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1. Principle of power acquisition by collection unit The fault indicator acquisition unit uses the electromagnetic induction principle of "moving electricity generates magnetism, and moving magnet generates electricity" to generate electricity on the secondary coil through the electromagnetic coupling of the permalloy core. Voltage and current realize the transmission of electric power and achieve the purpose of drawing electricity from the conductor. As shown in the figure, when a primary current flows through the primary winding N1, an alternating magnetic flux Φ1 is generated in the core magnet. This alternating magnetic flux Φ1 passes through the core magnetic circuit and generates an induced voltage value U on the secondary winding. Compared with other electromagnetic mutual inductance transformations, the primary winding here is a cable or wire, and the number of turns is 1 turn. When the alternating magnetic flux Φ1 forms a closed loop in the magnetic core, it will be hindered by magnetic resistance Φr, magnetic space radiation (magnetic leakage ΦL), etc. Part of the magnetic flux will be lost, and only this part of the magnetic flux that passes through the secondary winding Φ2 can effectively transfer electric energy to the secondary side, that is, Φ1=ΦL+Φr+Φ2. It can be seen that under the same working conditions, the smaller the reluctance Φr and magnetic leakage ΦL, the greater the power output by the secondary side will be. Since the permalloy magnetic core acquisition unit needs to meet the requirements of live installation and disassembly, the magnetic core needs to adopt the cutting and snapping mode, that is, the magnetic core needs to be cut into two halves during production and then closed to form a ring magnetic circuit during installation. When the magnetic circuit is closed, an air gap will be generated due to the cutting gap. Compared with the original annular core, its magnetic resistance Φr and magnetic leakage ΦL are greatly increased. Under the same working conditions, the better the cutting process, the smaller the air gap, and the smaller the magnetic resistance. The smaller the resistance Φr and magnetic leakage ΦL will be, the greater the secondary side output power will be. In order to reduce the magnetic circuit loss and increase the secondary side output power level under the same wire current, it is necessary to use magnetic core materials with high magnetic permeability and high saturation magnetic flux density Bs value, making the selection of magnetic core materials tend to be high-end. . After our many experiments, the materials that meet the power extraction requirements of the fault indicator collection unit are: permalloy 1J85, iron-based nanocrystal 1K107.   Physical Properties/Magnetic Properties of Magnetic Materials: 2. The relationship between magnetic flux and power/correlation calculation between theoretical formulas: (1)Φ1=B*Ae (2)B=μ*H (3)μ=AL*Le/0.4*π* N²*Ae(N²=1) (4) H=0.40π*N*I/Le in: μ: magnetic permeability B: Magnetic flux density Ae: core cross-sectional area H: magnetic field strength AL: inductance coefficient Le: equivalent magnetic circuit length It can be seen that at the same primary side current, the higher the magnetic permeability μ, the shorter the equivalent magnetic path length Le of the magnetic core, the larger the core cross-sectional area Ae, and the larger the primary side magnetic flux Φ1.   In order to minimize the losses of Φr and ΦL after the magnetic flux on the primary side is transferred to the secondary side, it is necessary to reduce the reluctance loss and magnetic leakage loss, that is, to increase the magnetic permeability, optimize the effective magnetic path length of the magnetic core, and adopt excellent technology to ensure The cut surfaces of the core fit snugly. In our actual processing practice, the magnetic permeability of 1K107 iron-based nanocrystalline magnetic core after cutting can reach more than 15,000, and the magnetic permeability of 1J85 permalloy magnetic core after cutting can reach more than 12,000. What is the magnetic permeability of permalloy core after cutting? To be broken down in the next episode.   3. Analysis of the reasons for burnt power coil Since the power coil works under power frequency conditions, if the magnetic core is properly designed, the iron loss caused by the eddy current in the magnetic core will not be too large, so the permalloy magnetic core will not burn out. The situation is mainly caused by improper design of the secondary winding. When the operating current on the primary side of the fault indicator rises, the output current on the secondary side will also rise accordingly, that is, I1:I2 =N1:N2 is satisfied. Therefore, it is necessary to consider the winding copper wire according to the possible continuous maximum current on the primary side conductor. The wire diameter and current density on the winding should not be too large, otherwise high heat will be generated on the winding, causing the coil to burn out.   4. Example application 1J85 (0.2mm permalloy) and 1K107 (0.025mm iron-based nanocrystal) are both ultra-high permeability soft magnetic materials. Under power frequency conditions, the eddy current loss is almost negligible. In the current fault indicator acquisition unit In power applications, its excellent magnetic properties are unmatched by other permalloy core magnetic materials. The price of magnetic cores between 1J85 and 1K107 is about 2:1. In large-volume applications, 1K107 has outstanding magnetic performance advantages and price advantages.

