Magnetic shielding structure for hydropower station transformer and preparation method and application thereof

Abstract

The invention belongs to the technical field of power equipment magnetic shielding, and particularly provides a magnetic shielding structure for a hydropower station transformer and a preparation method and application thereof.The magnetic shielding structure comprises a magnetic shielding structure base body and a coating covering the surface of the magnetic shielding structure base body, and the coating is prepared through a cold spraying technology; the coating comprises the following components: iron, nickel, copper, polyurethane and an inorganic fluorescent compound. The coating is prepared through the cold spraying technology, the advantages of being high in deposition efficiency, high in bonding strength, simple in procedure and high in reliability are achieved, meanwhile, the production technology of the magnetic shielding structure can be effectively simplified, the production efficiency is improved, the prepared coating can effectively prevent magnetic induction lines from directly passing through, and the application range is wide. Therefore, the influence of an external magnetic field on the internal space is reduced, and the magnetic shielding effect is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic shielding for electrical equipment, and particularly relates to a magnetic shielding structure for a hydropower station transformer, a preparation method thereof, and an application thereof. Background Art

[0002] In a hydropower station, electrical equipment is the core element to ensure its normal operation. The stable operation of electrical equipment is not only related to the power generation efficiency of the hydropower station, but also directly affects the safety and stability of the power system. The magnetic shielding structure of hydropower station electrical equipment is crucial for key equipment such as the excitation system and transformers.

[0003] During the generator short-circuit characteristic test and the generator short-circuit thermal stability test of Units 13#, 6#, and 8# of the Xiluodu Hydropower Station, individual steel components near the generator outlet and the generator neutral point heated up. For example, the temperature of the upper fixing bolts of the air cooler below the generator outlet and the upper ring plate of the stator frame reached 130 - 160°C, and the temperature of individual fixing points on the CT support platform at the generator neutral point reached 95 - 130°C, which did not meet the Xiluodu mechanical and electrical installation standard (the temperature of the generator stator frame should not be greater than 75°C). The existence of this heating point poses a hidden danger to the long-term safe and stable operation of the unit. Through the analysis and research of the actual measurement data and the structural characteristics of the generator, it is concluded that the main reason for the component heating is that the magnetic leakage shielding is imperfect, resulting in a large eddy current in the component.

[0004] If the magnetic shielding structure cannot effectively play its role, it will not only interfere with the surrounding electrical equipment and affect its normal operation, but also may lead to an increase in energy loss and a reduction in the efficiency of the power system. Currently, in order to solve the problem of magnetic field leakage of transformers, magnetic shielding structures are usually prepared using materials such as aluminum plates, silicon steel sheets, or permalloys. The main purpose is to reduce the leakage magnetic flux, avoid local overheating, and improve the efficiency and reliability of the transformer.

[0005] CN110556959A discloses a new electromagnetic shielding structure under a strong electromagnetic environment of a giant hydrogenerator, including multiple layers of silicon steel sheets and one layer of aluminum plate arranged in parallel and laminated and adhered; the multiple layers of silicon steel sheets and one layer of aluminum plate are sequentially laminated and fixedly connected to form an integrated shielding structure; it is used to prevent the reinforced concrete structure in the machine pit wall from overheating under a strong electromagnetic environment and the situation of reduced structural strength caused by overheating.

[0006] On the one hand, there is still room for improvement in the shielding effect of traditional magnetic shielding structures. Facing the complex electromagnetic environment of a hydropower station, existing magnetic shielding materials often cannot completely and effectively block magnetic field leakage, resulting in some magnetic field leakage into the surrounding environment and interfering with other equipment.

[0007] On the other hand, existing preparation methods have problems in terms of process complexity, reliability, etc. Some preparation methods are cumbersome, requiring multiple processes and complex equipment, which increases production costs and production cycles. At the same time, the magnetic shielding structures obtained by some preparation methods may experience performance degradation, structural damage, etc. during long-term use, affecting their reliability and service life.

[0008] In summary, the existing magnetic shielding structures and their preparation methods for hydropower station transformers cannot fully meet the actual application requirements. There is an urgent need for a new magnetic shielding structure and its preparation method to improve the shielding effect, reduce costs, and enhance reliability, so as to better adapt to the special environment and working requirements of hydropower stations. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a magnetic shielding structure for hydropower station transformers, its preparation method and application, which can effectively prevent the direct passage of magnetic induction lines, improve the magnetic shielding effect, have a simple process, and improve production efficiency.

