What to do if the cable is interfered

1 The radiation problem of the cable

The radiation problem of cables is one of the most common problems in engineering. More than 90% of the equipment (mainly equipment containing pulse circuits) can not pass the radiation emission test because of the radiation of the ACSR conductor. There are two mechanisms of cable radiation. One is the differential mode radiation generated by the signal current (differential mode current) loop in the cable, and the other is the common mode current on the wires (including the shielding layer) in the AAC conductor. The radiation of the cable mainly comes from common mode radiation. Common-mode radiation is generated by common-mode current. The loop area of ​​common-mode current is formed by the cable and the ground (or adjacent to other large conductors), so it has a larger loop area and stronger radiation.

How the common mode current is generated is often a problem that many people are confused about. To understand this problem, first make it clear that common-mode voltage is the root cause of common-mode current. Common-mode voltage is the voltage between the cab

and the ground (or other large conductors nearby). Starting from the common-mode voltage, it is easy to find the cause of the common-mode current. Once the cause of a problem is clear, it is not very difficult to solve the problem. The common mode current on the cable is caused by the following points: Common mode current caused by differential mode current leakage. Even if the cable contains a signal return line, it cannot guarantee that 100% of the signal current will return to the signal source from the return line, especially in At higher frequencies, various stray parameters in space provide a third or even more return path for the signal current. Although this common mode current accounts for a small proportion, the radiation cannot be ignored due to the large radiation loop area.


Do not try to reduce the common mode current by “disconnecting” the circuit from the ground (disconnecting the ground wire between the circuit board and the chassis, or disconnecting the ground wire between the chassis and the ground), thereby reducing the common mode radiation. Disconnecting the circuit from the ground can only reduce the common mode current at low frequencies, and the path formed by the parasitic capacitance at high frequencies has very low impedance. The common mode current is mainly generated by stray capacitance. Of course, if the problem of common mode radiation mainly occurs at low frequencies, disconnecting the circuit board or chassis from the ground will have a certain effect. From the mechanism of common mode current generation, it can be known that an effective way to reduce this common mode current is to reduce the impedance of the differential mode loop, thereby prompting most of the signal current to return from the signal ground.

Generally, the closer the signal line and the return line are, the smaller the impedance of the differential mode current loop will be. A typical example is a coaxial cable. Since the return current of the coaxial cable is evenly distributed on the outer sheath, its equivalent current coincides with the axis, so the loop area is zero, the differential mode impedance is close to zero, and almost 100% of the signal current Returning to the signal source from the outer sheath of the coaxial cable, the common mode current is almost zero, so the common mode radiation is very small. On the other hand, since the area of ​​the differential mode current loop is almost zero and the differential mode radiation is also very small, the radiation of the coaxial cable is very small. For high-frequency signals, use coaxial cables to communicate to avoid radiation. In fact, this has the same essence as our traditional use of coaxial cables to transmit high-frequency signals to reduce signal loss. Because the signal loss is small, it naturally shows that the leakage component is less, and this part of the leakage is the radiation of the cable.

Common mode current caused by ground noise of the circuit board. The signal ground wire is the return line of the signal. Therefore, there must be a voltage between two points on the ground wire. For high-frequency circuits, these are high-frequency noise voltages, which act as a common-mode voltage to drive the common-mode current on the cable. , Resulting in common mode radiation. The various design methods to reduce the ground wire impedance provided in the circuit board design chapter can be used to reduce the noise on the ground wire, thereby reducing the common mode voltage. A recommended method is to set “clean ground” on the cable port. The so-called clean ground means that there is no circuit that can generate noise on this ground wire, so the local potential on the ground wire is almost equal. If the case is a metal case, connect this piece to the metal case cleanly. Common mode current induced by electromagnetic waves in the chassis.

