Pithy formula and interpretation of common cable selection

In our daily sales, we may encounter customers asking about ACSR Cable selection in the process of maintenance and repair. As a cable salesman, choosing the right cable for customers is the top priority of this work.
First, the actual power of the load should be considered, at the same time, the maximum current to be borne by the cable should be calculated, and then the appropriate cable should be selected. The following is the relevant contents sorted out by the editor in AAAC Cable treasure. I hope I can provide some help for my colleagues.

[doggerel]: five out of ten, two out of one hundred, fifty-three out of four, and 75% off for buried casing.
[explanation]: according to the total current required by the insulated conductor, when the total current is less than 10a, the cross-sectional area of the conductor per square millimeter can pass 5A current, if it is more than 100A, it can only pass 2A current per square millimeter, 4A current per square millimeter between 10 ~ 50A and 3a current per square millimeter between 50 ~ 100A. After this calculation, In case of buried or casing laying, the current value that can be passed shall be multiplied by 0.75.
The calculation method given above obtains the allowable current per square millimeter. The selection of the actual specific conductor section should be: first determine the current required by the electrical equipment (including rated current and appropriate margin), then compare the current range in the doggerel according to the required current value, and then the conductor section that should be selected can be obtained by “allowable current per square millimeter” belonging to the range at the required current value.

For example, the rated current of an electrical equipment is 20A. Considering a certain margin, the required current is determined to be 22a. Then, find out that the current range of 22a current in the above doggerel belongs to 10 ~ 50a, and the available current per square millimeter is 4a. Finally, divide 22a by 4a to obtain the conductor section s that should be selected as:
S = 22 / 4 = 5.5 (mm2). According to this value, the conductor with corresponding section can be selected. If the calculated sectional area is not in the conductor section specification series, a slightly larger conductor section can be selected.

How to skillfully use aluminum alloy cable in photovoltaic system?

The cost of control system is very important in the era of photovoltaic affordable Internet access. Over the past decade, the price of modules and inverters has decreased by 90%, which has made a great contribution to the overall cost reduction of photovoltaic system, but the cost of cables has not decreased. In large projects, the proportion of cables in the system reaches 10%, which is higher than that of inverters. In fact, as long as the design and installation are proper, on the premise of ensuring the normal operation and safety of the system, some AC cables adopt aluminum alloy cables, which can reduce some costs.
The cables of photovoltaic power station are divided into DC cables and AC cables. The DC cables between components and between components and inverter are generally required to use photovoltaic special DC cables, while the cables from inverter to AC distribution cabinet and from distribution cabinet to transformer are not required to use any ACSR Cables.

What is aluminum alloy cable: aluminum alloy cable is a new material power cable with aa8030 series aluminum alloy material as conductor. The resistivity of aluminum alloy is between aluminum and copper, higher than copper and slightly lower than aluminum. Under the premise of the same current carrying capacity, the weight of aluminum alloy conductor with the same length is only half of that of copper.
When the cross-sectional area of aluminum alloy conductor is 1.5 times that of copper, aluminum alloy ACSR Cable and copper cable achieve the same current carrying capacity, resistance and line loss.
Service life: different metal oxides are formed after the metal surface reacts with oxygen. Aluminum oxide can form a dense surface protective film with a certain hardness. Copper oxide, commonly known as copper green, is a toxic substance between the above two.
Economically, this is the most important aspect. The cost of aluminum alloy cable is about 25% ~ 50% of that of copper core cable. The cost advantage of aluminum alloy cable is relatively large. We can make a comparison. In a 400KW village level poverty alleviation power station, the distance from the AC distribution cabinet to the step-up transformer is 1500 meters, and the maximum output current of the 400KW power station is 580A. If copper cables are used, two 150 square meters are required for each phase and six for three phases, with a total length of 9000 meters and a price of 864000; If you use two 240 square meters of aluminum alloy, the total length is 9000 meters, and the price is 450000 yuan, 414000 yuan can be saved, and the loss of 240 square meters of aluminum wire is lower than that of 150 square meters of copper wire.

