Cable structure

Production of cables without production license is punished

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From the first batch of “iron fist”, there are cables again and again. There’s nothing to say. We’re catching up with the “quality month”. Xiaobian reminds everyone to pay attention. There will be some later. Don’t forget what we said in the early stage. There will be a reward of 1 million for reporting, so someone must have moved this crooked idea in the near future.
On June 15, 2021, the market supervision bureau of Changchun City, Jilin Province imposed an administrative penalty of confiscating 1000 meters of AAAC Cable involved and imposing a fine of 110000 yuan on Jilin Xinda Cable Co., Ltd. for the illegal act of producing extruded insulated low-voltage power cable without obtaining a production license.


On March 18, 2021, the law enforcement officers of Changchun Market Supervision Bureau inspected the business premises of the parties according to the reporting clues, and found that the parties stored extruded insulated low-voltage power cables (model: wdzcyjlv4) on the site × 400+1 × 240； Voltage 0.6/1kv; Sectional area 400mm ²； Manufacturer: Jilin Xinda Cable Co., Ltd.) with a total of 1000m, and the cross-sectional area exceeds the “cross-sectional area ≤ 300mm” allowed by its production license ²” It is suspected to produce extruded insulated low-voltage ACAR Cables without obtaining production license.


After investigation, the extruded insulated low-voltage power cables of the above specifications and models produced by Jilin Xinda Cable Co., Ltd. belong to the products listed in the production license catalogue, and the party concerned has not obtained the production license of the products of the above specifications and models. After consulting the production accounts, sales accounts and sales invoices provided by the parties, the law enforcement officers found that the parties produced 1000 meters of the above illegal products according to the contract, with a price of 110 yuan / meter and a total value of 110000 yuan. Since the products have not been sold, there are no illegal gains. The act of the party concerned violated the provisions of Article 5 of the regulations of the people’s Republic of China on the administration of production licenses for industrial products, and Changchun Market Supervision Bureau imposed administrative penalties on the party concerned according to law.


Power cables are widely used in people’s production and life. The power cables used have quality problems, which may cause short circuit or aging and fire, and there are serious potential safety hazards. Therefore, the State implements production license management for power cables. Strictly investigating and punishing the production of power cables without production license according to law and further strengthening the supervision and management of ACSR Cable product quality are conducive to improving product quality level, clarifying product quality responsibility, protecting the legitimate rights and interests of consumers and maintaining social and economic order.

Matters needing attention during wire and cable stranding

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

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


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


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

Harm and Countermeasures of wire joint heating

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The phenomenon of wire joint heating is generally manifested in that there is peculiar smell around the wire joint, which can be smelled. This is because the heat of wire joint makes the outer insulation layer smell; Secondly, the ACSR Cables joint is smoking, red, the outer insulation layer is black, fire, or even broken. What are its hazards, causes and countermeasures?

1. Harm
Hot wire connection will not only cause a lot of power loss, but also seriously affect the normal operation of electrical equipment. At least, the working current in the line will increase and the service life of electrical equipment will be shortened. At worst, it will suddenly interrupt the ongoing production, scientific research, medical surgery and other activities, and lead to fire and electric shock accidents, resulting in incalculable losses.

2. Cause
(1) The connector is not tightened during equipment installation and repair. When the current passes through, it may generate heat, even redness, smoke, fire and disconnection. ABC Cables, switches and electrical appliances are connected through wire posts. Due to careless construction, no washer is added on the terminal post and the Gong cap is not tightened, which will also increase the contact resistance. For example, in a hotel, because of this reason, the conductor heated and melted, and the molten beads fell on the cardboard box below, causing a fire.
(2) The connector will also loosen after long-term operation. Some joints are of good quality during installation, but they will become loose due to thermal expansion and cold contraction or long-term vibration. For example, for copper aluminum joints in long-term operation, if there is no silver plating or tin hanging on the contact surface, the contact surface produces serious electrochemical corrosion and generates oxide film, which increases the resistance at the joint and is very easy to become a hot spot.

