A design method for similarity scale model of transformer accident oil drainage
By designing a similar relationship between the transformer and the accident oil storage pit, the high cost and non-repeatability problems of oil drainage experiments after transformer explosions were solved, and similarity experiments of scaled models were realized, which reduced experimental costs and improved data authenticity.
Patent Information
- Application Number
- CN202411811541.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-10
- Publication Date
- 2025-09-19
- Estimated Expiration
- 2044-12-10
AI Technical Summary
In the existing technology, the oil drainage experiment after the transformer explosion is costly and not repeatable. The scaled model experiment needs to solve the problem of experimental similarity.
By calculating the dimensionless parameters of the prototype and the scaled model, the similarity relationship between the transformer and the accident oil storage pit was designed to ensure the similarity of the liquid level height and oil drainage time between the scaled model and the prototype, and the scaled model was used for experiments.
It reduces the experimental cost, improves the repeatability of the experiment and the authenticity of the data, and provides a reference for the design and modification of the accident oil discharge system.
Smart Images
Figure CN119647135B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of volume, flow, mass flow or liquid level measurement, and in particular to a design method of a transformer accident oil drainage similarity scale model. Background Art
[0002] After a transformer explodes, stress concentration locations such as the bushing riser often break and form cracks. Transformer oil flows out of the cracks to the accident oil pit at the transformer foundation. The oil in the accident oil pit is discharged to the total accident oil pool through the oil drain pipe at the oil drain port. Therefore, the leakage and discharge of transformer oil after a transformer explosion can be divided into two stages: (1) the oil in the transformer tank is discharged into the accident oil pit, and the accident oil pit is also in the oil discharge stage; (2) the oil in the transformer tank is completely discharged, and only the accident oil pit is in the oil discharge stage. In this process, if the leakage flow discharged into the accident oil pit is greater than the discharge volume of the accident oil pit, the amount of transformer oil retained in the accident oil pit will increase. When the retained oil volume exceeds the design capacity of the accident oil pit, the transformer oil will overflow and form a flowing fire, and the oil discharge process will fail; on the contrary, the amount of oil retained in the accident oil pit will continue to decrease until it is discharged to the total accident oil pool. The transformer oil will not form a flowing fire, and the oil discharge process will be successful. In order to study the oil discharge process, it is necessary to carry out relevant experiments. However, it is well known that full-scale model experiments or in-situ experiments are relatively expensive. If scaled-scale models can be used, the experimental costs can be significantly reduced. However, the biggest problem that scaled-scale experimental models need to solve is the experimental similarity between scaled-scale model experiments and prototype experiments. Therefore, it is necessary to conduct similarity research on scaled-scale model experiments.
[0003] However, the current common research methods for the problem of oil drainage after a transformer explosion are full-scale experiments and in-situ experiments, such as experiments on transformer accident oil pool fires with different oil pool diameters, and experiments on different fire extinguishing methods for transformer accident oil pool fires. This experimental method is generally expensive and lacks repeatability. Therefore, many scholars have also used numerical simulations, such as using DualSPHysics smooth particle dynamics calculation software to calculate and analyze the transformer oil drainage problem. Although this method is low-cost and highly controllable, it relies on the correctness of the model and the accuracy of the algorithm. High-precision calculation models require high-performance computers and a long time cost. Therefore, at this stage, it is necessary to combine the advantages and disadvantages of both and design a scaled model design method to study the oil drainage problem after a transformer explosion. However, the scaled model does not simply scale the geometric dimensions of the actual system, but rather maintains key physical properties similar to the original system. Summary of the Invention
[0004] In order to solve the problems in the prior art, the present invention provides a design method for a transformer accident oil drainage similarity scale model.