Regarding the relationship between the number of core turns and the transformation ratio of a current transformer, this question mainly involves the core-type transformer. According to relevant experiments, it is known that the ratio of its primary current and secondary current is equivalent to the number of primary turns. Inversely proportional to the secondary turns ratio. In other words, if the number of core turns of this transformer is 1 turn, its transformation ratio is 500/5; if the number of core turns is 2 turns, the transformation ratio becomes 250/5. The transformation ratio changes with the change in the number of core turns.   Based on this relationship, we can also calculate the current of the current transformer, which can be used to control the size of the current transformer based on the current to prevent the equipment from being burned due to excessive current.   The relationship and calculation of current transformer ratio and number of turns   Calculation of current transformer ratio and number of turns   Some current transformers have lost their factory nameplates during use. When the user's load changes and the current transformer ratio must be changed, the transformer must first be tested to determine the maximum primary rated current of the transformer, and then the ratio change must be carried out as needed. and calculation of turns.   For example, a current transformer with a maximum primary rated current of 150A needs to be used in a 50/5 transformer application. The formula is converted into the number of primary core turns = the maximum primary rated current of the current current transformer/the primary current of the transformer to be converted. =150/50=3 turns, which is converted into a 50/5 current transformer, and the number of core turns at one time is 3 turns.   The maximum primary rated current can be calculated for this purpose. For example, the transformation ratio of the original current transformer is 50/5 and the number of core turns is 3. If you want to convert it into a 75/5 transformer for use, you should calculate it first. Output the maximum primary rated current: Maximum primary rated current = primary current in the original application × original number of core turns = 50 × 3 = 150A, the number of core turns after conversion to 75/5 is 150/75 = 2 turns That is, when the original 50/5 current transformer with 3 core turns is converted into a 75/5 current transformer, the strain stress of the core turns is 2 turns. Another example is that the original 50/5 current transformer with 4 core turns needs to be used as a 75/5 current transformer. We first calculate the maximum primary rated current as 50×4=200A. After conversion, The number of turns for threading the core should be 200/75≈2.66 turns. When threading the core, the number of turns can only be an integer, either 2 turns or 3 turns.   When we pass through 2 turns, the primary current has become 200/2=100A, resulting in a 100/5 transformer, which causes a deviation. The deviation is (original transformation ratio - current transformation ratio) / current transformation ratio = (15-20)/20=--0.25, which is -25%. In other words, if you still calculate the electricity consumption according to the 75/5 ratio, you will undercount the electricity consumption by 25%. And when we use 3 turns, we will eventually overcount the customer's electricity consumption. Since its primary current becomes 200/3=66.66A, a 66.6/5 transformer is produced, and the deviation is (15-13.33)/13.33=0.125, that is, 12.5% is overcalculated when measuring the electrical energy based on the 75/5 transformation ratio. of electricity. Therefore, when we do not know the maximum primary rated current of the current transformer, we cannot casually replace the ratio, otherwise it may cause errors in measurement verification.   The relationship between the current transformer ratio and the number of core turns   The relationship between the current transformer ratio and the number of turns. For a core-type transformer, the ratio of its primary current to the secondary current is equivalent to the inverse ratio of the ratio of the primary turns to the secondary turns;   Transformer, with 1 turn through the core, the transformation ratio is 500/5; with 2 turns through the core, the transformation ratio is 250/5;   Primary current/secondary current=500/5=100/1=number of secondary turns/number of primary turns (number of secondary turns is 100 turns);   There are 2 turns in the core, the number of secondary turns/the number of primary turns = 100/2 = primary current/secondary current, the secondary current is 5A, and the primary current can be calculated to be 250A;   In other words, if the number of core turns changes, the applied transformation ratio changes, but the transformer itself does not change, and its secondary turns number does not change, it is still 100 turns;   Another optimization algorithm is:   Primary current × number of core turns = primary current when the core turns 1 (here 250A × 2 = 500A)   If the factory nameplate only says 150/5, it means that the primary side of this transformer (one wire across the transformer) can only allow a current pass of no more than 150 amps. If it exceeds, the transformer will be burned. However, in actual applications, the current on the primary side may not necessarily meet the current standard of 150 A, but the requirement of 150 A current magnetic induction can be obtained based on calculations, such as 75/5, 50/5, 30/5.150/5. The current on the primary side is 150 A, and the secondary output is 5 A. The transformation ratio is 150 divided by 5, which is equivalent to 30 times, 75/5, 50/5, 30/5 and so on. 75 requires 2 loops; 50 requires 3 loops; 30 requires 5 loops. In other words, to meet the requirement of outputting 5 amps on the secondary side, the primary side must have a current induction of 150 amps. If the primary side can only be 75 amps, then after two turns, 75*2 will satisfy the primary side. The 150 A current is magnetically induced, and so on for the others.   It can be seen that knowledge in these aspects is very important. If it can be mastered very well, it can have a certain maintenance effect on the current transformer. If you need to know more about this and obtain such products, please contact Hemei Electronics Company.

