Difference between low voltage cable and medium voltage cable

There are many kinds of AAAC Cables. According to voltage, they can be divided into low-voltage cable, medium voltage cable and high-voltage cable. What we can often touch and use in our life are low-voltage cable and medium voltage cable. How can we distinguish them? Some people say it’s 1kV, others say it’s 10kV. How to distinguish between low voltage cable and medium voltage cable? Now let Dr. Bao popularize science for you.
1、 Voltage level
According to different voltage levels, cables are habitually divided into low voltage power cables (3KV and below), medium voltage power cables (6kV ~ 35kV), high voltage power cables (66kV ~ 220kV) and ultra-high voltage power cables (above 220kV).
2、 Application and laying
Low voltage cable
Low voltage cables are used to transmit and distribute electric energy, mainly used in urban underground power grid, outgoing lines of power stations, internal power consumption of industrial and mining enterprises, and power transmission under river and sea water; It has the characteristics of reliable operation, no pole, no occupation of the ground, no hindrance to the view, less external influence and so on. The common laying methods include direct buried laying, AAC Cable trench laying, tunnel laying and wall laying.

■ medium voltage cable
MV cables are mostly produced as part of power generation and distribution networks for many applications such as utilities, petrochemicals, transportation, wastewater treatment, food processing, commercial and industrial markets. The common laying methods are underground direct buried laying; Laying of protective pipe (steel pipe, plastic pipe, row pipe, etc.); Laying of cable structures (cable trench, tunnel or working shaft, etc.); Laying in other public facilities (public facilities such as roads, railway bridges, tunnels or underground shopping malls, wharves, trestle roads, etc.); Underwater laying, etc.
3、 Observe the appearance
■ insulating materials
Low voltage power cable insulation material can be: PVC, cross-linked polyethylene;
Medium voltage power cable insulation material: cross linked polyethylene.
■ number of cable cores
The number of low-voltage power cable core is divided into: 1, 2, 3, 4, 5 core, 3 + 1 core, 3 + 2 core, 4 + 1 core
The number of medium voltage power cable core is divided into: 1 core, 3 core (so this kind of cable is mainly used for trunk transmission, 3-phase balance).
Minimum specification
The minimum specification of low voltage power cable is 1.5mm ²;
Minimum specification of medium voltage power cable: 3.6/6kv: 10mm ², 6/6kV, 6/10kV:16mm ², 8.7/10kV, 8.7/15kV:25mm ², 12/20kV:35mm ², 18/30kV:50mm ², 21/35 kV、26/35 kV: 50mm ²。
Color discrimination
Low voltage power cable cores are distinguished by different insulation colors, color lines or digital marks;
The core of medium voltage power cable shall be distinguished by ribbon.

Conductor structure
The conductor of low voltage power cable can be round non compact, round compact and irregular compact;
The conductor of medium voltage power cable must be round and tightly pressed( At present, the medium and low voltage power cables produced by our company all adopt circular compact structure
Basic structure of cable
The basic structure of low voltage power cable is conductor + insulation + filling + wrapping + outer sheath;
The basic structure of medium voltage power cable is conductor + three-layer coextrusion (conductor shielding, insulation, insulation shielding) + copper tape shielding + filling + wrapping + outer sheath.
Low voltage cable and medium voltage cable have different uses due to different voltage levels, composition, structure, etc. when choosing, you can choose according to your own actual situation.

Explore the longest 330kV cable laying site in China

Dancing a 700 meter long ultra-high voltage AAAC Cable that is thick at the mouth of the bowl and runs 3 kilometers underground, what are you doing? How many people will that take? How fierce is that? How hard is it to control?
On May 27, with a series of questions, the author came to the venue area of the 14th National Games in the northeast of Xi’an, Shaanxi Province, walked into the cable construction site of 330kV Jingxuan line I and II project of Shaanxi power transmission and Transformation Engineering Co., Ltd., and explored how to lay the longest 330kV UHV cable in China.
700 meter long cable “Jiaolong”