[0005] To implement the above technical solution, the specific steps of a design method for a transformer accident oil drainage similarity scale model are as follows:
[0006] S1. Calculate the dimensionless parameters of the prototype transformer and prototype accident oil storage pit;
[0007]
[0008] Where m is the ratio of the opening area at the root of the prototype transformer oil tank bushing to the effective cross-sectional area of the oil tank, A K is the opening area of the prototype transformer oil tank bushing root, A0 is the effective cross-sectional area of the prototype transformer oil tank; n is the ratio of the opening area of the prototype transformer oil tank bushing root to the effective cross-sectional area of the accident oil storage pit, A C is the effective cross-sectional area of the prototype accident oil storage pit; p is the ratio of the effective area of the prototype accident oil storage pit outlet to the effective cross-sectional area of the accident oil storage pit, A P The effective area of the oil outlet of the prototype accident oil storage pit;
[0009] S2. Obtain the similarity relationship m between the scaled model transformer and the prototype transformer based on the dimensionless parameter m, the initial transformer oil level in the prototype transformer, and the set similarity ratio. s and H 0s ; According to the dimensionless parameters n, p and the set similarity ratio, the similarity relationship n between the scaled model accident oil storage pit and the prototype accident oil storage pit is obtained s and p s , the specific steps are as follows:
[0010] S2.1. The scale model transformer and the prototype transformer have the following similarity relationship:
[0011]
[0012] Where m s is the ratio of the opening area at the root of the oil tank bushing of the scaled model transformer to the effective cross-sectional area of the oil tank; H0 is the initial transformer oil level in the prototype transformer; H 0s is the initial transformer oil level in the scaled model; a is the set similarity ratio;
[0013] S2.2. The scaled model accident oil storage pit and the prototype accident oil storage pit have the following similarity relationships:
[0014]
[0015] Where n s is the ratio of the opening area at the root of the transformer oil tank bushing to the effective cross-sectional area of the accident oil storage pit; sis the ratio of the effective area of the oil outlet of the scaled model accident oil storage pit to the effective cross-sectional area of the accident oil storage pit;
[0016] S3. Calculate the design parameters of the scale model transformer and the scale model accident oil storage pit;
[0017] When designing the scaled model, the parameters involved are shown in Table 1;
[0018] Table 1 Scale model design parameters and their descriptions
[0019]
[0020] Among them, H 0s The calculation method of A is shown in formula (2). 0s Determine according to experimental conditions. For the convenience of calculation and model processing, take A 0s =1m 2 ;
[0021] A Ks The calculation method is:
[0022] A Ks =a·m·A 0s (4)
[0023] A Cs The calculation method is:
[0024]
[0025] A Ps The calculation method is:
[0026] A Ps =a·p·A Cs (6)
[0027] S4. Calculate the similarity between the scaled model transformer and the prototype transformer, and between the scaled model accident oil storage pit and the prototype accident oil storage pit. The specific steps are as follows:
[0028] S4.1. Calculate the similarity between the scaled model transformer and the prototype transformer, specifically:
[0029] In the prototype system, when a transformer explodes, transformer oil leaks from the bushing rupture into the accident oil storage pit. At this time, the oil level in the transformer tank obeys the following quadratic function:
[0030]
[0031] Where H1(t) is the height of the prototype transformer oil level from the opening; t is time; g is the acceleration of gravity; C is the flow coefficient;
[0032] Substituting formula (1) into formula (7) we can obtain:
[0033]
[0034] The calculation expression for the time it takes to drain the transformer oil in the oil tank, i.e. the maximum oil draining time of the transformer, is as follows:
[0035]
[0036] Where, T 1max is the maximum oil draining time of the prototype transformer;
[0037] Substituting formula (1) into formula (9) we can obtain:
[0038]
[0039] For the scaled model transformer, the oil level of the scaled transformer model obeys the quadratic function consistent with the prototype transformer model. The specific expression is:
[0040]
[0041] Where H 1s (t) is the height of the oil level from the opening of the scale model transformer;
[0042] Substituting equations (2)-(6) into equation (11), we can obtain:
[0043]
[0044] It can be seen that the height of the transformer oil level from the opening between the scaled model transformer and the prototype transformer has a similar scale of 1:a 2 ;
[0045] Similarly, the maximum oil draining time of the scale model transformer tank satisfies:
[0046]
[0047] Where, is the maximum oil draining time of the scale model transformer;
[0048] Substituting equations (2)-(6) into equation (13), we can obtain:
[0049]
[0050] It can be seen that the maximum oil draining time of the transformer between the scaled model transformer and the prototype transformer has a similar scale of 1:1;
[0051] S4.2. Calculate the similarity between the scaled model accident oil pit and the prototype accident oil pit. Specifically, analyze the following two phases: the oil in the transformer tank is drained into the accident oil pit, and the accident oil pit is also drained (phase 1). The oil in the transformer tank is drained, and only the accident oil pit is drained (phase 2). The specific analysis is as follows:
