AAAC ACSR

Cable threading, tips you don’t know!

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In the wiring of weak current projects, we usually bury the wire tube in the wall first. Such a hidden design will not affect the beautiful effect of decoration. However, after the AAAC Cables tube is buried, threading from the inside is a troublesome thing. Sometimes we can’t wear a wire after tossing for a long time. What should we do at this time?

In fact, the reason is that we don’t use the right way to thread wires. Let’s introduce a new way to thread wires. It’s so fast and professional for wires to go through pipes. Teachers and Fu all install it like this. It’s too smart!
01
What’s good for threading wires
The traditional wire threading method is generally to put a small steel wire in the wire pipe, then bend the steel wire to buckle the outer edge of the pipe, tie the wire to one end of the steel wire, pull the steel ACSR Cables on the other side, and then slowly pull the wire out of the pipe, but this construction method tests patience. Moreover, it will greatly increase the decoration time, and the operation is also more troublesome. If you meet a corner, sometimes it takes half a day to get the line out. So now more and more people are not using this method.
However, with the development of technology, some tools in decoration are constantly updated, so now smart masters no longer use steel wire rope, but use this, which can thread quickly without jamming. Now the outer skin of professional threading device is made of steel wire wrapped rubber, which has good hardness and smoothness. It is much stronger than the previous steel wire rope, and it is not easy to jam at the elbow. In particular, a pulley is installed at the thread feeding head, which is very popular with teachers.
This threading device is also very simple in operation. It can be used for the first time. Use the traction head of the wire to pass through the wire head, and then fix it with a professional tensioner. This kind of tightener not only has good fixing effect, but also is convenient for construction, which saves the threading time of the master. After the thread head passes through the tightener, wrap it into an 8-shaped shape, and then push it up with the fastening spring. It is not too convenient. This is why more and more masters like to use the tightener instead of the steel wire rope.

02
Let’s introduce several standard threading methods
1. The first is that some wires will be long, or when it is necessary to turn and wind in the actual environment, talc powder can be added to the pipe to facilitate the extraction of wires. Remove a little of the insulation material in the front section of the wire, and then slowly fix the wire core in the coil.
2. The more important point is: wires with different voltages and different circuits must not be threaded in the same conduit. In addition, if the circuits of multiple lamps will not interfere with each other, remember not to thread too much.
3. After the wires are strung, remember to cut off the wires. If you want to connect the blood to the switches, sockets and junction boxes, we remember to reserve more than 15 cm. In addition, more than half of the perimeter of the distribution box should be left in the distribution box. Oh, the wires outside the door should be left about one and a half meters.
03
Wire threading cannot be carried out casually, and the following points shall be ensured
1. Be sure to select wires with good quality and large wire diameter. The threading pipe shall be flame-retardant PVC pipe. When purchasing, you can pinch it with your fingers. If it can’t be broken, it means that the quality is very good. If the economy permits, special galvanized pipe can also be selected.
2. In the same conduit, the number of wires passing through shall not be too much, and it shall be easy to pull. The popular standard is that the total cross-sectional area of the wires in the pipe shall not be greater than% of the total cross-sectional area of the inner diameter of the pipe, and shall not exceed


3. The inner wire shall be free of joints and kinks. The pipe sleeve shall be used when the pipeline is butted, the bend shall be connected with elbow or tee, and then glued with glue. The presser foot cap shall be used when connecting to the wire box, and the lock interface must be used between the wire pipe and the wire box.
4. High power electrical appliances such as floor heating and air conditioning should be wired separately, and electrical appliances such as refrigerators that are not suitable for frequent power cuts should also be wired separately. These electrical appliances should have separate switches at the main switch (air switch). If you go far away, you can turn off other power supplies, leaving only the refrigerator power on.
5. After the wire passes through the pipe, it is put into the slot and fixed with cement or quick drying powder, that is, several points are selected on a slot for sealing and fixing. When installing the cassette, the wall hole where the cassette is placed should be larger. Cement can be embedded in the gap between the cassette and the wall hole to fix the cassette firmly to prevent loosening in the future.
6. After the wiring is completed, the decoration company must leave a detailed “pipeline diagram”, number the wall, draw the direction and specific position of the wire with a pen, indicate the size from the upper floor to the lower floor and adjacent wall, especially the joint position of the pipeline. With such a detailed, it will be much more convenient to overhaul the ABC Cables in the future.
From the above points, we can know that it is necessary for wires to go through pipes in the process of decorating circuits. Now experienced masters will choose new types of threading appliances for wire threading. It is fast and professional to wear wires with it. Friends who like it might as well try it.

Matters needing attention during wire and cable stranding

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In order to improve the flexibility and integrity of wires and cables, two or more single wires are intertwined in the specified direction. This process is called stranding. The whole stranding process is divided into conductor stranding, cable forming, braiding, steel wire armor and winding. Any problem in any process will directly affect the cable quality.
What should we pay attention to in the process of stranding? Which links are prone to problems? Do you know all this? Next, let’s introduce the matters needing attention and easy problems in the middle process of wire and AAC Cable twisting.

18 questions and answers about cable stranding process
1. What are the quality requirements for stranded conductor cores?
Answer: the stranded wire core shall be tight, round, straight, without serious bending, strand skipping, scratch and flattening, the copper wire surface shall be free of oxidation, blackening, tin coating falling off or tin particles, uniform pitch, flat and firm joints, neat wire arrangement, AAAC Cable diameter shall meet the tolerance requirements, and length shall meet the specified requirements.
2. What preparations should be made before strand production?
Answer: (1) check whether all parts of the stranding machine are normal and whether there are obstacles in the operating parts（ 2) Check whether the electromechanical equipment, electrical switch and fence insurance are normal（ 3) Check whether the butt welding machine is normal（ 4) Check whether the tools and measuring tools are complete（ 5) Select and match the die according to the requirements of the dispatch list and process card, replace the pitch lap gear, replace the twist direction, measure the wire diameter, etc.
3. What are the main reasons for the scratch of stranded wire core and jumper?
Answer: (1) the main causes of abrasion are: the guide wheel is damaged or the conductor jumps out of the guide wheel, the threading pipe is damaged, the die is damaged or too small, and the conductor is crushed or abraded when the disc is rolling. Prevention method: replace the guide wheel to prevent the conductor from jumping out of the guide wheel, replace the threading pipe, select the die and replace the reel（ 2) The main reasons for jumper are: the die is too far from the distribution board, the setting out tension is inconsistent, the die is too large, etc. Prevention method: reasonably adjust the distance between the die and the branching board, adjust the base number of setting out tension, and reasonably select the die.
4. What is untwisting? Under what circumstances is the effect significant?
Answer: untwist stranding is to keep each reel equipped with a single line in a horizontal position through a special device (untwist mechanism), so as to ensure that each single line does not produce self twisting deformation in the stranding process. Only when the diameter of the single line is large, the pitch is large and the single line is hard, the untwisting will have a good effect.


