An oil tank explosion-proof capability examination method based on a scaled-down test

Abstract

This invention relates to a method for assessing the explosion-proof capability of fuel tanks based on scaled-down testing. Based on similarity theory, the π theorem, and an arc bubble dynamics model, a scaled-down criterion is obtained, and at least two length scaled-down coefficients are determined. Based on these coefficients, at least two scaled-down prototypes are designed, and a distortion coefficient is obtained based on the actual wall thickness of each prototype. Internal arc fault tests are conducted on each prototype, and pressure data, stress data, arcing time, test current, and test voltage at various measuring points within the fuel tank are collected and recorded. The pressure peak and stress peak values ​​of different scaled-down prototypes are compared to verify the effectiveness of the scaled-down criterion and the equivalence of the tests. By introducing a distortion coefficient, the nonlinear effects caused by processing limitations are effectively offset, enabling the scaled-down prototypes to more realistically reproduce the fault conditions of the original prototype.

Description

Technical Field

[0001] This invention relates to the field of pressure relief technology for power equipment, and in particular to a method for assessing the explosion-proof capability of fuel tanks based on scaled-down tests. Background Technology

[0002] Currently, with the continuous construction of ultra-high voltage (UHV) projects in my country, UHV transformers are not only core equipment of the UHV transmission system, but also play a crucial role in the long-distance, high-capacity, and low-loss power transmission. They can step up the voltage of electricity generated by power plants to 1000kV and above, enabling efficient transmission over thousands of kilometers. This supports the backbone of the national power grid and the optimized allocation of energy resources, directly impacting national energy security and the stable power supply for people's production and daily life. If an UHV transformer fails, the power supply to the entire region and even the entire country may face the risk of widespread disruption.

[0003] In recent years, several deflagration accidents have occurred in my country's ultra-high-voltage (UHV) power transmission projects, severely impacting the stability of the power system and causing significant social disruption. Arc faults are typically caused by winding insulation breakdown, short circuits, or overvoltage; therefore, UHV converter transformers inevitably experience arc faults during operation. When an arc fault occurs inside the transformer, the arc instantly releases enormous energy (tens of megajoules), causing the insulating oil to rapidly vaporize and decompose, violently generating large amounts of high-temperature, high-pressure flammable gases (such as hydrogen, methane, and acetylene). These gases rapidly accumulate within the confined space of the tank, forming an extreme high-pressure shock wave. This pressure wave repeatedly propagates, reflects, and converges within the large cavity, subjecting the bottom and side walls of the tank to megapascal-level pressures, which can easily cause deformation, tearing, or even explosion of the tank walls.

[0004] Arc faults in actual ultra-high voltage converter transformers can generate tens of megajoules, while high-energy arc tests can only reach a maximum of twenty-odd megajoules and carry a high risk factor. Directly conducting full-scale arc fault tests faces multiple technical and safety barriers. The instantaneous release of a high-voltage arc poses an extremely high risk of tank explosion, potentially leading to fires and casualties. Furthermore, the tests require extremely demanding conditions, including ultra-large-scale high-voltage test sites, specialized explosion-proof equipment, and massive amounts of insulating oil, resulting in very high costs and limited test energy (maximum twenty-odd megajoules), making it impossible to realistically reproduce the high-energy arc faults of actual scenarios.

[0005] Therefore, conducting arc testing on large-scale oil-filled ultra-high voltage (UHV) equipment faces challenges such as high cost, significant risks, and complex development of testing equipment. A scaled-down equivalent testing method is needed. The equivalent scaling-down technique, by developing a prototype scaled down by a certain coefficient, effectively maps high-energy faults from a large-scale prototype to a small-scale, low-energy model, significantly reducing the difficulty and risk of the test. The core of this technique lies in using the pressure distribution and stress conditions generated in a small cavity under low fault energy to simulate the pressure and stress response characteristics of a large cavity under high fault energy, ensuring a high degree of consistency between the two in terms of pressure peak value, fluctuation patterns, spatiotemporal distribution, and stress distribution.