[0052] S4.2.1. In the prototype system, when the oil in the transformer tank is discharged into the accident oil storage pit, and the accident oil storage pit is also in the oil discharge stage (t≤T max ), the oil level in the accident oil storage pit satisfies the following differential equation:
[0053]
[0054] Where H 2,1 (t) is the height of the liquid level in the prototype accident oil storage pit from the oil discharge port during the first stage;
[0055] Substituting formula (1) into formula (15) we can obtain:
[0056]
[0057] For the scaled model accident oil storage pit, when the oil in the transformer tank is discharged into the accident oil storage pit and the accident oil storage pit is also in the oil discharge stage, the oil level height of the scaled model accident oil storage pit also satisfies the following differential equation:
[0058]
[0059] Substituting equations (2)-(6) into equation (17), we obtain:
[0060]
[0061] Comparing Equation (16) with Equation (18), it is not difficult to find that in this stage, the oil level height of the scaled model and the prototype accident oil storage pit has the following similar scale:
[0062]
[0063] It can be seen that in this stage, the height of the oil discharge port between the scaled model accident oil storage pit and the prototype accident oil storage pit has a similar scale of 1:a 2 ;
[0064] S4.2.2 In the prototype system, after the oil in the transformer tank is drained and only the emergency oil storage pit is drained, the oil level in the emergency oil storage pit is expressed as follows:
[0065]
[0066] Where H2,2 (t) is the height from the liquid level in the prototype accident oil storage pit to the oil discharge port during the second stage; H 2max It's T 1max The height of the oil level in the prototype accident oil storage pit at the moment;
[0067] Substituting formula (1) into formula (20) we can obtain:
[0068]
[0069] For the scaled model accident oil storage pit, this stage also satisfies expression (20). From the above analysis, it can be seen that the oil draining of the prototype transformer tank and the scaled model have a similar scale of 1:1 in time. Therefore, when the transformer tank in the scaled model is drained,
[0070]
[0071] From this we can get:
[0072]
[0073] Where, is the height from the liquid level in the scaled model accident oil storage pit to the oil drain port in the second stage. It can be seen that in this stage, the height from the liquid level in the scaled model to the oil drain port has a similar scale of 1:a between the scaled model and the prototype accident oil storage pit. 2 ;
[0074] In the prototype, the maximum oil discharge time of the accident oil storage pit is expressed as:
[0075]
[0076] Where, T 2max is the maximum oil draining time of the prototype system;
[0077] From the above analysis, we can know that the maximum oil discharge time of the scaled model accident oil storage pit is expressed as:
[0078]
[0079] It can be seen that the similarity scale of the maximum oil discharge time between the prototype accident oil storage pit and the scaled model is 1:1;
[0080] Summarizing the above analysis, it can be seen that the liquid level changes between the scale model transformer and the scale model accident oil storage pit designed by the present invention and the prototype transformer and the accident oil storage pit have a similar scale of 1:a 2 ;The similarity scale of oil discharge time is 1:1;
[0081] S5. Make a scale model according to the design parameters;
[0082] The scale model includes: a scale model transformer and a scale model accident oil storage pit;
[0083] S6. Conduct scaled-down experiments based on existing transformers to verify the effectiveness of the scaled-down model.
[0084] Beneficial effects of the present invention
[0085] 1. Replace the currently common full-scale experiments and in-situ experiments, thereby achieving the goal of reducing costs and repeatable experiments;
[0086] 2. Replace numerical simulation methods, reduce the requirements for personnel and computer equipment, reduce time costs, and also improve the authenticity of data;
[0087] 3. Through the scaled model experiment, a reference can be provided for the design and modification of the emergency oil discharge system. BRIEF DESCRIPTION OF THE DRAWINGS
[0088] Figure 1 Flowchart of the present invention;
[0089] Figure 2 This is a simplified schematic diagram of an oil-immersed transformer and an emergency oil storage pit;
[0090] Figure 3 This is a schematic diagram of a scaled transformer oil tank;
[0091] Figure 4 This is a scaled-down picture of the transformer oil tank;
[0092] Figure 5 This is a scaled schematic diagram of the accident oil storage pit;
[0093] Figure 6 This is a scaled-down picture of the accident oil storage pit;
[0094] Figure 7 Experimental process of filling the scale transformer oil tank with water to the set water level;
[0095] Figure 8 Drain the oil tank of a scale transformer and record the liquid level experimental process;
[0096] Figure 9 The experimental and theoretical values of the oil tank level change in the oil draining experiment of a 220kVA transformer scale model are shown;
[0097] Figure 10 The process of water filling experiment for the scaled accident oil storage pit;
[0098] Figure 11 Draining the scaled-down accident oil storage pit and recording the liquid level height experiment process;
[0099] Figure 12These are the experimental and theoretical values of the change in liquid level in the accident oil storage pit during the oil drainage experiment on a scaled model of a 220kVA transformer. DETAILED DESCRIPTION
[0100] The present invention will be further described in detail below with reference to specific embodiments.
