row of pipes, one cable, or multiple cables for laying cables in the outdoor row of pipes?
Answer: Each tube should only wear 1 cable. Except for important places such as power plants and substations, for all circuits of a motor or all circuits of a low-voltage motor of the same equipment, no more than 3 power cables or multiple control cables can be combined in each tube. For details, see GB 50217-2007 P32 5.4.4.

Question 2
What should I do if the laying depth of the pipe is not enough?
Question supplement: How to bury cable ducts on the ground less than 1m thick? Below is the basement. The ceiling of the basement is only 70 to 80 cm thick, and the well depth is 1.3 meters?

Answer: If in an area with no vehicles, the buried depth should not be less than 0.5m (the cable specification requires 0.5m, and the civil code requires 0.7m. Here, the cable specification shall prevail). If there are more vehicles passing, you can add a protective plate on the pipe. Or use thick-walled steel pipes for laying or use cable trenches. If the roof of the basement has only 70-80 cm of soil, the depth of the well should be 1.3m to lower the roof, but this is of little significance, because the drainage problem of the cable well is difficult to solve, and few people pay attention to it.

Question 3
Is there a problem with the laying of strong current pipes and weak current pipes?
Question supplement: There is an external line in the factory area, there are more than a dozen low-voltage high-voltage cables, and there are also weak-current (TV, telephone, network) cables. There are more than 8 high-current cables, and they cannot be buried directly. Laying. But now there is a problem, that is, the weak current is also laid through the pipe, so can the strong current tube and the weak current tube be kept in line?

Answer: Try not to line up together. When doing small municipal administration, try to install strong and weak electric pipes on both sides of the road. If there is occasional crossing, it is recommended to implement it in accordance with the specification spacing requirements. You can refer to the atlas, such as the laying of underground communication cables 05X101-2.

Question 4
Outdoor cable concrete pipe laying?
Question supplement: When drawing the general plan, all outdoor cables shall be laid with concrete pipes at the request of Party A. After consulting the atlas (94D164), the following problems were found:
1. Due to the influence of other pipelines on site, except for straight wells, the cable piping work manhole wells cannot be in accordance with the size shown in the atlas. I wonder if there is any reasonable solution?
2. Regarding the drainage problem in the manhole well. According to the requirements of the civil regulations, a sump must be set in the manhole, but I don’t know what method to use for centralized drainage.
3. The spacing of manhole wells is 150m according to the specification, while the atlas is 50m. I don't know which one shall prevail, but there are still other regulations.
4. Are there other atlases for reference? In addition to standard wells, can you design the shape and size of the well by yourself?
5. What matters should be paid attention to during the design and construction of this laying method.

Answer: 1. Non-standard wells can be designed according to needs;
2. For drainage in the well hole, if it is possible to install a drainage pump, a drainage pump should be installed. If there is no way to install a drainage pump, set up an overflow hole at the bottom of the sump. Don't seal it with concrete, let the water penetrate naturally. , But it depends on the local groundwater level;
3. I usually consider the spacing of manhole wells according to 50~70;
4. I personally think that it is not necessary for small municipal power distribution to build wells in accordance with the requirements of the atlas, just non-standard;
5. Concrete piping has not been done before, but please refer to GB50217-2007 P32 5.4.6 for the precautions and requirements for using piping.