There is also a rare earth aluminum alloy cable, which is made of high elongation aluminum alloy material. By adding rare earth trace element materials such as boron to pure aluminum and treated by rolling technology and special annealing process, the cable has good flexibility. When its surface is in contact with air, it can form a thin and firm oxide layer, which can withstand all kinds of corrosion. Even when overloaded or overheated for a long time, it can ensure the stability of the connection, and the cost is about 10% higher than that of ordinary aluminum alloy cable.
Application scope of aluminum cable: aluminum cable can be considered for long-distance overhead line, underground cable trench with large space and places with reliable fixed bridge.
Precautions for use of aluminum cable:
The melting point of copper is 1080 ℃, while that of aluminum and aluminum alloy is 660 ℃, so copper conductor is a better choice for fire-resistant cable. At present, some aluminum alloy AAC Cable manufacturers claim that they can produce fire-resistant aluminum alloy cables and have passed the relevant national standard tests, but there is no difference between aluminum alloy cables and aluminum cables. If they are in the fire center, that is, when the temperature is higher than the melting point of aluminum alloy and aluminum cables, no matter what heat insulation measures are taken, the cables will melt in a very short time and lose their conductive function, Therefore, aluminum alloy should not be used as fire-resistant cable conductor, nor in densely populated urban distribution network, buildings, factories and mines.

Compared with aluminum core cable, the copper core is flexible, the allowable bending radius is small, and it is not easy to break after repeated bending. Therefore, aluminum cable should not be used when there are many bends, many pipes or complex lines.
As the terminals of electrical switchgear are made of copper, copper and aluminum are directly connected, and the chemical reaction of primary battery will occur after power on: aluminum with higher activity will accelerate oxidation, resulting in higher resistance and lower current carrying capacity at the joint. Therefore, some measures need to be taken when copper and aluminum are connected, such as using copper aluminum transition terminal or copper aluminum transition terminal block, Eliminate electrochemical reaction.

What is the content of periodic test for high voltage cable?

“Power cable operation regulation” stipulates that under the condition of not losing normal oil pressure, it is not necessary to conduct DC withstand voltage test regularly for high voltage oil filled AAAC Cable. As long as the oil pressure is normal and the dielectric loss and breakdown strength of oil are qualified, it can be considered that the cable insulation is reliable. Therefore, oil filled cable should be tested regularly to measure its dielectric loss and breakdown strength. The test period is generally sampled one year after putting into operation. If the results of two consecutive tests do not change, the test period can be gradually extended. In addition to the oil sample test, the following tests should also be carried out.

1. Measure the insulation resistance of outer sheath
the outer sheath of oil filled cable not only insulates the metal sheath from the ground, but also has anti-corrosion effect on the lead sheath and reinforcing tape. The insulation resistance of the sheath of oil filled cable shall be measured once a year by insulation resistance meter or other methods to check the integrity of the sheath insulation and the degree of water seepage. The high pressure oil filled cable is under the positive oil pressure, and the moisture in the air cannot invade people. Periodic measurement of outer sheath insulation can find out the early mild damage of sheath. When measuring the insulation of protective layer, the transposition bar and protector on transposition board in cross interconnection box shall be disassembled, and the insulation resistance of protective layer shall be measured by sections. Long lines shall be measured with electric insulation resistance meter.

2. Measure the grounding resistance
in the sheath grounding system with two ends grounded, one end grounded or cross interconnection connection, the value of grounding resistance will affect the operation of the protector. GEOX type grounding resistance measuring instrument can be used to measure the grounding resistance of the cable sheath connected with the grounding electrode or the grounding connecting line of the protector.
3. Measure the DC resistance of conductor
by measuring the DC resistance of the conductor and comparing it with the test values in previous years, we can check the change of the contact resistance between the outgoing stem or connecting pipe and the cable core, and judge whether the conductor connection is good.

