Cable threading, tips you don’t know!

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.

How to determine whether to use 6 / 10 or 8.7/10 for cable selection

When selecting cables, the power cable line design, installation and operation departments shall consider four factors, such as cable service conditions, insulation level, AAAC Cable type and conductor section, which are divided as follows.
1. Cable service conditions
(1) cable rated voltage / u () shall meet the following requirements:
1) the voltage shall meet the requirements of neutral grounding mode of power system, that is, in the neutral ungrounded power system, the voltage of non fault phase increases by times in case of single-phase grounding fault, which is related to the troubleshooting time of system grounding fault.


In IEC standard, power system is divided into three categories. Class a means that any phase conductor of the system is grounded and can be separated from the system within lmin; Class B refers to the grounding of single-phase conductor in the system, the allowable grounding fault time shall not exceed 8h, and the annual cumulative time shall not exceed 125h; Class C is a system that does not belong to classes a and B.
when the cable is used in the neutral effective grounding system, u takes the phase voltage value of the system. For example, 6 / 10kV cable is selected for 10kV system and 21 / 35kV Cable is selected for 35kV system.
When the cable is used for neutral non effective grounding system, the cable with one level higher than the system phase voltage shall be selected. For example, 8.7/10kv cable shall be selected for 10kV system and 26 / 35kV Cable shall be selected for 35kV system.
When the cable is used in class C system and single-phase grounding is allowed for long-term operation, u shall select the line voltage of the system, such as 6 / 6kV cable in 6kV system.
2) the voltage U and shall be equal to or greater than the rated voltage and maximum working voltage of the system where the ACSR Cable is located.
(2) cable transmission capacity. The cable line must meet the transmission capacity of the power system, that is, the selected cable shall have long-term allowable current carrying capacity to meet the system requirements.
For longer cable lines, the line voltage drop of the cable shall also be considered.
(3) cable laying conditions. Cables shall adapt to different laying methods, arrangement methods, metal sheath grounding methods and surrounding medium temperature, etc. The conductor of XLPE cable used for underwater laying shall have longitudinal water resistance. In order to meet the requirements of various laying environments, such as tension, compression, fire prevention, termite prevention and rodent prevention, the armor layer and outer sheath of the cable shall be made of corresponding structural materials.


2. Basic insulation level of cable
the peak value of lightning impulse withstand voltage between each conductor of the cable and the shield or metal sheath, i.e. the basic insulation level bil, shall comply with the provisions in table 1-13.
picture
in table 1-13, the lightning impulse withstand voltage of 220kV and above cable lines has two values, which can be selected according to the protection characteristics of arrester, the characteristic length of impulse wave of cable line and the lightning impulse insulation level of connected equipment.
3. Cable type
(1) comparison of insulation properties between XLPE and oil paper cables. XLPE insulated cable has the advantages of simple production process, short manufacturing cycle, easy installation and maintenance, excellent electrical performance and large transmission capacity. In recent 30 years, the technology of XLPE insulated cable has developed very fast and has been widely used. In terms of insulation performance, compared with oil paper insulation, cross-linked polyethylene insulation has some different characteristics, which are listed in table 1-14.
picture
Note: “air raid” should be “gap”
Oil paper insulated cable has the advantages of excellent electrical performance and long service life. It can be used in general occasions. However, compared with XLPE cable, the manufacturing and installation process of oil paper ABC Cable is more complex and the cost is higher.
oil filled cable with paper plastic composite insulation with low dielectric loss and alkylbenzene synthetic oil with good aging resistance as insulation structure, suitable for voltage levels of 220kV and above. In addition, oil paper insulated cables are also suitable for HVDC transmission lines.
(2) for cable lines of 110kV and below, XLPE insulated cable is generally the preferred variety. For distribution cables of 1kV and below, in addition to polyvinyl chloride (PVC) insulated cables for lines with light load, cross-linked polyethylene insulated cables shall also be selected.
Note: at present, 1-500 cables are mainly XLPE cables, and only some stocks of oil paper insulated cables and oil filled cables are left.