The chassis is always full of electromagnetic waves. These electromagnetic waves induce common-mode voltage on the cable. In addition, there are some circuits that generate high-frequency electromagnetic fields near the cable ports. There are capacitive coupling and capacitive coupling between these circuits and the cable. Inductive coupling creates a common mode voltage on the cable. Common mode voltage generated by electromagnetic induction. It should be noted that the electromagnetic waves in the chassis are mostly caused by the differential mode radiation of the circuit. In the circuit board design chapter, we discussed the frequency spectrum of the pulse signal differential mode radiation, which shows that the frequency range is very wide. This causes the frequency of the common-mode voltage to be much higher than what we expected.

Similarities and differences between electric welding machine cable and welding handle wire

Electric welding machine cables are commonly known as welding handle wires. The two are actually the same kind of cable, with superior flexibility and good bending performance. The sheath material is made of natural rubber or neoprene mixture, which can be applied to different occasions.
The neoprene compound sheath of the electric welding machine cable (welding handle wire) has heat resistance, oil resistance, non-flammability, and abrasion resistance. It is suitable for the secondary side of the electric welding machine with a voltage to the ground not exceeding 200V and a pulsating DC peak value of 400V. For wiring and connecting electric welding machines, special cables for electric welding machines.

Characteristics of electric welding machine cable (welding handle wire)
1. Frequent movement requires small outer diameter and light weight.
2. The long-term allowable working temperature of the cable should not exceed 65°C.
3. Sometimes hot welding parts are encountered, which require good heat deformation resistance.
4. The cables are frequently moved, twisted and cast, requiring softness and good bending performance.
5. It is easy to be scratched and rubbed by sharp steel components during the operation, so the cable insulation is required to have good mechanical properties such as tear resistance and abrasion resistance.
6. The welding machine cable works under low voltage (the highest voltage is 200V) and high current conditions, and requires a certain degree of heat resistance.
7. The use environment is complex, such as sunlight, water boiling, contact with muddy water, machine oil, acid and alkali liquids, etc., which require certain weather resistance, oil resistance, and solvent resistance.
Because the electrical performance of this kind of cable is not high, and the use environment is complicated, it is not suitable to meet various complex environmental factors in the structure. When using, pay attention to improving the conditions of use to prevent external damage.

Precautions for choosing household powercable

In home decoration, water and electricity decoration is the most important, especially the electrical part, because it involves the safety of electricity use. If there is a problem with the electrical decoration, it may directly affect the safety of the family and the consequences are quite serious. Therefore, whether it is the wiring, connection, or purchase of PE Cable, there must be reasonable planning and prior understanding.
At present, there are two types of wires for household use on the market, single-core and multi-core. Single-core wire means that the internal conductor is a relatively thick copper core, and the multi-core wire is twisted together by multiple thin copper cores. In comparison, single-core wires have higher hardness, and multi-core wires are softer, and their advantages and disadvantages are also obvious. You need to choose according to your own needs.

220V alternating current is used in the family, whether it is a single-core wire or a multi-core cable, as long as the qualified product is suitable for working under such conditions, the performance of the single-core wire will be more stable and the surface area It is small, not easy to be oxidized, and has higher mechanical strength. Multi-core cables are more flexible and easier to pull and bend, which is more convenient in the installation process, and it is not easy to damage the wires. In terms of price, the price of a single core is slightly cheaper, so when considering whether to use a single core or a multi-core wire, you need to choose according to your own needs and the characteristics of the wire.

In addition, when choosingSingle core cable, the most important thing is to see whether it meets the national standard. It cannot be a shoddy non-standard product. There are manufacturers, specifications, wire diameters, certification marks, and anti-counterfeiting queries on the wires. As for the amount of wire to choose at home, it should be determined according to the number and requirements of electrical appliances in the home. Generally speaking, the light wire uses 1.5 square wire, the socket uses 2.5 square wire. There are more electrical appliances in the kitchen and bathroom, and the power is large. It is best to use 4 square wires, vertical air conditioners use 4 square wires, and central air conditioners use 6 square line.

