Types of cables for photovoltaic power generation systems

Photovoltaic special cables, power cables, control cables, communication cables, radio frequency cables
Photovoltaic cable: PV1-F1*4mm2
The cable from the string to the combiner box is generally used: photovoltaic special cable PV1-F1*4mm2.
Features: The photovoltaic cable has a simple structure. The polyolefin insulation material used in it has excellent heat resistance, cold resistance, oil resistance, and ultraviolet resistance. It can be used under harsh environmental conditions and has a certain mechanical strength.
Laying: It can be protected through the pipe, and the component bracket is used as the channel and fixing of the cable laying to reduce the impact of environmental factors.
Power cable: ZRC-YJV22
Steel tape armored flame-retardant cross-linked cable ZRC-YJV22 is widely used in: combiner box to DC cabinet, DC cabinet to inverter, inverter to transformer, transformer to power distribution device, power distribution device to the power grid connecting cables.
The common nominal cross-sections of ZRC-YJV22 cables in photovoltaic power generation systems are: 2.5mm2, 4mm2, 6mm2, 10mm2, 16mm2, 25mm2, 35mm2, 50mm2, 70mm2, 95mm2, 120mm2, 150mm2, 185mm2, 240mm2, 300mm2.


Features:
(1) The texture is hard, the temperature resistance grade is 90°C, it is easy to use, has the characteristics of low dielectric loss, chemical corrosion resistance and no drop limit for laying.
(2) It has high mechanical strength, good resistance to environmental stress, good thermal aging performance and electrical performance.
Laying: It can be buried directly, suitable for fixed laying, and adapt to the needs of different laying environments (underground, water, trenches and tunnels).
Power cable: NH-VV
NH-VV copper core PVC insulated PVC sheathed fire-resistant power cable. Suitable for rated voltage 0.6/1KV.
Use characteristics: Long-term allowable working temperature is 80°C. Allowable bending radius during laying: single-core cables are not less than 20 times the cable outer diameter, and multi-core cables are not less than 12 times the cable outer diameter. When the cable is laid, the ambient temperature is not lower than 0 degrees Celsius, without pre-heating. The voltage laying is not limited by the drop.
Laying: Suitable for occasions with fire resistance requirements, and can be laid indoors, in tunnels and trenches. Note that it cannot withstand the action of external mechanical forces and can be directly buried in the ground.


Control cable: ZRC-KVVP
ZRC-KVVP copper core PVC insulated PVC sheathed braided shielded control cable. It is suitable for the control, monitoring circuit and protection circuit of AC rated voltage 450/750V and below.
Features: Long-term allowable use temperature is 70℃. The minimum bending radius is not less than 6 times the outer diameter.
Laying: Generally, it is laid indoors, cable trenches, pipes and other fixed places that require shielding and flame retardancy.
Communication cable: DJYVRP2-22
DJYVRP2-22 polyethylene insulated PVC sheathed copper wire braided shielded armored computer special soft cable is suitable for electronic computers and automation connection cables with high requirements for interference prevention at rated voltages of 500V and below.
Features: DJYVRP2-22 cable has the characteristics of oxidation resistance, high insulation resistance, good withstand voltage, and low dielectric coefficient. While ensuring the service life, it can also reduce the crosstalk and external interference between circuits, and the signal transmission quality is high. The minimum bending radius is not less than 12 times the cable outer diameter.
Laying: The cable is allowed to be fixedly laid and used under the ambient temperature of -40℃~50℃. Laying indoors, cable trenches, pipelines and other places that require electrostatic shielding.
Communication cable: RVVP
Copper core PVC insulated PVC sheathed insulated and shielded flexible cable RVVP, also known as electrical connection anti-interference flexible cable, is a communication cable suitable for anti-interference, safe and efficient data transmission, such as alarms and security.
Features: Rated working voltage 3.6/6KV, long-term working temperature of the cable conductor is 90℃, and the minimum allowable bending radius is 6 times the outer diameter of the cable. It is mainly used as a communication cable to play a role in anti-interference. Laying: The RVVP cable should not be exposed to sunlight, and the bottom core must be well grounded. The weak current circuit communication cables that need to suppress the intensity of electrical interference should be laid in steel pipes and boxes. When laying parallel to the power cable, the distance should be kept away as far as possible.
RF cable: SYV
Solid PE insulated and PVC sheathed radio frequency coaxial cable SYV.
Features: The commonly used video cables in monitoring are mainly SYV75-3 and SYV75-5. If you want to transmit video signals within 200 meters, you can use SYV75-3, and if you want to transmit video signals within 350 meters, you can use SYV75-5.
Laying: It can be laid through a pipe.