(3) ethylene propylene rubber (EPR) insulated cable is suitable for 35kV and below lines. This kind of cable is suitable for underwater laying because of its good moisture resistance, but its price is expensive.
4. Conductor section
copper conductors are generally used for power cables. The selection of conductor section shall meet the requirements of cable line transmission capacity and maximum short-circuit thermal stability of the system at the same time. And comply with “economic optimization of cable conductor size”.
in urban low-voltage power grid, four core cable is generally used, that is, in addition to three-phase conductor, there is a neutral line passing through three-phase unbalanced current and having protective grounding effect. The section of neutral wire shall generally be 30% ~ 60% of the conductor section of each phase. In the low-voltage power grid with large three-phase unbalanced current, four core low-voltage cables with equal cross-section shall be selected. The three core cable plus another insulated conductor cannot be used as the neutral wire to connect to the three-phase four wire low-voltage power grid, because in this way, there will be unbalanced current passing through the metal sheath and armor layer of the three core cable to heat it, thus affecting the transmission capacity of the cable.

How to choose wires for home decoration

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

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.

On the service life of control cable

The service life of control cable is determined by the air oxidation induction period of sheath raw materials. Generally, the design scheme of control cable is applied for 20 years, which is the most applied life of control cable. Although the specific daily life is likely to be longer, from the perspective of safety, the design scheme period is the most life of control cable.

Life of control cable
Elements endangering the service life of control cables and ways to increase the service life of control cables:
1. The control cable does not have to return to moisture to avoid heat and corrosion. Because the sheath of the cable has a certain maintenance effect on the cable, the corrosion is more harmful to the cable in case of heat.
2. Control cables do not have to be overloaded. Overload application of the cable will cause immediate damage to the insulation and sheath of the cable, endanger the service life of the cable or destroy the cable immediately.
3. For the route of old engineering buildings, if it is found to be swallowed or wet by water, especially if the route is worn and brittle, electric welders should be asked to repair it immediately.
4. The control cable shall prevent common faults of cable connector, which will lead to ABC Cable short-circuit fault, which will not only damage the cable, but also destroy household appliances.


5. Control cable commodity itself: select national and industrial standard cables as much as possible. Cost-effective non-standard cables are very easy to cause short-circuit fault, and the service life of non-standard AAC Cables is short.
6. Control the natural environment and temperature of the cable. The external natural environment and heat source where the control cable is located will also lead to excessive temperature of the control cable, penetration of the insulation layer, and even explosion and fire.

Mineral insulated cables in fire power distribution

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.

Causes of appearance defects of five kinds of rubber sheathed cables

In the production process of rubber sheathed AAC Cable, there are often appearance defects, such as unsmooth surface; Clinker particles (early vulcanized rubber particles) or impurities on the surface; Scratch and scratch on the surface of wires and cables; Surface collapse; There are hemp patterns on the surface.

The following are five common causes of appearance defects of rubber sheathed ACSR Cables:
1. The die sleeve bearing line is too long or too short, the die opening is not smooth and the hole diameter is too large; Low head, die or body temperature; Low plasticity of rubber may lead to unsmooth surface of rubber sheathed cable.
2. The supplied rubber is not clean and contains impurities; The scorch time of rubber is too short; The temperature of rubber extrusion body, head or die is too high; The rubber flow in the head is not smooth, and there is a dead corner of rubber retention; Unsmooth screw and viscose may lead to clinker particles (early vulcanized rubber particles) or impurities on the surface of rubber sheathed cable.
3. The die sleeve is not smooth and has no chamfer; Impurities or clinker particles block the die mouth; Abrasion of dragging pipe in vulcanization pipe; The small aperture of the sealing rubber gasket at the outlet of the vulcanization pipe may cause scratches and scratches on the surface of the rubber sheathed cable.
4. The hole diameter of die sleeve is too large; The gap between the outer strands and monofilaments of the conductive core is too large, and the outer diameter of the cable core is uneven; The rubber has small plasticity and poor viscosity; Impurities in rubber; Small mold distance and pressure may cause the surface collapse of rubber sheathed cable.
5. The hole diameter of die sleeve is too small; Insufficient rubber extrusion and insufficient filling of wire core gap; Conductive core or cable core jumper; Short distance between molds may lead to twist on the surface of rubber sheathed cable.

