Oil-immersed transformer based on evaporative cooling

Abstract

The application discloses an oil-immersed transformer based on evaporation cooling, which comprises an oil tank body, an opening is arranged at the top of the oil tank body, a tank cover is arranged at the opening of the oil tank body, an evaporation condensation cavity is connected with the tank cover, a plurality of oil liquid cavities are connected with the tank cover, the first end of each oil liquid cavity is a closed structure and is arranged in the oil tank body and is used for collecting the oil temperature of oil liquid at a preset position in the oil tank body, the second end of each oil liquid cavity is an open structure and is communicated with the evaporation condensation cavity to form a cooling liquid containing cavity, and cooling liquid is filled in the cooling liquid containing cavity, and the filling quality of the cooling liquid is related to the target overload current of the oil-immersed transformer, the target overload duration, the physical property parameters of the cooling liquid and the oil temperature rise limit value at the preset position in the oil tank body under the overload working condition. The application can ensure that the phase change heat absorption of the cooling liquid is sufficient to stably control the oil temperature of the oil liquid below the safety threshold value within the target overload duration, so that the high overload capacity is controllable and predictable.

Description

Technical Field

[0001] This invention belongs to the field of transformer technology, specifically relating to an oil-immersed transformer based on evaporative cooling. Background Technology

[0002] Oil-immersed transformers in power distribution networks often experience overload due to seasonal loads, sometimes reaching 2-3 times their rated load for short periods. Therefore, developing oil-immersed distribution transformers with high overload capacity is particularly important. Conventional 10kV oil-immersed transformers mostly use natural convection or forced oil circulation for cooling. Under short-term overload conditions (such as 1.5-2 times the rated load), the winding temperature rises sharply, easily triggering temperature protection or accelerating insulation aging, thus limiting overload capacity. Existing cooling technologies used in oil-immersed transformers to achieve high overload capacity and their drawbacks include:

[0003] 1. Adding heat sinks or fans: This results in larger size, higher noise, increased energy consumption, and slower response to transient thermal shocks.

[0004] 2. Forced oil circulation system: It has a complex structure, high maintenance costs, and the risk of leakage. It also relies on external power, which reduces its reliability.

[0005] 3. Traditional heat dissipation methods all rely on sensible heat exchange, depend on the temperature rise of the medium, have limited heat capacity, and are insufficient in their ability to "shaving off" peak heat loads.

[0006] Existing technologies have explored the application of phase change cooling in electrical equipment, but these often focus on the presence or absence of the system and basic circulation. The determination of the cooling medium dosage is frequently based on experience or rough estimation, lacking a direct, quantitative correlation with the transformer's specific overload capacity and temperature rise control targets. This leads to uncertain cooling effects, potentially resulting in over-protection (excessive dosage, high cost, and large size) or under-protection (insufficient dosage, unable to effectively suppress temperature rise). How to achieve a simple, reliable, and low-cost deep integration of efficient phase change cooling technology with standard oil-immersed transformers, and realize a "quantitatively designable and predictable" intelligent thermal management system, remains a technical challenge. Summary of the Invention

[0007] To address the aforementioned issues, this invention proposes an oil-immersed transformer based on evaporative cooling, which ensures that the phase change heat absorption of the coolant is sufficient to stably control the oil temperature below a safe threshold during the target overload duration, thereby achieving controllable and predictable high overload capacity.

[0008] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution:

[0009] An oil-immersed transformer based on evaporative cooling, comprising:

[0010] The fuel tank body has an opening at the top;

[0011] The tank cover is installed at the opening of the fuel tank body;

[0012] The evaporation and condensation chamber is connected to the box cover;

[0013] Several oil chambers are provided, each connected to the tank cover; the first end of each oil chamber is a closed structure located inside the oil tank, used to collect the oil temperature at a preset position in the oil tank; the second end of each oil chamber is an open structure, connected to the evaporation and condensation chamber, forming a coolant receiving chamber.

[0014] The coolant is injected into the coolant reservoir, and the injection quality is related to the target overload current of the oil-immersed transformer, the target overload duration, the physical properties of the coolant, and the oil temperature rise limit at a preset position in the tank under overload conditions.