Why can't the current transformer be opened when it is running? What is the principle? What are the adverse effects of opening a circuit?   Most welders often hear this sentence: "The secondary side of the current transformer cannot be open-circuited, and the secondary side of the voltage transformer cannot be short-circuited." At work, everyone must regard this as the "Quran". When disassembling the secondary line of the current transformer, first add a short rotor or short wiring to connect the secondary side, and then perform surgical removal or wiring work. , Only in this way can the safety of the person be guaranteed, which is a very appropriate approach. When I removed the current wire of the electric meter before, I encountered a situation where the wiring was not firm and the terminals were crackling with charge and discharge. So why can't the secondary current transformer be open circuited? What is the principle? What adverse effects will it cause? The following is a detailed analysis for everyone, I hope everyone can understand it. When the current transformer is working normally, the load connected to the secondary coil is an ammeter or meter current coil and a smart transmitter, etc. The impedance of these coils is not large, and most of them operate in short circuit conditions. Fault conditions. In this case, the magnetic flux generated by the primary current of the current transformer and the secondary coil current cancel each other, keeping the magnetic flux density in the core at a moderate level, usually at a few tenths of a Tesla ( The unit of magnetic flux density: T), because the secondary coil resistor is not large, the operating voltage of the secondary coil is also very low. Under normal operating conditions, the magnetic fluxes of current transformers cancel each other, and the relative density of the magnetic fluxes is not large. When the secondary winding of the current transformer is open-circuited, if the primary current does not change, the secondary circuit is broken, or the resistor is very large, then the current on the secondary side is 0, or very small, and the secondary coil Or the magnetic flux of the iron core is not large and cannot offset the primary magnetic flux. At this time, all the primary current turns into self-induced electromotive force, saturating the iron core. This change is sudden, called a sudden change, and its magnetic flux density reaches several Teslas.   Adverse effects of secondary open circuit of current transformer   When this kind of situation occurs, it will cause the following adverse effects:   1. The second generation of thousands of volts of voltage (this has not been certified, it is a copied theory), the high voltage will penetrate the insulation layer of the current transformer, causing the entire substation equipment casing to be induced and electrified, and will also It will cause electric shock accidents to maintenance workers and threaten their lives.   2. A sudden change in the saturation state of the iron core will increase the core loss of the voltage transformer, and the iron core will become hot and damage the voltage transformer.   3. The saturated iron core of the voltage transformer is in a saturated state, the measurement calibration is inaccurate, and the CT ratio difference and angle difference increase. 

The current transformer is an instrument that converts the large current in the primary side circuit into a small current that can be measured by the secondary side ammeter. It is mainly used for current monitoring and measurement or measurement of electrical energy.   Introduces the monitoring and measurement of current: Current monitoring and measurement is divided into two forms, one is ammeter detection of current; the other is thermal overload protection measurement.   The wiring method for ammeter to detect current is as shown below: Current transformer circuit diagram The P1 terminal of the current transformer in the figure is connected to the ammeter A1, and the A2 terminal is connected in series with the P2 terminal of the transformer and is grounded.   How to short-circuit other unused transformers? As we all know, the secondary side of the current transformer must not be opened. Because the current transformer is a step-up transformer, in an open circuit state, high voltage will be generated on the secondary side, which may easily cause electric shock to the human body. Therefore, the secondary side must be short-circuited when not in use. The simplest method is to connect the P1 and P2 terminals directly with a 2.5mm wire.   How to replace P1 and P2 when they are reversely connected? When the P1 terminal is connected to the P2 terminal, just connect the P1 and P2 terminals back to their original positions.   Hemei Electronics is committed to the research and development, production and sales of amorphous, nanocrystalline and permalloy magnetic core products. Its main products are: nanocrystalline strips, ultra-microcrystalline iron cores, ultra-microcrystalline magnetic cores, Permalloy cores, high-power transformer cores, nanocrystalline magnetic ring inductors, electromagnetic ring coils, switching transformers, common mode inductors, precision current transformers and other products have good stability and high electrical parameters. advantage.   Read more:  https://www.hemeielectricpower.com/