(3) For contacts with small current, the current increases suddenly due to the sudden change of the system, resulting in contact heating;
(4) In case of short circuit fault of the system, the over-current makes the contact with insufficient capacity or defective contact ignite instantly, etc.
Therefore, the contact heating is mainly caused by the increase of contact resistance.
3. Countermeasures
If the connector is well connected, the heating of the connector is prevented, and the heating problem of the AAAC Cable connector will not appear, so it does not need to be handled. Therefore, the wire joint shall be firm, tight and beautiful without overlap, bending, crack and concave convex; The mechanical strength of the joint shall not be less than 80% of the mechanical strength of the conductor; The insulation strength of the joint shall not be lower than that of the conductor. During installation and maintenance, the joints of wires shall be reduced as much as possible. Conductors with too many joints shall not be used. For joints of movable lines and outdoor lines, special attention shall be paid to the provision that only one joint is allowed between two adjacent wire stems.

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

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

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


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

Causes of blackening of copper wire of heavy rubber sheathed flexible cable

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2.1 catalytic aging of copper is an important reason for rubber hair adhesion
The experiment of the former Soviet Union Institute of AAAC Cable science proved that copper infiltrated into the insulating rubber from the contact with rubber during vulcanization, and the thickness of 1.0-2.0mm contained 0.009-0.0027% copper. As we all know, trace copper has a great damage to rubber, that is, heavy metal is the catalytic aging of rubber. During the process of insulation vulcanization, qiulanm precipitates some free sulfur to react with copper to form active copper containing groups: CH3 ■ ch2-ch-c-ch2- ■ ■ SS ■ ■ cucu, when aging, weak s-s-bond breaks, forming active copper containing base: cu-s-, which acts with rubber, and acts with oxygen, breaks down long bond molecules of rubber, making rubber soft and sticky, which is a combination of low molecular chain. The French Academy of rubber also pointed out that if there are harmful metals in rubber, such as copper, manganese and other heavy metal salts, the rubber viscosity will occur regardless of the type of promoter.

2.2 sulfur migration to the surface of insulating rubber and copper wire in rubber sheath cable
The possibility of sulfur diffusion in cable sheath rubber was confirmed by the use of radioisotope by former Soviet scientists. The diffusion coefficient of free sulfur is about 10-6cm2 / s at 130-150 ℃ in the vulcanized rubber based on natural rubber. In the continuous vulcanization factory, when vulcanizing sheath rubber, the temperature is between 185-200 ℃, and the diffusion coefficient is greater. Because of the diffusion of free sulfur in rubber sheath, the structure of the colum rubber is changed, and the polysulfide bond may be formed. These polysulfide compounds migrate through chemical decomposition and chemical combination, namely “chemical diffusion”. Due to the migration, not only the structure of the insulating rubber can be changed, the heat resistance of the rubber can be reduced, but the reaction between sulfur and copper surface will result in copper sulfide and cuprous sulfide, which leads to the blackening of copper wire. In turn, copper sulfide and cuprous sulfide accelerate the aging of rubber, and lead to the occurrence of adhesion.

3. Reasons for processing technology
3.1 reasons for processing rubber
In the insulation formula based on the combination of natural rubber and SBR, the plastic of rubber needs to be improved by plastic refining. In order to produce, some factories use internal mixer to improve plasticity by adding a small amount of chemical plasticizer, accelerator M. If the temperature of plastic refining and rubber filtration are not well controlled, high temperature above 140 ℃ appears. When the raw rubber is put on the opening mill, it passes through the drum slowly. Because the rubber is affected by hot oxygen and accelerator M, it will be found that the rubber surface seems to be coated with oil. In fact, rubber molecules are more serious in promoting the chain breaking under the promotion of chemical plasticizer, A relatively soft and sticky rubber with smaller molecular weight was produced.
Although the rubber was mixed with SBR and then mixed with insulating rubber, these small molecular weight natural rubber were evenly dispersed in the rubber. After the rubber was extruded on the copper wire for continuous vulcanization, there might be no problem at that time, but a hidden danger was buried for the rubber copper ABC Cables. That is, the local copper wire sticking phenomenon will appear in the first place for these small molecular weight natural rubber.