[0101] A design method for a transformer accident oil drainage similarity scale model includes the following steps:
[0102] S1. Calculate the dimensionless parameters of the prototype transformer and prototype accident oil storage pit;
[0103] The calculation method of the dimensionless parameters of the prototype transformer and prototype accident oil storage pit is:
[0104]
[0105] Where m is the ratio of the opening area at the root of the prototype transformer oil tank bushing to the effective cross-sectional area of the oil tank, A K is the opening area of the prototype transformer oil tank bushing root, A0 is the effective cross-sectional area of the prototype transformer oil tank; n is the ratio of the opening area of the prototype transformer oil tank bushing root to the effective cross-sectional area of the accident oil storage pit, A C is the effective cross-sectional area of the prototype accident oil storage pit; p is the ratio of the effective area of the prototype accident oil storage pit outlet to the effective cross-sectional area of the accident oil storage pit, A P The effective area of the oil outlet of the prototype accident oil storage pit;
[0106] The embodiment of the present invention obtains the prototype design parameters of common transformers and accident oil storage pits. The dimensionless parameters obtained by combining formula (1) are shown in Table 2. The simplified schematic diagram of transformer accident oil drainage is shown in Figure 1 As shown;
[0107] Table 2 Common transformer design parameters and dimensionless parameters
[0108] parameter 500kVA 330kVA 220kVA 110kVA <![CDATA[H0]]> 5.900 5.600 4.790 2.640 <![CDATA[A0]]> 27.100 20.180 19.350 6.856 <![CDATA[A K ]]> 0.205 0.166 0.0995 0.051 <![CDATA[A C ]]> 72.000 51.600 42.00 9.000 <![CDATA[A P ]]> 0.126 0.070 0.070 0.030 <![CDATA[m=A K / A0(10 -3 )]]> 7.565 8.226 5.142 7.439 <![CDATA[n=A K / A C (10 -3 )]]> 2.847 3.217 2.369 5.667 <![CDATA[p=A P / A C (10 -3 )]]> 1.744 1.357 1.667 3.333
[0109] S2. Obtain the similarity relationship m between the scaled model transformer and the prototype transformer based on the dimensionless parameter m, the initial transformer oil level in the prototype transformer, and the set similarity ratio. s and H 0s ; According to the dimensionless parameters n, p and the set similarity ratio, the similarity relationship n between the scaled model accident oil storage pit and the prototype accident oil storage pit is obtained s and p s , the specific steps are as follows:
[0110] S2.1. Assume that the scaled model transformer and the prototype transformer have the following similarity relationship:
[0111]
[0112] Where m s is the ratio of the opening area at the root of the oil tank bushing of the scaled model transformer to the effective cross-sectional area of the oil tank; H0 is the initial transformer oil level in the prototype transformer; H 0s is the initial transformer oil level in the scaled model; a is the set similarity ratio;
[0113] S2.2. Assume that the scaled model accident oil storage pit and the prototype accident oil storage pit have the following similarity relationship:
[0114]
[0115] Where n s is the ratio of the opening area at the root of the transformer oil tank bushing to the effective cross-sectional area of the accident oil storage pit; s is the ratio of the effective area of the oil outlet of the scaled model accident oil storage pit to the effective cross-sectional area of the accident oil storage pit;
[0116] The similarity ratio a is set as needed. In the embodiment of the present invention, three common similarity ratios a=1 / 2, a=1 / 3, and a=1 / 4 are selected to design the scaled model.
[0117] S3. Calculate the design parameters of the scale model transformer and the scale model accident oil storage pit;
[0118] When designing the scaled model, the main parameters involved are shown in Table 1;
[0119] Table 1 Scale model design parameters and their descriptions
[0120]
[0121] Among them, H 0s The calculation method of A is shown in formula (2). 0s Determine according to experimental conditions. For the convenience of calculation and model processing, take A 0s =1m 2 ;
[0122] A Ks The calculation method is:
[0123] A Ks =a·m·A 0s (4)
[0124] A Cs The calculation method is:
[0125]
[0126] A Ps The calculation method is:
[0127] A Ps =a·p·A Cs (6)
[0128] According to formula (2) to formula (6), the scale model design parameters of transformers of different specifications under different similarity ratios a are calculated. The specific calculation results are shown in Table 3.
