The difference between pvc and pur cables

Although both PVC and PUR are classified as plastics, due to the different molecular formulas, the two chemical substances have significantly different properties. In contrast, PUR cables have excellent acid and alkali resistance, good resistance, abrasion resistance, low temperature resistance (low temperature resistance), moisture resistance, aging resistance, corrosion resistance, weather resistance, long application life, and UV resistance. Kinetic energy release and many other good effects, suitable for oil stains, extreme places of ultra-low temperature natural environment culmination.
PVC sheathed 10 million times extremely flexible and fast towline cable. Highly flexible PVC sheathed towline cable used in the cable towline management system. Special high-softness PVC is used as the outer sheath. Its function: and acid resistance Alkali and freezing liquid can be used in humid natural environment, but not suitable for outdoor use. Especially messed up and the material of PVC is that the cable has a long service life.
Modified material pvc raw material towline cable
PUR sheathed 10 million times extremely flexible and fast towline cable. Highly flexible PUR sheathed towline cable used in the cable towline management system. The PUR outer sheath is used. The key function: it adopts resilience and is very resistant to abrasion. Very good wear resistance, hydrolysis resistance, acid resistance, can be used in humid natural environments, because it has good weather resistance, it can be suitable for indoor and outdoor applications.

 


The quality of PVC cable material is basically determined by the secret recipe of PVC cable material and the material selected. Especially at the environmental protection cable material level and the environmental protection cable material level with special requirements.
Polyurethane material (PUR) is a kind of high polymer with urethane open chain repeating structural unit made by the reaction of acrylate and polyether polyol. PUR products are divided into polyurethane foam products and non-polyurethane foam products. Polyurethane foam products include soft plastic, rigid, and semi-rigid PUR plastic foam; non-polyurethane foam products include architectural coatings, adhesives, and synthetic leather. , Elastomer materials and collagen fibers. PUR raw materials have excellent functions, are widely used, and have many types of products. Cables made of PUR raw materials are called PUR cables.
Compared with PVC cables, PUR cables have excellent acid and alkali resistance, good resistance, abrasion resistance, low temperature resistance (low temperature resistance), moisture resistance, aging resistance, corrosion resistance, weather resistance, long application life, and Ultraviolet light and its kinetic energy release and many other good effects, suitable for oil stains, extreme places of ultra-low temperature natural environment culmination. Natural PUR raw materials are relatively higher than PVC materials, and the cost is much higher, at least 40% higher.
Although both PVC and PUR belong to plastics, due to the different molecular formulas, the two chemical substances have significantly different properties. In contrast, PUR cables have excellent wear resistance, good resistance, abrasion resistance, low temperature resistance (low temperature resistance), moisture resistance, aging resistance, corrosion resistance, weather resistance, long application life, and UV resistance. The kinetic energy is released and has many good effects, suitable for oil stains and extreme places where the ultra-low temperature natural environment is extreme.
In price comparison, the price of pur raw materials is twice as high as that of pvc raw materials. If it is a towline cable without special regulations, it is suggested to use modified material pvc raw materials to save a lot of costs.

Take you to understand mining cables and insulated environmental protection cables

Mining cable is the abbreviation of coal mine cable, which is a rubber sheathed cable for coal mine manufactured through national standards. Mining cables are suitable for mobile laying cables for mining power plants with power frequency rated voltage U0/U 8.7/10KV and below.
In the mine power supply system, high-voltage power supply lines generally use armored cables, and their failure rate is much less than that of low-voltage power supply.
The power supply in the mining area is a weak link in the power supply system, and the working environment is poor. Therefore, how to choose the type and section of the cable is related to the safety of the power supply operation.