5. Which two requirements must the structure of sector core meet?
Answer: (1) the single lines on the center warp of the central layer shall also be arranged on the center line of the sector. If this requirement cannot be guaranteed, when the core is bent, these single lines will be stretched or compressed, resulting in the uplift of the single line, resulting in the change of the shape of the sector core（ 2) Slip requirement: that is, the single line around the fan-shaped outer circumference shall be able to slide on the central layer. This is because the insulated fan-shaped line is not twisted back when it is twisted into the cable core, and each single line around the outer circumference tries to slide around the central plane. Therefore, if this requirement is not met, the single line will jump up and damage the shape of the fan-shaped line.
6. For stranded wires in concentric layers, the direction of adjacent layers is specified to be opposite. Why?
Answer: (1) the stranded wire is round. If the adjacent layers are twisted in the same direction, it is easy to embed the single wire of the outer layer into the inner layer, thus damaging the complete circular structure（ 2) When the stranded wire is under tension, the rotating torque generated by each layer is opposite, which can offset each other to prevent the loose strand caused by the single wire of each layer rotating in the same direction. At the same time, it can also avoid the looping phenomenon of the stranded ACSR Cables when it is not tensioned（ 3) In steel cored aluminum strand, AC impedance can be reduced, corona phenomenon and power loss can be reduced.
7. What are the two methods of twisting insulated cores together? What kind of communication cable is currently used in domestic cities?
Answer: twisted pair and star twisted pair. At present, twisted pair communication cables are used in domestic cities.
8. What’s the reason why the inlet of the die hole of the die used in twisting the cable is in the shape of a horn?
Answer: the horn shape at the inlet of the die hole has two advantages: (1) to gradually compress the twisted cable core（ 2) It will not scratch the cable core.


9. What are the main differences between a winch and a cage winch?
Answer: the stranding part of the cage winch is connected with the paying off device, while the stranding part of the winch is not connected with the paying off device, but with the traction device and take-up device.
10. In terms of structure, what are the wrapping forms of the package for cabling?
A: there are three types: simple type, plane type, tangent or semi tangent type. The simple wrapping head is a wrapping in which the wrapping reel is at an angle with the group or the cable core axis. The flat winding head is the winding in which the tape reel is perpendicular to the wire group or cable mandrel, and the tangent (half tangent) winding head is the winding in which the tape reel is parallel to the wire group or cable mandrel.
11. The trial fraction shows the relationship between the package noise pitch H (mm) and the forward speed V (M / min) of the cable core and the number of revolutions n (R / min) of the package head rotating around the cable core.
Answer: H = V / N = 1000 (mm)
12. What is the difference between unit stranding and concentric stranding?
Answer: the stranding direction of each layer of unit stranding cable core is the same, and the multiple of stranding distance is large, which is about 1.5 times that of concentric stranding. The unit quantity in each layer of cable core does not follow the rule of N + 6. The reason is that it is necessary to completely fill the cable core to cause deformation, so that each unit no longer maintains the original circle. The unit quantity of each floor basically follows the rule of N + 4.
13. What is a cable? How many deformations are there when the insulated core is cabled?
Answer: the process of twisting multiple insulated cores into cables according to certain rules is called cable. When the insulated core is cabled, there are two kinds of deformation: one is the bending deformation caused by the core around the cylinder, and the other is the torsional deformation caused by the direction of the spiral wire.
14. What is reverse twist? Why do we use untwist to form cables with circular cores?
Answer: when stranding, the method of reverse twisting of the wire is called untwisting. For the circular core cable, the untwisted cable is mostly used to reduce the core deformation, avoid damaging the insulation due to deformation, and make the cable have good flexibility.
15. What are the main qualities and requirements of auxiliary materials in the cable forming process of power cables?
Answer: the auxiliary materials in the cable forming process of power cable include: filler rope liner, tie belt and shielding belt, which shall have heat resistance, non water absorption, consistent cable working conditions and no corrosive insulating materials. The tie belt for filling and lining shall have considerable mechanical properties and meet the process requirements.
16. General selection principle of cable forming die for sector core? What should we pay attention to in the specific operation process?
Answer: the first mold is 1.0 ~ 3.0mm larger than the outer diameter of the cable, and the second mold is 0 ~ 0.6mm smaller than the outer diameter of the cable. The third die is 0 ~ 0.2mm smaller than the outer diameter of the finished cable. Pay attention to the actual use of the die. The cable cannot swing in the die, the cable core does not feel loose when rotating by hand, and the heat generated by the friction between the die and the insulated wire core should not be hot. The surface of the pressing die of the insulated wire core shall be smooth without damage and other marks.
17. After the completion of a certain specification of control cable, it is found that the conductor is thin or even broken, and the main causes are analyzed?
A: the following reasons lead to fine drawing and fracture: (1) excessive setting out tension（ 2) Wire clamp at wire nozzle（ 3) The insulation of the wire core is wrapped, and the part is thick（ 4) The wire joint is not firm（ 5) The take-up force is too large.
18. Causes and preventive measures of fan-shaped insulated wire core turning over?
Answer: the causes of fan-shaped insulated wire core turning over are: (1) insufficient pre torsion angle（ 2) When the pay off reel is on, the core row turns over, and the core is thick（ 3) The wire core is twisted back during the split footwall, resulting in turning over. The prevention methods are: (1) adjust the distance between the pre angle spring die and the core guide wheel（ 2) Adjust the pre twist angle, arrange the line on the pay off reel once, turn the reel if necessary, and the line shall be neat and not loose.

Completion of laying of high temperature AC superconducting cable

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The transmission capacity of superconducting AAC Cable is much larger than that of conventional cable. The power transmission capacity of a 10KV three-phase coaxial high temperature AC superconducting cable is greater than that of a conventional 110kV cable, but the transmission loss is only one fourth to one fifth of that of a conventional cable, which is very suitable for power supply in high load density areas. However, due to the great difficulty of project implementation, at present, the above application scenarios are still blank in China and even in the world.
The superconducting cable laid this time passes through the busy roads, subway areas and core business districts in the central urban area of Shenzhen. The laying environment space is narrow. There are special complex working conditions such as 24.2m vertical drop, more than 10 turns less than 90 degrees, short-span S-shaped corners and staggered height of transmission pipelines. There is almost no precedent experience to follow. It is a typical “small corridor” of complex transmission in large cities, Even laying conventional cables is challenging.


