Talking about the definition and function of weak current wires

1. Definition of weak current wires
Weak current cables refer to cables used for security communications, electrical equipment and related weak current transmission. There is no strict boundary between “wire” and “cable”. Generally, products with a small number of cores, small product diameters, and simple structures are called wires, those without insulation are called bare wires, and the others are called cables; those with a larger conductor cross-sectional area (greater than 6 square millimeters) are called large wires. Small (less than or equal to 6 square millimeters) are called small wires, andXLPE insulated cables are also called cloth wires.
RVS fire wire
2. The role of weak current wires
The main processing object of weak wires is information, that is, the transmission and control of information, which is characterized by low voltage, low current, low power, and high frequency. The main consideration is the effect of information transmission, such as the fidelity, speed, breadth and reliability of information transmission, that is, the line that realizes the transmission of weak electrical signals.

RVVP shielded wire
3. Types of weak current wires
1. Telephone line, large logarithmic HYA: wire specifications are 2*1, 2*0.5, 4*1, 4*0.5, large logarithmic HYA has 10 pairs, 20 pairs, 30 pairs, 50 pairs, 100 pairs And so on, are all in pairs.
2. Video cable SYV series and SYWV series: SYV is a video cable for monitoring, such as video cable SYV75-5; SYWV is a cable TV cable, which belongs to physical foaming; there is also an elevator frequency cable SYXV.
3. Power cord RVV series: mainly used for weak current power supply, sometimes also used for control, such as RVV2*1.0.
4. RVS, RVB, RVVB series, including common type, fire-resistant type, and flame-retardant type. RVS is generally used in fire fighting systems.
5. Network cable: UTP is unshielded, FTP is shielded, such as: Category 5 unshielded network cable UTPCAT.5e, Category 6 shielded network cable is FTPCAT.6e.
6. Shielded wire RVVP series: The appearance is similar to the RVV power cord, except that there is an extra layer of shielding net in the structure, and a letter P is added to the model. Generally, wires with P have a shielding layer.

What kind of cable is HFTGB?

HFTGB series of flexible synthetic mineral insulated fireproof cables are made of copper stranded wire as conductor, wrapped with mineral oxygen barrier, extruded with synthetic mineral insulating material, and then covered with synthetic mineral belt, and the outer layer is spirally wrapped with non-magnetic stainless steel belt. Where the metal sheath is specifically required to not be exposed, a low-smoke, halogen-free sheath can be added to the outside.
Basic product parameters:
Conductor: The conductor is a round copper stranded wire.
Insulation: mineral oxygen barrier, then extruded synthetic mineral insulating material
Filling layer: The synthetic mineral belt is covered with a mineral compound.
Sheath: Spiral wrapped with non-magnetic stainless steel belt.
Use: This product is the first in China, and there is no prototype in the world. Compared with the BTTZ series of metal outer sheathed cables, the product maintains ultra-high fire resistance and electrical resistance. It can achieve continuous large length and multi-core cable within 120 mm, which overcomes the shortcomings of too many joints, and stainless steel The mechanical properties and environmental corrosion resistance of the outer sheath are greatly improved.
Special cables
Features: Flexible synthetic mineral insulated fireproof cable adopts a flexible structure to make up for the defects of hard structure, flammability, and toxicity. It also has some advantages that other cables cannot have, such as: fire resistance, large current carrying capacity, and impact voltage resistance , Mechanical damage resistance, halogen-free, non-toxic, explosion-proof, waterproof, anti-rat bite, corrosion resistance, long life, safety, overload resistance, high temperature resistance, heat insulation and low comprehensive cost characteristics, flexible synthetic mineral insulated fireproof cable HFTGB( Y) The process structure of the product is exactly the same as that of the traditional cable. It successfully solves the many shortcomings of the product determined by the production process of the magnesium oxide mineral insulated cable (BTTZ). At the same time, the power and the communication fireproof cable are integrated, so that in the event of a fire Keep communication information unblocked.
product description:
HFTGB cable is the first in China, and there is no prototype in the world. Compared with the BTTZ series of metal outer sheathed cables, the product maintains ultra-high fire resistance and electrical resistance performance. It can achieve continuous large length and multi-core cable within 120mm2, which overcomes the shortcomings of too many joints, and The mechanical properties and environmental corrosion resistance of the stainless steel outer sheath are greatly improved. However, the structure of this product is also complicated, the conductive performance of the stainless steel outer sheath is weak, and it cannot replace the grounding wire like a copper sheath. The overall cost is relatively high among the major categories of mineral cables.