The choice of cable type has a great relationship with the reliability, safety and economical reasons of the power supply. Article 467 of the Coal Mine Safety Regulations stipulates the following selection requirements for the selection of cables:
1. The level difference of the actual cable laying location should be compatible with the specified allowable cable laying level difference.
2. The cable should have a conductor with sufficient cross-section for protective grounding.
3. It is strictly forbidden to use aluminum-clad cables.
4. The fire -retardant cable that has passed the inspection and obtained the safety mark of coal mine products must be selected.
5. The cross-section of the main core of the cable should meet the load requirements of the power supply line.
Insulated environmental protection cables generally refer to wires and cables that have been tested by a regular testing organization, do not contain heavy metals and brominated flame retardants, do not produce harmful substances, and do not pollute the soil.
Insulated environmentally friendly cables can be recycled and will not harm the environment when discarded, and will not cause the spread of carcinogens. With the development of world economy and technology, the demand for cables is increasing, and their performance requirements are increasing. Under the new economic development trend and technical conditions, the development of the world’s cable industry has shown new trends, and insulated and environmentally friendly cables have gradually become the development focus of cables all over the world.

How to test and evaluate the quality of electric wires

For fire protection, maintenance and safety, it’s best to choose a wire specification for home improvement that has a certificate, a production license number, and a brand logo, and you must pay attention to its quality when purchasing overhead cables during home decoration. As long as there is nothing wrong with it, it is OK, otherwise the quality of the wires will not only affect our normal life, but there may also be huge safety hazards.
1. Appearance
Smooth and round, uniform color, insulating rubber and copper core are tight and not easy to peel off, inferior rubber looks thick, but when pressed hard, the squeezed part will become white, and it will be easy to age and fall off in the future, causing electric leakage.
2. Eccentricity
The thickness of the rubber ring is the same, that is, if the copper core is in the middle of the wire, the eccentricity is low.
3. Flame retardant
Use a lighter to burn the rubber. When the lighter leaves the wire, the wire should be automatically extinguished and a small amount of white smoke will be released. If the flame spreads and a large amount of white smoke is released, the rubber quality is not good.


4. Copper core
The high-purity copper core is anti-aging, high conductivity, and the fake color is yellow or white, and contains impurities. You can rub a piece of white paper on the copper core. If there are black substances on the white paper, it means that there are more impurities in the copper core. .
5. Logo
Whether there is a complete certificate of conformity, “CCC” mark, rated voltage, length, date, factory name and address and other complete information.
6. Thickness
The size of inferior copper core is often smaller than the size of a regular factory, and the outer insulation is thick, and the error of the wire section diameter cannot exceed 0.02%.
7. Length
The length of the ABC cable product conforms to the national standard 100±0.5m (that is, the standard is 100 meters, and the allowable error is 0.5 meters).
8. Weight
For the whole wire (100 meters), 1.5 square meters shall not be less than 1871 grams, 2.5 square meters shall not be less than 2915 grams, 4 square meters shall not be less than 4312 grams, and 6 square millimeters shall not be less than 6107 grams.

Fire-retardant and fire-retardant design of subway wires and cables

According to statistics from relevant departments, among the subway fires that occurred, fires caused by electricity accounted for more than half. However, in electrical fires, because there are relatively more wires and cables in subway buildings, and the underground environment is relatively humid, the commercialization of overhead cables, as well as aging and wire overload, etc., cause fires to be relatively large. Proportional. To a certain extent, the toxic gas emitted by the combustible insulation of wires and cables and the burning of protective materials will directly cause casualties, and will also restrict firefighting. Therefore, for these problems, it is necessary to use flame-retardant and fire-resistant wires and cables in the subway construction process, which can prevent electrical fires from occurring.
Subway cable laying

solar-cable-dual-core

At present, the most commonly used in subway station construction is ordinary flame-retardant fire-retardant wires and cables, which are relatively simple in production and relatively low-cost. Under the conditions of laying, the cable is burned to control the flame spread in the corresponding range. In this way, it prevents the disaster caused by the fire of the wire and cable and improves the fire protection level of the cable. The flame retardants in electrical fires mainly include aluminum hydroxide, chlorinated paraffin, dioxin and phosphoric acid wax and so on. However, the materials of ordinary flame-retardant cables are cross-linked polyethylene, oil hemp and ethylene-propylene rubber, etc. These materials are relatively easy to burn, except for polyvinyl chloride. When a fire occurs in a subway station, the combustion will release a large amount of toxic gases such as hydrogen chloride, and the damage caused is greater than the harm of the fire itself. Therefore, the application of flame-retardant cable materials can prevent corrosive gases from appearing in the cable during combustion, and only produce a small amount of dense smoke, which also reduces the damage to the equipment and the human body, which is conducive to the follow-up rescue work after the fire. The cost of the insulating layer and protective material of the low-smoke flame-retardant cable is based on polyvinyl chloride resin, and then plasticizers and absorbents, high-efficiency flame retardants and marital inhibitors are added to it, and then passed It is produced by a special process. This material can greatly reduce the release of dense smoke and toxic gases produced by the burning of the material, thereby ensuring the safety of the victims and equipment under the subway. So as to reduce economic losses.

