Transformer oil flow cooling system general test platform and submersible pump lift type selection method

Abstract

The invention discloses a general test platform for a transformer oil flow cooling system and an oil-submerged pump lift type selection method. The general test platform comprises an oil-submerged pump, a pressure difference detection assembly, a transformer oil tank equivalent resistance part and a heat exchanger equivalent resistance part. An oil outlet of the transformer oil tank equivalent resistance piece is connected with an oil inlet of the heat exchanger equivalent resistance piece through an oil-submerged pump; an oil flow inlet of the transformer oil tank equivalent resistance piece is connected with an oil flow outlet of the heat exchanger equivalent resistance piece through a flow meter and a valve; the pressure difference detection assembly is connected with the transformer oil tank equivalent resistance piece and the heat exchanger equivalent resistance piece and used for detecting the pressure difference between the two ends of the transformer oil tank equivalent resistance piece and the pressure difference between the two ends of the heat exchanger equivalent resistance piece. According to the method, the complicated transformer cooling system design can be dealt with, and the lift of the oil-submerged pump can be selected more accurately and scientifically, so that the effectiveness of the cooling system is improved, and safe and stable operation of a large-scale power transformer is guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of transformer cooling system optimization, in particular to a universal testing platform for transformer oil flow cooling system and a submersible oil pump head selection method. Background Art

[0002] Large power transformers generate a lot of heat during operation, and an effective cooling system is required to ensure the stable operation of the transformer and extend its service life. The forced oil circulation air cooling system forces the oil to circulate through the oil pump, so that the oil flows through the air cooler for heat dissipation, thereby achieving the purpose of cooling the transformer to stabilize the operating parameters. The system is mainly composed of a heat exchanger, a circulating oil pump, a cooling fan, etc. The submersible oil pump drives the oil to circulate continuously, and exchanges heat with the cooling medium air to achieve heat dissipation and cooling. At the same time, PLC is used as the controller, the top oil temperature of the transformer is used as the controlled quantity, and the temperature threshold of the differential margin is used as the control strategy to achieve automatic balanced switching of the cooler. This system is a typical fluid heat exchange system. The accurate evaluation and measurement of the overall resistance of the system is related to the stability of the transformer system. However, the types of transformers are complex and the heat dissipation requirements are diverse. More than any transformer requires a specially designed independent cooling system. The design methods mostly rely on empirical parameters and lack a corresponding scientific and general test platform.

[0003] The driving device of the transformer forced oil circulation air cooling system is a submersible pump. The basic performance parameters of the submersible pump are displacement and head, which determine the working capacity and application range of the pump. The displacement determines the flow rate of the cooling oil and the heat load of the heat exchange. The head is affected by many factors, including pipeline resistance, changes in liquid properties, pump wear and system working conditions. At present, the selection of transformer submersible pumps mostly adopts empirical methods. It has been found that excessive head leads to negative pressure and other problems. There is a lack of scientific and accurate submersible pump head selection method. Summary of the invention

[0004] In order to solve the deficiencies in the prior art, the present invention provides a universal test platform for transformer oil flow cooling system and a submersible oil pump head selection method, which can cope with complex transformer cooling system design and can select the submersible oil pump head more accurately and scientifically, so as to improve the effectiveness of the cooling system and ensure the safe and stable operation of large power transformers.

[0005] The present invention adopts the following technical solution.

[0006] In the first aspect, the present invention provides a universal test platform for a transformer oil flow cooling system, comprising: a submersible oil pump and a pressure difference detection component, the universal test platform for the transformer oil flow cooling system also comprising: a transformer oil tank equivalent resistance component, used to simulate the transformer oil tank resistance; a heat exchanger equivalent resistance component, arranged on one side of the transformer oil tank equivalent resistance component, used to simulate the heat exchanger resistance; wherein the oil flow outlet of the transformer oil tank equivalent resistance component and the oil flow inlet of the heat exchanger equivalent resistance component are connected through a submersible oil pump; the oil flow inlet of the transformer oil tank equivalent resistance component and the oil flow outlet of the heat exchanger equivalent resistance component are connected through a flow meter and a valve; the pressure difference detection component is connected to the transformer oil tank equivalent resistance component and the heat exchanger equivalent resistance component, and is used to detect the pressure difference at both ends of the transformer oil tank equivalent resistance component and the pressure difference at both ends of the heat exchanger equivalent resistance component.

