What is power cables overload?

During the operation of the wire and cable, heat will be generated due to the existence of resistance. The resistance of the wire is generally very small, and its heating power can be expressed by the formula q=I^2R. q=I^2R indicates: for a piece of Power Cable in actual use (R is basically constant), the larger the current through the wire, the greater the heating power; if the amount of current is constant, the heating power of the wire is also constant . The heat released during operation will be absorbed by the wire itself and cause the temperature of the wire to rise. Although the wire is constantly absorbing the heat released by current work, its temperature will not rise indefinitely. Because the wire is absorbing heat, it is also constantly releasing heat to the outside world. The facts show that the temperature of the wire gradually rises after the wire is energized, and finally the temperature is constant at a certain point. At this constant point, the wire has the same heat absorption and heat dissipation power, and the wire is in a thermal equilibrium state. The ability of the wire to withstand higher temperature operation is limited, and operation exceeding a certain maximum temperature will be dangerous. This maximum temperature naturally corresponds to a certain maximum current, and running a wire that exceeds this maximum current is an overload. The overload of the wire directly causes the temperature of the wire itself and nearby objects to rise. The increase in temperature is the most direct cause of this type of fire.

Overload damages the insulation layer between the twin Overhead Cable and causes a short circuit, which burns down the equipment and causes a fire. The double-stranded wires are separated by the insulating layer between them, and overload causes the insulating layer to be softened and destroyed, which leads to direct contact between the two wires to cause a short circuit and burn the equipment. At the same time, the high temperature generated by the large current at the moment of short-circuit causes the line to catch fire and fuse, and the resulting molten beads fall to combustibles and cause fire. Overload temperature rise can also directly ignite nearby combustibles. The heat transfer of the overload wire increases the temperature of nearby combustibles. For nearby combustibles with low ignition point, it is possible to ignite them and cause a fire. This danger is particularly prominent in warehouses that store flammable materials and buildings that are easy to use and combustible decorations.

There are so many types of cables, how can I remember them?

Each industry has skills and shortcuts for each industry, so in the wire and cable industry, how to remember the problem of cable models is a skill of the industry. Only those who are knowledgeable can remember, and those who don’t understand can learn and understand.
There are many specifications and models of power cables, and they are also very complicated. To be honest, you brought an unusual model, and I don’t know it. Therefore, this article mainly introduces: the composition law of cable specifications. Once you have mastered this law, even if you see something you don’t know, you can know what kind of cable it is and what materials it consists of as long as you find the meaning of the corresponding letter or number.

We often put the specifications and models together. In fact, these two are different categories. You can see from your company’s certificate that the specifications, models, and rated voltages are written separately.
Specification is the main material composition of the cable. Different materials are suitable for use in different places, and different specifications have different uses. Our common cable specifications are VV, YJV, NH-YJV, YJLV, etc. Each letter and number in it has a different meaning.
Common insulating materials are: V (polyvinyl chloride), YJ (cross-linked polyethylene)
Conductor: T (copper, generally omitted and not written), L (aluminum), HL (aluminum alloy)
Common outer sheath materials are: V (polyvinyl chloride), Y (polyethylene)
The armor layer is represented by numbers: 22 (double steel belt wrapping), 32 (thin round steel wire)
Some cables need special properties: NH (fire-resistant), ZR (flame-retardant)
The above is the composition rule of the specification, namely: (special performance)-insulation-conductor-outer sheath-armor layer. For example, NH-YJV is a fire-resistant XLPE insulated PVC sheathed copper core cable; ZR-YJLV is a flame-retardant XLPE insulated PVC sheathed aluminum core cable; WDZ-YJV22 is a low-smoke, halogen-free Type XLPE insulated PVC sheathed copper core cable.

Another category is the intuitive cable model. The cable model indicates the number and size of the neutral wires of the main line. There are 3 grades, 4 grades, 5 grades, 3+1, 3+2, 4+1, etc. 3×4 means three 4mm2 cables; 3×120+1×70 means three 120mm2 main wires and a 70mm2 four-core cable.
There is nothing to elaborate on the model, you just need to remember one point: According to the GB/T standard, the main line of the cable is generally not less than twice the zero line (except for aluminum alloy cables), and only two are special, namely: 35mm2 The main line adds a 16mm2 zero line, and the 150mm2 main line adds a 70mm2 zero line.