The 14th National Games is located in the northeast of Xi’an, and the ancient city ushers in the National Games for the first time. The relocation and landing of 330kV overhead transmission line in the northeast of Xi’an provides reliable power guarantee for the main stadium and surrounding area of Xi’an Olympic Sports Center. At the same time, by optimizing the 330kV line design and replacing the overhead line with the ground ABC Cable, the 330kV overhead line will be eliminated in the key areas of the National Games, creating a new sky landscape and showing the new style and features of the Millennium “charming ancient city” New weather.
The relocation and landing project of 330kV overhead transmission line in Northeast Xi’an involves 7 relocation and 2 new lines, 2 21km cable pipe corridors, 2 cable terminal stations and 100 km 330kV EHV cable lines, with a total investment of 8.274 billion yuan. After the completion of the project, it will be the largest 330kV and above UHV cable project in China.
The cable part of 330kV Jingxuan I and II line project is the longest and largest 330kV cable line in China. The first stage laying construction task is along the cable pipe gallery of Xingwei Road, with a total length of 6.3 km for single phase and 37 km for all cables. It is divided into nine sections, each section is 700 meters long, and each section contains six 700 meters long cables.
Green concept behind
There are 30 air vents in the underground high-voltage pipe gallery of Xingwei section, and 8 shafts for high-voltage cable laying. According to the conventional operation, each section of cable can enter the pipe gallery from the ground by selecting the nearest shaft, so as to minimize the cable transmission path. However, the actual construction scheme did not follow the conventional operation. Only two shafts were selected to enter the 9 sections of cables, and 6 of them need the whole cable to enter the pipe gallery and continue to transmit underground. After entering from shaft 24, the section with the longest transmission distance still needs to travel 3 kilometers underground, and it takes 6 hours to be in place.
Why choose this unconventional scheme of underground transmission?

“Mainly to make way for greening.” Wang Hailong, manager of Shaanxi power transmission and transformation construction project, said. High pressure pipe gallery in Xingwei section is mainly constructed by large-scale excavation except for shield construction in some sections. After the backfill treatment of the pipe gallery construction, the ground surface is planned as urban road and green belt according to the unified planning of the venue area of the 14th National Games“ Road construction, green belt planting, all need time, we occupy the site, we have to drag green back. At present, most of the greening of Xingwei road has been in good order.
Behind the posture is strength
Dancing “Jiaolong”
Following Wang Hailong into the underground high-voltage pipe gallery, he saw the sparse construction workers along the cable line, and was puzzled: “can such a few people dance the 700 meter cable?”
“Let’s call four or two thousand catties.” Wang Hailong squatted down, pointed to the roller under the cable and said, “this is the frequency conversion guide wheel, the main power of underground horizontal transmission of the cable.” A total of 900 electric frequency conversion rollers are arranged along the laying line, with a spacing of 5 meters, and a non powered roller support is arranged between the two. 900 variable frequency rollers are controlled by intelligent control box to start and stop synchronously. Although each variable-frequency roller intelligently generates a torque of 70kg, if 900 wheels rotate at the same time, the 700m “dragon” will move steadily along the passage at the speed of 6m per minute. In addition to the need for two people at the front end of the cable to lift the cable end to the next roller, the remaining 30 workers just need to watch the roller run well.
What should we do if there is any abnormality? There’s no cell phone in the tunnel. Moreover, the channel is too long and there are many turns, so the transmission distance of walkie talkie is greatly reduced.
“We have two call systems.” Wang Hailong said. They are equipped with 30 walkie talkies with coaxial cable signal relay. Another 50 walkie talkies are equipped with wireless chain relay. The two systems operate independently, which can realize the information synchronization of the whole cable laying line without delay, and ensure that the system can be shut down at the first time in case of abnormality.
“The pipe gallery is a limited space. In order to prevent accidents, we have gas masks every other section.” They did what they should have thought under special conditions.
“At the most spectacular time, there were three 700 meter long pipes running underground. The pipe gallery could not see the end at a glance, and the scene of more than 40 people dancing the 700 meter” dragon “could not be fully seen.” Wang Hailong added. Behind the grand scene is the courage, responsibility and courage of Shaanxi power transmission and transformation to seize the new challenges, explore new fields, start new engines, stimulate new power, help the new development of Shaanxi power grid, and serve the economic take-off of Shaanxi.