Soaring! Today’s copper price rises for 3 consecutive years! Up to 80000!

Today’s copper price

CCMN spot copper price: 77050 yuan / ton, up 2770 yuan / ton

                                 

Chile bill affects supply, copper may rise sharply on the 10th

Abstract: the prospect of economic restart in Europe and the United States is optimistic. Copper revenue rose nearly 3% every other week, reaching a record high. Chile’s tax increase bill will affect copper output, and renewable energy will promote consumption growth. Today, copper is expected to rise sharply.Huaxing ACSR Cable.
[copper futures market] with the acceleration of vaccine promotion, the prospects of economic restart in Europe and the United States are more optimistic. Every other week, Luntong continued to be strong and set a new record high. The latest closing price was $10413 / T, up 297 or 2.94%. The trading volume was 23447, up 9877, and the position was 328659, up 1073. On Friday night, Shanghai copper jumped to open high, and the latest closing price of the main monthly 2106 contract was 75720 yuan / ton, up 1570 yuan, or 2.12%.
London Metal Exchange (LME) reported its latest inventory of 126725 tons on May 7, a decrease of 4025 tons or 3.08% compared with the previous trading day.
Copper stocks in the previous period increased by 8603 tons to 208473 tons last week, after a slight decline for two consecutive weeks. Chile’s lower house of Parliament has passed a bill that includes a floating tax on copper sales based on copper price fluctuations. Industry analysts believe that the bill will at least delay Chile’s new copper production capacity projects. The CEO of Glencore believes that the copper price needs to grow to 15000 yuan to promote new supply, and the development of renewable energy will promote consumption growth for a long time. Today’s spot copper price is expected to rise sharply.

Working principle and characteristics of radiation cross-linked wire and cable

1. Explanation of the principle of irradiation:
Irradiation cross-linking is to use the high-energy electron beam generated by the electron accelerator to bombard the insulating layer and the sheath to break the polymer chain, and each broken point becomes a free radical. Free radicals are unstable and must be recombined with each other. After recombination, the original chain molecular structure becomes a three-dimensional network molecular structure to form crosslinks.
Second, the characteristics of radiation cross-linked low-smoke halogen-free wire and aaac cable
1. Large current carrying capacity; after radiation cross-linked cable, after high-energy electron beam irradiation, the molecular structure of the material changes from linear to three-dimensional network molecular structure, and the temperature resistance level is increased from non-crosslinked 70℃ to 90℃, 105 ℃, 125℃, 135℃, or even 150℃, the current carrying capacity of cables of the same specification is increased by 15-50%.
2. The insulation resistance is large; because the radiation cross-linked cable avoids the use of hydroxide as a flame retardant, it prevents pre-cross-linking during cross-linking and the insulation resistance drop due to the absorption of moisture in the air by the insulating layer. Thereby ensuring the insulation resistance value.


3. Long service life and strong overload capacity; due to the high temperature resistance grade and high aging temperature of the radiation crosslinked polyolefin material, the service life of the cable during the cycle of heating is extended.
4. Environmental protection and safety; since the materials used in the abc cables are all halogen-free environmentally friendly materials, the combustion characteristics of the cables meet environmental protection requirements.


