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Permalloys often refer to iron-nickel alloys with a nickel content in the range of 30 to 90%. It is a very widely used soft magnetic alloy. Through the appropriate process, the magnetic properties can be effectively controlled, such as the initial permeability of more than 105, the peak permeability of more than 106, the coercivity as low as 2 ‰ Oster, the rectangular coefficient close to 1 or close to 0. The permalloy with a face-centred cubic crystal structure has a very good plasticity, and it can be processed into an ultrathin strip with a 1 μm diameter and a variety of use forms. Commonly used alloys are 1J50, 1J79, 1J85 and so on. 　　1J50 saturation magnetic induction strength is slightly lower than silicon steel, but the permeability is dozens of times higher than silicon steel, iron loss is also 2 to 3 times lower than silicon steel. Made of higher frequency (400 ~ 8000Hz) transformer, no-load current is small, suitable for the production of 100W below the small higher frequency transformer. 1J79 has a good overall performance, suitable for high-frequency and low-voltage transformers, leakage protection switch core, common-mode inductance core and the current transformer core. 1J85 initial permeability can be up to one hundred thousand (105) or more, suitable for making a weak signal low-frequency or high-frequency input/output transformer. 1J85 initial permeability can be up to one hundred thousand (105) or more, suitable for making weak signal low-frequency or high-frequency input/output transformers. It is suitable for use as low frequency or high frequency input/output transformers for weak signals, common mode inductors and high precision current transformers.   Structural Magnetism 　　Permalloy is a kind of iron and nickel alloy with high permeability under weak magnetic field, nickel content in 30% or more nickel-iron alloys, at room temperature for the single-phase face-centred cubic (γ) structure, but in the vicinity of 30% Ni single-phase structure is very unstable, so the practical iron and nickel soft magnetic alloys with nickel content are more than 36%. Iron-nickel alloys in the vicinity of 75% nickel (atomic fraction), in this single-phase alloy will occur in the Ni3Fe long-range ordered transition, when the alloy's fractional constants and physical properties, such as electrical resistivity and magnetism, etc. will change. Therefore, the effect of the ordered transition on the properties has to be considered. Small amounts of additional elements such as Mo or Cu are usually added to Ni3Fe alloys to inhibit the generation of long-range ordering [1] . permalloy alloy materials permalloy transformer core split permalloy coils   Interrelationships 　　Figure 1 illustrates the saturation magnetisation strength Js, Curie temperature Tc, magnetic crystal anisotropy K1 and magnetostriction constant λ of binary Ni3Fe alloys as a function of nickel content. Fig. 2 illustrates K1 and λ of Ni-(Fe+Cu)-Mo alloys as a function of composition and heat treatment cooling rate. Fig. 3 illustrates the variation of uniaxial anisotropy constants Ku1 and Ku2 with nickel content obtained by rolling and magnetic annealing processes. As can be seen from the figure, K1 is not only dependent on the composition, but also related to the short-range ordering of Ni3Fe (controlled by the heat treatment cooling rate). λ is basically determined by the composition, and the cooling rate has a small effect on λ111 and λ100 only at the composition of Ni3Fe. The Ku2 produced by magnetic field heat treatment at temperatures below Tc is an order of magnitude smaller than the Ku1 produced by slip deformation (during cold rolling.) Both Ku1 and Ku2 are uniaxially anisotropic, so that rectangular hysteresis loops are obtained when magnetised along their preferred direction, whereas flattened loops with a low Br are obtained when magnetised along the perpendicular direction. For alloys with 70%~80% Ni, which have K1≤0, the easy magnetisation direction is <111>, and it is necessary to avoid {100}<001> cubic weaving, random weaving with chaotic orientation. And nickel for 45% ~ 68% of the alloy K1>0, easy magnetisation direction is <100>, so in order to obtain high magnetic properties, should try to obtain cubic weave. Specifically can be used in large under pressure cold rolling and lower temperature (900 ~ 1050 ℃) annealing. The annealing of pozzolanic alloys should be carried out in a pure hydrogen atmosphere without oxygen, with a dew point below -40℃, or in an atmosphere with a vacuum of 10-2～10-3Pa.   Classification properties 　　Permalloys can be divided into four major categories according to composition: 35% to 40% Ni-Fe alloys, 45% to 50% Ni-Fe alloys, 50% to 65% Ni-Fe alloys and 70% to 81% Ni-Fe alloys. Each category can be made with a circular hysteresis loop, rectangular hysteresis loop or flat hysteresis loop material.   