[0015] Optionally, the oil temperature at a preset position in the oil tank is the same as the oil temperature at the top of the oil tank.

[0016] Optionally, the formula for calculating the injected coolant mass is:

[0017] ,

[0018] In the formula, For the quality of coolant injection, For safety reasons, Minimum injection mass of coolant;

[0019] Among them, the minimum injection mass of coolant The calculation formula is:

[0020] ,

[0021] ,

[0022] ,

[0023] ;

[0024] In the formula, The latent heat of vaporization of the coolant. The specific heat capacity of the coolant. This is the limit value for oil temperature rise. The sensible heat required to rise from the initial ambient temperature to the boiling point of the coolant. The heat that needs to be absorbed by the phase change of the coolant, This refers to the total additional heat generated during the overload period. To account for the heat that can be dissipated through natural convection and radiation during the target overload duration. This represents the total loss of the transformer under overload conditions. This represents the total losses during normal transformer operation. The ratio of the target overload current to the rated current. The duration of the target overload.

[0025] Optionally, the volume of the evaporative condensation chamber is variable to accommodate the amount of coolant injected under different overload levels, wherein the overload level is determined by the target overload current and the target overload duration.

[0026] Optionally, the evaporation-condensation chamber is provided with multiple calibrated injection scales to indicate the amount of coolant injected under different overload levels, wherein the overload level is determined by the target overload current and the target overload duration.

[0027] Optionally, the evaporation-condensation chamber has a coolant inlet.

[0028] Optionally, the walls of the evaporation-condensation chamber are designed with ribs or a corrugated structure.

[0029] Optionally, the oil-immersed transformer further includes low-voltage bushings and high-voltage bushings, which are symmetrically arranged on the tank wall of the oil tank.

[0030] Optionally, each oil chamber is uniformly connected to the tank cover in an array.

[0031] Optionally, the evaporation and condensation chamber is sealed to the box cover via a flange and a seal.

[0032] Optionally, the ratio of the liquid volume of the coolant in the coolant reservoir to the volume of the coolant reservoir is within a set threshold range to accommodate the steam generated by vaporization.

[0033] Optionally, the coolant is a low-boiling-point coolant with a boiling point of 55°C to 85°C, and the boiling point is near the oil temperature rise limit of the oil-immersed transformer.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] This invention establishes a dual cooling cycle of "oil-liquid phase change coupling". Through precise design of the coolant quantity (i.e., injection mass) in the early stage, it achieves passive and precise limiting of oil temperature during operation. Specifically: when the transformer is under load, heat is transferred to the oil chamber through the transformer oil, which causes the coolant to vaporize. When the transformer is under short-term high overload, the oil temperature at a predetermined position in the tank (preferably the top of the tank) exceeds the boiling point of the coolant, triggering a violent phase change in the coolant. During this process, since the injection mass of the coolant is pre-matched according to the target overload condition (i.e., target overload current and target overload duration) and the allowable temperature rise (i.e., oil temperature rise limit), the heat absorbed by the phase change of the coolant during the entire overload period is sufficient to stably control the oil temperature below the safety threshold. This process achieves "adaptive matching of hydraulic oil heat and coolant evaporation" and "hard temperature limiting" protection, which can be achieved solely through physical design without the need for external sensors and controllers. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein:

[0037] Figure 1 This is one of the structural schematic diagrams of an oil-immersed transformer based on evaporative cooling according to an embodiment of the present invention;

[0038] Figure 2 This is a second schematic diagram of the structure of an oil-immersed transformer based on evaporative cooling according to an embodiment of the present invention;

[0039] Figure 3 This is a schematic diagram of the radial cross-section of an evaporation and condensation cavity according to an embodiment of the present invention;

[0040] In the picture:

[0041] 1-Tank body, 2-Tank cover, 3-Flange, 4-Seal, 5-Evaporator-condenser chamber, 6-Coolant, 7-Coolant inlet, 8-Oil chamber, 9-Oil, 10-Low-pressure bushing, 11-High-pressure bushing. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may include different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0044] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0045] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0046] The application principle of the present invention will be described in detail below with reference to the accompanying drawings.