What is the national standard cable

National standard ACSR Cable, literally, is the wire and cable produced in strict accordance with national standards. China has clear regulations on the appearance, mechanical strength, insulation of sheath, withstand voltage strength and line resistance of cables. There are different national standards for different types of cables, mainly as follows:
·Executive standard for irradiation crosslinked power cable (0.6 / 1KV): GB / t12706.1-2008
·Executive standard for medium voltage XLPE cable (6 / 6kv-26 / 35kV): GB / t12706.2-2008
·Executive standard for high voltage XLPE cable (64 / 110kV): GB / t11017 – [/ b] 2002
·Executive standard of control AAAC Cable (450 / 750V): gb9330-88
·Executive standard for aluminum strand and ACSR (0.6 / 1KV): GB / t1179-1999

How to distinguish national standard cable?
I want to see it. See if there is quality system certification; Check whether the certificate is standard or not; Check whether there is factory name, address, inspection seal and production date; See if the trademark, specification, voltage, etc. are printed on the wire. But also look at the cross-section of the wire copper core, superior copper color bright, soft color, otherwise it is inferior.
Try. Take a wire head and bend it repeatedly by hand. Those with soft handle, good fatigue resistance, high elasticity of plastic or rubber handle and no crack on the wire insulator are excellent products.
weighing. Good quality wires are generally within the specified weight range. For example, the commonly used plastic insulated single strand copper wire with a cross-sectional area of 1.5mm2 weighs 1.8-1.9kg per 100m; The weight of 2.5mm2 plastic insulated single strand copper wire is 3-3.1kg per 100m; The weight of the poor wire is not enough, or the length is not enough, or the copper core of the wire is too much impurity.
Look at the copper. Qualified copper wire copper core should be purplish red, glossy and soft. The copper core of the fake copper wire is purple black, yellow or white, with many impurities, poor mechanical strength and poor toughness. It will break with a little force, and the wire is often broken. When checking, you only need to strip one end of the wire for 2cm, and then rub it on the copper core with a piece of white paper. If there is black substance on the white paper, it means that there are more impurities in the copper core. In addition, the insulation layer of fake wires seems to be very thick. In fact, most of them are made of recycled plastics. Over time, the insulation layer will age and leak electricity.
Look at the price. Because of the low production cost of fake wires, vendors often sell them at low prices under the guise of low price and good quality.

“Non standard / enterprise standard / market national standard” and “national standard of resistance protection”?
When many sales companies are asked whether they are GB cables, they often hear such words as “GB for market” and “GB for resistance protection”. Many people have little understanding. What do these vague words mean?
Resistance national standard: cable is used for power, and conductor resistance directly affects the conductivity. If the conductor resistance is too large, the conductivity is poor, when there is a large current through, it will produce a lot of heat, which will cause a fire. At the same time, because of the high resistance, it will also produce heat and inaction consumption of electric energy.
Resistance cable is to ensure that the resistance value of the cable is in line with the national standard, but it does not guarantee that the component materials of the cable are completely produced in accordance with the national standard, such as conductor square, insulation, sheath, etc. To put it bluntly, it means that through various technological innovations (or means), the manufacturer can make the cable reach the safe use condition on the premise of reducing the material cost.
Note that two words are used here: innovation and means. Innovation refers to the cost reduction through technological innovation, such as the current aluminum alloy conductor, special-shaped conductor, etc., which reduces the price on the premise of ensuring safe use. Some manufacturers reduce the cost through some illegal means, such as using second-generation materials, reducing the purity of conductor, etc. even if the resistance value of such cable is within the standard range, its use is extremely unsafe. When purchasing this kind of cable, it must be screened again and again.
“Enterprise standard / non-standard / market national standard”: these words are easy to understand, “enterprise standard / non-standard” is non-national standard cable, the price is extremely low, and it is also extremely unsafe“ Market national standard “generally refers to 9 fold cable (or 95 fold), we must not regard it as national standard, we must ask clearly. In addition, we should pay attention to the fact that the enterprise standard is higher than the national standard in accordance with the principle, but the domestic standard does come in the opposite direction!
In recent years, there are more and more fire accidents caused by unqualified wires and cables, many of which are purchased unqualified products due to the lack of cable knowledge. It is our duty and responsibility to produce and purchase GB cables, so as to ensure the safety of power supply and the healthy development of cable market.