[0006] However, during the development of the scaled-down prototype of the UHV converter transformer, limitations in manufacturing processes and material forming precision prevented perfect geometric similarity to the original, inevitably leading to processing distortion and consequently nonlinear changes in the distortion coefficient. This nonlinear distortion disrupts the linear mapping relationship of physical quantities in traditional scaling methods, resulting in significant deviations in the pressure response, stress distribution, and energy equivalence of the scaled-down prototype, severely impacting the equivalence of the scaled-down test. For example, the scaled-down tank wall thickness should be 2mm according to calculations, but in reality, only a minimum of 4mm steel plate can be manufactured, leading to distortion and resulting in nonlinear differences in structural stiffness. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for assessing the explosion-proof capability of fuel tanks based on scaled-down tests. Its advantage is that it can construct an anti-distortion similarity criterion based on similarity theory and the π theorem through dimensionless processing, and introduce a distortion coefficient to effectively offset the nonlinear effects caused by processing limitations, so that the scaled-down prototype can more realistically reproduce the failure conditions of the original prototype.

[0008] The above-mentioned objective of this invention is achieved through the following technical solution: a method for assessing the explosion-proof capability of fuel tanks based on scaled-down tests, comprising the following steps: Based on similarity theory, the π theorem, and the dynamic model of electric arc bubbles, a scaling criterion is obtained, and at least two length scaling coefficients are determined. , ,in ≠ The scaling criterion is as follows: under the premise of satisfying pressure equivalence, the arc energy is scaled according to the volume scaling factor, and the arcing time is scaled according to the length scaling factor. According to the length scaling factor , Design at least two scaled-down prototypes and obtain the distortion coefficients based on the actual wall thickness of the scaled-down prototypes. Internal arc fault tests were conducted on each of the scaled-down prototypes. Pressure data, stress data, arcing time, test current, and test voltage were collected and recorded at each measuring point in the oil tank of the scaled-down prototype. The pressure data, stress data, arcing time, test current, and test voltage were corrected according to the distortion coefficient. By comparing the initial pressure peak and peak stress of different scaled-down prototypes, the effectiveness of the scaled-down criterion and the equivalence of the experiment are verified.

[0009] Preferably, the method for assessing the explosion-proof capability of fuel tanks based on scaled-down tests provided by the present invention is based on the length scaling factor. , Design at least two scaled-down prototypes, and obtain the distortion coefficient based on the actual wall thickness of the scaled-down prototypes, including: Calculate the length, width, height, and ideal wall thickness of the scaled-down prototype based on the length scaling factor. Due to limitations in the processing technology, the actual wall thickness is determined, and the distortion coefficient is calculated based on the length scaling factor and the thickness scaling factor. Pressure sensors and strain gauges were arranged on the scaled-down prototype to determine the location of the measurement points.

[0010] Preferably, the method for assessing the explosion-proof capability of fuel tanks based on scaled-down tests provided by the present invention obtains scaled-down criteria based on similarity theory, the π theorem, and an electric arc bubble dynamics model, including: The dynamic equation of arc-induced bubbles in a finite domain is: (1) In equation (1), For time; Radial position; The pressure of the liquid; For the density of oil, we can take it as . ; This represents the pressure at the boundary of a finite field; Specific heat ratio; The dynamic viscosity of insulating oil; The surface tension coefficient of the insulating oil; The initial internal energy of the bubble, The heat transferred is defined as R is the bubble radius; The specified radius at the boundary of the finite field; From equation (1), it can be seen that the arc energy is mainly related to the physical quantities of the initial internal energy oil of the bubble, such as density, dynamic viscosity, and surface tension coefficient. The arc energy is: (2) From equation (2), the dimensionless number of the electric arc energy is: (3) By setting the dimensionless numbers of the scaled-down model and the prototype to be equal, the scaling law for arc energy is derived as follows: (4) In equation (4), Dimensionless numbers based on the prototype is the dimensionless number of the scaled-down model; From equations (1) to (4), the scaling criterion is derived as follows: (5) (6) In equation (5), The prototype of electric arc energy; The arc energy is for a scaled-down model; This is the length scaling factor; In formula (6) Arc time for prototype; This represents the arcing time in a scaled-down model. This is the length scaling factor.

[0011] Preferably, in the method for assessing the explosion-proof capability of fuel tanks based on scaled-down tests provided by the present invention, the formula for calculating the thickness scaled-down coefficient is as follows: In the formula, This is the thickness reduction factor; The wall thickness is based on the prototype. This represents the actual wall thickness of the scaled-down prototype.

