In-situ test method and system for breakdown characteristics of micro-area on surface of copper-chromium contact of vacuum arc-extinguishing chamber

Abstract

The invention discloses an in-situ test method and system for the surface micro-area breakdown characteristic of a vacuum arc-extinguishing chamber copper-chromium contact, and the method comprises the steps: preparing a tungsten ball electrode and a copper-chromium contact cylindrical electrode based on a double-beam focused ion beam platform, respectively fixing the tungsten ball electrode and the copper-chromium contact cylindrical electrode on a nanometer manipulator mechanical arm and a sample platform, and placing the tungsten ball electrode and the copper-chromium contact cylindrical electrode in a vacuum cavity; and connecting the test circuits inside and outside the vacuum cavity. The distance between the electrodes is accurately adjusted by using a nano control system, and the specific micro-area on the surface of the contact is accurately positioned by combining an electron beam imaging technology and an ion beam imaging technology. Then, direct-current voltage is applied at a stable position, voltage and current signals in the breakdown process are collected, and surface topography images before and after breakdown are obtained; according to the invention, the in-situ test of the breakdown characteristic of the specific micro-area on the surface of the copper-chromium contact of the vacuum arc-extinguishing chamber is realized, the influence rule of the surface appearance on the breakdown behavior can be revealed, theoretical support is provided for contact surface regulation and control and process optimization, and the method has important significance for improving the insulating property of the vacuum arc-extinguishing chamber and developing a product with a higher voltage grade.

Description

Technical Field

[0001] This invention belongs to the field of vacuum power switch technology, specifically relating to an in-situ testing method and system for the micro-area breakdown characteristics of the copper-chromium contact surface of a vacuum interrupter. Background Technology

[0002] As a core breaking element in medium-voltage power systems, the reliability of vacuum interrupters heavily depends on the performance of their copper-chromium contacts. The breakdown characteristics of the contact material are key parameters determining the insulation recovery capability and service life of the vacuum interrupter. Due to the influence of the manufacturing process and arc erosion, the surface of the copper-chromium contacts exhibits non-uniform characteristics at the microscale, containing micro-regions with different morphologies such as grains, grain boundaries, pores, and chromium-rich areas. These micro-regions exhibit significantly different breakdown characteristics, and actual breakdown often begins in the weakest micro-region.

[0003] Currently, the evaluation of the breakdown characteristics of copper-chromium contacts generally employs a "non-in-situ" macroscopic testing method. This involves fabricating a flat electrode pair of the contact material, placing it in an independent vacuum chamber, and applying high voltage for testing. The obtained data represents the statistical average breakdown performance of the entire electrode surface. However, this traditional method has the following problems: it cannot achieve precise localization and measurement at the microscale, only measuring the overall performance of macroscopic areas at the millimeter or centimeter level, making it difficult to obtain intrinsic breakdown data for micro-areas that have direct guiding significance for material design and failure analysis. Although studies often supplement this with post-test microscopic observation (such as scanning electron microscopy) to analyze the location of breakdown pits and infer weak points, this "test first, observe later" non-in-situ characterization method separates macroscopic electrical performance testing from microscopic morphology analysis, making it impossible to accurately locate and correlate specific microscopic morphology areas at the moment of breakdown.

[0004] In summary, existing methods for testing the breakdown characteristics of copper-chromium contacts suffer from problems such as the inability to locate microscopic regions and distortion of the test sample's condition. Therefore, there is an urgent need in this field for a new method that can accurately and in-situ test the breakdown characteristics of specific microscopic morphological regions on the contact surface without damaging the original surface state, in order to gain a deeper understanding of the breakdown mechanism and provide accurate data support for the design of high-performance vacuum interrupters. Summary of the Invention

[0005] To address the problems existing in the prior art, the purpose of this invention is to provide an in-situ testing method and system for the micro-region breakdown characteristics of the copper-chromium contact surface of a vacuum interrupter. This invention can perform in-situ testing on specific morphological regions of the contact surface.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: An in-situ testing system for the micro-region breakdown characteristics of a copper-chromium contact surface in a vacuum interrupter includes a vacuum chamber and a power supply. The vacuum chamber contains a movable sample stage for holding the electrode under test (DUT). The DUT is insulated from the sample stage. Above the sample stage, the vacuum chamber has a scanning electron beam for electron beam imaging of the DUT surface and a focused ion beam for ion beam imaging of the DUT surface. The scanning electron beam is vertical, while the focused ion beam is not vertical. The vacuum chamber also contains a nanomanipulator arm with a tungsten ball electrode at its end. The nanomanipulator arm is insulated from the tungsten ball electrode. The two poles of the power supply are electrically connected to the tungsten ball electrode and the DUT, respectively.

