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.

How to find the fault point after the ACSR cable is short-circuited?

Generally speaking, when the ACSR conductor has a short-circuit fault, the air switch cannot be closed, which will not only cause a small-scale power failure, but if it is not handled properly, it may sometimes expand the scope of the fault and even cause an electric shock accident. Therefore, if the short-circuit fault is not eliminated, illegal power transmission is absolutely not allowed.

When dealing with a short-circuit fault of a cable, try not to break the cable destructively. In that case, it will damage the cable insulation, reduce the insulation strength of the cable, and cause electric shock. So, how to find the short-circuit point quickly and effectively when the cable has a short-circuit fault?

 

 

The main methods are as follows:

1. The place where the cable has a connector is the frequent occurrence point of cable short-circuit faults. When searching, the main search object is the cable connector.

ASTM 477 MCM ACSR Cable

2. If ASTM 477 MCM ACSR Cable is erected for a long distance, and there is a short circuit in the middle or at the end of the cable, the tripping time of the air switch may be delayed. This is because the short-circuit point is far from the air switch and there are A certain resistance value reduces the short-circuit current. If this is the case, the section of cable from the short-circuit point to the circuit breaker will definitely heat up and be higher than the temperature of the human body, and the rubber sheath will become soft or even bulge. At this time, touch the hot cable with your hand until it suddenly becomes cold. The place where you feel the cable hot is the short-circuit point.

3. If it is a two-core lighting cable, the light bulb from the short-circuit point to the power circuit breaker will emit light, but due to insufficient voltage, the light will be dim, and the light bulb after the short-circuit point will not light up at all.

Requirements for power cable use

Power cables are usually rope-like cables formed by twisting several or several groups of wires. Each group of wires is insulated from each other and is often twisted around a center. The entire outer layer has a highly insulating coating. They are mostly erected in the air, underground, or underwater for telecommunications or power transmission. Cables can be divided into power cables, communication cables and control cables according to their uses. So are there any safety requirements when using the cable? Let’s look at it in detail next.

1. When the cables cross each other, the high-voltage cables should be under the low-voltage cables. If one of the cables is protected by a pipe or separated by a partition within 1m before and after the intersection, the smaller allowable distance is 0.25m.

2. When the cable is close to or crossing the heating pipe, if heat insulation measures are provided, the smaller distance between parallel and crossing is 0.5m and 0.25m respectively.

 

 

3. When the ACSR conductor crosses the railway or road, it should be protected by a pipe. The protective pipe should extend 2m beyond the track or road.

4. The distance between the cable and the foundation of the building should be able to ensure that the cable is buried outside the building’s scattered water; when the cable is introduced into the building, it should be protected by a pipe, and the protective pipe should also exceed the building’s scattered water.

 

5. The distance between the cables directly buried in the ground and the grounding of the general grounding device should be 0.25~0.5m; the buried depth of the cables directly buried in the ground should generally not be less than 0.7m, and should be buried under the frozen soil layer.

The above is about the safe use of wires and cables. When using wires and cables, they must be in accordance with the standards to prevent the wires and cables from causing losses.

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.
flexibility
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.

What are the differences between YJV3+2 and YJV4+1 cables?

The YJV power cable  is composed of one or several soft wires, and the outer covering is covered with a light soft sheath; the cable is composed of one or several insulated wires, and the outside is covered with a tough outer layer made of metal or rubber.

As we all know, there are single-core cable and multi-core distinctions in wire and cable. Single-core cable means that there is only one conductor in an insulating layer, and multi-core means that there are multiple conductors in an insulating layer. Then there will be doubts from users who don’t know. 3+2 cores and 4+1 cores are both 5 cores. What is the difference between them? YJV3+2 and YJV4+1 cables are wires and cables.  In fact, these two kinds of wires and cables have their own characteristics.

The 3+2 and 4+1 on the YJV power cable indicate the number of cores of a cable. There are 2 or 3, 3+2, 4+1, and 5 wires that are insulated from each other in a cable, respectively Called 2-core or 3-core, 3+2 core, 4+1 core, 5 core wire.

What is the difference between YJV3+2 cable and YJV4+1 cable in the model name?