Small difference between overhead cable and fiber optic cable

Overhead cable: When the phone converts the acoustic signal into an electrical signal and then transmits it to the switch via the line, the switch transmits the electrical signal directly to the other phone via the line for answering. The transmission line during this conversation is the cable. The main part of the cable is copper core wire. The single core wire diameters are divided into 0.32mm, 0.4mm and 0.5mm. The larger the diameter, the stronger the communication capability; and according to the number of core wires, there are: 5 pairs, 10 pairs, 20 pairs, 50 pairs, 100 pairs, 200 Yes, wait, the logarithm mentioned here refers to the maximum number of users that the cable can accommodate; it is also divided by package.
Optical fiber cable: It is large in size, weight, and poor in communication ability, so it can only be used for short-distance communication. Optical cable: When the phone converts the acoustic signal into an electrical signal and then transmits it to the switch via the line, the switch transmits the electrical signal to the photoelectric conversion device (converts the electrical signal into an optical signal) and transmits it to another photoelectric conversion device via the line ( Convert optical signals into electrical signals), and then to the switching equipment, to another phone to answer. The line between the two photoelectric conversion devices is an optical cable. Gu said that it is only divided by the number of core wires, the number of core wires: 4, 6, 8, 12 pairs and so on.


Optical cable: It has the advantages of small size, weight, low cost, large communication capacity, and strong communication capability. Due to many factors, it is currently only used for long-distance and point-to-point (ie, two switch rooms) communication transmission. Their difference: the inside of the cable is copper core wire; the inside of the optical cable is glass fiber. Optical fiber communication optical cable is a kind of communication line in which a certain number of optical fibers form a cable core in a certain way, and are covered with a sheath, and some are also covered with an outer sheath to realize the transmission of optical signals. Field tests have been carried out successively in Shanghai, Beijing, Wuhan and other places. Soon after, it was tried out as an intermediate trunk in the local telephone network. After 1984, it was gradually used for long-distance lines, and single-mode fiber was adopted. Communication optical cables have greater transmission capacity than copper cables, with long relay sections, small size, light weight, and no electromagnetic interference. Since 1976, they have developed long-distance trunk lines, intra-city relays, offshore and transoceanic submarine communications. , As well as the backbone of wired transmission lines such as local area networks and private networks, and began to develop into the field of user loop distribution networks in the city, providing transmission lines for fiber-to-the-home and broadband integrated service digital networks. The cable is usually a rope-like cable that is twisted by several or several groups of wires (at least two in each group). Each group of wires is insulated from each other and is often twisted around a center. The entire outer bread has a height. Insulating coating; especially the submarine cable first: there is a difference in material. Cables use metal materials (mostly copper and aluminum) as conductors; optical cables use glass fibers as conductors. Second: There is a difference in the transmission signal. The cable transmits electrical signals. Optical cables transmit optical signals. Third: There are differences in the scope of application. Cables are now mostly used for energy transmission and low-end data information transmission (such as telephone). Optical cables are mostly used for data transmission.

What is a photovoltaic cable?

The construction of cost-effective and profitable photovoltaic power plants represents the most important goal and core competitiveness of all solar manufacturers. In fact, profitability depends not only on the efficiency or high performance of the solar modules themselves, but also on a series of components that seem to have no direct relationship with the modules. For example, if the photovoltaic power station fails to use suitable cables, it will affect the service life of the entire system. So, what is a photovoltaic cable?
Photovoltaic cable is an electron beam cross-linked cable with a rated temperature of 120°C, which is equivalent to 18 years of use under continuous temperature conditions of 90°C; and when the temperature is lower than 90°C, its use Longer life.
The characteristics of photovoltaic cables are determined by their special insulation materials and sheath materials, which are called cross-linked PE. After being irradiated by an irradiation accelerator, the molecular structure of the cable material will change, thereby providing its various performances. During installation and maintenance, the cables can be routed on the sharp edges of the roof structure. At the same time, the cables must withstand pressure, bending, tension, cross tensile loads and strong impacts. If the cable sheath is not strong enough, the cable insulation layer will be severely damaged, which will affect the service life of the entire cable, or cause short-circuit, fire, and personal injury hazards.
Photovoltaic cable selection


