Large oil-immersed transformer waste heat utilization system

Abstract

The utility model belongs to the field of waste heat utilization, and relates to a large oil-immersed transformer waste heat utilization system which comprises an air cooling / self-cooling cooling device, a control cabinet and a waste heat utilization device, and the air cooling / self-cooling cooling device comprises an upper cooling mother pipe, an upper cooling branch mother pipe, a lower cooling mother pipe and a lower cooling branch mother pipe. The upper cooling branch mother pipe and the lower cooling branch mother pipe are of L-shaped bent structures, and the two ends of the upper cooling mother pipe and the two ends of the lower cooling mother pipe are of closed structures. The waste heat utilization device comprises a heat exchange device and a waste heat absorption device, one side of the heat exchange device is communicated with the upper cooling branch mother pipe through a heat exchange connecting pipeline, and the other side of the heat exchange device is communicated with the waste heat absorption device through a heat exchange connecting pipeline; a frequency conversion oil pump is installed on the lower cooling branch mother pipe or the upper cooling branch mother pipe, and a frequency converter of the frequency conversion oil pump is installed in a control cabinet. According to the utility model, the air cooling / self-cooling device and the waste heat utilization device operate cooperatively, so that a large amount of energy is saved, and air thermal pollution is avoided.

Description

Technical Field

[0001] The utility model belongs to the technical field of waste heat utilization, and in particular relates to a large oil-immersed transformer waste heat utilization system based on a cooling mother pipe cooling structure. Background Art

[0002] Currently, global energy development faces three major challenges: resource scarcity, environmental pollution, and climate change. The vast majority of energy lost in power transmission is dissipated as heat. Transformers, as crucial heat-generating components in power grid operations, experience significant losses in their cores, windings, and steel structures due to resistance and magnetic reluctance.

[0003] Large oil-immersed transformers typically use natural or air cooling to cool the transformer oil. Heat energy is dissipated into the surrounding air through the oil's circulating cooling process. This not only wastes a significant amount of energy but also contributes to air thermal pollution. Although the energy conversion efficiency of large and medium-sized transformers has now reached over 99.5%, the energy lost through losses is still considerable. In fact, three or four voltage transformations are typically required from power generation to power supply and consumption, resulting in significantly greater losses. The larger the transformer capacity, the greater the heat loss. Summary of the Invention

[0004] In order to solve the above technical problems, the purpose of this utility model is to provide a large oil-immersed transformer waste heat utilization system based on a cooling main pipe cooling structure. The technical solutions adopted by this utility model are as follows:

[0005] A waste heat utilization system for a large oil-immersed transformer, wherein the large oil-immersed transformer adopts a cooling mother pipe cooling structure, including an air-cooled / self-cooled cooling device, a control cabinet and a waste heat utilization device symmetrically installed on both sides of the oil tank of the large oil-immersed transformer, wherein the air-cooled / self-cooled cooling device includes a plurality of fins, wherein the upper part of the fins is connected to the side wall of the upper cooling mother pipe through an upper connecting pipe, and the upper cooling mother pipe is connected to the top of the oil tank of the large oil-immersed transformer through a plurality of upper cooling branch mother pipes, and the lower part of the fins is connected to the side wall of the lower cooling mother pipe through a lower connecting pipe, and the lower cooling mother pipe is connected to the lower part of the oil tank side of the large oil-immersed transformer through a plurality of lower cooling branch mother pipes, and the upper cooling branch mother pipe and the lower cooling branch mother pipe are connected. The cooling branch mother pipe is an L-shaped bending structure, and both ends of the upper cooling mother pipe and the lower cooling mother pipe are closed structures; the waste heat utilization device includes a heat exchange device and a waste heat absorption device, one side of the heat exchange device is connected to the upper cooling branch mother pipe through a heat exchange connecting pipe 1, and the other side of the heat exchange device is connected to the waste heat absorption device through a heat exchange connecting pipe 2; a variable frequency oil pump is installed on the lower cooling branch mother pipe or the upper cooling branch mother pipe, and the frequency converter of the variable frequency oil pump is installed in the control cabinet; temperature sensors and flow sensors are installed in all pipelines, and an oil level temperature sensor is installed in the oil tank of the large oil-immersed transformer. All sensors are electrically connected to the CPU or industrial control machine in the control cabinet through data cables.