[0007] Preferably, the transformer oil tank equivalent resistance member includes: an equivalent oil tank, a first plug and a first screw thread; the oil flow inlet of the equivalent oil tank is connected to the oil flow outlet of the flow meter; the oil flow outlet of the equivalent oil tank is connected to the oil flow inlet of the submersible pump; at least one first plug is provided, and one end of the first plug can be detachably inserted into the interior of the equivalent oil tank for adjusting the equivalent resistance of the transformer oil tank equivalent resistance member; the first screw thread can be detachably provided on the side wall of the equivalent oil tank for fixing the first plug.

[0008] Preferably, the heat exchanger equivalent resistance member comprises: a main body, a second plug and a second screw thread; the inlet of the main body is connected to the oil flow inlet of the submersible pump, and the outlet of the main body is connected to the oil flow inlet of the flow meter; at least one second plug is provided, and one end of the second plug can be detachably inserted into the interior of the main body for adjusting the equivalent resistance of the heat exchanger equivalent resistance member; the second screw thread is detachably provided on the side wall of the main body for fixing the second plug.

[0009] Preferably, the pressure difference detection component includes: a first pressure difference sensor, connected to the two ends of the transformer oil tank equivalent resistance part, for detecting the pressure difference at both ends of the transformer oil tank equivalent resistance part; a second pressure difference sensor, connected to the two ends of the submersible pump, for detecting the pressure difference at both ends of the submersible pump; a third pressure difference sensor, connected to the two ends of the heat exchanger equivalent resistance part, for detecting the pressure difference at both ends of the heat exchanger equivalent resistance part; a fourth pressure difference sensor, connected to the two ends of the valve, for detecting the pressure difference at both ends of the valve.

[0010] Preferably, the universal test platform for transformer oil flow cooling system further comprises: a high-position oil tank, which is arranged above the transformer oil tank equivalent resistance part and connected to the transformer oil tank equivalent resistance part, and is used to collect transformer cooling oil overflowing from the transformer oil tank equivalent resistance part.

[0011] In a second aspect, the present invention provides a method for selecting the head of a submersible pump of a transformer oil flow cooling system using the aforementioned universal test platform for transformer oil flow cooling systems, comprising the following steps: constructing a transformer oil tank resistance simulation model and a heat exchanger tube resistance simulation model; given a local resistance coefficient, calculating the resistance of the transformer oil tank and the resistance of the flow channel in the heat exchanger tube respectively through the constructed transformer oil tank resistance simulation model and the heat exchanger tube resistance simulation model; adjusting the equivalent resistance of the transformer oil tank equivalent resistance component and the heat exchanger equivalent resistance component in the universal test platform for transformer oil flow cooling systems so that they are equal to the calculated resistance of the transformer oil tank and the resistance of the flow channel in the heat exchanger tube respectively; using the transformer oil flow cooling system The universal test platform measures pressure difference data, including pressure difference data at both ends of the transformer equivalent resistance component and pressure difference data at both ends of the heat exchanger equivalent resistance component; the obtained pressure difference data is substituted into the transformer oil tank resistance simulation model and the heat exchanger tube resistance simulation model, and the local resistance coefficient is corrected to obtain the corrected transformer oil tank resistance simulation model and the heat exchanger tube resistance simulation model; based on the mass and momentum balance principle of the flow equation, the corrected transformer oil tank resistance simulation model and the heat exchanger tube resistance simulation model are coupled to establish a transformer oil flow cooling system resistance simulation total model; the transformer oil flow cooling system resistance simulation total model is used to calculate the total system resistance, and the lift of the submersible pump is selected according to the set ratio of the total system resistance.