Rubber sheathed cable is a kind of soft and movable cable with multi strand fine copper wire as conductor and wrapped with rubber insulation and rubber sheath. Generally speaking, it includes general rubber sheathed flexible cable, electric welding machine cable, submersible motor cable, radio device cable and photographic light source cable.
Rubber sheathed cables are widely used in various electrical equipment, such as mobile power lines for daily appliances, electric machinery, electrical devices and appliances. At the same time, it can be used under indoor or outdoor environmental conditions. According to the external mechanical force on the cable, the product structure is divided into light, medium and heavy. There is also appropriate connection on the section.
General light rubber sheathed cables are used in daily electrical appliances and small electric equipment, which are required to be soft, lightweight and good bending performance;
Medium sized rubber sheathed cables are widely used in agricultural electrification except for industrial use;
Heavy duty cables are used in such occasions as port machinery, searchlights, large hydraulic drainage and irrigation stations in domestic industry, etc. This kind of products have good universality, complete series specifications, good and stable performance.
Waterproof rubber sheathed cable and submersible pump cable: mainly used for supporting submersible motor, with models of JHS and JHSB.
Cables for radio devices: now we mainly produce two kinds of rubber sheathed ABC Cables (one shielded and one unshielded), which can basically meet the requirements. The models are wyhd and wyhdp.
Photographic cable products: with the development of new light sources, they have small structure and good performance, meet the needs of indoor and field work, and gradually replace some old products with heavy weight and poor heat resistance.
Operation method:
1. Set the temperature and time according to the vulcanization system of the compound
2. Wipe and wash the repair place with rubber and ink diluent, especially the joint shall be fully treated.
3. Cut the repair rubber properly according to the size of the gap, and pay attention not to be too much or too little,
4. Plug the cut rubber in the gap, and pay attention that the rubber shall not be higher than the circumference of the wire.
5. Wrap it with high temperature resistant PP tape. And put it into the tubular die cavity slightly smaller than the wire diameter, lock the upper and lower dies, and make the supplemented position have a certain pressure. Note that the die cavity diameter is slightly smaller than the wire diameter by 0.1 ~ 0.2mm.
6. When the vulcanization time is up, take out the product. If a small amount of rubber overflows, repair it with a sharp blade and wipe it with diluent.

The world’s largest copper mine enters the countdown to strike

Union members of Escondida copper mine, the world’s largest copper mine in Chile, voted against the latest contract offer made by the mine owner and decided to go on strike. Many industries are worried that the global economy will continue to recover from the impact of the COVID-19 pandemic, which could lead to disruption in the supply of ABC Cables, a key metal.
Escondida copper mine is located in Atacama Desert in northern Chile. It is the largest copper mine in the world, and its output accounts for almost 5% of the total global copper supply. BHP Billiton currently manages the copper mine business and holds about 58% of the copper mine. Other investors include Rio Tinto and Mitsubishi Corp.


99.5% of union members reject BHP Billiton’s new contract
The union of Escondida copper mine said in a statement late Saturday that the union voted overwhelmingly against the new contract proposal of the mine owner (BHP Billiton). 2164 miners (about 99.5% of the total) rejected the proposal, and only 11 supported it.
The trade union said that the contract proposal did not include the terms previously required by the trade union: providing one-time bonuses for workers to maintain mine operations during the epidemic, performance-related remuneration and improved career development plans, and enabling workers’ children to enjoy the same educational benefits as those of supervisors.
BHP Billiton spokesman previously said in an e-mail statement on Friday that “the new offer proposed by the company improves the previous conditions and incorporates new benefits on issues that workers attach great importance to.” However, the trade union statement refuted that the so-called benefits in Escondida’s latest contract offer to the miners were actually based on extending working hours, increasing job requirements and other more demanding conditions for workers.
“We hope that this overwhelming vote will sound a decisive alarm and prompt BHP Billiton to start substantive negotiations to reach a satisfactory agreement – if they want to avoid the most costly long-term trade union conflict in Chile’s history,” the trade union statement said.