[0006] Preferably, the heat exchange device includes an oil-water heat exchanger, and the heat exchange connecting pipeline includes an upper waste heat recovery branch pipe, an upper waste heat recovery main pipe, a lower waste heat recovery main pipe and a total waste heat recovery main pipe with a bent structure. The upper cooling branch main pipe includes an upper cooling longitudinal branch main pipe and an upper cooling transverse branch main pipe. An electric three-way valve is installed between the upper cooling longitudinal branch main pipe and the upper cooling transverse branch main pipe. The lower end of the upper cooling longitudinal branch main pipe is connected to the top of the oil tank of the large oil-immersed transformer, and the upper end of the upper cooling longitudinal branch main pipe is connected to the outlet of the electric three-way valve. The second outlet of the electric three-way valve is connected with the end of the upper cooling horizontal branch mother pipe, the third outlet of the electric three-way valve is connected with one end of the upper waste heat recovery branch pipe, the other end of the upper waste heat recovery branch pipe is connected with the side wall of the upper waste heat recovery mother pipe, one end of the upper waste heat recovery mother pipe is a closed structure, the other ends of the two upper waste heat recovery mother pipes are connected to one end of the total waste heat recovery mother pipe through a three-way pipe joint, the other end of the total waste heat recovery mother pipe is connected to the oil-water heat exchanger, one end of the lower waste heat recovery mother pipe is connected to the oil-water heat exchanger, and the other end of the lower waste heat recovery mother pipe is connected to the lower part of the side wall of the oil tank of the large oil-immersed transformer.

[0007] Preferably, the oil-water heat exchanger includes: an oil-side oil pump of the oil-water heat exchanger and an oil-side oil pump of the oil-water heat exchanger, the oil-side oil pump of the oil-water heat exchanger and the oil-side oil pump of the oil-water heat exchanger are variable frequency oil pumps, and the frequency converters corresponding to the oil-side oil pump of the oil-water heat exchanger and the water-side oil pump of the oil-water heat exchanger are installed in the control cabinet.

[0008] Preferably, the waste heat disposal device includes a waste heat disposal pipeline, a heat pump and a terminal heat equipment. The water side of the oil-water heat exchanger is connected to one side of the heat pump, and the other side of the heat pump is connected to the terminal heat equipment through the waste heat disposal pipeline. The heat pump is equipped with a variable frequency oil pump on the terminal heat equipment side, and the frequency converter of the variable frequency oil pump on the terminal heat equipment side is installed in the control cabinet.

[0009] Preferably, the waste heat disposal device includes a thermoelectric generator.

[0010] Preferably, the heat exchange device includes an oil-oil heat exchanger, or other sealed heat exchange devices.

[0011] Beneficial effects of the utility model:

[0012] The utility model transforms a large oil-immersed transformer based on a cooling mother tube cooling structure, and adds a waste heat utilization device on the basis of the original air-cooling / self-cooling cooling device, so that the air-cooling / self-cooling cooling device and the waste heat utilization device operate in coordination, extracting heat from the transformer oil and then transferring the waste heat to the waste heat absorption device for waste heat utilization, thereby saving a large amount of energy and avoiding air thermal pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without inventive work.

