A method for simulating contact resistance of GIS contact

Abstract

The application discloses a simulation method of GIS contact contact resistance, which comprises the following steps: firstly, calculating the equivalent radius of the contact resistance, and calculating the current flow area of the contact resistance according to the equivalent radius; keeping the current flow area unchanged, converting the shape of the contact resistance into a rectangular block, and establishing an equivalent contact resistance model for each contact finger in three-dimensional software; then, classifying and fusing the models of the whole contact finger area; in the electromagnetic field calculation, the size of the contact resistance and the size of the equivalent model are combined to convert the conductivity thereof, so as to simulate the working conditions of different contact resistances; in the temperature-fluid field coupling calculation, the size of the contact resistance and the conductivity are combined to calculate the thermal conductivity of the equivalent contact resistance, and the loss calculation result of the electromagnetic field is introduced into the temperature-fluid field, so that the accurate simulation of the contact resistance can be realized in simulation.

Description

Technical Field

[0001] This invention relates to the field of GIS equipment technology, and in particular to a method for simulating the contact resistance of GIS contacts. Background Technology

[0002] Gas-insulated switchgear (GIS) is widely used in the power industry due to its advantages such as small footprint, reliable operation, long service life, long maintenance cycle, and ease of installation. Statistics show that in the past decade, the State Grid Corporation of China system has over 60,000 GIS bays in operation for 66-1000kV systems, with an average annual growth rate of 13%. Although GIS equipment is reliable, its stability is difficult to guarantee due to various factors such as transportation, assembly, structural materials, and manufacturing processes. Problems such as loose internal screws, missing components, and insulation breakdown may occur. Over time, the equipment's service life will shorten, and its components will accumulate varying degrees of wear. When defects accumulate to a certain severity, the contact resistance increases, and the contacts of GIS equipment will experience poor contact and overheating. Under the influence of external factors such as misoperation and overvoltage, faults will occur. According to the statistics in the international investigation report of the CIGRE 23.10 working group, the defects that cause accidents in GIS mainly include: (1) fixed protrusions; (2) residual metal particles; (3) defects in supporting insulators; (4) moisture; (5) insulation fit; (6) poor contact; (7) defects unrelated to insulation; (8) other defects. The probability distribution of GIS faults caused by different defect types is shown in the figure. Faults caused by poor contact account for nearly 1 / 3 of all GIS faults. If the overheating of GIS equipment is not detected and dealt with in time, it may cause hidden dangers such as poor insulation, poor contact and burnout, leading to a series of serious electrical accidents. Overheating faults mainly occur at contacts and connections, such as GIS disconnect switch contacts and GIS busbar insulators. The fault characteristics are mainly ablation, blackening or the appearance of powdery secondary products. According to the statistical analysis of GIS accidents by China Southern Power Grid from 2010 to 2015, the problem of abnormal temperature rise at conductor joints was prominent, accounting for 50% of all GIS faults in 2015.

[0003] For the contacts, due to the presence of contact resistance, a temperature rise will occur when current flows through the GIS equipment. Excessive changes in contact resistance will cause overheating of the GIS disconnect switch, and in severe cases, may even cause the contacts to melt and drip, leading to an accident. Therefore, when conducting electromagnetic-temperature-fluid coupling field simulations of GIS equipment, it is crucial to reflect the characteristics of the contact resistance in the simulation, which is key to achieving effective contact temperature simulation of GIS equipment.

[0004] Currently, many scholars have conducted extensive research on contact resistance and provided many theoretical derivations for reference. However, there is no practical and accurate simulation method for contact resistance simulation.

[0005] Hou Guobin of Xi'an Jiaotong University[1] equates the contact of all the fingers to a circular ring as a whole. By setting the conductivity of the ring, different contact situations are simulated. However, the contact resistance of each finger is not subdivided separately. The equivalent of the contact resistance is relatively rough and differs greatly from the actual contact resistance effect.