In power engineering, current transformers convert large currents into small currents and are used for the protection, measurement and measurement of power systems. Today I will explain to you how to choose a current transformer.   The technical conditions for current transformer selection and verification include: primary circuit voltage, primary circuit current, secondary load, secondary circuit current, accuracy level and transient characteristics, relay protection and measurement requirements, dynamic stability multiple, thermal Stability factor, mechanical load and temperature rise. In addition to the above technical conditions, it should also be calibrated according to the use environment: ambient temperature, maximum wind speed, relative humidity, pollution, altitude, earthquake intensity and system wiring method.   The rated primary voltage of the current transformer should not be less than the rated primary voltage of the circuit, which is generally the nominal voltage of the system instead of the highest working voltage.   The rated primary current of the current transformer is an important and difficult point in the selection. Generally, it can be selected according to the rated current or maximum operating current of the primary equipment to which it belongs. The standard values of the rated primary current are: 10A, 12.5A, 15A, 20A, 25A, 30A, 40A, 50A, 60A, 75A and their decimal multiples or decimals. The primary current of the current transformer winding for measurement and metering should be selected strictly according to the loop operating current. In actual use, the transformation ratio difference on each side of the current transformer connected to the main transformer and busbar differential protection should not be greater than 4 times.   As shown in Figure 1, for each circuit of the 35kV bus of a 50MVA booster station, the rated current of the main transformer circuit is 866A, the outlet circuit is 600A, the reactive power compensation circuit is 300A, and the rated current of the station transformer circuit is 10A. Because the rated current of the station transformer loop is very small, the primary current of the protection level winding of the current transformer of this loop is 1/4 times the current of the main transformer side; the primary current of the main transformer loop is selected as 1000A, and the primary current of the protection level of the station transformer loop is optional. It is 250A. Considering the consistency of the transformer ratio, the primary current of the station transformer circuit protection level can be selected as 300A, and the measurement and measurement is generally selected as 50A.   When the high-voltage side of the main transformer is a directly grounded system, the primary rated current of the neutral point current transformer should be 50% to 100% of the rated current of the high-voltage side of the transformer, and meet the specified error limit. The rated primary current of the discharge gap zero-sequence current transformer of the neutral point complete device should be selected according to 100A.   The cores of the current transformers on each side used for transformer differential protection and differential protection of the same busbar should have the same core form.   For P and PR class current transformers, they are only required to meet steady-state non-saturation, while TP class current transformers are required to be non-saturated throughout the entire working cycle.   The above is the current transformer selection compiled by the editor based on specifications and actual engineering experience. Please also pay attention to the reference in practical applications.   Read more:  https://www.hemeielectricpower.com/

Motor energy saving and core material development Today, it can be said that more than half of the total global electricity consumption comes from motors. High-efficiency motors are urgently needed to control carbon dioxide emissions and thereby curb global climate warming. The key to achieving this high-efficiency motor is the core material. The core material of the motor, as the name implies, is made of iron-containing materials. The core material is made of magnets and plays an important role in controlling the magnetic flux of the motor (forming a magnetic field), but it also becomes a source of heat due to iron losses (hysteresis loss and eddy current loss). So, will it be possible to achieve high efficiency of the motor by choosing a core material with small iron loss? Not so. Core materials have many properties. Moreover, even the same core material has different required properties when used in motors and when used in transformers. In recently developed high-efficiency motors, amorphous alloys are used instead of non-oriented electromagnetic steel sheets as core materials, and combined with ferrite magnets, ultra-high efficiencies previously thought to be impossible have been achieved. This article will explain the selection and use of motor core materials based on this case.   Core materials can be divided into two categories   Core materials are also called soft magnetic materials. Figure 1 shows the main soft magnetic materials.   What kind of motor core material is better? If there is no heating effect of iron loss, using soft magnetic materials with large Bs in the core can obtain the maximum magnetic flux density Bm of the core. In addition, the volume of the core is inversely proportional to the square of Bm. From the perspective of miniaturization, materials with large Bs also have advantages. On the other hand, from the perspective of improving efficiency, soft magnetic material cores with small iron losses are preferred. Therefore, high-quality soft magnetic materials with high Bs and low iron loss located in the lower right area of Figure 2 are needed. However, as shown in Figure 2, there is a compromise between high Bs and low iron loss, and the ideal soft magnetic material that can satisfy both does not exist. It can also be seen from Figure 2 that when the frequency is 1kHz, in terms of high Bs, Perminde alloy has advantages; in terms of low iron loss, nanocrystalline soft magnetic alloy and PC-type permalloy (high magnetic permeability material) are more advantageous. Advantage.   Comparing iron-based amorphous materials and non-oriented electrical steel sheets Comparison of the initial magnetization curves of iron-based amorphous alloy SA1 and non-oriented electromagnetic steel plate 35H300 is shown in Figure 3. For SA1, in order to relax the stress exerted on the alloy during casting, the magnetic properties can be improved through magnetic field-free heat treatment in a nitrogen atmosphere. However, since SA1 will become embrittled under heat treatment, heat treatment is mostly not performed when used in motors. When it exceeds B-0.8T, the magnetizing field strength of SA1 becomes greater than that of 35H300 (the magnetic permeability becomes smaller).   Evaluate core processing Figure 4 shows the iron loss comparison between SA1 and 35H300 slotted and cut cores without heat treatment. In the case of 400Hz and B.