[0007] Preferably, the end surface of the tungsten ball electrode is smooth and has a radius of curvature of 5~40μm.

[0008] Preferably, the electrode to be tested is a copper-chromium contact cylindrical electrode with a cylindrical shape and a thickness of no more than 1 cm.

[0009] Preferably, the vacuum chamber is equipped with a gas injection system.

[0010] Preferably, the power supply is a DC voltage source, and a vacuum flange is provided on the vacuum chamber; in the vacuum chamber, the tungsten ball electrode and the electrode under test are both connected to the vacuum flange through a shielded wire; outside the vacuum chamber, the DC voltage source is connected to the vacuum flange, thereby realizing that the two poles of the DC voltage source are electrically connected to the tungsten ball electrode and the electrode under test, respectively.

[0011] Preferably, the angle between the focused ion beam and the horizontal is 45° to 60°.

[0012] This invention also provides an in-situ testing method for the micro-region breakdown characteristics of the copper-chromium contact surface of a vacuum interrupter. This in-situ testing method uses the in-situ testing system described above and includes the following steps: Electrode fixation: Fix the tungsten ball electrode to the robotic arm of the nanomanipulator; fix the electrode to be tested horizontally on the top of the sample stage; Gap Distance Adjustment and Measurement: Adjust the position of the nanomanipulator's robotic arm and sample stage to align the edge of the tungsten ball electrode with the edge of the electrode under test vertically. Utilize focused ion beam-assisted imaging to measure the distance from the tip of the tungsten ball electrode to the edge of the electrode under test as shown in the focused ion beam image. d Then, based on the angle between the focused ion beam and the horizontal, calculate the vertical distance from the top of the tungsten ball electrode to the edge of the electrode under test. Voltage application: Keeping the tungsten ball electrode in a fixed position, move the sample stage so that different characteristic areas on the surface of the electrode under test are directly below the tungsten ball electrode, and apply voltage to the tungsten ball electrode and the electrode under test through the power supply; Data acquisition: The changes in the microstructure of the electrode surface before and after breakdown are observed in real time by scanning electron beam, and the voltage and current data of the power supply are recorded.

[0013] Preferably, when applying voltage to the tungsten ball electrode and the electrode under test through the power supply, the voltage is increased from 0V at a preset boost rate. When the electrode under test breaks down or the voltage reaches the preset voltage, the power supply stops applying voltage.

[0014] Preferably, the preset voltage boost rate is 1~2V / s; the preset voltage is the maximum output voltage of the power supply.

[0015] Preferably, the in-situ testing method further includes a pretreatment process for the tungsten ball electrode and the electrode under test, including: The tungsten ball electrode and the electrode under test were ultrasonically cleaned with acetone, anhydrous ethanol and deionized water in sequence to remove the surface oxide layer, oil and impurities. Then they were dried and the electrode was fixed after drying. The ultrasonic frequency was 39~41kHz, the ultrasonic power was 235~245 W, the heating temperature was 30~40 ℃, and the cleaning time was 5~10 min.