[0012] Preferably, in the method for assessing the explosion-proof capability of fuel tanks based on scaled-down tests provided by the present invention, the formula for calculating the distortion coefficient is as follows: In the formula, The distortion coefficient; This is the length scaling factor; This is the thickness scaling factor.

[0013] Preferably, the method for assessing the explosion-proof capability of fuel tanks based on scale-down testing provided by the present invention includes arranging pressure sensors on the scale-down prototype, comprising: Pressure sensors are arranged at the bottom of the oil tank, the long axis side wall, the short axis side wall of the riser, the vertical weld of the short axis of the riser, and the horizontal weld of the long axis side of the riser in the scaled-down prototype. Alternatively, pressure sensors are arranged at the bottom of the oil tank, the long axis side wall, the short axis side wall of the riser, the vertical weld of the short axis of the riser, the horizontal weld of the long axis side of the riser, the vertical weld of the short axis side of the valve, and the horizontal weld of the long axis side of the valve.

[0014] Preferably, the method for assessing the explosion-proof capability of fuel tanks based on scaled-down tests provided by the present invention includes arranging strain gauges on the scaled-down prototype, comprising: Strain gauges are arranged on the long axis sidewall, the short axis sidewall of the riser, the vertical weld of the short axis of the riser, the horizontal weld of the long axis side of the riser, and the top center position of the oil tank in the scaled-down prototype. Alternatively, strain gauges are arranged on the long axis sidewall, the short axis sidewall of the riser, the vertical weld of the short axis of the riser, the horizontal weld of the long axis side of the riser, the top center, and the middle position of the horizontal weld of the long axis side of the oil tank in the scaled-down prototype.

[0015] Preferably, in the method for assessing the explosion-proof capability of fuel tanks based on scaled-down tests provided by the present invention, the formula for calculating the length of the scaled-down prototype is as follows: In the formula, This is the length value of the scaled-down prototype; The length value of the prototype.

[0016] Preferably, in the method for assessing the explosion-proof capability of fuel tanks based on scale-down testing provided by the present invention, the formula for calculating the width of the scale-down prototype is as follows: In the formula, This is the width value of the scaled-down prototype; The width value of the prototype.

[0017] Preferably, in the method for assessing the explosion-proof capability of fuel tanks based on scale-down testing provided by the present invention, the formula for calculating the height of the scale-down prototype is as follows: In the formula, This is the height value of the scaled-down prototype; The height value of the prototype.

[0018] In summary, the beneficial technical effects of this invention are as follows: The method for assessing the explosion-proof capability of fuel tanks based on scaled-down tests provided in this application includes the following steps: obtaining scaled-down criteria based on similarity theory, the π theorem, and the arc bubble dynamics model, and determining at least two length scaled-down coefficients. , According to the length scaling factor , At least two scaled-down prototypes were designed, and the distortion coefficient was obtained based on the actual wall thickness of the scaled-down prototypes. Internal arc fault tests were conducted on each scaled-down prototype, and pressure data, stress data, arcing time, test current, and test voltage at various measuring points in the tank of the scaled-down prototype were collected and recorded. The pressure data, stress data, arcing time, test current, and test voltage were corrected according to the distortion coefficient. The pressure peak and stress peak of different scaled-down prototypes were compared to verify the effectiveness of the scaling criterion and the equivalence of the test. On the one hand, by adopting the scaling criterion, the large-size prototype tank was scaled down to a small cavity model, which greatly reduced the risk factor and test cost, thereby safely and economically verifying the explosion-proof performance, filling the gap in direct high-energy testing, and providing a reliable basis for the explosion-proof design of UHV converter transformers. On the other hand, by introducing the distortion coefficient, the nonlinear effects caused by processing limitations were effectively offset, enabling the scaled-down prototype to more realistically reproduce the fault conditions of the prototype. Attached Figure Description

[0019] Figure 1 This is a flowchart of a method for assessing the explosion-proof capability of fuel tanks based on scaled-down tests, provided in an embodiment of the present invention.