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.

The first 525 kV DC cable pre-qualification test is officially launched

On February 26, the first domestic pre-qualification test of 525 kV DC cables was officially launched. The test mainly detects the long-term performance of domestic 525 kV DC cables, and provides important technical support for Chinese cable companies to take the initiative in international competition.
It is understood that the Dutch government plans to develop a 6.1 gigawatt wind farm by 2030. In the face of the connection of large-capacity, long-distance offshore power grids and onshore power grids, 525 kV DC cables will be the most economical transmission method. The State Power Supplier invited 8 cable manufacturers from around the world to participate in the research and development of 525 kV DC sea and land cable systems. Entrusted by domestic cable companies, Zhejiang Zhoushan Power Supply Company Marine Transmission Engineering Technology Laboratory officially launched the pre-qualification test of 525 kV DC cables.

According to the test schedule, the laboratory has completed mechanical pretreatment tests, full-scale space charge detection, and DC withstand voltage test and other test items, and will carry out a long-term voltage test of 8760 hours and a DC superimposed impulse voltage test in the future.
This test carried out tests on both the submarine cable system and the Aerial Bundled Cable (ABC) BS 7870 Standard system samples, and fully applied the scientific research results of the national key research and development plan project “±500 kV DC cable system test and operation and maintenance technology”. The space charge measurement and evaluation technology under the simulated operating conditions of the high-voltage DC cable, the leakage current under the pre-qualification test of the DC cable and the distributed optical fiber temperature monitoring technology are integrated into the test system to ensure the scientific accuracy of the test.

The smooth advancement of the 525 kV DC cable system pre-qualification test will significantly enhance the international influence of the State Grid Corporation of Compete and win a broader overseas market.

The reason why cable manufacturing cannot do without plastic

1. Melt index

Under a certain temperature and pressure, the number of grams of molten resin extruded from a certain hole in 10 minutes is called the melt index, expressed in MI, and the unit is g/min.

2. Cold resistance

The ability of plastics to buy AAAC conductor maintain certain physical and mechanical properties at low temperatures is called the cold resistance of plastics. It is often expressed by the following cold-resistant temperature.

1) Low temperature embrittlement temperature: it is the temperature at which 50% of the ACSR conductor full form samples are damaged when the plastic is subjected to a specific impact load at a low temperature.

2) Low temperature half-folding temperature: it is the temperature at which the plastic sample is about to rupture when it is bent 180o.

3) Low-temperature impact compression temperature: it is the temperature at which the plastic sample is impacted and compressed by a hammer with a certain energy and speed at a low temperature to make the rupture rate reach 50%.

11. Flame resistance

Flame resistance refers to the ability of plastics to resist flame burning. Generally, plastics will burn after contacting the flame. After the flame is removed, the flame extension varies with different types of plastics, so the flame resistance performance is also different.

3. Heat aging performance

In the process of plastic processing and use, the performance of the plastic deteriorates due to heat. This phenomenon is called thermal aging. The ability of plastics to resist heat aging is called heat aging resistance. Use accelerated thermal aging test at high temperature to determine the retention rate of plastic properties (mechanical properties or electrical properties) after aging to measure the heat aging resistance of plastics.


4. Weather resistance

Plastics are used under atmospheric conditions and are affected by harsh natural conditions such as sunlight, rain, wind, and air pollution. The deterioration of plastic performance is called atmospheric aging. The ability of plastics to resist atmospheric aging is called the weather resistance of plastics.

5. Oil resistance and solvent resistance

When plastic comes into contact with mineral oil or various solvents, its ability to resist oil or solvent is called the oil resistance or solvent resistance of the plastic. The sample can be immersed in oil or solvent, and after a certain time at a certain temperature, the absorption rate, volume change rate or tensile strength and elongation retention rate of the oil or solvent can be measured.