[0016] The present invention has the following beneficial effects: This invention provides an in-situ testing system for the micro-region breakdown characteristics of copper-chromium contacts in a vacuum interrupter. It specifically addresses the core problems of existing copper-chromium contact breakdown tests, such as the inability to perform microscopic localization and the separation of testing and observation, enabling in-situ testing of specific morphological regions on the contact surface. The system utilizes a movable sample stage within the vacuum chamber, coupled with a robotic arm equipped with a tungsten ball electrode and a nanomanipulator. This, combined with dual-beam imaging technology using a vertical scanning electron beam and a non-vertical focused ion beam, allows for precise adjustment of the relative positions of the tungsten ball electrode and the electrode under test. This focuses the test on specific micro-regions such as grains, grain boundaries, and pores, overcoming the limitations of traditional macroscopic testing which only obtains average performance data, and accurately acquiring intrinsic breakdown data for micro-regions. Furthermore, the integrated design of the dual-beam imaging structure and the vacuum chamber allows for simultaneous breakdown testing and morphological observation, capturing real-time changes in micro-morphology before and after breakdown. This avoids positional deviations caused by the existing "test first, observe later" approach, ensuring the accuracy of the morphological data. Direct electrical connection between the power supply and the tungsten ball electrode and the electrode under test, combined with dual-beam real-time imaging, enables the simultaneous acquisition of electrical signals such as voltage and current, as well as changes in surface morphology. This provides direct data support for analyzing the influence mechanism of morphology on breakdown characteristics. Furthermore, the insulation design between the electrode under test and the sample stage, and between the robotic arm and the tungsten ball electrode, combined with nanometer-level positioning accuracy and a stable vacuum environment, effectively avoids stray current interference, improving the controllability, repeatability, and data reliability of the test. This makes it suitable for large-scale research on different contact materials and micro-regions. Attached Figure Description

[0017] Figure 1This is a schematic diagram of an in-situ testing system for the micro-region breakdown characteristics of the copper-chromium contact surface of a vacuum interrupter in an embodiment of the present invention.

[0018] Figure 2 SEM image of the tungsten sphere electrode prepared according to an embodiment of the present invention.

[0019] Figure 3 An actual image of the copper-chromium contact cylindrical electrode prepared according to an embodiment of the present invention.

[0020] Figure 4 This is a schematic diagram showing the positional relationship between the scanning electron beam, the focused ion beam, the tungsten ball electrode, and the electrode under test within the vacuum chamber in an embodiment of the present invention.

[0021] Figure 5(a) is a first SEM image of the position between the tungsten ball electrode and the copper-chromium contact cylindrical electrode used in the process of measuring the gap distance in an embodiment of the present invention.

[0022] Figure 5(b) is a second SEM image of the position between the tungsten ball electrode and the copper-chromium contact cylindrical electrode during the gap distance measurement process in an embodiment of the present invention.

[0023] Figure 6 This is a SEM image of the morphology of the copper-chromium contact surface before breakdown at the chromium grain location in an embodiment of the present invention.

[0024] Figure 7(a) is the first SEM image of the morphology after breakdown at the chromium grain position on the surface of the copper-chromium contact in an embodiment of the present invention.

[0025] Figure 7(b) is a second SEM image of the morphology after breakdown at the chromium grain position on the surface of the copper-chromium contact in an embodiment of the present invention.

[0026] Figure 8 This is an EDS energy spectrum of the surface of the copper-chromium contact after breakdown in an embodiment of the present invention.

[0027] Figure 9(a) is a SEM image of the tungsten ball electrode after breakdown in an embodiment of the present invention.

[0028] Figure 9(b) is an enlarged view of part A in Figure 9(a).

[0029] Figure 10 This is a current-voltage curve showing the breakdown process at the chromium grain location on the surface of the copper-chromium contact in an embodiment of the present invention.

[0030] Among them, 1-Focused ion beam, 2-Nanomanipulator robotic arm, 3-Vacuum chamber, 4-Scanning electron beam, 5-Gas injection system, 6-Tungsten ball electrode, 7-Copper-chromium contact cylindrical electrode, 8-Sample stage, 9-Shielding wire, 10-Vacuum flange, 11-Current limiting resistor, 12-Grounding, 13-DC voltage source. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0032] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0033] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0034] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0035] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0036] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0037] The following detailed description of specific embodiments of the present invention, in conjunction with the accompanying drawings, is intended to explain rather than limit the scope of the invention.

