China Zhenglan Cable Technology Co., Ltd Company News

Power cable is used to transmit and distribute electric energy. It is often used in underground power grid, power station outgoing line, internal power supply of industrial and mining enterprises and transmission line under river and sea. In power lines, the proportion of cables is increasing gradually. Power cable is main line of power system to transmit and distribute high-power power power, including 1-500kv and above voltage levels and various insulation power cables. Construction: The basic construction of power cable consists of four parts: core (conductor), insulation, ssreec and jacket . 1.Core The core is the conductive part of the power cable, which is used to transmit the electric energy, and is the main part of the power cable. 2.Insulation Insulation layer is an indispensable part of the structure of power cable, which separates the core from the earth and the cores of different phases in electrical field to ensure the transmission of electric energy. 3.Screen The power cables with 15kV and above generally have conductor shielding layer and insulation shield layer. 4.Jacket The function of the protective layer is to protect the power cable from the invasion of external impurities and water, and to prevent the external forces directly damaging the power cable.

XLPE or Cross-linked polyethylene is a thermoset insulation material. Crosslinking polymers is a process which changes the molecular structure of the polymer chains so that they are more tightly bound together and this crosslinking is done either by chemical means or physical means. Chemical crosslinking involves the addition of chemicals or initiators such as silane or peroxide to generate free radicals which form the crosslinking. Physical crosslinking involves subjecting the polymer to a high energy source such as high-energy electron or microwave radiation. Polyethylene (PE) material itself has excellent dielectric strength, high insulation resistance, and a low dissipation factor at all frequencies making it an ideal insulator, however it is limited in its temperature range. Cross-linking the PE to become XLPE increases the temperature range of the insulation whilst maintaining the electrical properties.

Cable withstand voltage test is a way to find faults in the presence of cables. It is easily affected by various factors during the test, resulting in problems such as failure and short circuit. The main methods of several cable withstand voltage tests are described below. First, ultra low frequency withstand voltage test The ultra-low frequency (0.1Hz) withstand voltage test method first appeared in 1980, and it is mainly a non-destructive test method for observing whether there is insulation defect in cable operation, and the method has been verified by a large number of laboratory tests and field tests. The low-frequency withstand voltage test has a good application effect in the low-voltage power cable withstand voltage test. The method utilizes the principle of converting 50 Hz alternating current into direct current voltage through rectification and filtering, and then converting the direct current voltage into an alternating current voltage of 1 kHz through an inverter circuit, and then performing amplitude modulation processing by a 0.1 Hz sinusoidal oscillator, and after amplitude modulation, 1 kHz. The amplitude wave such as the AC voltage is converted into a 0.1 Hz varying beam wave. It is mainly based on the high voltage formed between the high voltage transformer and the voltage multiplying circuit, which is mainly characterized by a sine wave and is mediated by a varistor, so that the high AC voltage load output is a 0.1 Hz high voltage sinusoidal waveform. The advantages of the ultra-low frequency withstand voltage test are mainly: 1 no damage; 2 high accuracy; 3 small size, easy to carry. However, the output voltage level of this method is low, and it is mainly used in the medium and low voltage cable withstand voltage test. Second, the modulated power frequency series resonance test The method mainly utilizes the inductive reactance of the reactor and the capacitive reactance of the measured cable capacitance to generate a resonance in a 50 Hz power frequency environment, and a high voltage is generated in the process. The advantages of the modulated power frequency series resonance test are: 1 the output current waveform is basically a sine wave; 2 is high in specificity, and only after the series resonant circuit satisfies the condition for generating resonance, a high voltage is formed, and the cable to be tested is once tested. If there is a problem, it will cause a loop abnormality, which is equivalent to a short circuit of the cable. The high voltage will also appear to be uniformly dropped. Moreover, since the reactor can limit the short-circuit current, the protection device is not affected, and thus it is not necessary to install a resistor protection device. The disadvantage of this test method is that the operation is complicated, the system quality factor is not high, the automation level is low, and the noise is large, which limits its application in practice. Third, the frequency conversion series resonance test The principle of frequency conversion series resonance test is similar to the above-mentioned principle of modulated power frequency series resonance test. The difference is that the frequency conversion series resonance test realizes the resonance of the test circuit by adjusting the output voltage frequency in the variable frequency power supply; In the frequency series resonance test, the resonance of the test circuit is realized by the inductance generated by the regulating reactor at the 50 Hz power frequency. The advantage of the variable frequency series resonance test is that when the required power supply capacity of the test is lower than the power supply capacity of the cable under test, the test can be performed at a much lower power than the required power supply, which can effectively improve the efficiency of the field test and can overcome The shortcomings of the modulated power frequency withstand voltage test device make it more widely used in real life. In addition, the operating frequency of the variable frequency series resonance test is only 30 to 300 Hz, which can improve the problem that the frequency of the ultra-low frequency withstand voltage test is too low and the loss is small, which is inconsistent with the actual loss. Therefore, the results obtained by the variable frequency series resonance withstand voltage test are precise, comprehensive and reliable.