[0020] Figure 2 This is a schematic diagram of a 110kV scale oil tank developed using a length scaling factor of 2.5 in the oil tank explosion-proof capability assessment method based on scaled-down testing provided in this embodiment of the invention.

[0021] Figure 3 This is a schematic diagram of a 35kV scale oil tank developed using a length scaling factor of 2.5 in the oil tank explosion-proof capability assessment method based on scaled-down testing provided in this embodiment of the invention.

[0022] Figure 4 This is a schematic diagram of a 35kV scale oil tank developed using a length scaling factor of 6.25 and a thickness scaling factor of 3 in the oil tank explosion-proof capability assessment method based on scaled-down testing provided in this embodiment of the invention.

[0023] Figure 5 This refers to the relative positions of pressure and strain measurement points in the fuel tank explosion-proof capability assessment method based on scaled-down tests provided in this embodiment of the invention. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to the accompanying drawings.

[0025] Reference Figure 1 The present invention discloses a method for assessing the explosion-proof capability of fuel tanks based on scaled-down tests, comprising the following steps: S101. Based on similarity theory, the π theorem, and the electric arc bubble dynamics model, a scaling criterion is obtained, and at least two length scaling coefficients are determined. , ,in ≠ The scaling criterion is as follows: under the premise of satisfying pressure equivalence, the arc energy is scaled according to the volume scaling factor, and the arcing time is scaled according to the length scaling factor. S102, Based on the length scaling factor , Design at least two scaled-down prototypes and obtain the distortion coefficients based on the actual wall thickness of the scaled-down prototypes; S103. Conduct internal arc fault tests on each scaled-down prototype, collect and record pressure data, stress data, arcing time, test current and test voltage at each measuring point in the oil tank of the scaled-down prototype, and correct the pressure data, stress data, arcing time, test current and test voltage according to the distortion coefficient. S104. By comparing the initial pressure peak and stress peak of different scaled-down prototypes, the effectiveness of the scaling-down criterion and the equivalence of the test are verified. On the one hand, by adopting the scaling-down criterion, the large-size prototype oil tank is scaled down to a small cavity model, which greatly reduces the risk factor and cost of the test, thereby verifying the explosion-proof performance safely and economically, filling the gap in direct high-energy testing, and providing a reliable basis for the explosion-proof design of UHV converter transformers. On the other hand, by introducing a distortion coefficient, the nonlinear effects caused by processing limitations are effectively offset, enabling the scaled-down prototype to more realistically reproduce the failure conditions of the prototype. In addition, by verifying the scaling-down criterion through multi-scale prototype comparison, it is ensured that the test data can be effectively used to deduce the prototype performance, forming a complete "design-test-verification" system.

[0026] This embodiment deeply integrates similarity theory, arc bubble dynamics, and the π theorem. Targeting the structural characteristics and fault features of UHV converter transformers, it scales down time by length and energy by volume, while also considering nonlinear scaling effects. It utilizes a "small cavity, low energy" approach to simulate a "large cavity, high energy" approach. This method not only clarifies the design basis of the scaled-down prototype and avoids the risks of direct testing, but also ensures that the initial peak, distribution, and fluctuation characteristics of the pressure wave in the small cavity are consistent with those in the large cavity. This completely fills the technological gap in the field of UHV converter transformers regarding energy equivalence scaling and explosion-proof verification methods.

[0027] Furthermore, in this embodiment, S101, based on similarity theory, the Π theorem, and the electric arc bubble dynamics model, obtains the scaling criterion, including: To accurately describe the physicochemical process of gas bubble generation by electric arc in oil, considering the continuous injection of arc energy and the influence of various factors such as pressure, surface tension, and viscous force at the boundary of the finite domain on the gas bubble dynamics, the finite domain arc-induced gas bubble dynamics equation is used for analysis. The finite domain arc-induced gas bubble dynamics equation is as follows: (1) In equation (1), For time; Radial position; The pressure of the liquid; For the density of oil, we can take it as . ; This represents the pressure at the boundary of a finite field; Specific heat ratio; The dynamic viscosity of insulating oil; The surface tension coefficient of the insulating oil; The initial internal energy of the bubble, The heat transferred is defined as R is the bubble radius; The specified radius at the boundary of the finite field; From equation (1), it can be seen that the arc energy is mainly related to the physical quantities of the initial internal energy oil of the bubble, such as density, dynamic viscosity, and surface tension coefficient. The arc energy is: (2) From equation (2), we can see that if we select length, density, and time as the three basic dimensions, then the other five physical quantities are independent and can be represented by these three basic dimensions. Furthermore, we can perform dimensionless processing, where the dimensionless number of the arc energy is: (3) By setting the dimensionless numbers of the scaled-down model and the prototype to be equal, the scaling law for arc energy is derived as follows: (4) In equation (4), Dimensionless numbers based on the prototype is the dimensionless number of the scaled-down model; From equations (1) to (4), the scaling criterion is derived as follows: (5) (6) In equation (5), The prototype of electric arc energy; The arc energy is for a scaled-down model; This is the length scaling factor; In formula (6) Arc time for prototype; This represents the arcing time in a scaled-down model. This is the length scaling factor.