Factors affecting service life of cable

Wire and cable as the domestic manufacturing industry second only to automobile manufacturing, it can be said that Aluminum Cable is closely related to our lives, has long been unable to separate, we all know that Chinese electric power penetration is very high, even better than many developed countries. Nowadays, all walks of life can not live without power, and the cable responsible for transmitting power is becoming more and more important.

Many people are concerned about the service life and safety of the Service Drop Cable. The service life of the cable is determined by the oxidation induction period of the sheath material, the average cable design is 20 years old, but many factors can accelerate cable aging, so keep these factors in mind for better cable maintenance.

1. External Force damage this is one of the most common causes of cable aging, such as: Cable installation is not standard construction, easy to cause mechanical damage.Sometimes if the damage is not serious, it will take months or even years to cause complete breakdown of the damaged parts to form a fault, sometimes serious damage may occur short-circuit fault, directly affect the safety of electricity and production.

2. Moisture in the insulation is also common, such as cable joints, such as poor cable quality, such as wet environment, may accelerate cable aging.

3. chemical corrosion severe cable aging due to long term overload operation, due to Joule’s laws load current flowing through the cable will inevitably lead to conductor heating, at the same time, the additional heat will be produced by the skin effect of electric charge, the eddy current loss of steel plate and the dielectric loss of insulation, which will increase the temperature of cable. Long-term overload operation, too high temperature will accelerate the aging of insulation, insulation is breakdown. Especially in the hot summer, the cable temperature often leads to the first breakdown of the weak insulation, so in the summer, the cable fault is particularly.

Ingenious use of aluminum alloy cables for photovoltaic systems(2)

In the era of low-cost Internet access, the cost of the control system is critical. In the past ten years, the prices of modules and inverters have fallen by 90%, which has contributed greatly to the overall cost reduction of photovoltaic systems, but the cost of cables has not been reduced. In large-scale projects, cables account for 10% of the system, which is even higher than that of inverters. In fact, as long as the design and installation are proper, under the premise of ensuring the normal operation and safety of the system, some AC cables are made of aluminum alloy cables, which can reduce part of the cost.
Rare earth aluminum alloy cable uses high elongation aluminum alloy material. By adding boron and other rare earth trace element materials to pure aluminum, and processed by rolling technology and special annealing process, the cable has good flexibility. When the surface is in contact with air, a thin and strong oxide layer can be formed, which can withstand various corrosions. Even when overloaded or overheated for a long time, the stability of the connection can be guaranteed, and the cost is slightly higher than that of ordinary aluminum alloy cables by about 10%.
The application range of aluminum cables: long-distance overhead lines, underground cable trenches with a relatively large space, and places with reliable fixed bridges, aluminum cables may be considered.

Precautions for the use of aluminum cables:
The melting point of copper is 1080°C, while the melting point of aluminum and aluminum alloy is 660°C, so copper conductors are a better choice for fire-resistant cables. Now some aluminum alloy 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 in this respect. No matter what kind of heat insulation measures the cable adopts, the cable will melt in a short time and lose its conductive function. Therefore, aluminum alloy is not suitable for fire-resistant cable conductors, nor is it suitable for use in densely populated urban distribution networks, buildings, factories and mines.

Compared with the aluminum core cable, the copper core is flexible, the allowable bend radius is small, and it is not easy to break after repeated bending. Therefore, the aluminum cable is not suitable for the occasions with many turns, more pipes, or complicated lines.
Since the terminals of the electrical switch equipment are all made of copper, the copper and aluminum are directly connected, and the chemical reaction of the galvanic battery will occur after power on: the more active aluminum will accelerate the oxidation, resulting in higher resistance at the joints and current carrying capacity. Therefore, some measures need to be taken when the copper and aluminum are connected, such as the use of copper-aluminum transition terminals or copper-aluminum transition terminals to eliminate electrochemical reactions.

Ingenious use of AAAC Conductors for photovoltaic systems(1)

In the era of low-cost Internet access, the cost of the control system is critical. In the past ten years, the prices of modules and inverters have fallen by 90%, which has contributed greatly to the overall cost reduction of photovoltaic systems, but the cost of cables has not been reduced. In large-scale projects, cables account for 10% of the system, which is even higher than that of inverters. In fact, as long as the design and installation are proper, under the premise of ensuring the normal operation and safety of the system, some AC cables are made of aluminum alloy cables, which can reduce part of the cost.