[0129] Table 3 Design parameters of scaled models of common transformers at different similarity ratios
[0130]
[0131]
[0132] D in the table s is the oil outlet diameter of the accident oil storage pit in the scaled model;
[0133] S4. Calculate the similarity between the scaled model transformer and the prototype transformer, and between the scaled model accident oil storage pit and the prototype accident oil storage pit. The specific steps are as follows:
[0134] S4.1. Calculate the similarity between the scaled model transformer and the prototype transformer, specifically:
[0135] In the prototype system, when a transformer explodes, transformer oil leaks from the bushing rupture into the accident oil storage pit. At this time, the oil level in the transformer tank obeys the following quadratic function:
[0136]
[0137] Where H1(t) is the height of the prototype transformer oil level from the opening; t is time; g is the acceleration of gravity; C is the flow coefficient;
[0138] Substituting formula (1) into formula (7) we can obtain:
[0139]
[0140] The calculation expression for the time it takes to drain the transformer oil in the oil tank, i.e. the maximum oil draining time of the transformer, is as follows:
[0141]
[0142] Where, T 1max is the maximum oil draining time of the prototype transformer;
[0143] Substituting formula (1) into formula (9) we can obtain:
[0144]
[0145] For the scaled model transformer, the oil level of the scaled transformer model obeys the quadratic function consistent with the prototype transformer model. The specific expression is:
[0146]
[0147] Where H 1s (t) is the height of the oil level from the opening of the scale model transformer;
[0148] Substituting equations (2)-(6) into equation (11), we can obtain:
[0149]
[0150] It can be seen that the height of the transformer oil level from the opening between the scaled model transformer and the prototype transformer has a similar scale of 1:a 2 ;
[0151] Similarly, the maximum oil draining time of the scale model transformer tank satisfies:
[0152]
[0153] Where, is the maximum oil draining time of the scale model transformer;
[0154] Substituting equations (2)-(6) into equation (13), we can obtain:
[0155]
[0156] It can be seen that the maximum oil draining time of the transformer between the scaled model transformer and the prototype transformer has a similar scale of 1:1;
[0157] S4.2. Calculate the similarity between the scaled model accident oil pit and the prototype accident oil pit. Specifically, analyze the following two phases: the oil in the transformer tank is drained into the accident oil pit, and the accident oil pit is also drained (phase 1). The oil in the transformer tank is drained, and only the accident oil pit is drained (phase 2). The specific analysis is as follows:
[0158] S4.2.1. In the prototype system, when the oil in the transformer tank is discharged into the accident oil storage pit, and the accident oil storage pit is also in the oil discharge stage (t≤T max ), the oil level in the accident oil storage pit satisfies the following differential equation:
[0159]
[0160] Where H 2,1 (t) is the height of the liquid level in the prototype accident oil storage pit from the oil discharge port during the first stage;
[0161] Substituting formula (1) into formula (15) we can obtain:
[0162]
[0163] For the scaled model accident oil storage pit, when the oil in the transformer tank is discharged into the accident oil storage pit and the accident oil storage pit is also in the oil discharge stage, the oil level height of the scaled model accident oil storage pit also satisfies the following differential equation:
[0164]
[0165] Where, is the height from the liquid level to the oil drain port in the scaled model accident oil storage pit during the first stage;
[0166] Substituting equations (2)-(6) into equation (17), we obtain:
[0167]
[0168] Comparing Equation (16) with Equation (18), it is not difficult to find that in this stage, the oil level height of the scaled model and the prototype accident oil storage pit has the following similar scale:
[0169]
[0170] It can be seen that in this stage, the height of the oil discharge port between the scaled model accident oil storage pit and the prototype accident oil storage pit has a similar scale of 1:a 2 ;
[0171] S4.2.2 In the prototype system, after the oil in the transformer tank is drained and only the emergency oil storage pit is drained, the oil level in the emergency oil storage pit is expressed as follows:
[0172]
[0173] Where H 2,2 (t) is the height from the liquid level in the prototype accident oil storage pit to the oil discharge port during the second stage; H 2max It's T 1max The height of the oil level in the prototype accident oil storage pit at the moment;
[0174] Substituting formula (1) into formula (20) we can obtain:
[0175]
[0176] For the scaled model accident oil storage pit, this stage also satisfies expression (20). From the above analysis, it can be seen that the oil draining of the prototype transformer tank and the scaled model have a similar scale of 1:1 in time. Therefore, when the transformer tank in the scaled model is drained,
[0177]
[0178] From this we can get:
[0179]
[0180] Where, is the height from the liquid level in the scaled model accident oil storage pit to the oil drain port in the second stage. It can be seen that in this stage, the height from the liquid level in the scaled model to the oil drain port has a similar scale of 1:a between the scaled model and the prototype accident oil storage pit. 2 ;
[0181] In the prototype, the maximum oil discharge time of the accident oil storage pit is expressed as:
[0182]
[0183] Where, T 2max is the maximum oil draining time of the prototype system;
[0184] From the above analysis, we can know that the maximum oil discharge time of the scaled model accident oil storage pit is expressed as:
[0185]
[0186] It can be seen that the maximum oil discharge time between the prototype accident oil storage pit and the scaled model is similar in scale of 1:1.