=1.0T, the iron loss of the SA1 core is 2Wkg and the iron loss of the 35H300 core is 20Wkg. The former is 1/10 of the latter. Based on this, it is extremely effective in improving the efficiency of motors, such as in battery-driven motors, and has the effect of extending battery life. In addition, the higher the driving frequency, the greater the iron loss difference between the two. This situation also applies to high-speed motors. Figure 5 shows the structure of an 11kW double-rotor axial gap motor, which uses an SA1 stator core and a ferrite sintered magnet rotor. The stator core is a simple structure in which amorphous alloy SA1 is cut into long strips, laminated, and fixed with resin. It is a slit-cut core. The stator core is made of non-oriented electromagnetic steel plates of the same shape, which are cut into long strips and then laminated and fixed with resin to obtain another motor. The loss comparison between it and the motor shown in Figure 5 is shown in Figure 6. Compared with the 35H300 stator core, the SA1 stator core can reduce the iron loss by 1/5. In addition, by reducing the excitation current, the copper loss can be reduced by about 15%, reaching an efficiency of 93.2% in line with the IE4 standard. Furthermore, on the basis of this motor, the characteristics of amorphous alloy are fully utilized, which is smaller than the traditional three-phase induction motor. A high-efficiency motor that meets the IE5 standard is being developed.   Read more:  https://www.hemeielectricpower.com/

Background: Nowadays, China has made great progress in terms of life, economy and science and technology, among which the electric power industry is the most obvious. The domestic electric power industry has now set a benchmark in the international industry.Under the strategic goals of "power Internet of Things" and "digital grid", comprehensive monitoring of the status of the power grid has become an important step in realizing the digitalization and intelligence of the power grid. In this process, the application scenarios of power detection and monitoring equipment have become increasingly complex, the scale has gradually increased, and the demand for safe and stable power supply has also continued to increase. However, current transmission line monitoring equipment mainly supplies energy through wiring power supply or solar + energy storage power supply. It faces severe challenges such as high cost, frequent manual maintenance, and poor reliability, which seriously restricts the promotion, application and development of online transmission line monitoring equipment. .   In order to solve the problem of power supply for power detection and monitoring equipment, we will take you to learn about one of the safer energy supply solutions for equipment in the current power industry - passive source of electromagnetic induction energy!   When it comes to passive source of power, I believe the first thing that pops up in everyone’s mind must be the wireless charging function used on smartphones! In principle, the understanding is correct, but compared with the technology of passive source of electricity, the fields of application are essentially different. The former is currently suitable for medium, high and low voltage transmission lines. Passive source power is referred to as CT power extration, which mainly consists of three components: magnet core, power module and electrical equipment.   CT power extraction is based on the principle of electromagnetic induction, which induces energy from power lines in a non-electrical connection. The magnetic core material is processed into the required shape (usually a ring shape) through a special process, and the AC wire is passed through the inner hole of the magnetic core material. The magnetic core will sense the magnetic field around the wire and pass through the magnetic ring coil. Electric energy is induced, and after the electric energy is converted into AC/DC power through the coil end, a DC regulated power supply is output. (The magnetic core can be processed into a closed-loop or open-close structure according to requirements)   Features: 1. Stable power supply - The CT power supply device can be externally attached to the wire to provide stable power output, and can realize self-protection under short circuit and surge current, and achieve long-term stable operation with low heat consumption. It is a safe and reliable power supply method. 2. Wide application - The magnetic core of the CT power taking device can be specially customized according to different working environments. It has excellent waterproof, moisture-proof, high temperature resistance and other characteristics, and can be stable even in complex and severe weather such as rain and snow. , effective power supply. 3. Compact size - CT power extraction device has high power density, small size and light weight, which can greatly reduce the air resistance on overhead lines and reduce the load-bearing capacity of the line.   Application Environment: 1. Suitable for conventional medium voltage or low voltage transmission lines 2. Suitable for underground mines or tunnels 3. Overhead cables, underground branch cables, branch boxes, etc. 4. Rail transit electric traction system Product related companies: CT power extraction is a necessity derived from the development of the power industry. Currently, the quality of products produced by domestic manufacturers is uneven. Among them, Hefei Hemei Electronics Technology Co., Ltd., a leading material manufacturer, is an example: Hemei Electronics is a A leading domestic designer and manufacturer specializing in the research and development of electromagnetic signal coupling and magnetoelectric power conversion technology, it has been committed to promoting the progress and development of magnetoelectric signal coupling measurement technology, passive self-power supply technology, and mid-range wireless power transmission technology.   Hemei Electronics mainly produces passive self-powered (CT power supply) devices and CT power supply modules. Ultra-high-precision AC measurement sensors, permalloy cores, magnetic shielding boxes, etc.   The products are mainly used in passive power supply of intelligent sensing equipment, passive power supply AC measurement of AC power supply systems such as power and railways and monitoring equipment, amplification and isolation of carrier communication signals in smart home systems, etc.