ACSR cable is a kind of steel-cored aluminum stranded cable, which has the characteristics of simple structure, easy erection and maintenance, low cost, large transmission capacity, and convenient for laying across rivers and valleys and other special geographical conditions, as well as good electrical conductivity, sufficient mechanical strength, high tensile strength, and the distance of tower pole can be enlarged.Therefore, it is widely used in various voltage levels of overhead transmission and distribution lines.

1. Skin burning method: Ironing the insulation layer with an electric iron should have no obvious dents. If there are large dents, it indicates that the material or process used for the insulation layer is defective.After a long time of burning, the insulation layer of the cable is still relatively intact. There is no smoke or irritant smell. At the same time, the diameter increases.If it is easily ignited, it can be ascertained that the insulation layer of the cable is not made of a low smoke halogen-free material (most likely polyethylene or crosslinked polyethylene).If there is a large amount of smoke, the insulating layer is made of halogenated material. 2, hot water soaking method: put the core wire or cable in 90 ℃ hot water immersion, insulation resistance will not normally fell sharply and keep above 0.1 M Ω / Km.Ω such as insulation resistance fell sharply even less than 0.009 M/Km, then without proper irradiation crosslinking process.(Polyethylene or crosslinked polyethylene insulation materials do not apply to this method of identification, can be identified using the same method). 3. Density comparison method: The density of low-smoke halogen-free material is higher than that of water, so a little insulation layer can be removed and put into water. If the material floats above the water surface, it is definitely not low-smoke halogen-free material. Know to use low smoke zero halogen cable is good, but still on the market at present there are too many fake inferior cables, committing in the selling point of low smoke zero halogen, if don't understand distinguish true low smoke zero halogen flame retardant cable and bought substandard of defective, it will not only give us when using the use of inconvenience, as well as great potential safety hazard, so be sure to understand correctly distinguish between low smoke zero halogen cables.

The copper material always has a residual oxide film at the external temperature, and this oxide film is formed on the high-temperature, continuously cast copper rod when the copper wire enters the hot rod rolling stage.Oxide films are harmful because they cause many defects in the wire drawing process, such as excessive wear of the wire drawing film, poor solderability, and weak adhesion between enamel film and bare conductor. Drawing die is an important tool for wire production, it is the key to realize normal continuous drawing and ensure the quality of drawn products.To make the drawline to obtain high quality stretch products, not only depends on the raw materials and the drawline die itself material, but also depends on the mold groove design and use of other conditions.At present, with the wide application of high-speed wire drawing machine, the use of wire drawing die plays an important role in the process of wire drawing. In the actual production process of copper wire drawing, there are many kinds of wire drawing lubricants. Their performance varies greatly, which seriously affects the quality of wire rod. Therefore, in order to improve the quality of wire rod and save cost, it is particularly important to choose and use wire drawing lubricants reasonably and correctly. To achieve the above purpose, requires the lube oil base stability, good emulsification, with excellent lubricity, cooling and cleaning, easy to put the copper powder filter with precipitation, always maintain the best in the whole process of lubrication state, so that can form a layer of thin film under high pressure without being destroyed, reduce the friction of work area, improve the quality of drawing.Different lubricants have different advantages and disadvantages, and their use time should be decided according to different characteristics. The annealing of copper single wire is one of the important processes in the production of wire and cable. The electrical property, mechanical property and surface quality of the wire depend largely on the annealing process and production mode. One of the important characteristics of metal plastic deformation is work hardening.With the increase of the degree of deformation, all the indexes in the deformation wave, such as yield limit, strength limit and hardness, increase, while the plasticity indexes, such as elongation rate and section reduction rate, also increase the resistance and decrease the thermal conductivity.This will have a bad effect on the drawing. A cable is a mechanical operation that takes advantage of the plasticity of the material.Machinery used for this purpose may be direct or accumulation, this machine is called wire drawing machine or wire drawing machines, it includes a series of fixed anchor mold, placed between each thread die carrier to make the wire to keep certain tension, wire drawing machine to pull the wire pull mode, the final drawing operation is controlled by a pull force applied behind the mold to complete, after the coil through the wire received.