[0006] Niu Chunping et al. [2] determined the location of contact resistance and set the corresponding mesh node coupling area. That is, in the finite element simulation, the physical quantity transfer between two contacting conductors is only carried out through the coupled nodes to simulate the current contraction effect and realize the contact resistance simulation. This method is most suitable for the simulation of contact resistance, but the process of determining the mesh node coupling area for different contact resistances is cumbersome and complicated, which is not conducive to promotion. At the same time, it is only applicable to electromagnetic field calculations. In temperature-fluid field calculations, this method cannot realize the simulation of contact resistance.

[0007] Therefore, a method for simulating the contact resistance of GIS contacts is needed.

[0008] [1] Hou Guobin, Fu Mingli, Deng Xiaofeng, Wang Dibo, Li Xingwen, Zhuo Ran. Multiphysics simulation and experiment of temperature rise in GIS and heat flux distribution characteristics [J]. High Voltage Engineering, 2019, 45(07):2322-2328. DOI:10.13336 / j.1003-6520.hve.20190628018.

[0009] [2] Niu Chunping, Qiang Ruochen, Rong Mingzhe, Wang Zhen, Wang Xiaohua, Jin Guangyao. Simulation and experimental study on steady-state temperature rise of spring contact finger [J]. High Voltage Electric

[0010] Instrument, 2015, 51(03):8-14.DOI:10.13296 / j.1001-1609.hva.2015.03.002. Summary of the Invention

[0011] To address the shortcomings of the aforementioned solutions, this invention does not consider simulation through mesh node coupling. Instead, it achieves simulation by establishing an actual physical simulation model. However, it further refines the contact resistance simulation model, modeling and simulating the contact resistance of each finger. One challenge of existing solutions is that the contact resistance of each finger differs greatly in size from the surrounding model, making mesh generation difficult in finite element simulation.

[0012] According to one aspect of the present invention, a method for simulating the contact resistance of a GIS contactor is provided, comprising:

[0013] Calculate the equivalent radius of the contact resistance, and calculate the current-carrying cross-sectional area of ​​the contact resistance based on the equivalent radius;

[0014] Keeping the current-carrying cross-sectional area unchanged, the shape of the contact resistance is transformed into a rectangular block, and an equivalent contact resistance model is established for each finger in 3D software.

[0015] Perform model classification and fusion on the entire finger-touching area;

[0016] Calculate the resistivity corresponding to the contact resistance;

[0017] Based on the classification fusion and resistivity, the electromagnetic field mesh is divided into three-dimensional simulation models of GIS equipment, and electromagnetic field loss is calculated after the meshing is completed.

[0018] The completed 3D model is imported into the temperature and fluid field calculation platform to calculate the thermal conductivity of the contact resistance. Based on the thermal conductivity, the relevant properties of the contact resistance and other GIS equipment materials are set.

[0019] Based on the electromagnetic field loss, a heat source is set for the three-dimensional model after setting the thermal conductivity to obtain the final three-dimensional model;

[0020] The final three-dimensional model is meshed with a temperature-fluid field.

[0021] Select the solver for temperature-fluid field calculations, set the relevant solution parameters, and perform temperature-fluid field calculations.

[0022] Optionally, when converting the contact resistor shape into a rectangular block, the aspect ratio of the rectangular block is controlled to be less than 5:1 and the thickness to be less than 1mm.

[0023] Optionally, model classification and fusion are performed on the entire fingertip area, specifically including:

[0024] The SF6 in the finger-touch area is separated from the SF6 in the outer cavity, forming independent bodies;

[0025] The SF6 in the contact area is merged into a whole, while the volume occupied by the contact during insertion is removed;

[0026] The shielding cover and base are combined into one unit;

[0027] Set the mesh generation order.

[0028] Optionally, the SF6 in the finger contact area includes all SF6 present in the finger contact gap, contact resistance gap, shield gap, and base gap.

[0029] Optionally, the meshing sequence includes: meshing in the order of contact resistance, contact finger, SF6 gas, and the overall shielding cover. The meshing size of each part is determined according to the size of each part, but the size cannot have a difference of orders of magnitude, and the following conditions must be met: contact resistance size < contact finger size ≤ SF6 gas size ≤ overall shielding cover size.

