The impact of “anti-dumping” on the domestic optical fiber and cable industry

Recently, the optical communications section is relatively hot. In the process of communicating with friends, it seems that many people are very concerned about the impact of the Ministry of Commerce on the impact of the anti-dumping of optical fiber preforms from US and Japanese manufacturers on domestic enterprises, especially worried about the implementation deadline of August 19, 2017 After the expiration, the domestic optical fiber and aerial bundled cable  b231 business situation came to an abrupt end.

So what is the reason for this “anti-dumping”, what is the specific content, and what impact will its implementation and future expiration have on the domestic optical fiber and cable market?

1. The whole story of the “anti-dumping” case concerning optical fiber preforms in the United States and Japan.

—On May 18, 2015, the Ministry of Commerce issued Announcement No. 15 of 2015, announcing the preliminary ruling of the anti-dumping investigation on imported optical fiber preforms originating in Japan and the United States: to determine the existence of imported light rod products from the United States, Japan and other countries Anti-dumping behavior. From the side, it shows the state’s attitude to support the development of domestic optical communication enterprises.

—On August 19, 2015, the Ministry of Commerce issued Announcement No. 25, announcing the final decision on the anti-dumping case against imported optical fiber preforms originating in Japan and the United States. The Ministry of Commerce determined that there was dumping of imported optical fiber preforms originating in Japan and the United States, China’s domestic industry was threatened with material damage, and there was a causal relationship between dumping and the threat of material damage, and decided to implement anti-dumping measures on the product.

—On March 6, 2015, the Ministry of Commerce issued an announcement that in view of the special aerial bundled cable (abc)  and complicated anti-dumping investigation of imported optical fiber preforms originating in Japan and the United States, the Ministry of Commerce decided to extend the investigation period of this case by 5 months , That is, the deadline is August 19, 2015. This makes the anti-dumping investigation of optical fiber preforms that have been controversial when they first emerged, once again in a halo.

—On May 18, 2015, the Ministry of Commerce issued Announcement No. 15 of 2015, announcing the preliminary ruling of the anti-dumping investigation on imported optical fiber preforms originating in Japan and the United States: to determine the existence of imported light rod products from the United States, Japan and other countries Anti-dumping behavior. From the side, it shows the state’s attitude to support the development of domestic optical communication enterprises.

—On August 19, 2015, the Ministry of Commerce issued Announcement No. 25, announcing the final decision on the anti-dumping case against imported optical fiber preforms originating in Japan and the United States. The Ministry of Commerce determined that there was dumping of imported optical fiber preforms originating in Japan and the United States, China’s domestic industry was threatened with material damage, and there was a causal relationship between dumping and the threat of material damage, and decided to implement anti-dumping measures on the product.

What are the common types of aluminum alloy cables

Aluminum alloy cable (abbreviation: alloy cable) is different from the traditional copper core cable. This aluminum alloy cable uses high elongation aluminum alloy material. The pure aluminum is added with iron and other materials, and undergoes a compact stranding process and special Annealing treatment can “squeeze” the voids in the alloy aluminum to reduce the cross-sectional area, so that the cable has better flexibility. The safety performance of this kind of aluminum alloy cable is also better than that of copper core cable. When its surface is in contact with air, it can form a thin and strong oxide layer, which can withstand various corrosions. Even when overloaded or overheated for a long time, the stability of the connection can be guaranteed. To achieve the same electrical performance, the direct purchase cost of aluminum alloy cables is 40% lower than that of copper cables, and the general construction and installation costs can be saved by more than 20%.

1.Aluminum alloy (STABILOY) non-armored AC-XLPE insulated PVC sheathed cable:
AC-XLPE insulated PVC sheathed cable, aluminum alloy non-armoured cable is made of conductor, the cross-section specification is from 10mm² to 400mm², the core is grade compressed strand type, which fully complies with CSA C22.2 NO.38 about ACM alloy conductor Standards, also in line with the latest editions of GB 12706.1 and IEC 60502.1.
Aluminum alloy (non-armoured cables use cross-linked polyethylene insulation with a working temperature of 90℃ and black PVC outer sheath, which have a very wide range of applications where no armored mechanical protection is required. They can be used in non-combustible buildings, such as Feeder lines for lighting, sockets and other equipment in office buildings, hotels, shopping malls and factories.