6. Water resistance and humidity resistance

The ability of plastics to resist the penetration of water or humid gas under water or humid conditions is called the water resistance or moisture resistance of plastics. After the plastic absorbs water or moisture, it will cause a decrease in insulation resistance, breakdown field strength, increase in dielectric loss, and changes in the appearance, weight, and mechanical properties of the plastic. Therefore, plastics are required to have good water resistance and moisture resistance. For plastics used in wires and cables, the main consideration is to ensure that the electrical insulation properties of the plastics meet the requirements of use after immersion or moisture absorption. The water absorption of plastic can be expressed by the water absorption per unit area, the water absorption rate or the water absorption weight. The moisture permeability of plastics is expressed in terms of moisture permeability coefficient and vapor permeability.

Five Well-known Cable Brands in China

1. TBEA 
TBEA Co., Ltd. (TBEA Co., Ltd.) referred to as “TBEA” (A stock code: 600089) is a service provider that provides system solutions for the global energy industry and is a large local industrial manufacturing in Xinjiang The enterprise is a large-scale energy equipment manufacturing enterprise in China. It is composed of nearly 20,000 employees from 29 ethnic groups including Uyghur, Han, Kazakh, Hui, Mongolian, and Tajikistan in 24 countries around the world. my country’s large-scale aluminum electronics, polysilicon new material development and export base, a large-scale solar photovoltaic system integrator, has 14 domestic manufacturing industrial parks, and two overseas bases.

2. Zhongtian Technology
Zhongtian Technology started in 1992 and started with optical fiber communications. With the rapid development of the national information industry, it has now formed a two-wheeled industrial scale driven by telecommunications and power grids, and is involved in the field of new energy. It has successively been awarded gold medal listed company, national innovative pilot enterprise, and ranked among the top 100 Chinese electronic information and top 500 private enterprises in China.
The layout is Beijing headquarters, Nantong new department, Rudong headquarters. The company adheres to the “going global” strategy, exports its products to more than 100 countries and regions, opens factories in India and Brazil, and has more than 40 overseas offices to gradually build ZTT into a world-class Chinese optoelectronic cable brand.

3. Henan Huaxing Cable
Henan Huaxing Wires& Cables Co. was established in 1984 and is a specialized and large-scale cable manufacturer. The company is mainly committed to the system research and development, design, manufacturing, marketing and service of four major types of cable products such as overhead wires, power cables, electrical equipment wires and cables, and household cables. Products are widely used in power transmission, transportation, energy, petrochemical and other industries as well as urban construction and other fields. They are sold all over the world and are deeply trusted by users.
The company adheres to the quality policy of “innovative work, technological refinement, quality, and trust”. In recent years, it has successively introduced more than dozens of advanced technologies and equipment from Finland, Switzerland, the United States, Japan, Germany and other countries. An assembly line operation has been formed, and the production equipment has basically reached the domestic first-class level. The company has complete inspection, measurement and testing institutions and advanced equipment, which provide a fundamental guarantee for high-quality products. Pursue and produce high-quality products consistently.

4. Baosheng Cable
Baosheng Group Co., Ltd., a subsidiary of Aviation Industry Corporation of China, was established in 1985. Its R&D and marketing centers are located in Jinshan District and Putuo District, Shanghai, and its production centers are located in Yangzhou City and Baoying County, Jiangsu. It is a relatively competitive power and intelligent industry group in China that integrates wires and cables and systems, cable materials, electrical appliances, high, middle and low voltage inverters, servo systems, industrial robots and logistics services, as well as the construction and operation of photovoltaic power stations. Baosheng Group is a provider of power projects such as power station construction, power engineering, power facilities, and information technology and intelligent system engineering solutions. It can provide from engineering design to cable and electrical product design, manufacturing, installation, photovoltaic power generation, and construction. A complete set of systematic and integrated services such as steel structure and general engineering contracting

5. Delixi Electric
Delixi Electric Co., Ltd. was established on January 4, 2007, located in Liushi Town, Yueqing City, Zhejiang Province, with a cumulative investment of nearly 2 billion yuan, covering an area of ​​600,000 square meters, and employing more than 10,000 employees. It is a large-scale joint venture in China’s low-voltage electrical industry.
Through 30 years of unremitting efforts of two generations of Delixi people, the “Delixi” brand has become a household name in China.