What is the cable compression factor, filling factor, elongation factor

Definition of filling coefficient on AAAC Cable Manual: ratio of actual cross-sectional area of conductor to cross-sectional area of core outline
Filling coefficient of circular core = sum of cross-sectional area of each single line / circumcircle area of stranded core
Fan, pad core filling factor = sum of each single line cross-sectional area / outline area of stranded core (i.e. roller hole section)
Understanding: both parameters guide the parameters after the body is processed. Do not understand as the parameters before machining

According to the definition, because the definition is the ratio of the actual cross-sectional area of the conductor to the sectional area of the outline, if the conductor is drawn, it shall be the cross-sectional area after stretching, rather than the cross-section before processing. Therefore, if the parameters of the conductor before processing are substituted for calculation, the total cross-sectional area shall be divided by the tensile coefficient as the effective cross-sectional area after the stretching
Because there are still some gaps between conductors even after the conductor is pressed tightly. In order to express the degree of tight pressure, the ratio of the conductor without clearance (i.e. the effective conductor cross-section after tight compression) to the cross-sectional area with clearance of conductor is used to indicate the degree of tightness. Therefore, it can be understood that the effective section of the whole conductor is filled into the profile section, and the percentage of effective section filled with effective section, The larger the filling coefficient is, the greater the ratio of the actual effective section to the profile section after machining, the closer it is, and the looser the other is
After the circular core is pressed tightly, the outer circle area is the outline area of the core. For the sector and tile core, the contour area is difficult to calculate. Generally, the contour area of the core after pressing is not considered after the roller is drawn (that is, the contour cross-section area of the roller is the same as the actual contour sectional area of the conductor), the cross-section area of the roller hole is the contour area of the core
For the concept of the coefficient of tension, this is to facilitate understanding. Generally, the filling coefficient of conductor is also called the compression coefficient, which is equivalent to the common name. In the case of not really understanding the meaning of the coefficient of tension, it is very easy to think that since it is a compression coefficient, the lower the value, the tighter the pressure, This should be a false understanding. That is, the direct and direct view of the compression coefficient is the ratio of the effective cross-section after compression to the effective cross-sectional area before the compression or the ratio of the profile section (or conductor outer diameter) to the profile section (or outer diameter of conductor) before the compression. Both of these two understandings are incorrect. The former can only reflect the degree of tension of the conductor and cannot reflect the degree of compression, The latter can not reflect the degree of tension accurately. Imagine that if the conductor is pressed to zero gap under ideal condition and the tension is still under the action of external force after compression, the ratio of the compressed contour area to the contour area before compression will be a value that changes with the tensile strength. This can not reflect the degree of compression. According to the definition of filling coefficient, As long as the actual section after compression is the same as the profile section, the compression coefficient is 1, i.e. zero clearance. No matter how stretched, it is always the same filling coefficient
In some places, we often see some statements, such as the coefficient of compression is generally 0.89-0.92, and it is impossible to reach 0.85. This is unreasonable. It should be said that the compression coefficient is generally 0.89-0.92, and it cannot reach 0.98. Because the compression coefficient of 0.85 is very loose, rather than pressed very tightly. The compression coefficient of one compression is relatively small, and the layered compression is larger

The extension coefficient is defined as the ratio of the effective cross-sectional area before the conductor is stretched to the effective cross-sectional area after the conductor is stretched. Generally, the higher the degree of conductor compression, the greater the external force is required, so the greater the tensile strength is, The larger the extension coefficient is, the effective section before the conductor is the sum of the cross-sectional area of all single conductor before stretching. The effective section after stretching shall be the filling coefficient of conductor contour area X. the contour area of roller hole is the outline area after the conductor stretching without considering the post rolling tension. Therefore:
The elongation coefficient of the conductor = the effective area of the conductor before stretching / the contour area of the roller hole * filling factor
In this formula, it is not understood that the larger the filling coefficient, the smaller the extension coefficient is, because when the filling coefficient is larger, the smaller the contour area of the roller hole is, the product of the (contour area of the roller hole * filling coefficient) is still smaller than that of the small filling coefficient. Under the change of two variables, the smaller the filling coefficient, the smaller the tensile coefficient, the larger the filling coefficient, The greater the extension coefficient
For the measurement of extension coefficient, the standard length, such as 1 m, can be taken for weighing after processing, and then the measured weight value of unit length of conductor before processing / unit length after processing can be taken as the extension coefficient

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Common causes of appearance defects of rubber sheathed cable

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In the production process of rubber sheathed cable, appearance defects often appear, such as the surface is not smooth; There are clinker particles (early vulcanized rubber particles) or impurities on the surface; Scratch and scratch on the surface of wires and AAC Cables; There is collapse on the surface; There are twist patterns on the surface. The following are five common causes of appearance defects of rubber sheathed cables collected by cable network on the network for reference of rubber sheathed cable manufacturers:
First, the die sleeve line is too long or too short, the die mouth is not smooth and the hole diameter is too large; The temperature of head, die or fuselage is low; The low plasticity of rubber may lead to unsmooth surface of rubber sheathed cable.
Second, the rubber supplied is not clean and contains impurities; The scorch time is too short; The temperature of rubber extrusion body, die or die is too high; The rubber flow in the head is not smooth, and there is a dead angle of rubber retention; The unsmooth screw and viscose may cause clinker particles (early vulcanized rubber particles) or impurities on the surface of rubber sheathed cable.

