Oil-immersed transformer oil tank shielding structure with phase change auxiliary heat dissipation function

Abstract

The invention discloses an oil-immersed transformer oil tank shielding structure with a phase change auxiliary heat dissipation function. The shielding structure comprises a phase change auxiliary heat dissipation shield and a radiator, and the radiator is arranged above the oil tank; the phase change auxiliary heat dissipation shield is mainly composed of a plurality of groups of hollow metal plates, each group of hollow metal plates comprises a plurality of hollow metal plates, and internal cavities of the hollow metal plates are filled with phase change cooling liquid; the hollow metal plate is arranged in the height direction of the oil tank, is parallel to the inner side wall of the oil tank and is connected with the inner side wall of the oil tank; the top end of the hollow metal plate extends out of the transformer oil tank and is connected with the radiator. While magnetic flux leakage shielding is carried out through the hollow metal sheets, heat exchange between the interior and the exterior of the transformer oil tank is achieved through circulation of the cooling liquid in the hollow metal sheets, and the overall heat dissipation capacity of the oil-immersed transformer is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of transformer magnetic shielding, and in particular to an oil-immersed transformer tank shielding structure with a phase change assisted heat dissipation function. Background Art

[0002] With the continuous increase in the capacity of oil-immersed transformers, cooling technology has become the key in the design and development of oil-immersed transformers. Due to its own structural characteristics, the oil-immersed transformer has a serious leakage magnetic field problem. The stray losses caused by the leakage magnetic field will lead to a reduction in the efficiency of the transformer and local overheating of the tank, seriously endangering the safe operation of the power transformer.

[0003] To solve the problem of tank heating, domestic and foreign scholars and manufacturers generally use the form of adding shielding to the tank to reduce the stray losses of the tank. The tank shielding of oil-immersed transformers can be divided into two categories: magnetic shielding and electrical shielding. Among them, magnetic shielding lays a magnetic conductive shielding material on the inner wall of the tank to guide the leakage magnetic flux into the magnetic shielding, thereby reducing the leakage magnetic flux and stray losses entering the tank wall and suppressing the local overheating of the tank caused by it. Magnetic shielding has significant application advantages in large-capacity and high-voltage transformers. Electrical shielding is to lay a conductive shielding material (usually an aluminum plate or a copper plate) on the inner wall of the tank. Due to the high conductivity of the shielding material, the leakage magnetic flux entering the conductive shielding material will generate an eddy current with a demagnetizing effect in it, and finally the leakage magnetic flux entering the tank wall is reduced. The electrical shielding structure is generally used in transformers with large usage and medium voltage levels. Although both magnetic shielding and electrical shielding can effectively shield the leakage magnetic flux, their shielding structures themselves will also generate losses, resulting in local overheating problems. Therefore, in view of the heating and heat dissipation characteristics of transformers, researching and developing a high-performance and high-reliability shielding system for transformers has important application value and significance. Summary of the Invention

[0004] The purpose of the present invention is to provide an oil-immersed transformer tank shielding structure with a phase change assisted heat dissipation function. The shielding structure is composed of multiple hollow metal plates filled with a phase change coolant. During operation, on the one hand, the hollow metal plate shell plays an electrical shielding role; on the other hand, the heat absorption of the filled coolant during phase change is utilized to form a two-phase coolant circulation in the hollow plate, quickly dissipating the heat in the shielding and the surrounding cooling oil, and improving the heat dissipation capacity of the transformer.

[0005] The technical solution adopted by the present invention is as follows:

[0006] 1. An oil-immersed transformer tank shielding structure with a phase change assisted heat dissipation function

[0007] The shielding structure includes a phase change assisted heat dissipation shield and a radiator, and the radiator is arranged above the fuel tank; the phase change assisted heat dissipation shield is mainly composed of several groups of hollow metal plates, each group of hollow metal plates includes multiple hollow metal plates, and a phase change coolant is filled in the internal cavity of the hollow metal plate; the hollow metal plates are arranged along the height direction of the fuel tank and are parallel to the inner wall of the fuel tank, and the hollow metal plates are connected to the inner wall of the fuel tank; the top end of the hollow metal plate extends to the outside of the transformer fuel tank and is connected to the radiator.

[0008] Specifically, at least one group of hollow metal plates is provided on each inner wall of the fuel tank; for each inner wall of the fuel tank, the number of groups of hollow metal plates is the same as the number and arrangement position distribution of the projections of the windings.