Historically, miners at Escondida copper mine also held a strike in 2017, which lasted for 44 days at that time.
Strike Countdown: last chance during government mediation
After the announcement of the AAC Cables of the union vote, BHP Billiton has said it will ask the government to intervene in mandatory mediation.
“The company’s interest is always to reach an agreement with employees, which is why we maintain an open dialogue and occupy all available space for this purpose,” the company said in a statement BHP Billiton did not comment on the Union’s specific request.
Analysts said that according to the local law of Chile, miners must continue to work during the government’s forced mediation, and the mediation period is up to 10 days. Therefore, although the strike has entered the countdown, it is not a certainty at present. In all walks of life, union voting to authorize strikes is often used as a negotiation strategy.
Eleni joannides, an analyst at wood Mackenzie, a commodity consulting firm, said before the union vote: “whether the market and prices will be significantly affected will depend on whether there will be a strike in about 10 days.” She also pointed out that “at current prices, Escondida’s negotiations seem to have affected the market.”
Will the strike push copper prices higher?
Copper is a key raw material for manufacturing wires and motors, and is widely used in many fields such as construction industry. Earlier this year, copper prices soared to a record high as the market expected that the global economy would continue to recover and the energy transformation would require a large amount of copper to produce electric vehicles and renewable energy.


Novel coronavirus pneumonia has been faced with severe challenges before mining operations. BHP Billiton said on July 20 that due to a number of epidemic prevention measures, the operation of several Chilean copper mines including Escondida has not been interrupted, but the number of employees has been reduced. The company reported that copper production at Escondida copper mine is expected to decline by 10% in the current fiscal year. BHP Billiton also said that due to the rising infection rate of the epidemic, the company is expected to face continuous operational challenges in Chile.
Although some analysts, including joannides, believe that the recent rise in copper prices has reflected people’s expectations of the interruption of mine operations, other analysts are still worried that the strike may push copper prices further to record highs. LME copper prices climbed to a six week high of $9924 last week after hitting an all-time high of $10747.50 in May.
Morgan Stanley said that the contract negotiation of Chilean copper mine is a key focus of short-term copper price trend. The bank said that although the copper market is expected to have surplus in 2022 due to output growth exceeding demand, the ACSR Cables will still face copper shortage this year.
Sabrin Chowdhury, an analyst at Fitch solutions in Singapore, also said that the strike risk of Escondida copper mine is driving up the short-term prospect of copper prices. Copper prices will also benefit from severe floods in Central China and the weakness of the US dollar.
Chowdhury pointed out, “whether the strike occurs or not, it will cause panic among investors, because copper stocks on the exchange have fallen sharply in recent weeks. The market is already tight, and the demand exceeds the supply that is trying to return to the pre epidemic level. If the strike does happen, copper prices will reach a new record high, higher than in May“

Causes and treatment of unqualified strand products

1. Scope of application
This specification is applicable to the stranding of copper aluminum strand, steel cored aluminum strand and power ABC Cable conductor core.
2. Equipment parameters
2.1 equipment name: jlk-500 / 12 + 18 + 24 frame stranding machine
2.2 equipment capacity (technical parameters)
a. Single wire diameter: 1.5 ~ 5mm (copper) 1.8 ~ 5mm (aluminum)
b. Maximum stranded outer diameter: 45 mm
c. Maximum traction speed: 69m / min
d. Maximum speed of frame: 12 discs R / min 173m
18 discs R / min 152 M
24 discs R / min 133 M
e. Equipment stranding pitch: 12 reels mm 56 ~ 962
18 disc mm 64 ~ 1095
24 disc mm 73 ~ 1245
f. Traction wheel diameter: φ 200 mm
g. Specification of pay off panel in frame: PND 500 mm
h. Specification of central pay off panel: pn800 ~ pn1600 mm
1. Specification of take-up reel: pn1250 ~ pn2500 mm
j. Main motor power kw: 75 (DC)