Product performance standards:
1. BS 6387:1994 performance requirements for cables to maintain circuit integrity under flame conditions;
2. Follow the corresponding corporate standards.
Product characteristics:
Voltage level: 0.6/1kV, working voltage is 500V for light load and 1000V for heavy load.
Working environment: The long-term working temperature is 70°C for the sheath; the long-term working temperature of the mineral insulated cable is 105°C where no one can touch it.
1. Installation conditions: It is suitable for the open laying of the ladder frame, and the installation methods such as bridge frame, pipe-through, and burying can also be adopted;
2. Installation process: there are special connectors, please refer to the manufacturer’s “installation instruction manual” for details;
3. Matters needing attention: The bending of the stainless steel metal sheath must be carried out in a reliable way. A single single-core cable is not suitable for laying directly through a metal pipe.

A qualified cable, these steps can not be less

A qualified cable, which can not be short of 600V Overhead Aerial cable 54.6m㎡ as a means of transmitting electrical energy and communication signals, is undoubtedly the existence of blood vessels and nerves in the modern era of the Internet, is the key to manufacturing in most industries today.

Chinese cable industry is now a large-scale, is a major international cable manufacturing country, the domestic cable manufacturing industry is only the second largest manufacturing industry after automobiles, but the huge industry has also spawned a lot of chaos and speculators, many small cable enterprises, in order to seize the market, maliciously underpricing, producing unqualified cable and wire without enough work and materials, and even worse, using fake cable and wire to list well-known cable and wire brands for sale, has had a very bad impact on the industry.

In the production of cable, in strict accordance with the production requirements and procedures, and conduct a comprehensive testing and testing to ensure that URD Cable out of the factory is of high quality, today to talk about the production of a qualified cable, what are the key steps? First of all, of course, it is strictly controlling the purchase of raw materials.

If it is a good raw material, then the quality and life performance of the cables produced will be greatly reduced. Meanwhile, Shenghua cable will strictly control the purchase, production, transportation, sales and other links, compare the raw materials from the suppliers in all aspects to ensure that the raw materials obtained are of high quality and durable; with good production materials, the next step is the production process. Huaxing cable has the latest cable production equipment.

During the production process, it also requires operators to work strictly in accordance with the requirements, whether it is extrusion machine series, drawstring machine series, stranding machine series, wrapping machine series, Huaxing cable are to achieve strict production requirements. Inspection is the most important link in the cable production process, Shenghua cable is of course also attached great importance to, for a long time, huaxing cable has always insisted on the survival of quality, to ensure safety, to service credibility, to management to promote efficiency, to forge ahead. Through the strict check and inspection of each link of the production cable, the product quality is ensured and the customer requirements are met.

Do you know what are the advantages of superconducting cables

At present, the long-distance large-capacity power transmission generally uses overhead bare aluminum cable and wires, and the power transmission in large cities generally uses underground cables, and the conductors are copper wires or aluminum wires. Using these traditional wires or cables, electrical energy will lose 5% to 10% during the transmission process. In order to reduce the loss of electric energy during the transmission process, the voltage should be increased as much as possible during long-distance transmission, such as using 500kV or 750kV and above ultra-high voltage lines. UHV lines have very high requirements on the insulating porcelain bottles of transmission towers and the use of space, especially the materials and production technology requirements of line terminal accessories, which greatly increase the construction cost of UHV lines. At present, my country cannot produce terminal accessories for ultra-high voltage lines, and imported ultra-high voltage line terminal accessories are very expensive.