[0012] Preferably, the set ratio is 120%.

[0013] Preferably, the construction of the transformer oil tank resistance simulation model includes the following steps: establishing a physical model of the transformer oil tank structure and internal windings, iron core and oil flow channels; dividing the physical model into grids and setting boundary conditions; and using fluid mechanics to construct the transformer oil tank resistance simulation model.

[0014] Preferably, the construction of the heat exchanger tube resistance simulation model comprises the following steps: determining the heat exchanger type, fin shape and arrangement, and structural parameters of the heat exchanger; determining the transformer cooling oil physical property parameters; establishing a heat exchanger tube resistance simulation model regarding the heat exchanger structure, type, fin shape and arrangement, and transformer cooling oil physical properties.

[0015] Preferably, the method for selecting the head of the submersible pump of the transformer oil flow cooling system also includes the following steps: constructing a pipeline along-the-line resistance calculation model and a elbow valve local resistance calculation model; using a universal test platform for the transformer oil flow cooling system to measure the local pressure difference of the connecting pipeline, elbow and valve; substituting the measured local pressure difference of the connecting pipeline, elbow and valve into the pipeline along-the-line resistance calculation model and the elbow valve local resistance calculation model, correcting the local resistance parameters, and obtaining the corrected pipeline along-the-line resistance calculation model and the elbow valve local resistance calculation model; coupling the corrected pipeline along-the-line resistance calculation model and the elbow valve local resistance calculation model with the corrected transformer oil tank resistance simulation model and the heat exchanger tube resistance simulation model according to the mass and momentum balance principle of the flow equation to obtain an updated transformer oil flow cooling system resistance simulation overall model; based on the updated transformer oil flow cooling system resistance simulation overall model, selecting the head of the submersible pump.

[0016] The beneficial effect of the present invention is that, compared with the prior art, the universal test platform for transformer oil flow cooling system provided by the present invention can simulate the resistance of the transformer oil tank and the heat exchanger by providing the transformer oil tank equivalent resistance part and the heat exchanger equivalent resistance part, and facilitate the adjustment of the resistance of the transformer oil tank and the heat exchanger. At the same time, the pressure difference detection component provided can measure the pressure difference at both ends of the transformer oil tank equivalent resistance part and the pressure difference at both ends of the heat exchanger equivalent resistance part, and the pressure difference can be combined with the flow data measured by the flowmeter to calculate the resistance of the transformer oil tank equivalent resistance part and the heat exchanger equivalent resistance part, so as to obtain the total system resistance of the universal test platform for transformer oil flow cooling system, and select the head of the submersible pump according to the set ratio of the total system resistance, so that the selection of the head of the submersible pump is more accurate, and can cope with the complex transformer cooling system design, can improve the effectiveness of the cooling system, and ensure the safe and stable operation of large power transformers.

[0017] In addition, the method for selecting the head of a submersible pump for a transformer oil flow cooling system provided by the present invention, based on the principle of fluid mechanics, constructs a transformer oil tank resistance simulation model and a heat exchanger tube resistance simulation model, so as to facilitate the design of the equivalent resistance of the transformer oil tank equivalent resistance parts and the heat exchanger equivalent resistance parts of the universal test platform for the transformer oil flow cooling system. And by using the pressure difference data measured by the designed universal test platform, the local resistance coefficient in the constructed transformer oil tank resistance simulation model and the heat exchanger tube resistance simulation model can be corrected, thereby improving the accuracy of the resistance model simulation. Finally, based on the mass and momentum balance principle of the flow equation, the corrected transformer oil tank resistance simulation model and the heat exchanger tube resistance simulation model are coupled to obtain the total system resistance, so as to facilitate the selection of the submersible pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1It is a structural schematic diagram of a universal test platform for transformer oil flow cooling system in the present invention;

[0019] Figure 2 The present invention is a schematic flow chart of a method for selecting the head of a submersible oil pump in a transformer oil flow cooling system.