Third, the die sleeve is not smooth and has no chamfer; There are impurities or rubber particles blocking the die; Drag the tube inside the vulcanization tube and scratch it; The small diameter of rubber gasket at the outlet of vulcanization pipe may cause Scratch and scratch on the surface of rubber sheathed cable.
Fourth, the hole diameter of die sleeve is too large; The gap between strands and monofilaments in the outer layer of conductive core is too large, and the outer diameter of cable core is uneven; The rubber has low plasticity and poor viscosity; There are impurities in the rubber; Small die distance and small pressure may cause surface collapse of rubber sheathed cable.
Fifthly, the hole diameter of die sleeve is too small; The rubber extrusion is insufficient, and the gap of wire core is not filled; Conducting core or cable core jumper; The short distance to the mold may lead to the appearance of twist on the surface of the rubber sheathed cable.

Is the cable conductor detected by the cable nose in accordance with the national standard

The AAC Cable nose is often used for the end connection and continuation of the cable, which can make the connection between the cable and electrical appliances more firm and safer. Cable companies often receive customer complaints: with the corresponding specifications of the wire nose through the corresponding specifications of the conductor, found that the wire nose is larger than the outer diameter of the cable conductor! If it is suspected that the cable is a non-standard product, let the cable enterprise send someone to explain and deal with it on site immediately; In particular, with the use of “special-shaped wire stranded cable conductor and its production method” by cable enterprises, the compression coefficient of cable conductor has increased from 0.90 to more than 0.98, and the outer diameter of cable conductor has decreased by more than 5%. In this way, cable users worry about whether the cable is non-standard or wrong cable specification after receiving the goods? Today, I want to explain to you: why is the cable nose larger than the outer diameter of the cable conductor?

The reason why the cable nose is larger than the outer diameter of the cable conductor is mainly to reduce the contact resistance of the connection and strengthen the local heat dissipation capacity. For a cable, the resistance of the whole length is evenly distributed, but no matter how much pressure you use to install the connection of the cable nose, the resistance of the contact part is always greater than that of the non connection part of the cable, resulting in serious local heating, The solution is to increase the contact area and reduce the contact resistance. At the same time, the larger the nose, its heat dissipation capacity will be higher. Generally, the area of the cable nose is 30-50% larger than the corresponding specification of the cable conductor, because the cable conductor is sometimes rolled into a fan or tile shape, which is not a pure circle. Generally, it needs to be compressed by a hydraulic press and then turned into a circle. If the inner hole of the cable nose is designed according to the nominal outer diameter of the cable conductor, some special-shaped conductors cannot be penetrated.

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Requirements for fire protection certification of cables

In order to solve the long-standing problem of the lack of flame retardant classification standards in the AAC Cable industry and the imperfection of the evaluation index dimension in the original flame retardant standard system, the former Sichuan Fire Protection Research Institute of the Ministry of public security organized relevant units to take the lead in formulating the national mandatory standard GB 31247-2014 “classification of burning performance of cables and optical cables”, which was issued on December 5, 2014 and officially implemented from September 1, 2015. On the basis of full investigation and verification test, combined with the relevant requirements of EN 13501-6:2014 and the actual grading assessment needs of domestic cables and optical cables, GB 31247-2014 finally forms four grades A, B1, B2 and B3. The assessment dimensions include the main grading indexes such as combustion calorific value, flame spread, heat release, smoke production characteristics and smoke density, and the main grading indexes such as combustion droplet / particle, smoke emission and so on The toxicity and corrosivity of flue gas are three additional classification indexes. Generally speaking, these assessment indexes can more truly reflect the combustion characteristics of cables under actual fire conditions, and the evaluation of cable combustion performance grade will be more scientific, reasonable and practical.