[0014] Figure 1 This is the left view of a large oil-immersed transformer based on the cooling main tube cooling structure;

[0015] Figure 2 This is an outline view of a large oil-immersed transformer based on a cooling main tube cooling structure;

[0016] Figure 3 This is a left side view of the waste heat utilization system according to the first embodiment of the present invention;

[0017] Figure 4 is a top view of the waste heat utilization system according to the first embodiment of the present invention;

[0018] Figure 5 This is a partial enlarged view of the oil-water heat exchanger of the first embodiment of the present invention;

[0019] Figure 6 1 is a schematic structural diagram of the electric three-way valve in the first embodiment of the present invention;

[0020] In the figure, 1 is a large oil-immersed transformer, 2 is an air-cooled / self-cooled cooling device, 3 is a waste heat utilization device, 21 is an upper cooling main pipe, 22 is an upper cooling branch main pipe, 221 is an upper cooling longitudinal branch main pipe, 222 is an upper cooling transverse branch main pipe, 23 is a fan, 24 is a fan, 25 is a lower cooling main pipe, 26 is a lower cooling branch main pipe, 27 is a variable frequency oil pump, 31 is an electric three-way valve, 311 is an electric three-way valve outlet 1, 312 is the second outlet of the electric three-way valve, 313 is the third outlet of the electric three-way valve, 32 is the upper waste heat recovery branch pipe, 33 is the upper waste heat recovery main pipe, 34 is the total waste heat recovery main pipe, 35 is the oil-water heat exchanger, 351 is the oil side oil pump of the oil-water heat exchanger, 352 is the water side oil pump of the oil-water heat exchanger, 36 is the lower waste heat recovery main pipe, 37 is the waste heat absorption device, 38 is the heat pump, 39 is the terminal heat-using equipment, and 40 is the control cabinet. DETAILED DESCRIPTION

[0021] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0022] like Figure 1 、 2As shown, a large oil-immersed transformer waste heat utilization system is shown. The large oil-immersed transformer 1 is based on a cooling main pipe cooling structure. Air-cooling / self-cooling cooling devices 2 are symmetrically installed on both sides of the oil tank of the large oil-immersed transformer 1. The air-cooling / self-cooling cooling devices 2 include several fins 23. The upper portion of each fin 23 is connected to the side wall of an upper cooling main pipe 21 via an upper connecting pipe. The upper cooling main pipe 21 is connected to the top of the oil tank of the large oil-immersed transformer 1 via several upper cooling branch main pipes 22. The lower portion of each fin 23 is connected to the side wall of a lower cooling main pipe 25 via a lower connecting pipe. The lower cooling main pipe 25 is connected to the side of the oil tank of the large oil-immersed transformer 1 via several lower cooling branch main pipes 26. The air-cooling cooling device is provided with a fan 24, which is fixedly mounted on the bottom or side of the fin 23. The self-cooling cooling device does not have a fan. The hot oil in the upper portion of the oil tank of the large oil-immersed transformer 1 flows through the upper cooling branch mother pipe 22 into the upper cooling mother pipe 21. The hot oil then disperses from the upper cooling mother pipe 21 to the fins 23. A fan 24 is used to accelerate air circulation in the fins 23, improving heat dissipation efficiency. After cooling in the fins 23, the hot oil flows through the lower cooling mother pipe 25 and the lower cooling branch mother pipe 26, and finally flows back into the oil tank of the large oil-immersed transformer 1, forming a complete transformer cooling system. The upper cooling branch mother pipe 22 and the lower cooling branch mother pipe 26 have an L-shaped bent structure, while the upper cooling mother pipe 21 and the lower cooling mother pipe 25 have closed ends.

[0023] In the embodiment of the present utility model, a large oil-immersed transformer waste heat utilization system is designed based on the large oil-immersed transformer 1 with a cooling main pipe cooling structure of the above structure or a similar structure. Example 1

[0024] In the first embodiment of the present invention, the existing cooling system of the large oil-immersed transformer 1 based on the cooling main pipe cooling structure is technically modified, and a waste heat utilization device 3 is added, which enables the air-cooling / self-cooling cooling device 2 and the waste heat utilization device 3 to operate in coordination.

[0025] like Figure 3-6 As shown, first, a variable frequency oil pump 27 is installed on the lower cooling branch main pipe 26 of the air-cooled / self-cooled cooling device 2. In this first embodiment, the variable frequency oil pump 27 is installed on the lower cooling branch main pipe 26. Of course, the variable frequency oil pump 27 can also be installed on the upper cooling branch main pipe 22 as needed. The inverter of the variable frequency oil pump 27 is installed in the control cabinet 40. The inverter controls the variable frequency oil pump 27, thereby controlling the oil flow of the air-cooled / self-cooled cooling device 2 and the waste heat utilization device 3.