In the face of such special and complex working conditions, in order to ensure the smooth completion of superconducting cable laying, the superconducting cable project team of Shenzhen Power Supply Bureau has conducted dozens of field surveys and discussions in the past three months, and formulated a special research scheme of “remote simulation laying + on-site pre laying”. The project team built a simulation site at the location of the manufacturer, restored various special and complex working conditions, carried out many simulation laying drills, obtained a large amount of valuable data, accumulated on-site experience and laid a solid foundation for on-site laying. In the project site, analog cables of the same size and weight are pre laid twice, which provides the most direct reference for formal laying.
During the laying process, in addition to the conveyor and winch required for conventional AAAC Cable laying, the project team has developed special auxiliary guidance, turning radius limit protection, nozzle center positioning, well shaped conveying wheel set and other laying tools and instruments to ensure the safe and reliable laying of superconducting cable body.
Next, the project will enter the installation, test and commissioning stage of superconducting cable accessories, supporting low-temperature refrigeration system, measurement and control protection system, etc. When the project is put into operation, it is expected to “package” solve many problems and challenges such as the difficulty of power grid construction land in large cities, the continuous growth of power grid load demand and the saturation of urban transmission and distribution corridors, so as to provide a new scheme for solving the problem of regional power supply with high load density in mega cities around the world
Other media reports:
The first 10kV three-phase coaxial high temperature AC superconducting cable in China has been laid
Xinhua news agency, Shenzhen, July 30 (reporter Wang Feng) – the reporter learned from the Shenzhen Power Supply Bureau of China Southern Power Grid on the 30th that the first 10kV three-phase coaxial high-temperature AC superconducting cable in China was laid in Shenzhen on the 28th, laying the foundation for the first demonstration project of this type of superconducting cable to be put into operation within the year. It is expected to “package” solve the difficulty of power grid construction land and the continuous growth of power grid load demand in big cities There are many problems and challenges such as the saturation of urban transmission and distribution corridors.
It is reported that the project is a major science and technology project of China Southern Power Grid Corporation. It is developed by Shenzhen Power Supply Bureau of China Southern Power Grid and connects 220 kV Binhe substation and 110 kV Xinghe substation in Futian central area of Shenzhen. The cable length is 400 meters. It will supply power to important loads such as Shenzhen landmark Ping’an building.
High temperature superconducting power transmission refers to the use of the superconducting properties of superconducting materials to make the power transmission medium close to zero resistance and the power transmission loss close to zero in the liquid nitrogen environment close to minus 200 ℃ relative to absolute zero, so as to realize high-capacity power transmission at low voltage level. A 10KV three-phase coaxial high temperature AC superconducting cable has the power transmission capacity equivalent to a conventional 110kV cable.
It is understood that at present, most domestic superconducting ACSR Cable demonstration projects are experimental in nature, and the importance level of line load is low. The demonstration project plans to apply superconducting cable to the high load density power supply area in the city center to supply power to important loads, which will be a big test for the application of superconducting cable.
Next, the project will enter the installation, test and commissioning stage of superconducting cable accessories, supporting low-temperature refrigeration system, measurement and control protection system, etc. When the project is put into operation, it will provide a new scheme and model for solving the power supply problem in high load density areas of mega cities.

How to choose wires for home decoration

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Recently, the home decoration needs to buy Wires for construction. At this time, I don’t know which kind to buy, and I don’t know how to choose wires? So, today in this article, we will use three easy to understand steps to explain the relevant knowledge of wires in decoration, and let them know which is good, including how to choose.

Step 1: first understand what types of wires are used in home decoration
There are many kinds of wires, and the AAAC Cables that can be used for home decoration are fixed. The specific classification is as follows:
Bv wire (hard wire)
BVR wire (Multi Strand flexible wire)
RVs thread (plush thread)
BLVVB wire (aluminum sheathed wire)
BVVB wire (copper sheathed wire)
BLV wire (single strand aluminum core wire)
RVV line (copper core cable) household weak current line: closed circuit line, network line, telephone line, audio line, etc.
In other words, among the wires available for home decoration, with the continuous improvement of wire use requirements and user requirements, BV wires (hard wires) are currently used for strong wires, and BVVB wires (copper sheathed wires) will still be used in some areas. For weak wires, RVV wire (copper core cable) is used.

Step 2: understand why bv wire is suitable for home decoration ACSR Cables
1. What is bv line
Bv wire refers to copper core PVC insulated wire, where B represents category and V represents insulated PVC, with bv1.5m ²、 BV2.5m ²、 BV4.0m ²、 BV6m ² Wait, wire diameter classification. Bv line can be divided into BV and ZR-BV, among which ZR-BV is flame retardant bv line. In home decoration, most of them can meet the use requirements by using bv line. Only a few owners and decoration companies will use ZR-BV line to use home decoration wires. No matter which one of BV and ZR-BV is used, it can be applied to power devices and daily appliances with AC voltage of 450 / 750V and below, that is, it can ensure the daily power demand and safe use at home.
2. Why bv line is suitable for home decoration
Bv line can stand out among many household wires. Of course, it must have sufficient advantages and persuasion. Otherwise, it will not become the dominant type of wires for home decoration. Specific advantages are as follows:
Convenient construction: bv wire is a single strand wire, which is very convenient whether threading or wiring during construction. This provides convenience in construction. At the same time, because the BV line is a single strand line and a single cycle line, it is also very convenient to take it. It can save the time of construction workers during construction. Therefore, the master is willing to recommend users to buy this kind of wire. Under the same labor cost, using the bv line can save at least one man hour. From the side, it is to make the construction earn more money.
High safety: for BV wire, because it is a copper core PVC insulated wire, its internal is a single strand copper core, and the external is insulated with PVC, which is the best in use safety. Meanwhile, BV wire is made of 99% pure oxygen free copper, because the oxygen free copper core has low resistivity, excellent conductivity, large current carrying capacity, good ductility, oxidation resistance, corrosion resistance, strong stability and high safety.
Affordable price: the price of wires is the main factor affecting consumers’ purchase. Under the condition of ensuring safety, the price of BV line is only a little higher than that of traditional line, and the cost of single lap is not very high, which is within the range acceptable to consumers. Therefore, as consumers, with high safety and affordable price, they will naturally choose to use bv line.
Strong tensile resistance: bv wire needs to be threaded for construction when power is used for home decoration. At this time, the construction of threading and pulling wire will occur. Whether through the steel ratio or the wire itself, it will produce a certain tensile force on the wire. At this time, BV wire will not have any impact on the constructors when they pull wire normally, and will not damage the internal single strand copper core, If PVC insulation material is used externally, consumers will naturally feel relieved to use it, which also shows its high safety from the side.
Long service life: for BV wire, the inner part of the base is a single strand copper core and the outer part is PVC insulating material. Through such protection, the inner single strand copper core can have stronger corrosion resistance and oxidation resistance, so as to prolong the service life of the ABC Cable, which also meets the service life requirements of home decoration wires. Generally speaking, it is no problem to use it for 10 years.
Through the above basic explanation and advantages of BV line, we can clearly know why bv line is suitable for home decoration, and it is also the best strong current line for home decoration at present.