35%～40% 　　In the range of 35% to 40% nickel content, the magnetocrystalline anisotropy K1 decreases with the increase of nickel content, and the square ratio Br/Bs also becomes smaller, showing a circular hysteresis loop. This circular return line combined with high resistivity (ρ = 60 μΩ-cm at 40% Ni; and ρ = 45 μΩ-cm at 48%) and fine-grain isotropic microstructure results in lower core losses. For example, a 40% Ni-Fe alloy strip with a thickness of 0.05 mm has a loss of 9 watts per kilogram at 0.1 T and 20 kHz; while the corresponding loss for a 48% Ni-Fe alloy strip is 14 watts per kilogram. These alloys are suitable for square wave transformers, DC converters, etc.   45% to 50% 　　Alloys in this composition range have a high saturation magnetisation strength among the Permalloys with K1>0 and a susceptible magnetisation direction of <100>. Rectangular hysteresis loops can be obtained by forming cubic weaves for use in magnetic amplifiers, chokes, and transformers. Circular hysteresis loops can also be obtained by forming a secondary recrystallised {210} weave, or by forming a fine-grained isotropic microstructure with the aid of primary recrystallisation. This alloy has a high permeability and low coercivity and is used in current transformers, ground-fault circuit breakers, micromotors and relays.   50% to 65% 　　Alloys in this composition range have high Curie temperatures and high saturation magnetisation strengths and are in the ordered state K1≈0. Therefore, the magnetic field heat treatment effect is particularly pronounced and can produce strong induced magnetic anisotropy. Low temperature (Curie point below about 130 ℃) magnetic field heat treatment, the hysteresis loop is rectangular, DC permeability is high, but the dynamic characteristics of the poor; high temperature (Curie point below about 60 ℃) magnetic field heat treatment, the square ratio of the return line has decreased, the DC peak permeability is not high, but the dynamic characteristics of the good. Nickel-iron alloy containing about 55% nickel (plus 2% molybdenum) by high-temperature annealing, the formation of {210}<001> weaving structure or fine grain secondary recrystallisation organisation, and then high-temperature longitudinal magnetic field heat treatment, can significantly improve the μi and μm. 65% nickel iron alloy containing nickel with a fine-grained isotropic microstructure of the longitudinal magnetic field heat treatment, you can get a good dynamic characteristic of the rectangular hysteresis loop material, suitable for the magnetic amplifiers. This alloy by transverse magnetic field heat treatment, can get low Br flat-like return line, permeability in a certain range of magnetic field strength changes very little, known as constant permeability alloy, suitable for inductive components.   70%～81% 　　This composition range of Permalloy has high magnetic permeability. Although the binary nickel-iron alloy K1 and λ can not be reduced to zero at the same time, but in this composition range to add the appropriate amount of alloying elements such as molybdenum, chromium, copper, etc., and then through the control of the cooling rate of the heat treatment, it will be able to make K1 and λ at the same time converge to zero, so as to obtain a very high permeability and very low coercivity. Generally this alloy μi up to 40 ~ 60mH / m. In 1947, the Americans Bozorth (R.M. Bozorth) and others with pure raw materials, vacuum melting and in pure hydrogen in 1200 ~ 1300 ℃ annealed at high temperatures, obtained the μi and μm high Ni79Mo5 alloy, called the super-slope Permalloy. Its μi can reach 150mH / m or more, μm up to 1130mH / m. In the late 1960s, Japan's Masumoto amount of 78% Ni-Fe alloys in the addition of niobium, tantalum, and later added the fourth and fifth elements such as molybdenum, chromium, titanium, aluminium, manganese, etc., to obtain a high hardness and high permeability of the pozzolanic alloys, the hardness of its Hv>200, known as hard pozzolanic alloys. These alloys are suitable for making transformers, chokes, magnetic heads, magnetic shields, etc. In addition, this type of alloy through the formation of cubic weaving structure, the return line can also be rectangular; at the same time, control the degree of order of the alloy, so that K1 ≥ 0, it shows good dynamic characteristics, it is very suitable for doing magnetic modulator. Add 2% of 80% ~ 82% Ni-Fe alloy powder made of pressed powder core, with high resistance and good stability, can be used at a frequency of 300Hz.   Learn more :    https://www.hemeielectricpower.com/

With the continuous development of science and technology and the continuous expansion of human activities, microelectronics technology and computer technology have been applied to all aspects of social life. A large number of electrical and electronic products with high technical content and complex internal structures have been widely used, making them increasingly informatized and Electromagnetic sensitization. The impact of complex electromagnetic environment on human beings has attracted more and more attention. Therefore, it is of great significance to study the electromagnetic coupling mechanism.   