The cables of the power station are divided into DC cables and AC cables. Among them, the DC cables between the components and the DC cables between the components and the inverter are generally required to use photovoltaic special DC cables, and from the inverter to the AC distribution There is no requirement for cables between electric cabinets and cables between distribution cabinets and transformers.
What is aluminum alloy cable: Aluminum alloy cconductor is a new material power cable with AA8030 series aluminum alloy material as the 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 the aluminum alloy conductor of the same length is only half of that of copper.
In terms of service life: after the metal surface reacts with oxygen, different metal oxides are formed. Aluminum oxide can form a dense surface protective film with a certain hardness. Copper oxide, commonly known as patina, is between the above two and is a toxic substance.

The cost of aluminum alloy cable is about 25% to 50% of that of copper core cable, and the cost advantage of using aaac 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 cables are required for each phase. 150 square meters, 3 phases need 6 pieces, the total length is 9000 meters, the price is 864,000; if you use aluminum alloy with two 240 square meters, the total length is also 9,000 meters, the price is 450,000, you can save 414,000 yuan, and 240 A square aluminum wire has lower loss than a 150 square copper wire.

Talk about the common misunderstandings of those wires and cables

Nowadays, there are many kinds of wires and cables, and their performances are diverse. When buying All Aluminum Alloy Cable

, many people choose to learn about the various parameters and evaluations of the cables on the network, but because the information on the network is too complicated, it is difficult to distinguish between true and false. , Some wrong viewpoints will cause misunderstandings to many people who browse and watch, so many misunderstandings about wires and cables are formed. Here is a summary of several common misunderstandings.

Misunderstanding 1: There is radiation in wires and cables

Many people have seen on the Internet that wires and cables have radiation. To be honest, there is radiation, but those who have a little knowledge of physics should know that everything that uses electricity has radiation. Even an electric fan has radiation. Except for those high-risk radiation products, the amount of radiation from ordinary wires and cables is negligible and basically negligible.

And what you may not know is that the radiation of wires and AAAC cables is even weaker than that of the mobile phones we carry around every day, so those who are afraid of radiation from wires and cables, the first thing to do is not to stay away from wires and cables, but Throw away the phone quickly.

There are also some people who worry about the magnetic field generated by wires and cables, and think that this kind of magnetic field has an unhealthy effect on the human body. If they are worried about the magnetic field, it is even more nonsense, because everyone knows that our earth has a natural geomagnetic field , And it has a larger range and stronger power. If the magnetic field is not good for the human body, the entire earth is no longer suitable for human habitation. Our Mars immigration plan can only be started in advance, so we are worried about the radiation magnetic field of wires and cables.

Factors that cause power cables to overheat

AAAC Condutors are the basic facilities for transmitting electrical energy to every household or unit. Without it, we can enjoy modern life without electricity. However, precisely because it is placed in our work and living environment, it also brings certain hidden dangers to our lives, lives and work. There are countless fires caused by overheating of AAAC cables, whether at home or abroad, so what causes the overheating of wires and cables to cause fires? The following wire and cable manufacturers will give you a good introduction to what are the factors that cause the wire and cable to overheat? So everyone can be on guard.
1. The cable conductor resistance does not meet the requirements, which will cause the cable to overheat during operation. There is also improper cable selection, the conductor cross-section of the cable used is too small, and overload occurs during operation. After long-term use, the heating and heat dissipation of the cable will be unbalanced and cause overheating.

2. The partial sheath of the armored cable is damaged, which will cause slow damage to the insulation performance after water enters, resulting in a gradual decrease in insulation resistance, and overheating during cable operation.
3. When the cables are installed too densely, the ventilation and heat dissipation effect is not good, or the cables are too close to other heat sources, which affects the normal heat dissipation of the cables, and may also cause the cables to overheat during operation.
Fourth, the joint manufacturing technology is not good, the crimping is not tight, resulting in excessive contact resistance at the joint, and also causing the cable to overheat. The insulation performance between phases of the cable is not good, resulting in low insulation resistance and overheating during operation.