Step 3: how to select wires?
Now that we know that the wires used for home decoration are bv wires, the next step is to know how to choose. I believe this is also a matter of great concern to most consumers. The specific selection steps are as follows:
The first step in selecting high-quality wires is to look at the wire diameter: bv wires can be divided into bv1.5m due to different wire diameters ²、 BV2.5m ²、 BV4.0m ²、 BV6m ² And so on. For home decoration, it is often bv2.5m ²、 BV4.0m ² Mainly used in lighting and socket circuits. For the earliest bv1.5m ² Generally speaking, bv2.5m is rarely used in lighting, and bv2.5m is directly used ² To be used as a lighting circuit. BV6m ² Wires are often used for independent circuits, as well as high-power electrical appliances for home decoration, such as central air conditioning and fast heating hot water products.
The second step of selecting high-quality wires is to look at the color: I believe that after you understand the wire diameter of BV wire, you will find that there are many colors when you see bv wire in the market, and the merchant will tell you which color to buy for use. And this is also the BV, which needs to pay attention to details, because different colors represent different meanings. Red is used as the fire line L; Blue, yellow and green are used as zero line n; The yellow green two-color wire is used for the ground wire PE. Different colors should be used in different positions, and the construction should be carried out according to the standard color wire. In this way, whenever the home wire needs to be maintained and reinstalled with new electrical appliances, it is very convenient to recognize the fire, zero and ground wire of the wire, so naturally there will be no wiring errors and major potential safety hazards.
The third step of selecting high-quality wires is to look at the brand: the brand is also reflected in the wire industry. As a large domestic brand, the quality of wires produced can be guaranteed. But sometimes, because of the reasons why sales are not suck, the local production lines can be recognized by consumers in many city. Therefore, when purchasing wires, we must decide the local conditions according to the local conditions. If the local people recognize their local brands, then they can choose their local brands, so we need not worry about the quality at this time. Because the local brand wire is recognized by consumers.
The fourth step of selecting high-quality wires is to look at the trademark: the trademark mentioned here does not mean the trademark of the wire brand, but the specific information on the wire packaging and 3C certification, because the formal wire brand must have specific information about the goods on its outer packaging during production. In addition, there must be strong safety standards implemented by the industry. With this information, Wires can be used safely.
The fifth step of selecting high-quality wire is to look at the copper core: for BV wire, its interior is a single strand copper core, and the copper core is made of 99% pure oxygen free copper, so pay attention to the brightness of the copper core when purchasing. Generally speaking, the higher the copper quality, the better, and the brightness is uniform and shiny. When buying, you can simply do an experiment. If you bend the wire for many times, it means that the bending resistance is good, which means that the copper quality is good. If you break after bending a few times, it means that you can’t buy if the copper quality is not up to the standard.
The sixth step of selecting high-quality wires is to look at the appearance: for BV wires, the external PVC insulation material is also very key, which is an important factor to ensure the safety of wires. Therefore, pay attention to the appearance and check the color and texture of PVC insulation materials. Generally speaking, whether the high-quality PVC insulation material has bright color and fine texture; The inferior PVC insulation material uses recycled plastic, so the appearance color is dim and the texture is loose, so such wires can not be selected.
The seventh step of selecting high-quality wire is to look at the meter number: for BV wire, it is usually written on the commodity packaging that it is 100 meters, but in fact it is only about 95 meters. Such a meter number shows that it is full meters, which is also the rule of the industry. For some wires, the number of meters is only about 90 meters, less than 95 meters, so we need to pay attention. Such wires belong to non-national standards, and their quality can not be used safely.

summary
Recently, for home decoration, buying bv hard wire is the best choice for wire use. It is a wire that can ensure quality and safety. At the same time, as long as we follow the above seven steps of selecting wires, we can select high-quality wires and be assured and worry-free.

18 key problems in cable stranding process

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In order to improve the flexibility and integrity of wires and cables, two or more single wires are intertwined in the specified direction. This process is called stranding. The whole stranding process is divided into conductor stranding, cable forming, braiding, steel wire armor and winding. Any problem in any process will directly affect the cable quality.
What should we pay attention to in the process of stranding? Which links are prone to problems? Do you know all this? Next, let’s introduce the matters needing attention and easy problems in the middle process of wire and cable twisting.
18 questions and answers about AAAC Cable stranding process


1. What are the quality requirements for stranded conductor cores?
Answer: the stranded wire core shall be tight, round, straight, without serious bending, strand skipping, scratch and flattening, the copper wire surface shall be free of oxidation, blackening, tin coating falling off or tin particles, uniform pitch, flat and firm joints, neat wire arrangement, wire diameter shall meet the tolerance requirements, and length shall meet the specified requirements.
2. What preparations should be made before strand production?
Answer: (1) check whether all parts of the stranding machine are normal and whether there are obstacles in the operating parts（ 2) Check whether the electromechanical equipment, electrical switch and fence insurance are normal（ 3) Check whether the butt welding machine is normal（ 4) Check whether the tools and measuring tools are complete（ 5) Select and match the die according to the requirements of the dispatch list and process card, replace the pitch lap gear, replace the twist direction, measure the wire diameter, etc.
3. What are the main reasons for the scratch of stranded wire core and jumper?
Answer: (1) the main causes of abrasion are: the guide wheel is damaged or the conductor jumps out of the guide wheel, the threading pipe is damaged, the die is damaged or too small, and the conductor is crushed or abraded when the disc is rolling. Prevention method: replace the guide wheel to prevent the conductor from jumping out of the guide wheel, replace the threading pipe, select the die and replace the reel（ 2) The main reasons for jumper are: the die is too far from the distribution board, the setting out tension is inconsistent, the die is too large, etc. Prevention method: reasonably adjust the distance between the die and the branching board, adjust the base number of setting out tension, and reasonably select the die.
4. What is untwisting? Under what circumstances is the effect significant?
Answer: untwist stranding is to keep each reel equipped with a single line in a horizontal position through a special device (untwist mechanism), so as to ensure that each single line does not produce self twisting deformation in the stranding process. Only when the diameter of the single line is large, the pitch is large and the single line is hard, the untwisting will have a good effect.


5. Which two requirements must the structure of sector core meet?
Answer: (1) the single lines on the center warp of the central layer shall also be arranged on the center line of the sector. If this requirement cannot be guaranteed, when the core is bent, these single lines will be stretched or compressed, resulting in the uplift of the single line, resulting in the change of the shape of the sector core（ 2) Slip requirement: that is, the single line around the fan-shaped outer circumference shall be able to slide on the central layer. This is because the insulated fan-shaped line is not twisted back when it is twisted into the ABC Cable core, and each single line around the outer circumference tries to slide around the central plane. Therefore, if this requirement is not met, the single line will jump up and damage the shape of the fan-shaped line.
6. For stranded wires in concentric layers, the direction of adjacent layers is specified to be opposite. Why?
Answer: (1) the stranded wire is round. If the adjacent layers are twisted in the same direction, it is easy to embed the single wire of the outer layer into the inner layer, thus damaging the complete circular structure（ 2) When the stranded wire is under tension, the rotating torque generated by each layer is opposite, which can offset each other to prevent the loose strand caused by the single wire of each layer rotating in the same direction. At the same time, it can also avoid the looping phenomenon of the stranded wire when it is not tensioned（ 3) In steel cored aluminum strand, AC impedance can be reduced, corona phenomenon and power loss can be reduced.
7. What are the two methods of twisting insulated cores together? What kind of communication cable is currently used in domestic cities?