Why is the cable hot?

In recent years, various types of electrical appliances often catch fire in our daily lives. Therefore, when using electrical appliances, the cables need to be protected. However, I don’t know if you find that the cable will heat up during operation. Is it a manifestation ofAerial Bundled Cable (ABC) HD 626 S1 Standardquality problems? Or is it a normal phenomenon of cable use? What is the cause of the cable heating during operation? How should we deal with the heating of cables?
If the cable becomes hot during operation, this does not mean that there is a problem with the cable quality, but the normal operation of the cable. As long as the cable passes a certain load current, it will definitely heat up, and as the load current increases, the surface temperature of the cable will be higher. Therefore, it is basically normal to control the surface temperature of the wire below 60 degrees.

The reasons for the cable heating during operation are as follows:
1. The cable conductor resistance does not meet the requirements, causing the cable to generate heat during operation.
2. Inappropriate cable selection, for example: the conductor cross section of the cable is too small, and overload occurs during operation. The heat dissipation and heat dissipation of the cable are unbalanced after long-term use, causing the cable to heat up.
3. When the cables are installed too densely, the ventilation and heat dissipation effect is not good. OrAerial Bundled Cable (ABC) SANS 1418 Standard is too close to other heat sources, which will affect the normal heat dissipation of the cable, and may also cause the cable to heat up.
4. The manufacturing process of the cable joint is not good and the crimping is not tight. If the contact resistance at the joint is too large, it will also cause the cable to heat up.

5. The insulation performance between the phases of the cable is not good, which leads to low insulation resistance and heat generation during operation.
6. Part of the sheath of the armored cable is damaged. After the water enters, it will slowly damage the insulation performance. As a result, the insulation resistance will gradually decrease, and it will also cause heat during the operation of the cable.
After the cable heats up, if the cause is not found, the fault should be eliminated in time, and the continuous power operation will continue. The insulation thermal breakdown phenomenon will occur, causing the cable to short circuit and trip between the phases, which may cause a serious fire.
So, how to deal with the heating of the cable? Since the cable heats up when there is current passing through it, we cannot cool the cable in cold water because this will cause water to enter the cable and affect the use of the cable. Therefore, when using the cable, we can only pay attention to the use time of the cable and distribute the power reasonably. The cables should be checked regularly to see if they are old or damaged. If this is the case, the cable should be replaced in time to avoid causing the cable to catch fire.

The difference between an open wire and a dark wire

Hydropower renovation is carried out before interior decoration, which is also a key link in the entire renovation process. If there is an error, it will bring a lot of trouble to the future decoration work. Time is wasted and money is wasted, so the early hydropower transformation is more important and attract enough attention. Many people are struggling with a problem now. Is it better to install an open wire or a hidden wire? Let us find out.
1. Advantages of installing hidden wires:
1. Security
Our first consideration is safety. If PVC XLPE Insulated Power Cable 25mm² ~ 400mm² are exposed, the chance of direct contact with the human body after an accident will increase, and the damage rate will be higher.
2. Beautiful
The dark lines make them invisible from the outside, so that the surface looks more beautiful and will not affect the overall design of the room.
3. Life
The main reason is to hide the wires on walls that are prone to aging. The surface air circulation of the bare wire is relatively fast, and the continuous change of temperature increases the aging speed of the circuit.
Disadvantages of installing hidden wires:
The main reason is that the construction is more difficult and troublesome, so there are three problems: one is that the construction period needs to be extended, the other is the increase in construction cost, and the third is that the technical requirements are high and ordinary people cannot be hired. However, some people say that the installation of grooves will affect the building, but I think that in accordance with the construction rules, control the depth of the grooves and do not open holes at will, basically there will be no problems.

