Quality assessment method for oil-immersed electric contact component

Abstract

The invention discloses a quality assessment method for an oil-immersed electric contact component, and the method comprises the steps: evaluating the reasonability of the structural design of the electric contact component based on structural parameters and a force-contact resistance mapping relation of the electric contact component; thermal expansion micro displacement of the plug-in structure is simulated, a micro wear test is carried out, and the wear resistance of the electric contact component is examined by combining the contact resistance of the electric contact component and the coating thickness after the test; carrying out a cyclic thermal shock test on the electric contact part, observing whether the plating layer has layering and cracks or not through metallographic phase after the test, and checking the adhesion of the plating layer of the electric contact part; a high-temperature tube furnace test is carried out under the working condition that the electric contact part is pressed, and the high-temperature creep resistance of the electric contact part is evaluated by combining mechanical and metallographic detection; and carrying out an accelerated corrosion test on the electric contact part, and detecting and evaluating the corrosion resistance and the coating density of the electric contact part by adopting SEM-EDS after the test. According to the invention, a systematic and scientific quality assessment method is formed for the electric contact part, and the potential safety hazard of an ultra-high voltage power transmission project can be reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of power equipment fault assessment, and in particular to a quality assessment method for oil-immersed electric contact components on the side of an ultra-high voltage converter transformer valve. Background Art

[0002] Oil-immersed electrical connection components are key current-carrying connections between the lead-out wires of the valve-side windings of UHV converter transformers and the valve-side bushings. As the "main artery" and "experimental field" of domestic UHV DC transmission, the earliest converter stations in the western region have recently experienced excessive DC resistance values ​​on the valve side of converter transformers due to the degradation of oil-immersed strap contacts, causing a total of 6 bipolar high-end converter transformers to be shut down for 3 months, resulting in significant economic losses. At present, 1,344 valve-side bushings in the domestic UHV DC converter stations in operation use the same strap connection structure. As the operating time increases, the continuous degradation of oil-immersed electrical connections will pose a serious safety hazard to UHV transmission projects.

[0003] At present, the design method of the electrical connection components in the elevated seat area on the UHV converter transformer valve side in the UHV DC transmission project of the State Grid Corporation is directly determined by the transformer and bushing manufacturers. The recent frequent failures indicate that the existing electrical connection components in the elevated seat area on the converter transformer valve side lack a systematic and scientific assessment method. Therefore, it is necessary to propose a quality assessment method for oil-immersed electrical contact components based on relevant experimental and theoretical research results. Summary of the invention

[0004] The purpose of the present invention is to provide a quality assessment method for oil-immersed electrical contact components in view of the current situation that there is a lack of scientific and systematic assessment methods for oil-immersed electrical contact components. The method evaluates the rationality of the structural design, the wear resistance of the coating, the adhesion of the coating, the creep resistance and the corrosion resistance of the electrical contact components, thereby forming a systematic and scientific quality assessment method for the electrical contact components and reducing the safety hazards of ultra-high voltage power transmission projects.

[0005] The present invention is achieved through the following technical solutions:

[0006] The present invention provides a quality assessment method for an oil-immersed electrical contact component, comprising the following steps:

[0007] S1. Obtain the inflection point of the force-contact resistance mapping relationship curve of the electrical contact component, and evaluate the rationality of the structural design of the electrical contact component in combination with the geometric parameters of the plug-in structure;

[0008] S2. Simulate to obtain the micro-displacement of the electrical contact parts caused by the thermal expansion of the plug-in structure, carry out micro-displacement wear test, and evaluate the wear resistance of the electrical contact parts in combination with the contact resistance and coating thickness of the electrical contact parts after the test;

[0009] S3. Carry out cyclic thermal shock test on electrical contact parts. Cut the cross section of the electrical contact parts after the test and use metallographic microscope to observe whether the coating has delamination and cracks, and evaluate the adhesion of the coating on the electrical contact parts.

[0010] S4. Carry out high-temperature tube furnace test under pressure condition of electrical contact parts, compare the force-compression mapping curve of electrical contact parts, the hardness of stainless steel skeleton and the metallographic grain size of stainless steel skeleton before and after the test, and evaluate the high-temperature creep resistance of electrical contact parts;

[0011] S5. Carry out accelerated corrosion tests on electrical contact parts. After the test, use SEM-EDS to detect the surface morphology and surface elements of the electrical contact parts to assess the corrosion resistance and coating density of the electrical contact parts.