[0028] During the experiment, the prototype UHV converter oil tank was scaled down to an equivalent value. According to Equations (5) and (6), the appropriate length scaling factor can be determined as needed.

[0029] Furthermore, in this embodiment, S102, according to the length scaling factor... , Design at least two scaled-down prototypes and obtain the distortion coefficients based on the actual wall thickness of the scaled-down prototypes, including: S1021. Calculate the length, width, height, and ideal wall thickness of the scaled-down prototype based on the length scaling factor.

[0030] The formula for calculating the length of the scaled-down prototype is as follows: (7) In equation (7), This is the length value of the scaled-down prototype; The length value of the prototype.

[0031] The formula for calculating the width of the scaled-down prototype is: (8) In equation (8), This is the width value of the scaled-down prototype; The width value of the prototype.

[0032] The formula for calculating the height of the scaled-down prototype is: (9) In equation (9), This is the height value of the scaled-down prototype; The height value of the prototype.

[0033] The formula for calculating the ideal wall thickness of a scaled-down prototype is: (10) In equation (10), The ideal wall thickness for a scaled-down prototype; The wall thickness is based on the prototype.

[0034] S1022. Due to limitations in processing technology, the actual wall thickness is determined, and the distortion coefficient is calculated based on the length scaling factor and the thickness scaling factor.

[0035] Due to limitations in the manufacturing process, specifically the processing of the steel plates, the wall thickness of the oil tank in the scaled-down prototype cannot be designed according to the length scaling factor, which will cause distortion. To further reproduce the fault conditions under the ultra-high voltage scale, a distortion factor is introduced, and based on its equivalence, other physical quantities such as voltage, current, and pressure in the experiment are further corrected.

[0036] The formula for calculating the distortion coefficient is as follows: (11) In equation (11), The distortion coefficient; This is the length scaling factor; This is the thickness scaling factor.

[0037] Specifically, the formula for calculating the thickness reduction factor is as follows: In the formula, This is the thickness reduction factor; The wall thickness is based on the prototype. This represents the actual wall thickness of the scaled-down prototype.

[0038] S1023. Arrange pressure sensors and strain gauges on the scaled-down prototype and determine the location of the measurement points.

[0039] Continue to refer to Figure 5 In this embodiment, pressure sensors are arranged on the scaled-down prototype, including: pressure sensors are arranged at the bottom of the oil tank, the long axis sidewall, the short axis sidewall of the riser, the vertical weld of the short axis of the riser, and the horizontal weld of the long axis side of the riser in the scaled-down prototype; or, pressure sensors are arranged at the bottom of the oil tank, the long axis sidewall, the short axis sidewall of the riser, the vertical weld of the short axis of the riser, the horizontal weld of the long axis side of the riser, the vertical weld of the short axis of the valve, and the horizontal weld of the long axis side of the valve.

[0040] Specifically, taking the design of scaled-down prototypes at 110kV and 35kV levels as examples, in terms of pressure measurement, the 35kV scaled-down tank has pressure sensors arranged at five locations: the bottom, the long axis side wall, the short axis side wall of the riser seat, the vertical weld of the short axis of the riser seat, and the horizontal weld of the long axis side of the riser seat; the 110kV scaled-down tank has pressure sensors arranged at seven locations: the bottom, the long axis side wall, the short axis side wall of the riser seat, the vertical weld of the short axis of the riser seat, the horizontal weld of the long axis side of the riser seat, the vertical weld of the short axis side of the valve, and the horizontal weld of the long axis side.