[0038] See Figure 1 and Figure 4 This embodiment of the in-situ testing system for the micro-region breakdown characteristics of the copper-chromium contact surface of a vacuum interrupter includes a vacuum chamber 3 and a power supply. The vacuum chamber 3 is equipped with a movable sample stage 8 for holding the electrode under test. The electrode under test is insulated from the sample stage 8. Above the sample stage 8, the vacuum chamber 3 is equipped with a scanning electron beam 4 for electron beam imaging of the surface of the electrode under test and a focused ion beam 1 for ion beam imaging of the surface of the electrode under test. The scanning electron beam 4 is in a vertical position, and the focused ion beam 1 is in a non-vertical position. The vacuum chamber 3 is also equipped with a nanomanipulator arm 2. The end of the nanomanipulator arm 2 is equipped with a tungsten ball electrode 6. The nanomanipulator arm 2 is insulated from the tungsten ball electrode 6. The two poles of the power supply are electrically connected to the tungsten ball electrode 6 and the electrode under test, respectively.

[0039] The in-situ testing method of the in-situ testing system of the above embodiments of the present invention includes the following process: Electrode fixation: Fix the tungsten ball electrode 6 onto the robotic arm 2 of the nanomanipulator; fix the electrode to be tested horizontally on the top of the sample stage 8; Gap Distance Adjustment and Measurement: Adjust the positions of the nanomanipulator robotic arm 2 and the sample stage 8 to align the tungsten ball electrode 6 vertically with the edge of the electrode under test. Use focused ion beam 1 to assist imaging and measure the distance from the top of the tungsten ball electrode 6 to the edge of the electrode under test under the focused ion beam image. d Then, based on the angle between the focused ion beam 1 and the horizontal, calculate the vertical distance from the top of the tungsten ball electrode 6 to the edge of the electrode under test. Voltage application: Keeping the tungsten ball electrode 6 in a fixed position, the sample stage 8 is moved so that different characteristic areas on the surface of the electrode under test are directly below the tungsten ball electrode 6. A voltage is applied to the tungsten ball electrode 6 and the electrode under test through a power supply. When applying the voltage, the voltage rises from 0V at a preset boost rate. When the electrode under test breaks down or the voltage reaches the preset voltage, the power supply stops applying the voltage. The preset boost rate is 1~2V / s. The preset voltage is the maximum output voltage of the power supply. Data acquisition: The changes in the microstructure of the electrode surface before and after breakdown are observed in real time by scanning electron beam 4, and the voltage and current data of the power supply are recorded.

[0040] Furthermore, as an optional embodiment, in this embodiment, before installing the tungsten ball electrode 6 and the electrode under test, it is preferable to clean the tungsten ball electrode 6 and the electrode under test to remove surface impurities, specifically including: The tungsten ball electrode 6 and the electrode under test were ultrasonically cleaned with acetone, anhydrous ethanol and deionized water in sequence to remove the surface oxide layer, oil and impurities. Then they were dried and the electrode was fixed after drying. The ultrasonic frequency was 40±1kHz, the ultrasonic power was 240±5 W, the heating temperature was 35±5 ℃, and the cleaning time was 5~10 min.

[0041] In the above scheme, the value before “±” is the set value (or nominal value) of the corresponding parameter, and the value before “±” is the deviation value of the corresponding parameter. In the following embodiments, only the set value (or nominal value) of the corresponding parameter is given. It can be understood that the relevant parameters in the following embodiments are within the range of the above set value (or nominal value) ± deviation value, and the technical solution is feasible.

[0042] As an optional embodiment, in this embodiment, the end surface of the tungsten ball electrode 6 is smooth and the radius of curvature is 5~40μm.

[0043] As an optional embodiment, in this embodiment, the electrode to be tested is a copper-chromium contact cylindrical electrode 7 with a cylindrical shape and a thickness of no more than 1 cm.

[0044] As an optional embodiment, in this embodiment, the vacuum chamber 3 is provided with a gas injection system 5, which can be used to evacuate and exhaust the vacuum chamber 3, as well as inject protective gas into the vacuum chamber 3.

[0045] As an optional embodiment, in this embodiment, the power supply is a DC voltage source 13, and a vacuum flange 10 is provided on the vacuum chamber 3; in the vacuum chamber 3, the tungsten ball electrode 6 and the electrode under test are both connected to the vacuum flange 10 through the shielding wire 9; outside the vacuum chamber 3, the DC voltage source 13 is connected to the vacuum flange 10, thereby realizing that the two poles of the DC voltage source 13 are electrically connected to the tungsten ball electrode 6 and the electrode under test, respectively.