[0030] Optionally, the equivalent radius of the contact resistance is calculated using Hall's law.

[0031] Optionally, the thermal conductivity of the contact resistance is calculated using the Wiedelmann-Franz law.

[0032] Optionally, performing temperature-fluid field meshing on the final three-dimensional model includes:

[0033] First, the finger region is meshed according to the electromagnetic field mesh; then, the remaining structures other than the finger region are meshed, and the SF6 fluid domain is meshed with a boundary layer.

[0034] Compared with existing technologies, the present invention has the following advantages:

[0035] 1. The present invention provides a method for simulating the contact resistance of GIS contacts. First, the equivalent radius of the contact resistance is calculated, and the current-carrying cross-sectional area of ​​the contact resistance is calculated based on the equivalent radius. Keeping the current-carrying cross-sectional area constant, the shape of the contact resistance is transformed into a rectangular block, and an equivalent contact resistance model is established for each contact finger in 3D software. Then, the entire contact finger region is classified and fused into models. In the electromagnetic field calculation, the conductivity is calculated by combining the magnitude of the contact resistance and the size of the equivalent model to simulate the working conditions of different contact resistances. In the temperature-fluid field coupling calculation, the thermal conductivity of the equivalent contact resistance is calculated by combining the magnitude of the contact resistance and the conductivity, and the loss calculation results of the electromagnetic field are imported into the temperature-fluid field, enabling accurate simulation of the contact resistance in the simulation. This invention provides an important reference for the temperature field simulation of GIS equipment contacts, laying an important simulation foundation for subsequent research on contact temperature monitoring of GIS equipment.

[0036] 2. To ensure that the simulated contact resistance closely approximates the actual engineering results, the contact resistance is equivalent to a rectangular block while maintaining a constant cross-sectional area. The aspect ratio must be controlled to be less than 5:1, and the thickness less than 1mm. Furthermore, a detailed contact resistance is established for each contact finger, without neglecting the influence of the shielding.

[0037] 3. To address the difficulty in meshing simulation models considering contact resistance, a meshing method with model classification and fusion and a characteristic meshing sequence was adopted. This method separates the SF6 in the contact finger area from the SF6 in the cavity, while merging all SF6 in the contact finger area into a single unit, and merging the shield and base into a single unit. The meshing sequence is set as: contact resistance, contact finger, SF6 gas, and shield as a whole. The meshing size of each part is determined based on the size of each part, but the size difference cannot exceed orders of magnitude, and should satisfy the condition: contact resistance size < contact finger size <= SF6 gas size <= shield as a whole. This achieves meshing of the contact portion considering contact resistance. Attached Figure Description

[0038] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only one embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a flowchart of a method for simulating the contact resistance of a GIS contactor according to an embodiment of the present invention;

[0040] Figure 2 This is a schematic diagram of the structure of each part of the finger-touching area according to an embodiment of the present invention;

[0041] Figure 3 This is an equivalent schematic diagram of contact resistance according to an embodiment of the present invention;

[0042] Figure 4 This is a schematic diagram of the mesh division of a single contact resistance according to an embodiment of the present invention;

[0043] Figure 5 This is a schematic diagram of the mesh division of all contact resistance areas according to an embodiment of the present invention;

[0044] Figure 6 This is a schematic diagram of SF6 fluid domain mesh partitioning according to an embodiment of the present invention. Detailed Implementation

[0045] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0046] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0047] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0048] According to an embodiment of the present invention, an embodiment of a method for simulating the contact resistance of a GIS contactor is provided. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0049] like Figure 1 This is a flowchart of a method for simulating the contact resistance of a GIS contactor according to an embodiment of the present invention, such as... Figure 1 As shown, this includes the following steps:

[0050] Step S1: Calculate the equivalent radius of the contact resistance, and calculate the current-carrying cross-sectional area of ​​the contact resistance based on the equivalent radius.

[0051] As an optional embodiment, the equivalent radius of the contact resistance is calculated using Hall's law, specifically including the following steps:

[0052] The contact radius between the two contacting bodies is:

[0053]

[0054] Among them, E * R is the equivalent elastic modulus, R is the radius of the spherical object, and F is the contact stress.