1.YJV 3+2 core

3 of the 3+2 cable is the three phase wires (L1, L2, L3 phase wires, the diameter of these three wires is large), the diameter of the wires is the same, 2 is the neutral wire and the PE wire, and one wire is used to connect the neutral wire (N in The diameter of this wire is smaller than L1, L2, L3), and one wire is used to connect to the grounding wire (PE grounding protection wire, this diameter is also smaller than L1, L2, L3).

2.YJV 4+1 core

The 4 of the 4+1 cable means that the diameter of the three phase wires is the same as the diameter of the neutral wire, 1 means that the PE ground wire has a single diameter; 4+1 means that a cable consists of 4 wires, one of which is used to connect to the live wire (L1 phase wire). ), one wire is used to connect to the neutral wire (N neutral wire), and one wire is used to connect to the ground wire (PE grounding protection wire).

The above is about the structure difference between YJV3+2 cable and YJV4+1 cable, and the difference in naming. We all know that cables are named based on models, and different models of cables are different in nature, and each model of cable has its own characteristics.

General Rubber Plastic Wire Structural Characteristics

Requirements of General rubber plastic wire:
1. Scope of application: connection and internal installation of power, lighting, electrical equipment, instrumentation and telecommunication equipment with AC rated voltage of 450/750V low voltage cable and below.
2. Laying occasions and methods: indoor open laying and communication channels, along the wall or overhead laying in tunnels; outdoor overhead laying, laying through iron pipes or plastic pipes, electrical equipment, meters and radio installations, all fixed laying; plastic The sheathed wire can be directly buried in the soil.
3. General requirements: economical and durable, simple structure.
4. Special requirements:
1) When laying outdoors, due to the influence of sunlight, rain and freezing conditions, it is required to be resistant to the atmosphere, especially sunlight aging; cold resistance requirements are required in severe cold areas;

2) In use, it is easy to be damaged by external force or flammable, and it should be worn in the occasions where it is in contact with oil. When the pipe is worn, the wire is subject to greater tension and may be scratched, so lubrication measures should be taken;
3) When used internally for electrical equipment, when the installation location is small, it should have a certain degree of flexibility, and require clear color separation of the insulated wire core, and should be matched with the corresponding connector terminals and plugs to make the connection convenient and reliable; for occasions with electromagnetic protection requirements , Shielded wires should be used;

4) For high ambient temperature occasions, sheathed cables should be used; for special high temperature occasions, heat-resistant cables should be used.

Structural features
1. Conductive core: when used for internal installation of power, lighting and electrical equipment, copper core is preferred. For large cross-section wires, it is better to use compact core; bare conductors for fixed installation generally adopt category 1 or category 2 conductor structure .
2. Insulation: Insulation materials generally use natural styrene-butadiene rubber, polyvinyl chloride (PVC) cable, polyethylene, and nitrile polyvinyl chloride compound; heat-resistant wires use polyvinyl chloride with a temperature resistance of 90°C.
3. Sheath: There are generally five types of sheath materials: polyvinyl chloride, cold-resistant polyvinyl chloride, anti-termite polyvinyl chloride, black polyethylene, and neoprene rubber.


Especially cold-resistant and outdoor overhead laying should use black polyethylene and neoprene sheathed wires.
In environments with external forces, corrosion, humidity, etc., rubber or plastic sheathed wires can be used.

Cable selection method of generic cabling system

Generic cabling is one of the key links of information network system. In order to ensure the high-speed and stable operation of information network system, it is particularly important to select high-quality and high-performance cables.

The cable selection should be based on the system requirements, technical performance, investment estimates and other factors, but in the wiring system, it should first determine the type of cable used and the structure of wiring (unshielded cable, shielded cable, optical cable or mixed use). Cables usually use Aluminum conductors with insulation and one or more layers of plastic sheath. The cable usually consists of 2 to 3600 pairs. Large logarithmic cables are usually used in backbone cabling systems and are suitable for voice and low rate data transmission. The maximum lengths of these cables for trunk and horizontal (hub to desktop) cabling systems are specified in the latest GB 50311-2007. It should be noted that these maximum length limits apply to all media. They do not consider the impact of performance differences due to different cable types and protocol types used in the network. In fact, the maximum cable length will depend on the application of the system, the type of network and the quality of the cable.