[0020] Reference numerals in the figures:

[0021] 1. Equivalent resistance parts of transformer oil tank; 2. High-level oil tank; 3. Submersible oil pump; 4. Equivalent resistance parts of heat exchanger; 5. Flow meter; 6. Valve; 7. First differential pressure sensor; 8. Second differential pressure sensor; 9. Third differential pressure sensor; 10. Fourth differential pressure sensor; 11. First plug; 12. First screw thread; 13. Second plug; 14. Second screw thread. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0023] Combination Figure 1 Embodiment 1 of the present invention provides a universal test platform for a transformer oil flow cooling system, including: a transformer oil tank equivalent resistance component 1, a high-level oil tank 2, a flow meter 5, a heat exchanger equivalent resistance component 4, a submersible pump 3, a valve 6, a first differential pressure sensor 7, a second differential pressure sensor 8, a third differential pressure sensor 9, and a fourth differential pressure sensor 10.

[0024] The transformer oil tank equivalent resistance component 1 includes a cylindrical equivalent oil tank for storing transformer cooling oil. The side wall of the equivalent oil tank is detachably mounted with at least one first plug 11 for adjusting resistance. The first plug 11 is connected to the side wall of the equivalent oil tank through a first screw thread 12, and one end of the first plug 11 is inserted into the interior of the equivalent oil tank. The equivalent resistance is controlled by adjusting the number of first plugs to simulate the transformer oil tank resistance.

[0025] The high-position oil tank 2 is connected to the transformer oil tank equivalent resistance member 1, and is arranged at a high position on the upper part of the top plate of the transformer oil tank equivalent resistance member 1, and is used to collect the transformer cooling oil overflowing from the transformer oil tank equivalent resistance member 1 to prevent the oil temperature from rising rapidly and the volume from expanding rapidly when the transformer fails, causing a fault.

[0026] The submersible pump 3 is connected to the oil flow outlet of the transformer oil tank equivalent resistance component 1 through the submersible pump oil flow inlet, serving as a driving component of the transformer oil flow cooling system.

[0027] The heat exchanger equivalent resistance member 4 is connected to the oil flow outlet of the submersible pump through the oil flow inlet of the heat exchanger equivalent resistance member, and is a circular tube structure. The side wall of the main body of the heat exchanger equivalent resistance member 4 can be detachably inserted with at least one second insert tube 13 for adjusting the resistance. The second insert tube is connected to the outer wall of the main body through a second screw thread 14, and one end is inserted into the interior of the heat exchanger equivalent resistance member 4. The equivalent resistance is controlled by adjusting the number of insert tubes to simulate the heat exchanger resistance.

[0028] The flow meter 5 is connected to the oil outlet of the heat exchanger equivalent resistance part 4 through the flow meter oil inlet, and is used to measure the system cooling oil flow. A straight pipe section needs to be set before the cooling oil enters the flow meter 5 to ensure the stability of the flow; the valve 6 is connected to the oil outlet of the flow meter 5, which is a ball valve or a butterfly valve, and is used to control the transformer cooling oil flow.

[0029] It is used to connect the interconnected components among the transformer oil tank equivalent resistance part 1, the high-level oil tank 2, the submersible oil pump 3, the heat exchanger equivalent resistance part 5 and the valve 6 through connecting pipes and elbows.

[0030] The first differential pressure sensor 7 is arranged at both ends of the transformer oil tank equivalent resistance part 1, the second differential pressure sensor 8 is arranged at both ends of the submersible pump 3, the third differential pressure sensor 9 is arranged at both ends of the heat exchanger equivalent resistance part 5, and the fourth differential pressure sensor 10 is arranged at both ends of the valve 6, which are respectively used to measure the pressure difference at both ends of the transformer oil tank equivalent resistance part 1, the pressure difference at both ends of the submersible pump 3, the pressure difference at both ends of the heat exchanger equivalent resistance part 5 and the pressure difference at both ends of the valve 6. Combined with the flow rate data, the flow resistance of the aforementioned components under working conditions can be obtained.