[0047] This invention provides an oil-immersed transformer based on evaporative cooling, such as... Figures 1-3 As shown, it includes:

[0048] The tank body 1 has an opening at the top and is filled with oil 9 (i.e., transformer oil).

[0049] The tank cover 2 is installed at the opening of the tank body 1;

[0050] The evaporation and condensation chamber 5 is connected to the box cover 2;

[0051] Several oil chambers 8 are provided, each of which is connected to the tank cover 2. The first end of each oil chamber 8 is a closed structure located inside the oil tank body 1, used to collect the oil temperature of the oil 9 at a preset position in the oil tank body 1. The second end of each oil chamber 8 is an open structure, connected to the evaporation and condensation chamber 5, forming a coolant receiving chamber.

[0052] Coolant 6 is injected into the coolant reservoir. The injection quality is determined by the target overload current of the oil-immersed transformer, the target overload duration, and the oil temperature rise limit at a preset location in the tank 1 under overload conditions. The oil temperature rise limit is determined by the oil insulation class, such as 65K for Class A and 100K for Class F.

[0053] The above scheme establishes a dual cooling cycle of "oil-liquid phase change coupling". Through precise design of the amount of coolant 6 (i.e., the injection mass) in the early stage, passive and precise limiting of oil temperature during operation is achieved. Specifically: when the transformer is under load, heat is transferred to the oil chamber 8 through the transformer oil 9, which causes the coolant 6 to be vaporized; when the transformer is under short-term high overload, the oil temperature of the oil 9 at a predetermined position in the oil tank 1 (preferably at the top of the oil tank 1) exceeds the set boiling point of the coolant 6, triggering the cooling... The coolant 6 undergoes a dramatic phase change. During this process, because the injection quality of coolant 6 is pre-matched based on the target overload condition (i.e., target overload current and target overload duration) and the allowable temperature rise (i.e., oil temperature rise limit), the heat absorbed by the phase change of coolant 6 is sufficient to stably control the oil temperature of oil 9 below the safety threshold throughout the overload period. This process achieves "adaptive matching of heat of transformer oil 9 and evaporation of coolant 6" and "hard temperature limiting" protection, which can be achieved solely through physical design without the need for external sensors and controllers. In specific implementation, when injecting coolant 6, it is necessary to ensure that coolant 6 is evenly distributed in the evaporation and condensation chamber 5, and to inject it after evacuation to remove air. The oil chamber 8 is preferably a thin-walled stainless steel tube with an inner diameter of 8-15mm and a wall thickness of 0.5-1.0mm, which facilitates timely heat transfer and improves heat transfer accuracy. The entire cooling process is completed by natural circulation driven by gravity, density difference, and phase change, without any moving parts or external power, achieving the highest reliability.

[0054] In one specific embodiment of the present invention, the oil temperature of the oil 9 at a preset position in the oil tank body 1 refers to the oil temperature of the oil 9 at the top position in the oil tank body 1.

[0055] In the above scheme, since the oil temperature of the oil 9 at the top of the tank 1 is the highest, by transferring the oil temperature at the top of the tank to the coolant 6, the peak oil temperature at the top of the tank during overload can be predicted and strictly limited to the design value (such as 105℃), with a small fluctuation range. This is significantly better than traditional forced-cooling transformers that rely on discrete control methods such as intermittent start-stop of the fan, and greatly improves the operational certainty and lifespan predictability of the transformer under extreme loads.

[0056] In a specific embodiment of the present invention, the formula for calculating the injection mass of coolant 6 is as follows:

[0057] ,

[0058] In the formula, The injection quality of coolant 6, For safety factor, the safety factor Used to ensure reliability; The minimum injection mass of coolant 6;

[0059] Among them, the minimum injection mass of coolant 6 The calculation formula is:

[0060] ,

[0061] ,

[0062] ,

[0063] ,

[0064] In the formula, The latent heat of vaporization of coolant 6 The specific heat capacity of the coolant is 6. This is the limit value for oil temperature rise. The sensible heat required to raise the temperature from the initial ambient temperature to the boiling point of the coolant (6 boiling points), The heat that needs to be absorbed by the six-phase change of the coolant, This refers to the total additional heat generated during the overload period. To account for the heat that can be dissipated through natural convection and radiation during the target overload duration. This represents the total loss of the transformer under overload conditions. This represents the total losses during normal transformer operation. The ratio of the target overload current to the rated current is N. In the specific implementation process, N can be set according to actual needs, such as 1.5 or 2. The duration of the target overload.