The cables used in the low-voltage DC transmission part of the solar photovoltaic power generation system have different requirements for the connection of different components due to different use environments and technical requirements. The overall factors to be considered are: the insulation performance of the cable, the heat-resistant and flame-retardant performance, Engage in aging performance and wire diameter specifications. Specific requirements are as follows:
1. The connecting cable between the solar cell module and the module is generally connected directly with the connecting cable attached to the module junction box. When the length is not enough, a special extension cable can also be used. Depending on the power of the components, this type of connecting cable has three specifications with a cross-sectional area of ​​2.5m㎡, 4.0m㎡, and 6.0m㎡. This type of connecting cable uses a double-layer insulation sheath, which has superior resistance to ultraviolet rays, water, ozone, acid, and salt, as well as superior all-weather capability and abrasion resistance.
2. The connecting cable between the battery and the inverter requires the use of a multi-strand flexible wire that has passed the UL test, and it should be connected as close as possible. Choosing a short and thick cable can reduce the loss of the system, improve efficiency, and enhance reliability.
3. The connecting cables between the battery square array and the controller or DC junction box also require the use of multi-strand flexible wires that have passed the UL test. The cross-sectional area specification is determined by the maximum current output of the square array.
The cross-sectional area of ​​the DC cable of each part is determined according to the following principles: The connecting cable between the solar cell module and the module, the connecting cable between the battery and the battery, and the connecting cable of the AC load. Generally, the rated current of the selected cable is the maximum continuous operation of each cable 1.25 times the current; the connecting cable between the solar cell array and the array, the connecting cable between the battery (group) and the inverter, the cable rated current is generally 1.5 times the maximum continuous working current in each cable.

Production of cables without production license is punished

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.

Precautions for household wire installation

In home decoration, circuit engineering is the most important, and home circuit belongs to concealed engineering, which is related to people’s quality of life and living standard in the future. Therefore, we must pay attention to circuit problems in decoration to avoid potential safety hazards. Next, Guoyou AAC Cable will share the relevant knowledge of family wire laying to protect the safety of family electricity.

1、 Flame retardant wires shall be selected
In modern families, there are too many household appliances and heavy wire load, which is easy to cause fire accidents. In these aspects, flame retardant wires can meet the power demand of families. At the same time, in case of fire hazard, flame retardant wires can effectively control the spread speed of fire, avoid greater losses caused by the fire of combustibles around wires, and strive for more time for people to evacuate from the fire site to minimize the loss of fire injury.

2、 Use wires of different colors
Color classification shall be done well when laying family lines, and it is more convenient for later maintenance. According to national regulations, red, yellow and green represent live wire, light blue is used for zero wire, and yellow and green are used for ground wire. In future maintenance, electricians can distinguish live wire and zero wire through the color of wires, which is convenient for construction and is also very important for household electricity.
3、 Wire laying and pipe sleeve
According to the ACSR Cables laying regulations, the wire must be protected by insulating sleeve during the laying process, and the joint shall not be exposed. Some irresponsible construction teams will directly bury the wires in the wall without casing protection. This treatment leads to the exposed wire joints, which are easy to be damaged by external forces, so as to reduce the service life of the wires and bury potential safety hazards for people’s life.

Unqualified ABC Cables laying will not only affect our use, but also directly affect our life safety. Choosing a high-quality wire product can reduce the risk from the source. Guoyou high-end wire has excellent performance in high temperature resistance, moisture resistance, durability, energy saving and environmental protection, which is different from ordinary household wires, With professional environmental protection and flame retardancy, consumers are more safe and assured to use. The above is the relevant knowledge of family wire laying. I hope it will be helpful to you

Cable threading, tips you don’t know!

In the wiring of weak current projects, we usually bury the wire tube in the wall first. Such a hidden design will not affect the beautiful effect of decoration. However, after the AAAC Cables tube is buried, threading from the inside is a troublesome thing. Sometimes we can’t wear a wire after tossing for a long time. What should we do at this time?