[0055] According to Hall's law, the equivalent radius of the contact resistance of the GIS contactor can be derived as follows:

[0056]

[0057] Where R1 and R2 are the radii of the contact finger and contact head on the contact arc surface, respectively.

[0058] Step S2: Keeping the current-carrying cross-sectional area unchanged, transform the contact resistance shape into a rectangular block, and establish an equivalent contact resistance model for each finger in the 3D software.

[0059] As an optional embodiment, based on the current-carrying cross-sectional area calculated in step S1, keeping the current-carrying cross-sectional area unchanged, the contact resistance shape is transformed into a rectangular block and modeled in Solidworks software. It is important to note that the aspect ratio should be kept within 5:1, mainly to avoid extreme aspect ratios causing the equivalent contact resistance model to exceed the width of the finger itself. Simultaneously, the contact resistance thickness should be controlled within 1mm. If the equivalent contact resistance is too thick, the simulated contact resistance will differ significantly from the actual engineering resistance, failing to meet the original purpose of equivalence. The structure of each part of the finger region is as follows: Figure 2 As shown, the equivalent schematic diagram of contact resistance is as follows: Figure 3 As shown.

[0060] Step S3: Perform model classification and fusion on the entire finger area. This step is mainly to achieve mesh partitioning when considering contact resistance.

[0061] As an optional embodiment, taking a 110kV GIS disconnector as an example, the contact finger area mainly includes: 36 contact fingers, 72 contact resistors, contact base, shielding cover, and the SF6 gap surrounded by all components. In the mesh generation, due to the large difference between the contact resistor size and the surrounding solid size, it is difficult to achieve mesh generation. Therefore, it is necessary to reasonably classify and merge the contact finger area. Step S3 specifically includes:

[0062] Step S31: Separate the SF6 in the finger-touch area from the SF6 in the outer cavity to form independent bodies;

[0063] Step S32: Merge the SF6 of the contact finger area into a whole, and remove the volume occupied by the contact when it is inserted; wherein, the SF6 of the contact finger area includes all the SF6 existing in the contact finger gap, contact resistance gap, shield gap and base gap;

[0064] Step S33: Combine the shielding cover and the base into a single unit;

[0065] Step S34: Set the meshing sequence. The meshing sequence includes: meshing in the order of contact resistance, contact fingers, SF6 gas, and the overall shielding cover. The meshing size of each part is determined according to the size of each part, but the size difference cannot be across orders of magnitude (for example, from the perspective of units, the maximum mesh size of the contact resistance should be controlled within 1mm, the maximum mesh size of the conductor in contact with the contact resistance should be controlled within 10mm, and the other adjacent parts should be the same). Furthermore, it must satisfy the following condition: contact resistance size < contact finger size ≤ SF6 gas size ≤ overall shielding cover size. A meshing diagram is shown below. Figures 4-6 As shown.

[0066] Step S4: Calculate the resistivity corresponding to the contact resistance.

[0067] As an optional embodiment, according to the resistivity calculation formula The resistivity corresponding to the contact resistance is calculated, where ρ is the resistivity, R is the contact resistance value, s is the cross-sectional area through which the current flows through the contact resistance, and l is the length of the contact resistance in the direction of the current.

[0068] Step S5: Perform electromagnetic field meshing on the 3D simulation model of the GIS equipment according to the classification fusion and resistivity. After the meshing is completed, perform electromagnetic field loss calculation. First, the touch area needs to be meshed according to step S34 in step S3, and then the other parts of the model are meshed. After the meshing is completed, perform electromagnetic field loss calculation.

[0069] Step S6: Import the completed 3D model into the temperature and fluid field calculation platform, calculate the thermal conductivity of the contact resistance, and set the contact resistance and other relevant properties of GIS equipment materials based on the thermal conductivity.

[0070] As an optional embodiment, the thermal conductivity of the contact resistance is determined using the Weidlmann-Franz law. Calculate, where σ is thermal conductivity, λ is resistivity, and L is the Lorentz number, taken as a constant value of 2.44 × 10⁻⁶. -8 W·Ω·K -2 T represents absolute temperature.