5. Product quality temperature: The quality of traditional warm water cross-linked cables is affected by water temperature, preparation process, cross-linking additives and other factors, and the quality is unstable. The quality of irradiated cross-linked cables depends on the radiation dose of the electron beam. The radiation dose is controlled by a computer, and there are no human factors, so the quality is stable.
Irradiation cross-linked low-smoke halogen-free flame-retardant wires and cables are difficult to catch fire and have the ability to prevent or delay the spread of flames. They have strong overload capacity and once caught fire, they have halogen-free, low-smoke, non-toxic, and non-corrosive characteristics. Used in high-rise buildings, hotels, hospitals, subways, nuclear power plants, tunnels, power plants, ore, petroleum, chemical industries, etc.

Cable quality defects and troubleshooting methods

The degree of crosslinking (hot extension) is unqualified
If the degree of cross-linking fails to meet the standard, the thermal-mechanical properties of the aac cable are unqualified and cannot meet the requirement of 90°C working temperature.
The reasons for the unqualified cross-linking degree are the unqualified formula and the improper type and ratio of the compounding agent. The formula should be adjusted to solve the problem; the second is the improper vulcanization process, such as low air pressure, fast line speed, high cooling water level and other factors.
The solution is to first find out what is the reason, which may be one or several reasons at the same time, and eliminate the reasons.


Unqualified structure and appearance
(1) The thinnest point of the insulating layer thickness is lower than the minimum value specified in the standard, or the average thickness is lower than the nominal value. The reasons for the unqualified insulation thickness are the fast line speed, the small amount of glue from the extruder, and the improper selection of molds.
The solution is to reduce the linear speed or increase the speed of the extruder and adjust the size of the die.
(2) Eccentricity
The reason for the eccentricity is that the mold is not adjusted or the suspension control has changed after the recruitment is adjusted.
The solution is to control the drape as stable as possible during driving.
Bamboo-shaped
The reason for the appearance of the bamboo-shaped outside of the cable is electrical and mechanical systems that cause the traction speed to be unstable. The second is that the core is too small, or the outer diameter of the acsr conductor full form is uneven.
The troubleshooting method is to check the mechanical and electrical system and eliminate the fault. Properly adjust the size of the core, control the outer diameter of the suburbs and counties to be as uniform as possible, and the stranded wire that exceeds the process regulations can be used.


Scratches on the surface
(1) The cable touches the upper or lower wall or foreign matter in the vulcanizing tube. Therefore, it is required to adjust the degree of suspension, try to make the wire core move in the middle of the cross-linked tube, and find foreign matter, and clean it in time.
(2) There is burnt on the outer edge of the mold sleeve. The solution is to adjust the temperature of the mold sleeve when starting the car to prevent overheating. Once it is found to be burnt, it should be stopped immediately to remove it, or it will not get better by itself.
Impurity
Most of the impurities in insulating materials and semi-insulating materials are brought in during mixing and during the feeding process of the extruder. Strict attention should be paid to the cleanliness of materials during operation to prevent the mixing of external impurities. Another kind of impurity is scorching lumps, its existence affects the performance and service life of the abc cable, so the temperature is strictly controlled during mixing and extrusion to prevent the occurrence of scorching.


bubble
There may be two reasons for bubbles generated in insulation, one is caused during extrusion. The solution is to select appropriate molds. There are bubbles in the shielding layer. The main reason is that there is moisture in the material. It should be dried before extrusion. The second is insufficient cooling. At this time, the following will appear. A circle of bubbles will appear on the circumference equidistant from the core.
The elimination method is to strengthen the cooling, raise the water level and lower the temperature of the cooling water.
Unqualified cable performance
(1) Unqualified free discharge and dielectric loss
The causes of dissociation discharge and dielectric loss unqualified are very complicated, and they are shielded from the outside. Whether the insulation contains bubbles and impurities is closely related to the performance of the raw materials. The elimination method is to keep the raw materials clean and strictly follow the production process.
(2) Cable insulation breakdown
The main cause of cable insulation breakdown is the mixing of insulating materials and external damage. Due to strict avoidance of external damage, the mixing of impurities should be avoided as much as possible. The semi-finished products are strictly managed to prevent stumbling.
(3) Cushion breakdown
The main reason for the cushion layer breakdown is the steel with burrs, curling, and puncture the cushion. The method of elimination is the use of different quality requirements of the steel belt. The cushion shall be made of plastic tape with a higher hardness, and it shall be ensured The thickness of the cushion.