Method of cable selection in generic cabling system

Since it is a building, it will definitely use a lot of communication cables. As the nervous system of intelligent building, generic cabling system is the key part and infrastructure of intelligent building. It has a very close relationship with the planning and design, construction, installation and maintenance of construction engineering. It is like an information superhighway in the building. People can communicate and communicate conveniently, quickly and effectively. It can be said that the generic cabling system connects the communication, computer and various facilities and equipment in the intelligent building to form a complete set of whole, so as to meet the requirements of highly intelligent.

But then we have to consider a problem: fire prevention. Once a fire breaks out in the building, the heat and gas released by these cables will become a major safety hazard. Looking at several large-scale fire accidents in China in recent years, many of them are due to the fact that the victims can’t escape. The burning of cables emits poisonous acid gas. In addition, a lot of heat and smoke are released from the combustion, which makes it difficult for the victims to breathe and lead to tragedies. Therefore, in addition to considering the performance, fire protection and environmental protection are also very important reference factors when we select cables for generic cabling system.

Discussion on environmental protection requirements of PVC cables and wires

The use of non environmental protection cables is strictly prohibited in developed countries, and China also attaches great importance to this field. China’s relevant laws and regulations clearly require the use of PVC wires and cables in important buildings. Halogen free and low smoke crosslinked PVC wires and cables must be used to avoid heavy smoke and chlorine gas causing casualties in case of fire.

Environmental protection cable will effectively drive the development of cable industry, enhance the competitiveness of cable manufacturer, and make the cable industry more and more stable on the road of sustainable development in green practice and innovation. In recent years, China’s cable enterprises have gradually made efforts to environmental protection cables and low smoke and halogen-free cables. As far as possible, they do not contain heavy metals such as lead, cadmium, mercury, bromine flame retardants, harmful halogen gases, corrosive gases, less heat during combustion, and no soil pollution. Environmental protection cables will be more favored by the market, and will be recruited by power grid companies It is easier to get high order in the bid.

The user’s requirements for environment-friendly wires and cables can be summarized as follows:

1. Low content of lead and heavy metals is required

It is well known that lead and some heavy metals will have adverse effects on human health. In PVC formulation, additives such as lead, cadmium, barium and other heavy metal compounds are usually needed. However, since the 1990s, some developed countries and large electric companies have successively formulated laws and regulations. In the PVC wires and cables used, there are eight kinds of heavy metal content shall not be greater than the regulations. These new regulations not only bring new business opportunities to wire and cable manufacturers, but also bring serious challenges to PVC cable manufacturer.

2. Low smoke and low hydrogen oxide are required

Good flame retardant performance is a very obvious advantage of PVC wire and cable. However, when ordinary flame retardant PVC cable is on fire, it will release thick black smoke and a large amount of HCI gas, which will cause “secondary disaster” after the fire, and seriously affect personnel evacuation and fire rescue work. Therefore, in addition to the flame retardant requirements for wires and cables, the requirements of “low smoke” and “low HCI” will be put forward in some applications.

3. Low toxicity or non toxicity is required

In addition to lead-free and heavy metal free, non-toxic (or low-toxic) cables are required for some household appliances, medical and health appliances and children’s electric toys that may come into contact with food and blood products. This means that all constituent materials used in PVC formulations should be non-toxic. There are a lot of plasticizers in cable materials, but the non-toxic plasticizers must be used to manufacture non-toxic materials. Therefore, the requirements of this PVC material are higher than that of lead-free and heavy metal free materials, and the price is naturally more expensive.

4. Other prohibited items

At present, the regulations being reviewed by the EU impose restrictions on the following items to ensure that wires and cables meet the requirements of environmental protection. For example: 1) asbestos; 2) biphenyl and its ethers, polybrominated phenol; 3) polychlorinated biphenyls; 4) short chain (C10-C13) chlorinated paraffin.

With more and more attention to environmental issues, many countries have formulated a variety of environmental protection policies, so people prefer to use green cable. Low smoke halogen-free flame retardant cable material is one of the most popular environmental protection cables. Although China’s market demand for green cable is growing, compared with developed countries, China still has a long way to go in terms of relevant policy formulation and mandatory application. China should improve the environmental protection cable standards as soon as possible.