1. Concepts related to electromagnetic environment The electromagnetic environment refers to the sum of electromagnetic phenomena existing in space. Various man-made electromagnetic radiation and natural electromagnetic radiation constitute a complex electromagnetic environment. Man-made electromagnetic radiation includes mobile phones, radio talkies, radio and television transmitters, satellites, radars, etc., lightning, static electricity, geomagnetic field, sunspots, etc. Activities, cosmic rays, etc. constitute natural electromagnetic radiation sources. The formation of electromagnetic radiation requires the following three elements at the same time: Electromagnetic wave source refers to the components, equipment, systems or natural phenomena that generate electromagnetic waves; Coupling channel refers to the channel or medium that couples or propagates energy from a wave source to a sensitive device and causes the device to respond; Sensitive equipment refers to equipment that responds to electromagnetic waves. These three elements are usually called the three elements of electromagnetic coupling.   2. Coupling method of electromagnetic radiation (1) Antenna coupling All metal conductors exposed to electromagnetic fields can be considered as antennas. "Front-door" coupling refers to the coupling of electromagnetic pulse or microwave energy into the electronic system through the antenna on the target. Therefore, the coupling strength can be calculated based on the design characteristics of the antenna. When the electromagnetic wave frequency is equal to the antenna design frequency, the coupling reaches its peak value. (2) Hole-slit coupling Typically, electronic devices are packaged in containers made of conductive materials. Due to the needs of equipment for heat dissipation, ventilation, gaps, cracks, power feeding, and signal transmission, the container cannot be sealed and there are different types of holes and seams, which provide a coupling path for electromagnetic radiation. "Back-door" coupling means that high-energy electromagnetic pulse energy couples into the system through holes and gaps in the target, interfering with or destroying electronic equipment. When the wavelength is smaller than the hole size, the electromagnetic wave will enter the shield without any obstruction; when the wavelength is larger than the hole size, the electromagnetic wave will be blocked; when there is a hole with a size comparable to the electromagnetic wavelength, the coupling of electromagnetic waves will be serious. Resonance will occur. (3) Coupling of power lines and transmission lines The power cord is a long line exposed outside the system and is vulnerable to electromagnetic energy attacks. It can both receive and transmit interference energy. If there is a power line or signal transmission line connected from the shielded case to the inside of the system, the received and induced current will propagate along the line and enter the shield. Generally, microwave pulse current is propagated. Even if the current is not introduced from the lead of the core wire of the transmission cable, but is induced on the outer shielding layer, it will be coupled to the core wire through the transfer impedance and directly enter the electronic system. For microwaves, the transfer impedance of shielded cables is also much larger than that of radio frequencies, so microwaves can enter the core wires through the braided shielding of power lines and transmission lines. (4) Skin effect of metal shell The penetration of electromagnetic waves into metal shells is achieved through the skin effect. The skin depth of electromagnetic waves in the material is In the formula, f is the frequency of electromagnetic waves, and are the magnetic permeability and electrical conductivity of the metal shell material respectively. For a 2GHz microwave signal, its skin depths in copper (=5.5×107S/m) and aluminum (=3.2×107S/m) are 1.52 and 2.82 respectively. For higher frequency microwave signals, the value of skin depth is smaller.   3. The mechanism of action of electromagnetic energy The impact of electromagnetic hazard sources on high-tech equipment mainly occurs through conduction coupling and radiation coupling of energy. Its mechanism of action can be summarized as the following four aspects: (1) Thermal effect The thermal effect generated by electrostatic discharge and high-power electromagnetic pulse is generally completed in nanoseconds or microseconds, and is an adiabatic process. As an ignition source and detonation source, it can instantly cause the explosion of flammable and explosive gases or electrical pyrotechnics. It can also overheat microelectronic devices and electromagnetic sensitive circuits in the system, causing local thermal damage, circuit performance deterioration or failure, and even Causing inventory materials to burn and explode. (2) Radio frequency interference and "surge" effect Radio frequency interference caused by electromagnetic radiation causes electrical noise and electromagnetic interference to information equipment, causing it to malfunction or malfunction. Strong electromagnetic pulses and their "surge" effects can also cause hard damage to the system, which can not only degrade or invalidate the performance parameters of devices or circuits, but can also form a cumulative effect, burying potential hazards and affecting the usability of circuits or equipment. reduce. (3) Strong electric field effect The strong electric field (especially the electrostatic field) generated by electromagnetic hazards can not only cause the breakdown of the gate oxide layer of the MOS circuit or the dielectric breakdown between metal lines, causing circuit failure, but also cause potential damage to system self-test instruments and sensitive devices. impact on work. (4) Magnetic effect Strong currents caused by electrostatic discharge, lightning strikes, and similar electromagnetic pulses can produce strong magnetic fields, causing electromagnetic energy to be directly coupled into the system and interfering with the normal operation of electronic equipment.   