If a superconducting cable is used, its AC impedance is only 1/10 of that of a conventional aerial bundled cable ASTM B231 standard, which can reduce the line loss of the power grid by about 50%; the application of superconducting cable will also reduce the system voltage for long-distance transmission, and the overall cost of other equipment in the system will follow It is reduced.In the long run, the application of superconducting cables also makes long-distance DC transmission technology easy and economical. For direct current transmission, superconducting cables will reduce the power grid line loss by more than 70%, showing better economic benefits. Since the power transmission capacity of superconducting cables is 3 to 5 times that of traditional conventional cables, the use of superconducting cables can also save the area and space of the power transmission system, save a lot of valuable land resources, and protect the ecological environment accordingly.

The smooth grid-connected operation of China’s first group of practical superconducting cables indicates that the technology of my country’s superconducting cables has become mature and has a profound impact on the development of my country’s power system. The application of superconducting cables in the main lines of my country’s power grids and transmission bottlenecks will help improve the safety and reliability of the power grid. In the long-distance and large-capacity transmission, superconducting cables have incomparable advantages in the overall performance of the system, and will fundamentally solve the problem of long-distance and large-capacity transmission such as my country’s “West-to-East Power Transmission” in the long run. In the near future, high-temperature superconducting cables may soon show advantages in the following aspects:

(1) In dense urban residential areas, skyscrapers, conventional cable capacity is insufficient, and there is no room for aerial bundled cables BS 7870;

(2) High current, short distance, and small space applications such as metal smelting equipment;

(3) High-current transmission bus in power stations and substations;

(4) In large cities with rapidly developing power demand, the required power supply capacity is constantly expanding. Due to the congestion of the city and the high cost of excavation, it is impossible to expand the scope of cable laying. With the help of superconducting cables, it can be replaced in the original pipeline to increase the power supply capacity. Increase 3-5 times.

Selection of power cables for home use

The decoration of the new house has many small and large details, and every detail needs to be taken seriously. This is because many decorative details are related to the comfort and safety of the house. However, there are many decorative materials on the market. Therefore, many friends do not know how to choose when choosing materials. Among them, everyone is more entangled. The question of material selection is: Should power cables be flexible wire? Or should I choose a hard line! What is the difference between hard wire and soft wire? Below, I will give you a brief explanation.
Before choosing hard wire or soft wire, we must first know what is hard wire? What kind of wire is a flexible wire?
The so-called flexible wire refers to strands of conductive solid wires with a diameter less than 1mm twisted together, that is, multiple strands of copper wires are twisted together. Therefore, the flexible cord is also called “sheathed cord”. Hard wire refers to a hard wire composed of several thick copper cores. Generally, hard wires of less than 10 square meters are single stranded.

So, what are the advantages and disadvantages of soft and hard wires? The details are as follows.
From the point of view of the service life of the wire, because the hard wire is thicker, it is not easy to oxidize; the flexible wire is composed of multiple thin copper wires, which are easily oxidized by the air, so the service life of the hard wire is much longer than that of the flexible wire From the perspective of the cost of the wire, since the flexible wire is relatively soft, it must be wound many times before use; the hard wire has only one copper wire, which can be passed directly. Therefore, compared with flexible wires, hard aaac conducors have less processing and are much cheaper; from the perspective of current-carrying capacity, flexible wires are composed of multiple strands of copper wire, and their current-carrying capacity is greater than that of a single copper wire. , But when it is suddenly loaded, the capacity of the current-carrying hard wire is greater than the capacity of the flexible wire; therefore, if it is used in general household appliances and the current does not exceed 100 A, single-stranded wire can be used.