[0009] Specifically, the width of the hollow metal plate is greater than the width of the corresponding winding; the bottom height of the hollow metal plate is lower than the bottom height of the iron core inside the corresponding winding.

[0010] Specifically, in each group of hollow metal plates, the hollow metal plates are evenly arranged; in each group of hollow metal plates, the interval between adjacent hollow metal plates remains the same.

[0011] Specifically, the radiator uses an aluminum alloy fin radiator.

[0012] II. A structural optimization method for the shielding structure of an oil-immersed transformer fuel tank

[0013] The structural optimization method includes the following steps:

[0014] S1) Take the shielding spacing, shielding distance, and shielding length of the shielding structure of the oil-immersed transformer fuel tank as the structure parameters to be optimized, and select multiple different level parameters within the value range of each structure parameter to be optimized set in advance.

[0015] Optionally, the value range of the shielding spacing is 10 - 40 mm; the value range of the shielding distance is 100 mm - 250 mm; the value range of the shielding length is 3100 mm - 3400 mm.

[0016] S2) According to the structure parameters to be optimized and the level parameters obtained in step S1, use the Taguchi method to generate an orthogonal test table composed of multiple combinations of the structure parameters to be optimized.

[0017] S3) For each combination of the structure parameters to be optimized in the orthogonal test table, obtain the corresponding leakage magnetic flux density and winding temperature rise through simulation; combine the leakage magnetic flux density and winding temperature rise corresponding to all combinations of the structure parameters to be optimized to obtain the original data. In step S3, the process of obtaining the leakage magnetic flux density and winding temperature rise corresponding to each group of structure parameters to be optimized is specifically: obtain the leakage magnetic flux density and winding temperature rise distribution through numerical simulation.

[0018] S4) Perform mean value analysis and mean square deviation analysis on the original data obtained in step S3 to obtain the mean value of the magnetic flux leakage magnetic density, the mean square deviation of the magnetic flux leakage magnetic density, the mean value of the winding temperature rise, and the mean square deviation of the winding temperature rise corresponding to each structural parameter to be optimized.

[0019] S5) Using the Taguchi method, based on the mean value of the magnetic flux leakage magnetic density, the mean square deviation of the magnetic flux leakage magnetic density, the mean value of the winding temperature rise, and the mean square deviation of the winding temperature rise corresponding to each structural parameter to be optimized, obtain the optimal level parameters of each structural parameter to be optimized and use them as the optimal structural parameters. All the optimal structural parameters form an optimal structural parameter combination.

[0020] The beneficial effects of the present invention are as follows:

[0021] While the present invention conducts magnetic flux leakage shielding through a hollow metal plate, heat exchange between the inside and outside of the transformer tank is achieved through the circulation of the coolant inside the hollow metal plate. Compared with the traditional electric shielding structure, the overall heat dissipation capacity of the oil-immersed transformer can be significantly improved. Description of the Drawings

[0022] Figure 1 Schematic diagram of a transformer structure for installing an oil-immersed transformer tank shield with a phase change assisted heat dissipation function;

[0023] Figure 2 Schematic diagram of the structure of the hollow metal plate.

[0024] In the figure: 1. Radiator, 2. Phase change assisted heat dissipation shield, 3. Tank, 4. Winding, 5. Iron core, 6. Hollow metal plate, 7. Gaseous coolant, 8. Liquid coolant. Detailed Embodiments

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] The first aspect of the present invention provides an oil-immersed transformer tank shielding structure with a phase change assisted heat dissipation function.

[0027] As Figure 1 shown, the shielding structure of the present invention includes a phase change assisted heat dissipation shield 2 and a radiator 1. The radiator 1 is arranged above the tank 3. The phase change assisted heat dissipation shield 2 is mainly composed of several groups of hollow metal plates. Each group of hollow metal plates includes multiple hollow metal plates 6. The internal cavity of the hollow metal plate 6 is filled with a phase change coolant; the hollow metal plates 6 are arranged along the height direction of the tank 3 and are parallel to the inner wall of the tank 3. The hollow metal plates 6 are connected to the inner wall of the tank 3; the top end of the hollow metal plate 6 extends outside the transformer tank 3 and is connected to the radiator 1.