[0041] Continue to refer to Figure 5 In this embodiment, strain gauges are arranged on the scaled-down prototype, including: strain gauges are arranged on the long axis sidewall of the oil tank, the short axis sidewall of the riser, the vertical weld of the short axis of the riser, the horizontal weld of the long axis side of the riser, and the top center position of the scaled-down prototype; or, strain gauges are arranged on the long axis sidewall of the oil tank, the short axis sidewall of the riser, the vertical weld of the short axis of the riser, the horizontal weld of the long axis side of the riser, the top center, and the middle position of the horizontal weld of the long axis side of the riser.

[0042] Specifically, taking the design of scaled-down prototypes at 110kV and 35kV as examples, in terms of strain measurement, strain gauges are arranged at five positions in the 35kV scaled-down tank: the side wall of the long axis, the side wall of the short axis of the riser, the vertical weld of the short axis of the riser, the horizontal weld of the long axis of the riser, and the center of the top. In the 110kV scaled-down tank, strain gauges are arranged at six positions: the side wall of the long axis, the side wall of the short axis of the riser, the vertical weld of the short axis of the riser, the horizontal weld of the long axis of the riser, the center of the top, and the middle of the horizontal weld of the long axis.

[0043] The following section uses a converter transformer prototype oil tank with dimensions of 10.5m long, 4.4m wide, 5.0m high, and 12mm thick as an example. Three types of scaled-down oil tanks were designed for explosion-proof verification. The structures of the three types of scaled-down oil tanks are shown in [reference needed]. Figures 2 to 4 As shown.

[0044] The first type of scaled-down oil tank is a 110kV scaled-down oil tank with a length scaling factor of 2.5 and a thickness scaling factor of 1.2 (i.e., the actual wall thickness of the first type of scaled-down oil tank is 10mm). See [link / reference]. Figure 2 The second type of scaled-down tank is a 35kV scaled-down tank with a length scaling factor of 6.25 and a thickness scaling factor of 1.5 (i.e., the actual wall thickness of the second type of scaled-down tank is 8mm). See [link / reference]. Figure 3 The third type of scaled oil tank is a 35kV scaled oil tank with a length scaling factor of 6.25 and a thickness scaling factor of 3 (i.e., the actual wall thickness of the third type of scaled oil tank is 4mm). Based on the principle of equivalent distortion factor, the distortion factor is taken as = length scaling factor / thickness scaling factor.

[0045] It should be noted that the 110kV scaled-down oil tank refers to the oil tank of the UHV converter transformer scaled down to the 110kV scaled-down oil tank; the 35kV scaled-down oil tank refers to the oil tank of the 110kV scaled-down oil tank scaled down to the 35kV scaled-down oil tank.

[0046] For ease of study, this experiment selected a 110kV scaled oil tank (first type) and a 35kV scaled oil tank (second type) with a length scaling factor of 2.5 and a thickness scaling factor of 2.5. Therefore, there is no distortion factor in this experiment.

[0047] Among them, the arc test using the first type of 110kV scaled-down oil tank model is shown in [reference]. Figure 2 An arc test was conducted with an effective current of 40 kA and an arcing time of 70 ms. Based on the measured arc voltage and current curves, the arc energy of this test was calculated through integration. =1.88MJ.

[0048] For the arc test of the second type of 35kV scaled-down oil tank, see [link to relevant documentation]. Figure 3 Its effective current is 13kA, arcing time is 30ms, and arc energy is 0.144MJ.

[0049] The results of the two sets of experiments show that the ratio of the arcing time of the two scaled-down prototypes is basically consistent with the length scaling factor, which satisfies the law of time scaling down according to length; the ratio of the arc energy of the two scaled-down prototypes is basically consistent with the cube of the length scaling factor, which satisfies the law of energy scaling down according to volume, thus verifying that the scaling criterion established in this invention is accurate and reliable.

[0050] Considering the differences in the specifications of the pressure relief devices in the two tests, in order to eliminate the interference of the pressure relief behavior on the pressure comparison results, the first peak of the pressure wave was selected for comparison. The pressure data of each measuring point are shown in Table 1. The test results show that the pressure response of the scaled-down oil tanks of 110kV and 35kV have good consistency, indicating that the scaled-down criterion of this application is correct and reliable.