High voltage cable intelligent anti breaking system

Project background

If the city grid is given life, the AAAC Cable is his blood vessel, which injects the energy of the power grid.
However, with the development, the construction frequency is high, which leads to the explosion of the risk of cable external force damage. Please see, this is the scene after the cable has been destroyed. Then, once the underground cable is damaged by the external force of construction machinery, it may cause chain reaction and lead to large-scale power failure.
If the power outage occurs in hospitals, transportation hub, government agencies and other important places, how much loss will be suffered to the people’s lives and property, and the indirect economic losses caused by the power failure are immeasurable; On the other hand, cable damage may also lead to the construction of personnel casualties. In view of this, it is urgent to prevent external damage!

Traditional cable inspection mainly relies on manual field inspection, which makes it difficult to find out the cable external breakage due to various mechanical construction on the ACSR Cable path in time and accurately. There are few operation and maintenance personnel, and the inspection mode mainly depends on the drawing and oral communication to confirm the cable location. Inspection efficiency is low and maintenance cost is high.

Function and characteristics of the scheme

With the national policy support for the digital transformation of state-owned enterprises and the promotion and application of 5g technology, our team seized the opportunity to break through the bottleneck, combined smart IOT technology with cable anti-external breaking work organically, and independently developed “intelligent brain – high voltage cable intelligent external breaking system based on artificial intelligence”.

Function 1
The full time visual monitoring device is applied to improve the real-time visibility of the equipment channel. The visual monitoring device is installed on the smart light pole in key cable channels and construction intensive areas, which can automatically identify the hidden dangers outside the cable channels such as large construction machinery.
The real-time data collected by camera is compared with the hidden danger image database of cable channel, and all kinds of external damage hazards on cable channel are automatically studied and identified.
At the same time, the system has the ability of autonomous learning, and with the deep use of the system, the recognition efficiency is improved.
Function 2
The fiber vibration technology is applied to improve the state perception of the equipment. The abnormal vibration caused by external force is automatically captured, and the warning is given before the external force endangers the power cable. According to the external vibration of optical fiber, the external force failure signal is automatically identified and the location of the hidden danger of external failure is accurately located.

Function 3
The application of “four-dimensional” visualization technology can enhance the visual operation and maintenance capability of underground cables. Realize the operation and maintenance personnel to stereoscopic view the cable lines and auxiliary facilities in VR form on site through PDA terminal, and guide the accurate operation.

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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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How to select cable label

AAAC Cable label is an identification mark used in field installation and after maintenance.
The purpose of cable identification is
Ensure the organization and correctness of installation
And the convenience of maintenance and inspection later.
This paper is to share the purpose, characteristics and how to choose cable label for you.

Application and characteristics of cable identification
In a line system, it is impossible for the operation and maintenance personnel to memorize a wide range of equipment and lines. In order to make sure that they do not miss in the inspection, it is necessary to manage the line identification. After marking each line, it shall be sorted and summarized and posted in a conspicuous position. In the future, it can be done without omission if the inspection is carried out in strict accordance with the project requirements.
Cable identification system can not only provide correct guarantee for the operation and maintenance personnel to carry out correct daily maintenance and abnormal accident handling, but also provide help for the later generations. Even if the new personnel are employed, as long as the identification is followed, there will be no misoperation.
How to select ACSR Cable label
Mark before or after the terminal is completed
Cable identification card: 1. It can be used before or after the terminal connection. 2. The content is clear. The label is completely wrapped around the cable.
Heat shrinkable cable identification pipe: 1. It can only be used before the terminal is connected, and is sheathed on the wire through the open end of the wire. 2. Before heat shrinking or splicing, the label can be replaced randomly. 3. After the terminal is jacketed, the sleeve will become a permanent mark which can withstand the bad environment. And it’s low cost.
What is the diameter of the cable
The diameter of the cable determines the type, length, or diameter of the sleeve to be identified. Cable identification card is widely used in large square cable, large logarithmic cable and outdoor optical cable. The heat shrinkable label tube is widely used on the small square secondary small line. Identification cards can be used for various cables of different diameters.
What environment will cable labels be placed in
Factors to consider include:
1. Is there any contact with oil, water, chemicals or solvents?
2. Is flame retardant required?
3. Does the state have any special or other provisions on this?
4. Is it used in clean or other environments? Even in the harsh environment, the heat transfer printing, industrial grade printing quality, has strong anti pollution, in fact, the print content is also “anti oil pollution”.