2. From the perspective of the working process of the wire, use a soft wire at the connection of the hot tin or iron wire end, otherwise the multi-stranded wire may rise and connect with the next wire, which is very dangerous; and the hardness of the hard wire Very strong, its safety performance is relatively strong, from the perspective of whether it is convenient to repair the wire; although the hard wire is more difficult to replace, it can be completely pulled out of the threaded tube; if necessary, you can also replace the threading; but The cord is different, because the cord is prone to aging and breaks easily, so when the cord is replaced, the wire is likely to be damaged.
Generally, hard wires are more suitable for household use. However, it is worth noting that not all household wires need to use hard wires, and some places are more suitable for flexible wires. Therefore, when choosing wires, you should choose according to the location of the wires and the needs of your own home.

Graphene: Let AAAC cables also “voice control”

The new material we are going to talk about this time may bring new changes to the material field of aluminum alloy cables. It is magic angle graphene. Some people say, isn’t it just graphene? I already knew it.
In fact, it is really not. The magic angle graphene we are going to talk about is not the graphene you understand. Different from graphene, magic angle graphene has a feature, that is, insulation and superconductivity will appear on the same material. We don’t know what this material can do in the field of cables, but it may open a sea of ​​unknowns to the cable industry.

Let’s get to know it now.
The “Magic Horn” is indeed like a magical angle. Graphene is originally a material with better conductivity than metal, but when two layers of graphene are stacked together, at a special angle, they suddenly become insulators.
According to our general understanding, insulators and superconductors are two extreme materials. The resistance of the insulator is very high, while the resistance of the superconductor is zero. However, when the two layers of graphene are at a special angle, they can easily bridge the gap between these two extremes. You can imagine that one day, the insulation of the cable you make is a conductor, and the conductor is also insulation, and you can change it at will. Anyone who makes materials knows that it takes time and effort to find new materials with certain characteristics. Because there is almost only one way to do this work, which is to keep sifting through a large number of materials. Whether you can find it is almost pure luck.
But the study of magic angle graphene has opened up new ideas for materials science. It makes scientists realize that materials science can accurately predict the performance of materials in advance and reduce a lot of work. Even materials science can construct new materials based on the underlying logic of material properties.

In early May 2020, Chinese young scientist Cao Yuan published two articles in the same issue of Nature, introducing some new discoveries of his team on “Magic Angle Graphene”.
To talk about this new hairstyle, we have to start with graphene. Graphene is a material with a thickness of only one carbon atom. More specifically, the carbon atoms will first form a hexagonal unit, and then spread out on the plane like a tile. If you compare it, it looks like a mosquito net. Common mosquito nets are covered with hexagonal holes, and each hole is like a unit of six carbon atoms in graphene.
If we randomly stack two layers of mosquito nets together, it is difficult to completely overlap the hexagonal holes, and there will always be a certain angle of misalignment. For graphene stacked in two layers, this angle will bring about a surprising change: at a special angle, graphene that has better conductivity than metal will suddenly become an insulator.
This special angle is the “magic angle”. When two or more layers of graphene are stacked at this angle, it is called “magic angle graphene.”
In fact, as early as 2011, some scientists discovered through theoretical predictions that when the angle between two layers of graphene is at a certain angle, the electrical properties of graphene will suddenly change. But at the time, there was only theory, no experiments.
In 2018, experiments appeared. The Pablo Jarillo-Herrero team of the Massachusetts Institute of Technology in the United States published a paper in the journal “Nature” and used experiments to prove that this prediction was valid. Chinese scientist Cao Yuan was the first author.
They twisted the stacked graphene at a very low temperature and found that when the angle between the two graphene layers is 1.08 degrees, there will be a sudden change in prediction, and the originally conductive graphene will suddenly become Insulator.
What is even more amazing is that as long as a small electric field is applied, the insulator will turn into a superconductor. This experimental result exceeds the original theoretical prediction.
In May 2020, Cao Yuan’s team made some new discoveries.
In one of his papers, it can be seen that on the original basis, they have studied three different angles of double-layer graphene, the three angles are 0.84 degrees, 1.09 degrees and 1.23 degrees.
After studying double-layer graphene stacked at these angles, Cao Yuan’s team came to an important conclusion. They revealed that magic-angle graphene is “tunable.” This is a proper term in a subject, but don’t worry, it’s not hard to understand.
For example, the voice-activated lights in the corridor will light up when there is a sound. But in the beginning, no one knew the connection between sound and light. Cao Yuan’s work in 2018 is like discovering a phenomenon, that is, shouting at the voice-activated light from a specific angle, and the voice-activated light can be switched between “on” and “off” freely.
Of course, there is no such phenomenon in real life, but it happens in the world of graphene, so it is very eye-catching.
In his work in 2020, Cao Yuan further discovered that the lighting is very sensitive to angle changes still near this angle. You still shout, but when you shook your head slightly to the left or right, the light can not only switch between “on” and “off,” it can also change into various colors. This is the so-called “tunability”.
Using this “tunability”, maybe one day our AAAC cables will become “voice-activated”.