[0012] As a preferred embodiment of the present invention, in step S1, a contact resistance measuring device is used to obtain a compression amount-contact resistance mapping curve of an electrical contact component, and a tangent method is used to obtain an inflection point of contact resistance change; based on the force-compression amount mapping relationship and the geometric parameters of the plug-in structure, it is determined whether the contact resistance of each contact piece of the electrical contact component on the plug-in structure is in a stable range under eccentric conditions.

[0013] As a preferred embodiment of the present invention, in step S2, the thermal expansion displacement of the plug-in structure under different operating currents is obtained based on the electro-thermal-static simulation, the wear test stroke is clarified, and 10,000 micro-motion wear tests are carried out. After the test, it is judged whether the wear resistance of the coating meets the requirements based on the coating thickness in the wear area of ​​the electrical contact parts and the contact resistance at the working height.

[0014] As a preferred solution of the present invention, a lower convection heat dissipation coefficient is taken, and the heating power of the plug-in structure under full load and 0.1 times the rated current is obtained based on electro-thermal simulation. This power is introduced into static simulation to calculate the expansion displacement of the plug-in structure caused by the change in load current.

[0015] As a preferred embodiment of the present invention, after the fretting wear test, the contact resistance of the electrical contact component at the working height should be lower than 3 times the initial contact resistance; the cross section of the electrical contact component is detected by metallographic method, and there should be no cracks in the coating of the electrical contact component on the cross section, and the remaining coating thickness should still be greater than 5μm.

[0016] As a preferred embodiment of the present invention, in step S3, the electrical contact component is placed in a 200° C. vacuum tube furnace for 30 minutes, taken out and placed in ice water below 10° C. for rapid cooling, and the operation is repeated 5 times, and then the coating of the electrical contact component is observed to see whether there is cracking or stratification, so as to determine whether the adhesion of the coating meets the requirements.

[0017] As a preferred embodiment of the present invention, in step S4, after the electrical contact component is placed in a working compression state by the electrical contact component tooling, the electrical contact component is placed in a 400°C vacuum tube furnace for 48 hours. After the test, the force-compression curve of the electrical contact component cannot show obvious attenuation, and the hardness of the stainless steel and its metallographic grain size should remain basically unchanged.

[0018] As a preferred embodiment of the present invention, the electrical contact component tooling includes two stainless steel pressure plates arranged opposite to each other, and a plurality of stainless steel support blocks arranged between the two stainless steel pressure plates, wherein the height of the stainless steel support blocks is consistent with the working height of the electrical contact component, and also includes a bolt and nut assembly for applying a clamping force to the two stainless steel pressure plates relative to each other.

[0019] As a preferred embodiment of the present invention, in step S5, a simulated corrosion test platform for electrical contact components is constructed, and test oil with a DBDS concentration of 200 mg / kg is configured to accelerate the corrosion of electrical contact components at an oil temperature of 180° C. for 24 hours.

[0020] As a preferred embodiment of the present invention, SEM-EDS is used to detect the surface morphology and surface elements of the electrical contact component after the test. If there is no Cu element on the surface of the electrical contact component, it means that the coating of the electrical contact component is relatively dense, no pitting corrosion occurs, and the corrosion resistance meets the assessment requirements.

[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0022] In the present invention, the electrical contact components are evaluated from the perspectives of structural design rationality, coating wear resistance, coating adhesion, creep resistance, and corrosion resistance through steps S1-S5, thereby forming a systematic and scientific quality assessment method for the electrical contact components and reducing the potential safety hazards of UHV power transmission projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0024] Figure 1 is a flow chart of the quality assessment method of the oil-immersed electrical contact component in this embodiment;

[0025] Figure 2 is the contact resistance measuring device in this embodiment;

[0026] Figure 3is the electrical contact component compression amount-contact resistance curve and the contact resistance stable range in this embodiment;

[0027] Figure 4 is the compression amount of each electrical contact component when the plug in this embodiment is eccentric;

[0028] Figure 5 is the coating thickness and cracks in the wear area in this embodiment;

[0029] Figure 6 It is the coating delamination phenomenon in this embodiment;

[0030] Figure 7 is a structural diagram of the electrical contact component tooling in this embodiment;

[0031] Figure 8 is the metallographic structure of the stainless steel before and after the tube furnace test in this embodiment;

[0032] Fig. 9 It is the accelerated corrosion test platform in this embodiment;

[0033] Fig.10 This is the SEM-EDS test result of the electrical contact component in this embodiment after pitting corrosion occurs.