Answer: twisted pair and star twisted pair. At present, twisted pair communication cables are used in domestic cities.
8. What’s the reason why the inlet of the die hole of the die used in twisting the ACSR Cable is in the shape of a horn?
Answer: the horn shape at the inlet of the die hole has two advantages: (1) to gradually compress the twisted cable core（ 2) It will not scratch the cable core.
9. What are the main differences between a winch and a cage winch?
Answer: the stranding part of the cage winch is connected with the paying off device, while the stranding part of the winch is not connected with the paying off device, but with the traction device and take-up device.
10. In terms of structure, what are the wrapping forms of the package for cabling?
A: there are three types: simple type, plane type, tangent or semi tangent type. The simple wrapping head is a wrapping in which the wrapping reel is at an angle with the group or the cable core axis. The flat winding head is the winding in which the tape reel is perpendicular to the wire group or cable mandrel, and the tangent (half tangent) winding head is the winding in which the tape reel is parallel to the wire group or cable mandrel.
11. The trial fraction shows the relationship between the package noise pitch H (mm) and the forward speed V (M / min) of the cable core and the number of revolutions n (R / min) of the package head rotating around the cable core.
Answer: H = V / N = 1000 (mm)
12. What is the difference between unit stranding and concentric stranding?
Answer: the stranding direction of each layer of unit stranding cable core is the same, and the multiple of stranding distance is large, which is about 1.5 times that of concentric stranding. The unit quantity in each layer of cable core does not follow the rule of N + 6. The reason is that it is necessary to completely fill the cable core to cause deformation, so that each unit no longer maintains the original circle. The unit quantity of each floor basically follows the rule of N + 4.
13. What is a cable? How many deformations are there when the insulated core is cabled?
Answer: the process of twisting multiple insulated cores into cables according to certain rules is called cable. When the insulated core is cabled, there are two kinds of deformation: one is the bending deformation caused by the core around the cylinder, and the other is the torsional deformation caused by the direction of the spiral wire.
14. What is reverse twist? Why do we use untwist to form cables with circular cores?
Answer: when stranding, the method of reverse twisting of the wire is called untwisting. For the circular core cable, the untwisted cable is mostly used to reduce the core deformation, avoid damaging the insulation due to deformation, and make the cable have good flexibility.
15. What are the main qualities and requirements of auxiliary materials in the cable forming process of power cables?
Answer: the auxiliary materials in the cable forming process of power cable include: filler rope liner, tie belt and shielding belt, which shall have heat resistance, non water absorption, consistent cable working conditions and no corrosive insulating materials. The tie belt for filling and lining shall have considerable mechanical properties and meet the process requirements.
16. General selection principle of cable forming die for sector core? What should we pay attention to in the specific operation process?
Answer: the first mold is 1.0 ~ 3.0mm larger than the outer diameter of the cable, and the second mold is 0 ~ 0.6mm smaller than the outer diameter of the cable. The third die is 0 ~ 0.2mm smaller than the outer diameter of the finished cable. Pay attention to the actual use of the die. The cable cannot swing in the die, the cable core does not feel loose when rotating by hand, and the heat generated by the friction between the die and the insulated wire core should not be hot. The surface of the pressing die of the insulated wire core shall be smooth without damage and other marks.
17. After the completion of a certain specification of control cable, it is found that the conductor is thin or even broken, and the main causes are analyzed?
A: the following reasons lead to fine drawing and fracture: (1) excessive setting out tension（ 2) Wire clamp at wire nozzle（ 3) The insulation of the wire core is wrapped, and the part is thick（ 4) The wire joint is not firm（ 5) The take-up force is too large.
18. Causes and preventive measures of fan-shaped insulated wire core turning over?
Answer: the causes of fan-shaped insulated wire core turning over are: (1) insufficient pre torsion angle（ 2) When the pay off reel is on, the core row turns over, and the core is thick（ 3) The wire core is twisted back during the split footwall, resulting in turning over. The prevention methods are: (1) adjust the distance between the pre angle spring die and the core guide wheel（ 2) Adjust the pre twist angle, arrange the line on the pay off reel once, turn the reel if necessary, and the line shall be neat and not loose.

Why are mineral insulated cables so hot?

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In recent years, the city has developed rapidly
Subway, station, hospital, school, high-rise residence
Expansion of public facilities construction scale
The number of high-rise buildings surged
The demand for urban electricity is rising
Such a densely populated key area
In case of fire, the consequences are serious
In recent years, the fire spread trend in such places shows a similar pattern

According to the analysis of construction safety and fire protection experts
At present, there are still many cables selected for public facilities
No fire resistance
It is difficult to play its due role in fire
The law expressly stipulates that China’s civil construction law stipulates that in the code for fire protection design of construction projects, the fire protection system needs to use mineral insulated cables in order to pass the fire protection acceptance.
Under fire conditions, mineral insulated AAAC Cable can not only ensure the fire power supply within the fire duration (more than 180 minutes), but also will not delay combustion, produce smoke and secondary disasters, so as to win valuable time for fire rescue.
It can be said that mineral insulated cable is a special cable that must be used for fire protection in national important facility construction, large public areas, high-rise buildings and other places. Its fire resistance, durability, safety, reliability and economy can not be replaced by traditional power cable.
1、 Mineral insulated cable structure
Chengtiantai mineral insulated cable is a kind of cable that uses copper sheath to wrap copper conductor core wire and magnesium oxide powder as inorganic insulating material to isolate conductor and sheath (outer sheath is optional), forming a close whole with metal core and sheath.
Magnesium oxide is also a non combustible material, and will not produce toxic smoke or other harmful substances when encountering high temperature. Therefore, the cable with magnesium oxide as the insulator of copper core and copper sheath has good performance and many advantages.
2、 Performance and advantages of mineral insulated ACSR Cable
Chengtiantai mineral insulated cable mainly includes bbtrz (flexible mineral insulated fireproof cable) and yttw (flexible inorganic mineral insulated cable) series. It has the characteristics of good fire resistance, high temperature resistance, large current carrying capacity, waterproof, corrosion resistance, mechanical damage resistance, radiation resistance, electromagnetic compatibility and elegant appearance. At the same time, the cable will not emit any smoke under fire conditions Halogen and toxic and harmful gases.


