1. What should we pay attention to when burying directly? Under what circumstances
In direct burying, it is necessary to consider whether the cable is vulnerable to external force impact and lead to damage.
1. if it is not greatly affected, it can be laid directly.
2. if it may be affected by a large extent, but the strength can be controlled within a certain range, the direct burial of armor can be considered.
3. if the external force is large, the casing shall be protected. You can set up locally (for example, where you pass a road).
Advantages and disadvantages of direct embedded cable laying:
Advantages: easy to lay, saving materials and labor,
Disadvantages: inconvenient maintenance. If maintenance is required, the overlay needs to be excavated. Only recommended where maintenance is not considered or acceptable. When buried directly, yellow sand must be placed on it.
Question 1. how to find the fault point of buried cable grounding?
A: use cable tester.
Question 2 does the cable well need to be buried directly?
Problem added: cables laid in the plant area are buried directly with armored cables. Are cables required at the intersection of the workshop and in the distribution room? Is it necessary to add cables to municipal 10kV cables entering the plant area?
A: cable tray cannot be set for 6 or less cables, and more cable trays are set, which is convenient for replacing and adding cables. Municipal 10kV cable can be directly buried in high voltage distribution cabinet from the terminal post when it enters the factory without good cable.
Q3 how to lay temporary cables on site?
Problem supplement: the new plant of the unit, the construction transformer and high voltage line are far away from the construction center. Because of the steel structure workshop, overhead lines cannot be used to avoid conflict with the installation of steel structure. Only primary distribution boxes leading from transformers to construction sites through low voltage cables can be used and then distributed to secondary distribution boxes of each construction unit on site. How to lay low voltage cables? Is it buried directly or directly on the ground?
A: it is strictly forbidden to lie on the ground directly. Low voltage cable is laid directly.
2. What should be paid attention to when piping? Under what circumstances
Compared with direct burial, the ACSR Cable is more convenient to maintain and increase the line in the later stage. For cables laid through pipes, some spare pipes may be considered to prepare for future maintenance and increase of line capacity.
1. when laying pipelines, cable wells shall be considered when the turning angle of the conductor is large or the distance of straight section is long.
2. cable shaft can be used for the number of cables and the diameter of cable is small.
3. if there are many cables and large diameter, cable manholes shall be considered. Cable wells can be carried out according to the atlas. In addition to the atlas method, many small intersections can also be placed directly with bricks or concrete, and the bottom of the tunnel should be considered.
4. there are more pipes that are pierced by pipes, such as cast iron pipe, steel pipe, polyethylene pipe, nylon pipe and carbon pipe, which can be selected according to the needs. When single core cable is through metal pipe, the influence of eddy current should be paid attention to.
3. What should be paid attention to in the pipe arrangement? Under what circumstances?
The laying of the pipe is mainly used in the areas with more lines and concentrated routes. Relatively speaking, it is more convenient to lay out the pipe and save materials.
Question 1 is the outdoor pipe laying cable, one line of pipe, one cable, or multiple cables can be laid in one row of pipes?
A: only one cable should be worn for each pipe. Except for important places such as power plant and substation, for all circuits of one motor or all circuits of low voltage motor of the same equipment, no more than 3 power cables or multiple control cables can be connected in each pipe.
Question 2. The laying depth of row 2 pipe is not enough, what should be done?
(problem added: how to embed cable bank pipe on the ground less than 1m thick? Below is basement, basement roof is only 70, 80 cm thick, well depth is 1.3m?)
A: if the buried depth is not less than 0.5m in the area without vehicles passing (the cable specification requires 0.5m and the civil code requirement is 0.7m, the cable specification shall prevail here). If there are more vehicles to pass, the protective plate can be added to the discharge pipe. Or use thick wall steel pipe to lay or use cable trench. If the roof of basement is only 70-80 cm of soil covering, the well depth of 1.3m is to reduce the slab of the roof, but this is not significant, because the drainage problem of cable well is difficult to solve, and few people pay attention to it.
Question 3. Strong current discharge pipe and weak current pipe, laying problem?
(problem added: there is an external line in the plant, with more than ten low-voltage and strong current cables, and also weak current (TV, telephone, network) cables. The strong current cables are more than 8, and can not be buried directly. I used the laying of the pipes. But now there is a problem, that is, weak current is also laid through pipes. Can strong and weak current pipes be arranged all the time
A: try not to be in line, when doing small municipal work, try to set strong and weak electric pipes on both sides of the road. If there are occasional intersections, it is recommended to implement the requirements of the specification spacing. Please refer to the atlas, such as laying 05×101-2 underground communication cable.
Question 4 outdoor cable concrete pipe laying?
(problem supplement: when drawing the general drawing, all outdoor cables shall be laid by concrete pipe arrangement according to Party A’s requirements. After consulting the atlas (94d164), the following problems were found:
1. due to the influence of other pipelines on site, the manhole shaft of cable drain pipe can not be in accordance with the size shown in the atlas except for straight shaft,
I wonder what reasonable solutions are available?