[0046] As an optional embodiment, in this embodiment, the angle between the focused ion beam 1 and the horizontal is 45°~60°, which facilitates the measurement of the distance from the tip of the tungsten ball electrode 6 to the edge of the electrode under test in the focused ion beam image. d At the same time, it can also ensure the imaging quality of focused ion beam 1.

[0047] Example 1 See Figure 1 ,use Figure 1 The in-situ testing system for the micro-region breakdown characteristics of the copper-chromium contact surface of a vacuum interrupter, as shown, provides an in-situ testing method for the micro-region breakdown characteristics of the copper-chromium contact surface of a vacuum interrupter, specifically including the following steps: S1. Electrode preparation: Tungsten ball electrodes 6 with smooth surfaces and curvature radii of 5~40μm are prepared by electrochemical corrosion and Joule melting. Copper-chromium contacts are made into copper-chromium cylindrical electrodes 7 with a thickness of less than 1 cm and a diameter of 2 cm by wire cutting. S2. Surface Treatment: The tungsten ball electrode 6 and the copper-chromium contact cylindrical electrode 7 obtained in step S1 are ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water to remove oxide layers, oil stains, and other impurities from the electrode surfaces. The ultrasonic frequency is 40kHz, the ultrasonic power is 240W, the heating temperature is 35℃, and the cleaning time is 5 minutes. S3. Electrode Fixing: Fix the tungsten ball electrode 6 on the nanomanipulator robotic arm 2, and fix the copper-chromium contact cylindrical electrode 7 at the center of the top of the sample stage 8, and keep the surface of the copper-chromium contact cylindrical electrode 7 as horizontal as possible. Connect the tungsten ball electrode 6 and the copper-chromium contact cylindrical electrode 7 to the test circuit inside and outside the vacuum chamber 3 through the vacuum flange 10. S4. Gap Distance Adjustment: See [link / reference] Figure 4 The robotic arm 2 and sample stage 8 of the mobile nanomanipulator move the end of the tungsten ball electrode 6 ( Figure 4 The lower end of the tungsten ball electrode 6 is aligned vertically with the upper edge of the copper-chromium contact cylindrical electrode 7. Using focused ion beam 1 to assist imaging, the distance from the top of the tungsten ball electrode 6 to the edge of the copper-chromium contact cylindrical electrode 7 in the focused ion beam image is measured. d Because the focused ion beam 1 has a certain angle α with the horizontal (e.g., 52°), the actual gap distance between the lower end of the tungsten ball electrode 6 and the surface of the copper-chromium contact cylindrical electrode 7 is... h = d ×tanα; S5. Voltage application: Keep the position of the robotic arm 2 of the nanomanipulator unchanged throughout the test (that is, keep the position of the tungsten ball electrode 6 unchanged), move the sample stage 8 so that different feature areas on the surface of the copper-chromium contact cylindrical electrode 7 are directly below the tungsten ball electrode 6, and use the LabVIEW program to control the output voltage of the DC voltage source 13 to increase stepwise at a rate of 1 V / s. S6. Data Acquisition: Observe the changes in the microstructure of the cylindrical electrode 7 of the copper-chromium contact before and after breakdown in real time, and record the voltage and current data.

[0048] Example 2 A tungsten ball electrode 6 with a radius of curvature of 8 μm was used as the counter electrode. The copper-chromium contact cylindrical electrode 7 was a contact material that had undergone vacuum arc melting and voltage aging. By mass percentage, the copper content in the copper-chromium contact cylindrical electrode 7 was 60 wt%, with the balance being chromium and unavoidable impurities. The breakdown voltage of a chromium grain on the surface of the copper-chromium contact cylindrical electrode and the morphological changes before and after breakdown were obtained.