In fact, the reason is that we don’t use the right way to thread wires. Let’s introduce a new way to thread wires. It’s so fast and professional for wires to go through pipes. Teachers and Fu all install it like this. It’s too smart!
01
What’s good for threading wires
The traditional wire threading method is generally to put a small steel wire in the wire pipe, then bend the steel wire to buckle the outer edge of the pipe, tie the wire to one end of the steel wire, pull the steel ACSR Cables on the other side, and then slowly pull the wire out of the pipe, but this construction method tests patience. Moreover, it will greatly increase the decoration time, and the operation is also more troublesome. If you meet a corner, sometimes it takes half a day to get the line out. So now more and more people are not using this method.
However, with the development of technology, some tools in decoration are constantly updated, so now smart masters no longer use steel wire rope, but use this, which can thread quickly without jamming. Now the outer skin of professional threading device is made of steel wire wrapped rubber, which has good hardness and smoothness. It is much stronger than the previous steel wire rope, and it is not easy to jam at the elbow. In particular, a pulley is installed at the thread feeding head, which is very popular with teachers.
This threading device is also very simple in operation. It can be used for the first time. Use the traction head of the wire to pass through the wire head, and then fix it with a professional tensioner. This kind of tightener not only has good fixing effect, but also is convenient for construction, which saves the threading time of the master. After the thread head passes through the tightener, wrap it into an 8-shaped shape, and then push it up with the fastening spring. It is not too convenient. This is why more and more masters like to use the tightener instead of the steel wire rope.

02
Let’s introduce several standard threading methods
1. The first is that some wires will be long, or when it is necessary to turn and wind in the actual environment, talc powder can be added to the pipe to facilitate the extraction of wires. Remove a little of the insulation material in the front section of the wire, and then slowly fix the wire core in the coil.
2. The more important point is: wires with different voltages and different circuits must not be threaded in the same conduit. In addition, if the circuits of multiple lamps will not interfere with each other, remember not to thread too much.
3. After the wires are strung, remember to cut off the wires. If you want to connect the blood to the switches, sockets and junction boxes, we remember to reserve more than 15 cm. In addition, more than half of the perimeter of the distribution box should be left in the distribution box. Oh, the wires outside the door should be left about one and a half meters.
03
Wire threading cannot be carried out casually, and the following points shall be ensured
1. Be sure to select wires with good quality and large wire diameter. The threading pipe shall be flame-retardant PVC pipe. When purchasing, you can pinch it with your fingers. If it can’t be broken, it means that the quality is very good. If the economy permits, special galvanized pipe can also be selected.
2. In the same conduit, the number of wires passing through shall not be too much, and it shall be easy to pull. The popular standard is that the total cross-sectional area of the wires in the pipe shall not be greater than% of the total cross-sectional area of the inner diameter of the pipe, and shall not exceed


3. The inner wire shall be free of joints and kinks. The pipe sleeve shall be used when the pipeline is butted, the bend shall be connected with elbow or tee, and then glued with glue. The presser foot cap shall be used when connecting to the wire box, and the lock interface must be used between the wire pipe and the wire box.
4. High power electrical appliances such as floor heating and air conditioning should be wired separately, and electrical appliances such as refrigerators that are not suitable for frequent power cuts should also be wired separately. These electrical appliances should have separate switches at the main switch (air switch). If you go far away, you can turn off other power supplies, leaving only the refrigerator power on.
5. After the wire passes through the pipe, it is put into the slot and fixed with cement or quick drying powder, that is, several points are selected on a slot for sealing and fixing. When installing the cassette, the wall hole where the cassette is placed should be larger. Cement can be embedded in the gap between the cassette and the wall hole to fix the cassette firmly to prevent loosening in the future.
6. After the wiring is completed, the decoration company must leave a detailed “pipeline diagram”, number the wall, draw the direction and specific position of the wire with a pen, indicate the size from the upper floor to the lower floor and adjacent wall, especially the joint position of the pipeline. With such a detailed, it will be much more convenient to overhaul the ABC Cables in the future.
From the above points, we can know that it is necessary for wires to go through pipes in the process of decorating circuits. Now experienced masters will choose new types of threading appliances for wire threading. It is fast and professional to wear wires with it. Friends who like it might as well try it.

How many rumors do you know about wires and cables?

The rapid development of the Internet age has not only brought convenience to everyone’s life, but also brought new challenges to our social management. In particular, we have seen the rapid spread of rumors. I believe you can distinguish many rumors, but how many rumors about wires and AAAC Cables have you heard? Can you identify it in time?