[0026] The waste heat utilization device 3 includes a heat exchange device and a waste heat disposal device 37. The heat exchange device includes an oil-water heat exchanger 35 and a heat exchange connecting pipeline. The heat exchange connecting pipeline includes an upper waste heat recovery branch pipe 32 and an upper waste heat recovery main pipe 33. In order to facilitate the installation of the oil-water heat exchanger 35, the upper cooling branch main pipe 22 is cut off at the bend, so that the original upper cooling branch main pipe 22 is divided into two sections: an upper cooling longitudinal branch main pipe 221 and an upper cooling transverse branch main pipe 222. An electric three-way valve 31 is installed between the upper cooling longitudinal branch main pipe 221 and the upper cooling transverse branch main pipe 222. The electric three-way valve 31 includes an electric three-way valve outlet 2 312 and an electric three-way valve outlet 3 313 symmetrically at both ends, and an electric three-way valve outlet 1 311 located between the electric three-way valve outlet 2 312 and the electric three-way valve outlet 3 313. The lower end of the upper cooling longitudinal branch mother pipe 221 is connected to the top of the oil tank of the large oil-immersed transformer 1, the upper end of the upper cooling longitudinal branch mother pipe 221 is connected to the electric three-way valve outlet 1 311, the electric three-way valve outlet 2 312 is connected to the end of the upper cooling horizontal branch mother pipe 222, the electric three-way valve outlet 313 is connected to one end of the upper waste heat recovery branch pipe 32, the other end of the upper waste heat recovery branch pipe 32 is connected to the side wall of the upper waste heat recovery mother pipe 33, one end of the upper waste heat recovery mother pipe 33 is a closed structure, and the two ends are connected. The other end of the upper waste heat recovery main pipe 33 is connected to one end of the total waste heat recovery main pipe 34 through a tee pipe joint. The other end of the total waste heat recovery main pipe 34 is connected to the oil-water heat exchanger 35. The total waste heat recovery main pipe 34 is a bent structure. One end of the lower waste heat recovery main pipe 36 is connected to the oil-water heat exchanger 35. The other end of the lower waste heat recovery main pipe 36 is connected to the lower part of the oil tank side wall of the large oil-immersed transformer 1. After the hot oil is cooled in the oil-water heat exchanger 35, it flows back to the interior of the large oil-immersed transformer 1 through the lower waste heat recovery main pipe 36.

[0027] The oil-water heat exchanger 35 includes heat exchange connecting piping, an oil-side oil pump 351, and a water-side oil pump 352. These pumps are variable-frequency pumps, and their corresponding frequency converters are installed in the control cabinet 40. The oil-water heat exchanger 355 is a mature product, and the number and installation locations of the oil-side and water-side oil pumps 351, 352 can be flexibly adjusted as needed. The oil-water heat exchanger 355 is distinguished by its use of cooling water to cool the transformer oil, ensuring independent oil and water circulation, preventing mixing.