3. Preparation before production:
3.1 check whether all electromechanical equipment and transmission devices are normal, check the lubrication system, and apply pressure to the equipment according to the “oil standard”
Lubricating oil.
3.2 put the production tools and measuring tools (vernier caliper with accuracy of 0.02 mm and micrometer with accuracy of 0.01 mm) in a place convenient for use
A safe place and check whether the measuring tools are accurate.
3.3 according to the production plan, check whether the diameter of the single line is consistent with the process, and whether the single line is bruised, scratched, oxidized, etc,
Unqualified single line shall not be used.
3.4 prepare pressing wheel, die and other molds according to process requirements.
3.5 the take-up reel shall be selected according to the outer diameter, manufacturing length and process requirements of the strand, and the quality of the take-up reel shall be checked. The deformation is serious
Burrs on the edge of the side plate shall not be used.
3.6 the successor must understand the variety, specification and quality of twisted products and make clear the responsibility.
4. Key points of operation
4.1 before start-up, carefully check the correctness of operating parts, the reliability of interlocking mechanism and reel jacking, and the locking mechanism can make
The reel must be tightened and locked reliably, and the fence protection of the whole machine shall be set in place to ensure safety.
4.2 no matter under any circumstances, observe the changes of current, AAC Cables, temperature and other parameters at all parts at any time
In addition, any large fluctuation is dangerous and should be stopped immediately for inspection. Start up after troubleshooting.


4.3 according to the production plan and process requirements, the winding and branching shall be arranged according to the specified structure. When hanging the coil, pay attention to the balance and correct swing of the coil
The setting out direction of the reel shall be the same as that of the reel in a frame. The top clamp shall be screwed first and then locked and fixed with interlocking device,
Prevent accidents. Adjust the tension to achieve basic consistency.
4.4 the single line shall not be scratched or scratched when passing through the single line through the threading hole. The single line must be evenly separated through the threading hole or distribution board
Cross each other.
4.5 when installing the die, it must be aligned with the center, and check whether the die quality is good. The surface of the inner hole of the die or the pressing wheel and the conductor
The surface contact part shall be smooth, otherwise it shall not be put into use.
4.6 adjust the pitch and rotation direction of each section according to the process requirements.
4.7 lead wire: tightly wound outside the steel wire rope with a single wire to form a whole. Then start pulling and guiding from the die base of disc 12
Then 12 coils and 24 coils, gradually add stranded wires outside the core wire, and wind at least 4 turns on the traction wheel according to the branching slot.
Stop the machine when the conductor head is led to the reel. Replace the reel, remove the conductor head, and wrap the head tightly with tape and wire,
Prevent looseness. Insert the head into the threading hole on the disc core / side plate, extend the head for at least 1m, and use homogeneous wire to thread the coil
Wrap the brace for several turns and fix it firmly.
4.8 after the stranding machine is adjusted, the process inspection must be carried out comprehensively again, including the structure, direction, pitch
Start up after the outer diameter and number of strands fully meet the process requirements.
4.9 during the production of sector conductors, the sector height shall be adjusted at a slow speed and the pressure roller height shall be adjusted at the same time. Static pressure adjustment is not allowed
Roll to prevent breakage caused by uneven deformation of single line.
4.10 start up after process adjustment. After the strand reaches the traction wheel, actually measure the process parameters, such as pitch, outer diameter
The sector is high, and each process parameter shall be subject to the actual measurement, and each process parameter shall be filled in the self inspection form.
4.11 during the normal operation of the machine, the operator shall not leave the post without authorization, and it is found that the equipment is abnormal and the product quality is affected
In case of any problem, stop the vehicle for inspection in time.
4.12 when stopping, turn off the power supply and stop slowly. Emergency stop is allowed under special circumstances.
4.13 if the single line is allowed to have joints, the joints shall meet the requirements of the process card.
5. Precautions and treatment methods
5.1 always observe whether the electromechanical equipment and various instruments are in normal state.
5.2 regularly check whether the outer diameter (or fan height) pitch of the product is consistent with the process requirements, and fill in the self inspection form with the inspection results; If not, stop the vehicle for inspection and start the vehicle after handling.
5.3 pay attention to the surface quality and structural dimension of the line during the replacement of specifications, joints, adjustment plates and normal start-up.
5.4 the sector height of the compacted wire core must be controlled within the range specified in the process documents. If the requirements are not met, the pressure shall be adjusted in time
Wheel.
5.5 the take-up reel shall meet the requirements of users and products.
5.6 the wiring arrangement shall be tight and tidy, and no pressing, disorder, scratch and other phenomena are allowed. The finished product line shall be full if the user has special requirements
Meet user requirements. The distance between the outermost layer and the edge of tooling side plate shall not be less than 50mm
5.7 the length of the downlead shall meet the user’s requirements or the conductor wiring length requirements. After each reel is completed, the process shall be filled in
The product circulation card shall indicate the workshop, machine, model, specification, length, number of sections, shift, production date and product manufacturing information
Kuang et al.