The process of adding vulcanizing agent and accelerator to insulating rubber is also very important. Some small factories add vulcanizing agent on the mixer, that is, pour the pot containing vulcanizate into the middle of the drum, with many in the middle, and less on both sides. When the vulcanizate into rubber, the number of turning triangle was less, which would make the vulcanizate distributed unevenly in the rubber. In this way, copper wire blackening is easy to appear in many places with vulcanizing agent when extrusion is continuous vulcanization. In the blackening place for a long time, the phenomenon of rubber adhesive copper wire will appear.
3.2 reasons for vulcanization of insulating rubber
In order to pursue the production, some enterprises only have 60 meters long continuous vulcanization tubes, 1.3mpa steam pressure, and the vulcanization speed is 120 m / min. thus, the residence time of insulating rubber in the pipe is only 30 seconds. Rubber itself is a bad conductor of heat. The surface temperature of the insulating core is more than 190 ℃, and when the temperature is transferred to the inner rubber contacting with copper wire, it is also absorbed by copper wire. When the copper wire is heated to close to the inner rubber temperature, the vulcanized rubber wire core has been discharged from the vulcanizing tube. So the temperature of the inner rubber is relatively low, about 170 ℃, and the vulcanization tube will be left only a few seconds. When it enters the cooling and winding, the insulation rubber will not be vulcanized enough.
In order to achieve sufficient vulcanization, the amount of promoter TMTD (as vulcanizing agent) is up to 3.4%. The excess of vulcanizing agent also releases more free sulfur during the curing process. Besides the crosslinking rubber molecules, there are also excess free sulfur. This is the reason why the copper wire surface is blackened.
In short, it is still difficult to solve the problem of copper wire blackening. Every process from copper wire to rubber should be taken seriously to achieve better results. The key to the problem is the choice of rubber species and the adoption of vulcanization system. The solution to this problem needs to go through the test of time.

How to measure the temperature of cable terminal tail contact?

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The contact resistance of the tail wire contact of AAAC Cable terminal (especially outdoor, sometimes connected by copper aluminum two different metals) will increase under the influence of long-term load and fault current, which will lead to overheating. When the line fails, the fault current flows through the contact, which will burn the contact. Measuring the contact temperature under the condition of no power failure, that is, to conduct live temperature measurement (preferably when the load is large), is an effective measure to monitor and check the contact condition. There are three main methods to check the contact temperature.


(1) Paste the temperature wax sheet: the temperature wax sheet is divided into three types: 60 ℃, 70 ℃ and 80 ℃, and are respectively expressed in different colors, and the commonly used ones are yellow, green and red. The temperature range can only be roughly checked by using the temperature wax plate. The reaction time is slow and the paste is not convenient. It is less used at present.
(2) Discoloration thermometer: this kind of color change thermometer is a surface measuring tool. It was used to monitor the temperature of heating working parts during welding in shipbuilding industry. It is used to indicate temperature according to the color changing characteristics of pigment in the pen at a certain temperature. The temperature measurement is quick and easy to use. Generally, the one with lower temperature can be selected for ABC Cable line. For example, the color changing temperature pen with color change temperature of 70 ℃ is selected, and it is marked as the original color. If the temperature is more than 70 ℃, it will become lake blue. The price of this color change thermometer is also cheaper. The temperature measurement reaction is fast (only 1-2s), and it is convenient to use.


(3) Infrared thermometer and thermal imager: the temperature wax plate and the color change thermometer shall be directly contacted with the live equipment, and the insulation rod shall be used for operation. Infrared thermometers and thermal imagers can measure temperature outside the measured point, so they are safe and reliable, and their measurement accuracy is much higher than the above two. The commonly used infrared thermometers or thermal imagers generally adopt portable type. See Fig. 9-4 and Fig. 9-5. The measuring distance is 5m, 10m, 100m, or even larger. The thermal imager can display the image of temperature distribution, and can store the image data in disk or computer, with good effect. But the price of this instrument is relatively expensive, and special personnel shall be responsible for the use and maintenance.