Aluminum alloy cable is an aluminum alloy conductor specially developed for construction application cables. The safety performance, electrical performance, and mechanical performance of aluminum alloy cables have been tested by the China Quality Certification Center and the National Wire and Cable Quality Supervision and Inspection Center, and all meet the requirements of China’s National Standards (GB). Aluminum alloy cables have been successfully used in North America for more than 30 years and are advanced and mature technologies and products.

2.Self-locking armored cable:
ACWU90 is a highly flexible self-locking aluminum armored, PVC outer sheath, 90℃ cross-linked polyethylene waterproof insulated single-core or multi-core cable, with an equipotential bonding bare conductor. Because of the FT4 grade PVC outer sheath, ACWU90 can be directly laid and buried in the ground, and is suitable for corrosive environments and non-combustible buildings. ACWU90 reduces the construction difficulty and labor cost caused by pipeline wiring.

The alloy cable has been assembled in the factory with a highly flexible self-locking armor and a sealed PVC outer sheath. There is no need for pipelines and accessories and manual procedures such as intensive drawing, buckling and pipe threading. ACWU90 has passed the CSA certification and can be used in open or dark wiring in dry and humid environments, as well as in the first-level hazardous environment in zone 1 and 2, as well as the second and third-level hazardous environments. Laying method: Brackets, ladders, trays and cable clamps can be used for indoor laying. Outdoors can be directly buried, cable trench, cable tunnel and other methods. ACWU90 is equipped with calibration marks per meter to accurately determine the cable length.

Aluminum alloy cable, ACWU90 multi-core cable is made of conductor, and the cross-section specification ranges from 10mm² to 400mm². It is fully compliant with IEC 60502.1 and GB 12706.1 standards, and can also provide various specifications of low-smoke and halogen-free products according to customer requirements. Both AC90 and ACWU90 can be used as user incoming cables. The self-locking armored technology used makes the cables more flexible and easier to install than conventional armored cables. In fixed installation, the bending radius of the self-locking armored cable can be only 6 times the outer diameter of the cable.

3AC90 type multi-core aluminum alloy self-locking armored aluminum alloy cable:
AC90 is a highly flexible self-locking aluminum armored, 90℃ cross-linked polyethylene insulated single-core or multi-core cable, with an equipotential bonding bare conductor. The AC90 cable is assembled in the factory with high-flexibility self-locking armor, without the need for pipelines and accessories, and manual procedures such as intensive drawing, buckling and pipe threading.
AC90 type has been used in non-combustible buildings, such as office buildings, hotels, shopping malls and factories in the lighting, sockets and other equipment feeder lines, can be used as users on the ground and in dry environments as the incoming cable. AC90 can be installed on the cable tray (perforated tray, non-perforated tray and ladder frame), and can also be laid along the wall and the top by using a bracket or a cable clamp.
AC90 multi-core cables are made of conductors, with cross-sectional specifications ranging from 10mm² to 400mm². It has passed CSA certification and can be used for open or dark wiring in a non-humid environment, and has the same performance as pipeline laying. AC90 is a flame-retardant Class A, low-smoke and halogen-free type, which fully complies with the standards of IEC 60754, GB17650.1 and IEC 60502.1\GB 12706.1.


What should we pay attention to when installing cables?

Matters needing attention in Electrical cable installation:

1. Keep a distance of 2m when the mine cable is installed in parallel with the heating pipeline, and keep 0.5m when crossing.
2. When the cable is installed in parallel or across other pipes, a distance of 0.5m must be maintained.
3. When the cable is directly buried, the depth of the 1-35kV cable should not be less than 0.7m.
4. When the cables of 10kV and below are installed in parallel, the mutual clear distance is not less than 0.1m, the 10-35kV is not less than 0.25m, and the distance when crossing is not less than 0.5m.
5. The minimum bending radius of the cable must not be less than 15D for multi-core cables and 20D for single-core cables (D is the outer diameter of the cable).

