A vacuum interrupter and circuit breaker with a main shield, a method of manufacture and use thereof

Abstract

This invention discloses a main shield, its preparation method, and its application in a vacuum interrupter and circuit breaker, belonging to the technical field of vacuum switchgear. The main shield includes an inner surface, an outer surface, and an end-curled edge region extending inward from the outer surface. At least a portion of its surface is provided with an insulating ceramic functional layer. The insulating ceramic functional layer forms a spatially continuously varying structural system along the inner surface to the end-curled edge region and extending to the outer surface, giving different regions different structural characteristics. Specifically, the inner surface away from the curled edge region has a multi-layered structure, the inner surface near the curled edge region has a gradient structure with continuously varying porosity, density, and thickness, and the end-curled edge region and outer surface region have a dense and uniform structure. This invention also provides a vacuum interrupter and circuit breaker including the above-mentioned main shield. The main shield, vacuum interrupter, and circuit breaker of this invention can simultaneously meet the requirements of arc erosion resistance, stress relief, and electric field control, improving insulation reliability and operational stability.

Description

Technical Field

[0001] This invention relates to the field of electrical switchgear technology, specifically to a main shield, its preparation method, and its application in a vacuum interrupter and circuit breaker. Background Technology

[0002] In a vacuum interrupter, the main shield is used to shield the metal vapor generated by the interrupting electric arc and regulate the internal electric field distribution. However, under high voltage and extreme operating conditions, the inner surface of the main shield is subjected to arc erosion and thermal cycling for a long time, which can easily lead to local melting and structural degradation. At the same time, the rolled edge area at its end is prone to becoming an electron emission source due to the concentration of electric field, inducing surface flashover or even breakdown, which in turn leads to insulation failure of the vacuum interrupter.

[0003] In existing technologies, ceramic or organic coatings are typically applied to the surface of the main shield to improve insulation performance and resistance to arc erosion. Related technologies mainly focus on improving high-temperature resistance, heat dissipation, arc erosion resistance, and insulation performance through material modification or coating structure optimization. However, these technologies primarily optimize the overall performance of the coating and lack a systematic consideration of the differences in service environments in different regions.

[0004] During the actual operation of a vacuum interrupter, the physical effects experienced by different areas of the main shield vary significantly. The inner surface is directly exposed to the arc environment generated during the interruption process, and is simultaneously subjected to high temperature, arc impact, and thermal cycling coupling. The outer surface is located at the start and end points of surface flashover, and its surface condition has a significant impact on the electric field distribution and the initiation of surface flashover. Due to the geometric changes, the end rolled edge region is not only an area of ​​electric field concentration but also a continuous transition zone between the inner and outer surfaces, which is prone to stress concentration and stress transmission problems.

[0005] During long-term service, ceramic coatings may experience stress cracking under the influence of electric arc impact and thermal cycling. When cracks extend to the edge area, stress concentration exacerbates the cracking, failure, and even detachment of the coating in that area, leading to a decrease in the coating's insulation performance, increasing the risk of surface flashover and breakdown, and threatening the long-term stable operation of the vacuum interrupter.

[0006] However, existing technologies have not addressed the structural differences in service mechanisms across these regions, particularly lacking functional zoning designs for the inner and outer surfaces of the main shield and the end rolled edge areas, as well as specialized structural reinforcement or stress control designs for the end rolled edge areas. Therefore, existing technologies struggle to simultaneously meet the multiple requirements of the main shield surface structure during long-term service, including resistance to arc erosion, surface flashover suppression, and stress transmission control. Summary of the Invention

[0007] To address the problems existing in the prior art, the present invention aims to provide a vacuum interrupter and circuit breaker with a partitioned main shield, a preparation method thereof, and their applications. By differentiating the surface structure of different spatial regions of the main shield, the invention achieves coordinated control of arcing, surface discharge, and stress transmission, thereby improving the operational stability of the main shield and reducing the risk of insulation failure.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A main shield includes an inner surface facing the contact gap, an outer surface adjacent to the ceramic shell, and an end rolled edge region extending from the outer surface to the inner surface. At least a portion of the surface of the main shield is provided with an insulating ceramic functional layer, and the functional layer extends from the inner surface to the end rolled edge region and to the outer surface to form a structural system with spatially continuous variation characteristics. Different positions have different structural features, realizing differentiated construction for different service areas; wherein: The functional layer on the inner surface away from the end rolled edge region is configured as a multi-layer structure, including an inner layer and an outer layer. The outer layer is a dense structure, and the inner layer is a microporous structure. This structure improves the resistance to arc erosion while mitigating thermal shock.