6. After shift work:
6.1 cut off the main power supply after the work is completed.
6.2 report the equipment operation, product quality, problems, product specification and length of the shift to the successor in detail
The handover is clear.
6.3 keep the production process records of the shift, sort out the waste, clean the equipment, sort out the tools and measuring tools, clean the working place and clean the equipment
Do not use the mold temporarily and hand it over to the mold warehouse for storage.

What is the difference between yttwy and ng-a btly mineral insulated cables?

Ng-a (btly) series isolated fire-resistant ACSR Cables are flame-retardant and fire-resistant cables. The insulating layer is phlogopite tape (fire resistance temperature 750 ℃ ~ 800 ℃), the sheath is aluminum tube (fire resistance temperature 660 ℃), and the outer sheath is plastic. It is not in the same category as yttw and bttz mineral insulated cables. We can make a comparison from the following technical data.
The structure diagram of yttwy copper core copper sheathed mineral insulated cable and ng-a btly isolated (flexible) mineral insulated cable is as follows:
(1) Yttw series metal sheathed inorganic mineral insulated cables are fireproof cables composed of copper core, copper sheath and inorganic mineral insulating materials. They are produced in strict accordance with the national industrial standard JG / t313-2014.
1) Yttw series metal sheathed inorganic mineral insulated cables are wrapped with natural inorganic mineral insulating tape (high temperature resistance above 1370 ℃). The sheath adopts copper sheath (high temperature resistance of 1083 ℃), which is continuously rolled, has fast heat dissipation and can be bent.
2) Metal sheathed inorganic mineral insulated cable can be made into pre branch cable to realize trunk power distribution system.

(2) Ng-a (btly) series isolated fire-resistant ABC Cables are organic and inorganic mixed fire-resistant cables, which will produce low smoke and low toxicity during combustion, which can not be compared with the smokeless and non-toxic of inorganic mineral insulated cables.
1) The refractory layer is made of glass fiber cloth, which is softened and damaged at about 840 ℃;
2) The filling layer adopts hydrated metal oxide, which is a gypsum like semi fluid containing organic components. During combustion, water vapor escapes and colloidal becomes solid (aluminum oxide). It is unclear whether it is toxic or not;
3) The isolation sleeve is generally cross-linked polyethylene (XLPE), with low smoke and low toxicity during combustion;
4) The metal sheath and aluminum material have poor mechanical and electrical properties. The flame temperature melts at 660 ℃, so it is not suitable for the metal sheath of fireproof cable;
5) The mineral insulation layer adopts phlogopite tape. The fire resistance characteristic of phlogopite is only class B (750 ℃ ~ 800 ℃), which can only be used as class B fire-resistant cable. It cannot be used in class A (950 ℃ ~ 1000 ℃) fire-resistant cables.
To sum up, yttw series metal sheathed inorganic mineral insulated cable has the following essential advantages compared with ng-a btly
a. The cable structure shall be free of any combustible organic material;
b. The high temperature resistance of the cable is greatly improved, and the calorific value is zero;
c. The cable is non combustible as a whole;
d. Non toxic and smokeless during cable combustion;
e. The thermal overload and long-lasting withstand voltage performance of the cable are greatly improved;
f. The durability of the cable has doubled.


Moreover, there is no unified standard for ng-a (btly) series isolated fire-resistant cables in China, and only individual manufacturers produce them according to enterprise standards.