In order to promote the flame retardant cable classification standard and link up the related testing and certification work, China Quality Certification Center and National Center for quality supervision and inspection of fire resistant building materials (nftc) have cooperated closely since the standard drafting stage to develop cqc17-463416-2015 “implementation rules for classification certification of burning performance of cables for construction Engineering”, Since 2015, we have held publicity and implementation meetings on standards and certification in Nanjing, Yixing, Guangzhou, Jinan, Chengdu and other places, actively promoting the application and acceptance of standards to relevant architectural design units and architectural design specifications, and achieved good promotion results. This work also lays a foundation for the domestic flame retardant cable export to meet the relevant technical requirements of the European Union CPR building product regulations.
Considering the identification and type selection requirements of cables with different flame retardant grades, the new version of the implementation rules (cqc17-463416-2020) in 2020 adds the model naming provisions of cables with flame retardant grades, and adds some products with flame retardant grades B1 and B2, such as wdzb1-yjy, zb2-bv, etc., and provides the new products to Jiangsu Shangshang, Wuxi Jiangnan, Wuxi Jiangnan, etc Some excellent cable enterprises such as Jiangsu Zhongmei and Sichuan Xinshiji have issued the first batch of new CQC fire prevention certificates.

The new version of CQC fire prevention Certification Implementation Rules includes power cable, wiring, control cable, computer cable, flexible cable, communication cable, optical cable and other construction cable products. The CQC fire prevention certification mark shown in Figure 1 can be applied to the certified products to prove that the products meet the relevant requirements of each flame retardant grade. After the implementation and promotion of flame retardant classification standards and certification, many laboratories including the National Center for quality supervision and inspection of fire resistant building materials, the National Center for quality supervision and inspection of wire and cable products (Yixing) and Shanghai ABC Cable wisdom Testing Technology Co., Ltd. (istcw) have obtained the relevant recognition of the flame retardant classification certification.
3、 Some misunderstandings and development prospects of flame retardant graded cables
In recent years, with the popularization and application of GB / T 19666 “general rules for flame retardant and fire resistant wires, cables or optical cables” and the flame retardant categories of ZA, ZB, ZC and ZD, due to the common sense tendency to code a-b-c-d level arrangement and the non-metallic content from high to low in the test, there are a large number of manufacturers, users and technical institutions in the industry that bundle flame retardant ZA, ZB, ZC and ZD are flame retardant levels, It is also understood that flame retardant class A is superior to (covering) class B, class C, and then to class D.
However, the standard analysis shows that the main difference of bunched flame retardant (ZA, ZB, ZC, ZD) categories lies in the different application and evaluation occasions, and the grade relationship or classification concept is not mentioned in the relevant standards. In particular, in the article “understanding and suggestions on the requirements of Flame Retardancy for wiring bundles” recently received in the Journal of quality and certification, verification tests were carried out on five groups of samples of typical wiring products from different manufacturers: za-bv 450 / 750V 2.5 and wdza-byj 450 / 750V 2.5, and the above ten groups of samples were tested in accordance with GB / T 18380 series standards Class C and class D combustion tests. By analyzing the carbonization height of the samples before and behind the steel ladder after the combustion test, the results show that the carbonization height of most of the bundles of this kind of wire products is higher than that of class A, and even some of the samples have passed the flame retardant class a test, and the flame retardant class D is unqualified. The bundle combustion verification test of this cloth and wire product also proves that the traditional bundle flame retardant ZA, ZB, ZC and ZD do not belong to the classification of flame retardant performance, and there is no relationship between high and low levels.

In contrast, GB 31247-2014 “classification of burning performance of cables and optical cables” scientifically and systematically classifies the burning performance of cables used in construction projects through multi-dimensional index assessment and evaluation, which is close to the requirements of actual building fire safety scenarios, and gives a clear description of the performance grade in the standard, for example, the burning performance B1 is flame retardant 1 cable (optical cable), The combustion performance of grade B2 is flame retardant grade 2 cable (optical cable), etc( This also lays a solid foundation for the reference and acceptance of GB 31247-2014 flame retardant classification in GB 51348 standard for electrical design of civil buildings.
It is believed that with the promulgation and heavy implementation of GB 51348 “standard for electrical design of civil buildings” and subsequent relevant design specifications, a more unified and clear understanding and application of the classification of combustion performance of cables and optical cables will be formed from user units, design units, supervision units, testing and certification Institutions to manufacturers and other relevant policies, The flame retardant cables and optical cables used in domestic construction projects will also usher in a brighter development prospect.