The basic process flow of plastic wire and cable manufacturing

1. Copper and aluminum monofilament drawing
Commonly used copper and aluminum rods for wires and cables, at room temperature, use a wire drawing machine to pass through one or several stretch die holes to reduce the cross-section, increase the length, and increase the strength. Wire drawing is the first process of various wire and abc cable companies, and the main process parameter of wire drawing is die matching technology.
2. Monofilament annealing
Copper and aluminum monofilaments are heated to a certain temperature to recrystallize the toughness of the monofilament and reduce the strength of the monofilament to meet the requirements of the wire and cable for the conductive core. The key to the annealing process is to prevent the oxidation of the copper wire.


3. Stranding of conductors
In order to improve the flexibility of the wire and cable and facilitate the laying and installation, the conductive core is made of multiple monofilaments twisted. From the stranding form of the conductive core, it can be divided into regular stranding and irregular stranding. Irregular stranding is divided into bundle stranding, concentric twisting, special stranding and so on. In order to reduce the occupied area of ​​the wire and reduce the geometric size of the cable, the compacted form is adopted while the acsr conductor size is twisted, so that the ordinary circle is transformed into a semicircle, sector shape, tile shape and compacted circle. This kind of conductor is mainly used in power cables.


4. Insulated extrusion plastic wires and cables mainly use extruded solid insulation layer, the main technical requirements of plastic insulation extrusion:
4.1. Eccentricity: The deviation value of the extruded insulation thickness is an important indicator of the level of the extrusion process. Most of the product structure dimensions and deviation values ​​are clearly specified in the standard.
4.2. Smoothness: The surface of the extruded insulating layer must be smooth, and there must be no poor quality problems such as surface roughness, burnt, and impurities
4.3. Density: The cross-section of the extruded insulation layer should be dense and strong, and no pinholes visible to the naked eye are allowed to prevent the existence of air bubbles.
5. Cable
For multi-core cables, in order to ensure the degree of forming and reduce the appearance of the cable, it is generally necessary to twist them into a circle. The stranding mechanism is similar to that of conductor stranding. Because the stranding pitch diameter is larger, most of them adopt the non-back-twisting method. Technical requirements for cable formation: First, to prevent twisting of the cable caused by the overturning of the special-shaped insulated core; second, to prevent the insulation layer from being scratched. Most of the cables are completed with the completion of the other two processes at the same time: one is filling to ensure the roundness and stability of the cable after the cable is formed; the other is binding to ensure that the cable core is not loose.


6. Inner sheath
In order to protect the insulated core from being damaged by the armor, it is necessary to properly protect the insulating layer. The inner protective layer is divided into: extruded inner protective layer (isolation sleeve) and wrapped inner protective layer (cushion layer). The wrapping cushion layer replaces the lashing tape and the cable forming process is carried out simultaneously.
7. Armoured
For cables laid underground, they may be subjected to certain positive pressure during work, and an inner steel tape armored structure can be selected. Cable laying in occasions with both positive pressure and tension (such as in water, vertical shafts or soil with a large drop), the structure type with inner steel wire armor should be selected.
8. Outer sheath
The outer sheath is the structural part that protects the insulating layer of the wire and cable from environmental factors. The main function of the outer sheath is to improve the mechanical strength of the wire and cable, prevent chemical corrosion, moisture, waterproof, and prevent the cable from burning. According to the different requirements of the cable, the plastic sheath is directly extruded by the extruder.