Do you plan to print or buy pre processed logo yourself?
Purchase cable identification
1. There are a variety of preprint content available for selection;
2. If the demand is large, it can provide customized preprint content;
3. There are various kinds of marks such as card and sleeve type, which can be selected, convenient to use and convenient for transportation;
4. It is suitable for various applications.
Print logo by yourself
1. Print various content as needed (even if you print very little);
2. There are various label and label sleeve materials for portable printer, heat transfer printer and computer printer;
3. Suitable for printing longer characters;
4. And have the label size suitable for different applications.

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Radiation crosslinked cables and materials

1. development of crosslinking technology
In 1952, Charles by invented crosslinked polyethylene insulation by using radiation energy to trade polyethylene into polyethylene in a nuclear reactor test;
In 1957, Ge first made cross-linked ACSR Cable in cable industry by using peroxide (DCP) as chemical crosslinking reagent on the basis of the above principles;
In the late 1960s, Dow Corning invented silane crosslinking technology, and has developed to date

2. radiation crosslinking process of cable
There are three kinds of production processes: two-step one-step copolymerization and ethylene silane copolymerization.
The two-step technology is the first developed technology. The secondary method has less investment and low cost, but it is easy to bring impurities, so it can only be used in the manufacture of low-voltage cable. It has little requirements for equipment and can be completed on conventional extrusion equipment;
The one-step process of grafting reaction and adding condensation catalyst was combined to extrude the cable in one step to reduce the pollution opportunity of impurities, which is suitable for the manufacture of medium and low voltage power cables. But the technology is difficult, and it needs special extruder, and the investment is bigger than one-step;
In the copolymerization, silane copolymers are reacted in PE reactor, which improves the electrical insulation performance of crosslinked PE significantly, and is more suitable for medium and low voltage AAAC Cables besides the manufacture of low voltage cables. Reply to “cable”, and check for more related articles
3. requirements for materials of irradiation cable
Irradiation cable shall be processed three times
a) Material modification to get cable material
b) Cable sheath plastic
c) To withstand the attack of high energy particles
The environment of irradiation cable
High temperature, possibly oil pollution, other harsh environment

4. irradiation crosslinking of polymer materials
5. Application of irradiation crosslinking cable
Various connecting wires and installation wires commonly used in buildings are copper wires wrapped in insulation layer, which are used for low voltage electrical equipment and lighting devices. This wire is commonly known as “laying wires”.
Electrical installation line, but the application field of electrical installation line is more extensive, and the requirements for cables are different in different application occasions. In some cases, the diameter of the line is relatively thin, which belongs to the commonly known “electronic line”.
Radiation crosslinking cable is also needed in the lead-up flexible wire of motor winding
Car and locomotive lines
Marine and petroleum platform cables
Overhead insulated cable
Locomotive navigation aids light cable
New energy cable (photovoltaic, wind, charging pile)
Other special occasions (aerospace, nuclear)

6. Standard and quality control of irradiation crosslinking cable and materials
1. gel content
Gel content is an important index of cross-linking degree of surface materials. Generally, linear polymer materials can be dissolved in some solvents under certain conditions, but the crosslinked network structure is not soluble in any solvent. Based on this principle, gel content can be obtained. It is the most direct and simple method to characterize the degree of crosslinking of polymers. The cross linked polymer with known weight was put into Soxhlet extractor and refluxing with suitable solvent for a certain time. After being removed, the gel content was obtained by vacuum drying and weighing.
2. thermal extension
Although the gel indicates that the degree of crosslinking of polymers is more accurate, but the operation is rather cumbersome, it is often tested in the cable industry to determine the degree of cross-linking after the thermal elongation of the material coated by the radiation. After applying 0.2MPa tensile force at 200 ℃ for 15min, the elongation is less than 175%. After the sample is taken out of the heat aging box and cooled, the permanent thermal deformation is less than 15%, which means the cross-linking is qualified.
3. thermal aging
The temperature grades of crosslinked cable materials in JB / t10436-2004 are 90 ℃, 105 ℃, 125 ℃, 150 ℃, and the aging time is 168 hours, but the aging temperature is 121 ℃, 136 ℃, 158 ℃, 180 ℃ respectively