[0051] Meanwhile, based on the principle of scaling up the arc energy by volume, the arc energy applied in the above two tests can be equivalent to the arc fault energy of the UHV prototype oil tank at the level of 30 MJ, which further verifies that this scaled-down test method can truly reflect the pressure impact characteristics of the prototype oil tank under actual fault conditions.

[0052] Table 1 The method for assessing the explosion-proof capability of fuel tanks based on scaled-down tests provided in this application includes the following steps: obtaining scaled-down criteria based on similarity theory, the π theorem, and the arc bubble dynamics model, and determining at least two length scaled-down coefficients. , According to the length scaling factor , At least two scaled-down prototypes were designed, and the distortion coefficient was obtained based on the actual wall thickness of the scaled-down prototypes. Internal arc fault tests were conducted on each scaled-down prototype, and pressure data, stress data, arcing time, test current, and test voltage at various measuring points in the tank of the scaled-down prototype were collected and recorded. The pressure data, stress data, arcing time, test current, and test voltage were corrected according to the distortion coefficient. The pressure peak and stress peak of different scaled-down prototypes were compared to verify the effectiveness of the scaling criterion and the equivalence of the test. On the one hand, by adopting the scaling criterion, the large-size prototype tank was scaled down to a small cavity model, which greatly reduced the risk factor and test cost, thereby safely and economically verifying the explosion-proof performance, filling the gap in direct high-energy testing, and providing a reliable basis for the explosion-proof design of UHV converter transformers. On the other hand, by introducing the distortion coefficient, the nonlinear effects caused by processing limitations were effectively offset, enabling the scaled-down prototype to more realistically reproduce the fault conditions of the prototype.

[0053] The beneficial technical effects of the oil tank explosion-proof capability assessment method based on scaled-down testing provided by this invention are as follows: By using test data (i.e., arc energy, arc time, pressure, and stress) from a scaled-down prototype, the UHV converter transformer prototype equipment is reverse-checked and corrected. This ultimately forms a complete explosion-proof verification test method, encompassing scaled-down model design, equivalent energy loading, pressure and stress data acquisition, and finally, equivalence verification. This test method has a clear process, strong operability and repeatability, and can be extended to scaled-down arc fault testing and explosion-proof verification of other large UHV oil-filled equipment such as UHV reactors in the future, providing a unified and scientific test method for the safety protection design of UHV power equipment.

[0054] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0055] Finally, it should be noted that the above embodiments are merely examples for clearly illustrating the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for assessing the explosion-proof capability of fuel tanks based on scaled-down tests, characterized in that: Includes the following steps: Based on similarity theory, the π theorem, and the dynamic model of electric arc bubbles, a scaling criterion is obtained, and at least two length scaling coefficients are determined. , ,in ≠ The scaling criterion is as follows: under the premise of satisfying pressure equivalence, the arc energy is scaled according to the volume scaling factor, and the arcing time is scaled according to the length scaling factor. According to the length scaling factor , Design at least two scaled-down prototypes and obtain the distortion coefficients based on the actual wall thickness of the scaled-down prototypes. Internal arc fault tests were conducted on each of the scaled-down prototypes. Pressure data, stress data, arcing time, test current, and test voltage were collected and recorded at each measuring point in the oil tank of the scaled-down prototype. The pressure data, stress data, arcing time, test current, and test voltage were corrected according to the distortion coefficient. By comparing the initial pressure peak and peak stress of different scaled-down prototypes, the effectiveness of the scaled-down criterion and the equivalence of the experiment are verified.

2. The method for assessing the explosion-proof capability of fuel tanks based on scaled-down tests according to claim 1, characterized in that: According to the length scaling factor , Design at least two scaled-down prototypes, and obtain the distortion coefficient based on the actual wall thickness of the scaled-down prototypes, including: Calculate the length, width, height, and ideal wall thickness of the scaled-down prototype based on the length scaling factor. Due to limitations in the processing technology, the actual wall thickness is determined, and the distortion coefficient is calculated based on the length scaling factor and the thickness scaling factor. Pressure sensors and strain gauges were arranged on the scaled-down prototype to determine the location of the measurement points.