[0028] In the phase change assisted heat dissipation shield 2, the outer shell of the hollow metal plate 6 can absorb the leakage magnetic flux, reducing the stray losses caused by the leakage magnetic flux in the oil tank 3. When the transformer is operating, the heat generated by the winding 4 is first transferred to the outer wall of the hollow metal plate 6 through the cooling oil in the oil tank 3, and then transferred from the outer wall of the hollow metal plate 6 to the liquid coolant 8 inside it. Then, as the liquid coolant 8 evaporates from the liquid state to the gaseous state, the heat is transferred from the lower part of the phase change assisted heat dissipation shield 2 to the upper part of the phase change assisted heat dissipation shield 2, and finally guided to the radiator 1 outside above the transformer through the top outer shell of the hollow metal plate 6, and then dissipated from the outer surface of the radiator 1.

[0029] Specifically, at least one group of hollow metal plates is arranged on each of the four inner side walls of the oil tank 3. For each inner side wall of the oil tank 3, the number and arrangement positions of the hollow metal plate groups on the inner side wall are the same and aligned with the projection of the winding 4 on this inner side wall. In the embodiment of the present invention, three groups of hollow metal plates are arranged on each of the front and rear inner side walls of the oil tank 3, and one group of hollow metal plates is arranged on each of the left and right inner side walls.

[0030] Specifically, the width of the hollow metal plate 6 is greater than the width of the corresponding winding 4; the bottom height of the hollow metal plate 6 is lower than the bottom height of the inner iron core 5 of the corresponding winding 4.

[0031] Specifically, the hollow metal plates 6 in each group of hollow metal plates are evenly arranged; among the groups of hollow metal plates, the intervals between adjacent hollow metal plates 6 are kept consistent.

[0032] Preferably, the radiator 1 adopts an aluminum alloy fin radiator.

[0033] Specifically, the hollow metal plate 6 is connected to the radiator 1 by welding or mechanical connection. The mechanical connection can be bolt fixation, riveting or fixation using a connecting plate.

[0034] The second invention of the present invention provides a structural optimization method for the above-mentioned oil-immersed transformer oil tank shielding structure.

[0035] The structural optimization method of the present invention includes the following steps

[0036] The structural optimization method includes the following steps:

[0037] S1) Taking the shielding spacing, shielding distance, and shielding length of the oil-immersed transformer oil tank shielding structure as the structure parameters to be optimized, and selecting a plurality of different level parameters within the value range of each structure parameter to be optimized set in advance. Among them, the shielding spacing is the interval between adjacent hollow metal plates 6 in each group of hollow metal plates; the shielding distance is the distance between each group of hollow metal plates and the corresponding winding 4; the shielding length is the length between the top and bottom of the hollow metal thin plate, that is, the height of the hollow metal thin plate.

[0038] S2) According to the structural parameters to be optimized and the level parameters obtained in step S1, use the Taguchi method to generate an orthogonal test table composed of multiple combinations of the structural parameters to be optimized;

[0039] S3) For each combination of the structural parameters to be optimized in the orthogonal test table, under this combination of the structural parameters to be optimized, use numerical simulation to perform simulation to obtain the corresponding magnetic flux leakage density and winding temperature rise; combine the magnetic flux leakage density and winding temperature rise corresponding to all combinations of the structural parameters to be optimized to obtain the original data;

[0040] In step S3, the magnetic flux leakage density is the magnetic induction intensity generated in the space around the winding, iron core or other components due to the existence of leakage magnetic flux in the transformer; the magnetic flux leakage density is obtained through the following formula:

[0041]

[0042] In the formula, N is the number of turns of the winding; I is the current of the winding (A); R σ is the magnetic resistance of the leakage magnetic path (1 / H); A is the area through which the leakage magnetic flux passes (m 2 ), B σ is the magnetic flux leakage density;

[0043] The winding temperature rise is: the difference between the winding temperature and the ambient temperature during the operation of the transformer; the winding temperature rise is obtained through the following formula:

[0044]

[0045] In the formula, ΔT is the winding temperature rise, R 1 is the cold-state resistance (Ω); R 2 is the hot-state resistance (Ω); T 1 is the cold-state temperature (°C); k is a constant.

[0046] S4) Perform mean analysis and mean square deviation analysis on the original data obtained in step S3 to obtain the mean magnetic flux leakage density, mean square deviation of the magnetic flux leakage density, mean winding temperature rise, and mean square deviation of the winding temperature rise corresponding to each structural parameter to be optimized;

[0047] S5) Using the Taguchi method, according to the mean magnetic flux leakage density, mean square deviation of the magnetic flux leakage density, mean winding temperature rise, and mean square deviation of the winding temperature rise corresponding to each structural parameter to be optimized, obtain the optimal level parameter of each structural parameter to be optimized and use it as the optimal structural parameter, and all the optimal structural parameters form the optimal structural parameter combination.