6. Cable joints of 6kv and above.
A. When installing the cable terminal head, the semi-conductive shielding layer must be stripped off, and the insulation must not be damaged during operation. Knife marks and unevenness should be avoided, and sandpaper should be used to smooth it if necessary; the shielding end should be flat and graphite The layer (carbon particles) is removed.
B. The copper shield and steel armor of the plastic insulated cable end must be well grounded. This principle should also be followed for short circuits to avoid induced electromotive force at the end of the steel armor during unbalanced operation of three-phase, or even “fire” and burn the sheath Wait for the accident. The grounding lead wire should be tinned braided copper wire, and soldering iron should be used when connecting with the copper tape of the cable. It is not suitable to use a blowtorch to seal and solder, so as to avoid burning insulation.
C. The three-phase copper shield should be connected to the ground wire separately. Note that the shield ground wire and the steel armor ground wire should be led out separately and insulated from each other. The position of the welding ground wire should be as low as possible.
7. The basic requirements for cable ends and intermediate joints: a. Good conductor connection; b. Reliable insulation, it is recommended to use radiation cross-linked heat-shrinkable silicone rubber insulating materials; c. Good sealing; d. Sufficient mechanical strength, Can adapt to various operating conditions.

8. Electrical Power Cable end must be waterproof and corroded by other corrosive materials to prevent breakdown due to aging of the insulation layer caused by water trees.
9. Cable loading and unloading must use cranes or forklifts. Horizontal transportation or laying flat is prohibited. When installing large cables, cable cars must be used to prevent cables from being damaged by external forces or scratching the insulation layer due to manual dragging.
10. If the cable cannot be laid in time for some reason, it should be stored in a dry place to prevent sun exposure and water ingress into the cable end.

Precautions for testing cross-linked cables

In recent years, silane cross-linked polyethylene cable material (hereinafter referred to as XLPE) has become the leading material for low-voltage cross-linked cable insulation because of its simple manufacturing equipment, mature technology, convenient operation, and low overall cost.

At present, the commonly used XLPE is the two-step XLPE. When the cable factory produces the insulated core, the polyethylene (PE) grafted with silane and the catalyst masterbatch are mixed in a certain proportion and extruded in a common extruder. Then complete the cross-linking in hot water or steam; the other one-step method XLPE is made by the cable material manufacturer, which mixes all the raw materials together by a special method according to the ratio, and the cable factory directly completes the grafting and grafting in one step in the extruder. Extrude the insulated core, and then complete the cross-linking under natural conditions. The common point of these two types of XLPE is that no special extrusion equipment is needed and the cross-linking process is relatively simple. As long as the raw materials and process conditions meet the requirements, it can be made into an insoluble and infusible thermosetting plastic. Compared with thermoplastic PE, its heat-resistant deformation and mechanical properties at high temperature, environmental stress cracking, aging resistance, chemical resistance, etc. have been improved or improved, while the electrical properties remain basically unchanged, and the long-term work of the cable The temperature is increased from the original 70°C to 90°C, thereby improving the short-term current withstand capability of the cable. In summary, XLPE low-voltage cables have become the main products of cable manufacturers in recent years.

As a third-party inspection agency, this type of cable is also increasing year by year. How to accurately provide the test results of the thermal extension and aging performance of this type of product? Inspectors are faced with some special circumstances. The following is an analysis:

First, the problem of abnormal thermal extension of XLPE insulation. When testing, the author often finds that the elongation rate of XLPE cable insulation under load in the 200℃ thermal extension test greatly exceeds the requirements specified in the standard, or the sample is put into the oven and melted in a short time. If the test is repeated immediately with the original sample, The reproducibility of the results is very good. According to the routine, as long as the test method is correct and the sampling is correct, a conclusion can be drawn based on the test results. However, for XLPE, this may be a great risk. Because the cross-linking process of ACWU90 AC90 Cable is a slow chemical change process related to temperature, humidity, time, insulation thickness and other factors, especially the naturally cross-linked XLPE insulation material is affected by the above factors to complete the cross-linking. There will be a big difference in time, and it is entirely possible that the natural cross-linking has not been completed within the prescribed test period. Once the natural cross-linking is completed over time, its performance may meet the requirements of national standards. For such situations, the author believes that under the premise of reflecting the current situation of the sample, we should not rush to determine, but should provide the sample with a condition to promote crosslinking-soaking in hot water at 90°C±2°C Do the hot extension test after 4 to 5 hours. Practice has proved that the test results at this time can be used as a basis for judgment. It is worth mentioning that individual manufacturers are pursuing commercial profits one-sidedly, using the similar characteristics of PE and XLPE to pretend to be XLPE, and PE will not produce cross-linking changes no matter what conditions are provided to promote cross-linking. In terms of performance, it does not meet the requirements of XLPE at all, which is the same as the fact that stones cannot hatch chicks. This requires inspectors to have the ability to identify true and false, good and bad XLPE. In fact, through observation and work accumulation, we can distinguish whether the tested sample is under-crosslinked, inferior XLPE, or PE is used according to the fusing time and fusing point after the sample is placed in the oven. However, as a third-party inspector, you cannot draw conclusions based on experience alone, and must make judgments based on real data.

Second, the problem of the change rate of XLPE heat aging test exceeding the standard. When testing, if you get the sample, prepare it immediately, and put it in the oven for aging as usual, the tensile strength and elongation at break will often exceed the standard after aging, and you must be cautious in judging this result. This phenomenon is not entirely caused by poor aging performance, it may be because XLPE has not been completely cross-linked (from the time curve of XLPE cable material thermal extension with warm water placement, it can be seen that when the thermal extension is qualified, it does not represent the sample Completely cross-linked), and after being placed in the aging box, XLPE is still completing its cross-linking process, which leads to an increase in tensile strength, a decrease in elongation at break, and the final rate of change exceeds the standard. Due to the long time to complete the aging, it will be troublesome to discover the problem once the test is over. Therefore, it is necessary to thoroughly crosslink the sample before performing the aging test.

In summary, it can be seen that special factors should be considered to determine the thermal elongation and thermal aging performance of XLPE. Personnel engaged in third-party inspections can neither make a hasty conclusion on the results of the test, because doing so involves the risk of misjudging qualified products as unqualified; nor can they avoid these two tests because it is difficult to draw conclusions. This may cause substandard products or counterfeit products to be missed. Therefore, it is necessary to exclude the possibility that the sample has not been cross-linked or completely cross-linked before performing the above two tests. We advocate the use of scientific and reasonable test methods to provide fair and reliable test results.

The structure and specification of YJV cable

Let me introduce to you what YJV means, yj means cross-linked polyethylene, v means polyvinyl chloride, then YJV is cross-linked polyethylene insulated PVC sheathed cable, and the range of use is for the rated voltage (U0/U) 0.6/1—26/35kv power line transmission and distribution, the rated temperature of the cable conductor is 90 degrees when in use, and the temperature of the cable conductor does not exceed 250 degrees when short-circuited (the duration does not exceed 5S). It has the advantages of light weight and simple structure, so it is widely used in urban power grids.
YJV cable model specification

The cores of YJV cables are single core, 2 cores, 3 cores, 4 cores, 5 cores, 3+1, 3+2, 4+1. 3+1 represents 3 phase wires and 1 ground wire, 3+ 2 represents 3 phase wires and 2 ground wires, 4+1 represents 4 phase wires and 1 ground wire. According to the standard model, the specific size specifications include: 1 square, 1.5 square, 2.5 square, 4 square, 6 square, 10 square, 16 square, 25 square, 35 square, 50 square, 70 square, 95 square, 120 square, 150 Square, 185 square, 240 square, 300 square. For example, the YJV 3*120+2*70 cable is a cable composed of three 120 square phase wires and two 70 ground wires.

The combination between the ground wires is regulated by the standard, so the 70 square behind the YJV 3*120+2*70 cable can be omitted. The main specifications of the YJV cable range from 1 square to 240 square meters (also can be customized separately). It is a cable used for transmission and distribution of electric energy. It is often used in urban underground power grids, lead-out lines of power stations, internal power supply of industrial and mining enterprises, and underwater transmission lines that cross rivers and seas. In power lines, the proportion of cables is gradually increasing. Power cable is a cable product used to transmit and distribute high-power electrical energy in the main line of the power system, including 1-500KV and above various voltage levels, various insulated power cables.