References: [1] Liu Shanghe, Wu Zhancheng: Electromagnetic environment and high-tech weapons and equipment [J]. Modern Military, 2001. [2] Wu Xiong: Environmental issues of electric fields, magnetic fields and electromagnetic fields [J]. Electric Power Environmental Protection, 2007, (4). [3] Gao Yan, Yu Bo: Characteristics of complex electromagnetic environment [J]. Journal of Sichuan Ordnance Industry, 2008, (1). [4] Gao Bin, Tang Xiaobin: Preliminary study on the effects of complex electromagnetic environment [J]. Journal of China Electronics Research Institute, 2008, (4).   Learn more :  https://www.hemeielectricpower.com/

Current transformer is an important secondary device in the power system, widely used in metering, measurement, relay protection and other secondary circuits, in the high current or high voltage occasions we can not directly use the ammeter to measure the current size of the circuit, only through the secondary side of the current transformer to measure, so that it will be safe, then for the parameters of the current transformer, the 0.5 level, 1.0 level, as well as 10P20, 5P20 what does it mean? How do we choose to use it? The following will be carefully explained: 　　First, the principle of the current transformer 　　Current transformer and transformer is based on the principle of electromagnetic induction will be the primary side of the large current into the secondary side of the small current to measure the instrument. Current transformer is composed of a closed core and winding. The primary winding has a small number of turns and is strung in the line of the current to be measured. The secondary side of the winding turns is more, series in the measuring instrument and protection circuit, the current transformer in operation, its secondary side of the circuit is always closed, so the measuring instrument and protection circuit series coil impedance is very small, the current transformer's operating condition is close to a short circuit. 　　Types of current transformers 　　According to the use can be divided into: 　　Measuring current transformer: settlement of electricity costs 　　Measurement current transformer: measuring current, calculate the degree of electricity, etc., the accuracy is generally lower than the machine with two transformers, not as a settlement. 　　Protection current transformer: current speed protection, overcurrent protection, overload protection, etc.; 　　1. calibration current transformer accuracy: 0.1S level. Tolerance of 0.1%, commonly used in calibration measurement level current transformer accuracy.  　　2. measurement of current transformer accuracy: 0.2S 0.5 level. Tolerance of 0.2% and 0.5%, used for electricity billing basis, some occasions will also use the 0.5-level 　　3. Measuring current transformers: 0.5, 1.0, 2.0, etc., generally used for ammeters. 　　4. Protection of current transformer accuracy: 10P10, 10P20, 5P10, 5P20, etc., the meaning of accuracy: 10P10, for example, that is, the current flowing through the current transformer, is within 10 times its rated current, the inductor error within ± 10%. 　　5. In some special occasions, there are more accurate current transformers, there are 0.005 level, 0.05 level, etc., the use of occasions less.   Learn more :  https://www.hemeielectricpower.com/

November 20, this reporter learned from the Chinese Academy of Electric Sciences Wuhan Branch was informed that after two years of technological research, the hospital successfully developed a low-voltage current transformer (i.e., CT) full-range calibration equipment under charged conditions, for the first time with a non-stop state of the low-voltage current transformer to carry out the periodic calibration capacity. At present, the device has been in the State Grid Shanghai Electric Power Company and other units of the pilot application, the follow-up will be carried out in many parts of the country to carry out network operation work. Energized calibration is one of the most widely used techniques in energized operation, capable of accurately diagnosing faulty equipment and effectively detecting operational safety hazards. Previously, the commonly used method was the traditional detection technology relying on power outages, and the time window for power outage detection is difficult to coordinate, which is not conducive to the business environment and power supply reliability; in addition, the use of banding detection means can only detect the error situation of the user's current load point, and can not comprehensively reflect the user's operation process of all the actual error, the