Differences in use of brass, phosphor copper and red copper

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Pure copper is a purplish red metal, commonly known as “red copper”, “red copper” or “red copper”. Pure copper is ductile. Pure copper, the size of a drop of ACSR Cable, can be drawn into two kilometers of filaments or rolled into almost transparent foil larger than a bed. The most valuable property of pure copper is its excellent conductivity, second only to silver in all metals, so it has become the “leading role” of the electrical industry.

Pure copper is more widely used than pure iron. Every year, 50% of copper is electrolyzed and purified into pure copper for electrical industry. The pure copper mentioned here is really very pure, with a copper content of more than 99.95%. A very small amount of impurities, especially phosphorus, arsenic, aluminum, will greatly reduce the conductivity of copper. The oxygen content in copper (easily mixed with a small amount of oxygen in copper smelting) has a great influence on the conductivity, so the copper used in electrical industry must be oxygen free copper. In addition, lead, antimony, bismuth and other impurities will make copper crystal can not be combined, resulting in hot brittleness, also affect the processing of pure copper.
This kind of pure copper with high purity is usually refined by electrolysis: the Impure Copper (crude copper) is used as anode, the pure copper as cathode, and the copper sulfate solution as electrolyte. When the current passes through, the Impure Copper on the anode gradually melts, and the pure copper gradually precipitates on the cathode. Copper thus refined; The purity can reach 99.99%.
Red copper is a relatively pure copper, generally can be considered as pure copper, conductivity, plasticity are better, but the strength, hardness is poor.
Properties and uses of brass
Brass is a kind of copper containing other alloy components. Its price is cheaper than that of red copper. Its conductivity and plasticity are worse than that of red copper, but its strength and hardness are higher.
Brass is an alloy of copper and zinc. The simplest brass is copper zinc binary alloy, which is called simple brass or ordinary brass. The higher the content of zinc in brass, the higher the strength and the lower the plasticity. The zinc content of brass used in industry is not more than 45%. No matter how high the zinc content is, brittleness will occur and the alloy properties will deteriorate.
Adding 1% tin to brass can significantly improve the corrosion resistance of brass in seawater and marine atmosphere, so it is called “Navy brass”. Tin can improve the machinability of brass. Lead yellow copper is what we usually call easy to cut national standard copper. The main purpose of adding lead is to improve the machinability and wear resistance, but lead has little effect on the strength of brass. Carved copper is also a kind of lead brass. Most brasses have good color, processability and ductility, and are easy to be electroplated or coated.
In industry and civil use, different materials are selected according to different use characteristics. If make electric wire, requirement is softer, red copper is better. If the connection piece is made, brass is often used for the screw.
Properties and uses of bronze

It originally refers to copper tin alloy. Later, except brass and Cupronickel, all copper alloys are called bronze, and are often preceded by the name of the first major additive element. Tin bronze has good castability, antifriction and mechanical properties, and is suitable for manufacturing bearings, worm gears and gears. Lead bronze is widely used in modern engines and grinding machines. Aluminum bronze has high strength, good wear resistance and corrosion resistance. It is used for casting high load gears, shaft sleeves, marine propellers, etc. Beryllium bronze and phosphor bronze have high elastic limit and good conductivity. They are suitable for manufacturing precision springs and electrical contact elements. Beryllium bronze is also used to manufacture non sparking tools used in coal mines and oil depots.
Properties and uses of white copper
Copper alloy with nickel as the main additive. Copper nickel binary alloy is called ordinary white copper; Copper alloy with manganese, iron, zinc, aluminum and other elements is called complex copper. Industrial white copper can be divided into structural white copper and electrical white copper. The structural white copper is characterized by good mechanical properties, corrosion resistance and beautiful color. This kind of white copper is widely used in manufacturing precision machinery, chemical machinery and ship components. Electrical white copper generally has good thermoelectric properties. Manganin, constantan and Kaotong are white manganin copper with different manganese contents. They are used to manufacture precision electrical instruments, varistors, precision resistors, strain gauges and thermocouples.