[0065] In the above scheme, when the transformer is under load, heat is transferred to the oil chamber 8 through the transformer oil 9, which causes the coolant 6 to vaporize. When the transformer is under short-term high overload, the oil temperature at a predetermined location (preferably the top) of the tank body 1 exceeds the set boiling point of the coolant 6, triggering a violent phase change in the coolant 6. During this process, since the injection quality of the coolant 6 is pre-matched according to the target overload condition (i.e., target overload current, target overload duration) and the allowable temperature rise (i.e., oil temperature rise limit), the heat that needs to be absorbed by the phase change of the coolant 6 during the entire overload period is... This will be sufficient to offset the total additional heat generated during overload. This process dynamically and automatically limits the actual rise in oil temperature (Δθ_actual) within a preset safety window (Δθ_max) until the overload ends or the coolant is nearly depleted. This achieves "heat flow adaptive matching" and "temperature hard limiting" protection through physical design alone, without the need for external sensors and controllers.

[0066] In one specific embodiment of the present invention, the volume of the evaporative condensation chamber 5 is variable to accommodate the injection volume of coolant 6 under different overload levels, wherein the overload level is determined by the target overload current and the target overload duration.

[0067] In the above scheme, by setting the volume of the evaporative condensation chamber 5 to be variable, the injection volume of coolant 6 can be adapted to different overload levels, thereby achieving precise cooling and facilitating production, inspection, and on-site maintenance adjustments.

[0068] In one specific embodiment of the present invention, the evaporation-condensation chamber 5 is provided with multiple calibrated injection scales to indicate the injection volume of coolant 6 under different overload levels, wherein the overload level is determined by the target overload current and the target overload duration.

[0069] In the above scheme, multiple calibrated injection scales are provided on the evaporative condensation chamber 5 to accommodate the injection volume of coolant 6 under different overload levels, achieving precise cooling. In practical implementation, a transparent window or permanent scale can be installed on the side of the evaporative condensation chamber 5 to mark the "calibrated injection scale (i.e., recommended liquid level line)" corresponding to different standard overload levels (e.g., 1.5 times / 1 hour, 2.0 times / 0.5 hour), facilitating production, inspection, and on-site maintenance adjustments.

[0070] In one specific embodiment of the present invention, the evaporation and condensation chamber 5 is provided with a coolant injection port 7.

[0071] Based on the above scheme, it is preferable to use a quantitative injection device during injection, and ensure that after injection, a vacuum is drawn or an inert gas (such as nitrogen) is filled in to remove air and moisture, maintain the internal inert environment, and ensure long-term stability of insulation and heat exchange performance.

[0072] In one specific embodiment of the present invention, the wall of the evaporation and condensation cavity 5 is designed with ribs or a corrugated structure.

[0073] In the above scheme, by setting fins or corrugated structures, the heat dissipation area can be increased, air-side heat exchange can be enhanced, and heat dissipation efficiency can be improved. In specific implementation, the evaporation-condensation chamber 5 can be made of carbon steel.

[0074] In one specific embodiment of the present invention, the oil-immersed transformer further includes a low-voltage bushing 10 and a high-voltage bushing 11, which are symmetrically arranged on the tank wall of the oil tank body 1.

[0075] In the above scheme, by symmetrically arranging the low-pressure bushing 10 and the high-pressure bushing 11 on the tank wall of the tank body 1, a structural basis is provided for arranging the evaporation and condensation chamber 5 at the upper end of the tank cover 2, and it helps to balance the internal heat generation of the tank body 1, avoid local overheating, and make the top oil temperature more representative of the overall thermal state, thereby making the cooling response more accurate and effective.

[0076] In one specific embodiment of the present invention, each oil cavity 8 is uniformly connected to the cover 2 in an array.