[0049] The in-situ testing method for the micro-region breakdown characteristics of the copper-chromium contact surface in the vacuum interrupter in this embodiment specifically includes the following steps: S1. Electrode preparation: See [link / reference] Figure 2 First, a conical tungsten needle with a tip curvature radius of 2 μm was prepared by electrochemical etching using a high-purity tungsten wire with a diameter of 0.4 mm and a purity of 99.99%. Then, a tungsten ball electrode 6 with a spherical tip and a curvature radius of 8 μm was prepared using the Joule heating method. The tungsten ball prepared by this method has a smooth surface. See also... Figure 3 The copper-chromium contact (60 wt% copper, balance chromium and unavoidable impurities) that has undergone vacuum arc melting and voltage aging is wire cut to obtain a copper-chromium contact cylindrical electrode 7 with a thickness of 1 cm and a diameter of 2 cm. S2. Surface treatment: The prepared tungsten ball electrode 6 and copper-chromium contact cylindrical electrode 7 are ultrasonically cleaned sequentially with acetone, anhydrous ethanol and deionized water to remove the oxide layer, oil and other impurities on the electrode surface; the ultrasonic cleaning parameters are as follows: ultrasonic frequency 40 kHz, ultrasonic power 240 W, heating temperature 35 ℃, cleaning time 5 min. S3, Electrode Fixation: See [link] Figure 1 Inside the vacuum chamber 3, a tungsten ball electrode 6 is fixed to the robotic arm 2 of the nanomanipulator, and a copper-chromium contact cylindrical electrode 7 is fixed at the center of the sample stage 8. Insulation tape is used to protect the electrodes from the sample stage. The test circuit is connected internally and externally through a custom flange 10 of the vacuum chamber. The tungsten ball electrode 6 on the robotic arm 2 of the nanomanipulator is electrically insulated from the manipulator through a custom insulating adapter unit and is connected to the internal interface of the flange 10 using a shielded wire 9. The external interface is connected to the positive terminal of the DC voltage source 13. Similarly, the copper-chromium contact cylindrical electrode 7 on the sample stage is connected to another interface inside the flange using a shielded wire 9. The external interface is connected to the negative terminal of the DC voltage source through a 5000 Ω current-limiting resistor 11 and grounded 12. S4. Gap Distance Adjustment: See [link / reference] Figure 4 The figure shows the positional relationship between the scanning electron beam 4 and the focused ion beam 1 inside the vacuum chamber 3. Since the scanning electron beam 4 is directly above the copper-chromium contact cylindrical electrode 7, the gap distance cannot be directly measured using the scanning electron beam image. Therefore, the gap distance value is indirectly measured using the focused ion beam 1. The specific method is as follows: Referring to Figures 5(a) and 5(b), the nanomanipulator robotic arm 2 and the sample stage 8 are moved under electron beam imaging to move the top of the tungsten ball electrode 6 (i.e., Figure 4 The lower end of the tungsten ball electrode 6 is aligned vertically with the edge of the copper-chromium contact cylindrical electrode 7. The ion beam is turned on (the ion beam current should not be too high, otherwise it will damage the sample surface), and the distance between the top of the tungsten ball electrode 6 and the edge of the copper-chromium contact cylindrical electrode 7 is measured under ion beam imaging. dSince the ion beam makes a 52° angle with the horizontal, the vertical gap height between the tungsten ball electrode and the surface of the copper-chromium contact cylindrical electrode can be determined by the formula... h = d The value is calculated using ×tan52°. This embodiment... d =1.46 μm, which can be obtained through calculation. h =1.87 μm; S5. Voltage Application: During voltage application, to ensure the gap height (i.e., the distance between the end of the tungsten ball electrode 6 and the surface of the copper-chromium contact cylindrical electrode 7) remains constant, the position of the nanomanipulator robotic arm 2 and the height of the sample stage 8 should be kept constant. During the test, the test area is changed by horizontally moving the sample stage 8, so that different characteristic areas on the surface of the copper-chromium contact cylindrical electrode 7 are located directly below the tungsten ball electrode 6. In this embodiment, moving the sample stage 8 causes a chromium grain on the surface of the copper-chromium contact cylindrical electrode to be located directly below the tungsten ball electrode 6, and the microstructure of this chromium grain before breakdown is obtained, such as... Figure 6 As shown (the yellow dashed line represents the actual position of the tungsten ball electrode).

[0050] Using LabVIEW software, control the output voltage of a DC voltage source to increase stepwise from 0 V at a rate of 1 V / s, and immediately stop the program manually after a breakdown occurs or automatically stop the program when the maximum output voltage of 1000 V is reached.