How to prevent the electric power cable fire

The selection of XLPE insulated power cables should follow the following principles: the rated voltage should be greater than or equal to the voltage at the installation point.          

1. Short-circuit fault caused by insulation damage

The protective layer of the cable will be damaged during the laying process, or the insulation layer of the cable will be damaged by mechanical damage during the operation, resulting in interphase or damage to the protective layer of the cable, and the arc will cause the protection of the insulating material and the outer layer of the cable. The layer material burns and catches fire.

2. Long-term overload operation of the cable

Long-term overload operation, the working temperature of the cable insulation material exceeds the higher allowable temperature of normal heating, thereby accelerating the insulation aging of the cable. This insulation aging phenomenon usually occurs in the entire cable line. Due to the aging of the cable insulation layer, the insulation material will lose or reduce the insulation layer and mechanical properties, so it is easy to break and catch fire, and even burn in many places along the entire length of the cable.

3. Insulation breakdown of the intermediate junction box

The intermediate joint of cable joint box is oxidized, heated and gummed during operation due to loose crimping, weak welding or improper joint material selection; When making the cable intermediate joint, the quality of insulating agent poured into the intermediate joint box does not meet the requirements. When pouring the insulating agent, there are air holes in the box and the cable box is poorly sealed and damaged, which causes moisture leakage. The above factors can cause insulation breakdown, form short circuit, and cause cable explosion and fire.

4.Cable head burning

Because the surface of the cable head is contaminated by moisture, the porcelain sleeve of the power cable head will break, and the distance between the wires will be too small, which will cause arcing and fire, which will cause the cable head and the surface of the cable to be insulated. The insulation of the outlet is burning.

5. Cable fire caused by external fire and heat source

For example, the spread of fire in the fuel system, the explosion of the fuel circuit breaker, the spontaneous combustion of pulverized coal in the boiler crushing system or coal conveying system, the baking of high-temperature steam pipes, the chemical corrosion of acid and alkali, welding sparks, etc. may cause the cable to catch fire.

How to distinguish the quality of aluminum alloy cables

Conductor, insulation and armored sheath are necessary for the composition of aluminum alloy cables. The quality of aluminum alloy cables mainly depends on the aluminum alloy conductor rods and cable insulation. Aluminum alloy cables have very good performance, corrosion resistance, and mechanical Performance, bending performance, flexibility, etc.
1. Aluminum alloy conductor rod
See if we can independently produce high-quality aluminum alloy conductor rods:
1. At present, there are not many manufacturers with independent aluminum alloy conductor production technology. They have aluminum alloy conductor rod production lines that can be continuously smelted, continuous casting, continuous casting and rolling. If they do not have independent aluminum alloy conductor rod production capacity, rely on Consignment processing, so-called secret smelting, or other aluminum alloy conductor rods purchased without a formal source not only cannot ensure the basic quality of aluminum alloy cables, but also cannot control the quality of the cables from the source.
2. In addition to the aluminum alloy conductor rod production line with smelting, continuous casting, continuous casting and rolling, it also depends on the size of the continuous casting billet section of its production line. The larger the section, the better the quality of the rolled aluminum alloy rod. Excellent, “good steel is made by hard work.” Excellent aluminum alloy conductor rods are the decisive factor for the electrical and mechanical properties of aluminum alloy cables. If you do not have high-quality aluminum alloy rods, no matter how drawing, stranding, cabling, armoring, etc., the subsequent processes cannot be changed The basic quality of its conductor.