[0028] The waste heat disposal device 37 comprises waste heat disposal piping, a heat pump 38, and a terminal heat-using device 39. The oil side of the oil-water heat exchanger 35 is connected to the air-cooled / self-cooled cooling device 2, while the water side of the oil-water heat exchanger 35 is connected to one side of the heat pump 38. The other side of the heat pump 38 is connected to the terminal heat-using device 39. The heat pump 38 is equipped with a variable-frequency oil pump on the terminal heat-using device 39 side, and the inverter for the variable-frequency oil pump on the terminal heat-using device 39 side is installed in the control cabinet 40. The heat pump 38 is a highly efficient and energy-saving device that fully utilizes low-grade thermal energy. Heat can spontaneously transfer heat from a high-temperature object to a low-temperature object, but not spontaneously in the reverse direction. The operating principle of the heat pump 38 is that it mechanically forces heat from a low-temperature object to a high-temperature object in a reverse cycle. It consumes only a small amount of reverse cycle net work to generate a large amount of heat, effectively utilizing otherwise difficult-to-use low-grade thermal energy to achieve energy savings. The heat pump 38 can transfer heat energy from a low-level heat source to a high-level heat source for use in the heat-using terminal equipment 39, including but not limited to domestic hot water, winter heating, and greenhouses. For example, for heating, the heat pump 38 converts the low-level heat source into a high-level heat source. In this case, one side of the heat pump 38 is connected to the oil-water heat exchanger 35, and the other side is connected to the heating pipe. In this case, the heating pipe is the heat-using terminal equipment 39, and the two sides have relatively independent circulations. The heat pump 38 can absorb heat from the cooling water exiting the oil-water heat exchanger 35 to heat the circulating water in the heating pipe on the other side. For example, if the cooling water exiting the oil-water heat exchanger 35 is at 50°C, the heat absorbed by the heat pump 38, combined with the electrical energy consumed by the heat pump 38 itself, can be converted into heat for the circulating water on the other side. The temperature of the circulating water in the heating pipe can reach 80°C (the specific temperature depends on the type of heat pump 38, the needs of the heat-using terminal equipment 39, the water flow rate, etc.). The heat pump 38 can also utilize waste heat for cooling, replacing air conditioning for room cooling. This requires selecting the heat pump 38 and also has requirements for the temperature of the water output by the oil-water heat exchanger 35 .

[0029] Furthermore, temperature, flow and other sensors are set in all pipelines, and an oil level temperature sensor is set in the oil tank of the large oil-immersed transformer 1. The sensors are electrically connected to the control cabinet 40 through data cables. At the same time, transformer current signal lights and transformer voltage signal lights are set in the control cabinet 40 to analyze the transformer operation, heat dissipation, life, and waste heat disposal, as well as the coordinated operation of the air-cooled / self-cooled cooling device 2 and the waste heat utilization device 3.

[0030] The control cabinet 40 houses multiple frequency converters, each paired with a variable-frequency oil pump to control its flow rate. The oil-water heat exchanger 35 and the waste heat dissipation device 37 are connected by two water pipes, forming a circulation system. The cooling water in the oil-water heat exchanger 35 cools the transformer oil, dissipating the heat, raising its temperature to high-temperature cooling water. The high-temperature cooling water then enters the waste heat dissipation device 37, where it dissipates the excess heat, lowering its temperature to low-temperature cooling water. This low-temperature cooling water then flows back into the oil-water heat exchanger 35 to cool the transformer oil. After cooling, the transformer oil is re-introduced into the transformer tank. The amount of heat dissipated by the waste heat dissipation device 37 determines the amount of heat removed by the oil-water heat exchanger 35, and thus the amount of heat dissipated by the transformer via the oil-water heat exchanger 35. The entire system is flexibly controlled by the control cabinet 40, which is equipped with a CPU or industrial computer for automatic control. The control method is conventional.

[0031] At present, there is a technical gap in the utilization of transformer waste heat and the coordinated work of the existing transformer air cooling system. The utility model utilizes the waste heat of a large oil-immersed transformer. At the same time, the waste heat utilization and the original transformer air cooling system work together to ensure the maximum utilization of the waste heat while ensuring the normal heat dissipation of the transformer, thereby extending the service life of the transformer.

[0032] According to the analysis results of the CPU or industrial computer, the CPU or industrial computer controls the frequency converter and the electric three-way valve 31 to achieve the following functions:

[0033] 1. When the waste heat of the transformer can be completely absorbed by the waste heat absorption device 37, the air cooling / self-cooling cooling device 2 is completely cut off through the electric three-way valve 31 (the electric three-way valve outlet 2 312 is closed, and the electric three-way valve outlet 3 313 is opened), the variable frequency oil pump 27 stops working, and the waste heat of the transformer is completely absorbed by the waste heat utilization device 3.