3. The method for assessing the explosion-proof capability of fuel tanks based on scaled-down tests according to claim 2, characterized in that: Based on similarity theory, the π theorem, and the electric arc bubble dynamics model, the scaling criteria are obtained, including: The dynamic equation of arc-induced bubbles in a finite domain is: (1) In equation (1), For time; Radial position; The pressure of the liquid; For the density of oil, we can take it as . ; This represents the pressure at the boundary of a finite field; Specific heat ratio; The dynamic viscosity of insulating oil; The surface tension coefficient of the insulating oil; The initial internal energy of the bubble, The heat transferred is defined as R is the bubble radius; The specified radius at the boundary of the finite field; From equation (1), it can be seen that the arc energy is mainly related to the physical quantities of the initial internal energy oil of the bubble, such as density, dynamic viscosity, and surface tension coefficient. The arc energy is: （2） From equation (2), the dimensionless number of the electric arc energy is: （3） By setting the dimensionless numbers of the scaled-down model and the prototype to be equal, the scaling law for arc energy is derived as follows: （4） In equation (4), Dimensionless numbers based on the prototype is the dimensionless number of the scaled-down model; From equations (1) to (4), the scaling criterion is derived as follows: （5） （6） In equation (5), The prototype of electric arc energy; The arc energy is for a scaled-down model; This is the length scaling factor; In formula (6) Arc time for prototype; This represents the arcing time in a scaled-down model. This is the length scaling factor.

4. The method for assessing the explosion-proof capability of fuel tanks based on scaled-down tests according to claim 2, characterized in that: The formula for calculating the thickness reduction factor is: In the formula, This is the thickness reduction factor; The wall thickness is based on the prototype. This represents the actual wall thickness of the scaled-down prototype.

5. The method for assessing the explosion-proof capability of fuel tanks based on scaled-down tests according to claim 4, characterized in that: The formula for calculating the distortion coefficient is: In the formula, The distortion coefficient; This is the length scaling factor; This is the thickness scaling factor.

6. The method for assessing the explosion-proof capability of fuel tanks based on scaled-down tests according to claim 2, characterized in that: A pressure sensor is arranged on the scaled-down prototype, including: Pressure sensors are arranged at the bottom of the oil tank, the long axis side wall, the short axis side wall of the riser, the vertical weld of the short axis of the riser, and the horizontal weld of the long axis side of the riser in the scaled-down prototype. Alternatively, pressure sensors are arranged at the bottom of the oil tank, the long axis side wall, the short axis side wall of the riser, the vertical weld of the short axis of the riser, the horizontal weld of the long axis side of the riser, the vertical weld of the short axis side of the valve, and the horizontal weld of the long axis side of the valve.

7. The method for assessing the explosion-proof capability of fuel tanks based on scaled-down tests according to claim 2, characterized in that: Strain gauges are arranged on the scaled-down prototype, including: Strain gauges are arranged on the long axis sidewall, the short axis sidewall of the riser, the vertical weld of the short axis of the riser, the horizontal weld of the long axis side of the riser, and the top center position of the oil tank in the scaled-down prototype. Alternatively, strain gauges are arranged on the long axis sidewall, the short axis sidewall of the riser, the vertical weld of the short axis of the riser, the horizontal weld of the long axis side of the riser, the top center, and the middle position of the horizontal weld of the long axis side of the oil tank in the scaled-down prototype.

8. The method for assessing the explosion-proof capability of fuel tanks based on scaled-down tests according to claim 3, characterized in that: The formula for calculating the length of the scaled-down prototype is: In the formula, This is the length value of the scaled-down prototype; The length value of the prototype.

9. The method for assessing the explosion-proof capability of fuel tanks based on scaled-down tests according to claim 3, characterized in that: The formula for calculating the width of the scaled-down prototype is as follows: In the formula, This is the width value of the scaled-down prototype; The width value of the prototype.

10. The method for assessing the explosion-proof capability of fuel tanks based on scaled-down tests according to claim 3, characterized in that: The formula for calculating the height of the scaled-down prototype is as follows: In the formula, This is the height value of the scaled-down prototype; The height value of the prototype.

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