[0009] The functional layer on the inner surface near the end rolled edge region is configured as a gradient structure with porosity or density and thickness that continuously varies along the spatial direction, so as to mitigate the transmission of thermal stress to the end rolled edge region. The end rolled edge region and the functional layer on the outer surface are configured as a dense and uniform structure, which is beneficial to improve the local electric field distribution and reduce the risk of surface flashover. The porosity or density and surface condition of the functional layer change continuously from the inner surface to the rolled edge and outer surface. The structural system is used to achieve the synergistic effect of arc erosion resistance, stress transition and electric field control.

[0010] Preferably, the outer layer has a high thermal conductivity structure with a thermal conductivity of 30-200 W / (m·K); the inner layer has a microporous structure with a porosity of 5%-15%.

[0011] Preferably, the porosity of the gradient structure varies from high to low from the central region of the inner surface to the rolled edge region at the end.

[0012] Preferably, the porosity of the gradient structure gradually decreases from 5%-15% to below 2%; the porosity of the functional layer in the end rolled edge region is 0.5%–2%.

[0013] Preferably, the surface roughness Ra of the functional layer of the end rolled edge region and the outer surface is not greater than 1.5 μm.

[0014] The method for preparing the main shield includes the following steps: 1) Degrease, clean, sandblast, or roughen the metal substrate of the main shielding cover; 2) An insulating ceramic functional layer containing a microporous structure is deposited on the inner surface of the main shield away from the end rolled edge area by plasma spraying; 3) A gradient insulating ceramic functional layer with continuously varying porosity or density and thickness along the spatial direction is deposited on the surface of the main shield near the end rolled edge area by plasma spraying. 4) A high-density, low-roughness insulating ceramic functional layer is deposited on the rolled edge area and outer surface of the main shield using plasma spraying. 5) A highly thermally conductive and dense insulating ceramic functional layer is deposited on the inner surface of the main shield, away from the end rolled edge area, using plasma spraying. 6) Perform thermal annealing on the main shield after the deposition of the functional layer.

[0015] Preferably, the structural differences in different regions are achieved by adjusting at least one parameter among spraying power, spraying distance, powder feeding rate, or powder composition.

[0016] Preferably, in step 2), the plasma spraying power is 25-30kW, the spraying distance is 100-130mm, and the powder feeding rate is 15-20g / min. These process parameters form a microporous structure with a certain porosity, which helps to mitigate thermal stress under arc ablation and thermal cycling, reducing the risk of functional layer cracking. The microporous structure releases local strain energy through pore compression deformation, reducing stress concentration.

[0017] In step 3), the plasma spraying power is gradually increased from 25-30kW to 40-60kW, the spraying distance is gradually decreased from 100-130mm to 70-100mm, and the powder feeding rate is adjusted from 15-20g / min to 25-45g / min. By continuously adjusting the above parameters, a gradient structure with continuously changing porosity is formed, which achieves a smooth transition of stress between different structural regions, reduces the stress concentration at structural abrupt changes, and thus inhibits crack propagation.

[0018] In step 4), the plasma spraying power is 40–60kW, the spraying distance is 70–100mm, and the powder feeding rate is 25–45g / min. The formation of a dense and uniform functional layer structure through the above parameters helps to reduce local electric field distortion, suppress electron emission, thereby improving insulation performance and reducing the risk of breakdown.

[0019] In step 5), the plasma spraying power is 40–60kW, the spraying distance is 70–100mm, the powder feeding rate is 25–45g / min, and 10wt%–90wt% of aluminum nitride is added to the sprayed powder. By introducing high thermal conductivity components, the thermal conductivity of the functional layer is improved, which is conducive to accelerating heat diffusion and reducing local temperature rise and thermal stress caused by arc ablation.

[0020] In step 6), the heat annealing temperature is 400–800℃ and the holding time is 0.5–2h. The above heat treatment process can release the residual stress generated during the spraying process and reduce local structural defects, thereby improving the structural stability and bonding strength of the functional layer.

[0021] A vacuum interrupter includes a contact assembly and a main shield. Through a partitioned coating structure design, it is beneficial to simultaneously achieve anti-arc erosion, stress relief and electric field regulation, thereby improving the insulation performance and operational stability of the vacuum interrupter.