accuracy is difficult to ensure. As a measuring instrument, the transformer full-range energized calibration equipment can measure the amplitude and phase errors of the operating low-voltage current transformers in full range in accordance with the national calibration regulations. The technology adopts electromagnetic induction to calibrate the signal coupling and injection of low-voltage CT, without the need to make electrical connection to the running power supply line, and without adding any auxiliary device or module to the original power supply line, which makes the operation process simple and can effectively guarantee the safety of the personnel and the operation of the power grid. Wuhan Branch of the Chinese Academy of Electric Sciences charged calibration research team leader, professor-level senior engineer Zhang Jun told reporters that, in this case, the development of a can be carried out with electricity, high accuracy and high correlation with the traditional volume of transmission system there is a high degree of correlation between the transformer error calibration technology, appears to be very urgent. Since 2022, under the support of the State Grid Corporation, the Chinese Academy of Electric Sciences and the State Grid Shanghai Electric Power Company set up a project team, relying on the national high-voltage metering station, to jointly carry out the "low-voltage CT full-range calibration under electrified conditions" technology research. The research team through the field demand collection, the overall design of the system program, laboratory development and testing, project site debugging, prototype production and other aspects, repeated attempts, continued research, and the results will be completed on the grid pilot, and achieved good results. According to reports, low-voltage CT charged full-range calibration technology successfully implemented, can realize the normalization of low-voltage CT full-range charged calibration business, to ensure the stability of low-voltage CT metering performance, to avoid the user and the State Grid Corporation's power measurement losses. At the same time, it can improve the technical means of measurement and calibration of transformers, without affecting the quality of power supply services, and effectively improve the level of supervision and control of low-voltage CT operation quality.   Learn more :  https://www.hemeielectricpower.com/

Recently, the Chinese Electrical Engineering Society organized from the electric power, optical and other fields of experts, China's first "highly reliable and independent fiber optic current transformer" for technical appraisal. Chen Weijiang, academician of the Chinese Academy of Sciences, as the representative of the industry experts agreed that the project to form a full range of optical current transformer equipment, representing the field of the highest international level of technology, to realize the field of science and technology in the field of self-reliance and innovation beyond the important significance. 　　For a long time, fiber optic current transformer and its core optoelectronic devices are mainly dependent on imports, and because of its face of extreme low temperature, external vibration, strong electromagnetic interference and other complex and harsh operating environment, the failure rate remains high, many times leading to DC blocking and stopping, and has become a constraint on the reliable operation of DC engineering problems. 　　State Grid Corporation, deputy director of the equipment department Guo Xianshan said, "fiber optic current transformer oil-free, gas-free, safe and environmentally friendly, fast response speed, dynamic range, has become the main direction of development of the current measurement in the power system, especially in the DC power transmission project has an irreplaceable role, and its reliability directly affects the safe and stable operation of the system. " 　　In response to the current situation of operational failures in recent years, the Chinese Academy of Electric Sciences, State Grid Jiangsu Electric Power Company composed of a team after more than ten years of technical research, breakthroughs in fiber-optic current transformer polarization optics analysis method and disturbance mechanism, wave piece integrated sensing fiber development process, the core of the reliability of optoelectronic devices to grow the test method, the operational status of intelligent monitoring and early warning technology and other core problems. Finally, successfully developed the first 100% fully localized high reliability independent fiber optic current transformer, temperature, vibration resistance and other key indicators of environmental weathering and reliability of the comprehensive improvement, and ± 800kV Qingnan converter station successfully network operation, marking China's complete solution to the field of optical current measurement of the "neck" The project team has accumulated a lot of experience in this process. In the process, the project team has published 19 standards, 46 invention patents, 49 papers and monographs, and 17 software copyrights.   Learn more :  https://www.hemeielectricpower.com/