If the square of the wire is not enough, it will not be qualified?
not always! For many people, this is already a “common sense” existence, but is this really the case? With the improvement of conductor material production process and scientific and technological progress, the advanced production process of oxygen free copper has been widely used. The resistivity of copper conductor material is enough to ensure that the copper wire less than the nominal diameter can meet the requirements of DC resistance of corresponding specifications, while the conductor of wire and cable has strict requirements on the resistivity of conductor, for example, The DC resistance of 25 mm2 copper core conductor specified in the standard at 20 ° is not greater than 0.727 Ω / km (the second stranded conductor), so the conductor is qualified as long as it is not greater than this value.
Flame retardant ABC Cables will not burn?
wrong! Flame retardant of flame-retardant wire and cable refers to that when a wire and cable fire accident occurs, it can block and delay the diffusion and spread of flame along the wire and cable, and minimize the expansion of fire range of wire and cable. This type of cable has the characteristics of self extinguishing after fire. Fire resistant wire and cable refers to that in the case of wire and cable fire accident, the wire and cable product can adhere to the normal operation for a certain time under the condition that the external flame is still burning, maintain the integrity of wire and cable lines and maintain the normal operation of line equipment.
Will wires and cables have radiation?
Wires and cables do have radiation. However, the fact is that all live things have radiation. For example, 220V wires also have radiation, but the radiation is very small and basically negligible. Moreover, the radiation of wires is much lower than that of mobile phones. If you are really afraid of wire radiation, it is recommended to throw away the mobile phones first. If you are afraid of the magnetic field generated by wires and cables and think that the magnetic field will cause any harm to the human body, the geomagnetic field is even more terrible. Therefore, I think that “radiation from wires will damage health” is just groundless, and I think too much.


The thicker the cable insulation, the better?
No, too thick cable insulation will increase the difficulty of AAC Cable laying. At present, cable laying is mainly bridge or through pipe. Now many enterprises are implementing cable requirements, with tight cable requirements and small outer diameter. There can be gaps in the laying process to emit heat energy to ensure that the outer sheath of the cable is not damaged. Otherwise, it will bring some difficulties to the construction unit and cable laying. In summer, the working temperature will rise, and these temperatures will be emitted through the outer protective layer. The thickness of the sheath increases, and the heat energy is difficult to be emitted, which will affect the service life of the cable. Due to the thermal action of PVC, a series of physical and chemical changes will occur in the insulating layer, losing the original excellent performance, resulting in obvious decline in the insulating performance and even short circuit, Therefore, when selecting the cable, the thickness of the cable must be moderate.
The laying of water and electricity shall be horizontal and vertical
unnecessary! Although the water and electricity wires laid horizontally and vertically look very good, there are really many hidden dangers! Firstly, the material cost of the wire pipe is much higher than that of other laying methods. Secondly, because it is 90 degrees horizontally and vertically, it is easy to get stuck when threading the wire in the later stage! So as long as it complies with the specifications, how convenient it is to lay it!


In addition to the above, there are numerous rumors about wires and cables: wires and cables are cheap, so selling cables makes a lot of money; Wires of the same quality can certainly be bought at a cheaper price; The copper conductor used in wires and cables is not so high; Wires and cables will leak electricity in rainy days, which is unsafe.
Although some are rumors, it’s not too much to say that wires and cables are lifelines. We should be more careful when buying. Only by selecting manufacturers, products and national standard products can we use them at ease.

How to prevent cable from fire due to conductor overload

During the operation of wires and AAC Cables, they will heat due to the existence of resistance. The resistance of the conductor is generally very small, and its heating power can be expressed by the formula q = I ^ 2R. Q = I ^ 2R shows that for a section of conductor in actual use (r has been basically constant), the greater the current passing through the conductor, the greater the heating power; If the electric flow is constant, the heating power of the conductor is also constant. The heat released during operation will be absorbed by the conductor itself, resulting in the increase of conductor temperature. Although the conductor keeps absorbing the heat released by current work during operation, its temperature will not rise indefinitely. Because the conductor is absorbing heat and constantly releasing heat to the outside world, the facts show that the temperature rises gradually after the conductor is powered on, and finally the temperature is constant at a certain point. At this constant point, the heat absorption and release power of the conductor are the same, and the conductor is in thermal equilibrium. The ability of conductor to withstand high temperature operation is limited, and operation beyond a certain maximum temperature will be dangerous. This maximum temperature naturally corresponds to a maximum current. If the conductor exceeds this maximum current, it is overload. The overload of the conductor directly leads to the temperature rise of the conductor itself and its nearby articles. Temperature rise is the most direct cause of this kind of fire.