Basic knowledge of high voltage cable

High voltage cable is a kind of power cable, which is used to transmit power cable between 10kV and 35kV (1kV = 1000V). It is mainly used in the main road of power transmission.

The main types of high voltage cables are YJV cable, VV cable, yjlv cable and VLV cable.

YJV cable full name: XLPE insulated PVC sheathed power cable (copper core)

Full name of VV cable PVC insulated PVC sheathed power cable (copper core)

Yjlv cable full name: XLPE insulated PVC sheathed aluminum core power cable

VLV cable is PVC insulated PVC sheathed aluminum core power cable

Due to the excellent conductivity of copper conductor, more and more projects use copper core power cable as the main road of power supply system, while the application of aluminum core power cable is less, especially in the higher voltage power system, the more copper core cable is selected.

Structure of high voltage cable

The components of high voltage cable from inside to outside include: conductor, insulation, inner protective layer, filler (armor) and outer insulation. Of course, the armored high-voltage cable is mainly used for ground burial, which can resist the high-strength compression on the ground and prevent other external force damage.

Na-yjv, nb-yjv, XLPE insulated PVC sheathed class A (b) fire-resistant power cables can be laid in indoor, tunnel and pipeline with fire resistance requirements.

Na-yjv22, nb-yjv22, XLPE insulated steel strip armored PVC sheathed class A (b) fire-resistant power cables are suitable for buried laying when fire resistance is required, but not suitable for laying in pipelines.

Na-vv, nb-vv, PVC insulated and PVC sheathed class A (b) fire-resistant power cables can be laid in indoor, tunnel and pipeline with fire resistance requirements.

Na-vv22, nb-vv22, PVC insulated steel strip armored PVC sheathed class A (b) fire-resistant power cables are suitable for buried laying when fire resistance is required, but not suitable for laying in pipelines.

Wdna-yjy23, wdnb-yjy23, XLPE insulated steel strip armored polyolefin sheathed a (b) class halogen-free low smoke fire-resistant power cables are suitable for laying underground when there are requirements for halogen-free low smoke and fire resistance, but not suitable for laying in pipelines.

Za-yjv, za-yjlv, zb-yjv, zb-yjlv, zc-yjv, zc-yjlv, XLPE insulated PVC sheathed class A (B, c) flame-retardant power cables can be laid in indoor, tunnel and pipeline with flame retardant requirements.

Za-yjv22, za-yjlv22, zb-yjv22, zb-yjlv22, zc-yjv22, zc-yjlv22, XLPE insulated steel strip armored PVC sheathed class A (B, c) flame-retardant power cables are suitable for buried laying when flame retardant requirements are required, not suitable for laying in pipelines. Za-vv, za-vlv, zb-vv, zb-vlv, zc-vv, zc-vlv, PVC insulated and PVC sheathed class A (B, c) flame-retardant power cables can be laid in indoor, tunnel and pipeline with requirements for flame retardant.