[0022] A vacuum circuit breaker includes the aforementioned vacuum interrupter chamber, wherein the vacuum interrupter chamber employs a main shield with a partitioned coating structure, which is beneficial to improving the insulation reliability of the circuit breaker under high voltage and frequent interruption conditions, reducing the risk of surface flashover and breakdown, thereby improving the overall operational stability and service life of the unit.

[0023] Compared with the prior art, the present invention has the following advantages: 1. By implementing a partitioned structural design for the inner surface, end rolled edge area, and outer surface area of ​​the main shield, differentiated construction for different service areas can be achieved; 2. A multi-layer structure is set on the inner surface away from the end rolled edge area to improve the resistance to electric arc ablation and alleviate the thermal shock effect; 3. A gradient structure is provided on the inner surface near the end rolled edge area to reduce the transmission of thermal stress to the end rolled edge area; 4. A dense and uniform structure is provided in the end rolled edge area and outer surface area, which helps to improve the local electric field distribution and reduce the risk of surface flashover; 5. By forming a continuous structural system of "anti-ablation - stress transition - electric field regulation", the overall operational reliability of the main shield is improved. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the internal structure of a vacuum interrupter. Figure 2 Schematic diagram of the main shielding cover partition structure; Figure 3 This is a schematic diagram of the two-dimensional expansion of the functional layers of the partition structure; Figure 4 This is an enlarged schematic diagram of the structure of the end rolled edge area; Figure 5 This is a Weibull distribution curve of the lightning impulse test. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0026] This embodiment provides a main shield with a partitioned structure, which includes a metal substrate and an insulating ceramic functional layer disposed on its surface. For example... Figure 1 As shown, the main shield 1 is located inside the vacuum interrupter chamber and is used to shield the metal vapor generated by the electric arc and regulate the electric field distribution. The main shield 1 has contacts 2 inside and a ceramic shell 3 outside. Figure 2 As shown, the main shield 1 is divided into a functional layer 101 on the inner surface away from the end rolled edge region, a functional layer 102 on the inner surface near the end rolled edge region, a functional layer 103 on the end rolled edge region, and a functional layer 104 on the outer surface.

[0027] (1) Structural composition 1) Functional layer 101 on the inner surface away from the end rolled edge area The functional layer 101 on the inner surface away from the end rolled edge region is configured with a structure having a high porosity, and the insulating ceramic functional layer is a multilayer structure.

[0028] In this embodiment, the outer layer is a high thermal conductivity dense layer with a thermal conductivity of 30–200 W / (m·K) and a porosity of 0.5%–2%; the inner layer is a microporous structure with a porosity of 5%–15%; the micropore scale is from submicron to several micrometers; and the total thickness of the insulating ceramic functional layer is 50–150 μm.

[0029] 2) Functional layer 102 near the end rolled edge area on the inner surface The functional layer 102 near the end rolled edge region on the inner surface is configured as a stress transition zone. This region has a gradient structure, and its porosity changes continuously along the spatial direction. For example... Figure 3 As shown, the stress transition zone gradually densifies from the inner surface away from the end rolled edge region toward the end rolled edge region.

[0030] In this embodiment, the porosity gradually decreases from about 5%-15% to below 2%, and the thickness of the insulating ceramic functional layer gradually increases from the inner surface away from the end rolled edge region toward the end rolled edge region.

[0031] 3) End rolled edge area functional layer 103 The end-curled edge region functional layer 103 is a region of geometrical variation, and its surface is set with a dense structure. For example... Figure 4 As shown, the density of the insulating ceramic functional layer of the end rolled edge region functional layer 103 is higher than that of the adjacent region.

[0032] In this embodiment, the porosity is controlled at 0.5%–2%, and the surface roughness Ra is not greater than 1.5 μm.

[0033] 4) Outer surface functional layer 104 The outer surface functional layer 104 is configured with a dense and uniform surface structure.

[0034] In this embodiment, the porosity is 0.5%–2%, the surface roughness Ra is no greater than 1.5 μm, and the thickness of the insulating ceramic functional layer is 30–100 μm.

[0035] (2) Functional layer materials In this embodiment, the functional layer is an alumina ceramic material. The outer layer of the functional layer, located on the inner surface away from the end rolled edge region, is a ceramic material comprising 10wt%-90wt% aluminum nitride and 90wt%-10wt% alumina.

[0036] (3) Preparation method This embodiment uses a plasma spraying process to prepare the functional layer of the main shielding cover, including the following steps: Step 1: Matrix Treatment The main shield metal substrate was degreased, cleaned, and sandblasted; the surface roughness Ra after sandblasting was 2–10 μm.