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Conductor outer diameter in selecting and purchasing wires and cables

With the development of national economy, urban construction is becoming more and more prosperous, and the market demand for decoration cloth and wire products is strong. Cloth and Wire Manufactor products belong to CCC compulsory certification products. Domestic manufacturers implement the national standard GB / T 5023-2008 when producing. Manufacturers must send the products to the designated authoritative testing agency for performance testing every year, It is illegal to obtain the production license by virtue of the inspection report and on-site audit, if the product is produced without the production license.

Through market investigation, when consumers compare products of the same specification in the market, they often find out why the outer diameters of conductors of different manufacturers are different. For example, take the conductor for 6mm2 wiring as an example, the outer diameters of conductors of some manufacturers are 2.76mm, and those of some manufacturers are 2.90mm or even larger, which creates an illusion for consumers, The larger the outer diameter of the conductor, the better the wiring. In fact, it is not. In view of this situation, the following three aspects are discussed:
1. Standards
In the old version of GB / T 5023-1985, the outer diameter and DC resistance of conductor are strictly specified, and the outer diameter of conductor for 6mm2 wire is 2.76mm; In 1997, the new national standard GB / T 5023-1997 for wire laying stipulated that the conductor performance index must meet the requirements of GB / T 3956 (national standard for cable conductor), while the maximum outer diameter of conductor for 6mm2 wire laying should not exceed 2.90mm in GB / T 3956; In the new edition of national standard GB / T 5023-2008, the requirements for outer diameter of conductor are the same as those in GB / T 5023-1997, that is, the maximum outer diameter of conductor for 6mm2 wiring shall not exceed 2.90mm( At present, GB / T 5023-1997 is the latest effective national standard for wiring, which has replaced GB / T 5023-1985 and GB / T 5023-1997
2. Craft
The outer diameter of conductor (2.76mm) is strictly stipulated in GB / T 5023-1985, but the maximum outer diameter of conductor (2.90mm) is only required in GB / T 5023-1997 and GB / T 5023-2008. This is mainly because: in the 1980s, the smelting process level of raw material copper was not high, and there were many impurities in copper rod, which resulted in high conductor resistance, The national standard strictly requires the outer diameter of wire conductor. With the continuous development of copper smelting level and the improvement of conductor processing technology, the impurity content in copper is getting smaller and smaller. At present, in the industry, under the condition of ensuring that the DC resistance of conductor meets the requirements, the outer diameter of conductor produced has been reduced correspondingly, and the consumption of copper has also been reduced correspondingly, This is also the reason why the national standard only specifies the maximum outer diameter of the conductor, but does not specify the specific value of the conductor.

halogen free cable
3. According to the DC resistance formula of Conductor:
R= ρ× L/S
R is the DC resistance of conductor;
ρ In the ambient temperature of 20 ℃ ° Resistivity of conductor at different time
L is the unit length of conductor
S is the cross-sectional area of the conductor
According to the formula, in order to ensure the current carrying capacity of the wire to meet the requirements, the DC resistance of the conductor must meet the requirements of the standard ρ S is related to the diameter of the conductor, ρ When the DC resistance of the conductor is constant, when the outer diameter of the conductor is large, the resistance of the conductor will decrease ρ If the outer diameter of the conductor is small, the copper purity will decrease ρ The purity of copper increases with the decrease of the temperature.
According to the analysis of the above three aspects, when consumers choose wire products, the size of the outer diameter of the wire conductor can not be used as the only standard to judge whether the product is qualified or not, that is, when the wire specifications are selected, the larger the outer diameter of the conductor is, the worse it is. Therefore, the product quality should be judged according to the direct current resistance and mechanical properties of the conductor.

Up 80%! Some people “cover” copper not sold

“Do you have a copper machine tool? We can make a home valuation! ” Lao Zhao is a recycling business of scrap metals. Recently, he is circulating recycling advertisements by friends.
After the Spring Festival, copper prices have set a high, recycling manufacturers are looking for scrap copper. Zhao also took the opportunity to make a profit in this wave of market. He said that before the Spring Festival, the price of copper acsr cable was about 40000 yuan per ton, and now it has risen to more than 70000 yuan a ton, or nearly 80 percent.

With the continuous increase of copper price, the raw material cost pressure of downstream metallurgical and processing enterprises is becoming increasingly prominent. In this context, relatively low-cost and environmental protection of waste copper has become “fragrant bun”.
Industry insiders said that the rising copper price and the increase of copper cost are the main reasons for the popularity of recycled copper resources. In the future, the depletion and supply reduction of copper resources abroad will be the trend of the whole world. The market of urban mines and recycled copper resources will have unlimited potential.