Za-vv22, za-vlv22, zb-vv22, zb-vlv22, zc-vv22, zc-vlv22, PVC insulated steel strip armored PVC sheathed class A (B, c) flame retardant power cables are suitable for buried laying when flame retardant requirements are required, not suitable for laying in pipelines. Wdza-yjy, wdza-yjly, wdzb-yjy, wdzb-yjly, wdzc-yjy, wdzc-yjly, XLPE insulated polyolefin sheathed class A (B, c) flame-retardant power cables can be laid in indoor, tunnel and pipeline with flame retardant and halogen-free and low smoke requirements. WDZA-YJY23,WDZA-YJLY23,WDZB-YJY23,WDZB-YJLY23 ,WDZC-YJY23,WDZC-YJLY23,

Class A (B, c) flame retardant power cables with cross-linked polyethylene insulation and steel strip armored polyolefin sheath are suitable for buried laying when flame retardant and halogen-free low smoke are required, and are not suitable for laying in pipelines.

VV, VLV, copper (aluminum) core PVC insulated and PVC sheathed power cables are laid indoors, in tunnels and pipelines or in outdoor brackets without bearing pressure and external mechanical forces

Vy, Vly, copper (aluminum) core PVC insulated PE sheathed power cable

Vv22, vlv22, copper (aluminum) core PVC insulated steel strip armored PVC sheathed power cables are laid in indoor, tunnel, cable trench and directly buried soil. The cable can withstand pressure and other external forces

Vv23, vlv23, copper (aluminum) core PVC insulated steel strip armored polyethylene sheathed power cable

Service characteristics of high voltage cable

The product is suitable for power supply, transmission and distribution with AC rated voltage of 35kV and below, and can be used for fixed lines. The maximum long-term working temperature of cable conductor is 90 ℃, and the maximum temperature of cable conductor is not more than 250 ℃ in case of short circuit (the longest time is less than 5S).

UHV cable
1kV and below are low voltage cables; 1kV ~ 10kV are medium voltage cables; 10kV ~ 35kV are high voltage cables; 35 ~ 220kV are UHV cables;

UHV cable is a kind of power cable with the continuous development of cable technology. As the central link of large-scale transmission system, UHV cable is a kind of high-voltage cable with high technology content, which is mainly used for long-distance power transmission.

Raw Materials for Wire and Cable

There are thousands of wire and cable products, which are used in various industries. There are two general uses for them, one is to transmit current and the other is to transmit signals. The main technical performance index of the transmission current cable is the time-voltage performance of the conductor resistance; the main technical performance index of the transmission signal cable is the transmission performance-characteristic impedance, attenuation and crosstalk. Of course, the transmission signal mainly relies on electric current (electromagnetic wave) as the carrier. Now with the development of science and technology, light waves can be used as the carrier for transmission.

Main Materials of Wire and Cable:
1. The copper wire uses electrolytic copper as the raw material, and the copper wire made by the continuous casting and rolling process is called low-oxygen copper wire; the copper wire made by the up-drawing method is called oxygen-free copper wire. The oxygen content of the low-oxygen copper wire is 100-250ppm, the copper content is 99.9-9.95%, and the conductivity is 100-101%. The oxygen content of oxygen-free copper wire is 4–20p

pm, the copper content is 996-999%, and the conductivity is 102%. The specific gravity of copper is 889g/cm3.

2. The aluminum wire used as the wire must be annealed and softened. Aluminum wires used for cables generally do not need to be softened. The electrical resistivity of aluminum for wire and cable is required to reach 0.0282649mm2/m, and the specific gravity of aluminum is 2.703g/cm3.

3. Polyvinyl chloride (PVC): Polyvinyl chloride plastic is based on polyvinyl chloride resin and mixed with various compounding agents, such as antioxidants, antioxidants, fillers, brighteners, flame retardants, etc. The characteristics of PVC materials with a density of about 1.38~1.46g/m3: superior mechanical properties, chemical corrosion resistance, non-flammability, good weather resistance, good electrical insulation properties, and easy processing. The disadvantages of polyvinyl chloride materials: a large amount of toxic smoke is emitted during combustion; poor thermal aging performance, polyvinyl chloride has insulating materials and sheath materials.such as pvc insualted power cable. 