[0037] Step 2: Deposit functional layers in zones By adjusting the spraying process parameters, differentiated structures can be created in different areas: 1) Deposit an inner layer on the inner surface away from the end rolled edge area, with a spraying power of 25–30 kW, a spraying distance of 100–130 mm, and a powder feeding rate of 15–20 g / min, to form a microporous structure.

[0038] 2) In the stress transition zone, i.e. the inner surface near the end edge curling area of ​​the functional layer 102, the spraying parameters are continuously adjusted to adjust the spraying power from 25–30 kW to 40–60 kW, the spraying distance from 100–130 mm to 70–100 mm, and the powder feeding rate from 15–20 g / min to 25–45 g / min to form a gradient structure.

[0039] 3) Deposit dense, low-roughness insulating ceramics in the end-edge area and outer surface area, with a spraying power of 40–60 kW, a spraying distance of 70–100 mm, and a powder feeding rate of 25–45 g / min.

[0040] 4) Deposit an outer layer on the inner surface away from the end rolled edge area, using the same spraying parameters as the outer surface area, and use a ceramic material containing 10wt%-90wt% aluminum nitride and 90wt%-10wt% alumina powder to form a highly thermally conductive and dense outer layer.

[0041] Step 3: Heat treatment The functional layer after spraying is heat-treated at a temperature of 400–800 ℃ for 0.5–2 h to release residual stress and improve bonding strength.

[0042] (4) Performance test and results To verify the improved insulation performance and operational stability of the partitioned main shield described in this invention, lightning impulse tests were conducted on vacuum interrupter samples using different main shields for comparison. Three types of vacuum interrupter samples were selected for comparative testing: 1) Substrate sample: Vacuum interrupter sample with main shield without insulating ceramic functional layer; 2) Unpartitioned sample: A vacuum interrupter sample with a main shield having a uniform alumina functional layer on the entire surface but without partitioned structural design; 3) Partitioned structure sample: The vacuum interrupter sample with partitioned structure main shield of the present invention is adopted.

[0043] A standard lightning impulse voltage generator was used to conduct repeated impulse tests on the above samples. The test conditions were as follows: the impulse voltage waveform was a standard lightning impulse wave (1.2 / 50 μs); the impulse voltage was applied sequentially, with each sample subjected to 50 impulses; the voltage amplitude applied each time was gradually varied according to a set program; the voltage value of each impulse and whether the sample broke down were recorded. The breakdown criterion was the occurrence of typical breakdown characteristics such as a sudden voltage drop and a surge in current.

[0044] To quantitatively evaluate the differences in insulation performance among different samples under lightning impulse, breakdown events were considered failure events, and a two-parameter Weibull distribution was used for statistical analysis of the breakdown data. The cumulative failure probability can be expressed as:

[0045] in, P ( U ) for impulse voltage U The cumulative probability of breakdown is η, which is the characteristic breakdown voltage and characterizes the overall insulation withstand level of the sample. The higher the value, the more the sample can withstand higher amplitude lightning impulse voltage. β is the Weibull shape parameter, which characterizes the dispersion of breakdown data and the consistency of failure. The larger the value, the more concentrated the breakdown distribution, the smaller the fluctuation of insulation performance, and the better the operational stability.

[0046] In practical processing, based on the results of 50 impact tests, the breakdown voltage values ​​can be sorted from low to high, and the cumulative failure probability can be estimated according to the rank. Then, the Weibull linearization method can be used for fitting. The linearization expression is:

[0047] By comparing lnU and By performing linear fitting, the corresponding β and η for each type of sample can be obtained.

[0048] Based on the experimental data, the following statistical analysis was performed on various types of samples: Table 1 Statistical analysis of test results for each sample

[0049] like Figure 5 As shown in Table 1, the Weibull distribution curves of different samples exhibit significant differences. The partitioned structure sample showed a 51.6% and 6.3% increase in initial breakdown voltage, respectively, and a 68.3% and 25.4% increase in characteristic breakdown voltage η, respectively, compared to the substrate sample and the unpartitioned sample. These increases are significantly higher than those of the substrate sample and the unpartitioned sample, indicating an improved overall insulation withstand level. During the experiment, the breakdown frequency of the partitioned structure sample decreased by 10% and 8% compared to the substrate sample and the unpartitioned sample, respectively. Furthermore, the larger Weibull shape parameter β indicates a more concentrated breakdown voltage distribution, less dispersion in insulation performance, and better operational stability.