Advantages of copper-clad aluminum power cable

1.DC resistivity. The resistivity of copper clad aluminum wire is larger than that of pure copper wire, about 1.5 times that of pure copper wire. When the cathode value is the same, the weight of copper clad aluminum wire is about 1/2 of that of pure copper wire. According to the calculation of the skin effect, when the high frequency is above 5MHz, compared with the acsr conductor of the same cross section, its resistivity is the same. In the use of power cables with a frequency of 50 Hz, the skin effect and proximity effect of copper conductors gradually become prominent above 150mm2. At the same time, due to the continuous development of science and technology, high-order harmonic currents and energy will be injected into the power supply system. , The high-order harmonic voltage of the corresponding frequency is generated on the impedance of the system, causing the voltage waveform to be distorted, increasing the loss of the power supply system, and increasing the heat of the conductor; in addition, the cable amplifies the harmonics and generates overvoltage at the joint. Damage to the cable head. The use of copper-clad aluminum conductors can reduce the AC impedance (resistance) generated by high-order harmonics. In other applications, by increasing the volume of copper in the copper-clad aluminum monofilament and corresponding technological measures, the copper-clad aluminum/copper composite conductor is within the upper limit of the outer diameter of the existing conductor of the same specification and meets the conductor’s DC resistance requirement.
Connection method. The use of copper-clad abc conductors can meet the habit of product selection, design, use, installation, etc. of wires and cables that will be continued for many years, and it is also beneficial to the pressing and tin welding of the cable terminals.

2.Reduce AC resistance. AC resistance is the main basis for the current carrying capacity. According to the principle of skin effect, the current per unit area on the surface of a single wire is larger than the current per unit area of ​​the center of the wire, that is, the center of a large cross-section conductor In the area of ​​a circle formed by the same conductor, the current passing through the center of the circle is smaller than that of the circle. Therefore, it is the most reasonable and economical to use different metals for the center conductor and the circumferential conductor. In addition to the DC resistance and the skin effect, the AC resistance index also has the proximity effect. Compared with the copper conductor with the same DC resistance, after the copper composite conductor is used, the aluminum is in the center of the aac conductor and the copper is on the outer edge; In the composite conductor, the inner layer is copper-clad aluminum and the outer layer is pure copper. Aluminum is not sensitive to the skin effect and proximity effect of copper. At the same time, the copper composite conductor will increase the total cross-section of the conductor by a part, so it also increases the conductor. The surface area of ​​the cable improves the heat dissipation conditions of the cable and increases the heat dissipation area. The thermal conductivity of aluminum is similar to that of copper. Under the same material cost condition, the AC resistance index is much more economical.

3.It has good corrosion resistance: aluminum is more corrosive than copper, but because the copper-clad aluminum material has been completely metallurgized, aluminum is completely covered by copper and will not be in contact with water or air. It can fully achieve the same performance as copper. Copper-clad aluminum/copper composite conductors are also more useful to prevent the cable from being corroded, bruised, or due to tight pressure, poor soldering, and poor contact between the conductor and the terminal, heating and causing the copper layer to fall off and copper and aluminum. A potential difference is formed between metals, which accelerates galvanic corrosion and causes the hidden danger of burning at the end of the cable. For aluminum conductors, especially in coastal areas, the chloride ions contained in the salt spray in the atmosphere will condense on the surface of aluminum, which will easily cause local corrosion around impurities and defects on the surface, forming holes, cracks and micro-batteries, and aggravate the damage of aluminum conductors. corrosion.
4.Low cost and light weight. Compared with the copper core cable with the same technical index, the copper clad aluminum conductor cable can save more than 40% of the cost, and the copper clad aluminum/copper composite conductor cable can save more than 20% of the cost. The proportion of copper clad aluminum wire is only 37%-40% of pure copper wire. When the wire diameter and weight are equal, its length is 2.5 times that of pure copper wire.
5.Good weldability. The copper-clad aluminum wire is concentrically coated with a layer of pure copper, so it has the same solderability as pure copper wire and is convenient for production.

Various types of cables

Because cables are used in many different environments, they look very different in appearance. But regardless of any cable type, they are used as a conductor for signal transmission. These acsr conductor size also have different quality performances in transmitting different signals. Except for some special applications, the cables currently used for audio and video transmission are mainly single wires, twisted pairs, coaxial wires and optical fibers.