[0010] To solve the above technical problems, the technical solution adopted by the present invention is: a magnetic shielding structure for hydropower station transformers, including a magnetic shielding structure matrix and a coating covering the surface of the magnetic shielding structure matrix, and the coating is prepared by a cold spraying process; the components of the coating include iron, nickel, copper, polyurethane, and inorganic fluorescent compounds.

[0011] In a preferred embodiment, the mass ratio of iron, nickel, copper, polyurethane, and inorganic fluorescent compounds in the coating is 40~60:20~30:3~5:3~7:4~14.

[0012] In a preferred embodiment, the inorganic fluorescent compounds include one or a combination of several of calcium fluoride, potassium fluoride, boron nitride, and zinc sulfide.

[0013] In a preferred embodiment, the thickness of the coating is 100~1000 μm, the coating is a multi-layer structure, each layer of the coating is a grid surface, and the grid surfaces of adjacent layers are staggered and overlapped.

[0014] In a preferred embodiment, the material of the magnetic shielding structure matrix is aluminum or silicon steel or copper or iron-nickel alloy.

[0015] The present invention also provides a preparation method for a magnetic shielding structure for hydropower station transformers, including the following steps: S1. Clean the magnetic shielding structure matrix of the transformer with acetone; S2. Using iron, nickel, copper, polyurethane, and inorganic fluorescent compounds as raw materials, prepare a coating on the surface of the matrix by a cold spraying process, and iron, nickel, copper, polyurethane, and inorganic fluorescent compounds are in powder form.

[0016] In a preferred embodiment, in step S2, the iron powder is spherical or irregular in shape, with a particle size of 5 to 70 μm; the nickel powder is spherical or irregular in shape, with a particle size of 5 to 70 μm; the polyurethane powder is granular, with a particle size of 10 to 80 μm; and the inorganic fluorescent compound powder is spherical-like, with a particle size of 10 to 45 μm.

[0017] In a preferred embodiment, in step S2, before spraying, the spraying surface is subjected to glow discharge treatment; the interval between the glow discharge treatment and the start time of cold spraying does not exceed 40 min.

[0018] In a preferred embodiment, in step S2, the parameters of the cold spraying process are as follows: the working gas is one or more of air, nitrogen, and helium; the spraying pressure of the cold spraying is 1 to 7.5 Mpa, the spraying temperature is 100 to 1000 °C, the gas velocity of the cold spraying is 150 to 1200 m / s, and the spraying distance is 5 to 110 mm.

[0019] The present invention also provides an application of the preparation method of the magnetic shielding structure for a hydropower station transformer, applying the above-mentioned preparation method of the magnetic shielding structure for a hydropower station transformer to the preparation or surface repair of the magnetic shielding structures of generators and transformers.

[0020] The magnetic shielding structure for a hydropower station transformer, its preparation method, and application provided by the present invention have the following beneficial effects: 1. The cold spraying process adopted by the present invention has high deposition efficiency, high bonding strength, simple processes, and high reliability, and can effectively simplify the production process of the magnetic shielding structure and improve production efficiency.

[0021] 2. With iron, nickel, and copper as the main components of the coating, on the one hand, it helps to ensure the high bonding strength of the coating, so as to ensure that the magnetic shielding structure can serve for a long time under relatively harsh working conditions; on the other hand, due to the characteristics of magnetic substances, the electrons inside the coating will be arranged in the direction of the external magnetic field and magnetized by the external magnetic field. This characteristic can effectively prevent the direct passage of magnetic induction lines, thereby reducing the influence of the external magnetic field on the internal space and achieving the effect of magnetic shielding.

[0022] 3. Adding polyurethane with a porous structure to the coating can form a network structure inside the cold spraying coating; since the magnetic field is generated by electric current and has a certain penetration ability, when the magnetic force passes through the polyurethane, it will be blocked by the thermoelectric current and resistance in the polyurethane, forming an effect similar to magnetic resistance, thereby causing the electromagnetic wave to attenuate inside.

[0023] 4. Add a fluorescent substance to the coating. After being excited by energy, electrons are excited to a higher energy level. Subsequently, when returning from the higher energy level to the lower energy level, a fluorescence phenomenon occurs, thereby completing the conversion and release of energy, and then weakening the electromagnetic wave through fluorescence.

[0024] 5. The polyurethane powder and the fluorescent substance can make each other have better dispersion uniformity in the powder, which can improve the stability and performance of the coating after spraying.