How to distinguish red copper, brass, bronze and white copper
White copper, brass, red copper (also known as “red copper”) and bronze (cyan gray or grayish yellow) are distinguished from each other in color, among which white copper and brass are very easy to distinguish; It is difficult to distinguish red copper from pure copper (impurity < 1%) and bronze (about 5% of other alloy components). Before oxidation, the color of red copper is brighter than that of bronze, and the bronze is slightly cyan or yellow and dark; After oxidation, red copper turns black, while bronze turns Turquoise or chocolate.

How to prevent and control pests on cable lines?

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For direct buried ACSR Cable laying, in addition to preventing external mechanical damage, there is another kind of external damage from insects, such as termites. South China is located in the subtropical zone with humid climate, which is suitable for termite breeding. Termites will damage the lead sheath of the cable, causing the insulation damp after the lead sheath is perforated. In the areas where termite activities are more frequent, the special sheathed cable with termite resistance should be selected for the cable line design. If termite breeding is found near the cable line that has been put into operation, it should immediately report to the local termite control department for termite control, and adopt centralized trapping and prevention measures.

reference:
[1] Shi Chuanqing, chief editor. Question and answer of power cable installation and operation technology

What is the valve performance of the sheath protector?

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In order to ensure that the sheath insulation will not be damaged under the action of lightning overvoltage and switching overvoltage, the sheath protector should be used. The ball gap protector was used in the early stage, but its disadvantage was that its surface was burnt by power frequency afterflow after each action. This type is not only heavy maintenance, but also unreliable. At present, zinc oxide, a non-linear resistor, is widely used in sheath protectors.
under normal operation, the current flowing through the sheath protector is microampere, so as to ensure the reliable operation of the AAC Cable.


Function of cable sheath Protector:
1. Limit the power frequency induced voltage in the metal sheath of ACSR Cable line.
In the normal working state of the cable line, the high-voltage cable sheath protector presents a high resistance state, which cuts off the power frequency induced current circuit in the cable metal sheath.
2. The power frequency and impulse overvoltage in the metal sheath of cable line can be reduced rapidly.
When grounding fault, lightning over-voltage or internal over-voltage occurs in the cable line, which leads to high over-voltage in the metal sheath, the sheath protector presents a low resistance conduction state, which makes the fault current quickly pour into the earth through the protector.


Selection of cable sheath Protector:
1. The residual voltage under the action of the possible maximum impulse current shall not be greater than the value of [impulse withstand voltage of cable sheath] – (37.5kv for 110kV cable) divided by 1.4 (included in the insulation coordination coefficient).
2. The possible maximum power frequency overvoltage shall be able to withstand without breakdown or damage under the action of 5S.
3. The protector shall not be damaged after 20 times cumulative action of the maximum possible impulse current.
Regular inspection and maintenance of cable sheath Protector:
Regularly measure the DC reference voltage of cable sheath protector at 1mA and the leakage current at 0.75 times of the reference voltage, especially after the system failure.

Operation and maintenance of protective layer protector

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In order to reduce the induced overvoltage of the metal sheath of single core AAAC Cable lines of 110kV and above, a protective layer protector should be installed between the ungrounded end of the metal sheath and the earth.

In case of system trip or line lightning stroke, special patrol shall be conducted for cable sheath protector.
The valve plate of protective layer protector may be damaged during power frequency overvoltage. The damage degree of the valve plate is related to the overvoltage of the protective layer. If the valve plate is damaged, it should be replaced.

At present, zinc oxide sheath protector is widely used in high voltage ABC Cable lines, and its residual work ratio is 2.5 ~ 4.0. Insulation resistance monitoring should be carried out for sheath protector, which can usually be tested at 500V / min.
The cross transposition box should be cleaned once a year, and the underground transposition box should also be checked for ponding.