Downstream telephone burst, waste copper recycling station “cover not sell”

Near a scrap metal recycling station in the suburb of Tanggu, Tianjin, the abandoned copper wires were piled on the roadside, and the sun was golden. Once, this is the “urban waste” that nobody asks for. Nowadays, they are precious renewable resources that enterprises plunder.
In the warehouse built up by color steel plate, Shanghai Securities News reporter saw that the door was a black and abandoned cable, which was randomly collected by several sacks. Walk down the wall, and the white sack behind it is filled with yellow copper cables. The staff said that these are copper wires picked up from the cable at the door. Once, these copper wires were not worth a few money, and now they are worth a lot.

“We have been operating this recycling station for more than ten years, and this year’s good market has hardly seen.” Lao Qin, the head of the recycling station, said that the scrap copper sold only 40000 per ton a ton a ton a year ago, but there was not much downstream goods, and the warehouse was filled with goods that could not be sold. After the Spring Festival, copper and brass cables suddenly became “fragrant bun”, which has exceeded 80000 yuan per ton.
In the past, recyclers were “unreasonable” about copper waste resources, waiting for customers to ask for the recovery price. Now they are starting to drive to factories around the country to find copper scrap valuations.
The copper recovered by Laozhao in Shanghai comes from the abandoned machine tools, cables, copper pots, and parts removed from various old appliances. He took his recycling company for example, in the past, after he recycled and processed it every month, copper sold at most 12000 yuan, and now it can reach more than 100000 yuan per month“ Taking advantage of the high copper prices in recent months, I have shipped all the hoards that I couldn’t sell in the past, making a lot of money net. ”

However, more copper recyclers have a “business experience” and do not rush to sell the accumulated copper to intermediate agents or downstream copper refineries.
“Copper is now priced one day, and the cable copper, which was once slow to sell after the Spring Festival, is almost double.” Old Meng, boss of the scrap metal recycling base from Foshan, said.
Old mengning can backlog some scrap copper, and sell them together when prices are higher. The recyclers around him also sniffed business opportunities. Although agents and middlemen called to order goods every day, they still covered the scrap copper in their hands.
Such “business” also sinks to the basic environmental sanitation workers. According to a big data service provider for waste products in Chengdu, at present, many environmental sanitation workers in Chengdu will consciously look for copper containing cans and electronic components, “the items were sold for a maximum of 1200 yuan a day before, and now they can sell threeorfour yuan or more.”
Although the price of scrap copper has risen greatly, the sales profit of different recycling stations is quite different. Shanghai Securities News reporter understands that compared with the previous year, the most of them have reached several times or even ten times, while the few are only 30%. According to zz91 regeneration network data, as of the 12th, the average price of main copper scrap in Jiangsu, Zhejiang and Shanghai was about 65000 yuan / ton, up 32% from the beginning of the year.
In response, Wu Xinyong, an analyst in the copper industry of Shanghai Nonferrous network, said the main factors determining the profit of scrap copper recovery are the recovery cost when recycling and the price difference before the delivery price at the time of sale. If the scrap copper is recovered at the low point of copper price before the year ago and sold at the current copper price high, the intermediate profit will be considerable.

“Price difference between refined waste” and the economy of waste copper are highlighted

As for the phenomenon of copper scrap is tight since this year, Wang siran, director of Ping An Futures Research Institute, told Shanghai Securities News that in practice, many products of copper processing enterprises can take refined copper as raw materials and scrap copper as raw materials. There is a price difference between scrap copper and refined copper, and the price of scrap copper is not as fast as that of refined copper.
Wei Lai, director of all color research of Tianfeng futures research, told Shanghai Securities News that since this year, downstream enterprises have been in stable demand for copper, especially in emerging fields such as new energy vehicles, electronics, home appliances and other industries, with higher demand for copper. With the continuous increase of international copper price, the economy of waste copper has been highlighted. Because of the excessive cost of using refined copper, processing and smelting enterprises tend to increase the consumption of waste copper.
“The supply of copper concentrate abroad is relatively tight this year, and there are epidemic and strike in the main production areas of copper concentrate such as Chile.” Wei Lai said.
In March, copper production in Chile has fallen for 10 consecutive months, according to data. According to the National Bureau of statistics, Chile’s copper production in the first quarter of 2021 was 1.4 million tons. The year-on-year decrease was 2.2%.
The decline in copper production has shifted some demand to scrap copper, which also promotes domestic imports of scrap copper. My non-ferrous network data show that, due to steady growth of downstream demand, the import of recycled copper has increased significantly since this year. In the first quarter of 2021, the import of recycled copper was 363700 tons, an increase of 73.39% year-on-year.
“The use of scrap copper is no longer new. The industry has mature technology to convert waste copper into refined copper. From the perspective of environmental protection and carbon neutralization, it is also in line with the trend to increase the use of waste copper. ” Wei Lai said.