[0050] (5) Mechanism explanation During the arc breaking process, the inner surface of the main shield is subjected to high-temperature metal vapor impact and thermal cycling, which easily leads to thermal stress and structural damage. This invention employs a multi-layered structure on the inner surface away from the end rolled edge region, consisting of a high thermal conductivity, dense outer layer and a microporous inner layer to improve heat dissipation and alleviate localized stress concentration. A gradient structure is also incorporated on the inner surface near the end rolled edge region, allowing thermal stress to gradually transition along the spatial direction. A dense, low-roughness structure is provided in the end rolled edge region to improve the local electric field distribution. Finally, a dense, uniform structure is used on the outer surface region to reduce the risk of partial discharge. Therefore, this invention achieves synergistic control of thermal stress, electric field distribution, and discharge behavior through continuous structural changes.

Claims

1. A main shielding cover, characterized in that: The main shielding cover includes an inner surface facing the contact gap, an outer surface adjacent to the ceramic shell, and an end rolled edge region extending from the outer surface to the inner surface; The surface of the main shield is provided with an insulating ceramic functional layer, and the functional layer extends from the inner surface to the end rolled edge region and to the outer surface to form a structural system with spatially continuous variation characteristics. Different positions have different structural features, wherein: The functional layer on the inner surface away from the end rolled edge area is configured as a multi-layer structure, including an inner layer and an outer layer. The outer layer is a dense structure, and the inner layer is a microporous structure. The functional layer near the end rolled edge region of the inner surface is configured as a gradient structure in which the porosity, density, and thickness continuously vary along the spatial direction. The end rolled edge region and the functional layer on the outer surface are configured with a dense and uniform surface structure; The porosity, density, and surface condition of the functional layer change continuously from the inner surface to the rolled edge and outer surface. The structural system is used to achieve the synergistic effect of arc erosion resistance, stress transition and electric field modulation; The outer layer has a high thermal conductivity structure with a thermal conductivity of 30-200 W / (m·K); the inner layer has a microporous structure with a porosity of 5%-15%. The porosity of the gradient structure changes from high to low from the central region of the inner surface to the rolled edge region at the end. The porosity of the gradient structure gradually decreases from 5%-15% to below 2%; the porosity of the functional layer in the end rolled edge region is 0.5%–2%.

2. The main shielding cover according to claim 1, characterized in that: The surface roughness Ra of the functional layer of the end rolled edge area and outer surface is no greater than 1.5 μm.

3. A method for preparing a main shield as described in claim 1 or 2, characterized in that: Includes the following steps: 1) The main shielding metal substrate is degreased, cleaned, sandblasted, and roughened; 2) An insulating ceramic functional layer containing a microporous structure is deposited on the inner surface of the main shield away from the end rolled edge area by plasma spraying; 3) A gradient insulating ceramic functional layer with continuously varying porosity, density, and thickness along the spatial direction is deposited on the surface of the main shield near the end rolled edge area by plasma spraying. 4) A high-density, low-roughness insulating ceramic functional layer is deposited on the rolled edge area and outer surface of the main shield using plasma spraying; 5) A highly thermally conductive and dense insulating ceramic functional layer is deposited on the inner surface of the main shield, away from the end rolled edge area, using plasma spraying. 6) Perform thermal annealing on the main shield after depositing the functional layer.

4. The preparation method according to claim 3, characterized in that: Different regional structural differences can be achieved by adjusting at least one parameter among spraying power, spraying distance, powder feeding rate, or powder composition.

5. The preparation method according to claim 3, characterized in that: In step 2), the plasma spraying power is 25-30kW, the spraying distance is 100-130mm, and the powder feeding rate is 15-20g / min; In step 3), the plasma spraying power is gradually increased from 25-30kW to 40-60kW, the spraying distance is gradually decreased from 100-130mm to 70-100mm, and the powder feeding rate is adjusted from 15-20g / min to 25-45g / min. In step 4), the plasma spraying power is 40–60kW, the spraying distance is 70–100mm, and the powder feeding rate is 25–45g / min. In step 5), the plasma spraying power is 40–60kW, the spraying distance is 70–100mm, the powder feeding rate is 25–45g / min, and 10wt%–90wt% of aluminum nitride is added to the spraying powder. In step 6), the heat annealing temperature is 400–800℃, and the holding time is 0.5–2h.

6. A vacuum interrupter, characterized in that, It includes a contact assembly and a main shield, wherein the main shield is the main shield as described in claim 1 or 2.

7. A vacuum circuit breaker, characterized in that, Includes the vacuum interrupter as described in claim 6.

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