1.1. Single wire
A single wire is the most basic type of cable (such as a wire). It consists of one or a group of wires surrounded by a plastic protective layer. This kind of cable is commonly used to transmit low-frequency signals, such as power, audio, and computer ID code.
1.2. Twisted pair
Twisted pair is a general term. There are no restrictions on the number of wires and the type of twisting, but there are only two types in the structure of the cable: twisted pair with shielded net (STP: ShieldedTwistedPair) and without shielded net Twisted pair (UTP: UunshieldedTwistedPair). Twisted-pair cables are commonly used in telecommunications, the Internet, and professional audio. This aaac conductor full form is composed of two or more independent and mutually insulated cables that are continuously twisted. Two of the cables that are twisted to each other are called a group. , The transmission impedance is generally 100_, and the diameter of a single wire is between 20AWG (American wireline standard: 0.91mm) and 24AWG (0.61mm). Twisted pair is a relatively inexpensive cable. Each set of wires has the same anti-interference ability, which can effectively suppress external electromagnetic interference (EMI) and effectively shield the transmission signal from electromagnetic interference to the outside world.
UTP cables are most commonly used in telecommunications transmission and computer network environments. According to the type of twisting, they are divided into five, super five and six types of cables. Generally, they can reach a transmission rate of 100Mbps (100 million bits per second). The STP cable adds a layer of woven metal mesh or tin foil to the periphery of the wire group, which is more conducive to improving the signal and suppressing the impact of external radio waves. The metal shell of each connector of the STP cable must maintain good contact with the shielding net.

1.3. Coaxial cable
Coaxial cable (Coaxial) is a composite composed of two conductors. The center wire of the coaxial cable is used to transmit signals. The metal shielding net plays two roles: one is to provide current for the signal as a common ground wire for the signal. The second is as a shielding net for the signal, which suppresses the interference of electromagnetic noise on the signal. The center wire and the shielding net are between the semi-foamed polypropylene insulation layer. The insulation layer determines the transmission characteristics of the aac cable and effectively protects the wires in the middle.
Coaxial cables are widely used in audio, video or radio frequency transmission, and the transmission impedance is generally 75_, which has become the standard impedance of video (in the early days, 50_ impedance characteristics were also used for video transmission). High-quality standard coaxial cables are generally more expensive than twisted pairs because of the reliable physical characteristics of coaxial cables, which can provide excellent audio and video performance. The frequency and resolution of the signal and the effective transmission distance of the cable play a decisive role in the audio and video system.


1.4. Optical fiber
Optical fiber cable (OpticCable) is the best choice for long-distance signal transmission. Optical fiber transmission is a technical method based on photoelectric conversion instead of electronic transmission. The simple principle of optical fiber transmission is: the analog electric signal is transmitted to the optical transmitter, and the input voltage signal is converted into a current signal through the signal buffer circuit and the driving circuit, and the light-emitting tube or laser is driven. In this way, the input electrical signal is converted into an optical signal, which is coupled into the optical fiber through precise optical alignment and guidance.
After the optical signal is transmitted through the optical fiber, at the receiving end the optical signal is converted into the original electron source by a wavelength-matched photodiode, and then output after being amplified by a low-noise linear amplifier.
Optical fiber signal transmission avoids many shortcomings of traditional cable transmission, and has many advantages that cable transmission can’t match; Excellent anti-electromagnetic interference: In long-distance cable transmission, the cable itself is a huge antenna, which picks up electromagnetic signals in the surrounding space. , Especially in the display system, this kind of interference signal shows the granular noise that cannot be eliminated in the image display. The core of the fiber optic cable is glass, and it transmits optical signals, which is not easily interfered by external electromagnetic waves.
Very small volume: Most optical fibers are as thick as human hair.
Very low attenuation: Because the optical fiber transmission is completed by the glass conduit, there is no signal attenuation caused by the cable resistance and capacitive reactance. The optical fiber greatly improves the transmission bandwidth and transmission distance. High security of optical fiber: The signal content transmitted by optical fiber is not easy to be eavesdropped on.
Although optical fiber seems to be the ultimate method of signal transmission, there are some disadvantages;
Higher prices: optical cables, transmitters, and receivers are expensive
High labor: In the process of arranging and routing optical cables, a lot of human resources and special tools are required. Although the transmission loss of the optical signal in the optical fiber is very low, the attenuation of the signal by the electro-optical and photoelectric conversion at the transmitting end and the receiving end is very severe. Therefore, to ensure no insertion loss transmission, it is necessary to add a high-gain multi-stage amplifier to the transmission, and to ensure that the circuit can work stably.