On the core breaking of flame retardant copper wire and cable

With the development of economy, the industry of wire and cable is also changing and developing. The application demand of wire and cable is also increasing. Meanwhile, the flame retardant and fire-resistant wires have emerged. How to detect the quality of these wires? So, let’s talk about the detection of the core breaking of flame retardant wires and cables!
1: The method of electrifying capacitance
Some aaac cable factories usually use capacitance comparison to find out the approximate position of broken wires. The efficiency of the method is very low, which is to use continuous power on to accurately break the cable. Generally, it takes about 1 and a half hours to find a broken line point. This method is very unlikely to find the broken core for the flame retardant cable which has been completed in the shielding, armouring and sheath process. If it is not made properly, the flame retardant cable will be discarded. This method is basically no longer used.

2: The capacitance method and the induction method are combined
This method is used for core breaking, which requires that there is no metal layer and no extrusion cover outside the core. In the search, we first find out the approximate position of cable break with capacitance, and then use inductive voltage method to find the broken point accurately. This method is very simple and fast, and it is also the most used method at present. The induction voltage method is to connect 650V AC voltage at one end of the broken core of the cable, and the other end and other cores to ground, and then test with an inductive pen which can send light signal. When the probe slips out of the core, the signal will change, so that the cable break point can be accurately found.

3: Combination of constant current source and bridge method
This method is used for completed cables or cores covered with metal layers. The method of finding is to burn and break down the insulation at the broken core of flame retardant cable with constant current source, and then to locate the fault point accurately by bridge fault location instrument, which is also a common method.

Buy Wire and Cable These Knowledge Points You Want to Know!

                                                      First tip: first understand the meaning of Aerial Bundled Cable (ABC) BS 7870 Standard

Use code: A installation line, B cloth wire, C Marine cable, R flexible cable, K control cable, N agricultural cable, M coal cable, U mine cable, JK overhead cable;ZC flame-retardant cable, NH fire-resistant cable, WD low smoke free halogen cable.

Characteristic code: B flat, R soft, C heavy duty, Q light duty, Z medium duty, S twin type, P shield, L aluminum core, V insulated polyvinyl chloride, YJ crosslinked J polyethylene, H welding machine.For example, WDZN-BYJ stands for polyethylene insulated low smoke no halogen flame retardant wire, its rated voltage is 450/750V.


                                                             Second recruit: choose PVC Sheathed Power Cable according to the purpose

When choosing wires and cables, use, laying conditions and safety should be considered.Such as:

According to the different electrical appliances, optional wire, power cord, twisted pair, red and black wire, video cable and so on.

According to the different uses, can choose power cable, fire cable, overhead insulated cable, control cable, etc.

According to different laying conditions, cross-linked cable, armoured cable, aluminum alloy cable, anti-corrosion cable and so on can be selected.

According to the safety requirements, can choose flame retardant cable, halogen-free flame retardant cable, fire resistant cable, etc.



                                                                            Third recruit: choose cross-sectional area namely specification

The specifications of home wiring have dozens of specifications such as BV2.5, BV1.5, BV4, BV6;BV is a national standard code, and the numbers are our traditional square number of wires. In general, the wires are used as:

1,The 6 square meters are suitable for households, because the demand for land used by households is high.

2, 4 square suitable for the kitchen switch socket separate line and air conditioning water heater line, after all, these are power consumption, the wire specification can carry more electrical appliances as far as possible;

3, 2.5 square wire used in the common switch, socket and lighting main line;

4, 1.5 square for lighting control circuit switch, etc.

The specification of wire and cable is not the bigger the better, choose the right one is good, the specification is too large will only waste electricity

                                                                              Fourth recruit: choose brand heavy service

The safety and reliability of wire and cable should be guaranteed as the common wire in life.Therefore, when purchasing wires and cables, we should start from our own actual situation and buy reliable old brands. We should consider more from the practical aspect, so that quality, price and after-sales service can be guaranteed.

Jin Hautai, Dongguan wire and cable dealer, I hope this article can help you.