[0187] Summarizing the above analysis, it can be seen that the liquid level changes between the scale model transformer and the scale model accident oil storage pit designed by the present invention and the prototype transformer and the accident oil storage pit have a similar scale of 1:a 2 ; The oil discharge time similarity scale is 1:1.
[0188] S5. Make a scale model according to the design parameters. The specific steps are as follows:
[0189] The scale model includes: a scale model transformer and a scale model accident oil storage pit;
[0190] S5.1. Based on the design parameters in S3, the present invention selects a similarity ratio a=1 / 2 to produce a scaled model of the transformer and the accident oil storage pit; based on the similarity design parameters given in Table 3, the design parameters of the scaled transformer oil tank model are:
[0191] 1.0m long, 1.0m wide, 1.6m high (the height needs to be greater than the initial oil level of 1.475m);
[0192] In order to make the scaled model meet the oil drainage test of four transformer working conditions of 550kVA, 330kVA, 220kVA and 110kVA, four openings are set around the periphery with diameters of 69.4mm, 72.4mm, 57.2mm and 68.8mm respectively, and four initial oil level heights of 1.475m, 1.400m, 1.198m and 0.660m are set; the model designed according to the above parameters is shown in Figure 3 As shown, the actual completed Figure 4 As shown;
[0193] S5.2. Based on the similar design parameters given in Table 3, the design parameters for the scaled-down accident oil storage pit model are: width 1.0m, length 2.657m. To ensure that the scaled-down model can meet the oil drainage test requirements for four transformer operating conditions: 550kVA, 330kVA, 220kVA, and 110kVA, the lengthwise direction is divided into four compartments using three partitions. The first partition is located 2.556m from the end, the second partition is located 2.170m from the end, and the third partition is located 1.313m from the end. Each compartment has four openings with diameters of 46.76mm, 43.51mm, 43.96mm, and 46.10mm, respectively.
[0194] When designing the height of the scale model accident oil storage pit, it can be seen from the above that the cross-sectional area A of the transformer tank in the scale model is 0s Set to 1m 2 According to the initial liquid level of the oil in the tank, the transformer oil volumes corresponding to the four working conditions are: 1.475m 2 , 1.400m 2 、1.198m 2 , 0.600m 2 Assuming that all transformer oil flows into the accident oil storage pit and is not discharged, the maximum oil level height of the accident oil storage pit under four working conditions is: 1.475 / 2.657=0.5551m, 1.4 / 2.556=0.5477m, 1.198 / 2.17=0.5521m, 0.66 / 1.313=0.5027m, so when designing the scale model of the accident oil storage pit, the box height is greater than the above height. The height designed by the present invention is 0.65m; the model designed according to the above parameters is shown in FIG. Figure 5 As shown, the actual completed Figure 6 As shown;
[0195] S6. Perform a scaled-down experiment based on the existing transformer design parameters to verify the effectiveness of the scaled-down model. The specific steps are as follows:
[0196] S6.1. Taking a 220kVA transformer as an example, according to the above scaled model, use water as the medium to conduct the scaled transformer oil tank draining experiment, setting the initial oil level to 1.198m; use a stopwatch to measure the time when the liquid level reaches the upper edge of the opening, and use a camera to record the change of the liquid level. The test process is shown in Figure 6. Figure 7-Figure 8 The relevant test results are shown in Figure 9 As shown;
[0197] The main reasons for using water as the medium instead of oil are: 1. Transformer oil is flammable, so water is safer in comparison; 2. Water is more environmentally friendly than oil; 3. The present invention only considers the flow coefficient when calculating the similarity scale for the physical properties of the liquid. In other words, the correctness of the present invention can be verified regardless of whether it is oil or water discharge.