[0077] In the specific implementation process, each oil chamber 8 serves as the core "liquid-oil heat exchanger". It is uniformly welded to the bottom of the tank cover 2 in an array. The welding must ensure airtightness, and the distribution area of ​​the oil chamber 8 should cover the hot spot area at the top of the oil tank to ensure that the heat of the high-temperature oil at the top of the oil-immersed transformer can be quickly and evenly transferred to the coolant 6.

[0078] In one specific embodiment of the present invention, the evaporation and condensation chamber 5 is sealed to the box cover 2 via a flange 3 and a sealing element 4.

[0079] In the above scheme, the evaporation and condensation chamber 5 can be detachably and sealed to the cover 2 via flange 3 and sealing element 4, thereby improving the sealing performance of the entire device. In specific implementation, the sealing element 4 can be a rubber sealing ring or other device capable of achieving a sealing function.

[0080] In one specific embodiment of the present invention, the ratio of the liquid volume of the coolant 6 in the coolant reservoir to the volume of the coolant reservoir is within a set threshold range, so as to accommodate the steam generated due to vaporization.

[0081] In the above scheme, the set threshold is preferably set to 30%-35% to leave enough gas phase space to accommodate steam.

[0082] In one specific embodiment of the present invention, the coolant 6 is a low-boiling-point coolant 6 with a boiling point of 55°C to 85°C, and the boiling point is near the oil temperature rise limit of the oil-immersed transformer.

[0083] In the above scheme, the coolant 6 is preferably a fluorocarbon compound or a perfluorocarbon compound. These coolants 6 have a low boiling point and high thermal conductivity, which can effectively absorb and remove the heat generated inside the transformer. Its phase change temperature matches the upper limit of the transformer's allowable continuous operating oil temperature. This design allows the cooling system to be in a "standby" auxiliary state during normal operation and to be "activated" only when there is an overload temperature rise.

[0084] The cooling method for the oil-immersed transformer in this invention includes:

[0085] Heat transfer: The heat generated by the transformer load is first absorbed by the oil 9 through convection, and the high-temperature oil rises to the top of the oil tank.

[0086] Phase change triggering and heat absorption: High-temperature oil transfers heat to the coolant 6 in the evaporation and condensation chamber 5 through the oil chamber 8. When the oil temperature reaches the boiling point of the coolant 6, the coolant 6 vaporizes, absorbing a large amount of latent heat of vaporization, thereby strongly suppressing the rise in oil temperature.

[0087] Condensation and reflux: The generated coolant vapor rises to the lower temperature area at the top of the evaporation-condensation chamber 5, where it condenses into liquid after natural convection heat exchange with the air, releasing heat. The condensate then flows back to the bottom along the chamber wall under gravity, completing a closed phase change cycle.

[0088] Adaptive regulation: The cooling power of the entire system changes automatically and non-linearly with the internal temperature (oil temperature) of the transformer. The higher the temperature, the faster the vaporization rate of the coolant and the greater the heat dissipation, forming an inherent, adaptive negative feedback thermal regulation mechanism.

[0089] Based on the above analysis, this invention proposes a dual heat dissipation architecture of "oil-liquid phase change coupling". By combining the stability of traditional oil cooling with the extremely high transient heat dissipation capability of phase change cooling, a heat dissipation effect of "1+1>2" is achieved, which is an innovation in heat dissipation concept.

[0090] This invention achieves intelligent cooling with "self-triggered temperature threshold and self-adjusting cooling power". By precisely matching the boiling point of coolant 6 with the transformer's safe oil temperature threshold, the system only exerts maximum efficiency when needed (overload), avoiding the always-present additional losses or noise caused by conventional enhanced heat dissipation solutions.

[0091] This invention features a highly integrated and simplified structure. It simplifies the complex phase change system into a single evaporation and condensation chamber mounted on the tank cover 2, greatly improving engineering feasibility, reliability, and economy, and facilitating upgrades and modifications to existing transformer product lines.