2. the drainage problem in the manhole. According to the requirements of the people’s regulations, the sump pit is required in the manhole, but it is not known what method is adopted to centralized drainage.
3. the spacing between man hole and well is 150m according to the specification, and the atlas is 50m. I don’t know which one is the rule, or there are other provisions.
4. whether there are other atlas to refer to. Besides standard wells, can you design the shape and size of the well itself.
5. what should be paid attention to in the design and construction of this laying method.)
1. Non standard wells can be designed as required;
2. For drainage in the well hole, if there is any condition for setting drainage pump, drainage pump shall be set. If there is no way to set drainage pump, overflow hole shall be set at the bottom of sump, and it is not sealed with concrete, so that water can be penetrated naturally, but it depends on local groundwater level;
3. The spacing of manhole wells is usually considered according to 50-70;
4. In my opinion, it is unnecessary for small municipal distribution to do well according to the atlas requirements, and it is not standard;
4. What should be paid attention to in cable trench laying? Under what circumstances?
Pay attention to cable trench laying, cables of different voltage levels shall be set up according to different supports, and drainage measures shall be paid attention to in cable trench itself. And consider measures to prevent the entry of mice and other small animals.
Question 1 how many cables need to be laid in cable trenches?
A: according to “measures 2009 6.10 section 8 below recommended to adopt direct burial, 8-12 recommended to use the drainage pipe, 12-18 recommended cable trench, 18 more recommended cable tunnel.” These are all suggestive, and can be combined with actual engineering reference, not so fixed. As for cable trench and cable tunnel, it is not the difference between number of roots, but also the difference between maintenance and importance.
It mainly depends on the factors such as engineering conditions, environmental characteristics and cable type, and the selection of requirements for reliable operation, easy maintenance and reasonable technology and economy. It is uncertain whether there are mandatory index requirements.
Question 2 how to calculate the cable capacity of cable trench laying?
Netizen 1: (considering the cable tray laying, considering that the bridge is in the air, and the cable trench has cover plate, the capacity reduction coefficient is 0.96.)
Netizen 2: (for the coefficient of bearing capacity, refer to GB t16895.15-2002 “bearing capacity of 523 wiring system of Part 5 of electrical installations of buildings”, considering that the coefficient is appropriate to determine the ladder according to the ladder coefficient
Is there a depth requirement for the laying of high voltage cable with length question 3?
A: no requirement, the depth of cable trench is determined by the number of cables and the number of cable types. There are control cables, low-voltage power cables and high voltage power cables, which are generally divided into three layers. Generally, the spacing between each layer is 250-300, so the height can be determined,
Question 4 can be laid along the cable trench through bus duct?
(problem added: first, for high-level hospitals, it is necessary to save money. Oil immersed transformers shall be used for outdoor installation. 15 meters from the building (6m from the road in the middle) and the low voltage distribution room is located underground of the hospital. In order to save investment, I want to use bus duct (3000A load) to lay along the cable trench to the underground distribution room of the house.
A: dense buses meeting the corresponding IP level requirements can be adopted, for example, Siemens’ buses can be submerged underwater. However, the cost of using dense busbars will be higher, preferably dry-type transformers and bus bars should be considered comprehensively. The personal recommendation is to use dry transformers and put them indoors. Maintenance work will be reduced and failure rate will be reduced.
Question 5 how many cables can be laid in the cable tray without support?
A: Generally speaking, it is necessary to support it. If not supported, cable maintenance in the cable trench will be more troublesome. If the project is small and the number of cables is not large, it will not be harmful to set it, but the cooling conditions will be worse and if there is water in the trench, it will also affect the cable.
Q6 can high and low voltage cables be placed in the same cable tray?
(added questions: outdoor cable trench, width 1200mm, support on both sides, 10kV High Voltage Cable on one side, 1kV LV cable and control cable on the other side, please note whether it meets the specification? What should we pay attention to
Answer: cable trenches can be laid together. See setting requirements for specific requirements
Question 7 what is the distance between the cable trench and the road?
A: This is mainly to consider the force of cable trench cover plate. If there is no problem, there is no problem. Usually, it is set on sidewalks or where motor vehicles do not pass.
Should armour cable be used when Q8 is laid in cable trench?
(problem supplement: technical measures say: when laying cables in cable trenches or cable tunnels, cables with anti ant and rodent protection functions shall be considered. But it seems that there is no clear explanation on the standard! Can’t armour be used?
A: embedded cables do not need mandatory armouring and cable trenches will not exist. According to different environmental requirements (if mouse activity in this area is rampant, armor is recommended), there is no mandatory requirement.
Question 9 when placed in layers on the same side of the support, what is the minimum distance between the strong current cable and the weak current cable in the cable tray?
A: separate the weak current cable from the metal plate and ground the metal plate at the same time! It is best to pad the upper bracket with a plate (or metal slot box), then ground the plate and place the weak current cable on the plate (in the slot box).
The voltage levels shall be arranged in “descending order” of power cables from high to low, control and signal cables from strong to weak current and signal cables from communication cables to power sources.