[0051] S6. Data Acquisition: The morphology of the copper-chromium contact electrode surface before and after breakdown was obtained using electron beam imaging. Current data during the voltage application process was acquired using LabVIEW software (for plotting current-voltage curves) and saved. In this embodiment, the morphology of the chromium grains on the surface of the cylindrical electrode of the copper-chromium contact after breakdown is shown in Figures 7(a) and 7(b) (at the location of the white dashed box), compared with the morphology before breakdown (…). Figure 6 In contrast, the surface of the chromium grains after breakdown exhibits a molten pit morphology, and EDS energy dispersive spectroscopy analysis of this region yields the following results: Figure 8 As shown, its main component is Cr, indicating that the breakdown process is dominated by the cathode (chromium phase). The cathode field emission current generates Joule heating, which causes the emission point (chromium grains) to melt, metal vapor is released, and plasma channels are formed.

[0052] In this embodiment, a melting pit also appeared on the surface of the tungsten ball electrode, as shown in Figures 9(a) and 9(b). The formation of the melting pit is due to the heat released by the metal vapor accumulating on the surface of the tungsten ball. When the heat exceeds the melting point of the tungsten ball, a melting pit is eventually formed.

[0053] In this embodiment, the current-voltage curve of the breakdown process in this region is as follows: Figure 10 As shown, its breakdown voltage threshold is 645V, and its breakdown field strength is 3.45×10⁻⁶. 8 V / m.

[0054] As can be seen from the above experimental results, the technical solution of the present invention has the following characteristics: 1. Precise micro-area localization of copper-chromium contact surface breakdown testing has been achieved. By precisely adjusting the relative positions of the tungsten ball electrode and the cylindrical electrode of the copper-chromium contact using a nanomanipulator and sample stage, and combining electron beam and ion beam imaging technology, high-precision localization of specific micro-areas on the contact surface can be achieved in a vacuum environment, overcoming the limitation of traditional macroscopic electrode structure testing methods that cannot conduct breakdown studies on local areas.

[0055] 2. In-situ morphological observation of the breakdown process is achieved. This invention utilizes dual-beam imaging to achieve real-time imaging during electrode gap adjustment and breakdown loading, simultaneously acquiring information on the microscopic morphological changes of the contact surface before and after breakdown, thus solving the problem of difficult corresponding observation of the morphology before and after breakdown in existing technologies.

[0056] 3. The correlation between electrical signals and morphological evolution was obtained. This method can simultaneously acquire voltage and current data and surface morphological changes during the breakdown process, realize the correlation analysis between electrical behavior and structural characteristics, and provide an effective technical means to reveal the mechanism by which the surface morphology of the contact affects the breakdown characteristics.

[0057] 4. High repeatability and testing accuracy. Through nanometer-level position control and vacuum environment testing, this invention improves the controllability of experiments and the reliability of data, making it suitable for repeatable studies of different contact materials and different morphological regions.

[0058] 5. This invention enables in-situ testing of the breakdown characteristics of specific micro-regions on the surface of copper-chromium contacts in vacuum interrupters, revealing the influence of surface morphology on breakdown behavior. It provides theoretical support for contact surface control and process optimization, and is of great significance for improving the insulation performance of vacuum interrupters and developing higher voltage level products.

[0059] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. An in-situ testing system for the micro-region breakdown characteristics of the copper-chromium contact surface in a vacuum interrupter, characterized in that, The device includes a vacuum chamber (3) and a power supply. The vacuum chamber (3) is equipped with a movable sample stage (8) for holding the electrode to be tested. The electrode to be tested is insulated from the sample stage (8). Above the sample stage (8), the vacuum chamber (3) is equipped with a scanning electron beam (4) for electron beam imaging of the surface of the electrode to be tested and a focused ion beam (1) for ion beam imaging of the surface of the electrode to be tested. The scanning electron beam (4) is in a vertical state, and the focused ion beam (1) is in a non-vertical state. The vacuum chamber (3) is also equipped with a nanomanipulator arm (2). The end of the nanomanipulator arm (2) is equipped with a tungsten ball electrode (6). The nanomanipulator arm (2) is insulated from the tungsten ball electrode (6). The two poles of the power supply are electrically connected to the tungsten ball electrode (6) and the electrode to be tested, respectively.