[0034] 2. When the waste heat utilization device 3 fails or is under maintenance, the waste heat utilization device 3 can also be completely closed (the electric three-way valve outlet 2 312 is opened, and the electric three-way valve outlet 3 313 is closed), and the waste heat of the transformer is completely released by the air cooling / self-cooling cooling device 2, ensuring the normal operation of the transformer and the operational reliability of the transformer body.

[0035] 3. When the air-cooling / self-cooling cooling device 2 and the waste heat utilization device 3 need to work together, the electric three-way valve outlet 2 312 and the electric three-way valve outlet 3 313 are both opened, and the variable frequency oil pump 27 works. The channel size of the air-cooling / self-cooling cooling device 2 and the waste heat utilization device 3 can be adjusted by adjusting the opening angle of the electric three-way valve 31, and the frequency converter corresponding to the variable frequency oil pump 27 and the oil-water heat exchanger oil side oil pump 351 can be adjusted to adjust the pipeline flow, so as to achieve the purpose of reasonably dissipating the heat of the air-cooling / self-cooling cooling device 2 and the waste heat utilization device 3, ensuring the normal heat dissipation of the transformer and fully utilizing the waste heat of the transformer.

[0036] 4. By adjusting the inverter corresponding to the water-side oil pump 352 of the oil-water heat exchanger and the parameters of the heat pump 38, the outlet water temperature and flow rate of the heat pump 38 can be controlled. The difference between the desired and actual outlet water temperature and flow rate of the heat pump 38 can be used to regulate the entire waste heat utilization device 3.

[0037] It is also possible to finely distribute the waste heat of large oil-immersed transformers based on the waste heat absorption conditions at the rear end, so as to maximize the heat utilization rate of the transformer waste heat utilization device. Example 2

[0038] The waste heat disposal device 37 is not limited to the structure of the first embodiment. It can also utilize waste heat utilization devices such as thermoelectric generators, or combine heat pumps 38, terminal heat utilization devices 39, and thermoelectric generators. A thermoelectric generator is a specialized device that uses the thermocouple principle to directly convert thermal energy into electrical energy. A thermoelectric generator utilizes the Seebeck effect to directly convert thermal energy into electrical energy. It primarily consists of a combustion furnace, a power generation unit, a heat pipe, and cooling blades.

[0039] In specific applications, a thermoelectric generator is typically connected to a warm water pipe and a cold water pipe. By connecting the transformer waste heat recovery device 3 to the warm water pipe and feeding water from the natural environment into the cold water pipe, the thermoelectric generator can generate electricity. After generating electricity, the warm water from the waste heat recovery device 3 can be returned to the circulation system or fed back into the heat pump 38, depending on the specific application. Example 3

[0040] In the heat exchange device, the oil-water heat exchanger 35 in Example 1 can also be replaced by a combination of a heat exchanger and an oil pump (oil-oil heat exchanger), or other sealable heat exchange devices, and the cooling medium water therein can also be replaced according to the situation, such as ethanol, a mixture of ethanol and water, etc.

[0041] In the embodiments of the present invention, technical features that are not described in detail are all existing technologies or conventional technical means and will not be described in detail here.

[0042] Finally, it should be noted that the above embodiments are only specific implementation methods of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any person skilled in the art can modify or easily conceive of changes to the technical solutions described in the above embodiments within the technical scope disclosed by the present invention, or replace some of the technical features therein with equivalents. Such modifications, changes or replacements do not deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention.