1. Fire performance
Because mineral cables are all composed of inorganic substances, they will not cause fire, can not burn or support combustion, and will not produce toxic gases. Even if there is external flame combustion, the cable can still work normally. Mineral insulated cable is insulated with magnesium oxide, and the melting point of magnesium oxide is as high as 2800 ℃, which is difficult to burn easily. Therefore, the fire resistance of mineral insulated cable is excellent.
The test shows that the mineral insulated cable can run normally after burning in the flame with the temperature up to 800 ℃ – 900 ℃ for 2h; After burning under 1000 ℃ flame for 30 min, the cable is still intact and continues to operate normally.
2. High temperature resistant operation, large current carrying capacity
The normal service temperature of mineral insulated ACAR Cable can reach 250 ℃. Under special circumstances, the cable can maintain operation for a short time at a temperature close to the melting point of copper sheath. It is very suitable for laying in high temperature places, such as metallurgy, boiler, glass furnace, blast furnace and so on.
Its cut-off flow is much higher than that of other cables. Because magnesia powder has a better conductor coefficient than plastic, the cut-off flow is greater at the same working temperature. For lines above 16mm, one section can be reduced, and two sections can be reduced where people are not allowed to touch.
3. Waterproof, explosion-proof, high mechanical strength
The insulating layer of mineral insulated cable is processed by high-density compaction process, and then protected by seamless copper sheath. In the product standard, it must meet the three requirements of fire resistance, spray resistance and mechanical impact, and can withstand severe impact and mechanical damage. Therefore, it can not only prevent the infringement of water, moisture, oil and some chemical substances, but also apply to the connection of various explosion-proof equipment and equipment in places with explosion risk.
4. Overload protection
When the line is overloaded, the plastic cable will cause insulation heating or breakdown due to overcurrent or overvoltage. For mineral insulated cables, as long as the heating cannot reach the melting point temperature of copper, the cable will not be damaged. Even if the breakdown occurs instantaneously, the magnesium oxide at the breakdown point will not form carbide at high temperature. After the overload is cleared, the cable performance will not change and can still continue to be used normally.


5. The service life is longer and more safe and reliable
Since the structure of mineral insulated cable is composed of copper core and insulating sheath, which is a closed whole, it is difficult for the material to be aged due to the action of oxygen in the external air, which makes the overall service life of the cable longer (2-3 times the service life of ordinary cables). In addition, the characteristics of the copper sheath make the grounding of the cable better, Therefore, lightning protection and grounding measures are effectively realized, so as to ensure the safe and reliable operation of electrical lines.
Due to many excellent characteristics of mineral insulated cables, they have been successively adopted by many domestic electrical design codes or standards in recent years, and also used in many engineering projects in different industries. It can be expected that the use of mineral insulated cables in China will increase significantly in the next decade.

Mineral insulated cables in fire power distribution

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Mineral insulated ACSR Cable, the full English name is mineral insulated cable, and the abbreviation is (MI) cable.
Due to its complex process, high production cost and much higher market price than conventional YJV and yjy cables, it was rarely used in China at the initial stage and was only used in important places with high requirements for safety conditions. Later, it was clearly required to be used under certain conditions due to the implementation of code for fire protection design of buildings gb50016-2014, which was widely popularized.
But for most engineers who do design, they often know to use it, but their understanding of it is not as good as YJV cable.
(1) Structural form
It is a kind of cable that uses copper sheath to wrap copper conductor core wire, and uses magnesium oxide powder as inorganic insulating material to isolate conductor and sheath (that is, magnesium oxide insulating layer is between core conductor and copper sheath). The outermost layer can select appropriate outer sheath as required.
See the following figure:

Mineral insulated (MI) cable
There is also a similar cable, which uses metal sheath instead of copper sheath to wrap conductor core wire and magnesium oxide insulation layer, which is called [mineral insulated metal sheathed cable].
(2) Performance and characteristics
1. Fire resistance
From the above structural form, mineral insulated cable does not contain organic materials, so it has the characteristics of non combustion, smokeless, non-toxic and fire resistance.
The melting point of copper is 1083 ℃, and the melting point of mineral insulating layer is above 1000 ℃, while the maximum temperature at the fire site of general civil buildings is below 1000 ℃. In this way, the copper sheath of the secondary layer can withstand the high temperature at the fire site.
The common fire-resistant cable, also known as organic insulated fire-resistant ACAR Cable, generally has a fire-resistant temperature of 750 ~ 800 ℃ for 90min. Therefore, the fire resistance of mineral insulated cable is quite excellent, and it is safe to use it in the fire area below the melting point of copper.
2. High temperature resistant operation
We know that the current carrying capacity and working temperature of the core are actually taken from the withstand temperature of the cable insulation layer. The higher the withstand temperature of the insulation layer, the greater the current carrying capacity.
Mineral insulated cable can withstand continuous working temperature up to 250 ℃ according to different application places. Under special circumstances, the AAAC Cable can maintain operation for a short time at a temperature close to the melting point of the copper sheath. It is very suitable for laying in high temperature places, such as metallurgy, boiler, glass furnace, blast furnace and so on.


3. Long life
The inorganic materials used in the insulating layer and sheath layer of mineral insulated cable can make it more stable and longer service life.
4. Waterproof, explosion-proof and high mechanical strength
The insulating layer of mineral insulated cable is processed by high-density compaction process, and then protected by seamless copper sheath. In the product standard, it must meet the three requirements of fire resistance, spray resistance and mechanical impact, and can withstand severe impact and mechanical damage.
(3) Classification and model
According to the cable structure, it can be divided into [rigid] and [flexible]. As the name suggests, rigid mineral insulated cables are very difficult to bend during construction and installation, while flexible cables are relatively easy to lay, and their structural profile
Rigid mineral insulated cable is marked as [BTT] type, and flexible mineral insulated cable is marked as [RTT] type.
National standard GB / T 13033-2007 rigid cable models: light load 500V bttq, bttvq, bttyq, heavy load 750V bttz, bttvz, bttyz. 500V and 750V here refer to the voltage between the core conductor and the sheath and between each conductor does not exceed 500V and 750V.
The models of flexible cables in the national standard GB / T 34926-2017 are rttz, rttyz and rttvz, and the voltage levels are 0.6/1kv or 450 / 750V.
The models of other flexible cables are named by each manufacturer. There are more than ten common types, such as bttrz, bbtrz, yttw, ng-a (btly), etc.
From the above, the national standard for rigid cables was promulgated and implemented very early, which has strong constraints on the products of various manufacturers and fixed product models; The flexible cable market was chaotic before the introduction of the national standard.


However, both rigid and flexible cables can pass the most stringent C, W and Z tests in the British Standard Code for fire resistance of cables bs6387.
Finally, for the engineering design and application of mineral insulated cables, there is a problem that everyone is concerned about, that is, as pointed out in article 10.1.10-3 of code for fire protection design of buildings gb50016-2014 (2018 Edition), mineral insulated non combustible cables should be used for fire distribution lines.

Don’t say how cheap the cable is. Let’s see if these tests can be passed

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A quality inspection organization has conducted a sampling survey on domestic wires and cables. The results show that the qualified rate of wires and cables in production enterprises that have passed ISO 9000 certification is less than 90%, while the qualified rate of products in small-scale wire and cable production enterprises that have not passed certification is even less than 30%. The quality of wires and AAC Cables in China is worrying.