4. Polyethylene (PE): Polyethylene is polymerized by refined ethylene. According to the density, it can be divided into low density polyethylene (LDPE), medium density polyethylene (MDPE), and high density polyethylene (HDPE). The density of low-density polyethylene is generally 0.91-0.925g/m3; the density of medium-density polyethylene is generally 0.925-0.94g/cm3; the density of high-density polyethylene is generally 0.94~0.97g/cm3.PE cable become a good choice because it’s more economic.

The advantages of polyethylene materials: high insulation resistance and withstand voltage strength; in a wide frequency band, the dielectric constant and the dielectric loss tangent value are small; rich in flexibility, good wear resistance; heat aging performance, low temperature Good performance and chemical resistance; good water resistance and low moisture absorption; cables made with it are light in weight and easy to use and lay. Disadvantages of polyethylene materials: easy to burn when exposed to flame; low softening temperature.

5. Cross-linked polyethylene (XLPE): There are two main types of cross-linked polyethylene currently used in the cable industry. This is a kind of silane cross-linking agent called silane cross-linking material, which is mainly used in the insulation layer of low-voltage wires and cables. The other is a cross-linked polyethylene material with dicumyl peroxide (DCP) as a cross-linking agent, which is mainly composed of polyethylene, a cross-linking agent and an antioxidant. It is mainly used on the insulation layer of medium and high voltage cables. The higher the insulation withstand voltage level, the higher the purity required. The cross-linked polyethylene material used as a cross-linking agent is mainly composed of polyethylene, a cross-linking agent and an antioxidant. It is mainly used on the insulation layer of medium and high voltage cables. The higher the insulation withstand voltage level, the higher the purity required.such as 25-400m2 PVC XLPE insulated power cable .

DCP is a kind of peroxide, th

e higher the temperature, the faster the decomposition, after its decomposition, it will catalyze the cross-linking reaction of polyethylene. DCP will also decompose at room temperature, but the decomposition rate is very slow, but it will quickly decompose when heated to a certain temperature (the temperature exceeds 125°C). The silane crosslinking agent also has the same performance, but it also needs water as an auxiliary agent to achieve a complete grafting reaction. There are currently two types of silane cross-linked polyethylene in the market, one is called the one-step method, and the other is called the two-step method (this is different from the academic silane cross-linking method). The insulating material of the one-step method is premixed with the crosslinking agent and the catalyst. It is also called the copolymer method. The two-step method is divided into material A and material B. Mix the materials A and B before production. The storage time of the one-step method is very short, and the main material of the two-step method is separated from the catalyst material, so the storage time is longer, but the mixed material must be used immediately. In addition, carbon black masterbatch can also be added to the silane cross-linking material to play a role in weather resistance and used in the insulated overhead cable series. The advantages of cross-linked polyethylene materials: electrical properties are better than polyethylene and its mechanical properties are better than polyethylene, so it is more widely used than polyethylene. The softening temperature is higher than that of PⅤC, and the normal operating temperature of the cable can reach 90℃. The disadvantage is that it is difficult to process and easy to burn.
The advantages of cross-linked polyethylene materials: electrical properties are better than polyethylene; its mechanical properties are better than polyethylene, so it is more widely used than polyethylene. The softening temperature is higher than that of PⅤC, and the normal operating temperature of the cable can reach 90℃. The disadvantage is that it is difficult to process and easy to burn.

How to Prevent Wires and Cables from Catching Fire ?

How to prevent wires and cables from catching fire due to overload of wires?

During the operation of the wire and cable, it will generate heat due to the existence of resistance. The resistance of the wire is generally very small, and its heating power can be expressed by the formula q=I^2R. q=I^2R indicates: for a piece of wire in actual use (R is basically constant), the larger the current passing through the wire, the greater the heating power; if the current is constant, the heating power of the wire is also constant . The heat released during operation will be absorbed by the wire itself and cause the temperature of the wire to rise. Although the wire is constantly absorbing the heat released by current work, its temperature will not rise indefinitely.