[0092] This invention proposes a quantitative design method for the amount of coolant 6 used in transformer overload conditions, achieving "on-demand cooling" and "precise thermal protection." This invention abandons traditional trial-and-error or empirical methods, and for the first time establishes a minimum mass of coolant 6 (…). This invention provides an engineering calculation model relating the coolant 6 to the transformer's key operating parameters (target overload current, target overload duration, and oil temperature rise limit). This model allows for the "tailor-made" optimal coolant 6 filling quantity for transformers designed for specific application scenarios (such as seasonal peak loads or short-term emergency power supply) during the design phase. This makes the cooling system of this invention (evaporation-condensation chamber + oil chamber + coolant) not only a functional component but also a "thermal energy buffer" with calculable and verifiable protection characteristics, ensuring the controllability and reliability of high overload capacity enhancement.

[0093] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only used to facilitate the description of the present invention and to simplify the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of the present invention.

[0094] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. An oil-immersed transformer based on evaporative cooling, characterized in that, include: The fuel tank body has an opening at the top; The tank cover is installed at the opening of the fuel tank body; The evaporation and condensation chamber is connected to the box cover; Several oil chambers are provided, each connected to the tank cover; the first end of each oil chamber is a closed structure located inside the oil tank, used to collect the oil temperature at a preset position in the oil tank; the second end of each oil chamber is an open structure, connected to the evaporation and condensation chamber, forming a coolant receiving chamber. The coolant is injected into the coolant reservoir, and the injection quality is related to the target overload current of the oil-immersed transformer, the target overload duration, the physical properties of the coolant, and the oil temperature rise limit at a preset position in the tank under overload conditions. The formula for calculating the injection mass of coolant is: ， In the formula, For the quality of coolant injection, For safety reasons, Minimum injection mass of coolant; Among them, the minimum injection mass of coolant The calculation formula is: ， ， ， ； In the formula, The latent heat of vaporization of the coolant. The specific heat capacity of the coolant. This is the limit value for oil temperature rise. The sensible heat required to rise from the initial ambient temperature to the boiling point of the coolant. The heat that needs to be absorbed by the phase change of the coolant, This refers to the total additional heat generated during the overload period. To account for the heat that can be dissipated through natural convection and radiation during the target overload duration. This represents the total loss of the transformer under overload conditions. This represents the total losses during normal transformer operation. The ratio of the target overload current to the rated current. The duration of the target overload.

2. The oil-immersed transformer based on evaporative cooling according to claim 1, characterized in that: The oil temperature at a preset position in the oil tank is the same as the oil temperature at the top of the oil tank.

3. The oil-immersed transformer based on evaporative cooling according to claim 1, characterized in that: The volume of the evaporative condensation chamber is variable to accommodate the amount of coolant injected under different overload levels, which are determined by the target overload current and the target overload duration.

4. An oil-immersed transformer based on evaporative cooling according to claim 1, characterized in that: The evaporation and condensation chamber is equipped with multiple calibrated injection scales to indicate the amount of coolant injected under different overload levels. The overload level is determined by the target overload current and the target overload duration.

5. An oil-immersed transformer based on evaporative cooling according to claim 1, characterized in that: The evaporation and condensation chamber has a coolant inlet.

6. An oil-immersed transformer based on evaporative cooling according to claim 1, characterized in that: The walls of the evaporation and condensation chamber are designed with ribs or a corrugated structure.

7. An oil-immersed transformer based on evaporative cooling according to claim 1, characterized in that: The oil-immersed transformer also includes low-voltage bushings and high-voltage bushings, which are symmetrically arranged on the tank wall of the oil tank.

8. An oil-immersed transformer based on evaporative cooling according to claim 1, characterized in that: Each oil chamber is evenly connected to the tank cover in an array.

9. An oil-immersed transformer based on evaporative cooling according to claim 1, characterized in that: The evaporation and condensation chamber is sealed to the box cover via a flange and a sealing element.

10. An oil-immersed transformer based on evaporative cooling according to claim 1, characterized in that: The ratio of the liquid volume of the coolant in the coolant reservoir to the volume of the coolant reservoir is within a set threshold range to accommodate the steam generated by vaporization.

11. An oil-immersed transformer based on evaporative cooling according to claim 1, characterized in that: The coolant is a low-boiling-point coolant with a boiling point of 55°C to 85°C.

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