[0034] Marks and corresponding parts names in the attached drawings:

[0035] 1-pressing plate, 2-pressing head, 3-band fixing copper ring, 4-micrometer slide, 5-power supply anode hole, 6-power supply cathode hole, 7-DC power supply. DETAILED DESCRIPTION

[0036] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0038] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0039] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0040] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists, A and B exist at the same time, and B exists. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0041] In the embodiments of the present application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width and other dimensions of various components in the embodiments of the present application shown in the drawings, as well as the overall thickness, length, width and other dimensions of the integrated device are only exemplary descriptions and should not constitute any limitation to the present application.

[0042] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces), unless otherwise clearly and specifically defined.

[0043] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0044] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0045] like Figure 1 The flowchart of the quality assessment method in the present application is shown. A quality assessment method of an oil-immersed electrical contact component provided in an embodiment of the present application comprises the following steps:

[0046] S1. Obtain the inflection point of the force-contact resistance mapping relationship curve of the electrical contact component, and evaluate the rationality of the structural design of the electrical contact component in combination with the geometric parameters of the plug-in structure;

[0047] S2. Simulate to obtain the micro-displacement of the electrical contact parts caused by the thermal expansion of the plug-in structure, carry out micro-displacement wear test, and evaluate the wear resistance of the electrical contact parts in combination with the contact resistance and coating thickness of the electrical contact parts after the test;

[0048] S3. Carry out cyclic thermal shock test on electrical contact parts. Cut the cross section of the electrical contact parts after the test and use metallographic microscope to observe whether the coating has delamination and cracks, and evaluate the adhesion of the coating on the electrical contact parts.

[0049] S4. Carry out high-temperature tube furnace test under pressure condition of electrical contact parts, compare the force-compression mapping curve of electrical contact parts, the hardness of stainless steel skeleton and the metallographic grain size of stainless steel skeleton before and after the test, and evaluate the high-temperature creep resistance of electrical contact parts;

[0050] S5. Carry out accelerated corrosion tests on electrical contact parts. After the test, use SEM-EDS to detect the surface morphology and surface elements of the electrical contact parts to assess the corrosion resistance and coating density of the electrical contact parts.

[0051] The present application adopts the scheme in the above steps S1-S5 to evaluate the electrical contact components from the perspective of structural design rationality, coating wear resistance, coating adhesion, creep resistance and corrosion resistance, thereby forming a systematic and scientific quality assessment method for electrical contact components and reducing the safety hazards of ultra-high voltage power transmission projects.

[0052] In an embodiment of the present application, in step S1, a contact resistance measuring device is used to obtain a compression amount-contact resistance mapping curve of an electrical contact component, and a tangent method is used to obtain an inflection point of the contact resistance change; based on the force-compression amount mapping relationship and the geometric parameters of the plug-in structure, it is determined whether the contact resistance of each contact piece of the electrical contact component on the plug-in structure is in a stable range under eccentric conditions.

[0053] The above-mentioned contact resistance measuring device can refer to part of the contents in the public patent "A Continuous Current Corrosion Simulation System for Elastic Contact Finger" applied by Hu Shihong, Wang Fangqiang, etc., with application number 2023102450859, and the applicant is the State Grid Sichuan Electric Power Company Electric Power Research Institute. Specifically, the device consists of a pressure plate 1, a pressure head 2, a strap fixing copper ring 3, a micrometer slide 4, a power anode hole 5, a power cathode hole 6 and a DC power supply 7, such as Figure 2 It should be noted that Figure 2 The above is only an example of a possible solution for the contact resistance measurement device.

[0054] The electrical contact component compression-contact resistance mapping curve (such as Figure 3 As shown in the figure, the electrical contact components have a stable contact resistance range. Combined with the specific dimensions of the plug and socket of the plug structure, the range of the compression amount of each contact piece of the electrical contact component under the condition of full eccentricity (one side of the plug is completely in contact with the socket) is evaluated (such as Figure 4 If the compression of each contact piece is within the stable range, the structural design is reasonable.