See what acsr conductor manufacturers mentioned above, as long as we usually choose a regular manufacturer when buying cables, buy high-quality wires and cables, and equip them with appropriate cables according to the actual situation of the project or project. The wiring installation is scientific and reasonable. Then it will not easily cause the cable to overheat or even cause a fire.
The above are the factors that cause the overheating of the wires and cables, do you understand it? Hope it helps you.

Corrosion resistance of aluminum alloy conductors

Aluminum alloy power conductor is a new type of material power cable that uses AA8030 series aluminum alloy material as the conductor and adopts special roll forming wire stranding production technology and annealing treatment. Alloy power cables make up for the shortcomings of pure aluminum cables in the past. Although the electrical conductivity of the cable is not improved, the bending performance, creep resistance and corrosion resistance are greatly improved, which can ensure that the cable remains continuous during long-term overload and overheating. The performance is stable. The use of AA-8030 series aluminum alloy conductors can greatly improve the conductivity and high temperature resistance of the aluminum alloy cable, while solving the problems of pure aluminum conductors and creep. The electrical conductivity of aluminum alloy is 61.8% of the most commonly used benchmark material copper IACS, and the current carrying capacity is 79% of copper, which is better than the pure aluminum standard. But under the same volume, the actual weight of aluminum alloy is about one-third of copper. Therefore, the weight of the aluminum alloy cable is about half of the copper cable at the same current carrying capacity. The use of aluminum alloy cables instead of copper cables can reduce the weight of the cable, reduce the installation cost, reduce the wear of the equipment and the cable, and make the installation work easier.

The inherent anti-corrosion performance of aluminum comes from the formation of a thin and strong oxide layer when the AAAC Conductor surface is in contact with air. This oxide layer is particularly resistant to various forms of corrosion. The rare earth elements added to the alloy can further improve the corrosion resistance of the aluminum alloy, especially the electrochemical corrosion. Aluminum’s ability to withstand harsh environments makes it widely used as conductors for cables in trays, as well as many industrial components and containers. Corrosion is usually related to the connection of different metals in a humid environment. Corresponding protective measures can be used to prevent corrosion, such as the use of lubricants, antioxidants and protective coatings. Alkaline soil and certain types of acidic soil environments are more corrosive to aluminum, so directly buried aluminum conductors should use insulating layers or molded sheaths to prevent corrosion. In sulfur-containing environments, such as railway tunnels and other similar places, the corrosion resistance of aluminum alloy is much better than that of copper.
Aluminum alloy has very good bending properties, and its unique alloy formula and processing technology greatly improve flexibility. Aluminum alloy is 30% more flexible than copper and has a 40% lower resilience than copper. Generally, the bending radius of copper cables is 10-20 times the outer diameter, while the bending radius of aluminum alloy cables is only 7 times the outer diameter, making it easier to connect terminals.
Armor characteristics
Commonly used armored cables are mostly armored with steel tape, with low security level. When subjected to external destructive forces, their resistance is poor, which is easy to cause breakdown, and the weight is heavy, the installation cost is quite high, and the corrosion resistance is poor. The life is not long. The metal interlocking armored cable we developed according to American standards uses aluminum alloy tape interlocking armor. The interlocking structure between layers ensures that the cable can withstand the powerful destructive force from the outside, even if the cable is subjected to greater pressure The cable is not easy to be punctured under the impact force, which improves the safety performance. At the same time, the armored structure isolates the cable from the outside world. Even in the event of a fire, the armored layer improves the flame-retardant and fire-resistant level of the cable and reduces the risk of fire. Compared with the steel tape armored structure, the aluminum alloy tape armored structure is lighter in weight, convenient to lay, and can be installed without bridges, which can reduce installation costs by 20% to 40%. According to the different places of use, different outer sheath layers can be selected, which makes the use of armored cables more extensive.

How to inspect Aluminum Alloy Cable ?

1.Coefficient of compression of wire core

Aluminum alloy cable and the traditional power cable process structure and auxiliary materials have certain differences, aluminum alloy cable conductor using aluminum alloy monofilament tightly pressed stranded way, its core compression coefficient reached 97%, the conductor is very dense, and the traditional copper-core cable, aluminum-core cable in the conductor cross-section can clearly see the difference (the traditional cable production process, the core of the tight pressure coefficient can only reach 82% or so).