Overload destroys the insulation layer between double stranded conductors, causing short circuit, burning equipment and fire. The double strand conductors are separated by the insulating layer between them. Overload softens and destroys the insulating layer, resulting in direct contact between the two strands of conductors, causing short circuit and burning the equipment. At the same time, the high temperature generated by large current at the moment of short circuit causes the line to catch fire and fuse, and the generated molten beads fall to combustibles to cause fire. Overload temperature rise can also directly ignite nearby combustibles. The heat transfer of overload conductor increases the temperature of nearby combustibles. For combustibles with low ignition point nearby, it is possible to ignite them and cause a fire. This danger is particularly prominent in warehouses for storing inflammables and buildings with easy and combustible decoration.
Overload also puts the connection in the line under overheated conditions, which accelerates its oxidation process. Oxidation causes a thin layer of oxide film that is not easy to conduct electricity at the connection point. The oxide film increases the resistance between the contact points, resulting in ignition and other phenomena, resulting in fire.
So, how to prevent fire caused by overload of wires and ACAR Cables?
1. In the process of line design, the capacity of the site shall be accurately verified, the possibility of new capacity in the future shall be fully considered, and the appropriate type of conductor shall be selected. For large capacity, thicker conductor shall be selected. Line design and reasonable type selection are the key steps to prevent overload. If the design and selection are improper, it will leave congenital hidden dangers that are difficult to rectify. Some small projects and places are not carefully designed and selected. It is very dangerous to choose and lay lines at will. The bearing capacity of the original line shall be fully considered for new electrical appliances and electrical equipment. If the original line does not meet the requirements, it should be redesigned and reconstructed.


2. The line shall be laid by qualified electricians in accordance with relevant specifications. The laying conditions of the line directly affect the heat dissipation of the conductor. Generally speaking, the line laying shall not pass through inflammable and combustible materials and stacking, which will lead to poor heat dissipation of the conductor, heat accumulation, the possibility of igniting the surrounding combustible materials, and increase the risk of fire under overload; The lines laid in the decoration ceiling of public entertainment places shall be protected by steel pipes to separate the ceiling from the line. Even if there are molten beads under overload, short circuit and other conditions, they will not fall, so as to avoid fire.
3. Strengthen power management, avoid random wiring and grounding, and use mobile sockets carefully. Random ACSR Cables, random grounding and the use of mobile sockets are actually adding electrical equipment to a certain section of the line, increasing the amount of current, which may cause overload. The jack of mobile socket is obviously more than the fixed socket on the wall. If too many electrical equipment are used on the mobile socket, the original line must be difficult to bear. For high-power equipment and electrical appliances, separate lines should be set, and mobile sockets should not be used as wiring sources.


4. Speed up the renewal and transformation of old lines and eliminate potential fire hazards. Due to the long service life of old enterprises, old residential areas and other units, many lines have aged and exceeded the service life. Even if the current carrying capacity of some lines is small, it is difficult for aging lines to bear such current carrying capacity, and it also has the risk of overload. Especially in the old residential areas, the lines have long been aging, but with the improvement of people’s living standards and the increase of household appliances, their power consumption is still increasing year by year, which is really worse. For old lines, timely supervision and coordination shall be carried out to promote their rectification as soon as possible, so as to eliminate potential fire hazards and ensure safety.

How to determine whether to use 6 / 10 or 8.7/10 for cable selection

When selecting cables, the power cable line design, installation and operation departments shall consider four factors, such as cable service conditions, insulation level, AAAC Cable type and conductor section, which are divided as follows.
1. Cable service conditions
(1) cable rated voltage / u () shall meet the following requirements:
1) the voltage shall meet the requirements of neutral grounding mode of power system, that is, in the neutral ungrounded power system, the voltage of non fault phase increases by times in case of single-phase grounding fault, which is related to the troubleshooting time of system grounding fault.