Power supply companies use digital technology to develop and apply a fully functional fault location system by comprehensively processing and integrating fault alarm data, real-time operational data, offline data, grid structure, equipment parameters and many other information on the distribution network.   1 Background The power supply company under the jurisdiction of 95 10kV lines, in 2017 due to fault tripping caused by the grid eight events 43, an average of 0.45 / article, while the average time to find the fault event 136 minutes, the line fault outage has seriously affected the reliability of power supply and power supply service capacity. 2018 Weinan Power Supply Company stipulates that the distribution network eight grid events are strictly controlled within 14 times, the production management of distribution networks Requirements are higher, and in this regard, the Xintong operation and inspection class combined with the demand for small current connection fault diagnosis, based on the first half-wave grounding line selection principle, using wireless communication technology, data acquisition technology, computer technology, the development and application of the distribution network grounding fault location device.   2 Innovation Points The device is innovative in terms of reliability, availability, advancement and maintainability: maintenance-free. The internal use of large-capacity, long-life disposable lithium batteries, with CT power extraction, power extraction current to the supercapacitor charging, supercapacitor to the RF wireless communication module power supply; fault detection, load collection function integration. When a line fault occurs, it detects the type of grounding and short-circuit faults to achieve fault location. During normal operation of the line, load and voltage information is uploaded at regular intervals; Ground fault detection with direction. On the basis of collecting line current and capacitance current, it collects relative ground voltage, increases the criterion of voltage and direction, eliminates the false action caused by excitation inrush current, and greatly improves the correct rate of grounding detection; two-way wireless communication. With local wireless frequency division, frequency hopping network and remote GPRS ‘four remote’ two-way interactive communication dual maintenance function; integrated multi-technology fault indicator. Unconventional technical means to solve a series of problems such as machine power consumption, communication energy, self-power supply, fault detection, fault recording, online monitoring, high current impact, high and low temperature, protection level, lightning surge, EMC, volume, weight and so on.   3 Achieve benefits Economic benefits. After the implementation of the project, each line trip or grounding can reduce the accident point in a wide range, reduce manual patrol 2 man-days, each man-day 200 yuan, 2 × 200 = 400 yuan, reduce vehicle costs 100 yuan, a total of 500 yuan, according to the 128 flat line road grounding and tripping 58 times in the whole year of 2014, the annual savings of 29,000 yuan; change the traditional fault handling mode, reduce the fault processing time, effectively controlling the scope and time of the fault. The average outage time within the application area of the pilot project construction is reduced from 20.84 hours to 6.85 hours, and the annual power supply is increased by 313,568,000 kWh, which can directly generate economic benefits of 171,500 yuan according to the average price of electricity of 0.5471 yuan/kWh. Social benefits. After the implementation of this project, significant economic benefits have been achieved in addition to effectively improving power supply reliability, and the project has been awarded the First Prize of Science and Technology by Weinan Power Supply Company.   4 Outlook The distribution network line ground fault location device has been fully applied in State Grid Pucheng County Power Supply Company, and 19 sets of related devices have been deployed in Pucheng County power grid, providing a good basis for the operation of Pucheng power grid line equipment. As a useful attempt of 10 kV distribution network line fault diagnosis, the distribution network ground fault location device has explored the principle of fault routing, communication channels, power solutions, etc., which provides a theoretical and practical basis for further improvement of the fault indication device, and the continuous improvement in the field of fault diagnosis and localisation is an important supplement to realise the high-reliability and low-cost of distribution automation at the level of the agricultural network. The development prospect is huge.   Read more:  https://www.hemeielectricpower.com/

A current sensor is a detection device that detects current information, converts it into electrical signals that meet certain standards or other signals that can be analyzed, and performs operations such as transmitting, storing, and displaying these signals.   Current measurement can meet current monitoring, control, analysis and other requirements. For example, during the use of power supply, it is necessary to monitor the current, activate automatic protection devices in time when overcurrent, overvoltage, etc. occur, or help realize intelligent control to avoid equipment damage. In addition, current monitoring is equally important during the power supply technology upgrade process. Therefore, power supply technology using current sensors has gradually become a development trend.   Current sensors generally have the characteristics of high sensitivity, high temperature stability, strong anti-interference, and low power consumption. They can realize power measurement and current control, thereby monitoring energy systems and protecting power systems. According to different principles, current sensors can be divided into several categories such as electromagnetic current transformers, electronic current transformers, and fiber optic current sensors. Among them, the electronic current transformer sub-product Hall current sensor is the mainstream of the market, with demand accounting for than more than 50%.   