[0025] 6. The coating structure is designed as an overlapping network porous structure. When an electromagnetic wave is incident on the front interface between the shielding coating and free space, a part of the wave reflects the electromagnetic wave due to the impedance mismatch between the two media, and numerous multiple reflections and attenuations occur at the rich interfaces inside the material and between the two interfaces; another part of the non-reflected wave propagates into the material, and its intensity decreases exponentially due to attenuation and absorption through various ways such as conductive loss, dielectric loss, and magnetic loss, thereby effectively achieving the magnetic shielding effect. Specific embodiments

[0026] In order to make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the following further details the present invention in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] A magnetic shielding structure for a hydropower station transformer includes a magnetic shielding structure substrate and a coating covering the surface of the magnetic shielding structure substrate. The material of the magnetic shielding structure substrate is aluminum or silicon steel or copper or iron-nickel alloy.

[0028] The coating is prepared by a cold spraying process and is a multi-layer structure. Each layer of the coating is a grid surface, and the grid surfaces of adjacent layers are staggered and overlapped.

[0029] The components of the coating include iron, nickel, copper, polyurethane, and inorganic fluorescent compounds. The mass ratio of iron, nickel, copper, polyurethane, and inorganic fluorescent compounds in the coating is 40-60: 20-30: 3-5: 3-7: 4-14.

[0030] The inorganic fluorescent compounds include one or a combination of several of calcium fluoride, potassium fluoride, boron nitride, and zinc sulfide.

[0031] The preparation method of the above magnetic shielding structure for a hydropower station transformer includes the following steps: S1. Clean the magnetic shielding structure substrate of the transformer with acetone; S2. Use iron, nickel, copper, polyurethane, and inorganic fluorescent compounds as raw materials, and use a cold spraying process to prepare a coating on the surface of the substrate. The iron, nickel, copper, polyurethane, and inorganic fluorescent compounds are in powder form.

[0032] The thickness of the coating is 100 to 1000 layers, each layer of the coating is a grid surface, and the grid surfaces of adjacent two layers overlap staggeredly.

[0033] Before spraying, glow discharge treatment is carried out on the spraying surface; the interval between the glow discharge treatment and the start time of cold spraying does not exceed 40 min.

[0034] The iron powder is spherical or irregular in shape, with a particle size of 5 to 70 μm; the nickel powder is spherical or irregular in shape, with a particle size of 5 to 70 μm, and the powder purity is 99.0% to 99.99%; the polyurethane powder is granular, with a particle size of 10 to 80 μm; the inorganic fluorescent compound powder is spherical-like, with a particle size of 10 to 45 μm, and the powder purity is 99.0% to 99.99%.

[0035] The parameters of the cold spraying process are as follows: the working gas is one or more of air, nitrogen, and helium; the spraying pressure of the cold spraying is 1 to 7.5 Mpa, the spraying temperature is 100 to 1000 °C, the gas velocity of the cold spraying is 150 to 1200 m / s, and the spraying distance is 5 to 110 mm.

[0036] Example 1: In this example, the magnetic shielding structure includes a substrate and a coating covering the surface of the substrate, and the coating is prepared by the cold spraying process; the components of the coating include iron, nickel, copper, polyurethane, and inorganic fluorescent compound.

[0037] The mass ratio of iron, nickel, copper, polyurethane, and inorganic fluorescent compound in the coating is 53:25:5:7:10.

[0038] The polyurethane selected is the TPU powder of BASF in Germany.

[0039] The fluorescent substance is calcium fluoride.

[0040] The preparation method of the magnetic shielding structure for a hydropower station transformer is as follows: S1. Clean the transformer magnetic shielding substrate with acetone; S2. Using iron, nickel, copper, polyurethane, and inorganic fluorescent compound as raw materials, prepare a coating on the surface of the substrate by the cold spraying process.

[0041] The thickness of the coating is 300 μm, the coating is multi-layered, each layer of the coating is a grid surface, and the grid surfaces of adjacent two layers overlap staggeredly.

[0042] The iron powder is spherical or dendritic in shape, with a particle size of 40 to 70 um and a powder purity of 99.9%; the nickel powder is spherical, with a particle size of 10 to 45 um and a powder purity of 99.9%; the polyurethane powder is granular, with a particle size of 30 to 50 um; the fluorescent powder is spherical-like, with a particle size of 10 to 45 um and a powder purity of 99.9%.

[0043] Before the spraying process, glow discharge treatment is carried out on the spraying surface; the interval between the glow discharge treatment and the start time of spraying does not exceed 40 min.