Because the wire is constantly radiating heat to the outside while absorbing heat, the facts show that the temperature gradually rises after the wire is energized, and finally the temperature is constant at a certain point. At this constant point, the wire has the same heat absorption and heat dissipation power, and the wire is in a thermal equilibrium state. The ability of the wire to withstand higher temperature operation is limited, and operation exceeding a certain maximum temperature will be dangerous. This maximum temperature naturally corresponds to a certain maximum current, and running a wire that exceeds this maximum current is an overload. The overload of the wire directly causes the temperature of the wire itself and nearby objects to increase. Temperature rise is the most direct cause of this type of fire.

Overload damages the insulation layer between the twin wires and causes a short circuit, which burns down the equipment and causes a fire. The double-stranded wires are separated by the insulating layer between them, and the overload will soften and destroy the insulating layer, which will cause the two-stranded wires to directly contact and cause a short circuit and burn the equipment. At the same time, the high temperature generated by the large current at the moment of short-circuit causes the line to catch fire and fuse, and the resulting molten beads fall to combustible materials to cause a fire. Overload temperature rise can also directly ignite nearby combustibles. The heat transfer of the overloaded wire increases the temperature of nearby combustibles. For nearby combustibles with low ignition point, it is possible to ignite them and cause a fire. This danger is particularly prominent in warehouses for storing flammable materials and buildings that are easy to use and combustible decorations.

Overload also causes the connections in the circuit to be overheated, which accelerates the oxidation process. Oxidation produces a thin layer of oxide film that is not easy to conduct electricity at the connection points. The oxide film increases the resistance between the contact points, resulting in ignition and other phenomena, causing a fire.
So, how to prevent fire due to wire and cable overload?

1. During the circuit design process, the capacity of the site should be accurately verified, and the possibility of adding capacity in the future should be fully considered, and the appropriate type of conductor should be selected. For large capacity, thicker wires should be selected. Circuit design and reasonable selection are key steps to prevent overload. If the design is not properly selected, it will leave inherent hidden dangers that are difficult to rectify. Some small projects and places are not carefully designed and selected. It is very dangerous to choose and lay lines at will. New electrical appliances and electrical equipment should fully consider the capacity of the original lines. If the original line does not meet the requirements, it should be redesigned and modified.

2. The line should be constructed and laid by qualified electricians in accordance with relevant specifications. The wiring conditions directly affect the heat dissipation of the wires. Generally speaking, the wiring should not pass through flammable and combustible materials and stacks, which will cause poor heat dissipation of the wires, heat accumulation, and the possibility of igniting the surrounding combustible materials, which increases the risk of fire under overload conditions; Lines laid in the decoration ceiling of public entertainment places should be protected by steel pipes to separate the ceiling from the lines. Even if there are molten beads in overload, short circuit, etc., they will not fall to avoid fire.


3. Strengthen power management, avoid random wiring and wiring, and use mobile sockets with caution. Random wiring, random wiring, and use of mobile sockets are actually adding electrical equipment to a certain section of the line, which increases the amount of current and may cause overload. There are obviously more mobile socket jacks than fixed wall sockets. If too many electrical equipment are used on the mobile sockets, the original wiring must be unbearable. For larger power equipment and electrical appliances, separate lines should be provided, and mobile sockets should not be used as wiring sources.

4. Speed ​​up the renewal and transformation of old lines to eliminate fire hazards. Old enterprises, old residential areas and other units have been used for a long time, and many lines have been aging and have exceeded the service life. Even if the current-carrying capacity of some lines is not large, the aging circuit can hardly bear such current-carrying capacity, and it also has the danger of overload. Especially in old residential areas, the lines have long been aging, but with the improvement of people’s living standards and the increase of household appliances, their electricity consumption is still rising year by year, which is really worse. For old lines, timely supervision and coordination should be carried out, and rectification should be promoted as soon as possible to eliminate fire hazards and ensure safety.