2. Cable insulation
There are three things to look at with regard to insulation; cross-linking degree, stranded conductors, and conductor cable annealing:
1. Cross-linking degree: One of the advantages of aluminum alloy cables over copper cables is that all aluminum alloy cables are insulated with cross-linked polyethylene, and the operating temperature of the cable is 90 degrees. It is precisely because of the use of cross-linked polyethylene insulation that there is a problem of cross-linking degree. Regular professional aluminum alloy cable manufacturers should have a special cross-linking room.
2. Stranded conductor: Look at the conductor stranding technology and conductor stranding production line. At present, the stranded conductor equipment in the domestic cable industry is basically the same. The stranded conductor produced usually produces aluminum chips and burrs, which damage the insulation and affect the insulation. Effect, cause safety hazards and shorten insulation life. The advanced stranded conductor equipment is a sub-motor type, PLC program-controlled nano-technology conductor stranding equipment. Using this advanced process equipment, computer-controlled production programming, and innovative top-level nano-technology, the aluminum alloy conductors produced have no aluminum on the surface Chips, no burrs, no oil, no bumps, no scratches, no scratches, can effectively ensure that the cable insulation is free from any damage and destruction, and the service life of the product is much higher than that of similar products.
Third, the performance of aluminum alloy cables
1. Corrosion resistance: The corrosion resistance of pure aluminum is better than that of copper, but the corrosion resistance of aluminum alloy is better than that of pure aluminum, because the chemical elements such as rare earth added to aluminum alloy can increase the corrosion resistance of aluminum alloy, especially The performance of electrochemical corrosion resistance solves the long-term electrochemical corrosion problem of pure aluminum at the joint.
2. Mechanical properties: tensile strength and elongation. Compared with pure aluminum conductors, aluminum alloy conductors have added special ingredients and adopted special processing techniques to greatly improve the tensile strength, and the elongation rate is increased to 30%, making it safer and more reliable to use.
3. Bending performance: The bending performance of the aluminum core cable is very poor, and the bending is easy to break. The bending radius of the aluminum alloy power cable is 7 times the outer diameter of the cable, which is far better than the GB/T12706 “small bending when the cable is installed. 10 to 20 times the outer diameter of the cable specified in “Radius”.

4. Flexibility: As long as the pure aluminum cable is twisted at a certain angle for a few times, the conductor will crack or break, which is easy to cause accidents. The aluminum alloy power cable can withstand dozens of bends, eliminating the installation and use of pure aluminum cables in the past. The hidden dangers of accidents occurred during the process, which greatly improved the safety and reliability.
5. Aluminum alloy conductor is an emerging conductor material formed by adding rare earth, magnesium, copper, iron and other elements to pure aluminum through alloy technology. As we all know, after adding other alloying elements to aluminum, the electrical conductivity will decrease. However, through process control, the electrical conductivity can be restored to a level close to that of pure aluminum, making it have a current carrying capacity similar to that of pure aluminum.
6. Pure aluminum has poor creep resistance. The thermal expansion and contraction caused by power-on and power-off will cause a large amount of creep at the connection. After a long time, it will relax, and the contact resistance will increase and cause overheating, which is easy to cause accidents. The creep resistance of AA8000 series aluminum alloy is 300 of that of pure aluminum conductor, which greatly reduces the possibility of cable joint slack and improves the connection of conductors.

Is it better to use ordinary wires for household decoration or flame retardant wires?

Regarding this problem, it has always been a problem that owners have struggled with during decoration. Although each has its own advantages, it is recommended to use flame-retardant wires and higher safety performance when conditions permit.

The advantages of flame-retardant wires: in the event of a fire, the flame spread speed can be controlled within a certain range to avoid major disasters caused by the prolonged combustion of the wires, fight for rescue time, keep various equipment, and avoid greater losses.
Difference from ordinary wires: most ordinary insulated wires and flame-retardant wires have no difference in appearance, but flame-retardant wires contain flame-retardant components in the outer plastic insulation layer, while ordinary wires do not; flame-retardant wires are also classified as ZA ZA, ZB and ZC have three levels of flame retardant effects. ZA has a higher and better flame retardant rating. It is generally used in military, aviation and municipal engineering. The flame retardant effects of ZB and ZC can be used for ordinary household decoration.

Do I need to use flame-retardant wires for home decoration?
Homes have strict acceptance standards for engineering constructions, requiring that such places must use flame-retardant wires; at the same time, the fire department and engineering supervisors conduct spot checks on the construction wires, and the wires can only be constructed after they have passed the flame retardant performance. Therefore, in terms of home furnishings, flame-retardant wires can meet household electricity needs.