[0044] In step S2, the parameters of the cold spraying process are as follows: the working gas is one or more of air, nitrogen, or helium; the spraying pressure of cold spraying is 3 Mpa; the spraying temperature of cold spraying is 600 °C; the gas velocity of cold spraying is 450 m / s; the spraying distance of cold spraying is 40 mm.

[0045] Example 2: The difference from Example 1 is that: The thickness of the coating is 1000 μm, the coating is multi-layered, each layer of the coating is a grid surface, and the grid surfaces of adjacent layers are staggered and overlapped.

[0046] The iron powder is spherical or dendritic, with a particle size of 10 - 45 μm and a powder purity of 99.99%; the nickel powder is spherical, with a particle size of 10 - 45 μm and a powder purity of 99.99%; the polyurethane powder is granular, with a particle size of 30 - 50 μm; the fluorescent powder is spherical-like, with a particle size of 10 - 45 μm and a powder purity of 99.99%.

[0047] The parameters of the cold spraying process in step S2 are as follows: the working gas is one or more of air, nitrogen, or helium; the spraying pressure of cold spraying is 5 Mpa; the spraying temperature of cold spraying is 700 °C; the gas velocity of cold spraying is 650 m / s; the spraying distance of cold spraying is 30 mm.

[0048] Example 3: The difference from Example 1 is that the fluorescent substance is potassium fluoride.

[0049] Example 4: The difference from Example 1 is that the fluorescent substance is boron nitride.

[0050] Example 5: The difference from Example 1 is that the fluorescent substance is zinc sulfide.

[0051] Comparative Example 1: The difference from Example 1 is that the mass ratio of nickel, copper, polyurethane, and inorganic fluorescent compound in the coating is 78:5:7:10.

[0052] Comparative Example 2: The difference from Example 1 is that the mass ratio of iron, nickel, copper, polyurethane, and inorganic fluorescent compound in the coating is 65:20:5:5:5.

[0053] Comparative Example 3: The difference from Example 1 is that the mass ratio of iron, copper, polyurethane, and inorganic fluorescent compound in the coating is 74:5:7:14.

[0054] Comparative Example 4: The difference from Example 1 is that the mass ratios of iron, nickel, copper, polyurethane, and inorganic fluorescent compound in the coating are 43:35:5:7:10.

[0055] Comparative Example 5: The difference from Example 1 is that the mass ratios of iron, nickel, polyurethane, and inorganic fluorescent compound in the coating are 53:30:7:10.

[0056] Comparative Example 6: The difference from Example 1 is that the mass ratios of iron, nickel, copper, polyurethane, and inorganic fluorescent compound in the coating are 53:20:10:7:10.

[0057] Comparative Example 7: The difference from Example 1 is that the mass ratios of iron, nickel, copper, polyurethane, and inorganic fluorescent compound in the coating are 53:28:5:14.

[0058] Comparative Example 8: The difference from Example 1 is that the mass ratios of iron, nickel, copper, polyurethane, and inorganic fluorescent compound in the coating are 50:25:5:10:10.

[0059] Comparative Example 9: The difference from Example 1 is that the mass ratios of iron, nickel, copper, polyurethane, and inorganic fluorescent compound in the coating are 58:30:5:7:.

[0060] Comparative Example 10: The difference from Example 1 is that the mass ratios of iron, nickel, copper, polyurethane, and inorganic fluorescent compound in the coating are 53:20:5:7:15.

[0061] The performance tests on the specimens prepared in the examples are as follows: Combined with the particularity of the transformer housing and the actual situation of the cold spraying process, due to the special nature of the spraying object, it is impossible to conduct destructive testing. In order to verify the effectiveness of the spraying process and the quality of the coating, the same equipment, the same batch of raw material powder, the same process, and the preparation of accompanying test pieces at continuous time after spraying the product are used, and relevant tests are carried out.

[0062] 1) Magnetic shielding performance test The magnetic shielding performance is measured with reference to the test regulations in the national standard GB / T 44645-2024 "Measurement Method for High-Power Microwave Shielding Effectiveness of Electromagnetic Shielding Materials", specifically: GB / T 18663.3-2020 Mechanical Structures for Electronic Equipment - Tests for Metric and Inch Series - Part 3: Electromagnetic Shielding Performance Tests for Cabinets and Chassis.

[0063] 2) Adhesion strength test The adhesion strength of the coating is measured with reference to the test regulations in the national standard GB / T 38898-2020 "Non-Destructive Testing - Ultrasonic Testing Method for Coating Adhesion Strength".