So, don’t be too busy talking about how cheap the AAAC Cable is. Let’s take a look at the following common testing items?
1. Electrical performance test
It mainly includes conductor DC resistance, insulation resistance, finished product voltage test and insulated wire core voltage test, each of which is very important.
The conductor resistance directly reflects the electrical transmission performance of the cable and directly affects the temperature, service life, voltage drop and operation safety of the cable during power on operation. It mainly examines the material and cross-sectional area of the conductor. If the material of the conductor is poor or the cross-sectional area is seriously insufficient, the DC resistance of the conductor will seriously exceed the standard, This kind of cable laying in the line will increase the loss of current passing through the line, cause the heating of the cable conductor itself, cause the insulation aging and cracking of the coated conductor, cause electric leakage and short circuit of the power supply line, and even cause fire, endangering the safety of personal and property. The standard has strict provisions on the DC resistance of conductors of cables of different specifications, which shall not be greater than the value specified in the standard.
Insulation resistance, finished product voltage test and voltage test between insulated cores all examine the electrical insulation performance of cable insulation layer and sheath layer. Insulation resistance is to detect the resistance of insulating material between two conductors, which shall be large enough to play the role of insulation protection. The voltage test of finished products and the voltage test between insulated cores not only require that the ABC Cable has sufficient insulation capacity, but also that the insulation or sheath material is uniform without impurities, the thickness is uniform enough, and there shall be no invisible trachoma, pinhole, etc. on the surface, otherwise it will cause local breakdown during voltage withstand test.


2. Mechanical property test
It mainly examines the tensile strength and elongation at break of insulation and sheath plastic materials, including before and after aging, as well as the bending test, bending test, load core breaking test, insulation core tear test, static bending test, etc. for the finished flexible cable.
Tensile strength before and after aging and elongation at break before and after aging are the most important and basic indicators of cable insulation and sheath materials. It is required that the materials used as cable insulation and sheath should not only have sufficient tensile strength, not easy to break, but also have certain flexibility. Aging refers to the ability of insulation and sheath materials to maintain their original properties under high temperature conditions. Aging shall not seriously affect the tensile strength and elongation of materials, which will directly affect the service life of cables. If the tensile strength and elongation at break are unqualified, it is very easy to break sheath or insulator during cable construction and installation, or in light The sheath and insulation of cables used in thermal environment are easy to become brittle and break, resulting in exposed live conductors and electric shock.
In addition, because the flexible cable is not fixed laying, there are repeated dragging and bending in use. Therefore, the flexible cable standard also stipulates that dynamic bending test, bending test, load core breaking test, insulation core tear test, static bending test, etc. are added to the finished cable, so as to ensure that the cable meets the requirements in practical use. For example, the dynamic bending test mainly examines whether the stranded wire of the flexible conductor is broken to reduce the electrical transmission performance, or pierce the insulation to reduce the electrical performance of the insulation when the flexible cable is subjected to external mechanical tensile and bending stresses; It is a test method for whether the insulation is deformed or cracked under stress to affect the electrical insulation performance of cables.


3. Performance test of insulation and sheath materials
Including thermal weight loss, thermal shock, high-temperature pressure, low-temperature bending, low-temperature tensile, low-temperature impact, flame retardant performance, etc. These are to examine the performance of plastic materials for insulation and sheath.
For example, the thermogravimetric test is to detect the degree of degradation and volatilization of the material after 7 days of high-temperature aging at 80 ℃; Thermal shock test whether the specially wound insulation surface is cracked after high temperature of 150 ℃ for 1H; High temperature pressure test the elastic retention of insulating materials after high temperature re cooling; All low temperature tests generally refer to the change of mechanical properties under the condition of – 15 ℃, which is to detect whether the cable material becomes brittle, easy to crack or easy to break under the low temperature environment.
In addition, the flame retardant performance of the cable is very important. The test to check this performance is the non delayed combustion test, that is, the finished cable installed according to the standard is ignited with a special flame for a certain time, and the cable is burned after the flame goes out. Of course, the less the burned part is, the better, indicating that its flammability is poor, its flame retardant is good, and it is safer.
4. Sign check
The standard requires that the cable package shall be attached with labels or marks indicating product model, specification, standard number, factory name and place of origin.
Specifications include rated voltage, number of cores, nominal section of conductor, etc; The cable surface shall be printed with continuous signs of manufacturer’s name, product model and rated voltage. The spacing of signs shall be ≤ 200mm (insulating surface) or ≤ 500mm (sheath surface). The contents of signs shall be complete, clear and scratch resistant. This requirement is convenient for users to understand the model, specification and voltage grade of cables to prevent wrong laying.
In addition, the color recommended by the standard shall be preferred for the insulated wire core of the wire, especially the Yellow / Green two-color wire core. This kind of wire is generally used in the power line of electrical products. This special two-color wire is specially used for grounding. The Yellow / Green matching standard also has the following provisions: for each 15mm long insulated wire core, one color shall cover at least 30% of the surface of the insulated wire core, And not more than 70%, while the other color covers the rest of the insulated core, that is, the Yellow / green two colors shall be basically balanced.
5. Structural dimension detection
Including the thickness, thinnest thickness and overall dimension of insulation and sheath.
The thickness of insulation and sheath plays an important role in how much voltage the cable can withstand and its mechanical performance. Therefore, for cables of different specifications, the standard has strict provisions on the thickness, which shall not be lower than the specified value of the national standard. The cable insulation thickness is too thin, which will seriously affect the use safety of the cable, and will bring potential safety hazards such as cable breakdown and electric leakage caused by bare conductor. Of course, the thicker the better, which should not affect the installation. Therefore, the standard also sets an overall dimension requirement to limit it.
Appendix: common certification
1. CCC certification
Compulsory certification is a pass to enter the domestic market.
2. CB certification
Electrical products directly related to personal safety that are conducive to the export of products for families, offices, workshops and similar places. Such products are subject to compulsory certification in some countries, that is, they are allowed to be exported to the country and sold in the market of the country after obtaining the certification certificate of the country. Even in countries without compulsory certification, consumers are willing to buy certified products with certification marks for their own safety.
3. CE certification
It is a pass for products to enter the markets of EU and European Free Trade Area countries. Products certified with CE mark will reduce the risk of sales in the European market:
1) The risk of being detained and investigated by the customs;
2) Risks investigated and dealt with by market supervision institutions;
3) Risk of peer allegations for competitive purposes.
4. UL certification
In the U.S. market, consumers and buyers are more willing to buy products with UL certification marks.

What is the reason for the problem of high voltage cable?

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ACSR Cable is the bridge between power supply equipment and electrical equipment, which plays the role of transmitting electric energy. It is widely used, so faults often occur. The following briefly analyzes the causes of common problems of YJV high-voltage cable. According to the causes of faults, they are roughly divided into the following categories: Manufacturer’s manufacturing reasons, construction quality reasons, design reasons of design unit and external force damage.
1、 Reasons for construction quality there are many cases of high-voltage cable system failure caused by construction quality. The main reasons are as follows:
1. The site conditions are poor, the environment and process requirements of cables and joints are very high when they are manufactured in the factory, and the temperature, humidity and dust on the construction site are not easy to control.
2. During cable construction, small slip marks will inevitably be left on the insulation surface, and semi-conductive particles and sand particles on abrasive cloth may also be embedded in the insulation. In addition, moisture will be absorbed in the insulation due to insulation exposure in the air during joint construction, which will leave hidden dangers for long-term safe operation.