In IEC standard, power system is divided into three categories. Class a means that any phase conductor of the system is grounded and can be separated from the system within lmin; Class B refers to the grounding of single-phase conductor in the system, the allowable grounding fault time shall not exceed 8h, and the annual cumulative time shall not exceed 125h; Class C is a system that does not belong to classes a and B.
when the cable is used in the neutral effective grounding system, u takes the phase voltage value of the system. For example, 6 / 10kV cable is selected for 10kV system and 21 / 35kV Cable is selected for 35kV system.
When the cable is used for neutral non effective grounding system, the cable with one level higher than the system phase voltage shall be selected. For example, 8.7/10kv cable shall be selected for 10kV system and 26 / 35kV Cable shall be selected for 35kV system.
When the cable is used in class C system and single-phase grounding is allowed for long-term operation, u shall select the line voltage of the system, such as 6 / 6kV cable in 6kV system.
2) the voltage U and shall be equal to or greater than the rated voltage and maximum working voltage of the system where the ACSR Cable is located.
(2) cable transmission capacity. The cable line must meet the transmission capacity of the power system, that is, the selected cable shall have long-term allowable current carrying capacity to meet the system requirements.
For longer cable lines, the line voltage drop of the cable shall also be considered.
(3) cable laying conditions. Cables shall adapt to different laying methods, arrangement methods, metal sheath grounding methods and surrounding medium temperature, etc. The conductor of XLPE cable used for underwater laying shall have longitudinal water resistance. In order to meet the requirements of various laying environments, such as tension, compression, fire prevention, termite prevention and rodent prevention, the armor layer and outer sheath of the cable shall be made of corresponding structural materials.


2. Basic insulation level of cable
the peak value of lightning impulse withstand voltage between each conductor of the cable and the shield or metal sheath, i.e. the basic insulation level bil, shall comply with the provisions in table 1-13.
picture
in table 1-13, the lightning impulse withstand voltage of 220kV and above cable lines has two values, which can be selected according to the protection characteristics of arrester, the characteristic length of impulse wave of cable line and the lightning impulse insulation level of connected equipment.
3. Cable type
(1) comparison of insulation properties between XLPE and oil paper cables. XLPE insulated cable has the advantages of simple production process, short manufacturing cycle, easy installation and maintenance, excellent electrical performance and large transmission capacity. In recent 30 years, the technology of XLPE insulated cable has developed very fast and has been widely used. In terms of insulation performance, compared with oil paper insulation, cross-linked polyethylene insulation has some different characteristics, which are listed in table 1-14.
picture
Note: “air raid” should be “gap”
Oil paper insulated cable has the advantages of excellent electrical performance and long service life. It can be used in general occasions. However, compared with XLPE cable, the manufacturing and installation process of oil paper ABC Cable is more complex and the cost is higher.
oil filled cable with paper plastic composite insulation with low dielectric loss and alkylbenzene synthetic oil with good aging resistance as insulation structure, suitable for voltage levels of 220kV and above. In addition, oil paper insulated cables are also suitable for HVDC transmission lines.
(2) for cable lines of 110kV and below, XLPE insulated cable is generally the preferred variety. For distribution cables of 1kV and below, in addition to polyvinyl chloride (PVC) insulated cables for lines with light load, cross-linked polyethylene insulated cables shall also be selected.
Note: at present, 1-500 cables are mainly XLPE cables, and only some stocks of oil paper insulated cables and oil filled cables are left.


(3) ethylene propylene rubber (EPR) insulated cable is suitable for 35kV and below lines. This kind of cable is suitable for underwater laying because of its good moisture resistance, but its price is expensive.
4. Conductor section
copper conductors are generally used for power cables. The selection of conductor section shall meet the requirements of cable line transmission capacity and maximum short-circuit thermal stability of the system at the same time. And comply with “economic optimization of cable conductor size”.
in urban low-voltage power grid, four core cable is generally used, that is, in addition to three-phase conductor, there is a neutral line passing through three-phase unbalanced current and having protective grounding effect. The section of neutral wire shall generally be 30% ~ 60% of the conductor section of each phase. In the low-voltage power grid with large three-phase unbalanced current, four core low-voltage cables with equal cross-section shall be selected. The three core cable plus another insulated conductor cannot be used as the neutral wire to connect to the three-phase four wire low-voltage power grid, because in this way, there will be unbalanced current passing through the metal sheath and armor layer of the three core cable to heat it, thus affecting the transmission capacity of the cable.

Matters needing attention during wire and cable stranding

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.