[0055] In an embodiment of the present application, in step S2, the thermal expansion displacement of the plug-in structure under different operating currents is obtained based on the electro-thermal-static simulation, the wear test stroke is clarified, and 10,000 micro-motion wear tests are carried out. After the test, it is determined whether the wear resistance of the coating meets the requirements based on the coating thickness in the wear area of ​​the electrical contact component and its contact resistance at the working height.

[0056] In the embodiment of the present application, a lower value of 30W / (m 2 ·℃), the heat dissipation coefficient of the plug-in structure under full load and 0.1 times the rated current was obtained based on the electro-thermal simulation, and the power was introduced into the static simulation to calculate the expansion displacement of the plug-in structure caused by the change of load current. The micro-motion wear tester in Liu Xinlong's doctoral thesis "Study on the Influence of Micro-motion Wear Performance under Electrical Contact Conditions" was used to carry out 10,000 wear tests on the electrical contact parts under the corresponding expansion displacement.

[0057] In the embodiments of the present application, after the fretting wear test, the contact resistance of the electrical contact component at the working height should be less than 3 times the initial contact resistance; the cross section of the electrical contact component is detected by metallographic method, and there should be no cracks in the coating of the electrical contact component on the cross section, and the remaining coating thickness should still be greater than 5μm. The morphology of the unqualified coating after wear is as follows: Figure 5 shown.

[0058] In the embodiment of the present application, in step S3, the electrical contact component is placed in a 200°C vacuum tube furnace for 30 minutes, taken out and placed in ice water below 10°C for rapid cooling, and the operation is repeated 5 times. Then, a cross section of the electrical contact component is prepared, and the coating of the electrical contact component is observed to see if there is cracking or delamination, so as to determine whether the coating adhesion meets the requirements. Figure 6 shown.

[0059] In the embodiment of the present application, in step S4, after the electrical contact component is put into a working compression state by the electrical contact component fixture, the electrical contact component is placed in a 400°C vacuum tube furnace for 48 hours. After the test, the force-compression curve of the electrical contact component cannot show obvious attenuation, and the hardness of the stainless steel and the grain size of its metallographic structure should remain basically unchanged. Figure 8 shown.

[0060] In the embodiment of the present application, the electrical contact component tooling includes two stainless steel pressing plates arranged opposite to each other, and a plurality of stainless steel support blocks arranged between the two stainless steel pressing plates, wherein the height of the stainless steel support blocks is consistent with the working height of the electrical contact component, and further includes a bolt and nut assembly for applying a pressing force to the two stainless steel pressing plates. Figure 7 A possible electrical contact component tooling is shown.

[0061] In the embodiment of the present application, in step S5, a simulated corrosion test platform for electrical contact components is built, and a test insulating oil with a concentration of 200 mg / kg DBDS is configured to accelerate the corrosion of electrical contact components for 24 hours at an oil temperature of 180°C. The simulated corrosion test platform for electrical contact components can refer to the corrosion test platform in the paper "Deterioration Failure Mechanism of Oil-Immersed Band Contact Finger on UHV Converter Transformer Valve Side" by Huang Zhicheng et al., such as Fig. 9 shown.

[0062] In the examples of the present application, SEM-EDS is used to detect the surface morphology and surface elements of the electrical contact component after the test. If there is no Cu element on the surface of the electrical contact component, it means that the coating of the electrical contact component is relatively dense, no pitting corrosion occurs, and the corrosion resistance meets the assessment requirements. Fig.10 Shown are the surface morphology and surface element detection results of electrical contact parts after pitting corrosion.