2. Flexibility

Aluminum alloy cable using ASTM-B800 electrical control with 8000 series aluminum alloy wire, adding the appropriate amount of copper (Cu), iron (Fe), magnesium (Mg) … … and rare earth aluminum alloy materials and intermediate alloy materials developed through a special synthetic annealing process of high-tech new environmentally friendly energy-saving power cable, its conductor flexibility can be super strong, the Super flexibility can ensure the safety performance of aluminum alloy cable in actual application to reach or even surpass the copper-core cable, at the same time, it brings great advantages to the actual installation of aluminum alloy cable. In the actual test, direct hand folding test can get the aluminum alloy conductor is very flexible, it can be folded repeatedly or like a rope repeatedly winding, destructive folding aluminum alloy monofilament, experimental conclusion at least 18 times roundtrip before the crack or fracture phenomenon, while ordinary aluminum monofilament generally folded three times to crack, five times to absolutely break, an important disadvantage of ordinary aluminum wire is brittleness, in the As long as the installation of a certain angle of twisting, the conductor will have cracks, cracks will heat, corrosion, is an important cause of fire, which is also not times the universal application of the fatal reason.

3. Cable Structure

The aluminum alloy cable core adopts tightly pressed stranded way, the conductor cross-section is round core (traditional cable core more fan-shaped), the insulation adopts three-color co-extruded cross-linked polyethylene insulation process, the core arrangement rules, the whole cable round and flexible.

4.Bright and lustrous wire core

The aluminum alloy conductor has a bright and lustrous core cross section,such as overhead AAAC conductor 1/0 awg ,4/0 awg, which has a distinct organoleptic difference from conventional aluminum-core cables, due to the optimized crystallization of the conductor as a result of the rare earth alloys added during the smelting process.

5. Creep performance

The creep properties of the alloy conductor are almost identical to those of the copper core conductor, as shown by experiments: the yield strength of copper is 6.0, while that of the alloy conductor is 54, which is almost identical to that of copper, and 300% higher than that of the aluminum core conductor.

6. Extendibility

Elongation is an important indicator of the mechanical properties of the conductor, is an important symbol of the product and the size of the product can withstand external forces. It is also an important indicator for testing the mechanical properties of the cable bare conductor. Aluminum cable after annealing treatment of the elongation can reach 30%, while the elongation of copper cable for 30%, ordinary aluminum rod elongation of 15%, is an important indicator of the ability to replace the copper cable.

7. Tensile Strength

Since the density of aluminium alloys is only 30.4% of that of copper, even if the cross-sectional area of aluminium alloys is increased to 150% of the copper cross-sectional area, the weight of aluminium alloys is still 45% of that of copper, which means that the tensile strength of aluminium alloys is still lower than that of copper. Advantage. In large-span power projects, due to its specific gravity advantage, its tensile strength advantage in the equivalent premise is particularly prominent. It not only saves a large number of bridges and reduces the labor intensity of installation engineers, but also speeds up the installation process, saves construction time and greatly reduces the comprehensive installation cost.

8. Anti-corrosion performance

Aluminum alloy conductor itself has excellent anti-corrosion properties, the good anti-corrosion properties of aluminum alloy conductor from the inherent anti-corrosion properties of aluminum, its surface when in contact with the air, will immediately form a layer of about 2 ~ 4 μm thick layer of dense oxide film, this layer is very dense, especially resistant to all forms of corrosion, and thus has the characteristics of withstand the worst of the environment, in the actual service life of 10 years longer than copper cable. above. (The current domestic use of alloy cable time is not long, just 3 to 5 years, so from the domestic actually can not verify its actual service life. Can only refer to the actual use of foreign countries, on the current use of the European and American countries for 40 years, his actual service life is more durable than copper cable).

9. Electrical Performance

The resistivity of aluminum alloys is between aluminum and copper, slightly higher than aluminum and lower than copper, and an aluminum alloy conductor of the same length weighs only half as much as copper for the same cutoff current. If the conductivity of copper is 100%, the conductivity of the alloy conductor is about 62.5%, the specific gravity of the alloy is 2.7, and the specific gravity of copper is 8.9, then (8.9/2.7)×(0.612/1)=2, i.e., the resistance of 2 units of copper is the same as the resistance of 1 unit of mass of the alloy. The same cutoff current, resistance, and voltage losses as copper are achieved.