Current sensors can be widely used in electronics, home appliances, new energy vehicles, new energy power generation, smart grids, industrial equipment, medical equipment and other fields. Among them, in the field of new energy vehicles, current sensors are indispensable and are widely used in battery management systems BMS, current distribution units PDU, motor controllers, on-board chargers OBC, DCDC converters, charging piles, etc.; in the field of medical equipment , many devices need to accurately control the current passing through the device to ensure patient safety and device safety, and high-precision current sensors are required.   According to the "2023-2028 China Current Sensor Industry Market In-depth Research and Development Prospects Forecast Report", with the continuous expansion of application fields and the continuous advancement of downstream industry technology, the performance of current sensors continues to upgrade, and the market development space continues to increase. In 2022, the global current sensor market will be approximately 18.9 billion yuan; it is expected that the global current sensor market will grow at a compound annual growth rate of approximately 8.1% from 2022 to 2028, and the market size will reach 30.2 billion yuan by 2028.   Industry analysts said that after continuous development, the number of current sensor manufacturers in my country is increasing. However, my country still has deficiencies in the development of high-precision current sensors, and there is still room for greater progress in the industry in the future.   Read more:  https://www.hemeielectricpower.com/

The zero-sequence current transformer is an important instrument in the power system and is used to measure the zero-sequence current in the power system. The power system is composed of three phases, namely A, B, and C. Each phase can operate independently. However, in power systems, there is a current called zero sequence current that exists in three phases simultaneously. With zero-sequence current transformers, we can measure this current to ensure proper operation of the power system. The difference between a current transformer and a zero-sequence current transformer is the type of current measured. Typically, current transformers are used to measure on-load current or load current, while zero-sequence current transformers are used to measure zero-sequence currents in power systems. Therefore, the zero-sequence current transformer needs to have special structure and measurement capabilities to ensure accurate measurement of the zero-sequence current. current transformer power supply split core current transformer current transformer coils   1. Zero sequence current In power systems, there is a current called zero sequence current that exists in three phases simultaneously. Zero sequence current is caused by various factors and should not exist as it may cause system failure or equipment damage. In power systems, the importance of measuring and monitoring zero-sequence currents is self-evident. To clearly understand zero sequence current, let us look at the basics of the system. The power system consists of three phases, including phase A, phase B and phase C. Under normal conditions, these phases should have equal voltages and currents, resulting in a balanced system. However, under certain circumstances, such as faults or unbalanced loads, zero-sequence currents may occur in the power system. Zero-sequence currents are caused by unpaired charges, which can be any number of charges scattered throughout the system or present in ungrounded equipment or cables. If there are unpaired charges or ungrounded devices in the system, current imbalances and zero-sequence currents can result.   2. Working principle of zero sequence current transformer The main function of the zero-sequence current transformer is to measure the zero-sequence current in the power system and output the corresponding electrical signal. Its working principle is very simple: when a current flows in the cable through the transformer, the transformer generates a magnetic field proportional to the current. This magnetic field is then passed to a current sensor and generates a corresponding current signal.   3. Application of zero sequence current transformer Zero sequence current transformers have many applications including: 1. Power system protection: In the power system, zero sequence current can be used as a fault indicator to detect and protect equipment in the power system. 2. Power quality monitoring: Zero sequence current can be used to monitor the quality of the power system and indicate problems and faults in the power system. 3. Ground fault detection: Ground fault is a common fault type in power systems. By using zero-sequence current transformers, fault conditions present in equipment that are not paired with charges or are not grounded can be detected.   4. Conclusion In short, the zero-sequence current transformer is an important measuring device in the power system and is used to detect the zero-sequence current in the power system. Unlike current transformers, zero-sequence current transformers require special structure and measurement capabilities to ensure accurate measurement of zero-sequence current. Zero-sequence current transformers can be used in power system protection, power quality monitoring, ground fault detection and other fields, and play a very important role in the power system.   Read more:  https://www.hemeielectricpower.com/

Relay protection generally consists of three parts: measurement part, logic part and execution part. The function of the measurement part is to measure the physical quantity of the working state of the protected component and compare it with the given setting value to determine whether the protection should be activated. The function of the logic part is to make the protection device work according to a certain logic program based on the size, nature, order of appearance, etc. of each output of the measurement part, and finally pass it to the execution part. The function of the execution part is to complete the task of the protection device according to the signal sent by the logic part. Such as sending a signal, tripping or not acting, etc. Classification of relay protection 1) Classification according to the protected objects: transmission line protection, generator protection, transformer protection, busbar protection, motor protection, etc. 2) Classification according to protection principles: current protection, voltage protection, distance protection, differential protection, direction protection, zero sequence protection, etc. 3) Classification according to the type of faults reflected by the protection: phase-to-phase short-circuit protection, ground short-circuit protection, inter-turn short-circuit protection, disconnection protection, out-of-step protection, loss of excitation protection and over-excitation protection, etc. 4) Classification according to the implementation technology of relay protection devices: electromechanical protection, rectifier protection, transistor protection, integrated circuit protection, and microcomputer protection. 