[0198] Figure 9 Combined with the actual leakage experiment of the scaled model, the time-varying curve of the liquid level calculated by the theoretical calculation of the scaled model and the time-varying curve of the measured liquid level were compared. The results showed that the experimental results were highly consistent with the theoretical calculation results.
[0199] S6.2. Taking a 220 kVA transformer as an example, according to the above scaled model, a scaled oil storage pit drainage experiment was conducted using water as the medium. The plate was placed 2.170 m from the end, and the variable orifice diameter was set to 43.96 mm. The specific steps are as follows:
[0200] S6.2.1. Pour water into the scaled tank model to the scaled model liquid level specified in Table 3;
[0201] S6.2.2. Install the bottom orifice plate in the accident oil storage tank according to the diameter specified in Table 3 and apply sealant to position it;
[0202] S6.2.3. Drain the water from the oil tank and simultaneously observe the level gauge on the accident oil storage tank model with a camera, recording the water level in the gauge at different times;
[0203] See the test process Figure 10-11 The relevant test results are shown in Figure 12 As shown;
[0204] Figure 12 The liquid level height variation curve obtained by theoretical calculation of scaled model and the measured liquid level height variation curve were compared. The results showed that the experimental results were highly consistent with the theoretical calculation results.
[0205] In summary, it is effective to simulate the transformer oil drainage process using a scaled model. The experimental similarity design method proposed in this invention can meet the requirements of scaled experiments and maintain a good similarity relationship. The theoretical calculation model for transformer oil leakage and accident oil storage tank drainage is effective. The theoretical value of the curve of the liquid level height changing with time in the scaled model oil drainage process is in good agreement with the experimental value. The scaled model can be verified by experiments.
Claims
1. A design method for a transformer accident oil drainage similarity scale model, characterized in that: The following steps are involved: S1. Calculate the dimensionless parameters of the prototype transformer and prototype accident oil storage pit; The dimensionless parameters include: m, n, and p; wherein m is the ratio of the opening area at the root of the prototype transformer oil tank bushing to the effective cross-sectional area of the prototype transformer oil tank, n is the ratio of the opening area at the root of the prototype transformer oil tank bushing to the effective cross-sectional area of the accident oil storage pit, and p is the ratio of the effective area of the oil outlet of the prototype accident oil storage pit to the effective cross-sectional area of the accident oil storage pit; S2. Obtain the similarity relationship m between the scaled model transformer and the prototype transformer based on the dimensionless parameter m, the initial transformer oil level H0 in the prototype transformer, and the set similarity ratio a. s and H 0s ; According to the dimensionless parameters n, p and the set similarity ratio, the similarity relationship n between the scaled model accident oil storage pit and the prototype accident oil storage pit is obtained s and p s ; The m s is the ratio of the opening area at the root of the bushing of the scaled model transformer tank to the effective cross-sectional area of the tank. 0s is the initial transformer oil level in the scaled model, and n s is the ratio of the opening area at the root of the scaled model transformer oil tank bushing to the effective cross-sectional area of the accident oil storage pit. s is the ratio of the effective area of the oil outlet of the scaled model accident oil storage pit to the effective cross-sectional area of the accident oil storage pit; S3. Calculate the design parameters of the scale model transformer and the scale model accident oil storage pit; The design parameters include: initial transformer oil level height H 0s , Transformer box effective cross-sectional area A 0s , Transformer bushing root opening area A Ks , Effective cross-sectional area A of the accident oil storage pit Cs 、Effective area of oil outlet of accident oil storage pit A Ps ; S4. Calculate the similarity between the scaled model transformer and the prototype transformer, and between the scaled model accident oil storage pit and the prototype accident oil storage pit; S5. Make a scale model according to the design parameters; The scale model includes: a scale model transformer and a scale model accident oil storage pit.
2. The design method of a transformer accident oil drainage similarity scale model according to claim 1 is characterized in that: The expression of the dimensionless parameter is as follows: ； Where m is the ratio of the opening area at the root of the prototype transformer oil tank bushing to the effective cross-sectional area of the oil tank, A K is the opening area of the prototype transformer oil tank bushing root, A0 is the effective cross-sectional area of the prototype transformer oil tank; n is the ratio of the opening area of the prototype transformer oil tank bushing root to the effective cross-sectional area of the accident oil storage pit, A C is the effective cross-sectional area of the prototype accident oil storage pit; p is the ratio of the effective area of the prototype accident oil storage pit outlet to the effective cross-sectional area of the accident oil storage pit, A P It is the effective area of the oil outlet of the prototype accident oil storage pit.