[0048] The value range of the shielding distance is 10 to 40 mm; specifically: if the shielding distance is too small, it will affect the flow rate of the cooling oil in the shielding space, thereby affecting the heat transfer between the cooling oil in the fuel tank and the shielding structure, and ultimately affecting the heat dissipation effect; if the distance is too large, it will affect the shielding effect. Preferably, the number of levels is 4 (10 mm, 20 mm, 30 mm, 40 mm).

[0049] The value range of the shielding distance is 100 mm to 250 mm; specifically: if the shielding is too far from the winding, it will affect the heat transfer from the winding to the shielding structure, thereby affecting the heat dissipation effect; if it is too close, it will affect the shielding effect on the fuel tank. Preferably, the number of levels is 4 (100 mm, 150 mm, 200 mm, 250 mm).

[0050] The value range of the shielding length is 3100 mm to 3400 mm; preferably, the number of levels is 4 (3100 mm, 3200 mm, 3300 mm, 3400 mm).

[0051] The filling rate is preferably the medium filling rate. In specific implementation, for the shielding structures applied to different transformers, an appropriate filling rate can be selected to improve their heat dissipation capacity.

[0052] The specific embodiments of the present invention are as follows:

[0053] As Figure 1 shown, the phase change assisted heat dissipation shielding 2 structure in this embodiment is composed of multiple hollow metal plates 6, which are placed flat on the inner wall of the fuel tank 3 and parallel to the height direction of the inner wall. The lower end of the shielding is lower than the lower end of the iron core 5, and the upper end of the shielding extends outside the transformer fuel tank 3 and is connected to the radiator 1, and the width of each group of shielding structures is greater than the width of each phase winding 4. On the one hand, the outer shell of the hollow metal plate 6 can absorb the leakage magnetic flux, reducing the stray losses in the fuel tank caused by the leakage magnetic flux; on the other hand, when the transformer is operating, the heat generated by the winding is transferred to the phase change assisted heat dissipation shielding 2 by the cooling oil, and then guided to the radiator 1 outside the transformer, and then dissipated from the outer surface of the radiator 1.

[0054] As Figure 2 shown, a single shielding structure is composed of a hollow metal plate 6 and the phase change coolant inside. When the transformer is working, the lower part of the hollow metal plate 6 is heated, and the internal liquid coolant 8 is heated and evaporated into a gas, rising to the upper part of the hollow metal plate 6. In the cooling area at the upper part of the hollow metal plate 6, the gaseous coolant 7 will contact the lower temperature environment, cool down and condense into a liquid. The liquid coolant 8 drops to the heating area at the lower part of the hollow metal plate 6 due to the action of gravity, forming a two-phase coolant cycle.

[0055] The heat transfer performance of the heat pipe is evaluated by the equivalent thermal conductivity, and it is obtained that the equivalent thermal conductivity of the shielding structure is 80 times that of copper. The equivalent thermal conductivity can be obtained through the following formula:

[0056]

[0057] d o is the outer diameter (m) of the heat pipe shell; d i is the inner diameter (m) of the heat pipe shell; L is the length (m) of the heat pipe; λ is the thermal conductivity of the shell (W·(m·K) -1 )); e = L e / L, c = L c / L L e is the length (m) of the evaporation section; L c is the length (m) of the condensation section; α eff is the equivalent convective heat transfer coefficient W / (m 2 ·°C). In this embodiment, L = 2700 mm, d o = 200 mm, d i = 180 mm, L e = 900 mm, L c = 900 mm.

[0058] For the phase change assisted heat dissipation shield 2 in this embodiment, according to the above structural optimization method, by changing the length of the shield structure, the distance between the shield structure and the winding, and the distance between multiple hollow metal sheets, the shielding effect and heat dissipation effect of the shield structure can be optimized simultaneously. Further changing the type and amount of the cooling medium to change the heat dissipation effect will also cause corresponding changes in its equivalent thermal conductivity.