5) Classification of the relationship between relay protection measured value and set value: over-protection (measured value > set value), under-protection (measured value > set value) 6) Classification according to the role of protection: main protection, backup protection, auxiliary protection, etc. Main protection: protection that reflects the fault of the protected component itself and removes the fault in the shortest possible time. Backup protection: Protection used to remove faults when the main protection or circuit breaker refuses to operate. It is further divided into near backup protection and far backup protection. Near backup protection: Install two sets of protection at this component. When the main protection refuses to operate, the other set of protection of this component will act. Remote backup protection: When the main protection or circuit breaker refuses to operate, the backup protection is implemented by the protection of adjacent power equipment or lines.   Principle analysis of relay protection devices Relay protection devices include a measurement part (and a fixed value adjustment part), a logic part, and an execution part. 1. Sampling unit It electrically isolates the physical quantities (parameters) in the operation of the protected power system and converts them into signals that can be accepted by the comparison and identification unit in the relay protection device. It is composed of one or several sensors such as current and voltage transformers. 2. Comparative identification unit Including a given unit, the signal from the sampling unit is compared with the given signal to determine what signal the next-level processing unit sends out. (Normal state, abnormal state or fault state) The comparison and identification unit can be composed of 4 current relays, two of which are quick-break protection and the other two are over-current protection. The setting value of the current relay is the given unit. The current coil of the current relay receives the current signal from the sampling unit (current transformer). When the current signal reaches the current setting value, the current relay acts and passes to the next level through its contacts. The processing unit sends a signal that causes the circuit breaker to eventually trip; if the current signal is less than the set value, the current relay does not act, and the signal transmitted to the downstream unit does not act. The information of "quick break" and "over current" of the identification and comparison signal is sent to the next unit for processing. 3. Processing unit It accepts the signal from the comparison and identification unit, processes it according to the requirements of the comparison and identification unit, and determines whether the protection device should act according to the size, nature, and order of combinations of the outputs of the comparison link; it is composed of time relays, intermediate relays, etc. . Current protection: quick break---intermediate relay action, overcurrent, time relay action. 4. Execution unit Fault handling is implemented through execution units. Execution units are generally divided into two categories: one is a sound and light signal relay; (such as an electric whistle, an electric bell, a flashing signal light, etc.) and the other is the opening coil of the operating mechanism of the circuit breaker to open the circuit breaker. 5. Control and operating power supply The relay protection device requires its own independent AC or DC power supply, and the power of the power supply increases or decreases depending on the number of devices controlled; the AC voltage is generally 220V or 110V.   Read more:  https://www.hemeielectricpower.com/

Compared with traditional silicon steel, iron-based amorphous alloys have the advantages of high saturation magnetization, low iron loss and low coercive force, making them an ideal choice for soft magnetic materials. Iron-based amorphous alloys have attracted the attention of many researchers due to their excellent mechanical strength, high thermal stability and corrosion resistance. At present, iron-based amorphous alloys have been widely used in fields such as marine engineering and power electronics. However, with the deepening of engineering applications, further optimizing the amorphous formation ability and soft magnetic properties of iron-based alloys has become one of the main research directions. Heavy rare earth elements Gd and Dy can reduce the Curie temperature of iron-based metallic glass, increase magnetic entropy change and refrigeration capacity, and are suitable for the production of low-cost magnetic refrigeration materials. Of course, the addition of rare earth elements will also affect the amorphous oxidation performance. Rare earths have a strong affinity for oxygen and are therefore easily oxidized, which limits their applications. Studying the oxidation mechanism of rare earth-containing amorphous alloys plays an important guiding role in expanding their application scope. Wei Bingbo and others from Northwestern Polytechnical University improved the amorphous formation ability of the ternary Fe73B22Nb5 alloy by adding Gd element. The effect of Gd element content on the thermal stability and room temperature magnetic properties of the alloy was clarified, and the mechanism of rare earth elements in the alloy oxidation process was systematically revealed, providing an optimization solution for the composition design of iron-based amorphous alloys. Relevant research results will be published online in Acta Physica Sinica in March 2024.   This work was funded by the National Key Research and Development Program, the National Natural Science Foundation and the Shaanxi Provincial Natural Science Foundation. Read more:  https://www.hemeielectricpower.com/