3. The installation did not strictly follow the process construction or the process regulations did not consider the possible problems.
4. DC withstand voltage test is adopted for completion acceptance, resulting in the formation of reverse electric field in the joint, resulting in insulation damage.
5. Due to poor sealing treatment. The intermediate joint must adopt the sealing structure of metal copper shell plus PE or PVC insulation and anti-corrosion coating, and the lead seal is dense during on-site construction, so as to effectively ensure the sealing and waterproof performance of the joint.
2、 The manufacturer’s manufacturing reasons are divided into cable body reasons, AAAC Cable joint reasons and cable grounding system reasons according to different parts.
1. Reasons for cable joint manufacturing high voltage cable joints used to be wrapped, molded, molded and other types, which requires a large amount of work to be made on site. Moreover, due to the limitations of on-site conditions and manufacturing process, there will inevitably be air gaps and impurities between insulating tape layers, so problems are easy to occur. The commonly used types in China are assembled type and prefabricated type. The cable joint is divided into cable terminal joint and cable intermediate joint. No matter what type of joint, the cable joint failure generally occurs at the fracture of cable insulation shield, because this is the part where the electrical stress is concentrated. The reasons for the cable joint failure due to manufacturing reasons include manufacturing defects of stress cone body, insulation filler problems, oil leakage of sealing ring and so on.

2. Cable grounding system cable grounding system includes cable grounding box, cable grounding protection box (with sheath protector), cable cross interconnection box, sheath protector, etc. The common problems are mainly due to the poor sealing of the box and the water inflow, resulting in multi-point grounding and excessive induced current of the metal sheath. In addition, unreasonable parameter selection or poor quality of sheath protector and unstable zinc oxide crystal are also easy to cause sheath protector damage.
3. The reasons for the manufacture of the cable body generally include insulation eccentricity, uneven insulation shield thickness, impurities in the insulation, protrusions in the internal and external shields, uneven crosslinking degree, cable moisture, poor sealing of the cable metal sheath, etc. some conditions are more serious, and faults may occur in the completion test or shortly after putting into operation, Most of them exist in the form of defects in the cable system, causing serious hidden dangers to the long-term safe operation of the ABC Cable.

Underground cable is the trend of urban development

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Install “perspective eyes” for underground cables
In many cities in China, especially in some metropolises or new urban areas, power towers and wires are basically invisible, but thousands of households can use electricity normally. Where does people use electricity come from? In fact, this mainly depends on underground cables to transmit electric energy.
Underground cable is an important way of power transmission. The continuous power supply is realized by establishing underground channels and laying cables. In recent years, scientific and technological personnel have become more and more capable of controlling underground cables, and new technologies have been introduced, popularized and applied, which has laid a solid foundation for the all-round development of underground AAC Cables.


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Underground cable is the trend of urban development
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With the acceleration of China’s economic development and urbanization, the contradiction between power facilities and urban development is becoming increasingly prominent. In order to ensure the power safety of urban residents and keep the city clean and beautiful, it is necessary to reduce the starry overhead transmission lines over the city, set them underground and develop underground ACSR Cables.
According to statistics, the proportion of underground power transmission in some modern cities in the world, such as Berlin, Tokyo, Osaka and Copenhagen, has exceeded 70%. At present, China is also accelerating the construction of overhead wire into the ground, underground cable project and underground comprehensive pipe gallery. By 2017, the total length of Beijing underground cable tunnel is about 800 km. It is expected that by the end of the 13th five year plan, the underground cable utilization rate in Beijing’s core area will increase to 94% and the power supply reliability rate will increase to 99.999%.
In 2014, the State Council issued the guidance of the general office of the State Council on strengthening the construction and management of urban underground pipelines. In 2016, the Ministry of housing and urban rural development issued the 13th five year plan for the development and utilization of urban underground space. These documents require deployment to strengthen the construction and management of urban underground pipelines and ensure the safe operation of the city. As a national new area planning, xiong’an new area will adopt the underground pipe gallery mode for the construction of underground pipe network, and deploy water, electricity and urban transportation to the underground space.
In response to the call of the state, State Grid Corporation of China issued document No. 1459 notice on the planning and use management specification of urban power cable channel and the guidance on the planning and construction of power cabin of urban comprehensive pipe gallery in 2014. In the face of the increasing number of underground transmission lines, State Grid Corporation of China further standardized and strengthened the management of underground cables.


With the rapid development of underground cables, the number of underground pipelines will become larger and larger, and the space will become more and more crowded. Construction, operation and maintenance, management and other parties will face great difficulties and pressure. Therefore, there is an urgent need for an effective method to solve this problem. With the rapid development of information technology, three-dimensional digital technology stands out. Using this technology can realize the “perspective” and intelligent management of underground cables.
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What is 3D digital technology?
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The so-called “three-dimensional digitization” is to use three-dimensional tools (software or instruments) to realize a series of digital operations such as virtual creation, modification, improvement and analysis of the model. Generally speaking, it is to use computer technology to virtually appear any scene and object in real life in the computer, so as to realize the undifferentiated mapping from the real world to the computer virtual world.
The traditional three-dimensional digital technology mainly focuses on the modeling of the physical appearance. Based on the modeling software, the solid appearance is simulated in the computer by using the solid construction and rendering technology, which mainly meets the needs of display. At this stage, the three-dimensional digital technology has been upgraded on the original basis. In addition to truly simulating the appearance of the real object, it also includes a series of relevant information such as accurate size, volume, weight, material and management. The three-dimensional digital model constructed in this way belongs to the information model, which can not only meet the visualization requirements, but also carry out a series of calculation, analysis and management.


In August this year, China Electric Power Research Institute Co., Ltd., a scientific research institution directly under the State Grid Corporation of China, used three-dimensional digital technology to build a digital design system for power cable engineering. The system supports the construction of underground cable information model with voltage level of 35 kV to 500 kV, including different types of underground cable lines such as pipe arrangement, tunnel, comprehensive pipe gallery (power cabin), cable trench, bridge and direct burial. It not only realizes the three-dimensional digitization of the underground cable engineering body, but also supports the above ground buildings in the power corridor 3D visualization of the surrounding environment of other types of underground pipelines. Based on the completed three-dimensional digital model, the safe distance between the underground cable engineering body and the surrounding environment can be calculated, and a series of work such as cable engineering body planning, design, construction and management can be carried out. In addition, in order to save the construction time of underground cable informatization model and improve the model accuracy, the system has built three-dimensional general model libraries such as pipe arrangement, tunnel, cable trench, bridge and working well according to the general design library of State Grid, and provided parametric modeling tools such as pipe arrangement, tunnel, comprehensive pipe gallery (power cabin), AAAC Cable trench, bridge and direct burial, Have the ability to automatically build a 3D model by inputting parameters.