3. The design method of a transformer accident oil drainage similarity scale model according to claim 1 is characterized in that: The similarity relationship m between the scaled model transformer and the prototype transformer is obtained based on the dimensionless parameter m, the initial transformer oil level in the prototype transformer and the set similarity ratio. s and H 0s ; According to the dimensionless parameters n, p and the set similarity ratio, the similarity relationship n between the scaled model accident oil storage pit and the prototype accident oil storage pit is obtained s and p s The steps are as follows: S2.
1. The scale model transformer and the prototype transformer have the following similarity relationship: ； Where m s is the ratio of the opening area at the root of the oil tank bushing of the scaled model transformer to the effective cross-sectional area of the oil tank; H0 is the initial transformer oil level in the prototype transformer; H 0s is the initial transformer oil level in the scaled model; a is the similarity ratio; S2.
2. The scaled model accident oil storage pit and the prototype accident oil storage pit have the following similarity relationships: ； Where n s is the ratio of the opening area at the root of the scaled model transformer oil tank bushing to the effective cross-sectional area of the accident oil storage pit; s It is the ratio of the effective area of the oil outlet of the scaled accident oil storage pit to the effective cross-sectional area of the accident oil storage pit.
4. The design method of a transformer accident oil drainage similarity scale model according to claim 1 is characterized in that: Among the design parameters, the opening area A at the root of the transformer bushing of the scaled model is Ks , Effective cross-sectional area A of the scaled model accident oil storage pit Cs , Effective area A of the oil outlet of the scale model accident oil storage pit Ps The calculation method is as follows: A Ks The calculation method is: ； A Cs The calculation method is: ； A Ps The calculation method is: ； Where A 0s A represents the effective cross-sectional area of the scaled model transformer box. C is the effective cross-sectional area of the prototype accident oil storage pit.
5. The design method of a transformer accident oil drainage similarity scale model according to claim 1 is characterized in that: The method for calculating the similarity between the scale model transformer and the prototype transformer, and between the scale model accident oil storage pit and the prototype accident oil storage pit is as follows: S4.
1. Calculate the similarity between the scaled model transformer and the prototype transformer; The calculation expression for the height of the oil level from the opening of the scale model transformer is as follows: ； Where H 1s (t) is the height of the oil level of the scale model transformer from the opening; g is the acceleration of gravity; t is time; C is the flow coefficient; H1(t) is the height of the oil level of the prototype transformer from the opening; The maximum oil draining time calculation expression of the scale model transformer is as follows: ； Where, is the maximum oil draining time of the scale model transformer; T 1max is the maximum oil draining time of the prototype transformer; S4.
2. Calculate the similarity between the scaled model accident oil storage pit and the prototype accident oil storage pit, specifically divided into: (1) the oil in the transformer tank is drained into the accident oil storage pit, and the accident oil storage pit is also in the oil discharge stage; (2) the oil in the transformer tank is completely drained, and only the accident oil storage pit is in the oil discharge stage; S4.2.
1. When the oil in the transformer tank is drained into the accident oil storage pit and the accident oil storage pit is also in the oil draining stage, the oil level heights of the scaled model accident oil storage pit and the prototype accident oil storage pit have the following similar dimensions: ； Where, is the height from the liquid level in the scaled model accident oil storage pit to the oil discharge port in the first stage, is the similarity scale expression of the oil level height between the scaled model accident oil storage pit and the prototype accident oil storage pit; S4.2.
2. When the oil in the transformer tank is completely drained and only the accident oil storage pit is being drained, the calculation expression for the height of the liquid level in the scaled model accident oil storage pit from the oil drain port is as follows: ； Where, H is the height from the liquid level in the scaled model accident oil storage pit to the oil discharge port in the second stage. 2,2 (t) is the height from the liquid level in the prototype accident oil storage pit to the oil discharge port during the second stage, H 2max It's T 1max The height of the oil level in the prototype accident oil storage pit at the moment; The maximum oil discharge time of the scale model accident oil storage pit is expressed as: ； Where, T 2max is the maximum oil discharge time of the prototype accident oil storage pit, is the maximum oil discharge time of the scaled model accident oil storage pit.
Citation Information
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