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What should be paid attention to when storing wire and cable reel?

Attention should be paid to the following points when storing and transporting wires and AAAC Cables on shelves:
1、 In storage, first of all, it is forbidden to contact with acidic, alkaline and corrosive substances and store them separately. Insulated wires and cables should be stored in a dry and ventilated warehouse. The suitable temperature in the warehouse is 5-30 degrees, and the relative humidity should not exceed 75%. The glass on the warehouse window should be painted with white paint to avoid direct sunlight and premature aging of insulation layer.

2、 There shall be no harmful gas that can damage the insulation layer or corrode the conductor metal around the wire and cable storage place.
3、 Avoid storage in open air to prevent accidental damage.
4、 Small quantities of wires can be stacked in the shelf, and the stack height should be 5-10 rolls. Large quantities of wires can be stacked into plum blossom style ventilated round stacks. Single core wire and cable can be appropriately high code; The stack height is 2 meters in spring and winter and 1.5 meters in summer and autumn. When stacking, the pallet should be padded with sleepers, and the sleepers should be paved with planks, and two layers of moisture-proof paper should be added, and good ventilation should be maintained. During the storage of wires and cables, they should be stacked once every three months, and the upper and lower layers should be replaced to prevent long-term compression and deformation of the lower layer. Always check whether the sealing package of wires and cables is intact during storage.
5、 The storage life of wires and ACSR Cables shall be subject to the date of production. Generally, the storage life shall not exceed one and a half years, and the longest shall not exceed two years. Pay attention to the change of temperature and humidity in the process of storage, and take cooling measures immediately if the temperature in the warehouse exceeds 30 ℃. If the relative humidity reaches 75% for 3 consecutive days, desiccant or other measures should be taken to absorb moisture.

6、 It is strictly forbidden to drop wires and cables from high places during transportation, so as to avoid cracking of insulation layer and sheath layer, damaging the electrical and mechanical properties of wires and cables.
7、 During hoisting operation, it is strictly forbidden to hoist multiple coils of wires and cables at the same time. On vehicles, ships and other means of transport, wires and cables must be laid flat and properly fixed to prevent collision or overturning and damage to the outer or internal structure of wires and cables.

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Technical requirements of explosion proof combined switch and cable in coal mine

Technical requirements of explosion-proof intelligent vacuum combined switch
1. certificate and certificate with relevant qualification.
2. inspection report of qualified unit inspection.
3. the switch shall be provided with coal safety mark and explosion-proof sign.
4. the switch has explosion-proof and explosion resistance.
5. the altitude is 2000 meters.
6. switch protection is sensitive and reliable, with high measurement accuracy and high anti-interference capability; It has overload, over-current, phase break or leakage blocking protection.
7. fully digital, LCD display, fault self diagnosis, memory function, fault simulation test, can be inquired and modified online, with event sequence record, communication transmission, remote operation of shearer or mining face scraper conveyor.
8. when the scraper conveyor of mining face stops running, the shearer must be locked.
9. there is program control on and off operation, and three machines are matched, and full automatic centralized control is implemented.
10. it can be used for the AC 50Hz, 1140V to 3300v power grid, and interface with other automation equipment or system in a centralized control, protection, monitoring and communication.