In the home decoration, the wires are concealed projects. Once damaged, it will be more troublesome to repair. Therefore, try to use wire and cable products with higher safety performance, and use it more safely.


The difference between fire-resistant cable and flame-retardant cable

Flame retardant wire and cable, its flame retardant means that when a wire and cable fire accident occurs, it can block and delay the spread and extension of the flame along the wire and cable, and minimize the expansion of the wire and cable fire range. This type of cable has a self-defense after fire. The characteristics of extinguishing. Generally, it can be understood that when the wire and cable product catches fire by itself or by an external heat source, after the fire source subsides, the wire and cable product no longer burns, or the burning time is very short.

Fire-resistant wire and cable means that in a wire and cable fire accident, the wire and cable product can maintain normal operation for a certain period of time while the external flame is still burning, maintain the integrity of the wire and cable circuit and maintain the normal operation of the line equipment.

Both fire-resistant cables and flame-retardant cables are suitable for wiring of control, signal, protection and measurement systems with a rated voltage of 750V and below.
The structure and materials of fire-resistant cables are different from those of flame-retardant cables. The basic structure of flame-retardant cables is:
(1) The insulating layer is made of flame-retardant materials.
(2) The sheath and outer sheath are made of flame-retardant materials.
(3) The wrapping tape and filling are made of flame-retardant materials.

Fire-resistant cables usually add a fire-resistant layer between the conductor and the insulating layer, so theoretically, a fire-resistant layer can be added to the structure of the flame-retardant cable to form a flame-retardant and fire-resistant cable. Because of the fire-resistant layer of fire-resistant cables, multi-layer mica tapes are usually used to wrap the wires directly. It can withstand long-term burning, even if the polymer at the place where the flame is applied is burned, it can ensure the normal operation of the line.

Commonly used aluminum alloy wire varieties and product advantages

The commonly used aluminum alloy wire varieties are as follows:
1. High-strength aluminum alloy wire
High-strength aluminum alloy wire is an aluminum alloy product with magnesium and silicon added to aluminum and processed to obtain sufficient strength, plasticity and electrical properties, deformation and heat treatment. It is the largest and most widely used aluminum alloy variety of aluminum alloy transmission lines. The electrical conductivity of high-strength aluminum alloy wire is 53% IACS, which is almost twice that of ordinary aluminum wire, and the single-wire strength of aluminum alloy is greater than 300Mpa. The strength of ordinary aluminum single wire is 150~170Mpa, and aluminum alloy wire has a greater advantage in strength.



2. Heat-resistant aluminum alloy wire
Heat-resistant aluminum alloys are classified into heat-resistant aluminum alloys with an electrical conductivity of 58% IACS and high-conductivity heat-resistant aluminum alloys in which yttrium is added to aluminum. Since the current carrying capacity of the wire used at 150°C can be increased by 61-69% than that of the wire used at 90°C, the heat-resistant aluminum alloy can be used as a compatible wire. The high-strength performance of high-strength heat-resistant aluminum alloy wire can improve its dynamic stability under short-circuit or overload conditions; its heat resistance can improve thermal stability. The super heat-resistant aluminum alloy and ultra-high heat-resistant aluminum alloy to be developed can further improve the current-carrying capacity and heat resistance of the wire, and further increase the long-term use temperature to 180°C, 210°C and 230°C.
Compared with traditional ACSR, high-strength aluminum alloy wire and heat-resistant low-resistance aluminum alloy wire have the following advantages:
(1) Under the same unit weight, the DC resistance of the aluminum alloy conductor is low. , The current capacity is large, the pulling force is large, the unit weight is larger than the pulling force;
(2) Compared with the condition of the same current-carrying capacity, aluminum alloy wire has the advantages of lighter weight, greater tensile force, and greater tensile force per weight. Aluminum alloy wire is a single material wire, easy to install and construct.
(3) The carrying hazard level of aluminum alloy conductors is low;
(4) The service life of ordinary steel core aluminum stranded wire is about 50 years, and the service life of aluminum alloy wire is more than 100 to 120 years.