[0064] The test results are shown in Table 1.

[0065]

[0066] From the comparison of the test results of Comparative Example 1 and Comparative Examples 1-6, it can be seen that taking iron, nickel, and copper as the main components of the coating, on the one hand, it helps to ensure the high bonding strength of the coating, so as to ensure that the magnetic shielding structure can serve for a long time under relatively harsh working conditions; on the other hand, by using the characteristics of magnetic substances, the purpose of preventing the direct passage of magnetic induction lines is achieved, thereby reducing the influence of the external magnetic field on the internal space and achieving the magnetic shielding effect.

[0067] From the comparison of the test results of Comparative Example 1 and Comparative Examples 7-10, it can be seen that the porous polyurethane structure can attenuate the electromagnetic wave emission inside; adding fluorescent substances to the coating can weaken the electromagnetic wave effect. The polyurethane powder and the fluorescent substances can make the dispersion uniformity of each other in the powder better, and can improve the comprehensive properties such as the stability and strength of the coating after spraying.

[0068] The above embodiments are only the preferred technical solutions of the present invention and should not be regarded as limitations to the present invention. The embodiments in this application and the features in the embodiments can be arbitrarily combined with each other without conflict. The protection scope of the present invention should be the technical solutions recorded in the claims, including the equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, the equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A magnetic shielding structure for a hydropower station transformer, characterized in that: The invention comprises a magnetic shielding structure substrate and a coating covering the surface of the magnetic shielding structure substrate, wherein the coating is prepared by a cold spraying process; the components of the coating include iron, nickel, copper, polyurethane and inorganic fluorescent compounds.

2. A magnetic shielding structure for a hydropower station transformer according to claim 1, characterized in that: The mass proportion of iron, nickel, copper, polyurethane and inorganic fluorescent compound in the coating is 40~60:20~30:3~5:3~7:4~14.

3. The magnetic shielding structure for a hydropower station transformer according to claim 1, characterized in that: The organic fluorescent compound includes one or a combination of calcium fluoride, potassium fluoride, boron nitride and zinc sulfide.

4. The magnetic shielding structure for a hydropower station transformer according to claim 1, characterized in that: The coating has a thickness of 100-1000 μm and is a multi-layer structure. Each layer of the coating is a mesh surface, and the mesh surfaces of two adjacent layers are staggered and overlapped.

5. The magnetic shielding structure for a hydropower station transformer according to claim 1, characterized in that: The material of the magnetic shielding structure substrate is aluminum, silicon steel, copper or iron-nickel alloy.

6. The method for preparing a magnetic shielding structure for a hydropower station transformer according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Use acetone to clean the magnetic shielding structure matrix of the transformer; S2. Using iron, nickel, copper, polyurethane and inorganic fluorescent compounds as raw materials, a coating is prepared on the surface of a substrate by a cold spraying process. The iron, nickel, copper, polyurethane and inorganic fluorescent compounds are in powder form.

7. The method for preparing a magnetic shielding structure for a hydropower station transformer according to claim 6, characterized in that: In step S2, the iron powder is spherical or irregular in shape, with a particle size of 5 to 70 μm; the nickel powder is spherical or irregular in shape, with a particle size of 5 to 70 μm; the polyurethane powder is granular in shape, with a particle size of 10 to 80 μm; and the inorganic fluorescent compound powder is quasi-spherical in shape, with a particle size of 10 to 45 μm.

8. The method for preparing a magnetic shielding structure for a hydropower station transformer according to claim 6, characterized in that: In the step S2, before spraying, the spraying surface is subjected to glow discharge treatment; the interval between the glow discharge treatment and the start time of cold spraying is no more than 40 minutes.

9. The method for preparing a magnetic shielding structure for a hydropower station transformer according to claim 6, characterized in that: In step S2, the parameters of the cold spraying process are: the working gas is one or more of air, nitrogen, and helium; the spraying pressure of the cold spraying is 1 to 7.5 MPa, the spraying temperature is 100 to 1000° C., the gas velocity of the cold spraying is 150 to 1200 m / s, and the spraying distance is 5 to 110 mm.

10. Application of a method for preparing a magnetic shielding structure for a hydropower station transformer, characterized in that: The method for preparing a magnetic shielding structure for a hydropower station transformer as described in any one of claims 6 to 9 is applied to the preparation or surface repair of a magnetic shielding structure of a generator or a transformer.

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