2. So which of the two costs money?
Perhaps most people think that installing hidden wires is troublesome, and the cost will naturally be high; but what is unexpected is the cost of installing wires, mainly the construction cost; but installing open wires is the cost of building materials; installing open wires requires the use of BVVB or RVV The cost of this kind of wire is much higher than that of BV wire and BVR wire.
What is the voltage, DC or AC… 90% of the people are immediately dumbfounded…

3. Construction skills
1. When power distribution wires, there should be no knots or kinks in the pipeline. When connecting PVC pipes, joints are required, and glue must be used to bond them firmly.
2. Distribution lines include strong current lines and weak current lines: network lines, telephone lines, air-conditioning lines, TV lines, lighting lines, etc. should be placed with bushings.
3. We all prohibit burying wires directly in the plaster layer.
For the construction of the above-mentioned lines, you need to pay attention to skills and methods, and pay attention to the wiring method. The installation of wires will have a major impact on our future lives.
The above mainly introduces whether the wires are installed with open wires or hidden wires. I believe that through reading the above, everyone has a better understanding of the installation of aaac conductors. Thank you for reading.

Selection of power cables for home use

The decoration of the new house has many small and large details, and every detail needs to be taken seriously. This is because many decorative details are related to the comfort and safety of the house. However, there are many decorative materials on the market. Therefore, many friends do not know how to choose when choosing materials. Among them, everyone is more entangled. The question of material selection is: Should power cables be flexible wire? Or should I choose a hard line! What is the difference between hard wire and soft wire? Below, I will give you a brief explanation.
Before choosing hard wire or soft wire, we must first know what is hard wire? What kind of wire is a flexible wire?
The so-called flexible wire refers to strands of conductive solid wires with a diameter less than 1mm twisted together, that is, multiple strands of copper wires are twisted together. Therefore, the flexible cord is also called “sheathed cord”. Hard wire refers to a hard wire composed of several thick copper cores. Generally, hard wires of less than 10 square meters are single stranded.

So, what are the advantages and disadvantages of soft and hard wires? The details are as follows.
From the point of view of the service life of the wire, because the hard wire is thicker, it is not easy to oxidize; the flexible wire is composed of multiple thin copper wires, which are easily oxidized by the air, so the service life of the hard wire is much longer than that of the flexible wire From the perspective of the cost of the wire, since the flexible wire is relatively soft, it must be wound many times before use; the hard wire has only one copper wire, which can be passed directly. Therefore, compared with flexible wires, hard aaac conducors have less processing and are much cheaper; from the perspective of current-carrying capacity, flexible wires are composed of multiple strands of copper wire, and their current-carrying capacity is greater than that of a single copper wire. , But when it is suddenly loaded, the capacity of the current-carrying hard wire is greater than the capacity of the flexible wire; therefore, if it is used in general household appliances and the current does not exceed 100 A, single-stranded wire can be used.

2. From the perspective of the working process of the wire, use a soft wire at the connection of the hot tin or iron wire end, otherwise the multi-stranded wire may rise and connect with the next wire, which is very dangerous; and the hardness of the hard wire Very strong, its safety performance is relatively strong, from the perspective of whether it is convenient to repair the wire; although the hard wire is more difficult to replace, it can be completely pulled out of the threaded tube; if necessary, you can also replace the threading; but The cord is different, because the cord is prone to aging and breaks easily, so when the cord is replaced, the wire is likely to be damaged.
Generally, hard wires are more suitable for household use. However, it is worth noting that not all household wires need to use hard wires, and some places are more suitable for flexible wires. Therefore, when choosing wires, you should choose according to the location of the wires and the needs of your own home.