[0063] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A quality assessment method for oil-immersed electrical contact components, characterized in that: The following steps are involved: S1. Obtain the inflection point of the force-contact resistance mapping relationship curve of the electrical contact component, and evaluate the rationality of the structural design of the electrical contact component in combination with the geometric parameters of the plug-in structure; S2. Simulate to obtain the micro-displacement of the electrical contact parts caused by the thermal expansion of the plug-in structure, carry out micro-displacement wear test, and evaluate the wear resistance of the electrical contact parts in combination with the contact resistance and coating thickness of the electrical contact parts after the test; S3. Carry out cyclic thermal shock test on electrical contact parts. Cut the cross section of the electrical contact parts after the test and use metallographic microscope to observe whether the coating has delamination and cracks, and evaluate the adhesion of the coating on the electrical contact parts. S4. Carry out high-temperature tube furnace test under pressure condition of electrical contact parts, compare the force-compression mapping curve of electrical contact parts, the hardness of stainless steel skeleton and the metallographic grain size of stainless steel skeleton before and after the test, and evaluate the high-temperature creep resistance of electrical contact parts; S5. Carry out accelerated corrosion tests on electrical contact parts. After the tests, use SEM-EDS to detect the surface morphology and surface elements of the electrical contact parts to assess the corrosion resistance and coating density of the electrical contact parts.

2. The quality assessment method of oil-immersed electrical contact components according to claim 1, characterized in that: In the step S1, a contact resistance measuring device is used to obtain a compression amount-contact resistance mapping curve of an electrical contact component, and a tangent method is used to obtain an inflection point of contact resistance change; based on the force-compression amount mapping relationship and the geometric parameters of the plug-in structure, it is determined whether the contact resistance of each contact piece of the electrical contact component on the plug-in structure is in a stable range under eccentric conditions.

3. The quality assessment method of oil-immersed electrical contact components according to claim 1, characterized in that: In step S2, the thermal expansion displacement of the plug-in structure under different operating currents is obtained based on the electro-thermal-static simulation, the wear test stroke is determined, and 10,000 micro-motion wear tests are carried out. After the test, whether the wear resistance of the coating meets the requirements is determined based on the coating thickness in the wear area of ​​the electrical contact component and its contact resistance at the working height.

4. The quality assessment method of oil-immersed electrical contact components according to claim 3, characterized in that: Taking a lower convection heat dissipation coefficient, the heating power of the plug-in structure under full load and 0.1 times the rated current is obtained based on electro-thermal simulation. This power is introduced into the statics simulation to calculate the expansion displacement of the plug-in structure caused by the change of load current.

5. The quality assessment method of oil-immersed electrical contact components according to claim 3, characterized in that: After the micro-motion wear test, the contact resistance of the electrical contact parts at the working height should be lower than 3 times the initial contact resistance; the metallographic method is used to detect the cross-section of the electrical contact parts. There should be no cracks in the coating of the electrical contact parts on the cross-section, and the remaining coating thickness should still be greater than 5μm.

6. The quality assessment method of oil-immersed electrical contact components according to claim 1, characterized in that: In step S3, the electrical contact component is placed in a 200° C. vacuum tube furnace for 30 minutes, taken out and placed in ice water below 10° C. for rapid cooling, and the operation is repeated 5 times to observe whether the coating of the electrical contact component has cracks or delamination, so as to determine whether the adhesion of the coating meets the requirements.

7. The quality assessment method of oil-immersed electrical contact components according to claim 1, characterized in that: In step S4, after the electrical contact component is put into a working compression state by the electrical contact component fixture, the electrical contact component is placed in a 400° C. vacuum tube furnace for 48 hours. After the test, the force-compression curve of the electrical contact component should not show obvious attenuation, and the hardness of the stainless steel and its metallographic grain size should remain basically unchanged.

8. The quality assessment method of oil-immersed electrical contact components according to claim 7, characterized in that: The electrical contact component tooling includes two stainless steel pressure plates arranged opposite to each other, and a plurality of stainless steel support blocks arranged between the two stainless steel pressure plates, wherein the height of the stainless steel support blocks is consistent with the working height of the electrical contact component, and also includes a bolt and nut assembly for applying a clamping force to the two stainless steel pressure plates relative to each other.

9. The quality assessment method of oil-immersed electrical contact components according to claim 1, characterized in that: In the step S5, a simulated corrosion test platform for electrical contact components is constructed, and test oil with a DBDS concentration of 200 mg / kg is prepared to accelerate the corrosion of the electrical contact components at an oil temperature of 180° C. for 24 hours.

10. The quality assessment method of oil-immersed electrical contact components according to claim 9, characterized in that: After the test, SEM-EDS is used to detect the surface morphology and surface elements of the electrical contact parts. If there is no Cu element on the surface of the electrical contact parts, it means that the coating of the electrical contact parts is relatively dense, no pitting corrosion occurs, and the corrosion resistance meets the assessment requirements.

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