11. it can realize single machine control, multi loop program control, single machine double speed control and dual speed control.
12. the integrity standard of flameproof joint surface must meet the following table: ① when the diameter of the control rod is d < 6.0mm, l must not be greater than 6.0mm; When d < 25mm, l must be no less than D; d> At 25mm, l must not be greater than 25mm. ② The maximum unilateral clearance m between the shaft and the shaft hole of the rolling bearing structure shall not be greater than 2/3 of the W value.
13. the surface roughness of flameproof joint surface shall not be greater than 6.3; The surface roughness of the control lever shall not be greater than 3.2.
14. the defects of the flameproof joint surface or the raised parts on both sides of the mechanical scar higher than the surface without damage shall not exceed the following provisions after grinding:
③ The local sand holes with diameter no more than 1mm and depth no more than 2mm shall not exceed 5 for each 25px2 on the explosion-proof surface with width of 40, 25 and 15mm; The explosion-proof surface with a width of 10 mm shall not exceed 2. ④ The mechanical scars, width and depth shall not be greater than 0.5mm; The length shall ensure that the effective length of the remaining non injury flameproof surface is not less than 2/3 of the specified length.
15. the explosion-proof surface shall not be rusted or oil stained, and rust proof oil or phosphating shall be carried out. If there is rust, after wiping with cotton yarn, it is qualified to leave the traces of ferrous oxide in green brown color, and those who feel no sense by hand are qualified.
16. the bolt fixed flameproof joint surface shall be tightened to the extent that the flat spring washer is not loose and the clearance is not more than the specified.
17. observe the window hole with good sealing and transparency, without damage and crack.
18. screw explosion-proof structure: thread accuracy shall not be lower than grade 3; The pitch shall not be less than 0.7mm; The minimum number of thread engagement threads and the minimum screw in concentration meet the requirements.
19. the length of the diameter of the control rod and the flameproof joint surface must meet the requirements.
Technical requirements for mine cables
1. flame retardant shielded cable which has passed the inspection by qualified units and obtained safety signs of coal mine products must be selected.
2. qualified cable unit inspection and test report.
3. relevant certificates and certificates with qualification.
4. the number and section of cable cores shall be determined by the supporting manufacturers of three machines according to the power supply rules, and the length shall be determined according to the control location.
5. it is strictly forbidden to use aluminum clad cable and aluminum core cable.
6. aluminum core cable shall not be used for grounding.
7. rubber sleeve soft cable conforming to mt818 standard must be used for high and low voltage cables laid.
8. the number of cores of special control and communication cables shall be selected and reserved with a certain number of spare lines according to the actual requirements of communication, signal and control system.
9. the cable grounding core wire shall not be used for other purposes except for monitoring the grounding circuit.
10. according to the maximum working current actually passed by the cable, it shall not exceed the allowable current for the long time of the AAC Cable.

11. cable section shall be selected according to mechanical strength, and its core section shall not be less than the minimum section specified by various electrical equipment according to the mechanical strength requirements.
12. insulation shake test of cables of different voltage withstand grades must meet the insulation shake test standard.
13. the connection between ABC Cable and electrical equipment must be made with junction box consistent with the performance of electrical equipment. The cable core must be connected to the electrical equipment by means of a tooth shaped crimping plate (claw) or a nose.
14. rubber sleeve cables of different sections are strictly prohibited to be directly connected, and must be connected through the junction box, connector or bus box meeting the requirements.
15. the low-voltage rubber sleeve cable is connected with electrical equipment. The sealing ring is made of rubber with shore hardness of 45-55 degrees, and aging treatment shall be carried out according to the regulations, and it shall meet the requirements of intact.
16. the inlet and outlet nozzles are connected tightly. The fastening degree of fasteners after wiring is qualified that the crimp type nozzle is qualified to take the pulling cable without string operation, and the screw thread nozzle shall screw the compression nut into no more than half circle with five fingers of one hand. The flattening amount of the cable after pressing the cable with the pressure plate type nozzle shall not exceed 10% of the cable diameter.
17. the connection of cable core wire shall be crimped or welded, and binding is strictly prohibited. The joint resistance after connection shall not be greater than 1.1 times of the resistance of the same length of the core, and the tensile strength shall not be less than 80% of the original core.
18. when connecting the shielded cables, the shielding layer of the main wire core must be stripped.