2. The in-situ testing system for the micro-region breakdown characteristics of the copper-chromium contact surface of a vacuum interrupter according to claim 1, characterized in that, The tungsten ball electrode (6) has a smooth end surface and a radius of curvature of 5~40μm.

3. The in-situ testing system for the micro-region breakdown characteristics of the copper-chromium contact surface of a vacuum interrupter according to claim 1, characterized in that, The electrode to be tested is a copper-chromium contact cylindrical electrode (7) with a cylindrical shape and a thickness of no more than 1 cm.

4. The in-situ testing system for the micro-region breakdown characteristics of the copper-chromium contact surface of a vacuum interrupter according to claim 1, characterized in that, A gas injection system (5) is provided on the vacuum chamber (3).

5. The in-situ testing system for the micro-region breakdown characteristics of the copper-chromium contact surface of a vacuum interrupter according to claim 1, characterized in that, The power supply is a DC voltage source (13), and a vacuum flange (10) is provided on the vacuum chamber (3). In the vacuum chamber (3), the tungsten ball electrode (6) and the electrode under test are connected to the vacuum flange (10) through a shielding wire (9). Outside the vacuum chamber (3), the DC voltage source (13) is connected to the vacuum flange (10), thereby realizing that the two poles of the DC voltage source (13) are electrically connected to the tungsten ball electrode (6) and the electrode under test, respectively.

6. The in-situ testing system for the micro-region breakdown characteristics of the copper-chromium contact surface of a vacuum interrupter according to claim 1, characterized in that, The angle between the focused ion beam (1) and the horizontal is 45°~60°.

7. An in-situ testing method for the micro-region breakdown characteristics of the copper-chromium contact surface of a vacuum interrupter, characterized in that, The in-situ testing method is performed using the in-situ testing system described in any one of claims 1-6, and includes the following process: Electrode fixation: Fix the tungsten ball electrode (6) on the robotic arm (2) of the nanomanipulator; fix the electrode to be tested horizontally on the top of the sample stage (8); Gap distance adjustment and measurement: Adjust the position of the nanomanipulator robotic arm (2) and the sample stage (8) to align the tungsten ball electrode (6) with the edge of the electrode to be tested vertically. Use the focused ion beam (1) to assist imaging and measure the distance from the top of the tungsten ball electrode (6) to the edge of the electrode to be tested under the focused ion beam image. Then, calculate the vertical distance from the top of the tungsten ball electrode (6) to the edge of the electrode to be tested according to the angle between the focused ion beam (1) and the horizontal. Voltage application: Keep the position of the tungsten ball electrode (6) unchanged, move the sample stage (8) so that different feature areas on the surface of the electrode to be tested are located directly below the tungsten ball electrode (6), and apply voltage to the tungsten ball electrode (6) and the electrode to be tested through the power supply; Data acquisition: The changes in the microstructure of the electrode surface before and after breakdown are observed in real time by scanning electron beam (4), and the voltage and current data of the power supply are recorded.

8. The in-situ testing method for the micro-region breakdown characteristics of the copper-chromium contact surface of a vacuum interrupter according to claim 7, characterized in that, When a voltage is applied to the tungsten ball electrode (6) and the electrode under test by the power supply, the voltage is increased from 0V at a preset boost rate. When the electrode under test breaks down or the voltage reaches the preset voltage, the power supply stops applying the voltage.

9. The in-situ testing method for the micro-region breakdown characteristics of the copper-chromium contact surface of a vacuum interrupter according to claim 7, characterized in that, The preset voltage boost rate is 1~2V / s; the preset voltage is the maximum output voltage of the power supply.

10. The in-situ testing method for the micro-region breakdown characteristics of the copper-chromium contact surface of a vacuum interrupter according to claim 7, characterized in that, It also includes a pretreatment process for the tungsten ball electrode (6) and the electrode under test, including: The tungsten ball electrode (6) and the electrode to be tested were ultrasonically cleaned with acetone, anhydrous ethanol and deionized water in sequence to remove the surface oxide layer, oil and impurities, and then dried. After drying, the electrode was fixed. The ultrasonic frequency was 39~41kHz, the ultrasonic power was 235~245 W, the heating temperature was 30~40 ℃, and the cleaning time was 5~10 min.

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