Claims

1. A waste heat utilization system for a large oil-immersed transformer, wherein the large oil-immersed transformer adopts a cooling main pipe cooling structure, including air-cooling / self-cooling cooling devices, a control cabinet, and a waste heat utilization device symmetrically installed on both sides of the oil tank of the large oil-immersed transformer, characterized in that: The air-cooled / self-cooled cooling device includes a plurality of fins, the upper part of the fins is connected to the side wall of the upper cooling mother pipe through the upper connecting pipe, the upper cooling mother pipe is connected to the top of the oil tank of the large oil-immersed transformer through a plurality of upper cooling branch mother pipes, the lower part of the fins is connected to the side wall of the lower cooling mother pipe through the lower connecting pipe, the lower cooling mother pipe is connected to the lower part of the oil tank side of the large oil-immersed transformer through a plurality of lower cooling branch mother pipes, the upper cooling branch mother pipe and the lower cooling branch mother pipe are L-shaped bending structures, and the upper cooling mother pipe and the lower cooling mother pipe are closed structures at both ends; the waste heat The utilization device includes a heat exchange device and a waste heat disposal device. One side of the heat exchange device is connected to the upper cooling branch mother pipe through a heat exchange connecting pipe 1, and the other side of the heat exchange device is connected to the waste heat disposal device through a heat exchange connecting pipe 2; a variable frequency oil pump is installed on the lower cooling branch mother pipe or the upper cooling branch mother pipe, and the frequency converter of the variable frequency oil pump is installed in the control cabinet; temperature sensors and flow sensors are installed in all pipelines, and an oil level temperature sensor is installed in the oil tank of the large oil-immersed transformer. All sensors are electrically connected to the CPU or industrial control machine in the control cabinet through data cables.

2. The large oil-immersed transformer waste heat utilization system according to claim 1 is characterized in that: The heat exchange device includes an oil-water heat exchanger, a heat exchange connecting pipeline includes an upper waste heat recovery branch pipe, an upper waste heat recovery main pipe, a lower waste heat recovery main pipe and a total waste heat recovery main pipe with a bent structure, the upper cooling branch main pipe includes an upper cooling longitudinal branch main pipe and an upper cooling transverse branch main pipe, an electric three-way valve is installed between the upper cooling longitudinal branch main pipe and the upper cooling transverse branch main pipe, the lower end of the upper cooling longitudinal branch main pipe is connected to the top of the oil tank of the large oil-immersed transformer, and the upper end of the upper cooling longitudinal branch main pipe is connected to the electric three-way valve outlet. Outlet 2 of the electric three-way valve is connected to the end of the upper cooling horizontal branch mother pipe, outlet 3 of the electric three-way valve is connected to one end of the upper waste heat recovery branch pipe, the other end of the upper waste heat recovery branch pipe is connected to the side wall of the upper waste heat recovery mother pipe, one end of the upper waste heat recovery mother pipe is a closed structure, the other ends of the two upper waste heat recovery mother pipes are connected to one end of the total waste heat recovery mother pipe through a three-way pipe joint, the other end of the total waste heat recovery mother pipe is connected to the oil-water heat exchanger, one end of the lower waste heat recovery mother pipe is connected to the oil-water heat exchanger, and the other end of the lower waste heat recovery mother pipe is connected to the lower part of the oil tank side wall of the large oil-immersed transformer.

3. The large oil-immersed transformer waste heat utilization system according to claim 2 is characterized in that: The oil-water heat exchanger includes: an oil-side oil pump of the oil-water heat exchanger and an oil-side oil pump of the oil-water heat exchanger. The oil-side oil pump of the oil-water heat exchanger and the oil-side oil pump of the oil-water heat exchanger are variable frequency oil pumps. The frequency converters corresponding to the oil-side oil pump of the oil-water heat exchanger and the oil-water heat exchanger water side oil pump are installed in the control cabinet.

4. The large oil-immersed transformer waste heat utilization system according to claim 3 is characterized in that: The waste heat disposal device includes a waste heat disposal pipeline, a heat pump and a terminal heat equipment. The water side of the oil-water heat exchanger is connected to one side of the heat pump, and the other side of the heat pump is connected to the terminal heat equipment through the waste heat disposal pipeline. The heat pump is equipped with a variable frequency oil pump on the terminal heat equipment side, and the frequency converter of the variable frequency oil pump on the terminal heat equipment side is installed in the control cabinet.

5. The large oil-immersed transformer waste heat utilization system according to claim 1 is characterized in that: The waste heat disposal device includes a thermoelectric generator.

6. The large oil-immersed transformer waste heat utilization system according to claim 1, characterized in that: The heat exchange device includes an oil-oil heat exchanger.

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