[0071] Step S7: Set the heat source for the three-dimensional model with set thermal conductivity according to the electromagnetic field loss to obtain the final three-dimensional model.

[0072] Specifically, based on the electromagnetic field loss calculation completed in step S5, the loss values ​​of each part are extracted and used as a volume heat source to set the heat source for the relevant components in the temperature-fluid field calculation platform, thus realizing the import of the heat source.

[0073] Step S8: Perform temperature-fluid field mesh generation on the final three-dimensional model.

[0074] Specifically, step S8 includes:

[0075] First, the finger region is meshed according to the electromagnetic field mesh; then, the remaining structures other than the finger region are meshed, and the SF6 fluid domain is meshed with a boundary layer.

[0076] Step S9: Select the solver for temperature-fluid field calculation, set the relevant solution parameters, and perform temperature-fluid field calculation. This will enable the simulation calculation of the electromagnetic-temperature-fluid coupling field of GIS equipment considering contact resistance simulation.

[0077] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for simulating the contact resistance of a GIS contactor, characterized in that, include: Calculate the equivalent radius of the contact resistance, and calculate the current-carrying cross-sectional area of ​​the contact resistance based on the equivalent radius; Keeping the current-carrying cross-sectional area unchanged, the shape of the contact resistance is transformed into a rectangular block, and an equivalent contact resistance model is established for each finger in 3D software. The entire fingertip area is classified and fused using models, specifically including: The SF6 in the finger-touch area is separated from the SF6 in the outer cavity, forming independent bodies; The SF6 in the contact area is merged into a whole, while the volume occupied by the contact during insertion is removed; The shielding cover and base are combined into one unit; Set the mesh generation order; Calculate the resistivity corresponding to the contact resistance; Based on the classification fusion and resistivity, the electromagnetic field mesh is divided into three-dimensional simulation models of GIS equipment, and electromagnetic field loss is calculated after the meshing is completed. The completed 3D model is imported into the temperature and fluid field calculation platform to calculate the thermal conductivity of the contact resistance. Based on the thermal conductivity, the relevant properties of the contact resistance and other GIS equipment materials are set. Based on the electromagnetic field loss, a heat source is set for the three-dimensional model after setting the thermal conductivity to obtain the final three-dimensional model; The final three-dimensional model is meshed with a temperature-fluid field. Select the solver for temperature-fluid field calculations, set the relevant solution parameters, and perform temperature-fluid field calculations.

2. The method for simulating the contact resistance of GIS contacts according to claim 1, characterized in that, When converting the contact resistor shape into a rectangular block, the aspect ratio of the rectangular block is controlled to be less than 5:1 and the thickness to be less than 1mm.

3. The method for simulating the contact resistance of GIS contacts according to claim 1, characterized in that, The SF6 in the contact area includes all SF6 present in the contact gap, contact resistance gap, shield gap, and base gap.

4. The method for simulating the contact resistance of GIS contacts according to claim 1, characterized in that, The meshing sequence includes: meshing in the order of contact resistance, contact finger, SF6 gas, and the overall shielding cover. The meshing size of each part is determined according to the size of each part, but the size cannot have a difference of orders of magnitude, and the following conditions must be met: contact resistance size < contact finger size ≤ SF6 gas size ≤ overall shielding cover size.

5. The method for simulating the contact resistance of GIS contacts according to claim 1, characterized in that, The equivalent radius of the contact resistance is calculated using Hall's law.

6. The method for simulating the contact resistance of GIS contacts according to claim 1, characterized in that, The thermal conductivity of the contact resistance was calculated using the Wiedelmann-Franz law.

7. The method for simulating the contact resistance of GIS contacts according to claim 1, characterized in that, The temperature-fluid field meshing of the final three-dimensional model includes: First, the finger region is meshed according to the electromagnetic field mesh; then, the remaining structures other than the finger region are meshed, and the SF6 fluid domain is meshed with a boundary layer.

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