[0059] The heat transfer characteristics of the loop heat pipe vary with the filling ratio. Specifically, single-phase flow, intermittent boiling, and local instantaneous dryout occur under high, medium, and low filling ratios respectively. Under high filling ratio, as the heat flux density increases, the phase change is suppressed until it disappears, and single-phase flow appears in the pipe, with a significant increase in the outlet temperature of the evaporation section. Under medium filling ratio, obvious intermittent boiling instability occurs within a large range of heat flux density, and the outlet temperature of the evaporation section fluctuates violently. Under low heat flux density, when the heat flux density increases to a certain value, instantaneous dryout occurs in the evaporation section, causing significant overshoot and oscillation of the outlet temperature of the evaporation section. Therefore, for the shield structures applied to different transformers, an appropriate filling ratio can be selected to improve their heat dissipation capacity.

[0060] The above specific embodiments are used to explain and illustrate the present invention, rather than to limit the present invention. Any modifications and changes made within the spirit and scope of the claims of the present invention fall within the protection scope of the present invention.

[0061] The above are only the preferred embodiments of the present invention. Therefore, any equivalent changes or modifications made according to the structures, features, and principles described in the scope of the present invention patent application are included in the scope of the present invention patent application.

Claims

1. An oil-immersed transformer oil tank shielding structure with phase change auxiliary heat dissipation function, characterized in that: The shielding structure comprises a phase-change auxiliary heat dissipation shield (2) and a radiator (1), wherein the radiator (1) is arranged above the oil tank (3); the phase-change auxiliary heat dissipation shield (2) is mainly composed of a plurality of groups of hollow metal plates, each group of hollow metal plates comprises a plurality of hollow metal plates (6), and the internal cavities of the hollow metal plates (6) are filled with phase-change coolant; the hollow metal plates (6) are connected to the oil tank (3); the top end of the hollow metal plates (6) extends to the outside of the transformer oil tank (3) and is connected to the radiator (1).

2. The oil-immersed transformer oil tank shielding structure with phase change auxiliary heat dissipation function according to claim 1 is characterized in that: At least one group of hollow metal plates is arranged on each inner side wall of the oil tank (3); for each inner side wall of the oil tank (3), the number of groups of hollow metal plates is the same as the number and arrangement position distribution of the projections of the winding (4).

3. The oil-immersed transformer oil tank shielding structure with phase change auxiliary heat dissipation function according to claim 2 is characterized in that: The width of the hollow metal plate (6) is greater than the width of the corresponding winding (4); the bottom end height of the hollow metal plate (6) is lower than the bottom end height of the iron core (5) inside the corresponding winding (4).

4. The oil-immersed transformer oil tank shielding structure with phase change auxiliary heat dissipation function according to claim 2 is characterized in that: In each group of hollow metal plates, the hollow metal plates (6) are arranged evenly; in each group of hollow metal plates, the intervals between adjacent hollow metal plates (6) remain consistent.

5. The oil-immersed transformer oil tank shielding structure with phase change auxiliary heat dissipation function according to claim 1 is characterized in that: The radiator (1) is an aluminum alloy fin radiator.

6. A structural optimization method for the oil tank shielding structure of an oil-immersed transformer according to any one of claims 1 to 5, characterized in that: The structure optimization method comprises the following steps: S1) taking the shielding spacing, shielding distance and shielding length of the oil tank shielding structure of the oil-immersed transformer as structural parameters to be optimized, and selecting a plurality of different horizontal parameters within the preset value range of each structural parameter to be optimized; S2) generating an orthogonal test table consisting of a plurality of combinations of structural parameters to be optimized using the Taguchi method according to the structural parameters to be optimized and the level parameters obtained in step S1; S3) for each combination of structural parameters to be optimized in the orthogonal test table, the corresponding leakage magnetic flux density and winding temperature rise are obtained through simulation; the leakage magnetic flux density and winding temperature rise corresponding to all the combinations of structural parameters to be optimized are combined to obtain original data; S4) performing mean analysis and mean square error analysis on the raw data obtained in step S3 to obtain the leakage flux density mean, leakage flux density mean square error, winding temperature rise mean and winding temperature rise mean square error corresponding to each structural parameter to be optimized; S5) Using the Taguchi method, according to the mean value of leakage magnetic flux density, the mean square error of leakage magnetic flux density, the mean value of winding temperature rise and the mean square error of winding temperature rise corresponding to each structural parameter to be optimized, the optimal level parameter of each structural parameter to be optimized is obtained and used as the optimal structural parameter. All optimal structural parameters constitute the optimal structural parameter combination.

7. The structural optimization method according to claim 6, characterized in that: The shielding spacing has a value range of 10 to 40 mm; the shielding distance has a value range of 100 mm to 250 mm; and the shielding length has a value range of 3100 mm to 3400 mm.

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