[0031] Combination Figure 2 Embodiment 2 of the present invention provides a universal test platform for transformer oil flow cooling system and a method for selecting the head of a submersible oil pump, comprising the following steps:

[0032] Step S1, according to the transformer oil tank structure and internal winding, core and oil flow channel parameters, using CFD (Computational Fluid Dynamics), a transformer oil tank resistance simulation model is established to obtain the transformer oil tank resistance.

[0033] The specific process is as follows: first, a physical model of the transformer oil tank structure and internal windings, iron core and oil flow channels is established. After the physical model is imported into the software to divide the grid, the boundary conditions are set using computational fluid dynamics software to establish a CFD resistance simulation model, the inlet conditions (cooling oil flow data) are input, and the local resistance coefficient is given according to experience to calculate the transformer oil tank resistance data.

[0034] Step S2, establishing a heat exchanger tube resistance simulation model according to the heat exchanger structure (fin tube, bare tube, etc.) to obtain the flow resistance in the heat exchanger tube.

[0035] Specifically, the type of heat exchanger, fin shape and arrangement, and specific structural parameters of the heat exchanger (such as tube diameter, fin spacing, etc.) are determined, and the physical properties of the transformer cooling oil (such as viscosity, specific heat capacity, etc.) are determined. According to the correlation formula, a heat exchanger tube resistance calculation model is established for the heat exchanger structure, type, fin shape and arrangement, and physical properties of the transformer cooling oil. The local resistance coefficient is given according to experience, and the heat exchanger tube resistance data is calculated.

[0036] Step S3, according to the transformer oil tank resistance and the flow resistance in the heat exchanger tube calculated in steps 1 and 2, adjust the equivalent resistance of the transformer oil tank equivalent resistance component 1 and the heat exchanger equivalent resistance component 4 in the universal test platform of the transformer oil flow cooling system, so that they are equal to the calculated resistance of the transformer oil tank and the flow resistance in the heat exchanger tube, respectively.

[0037] Step S4, combining the transformer oil tank equivalent resistance component 1, the high-level oil tank 2, the flow meter 5, the heat exchanger equivalent resistance component 4, the submersible pump 3, the valve 6, the pressure difference sensor, the connecting pipes and the elbows, to build a universal test platform for the transformer oil flow cooling system.

[0038] Step S5, based on the established universal test platform for transformer oil flow cooling system, establish a pipeline along-the-line resistance calculation model, an elbow local resistance model and a valve local resistance model.

[0039] Step S6: Use the universal test platform for transformer oil flow cooling system (hereinafter referred to as the test platform) to measure the pressure difference data of each component, including the pressure difference of the transformer equivalent resistance component 1, the heat exchanger equivalent resistance component 4, the pipeline, the elbow and the valve. The pressure difference is obtained by the pressure difference sensor of each component on the test platform.

[0040] Step S7, substitute the pressure difference data obtained according to the test platform into the transformer oil tank resistance simulation model, the heat exchanger tube resistance simulation model, the pipeline along-the-way resistance calculation model, the elbow and valve local resistance model, correct the local resistance coefficients of the transformer oil tank resistance simulation model, the heat exchanger tube resistance simulation model, the pipeline along-the-way resistance calculation model, the elbow local resistance model and the valve local resistance model, and obtain the corrected transformer oil tank resistance simulation model, the heat exchanger tube resistance simulation model, the pipeline along-the-way resistance calculation model, the elbow and valve local resistance model.

[0041] Step S8, based on the mass and momentum balance principle of the flow equation, the modified transformer oil tank resistance simulation model, the heat exchanger tube resistance simulation model, the pipeline along-the-line resistance calculation model, and the elbow and valve local resistance calculation model are coupled to establish a total resistance simulation model of the transformer oil flow cooling system to calculate the total resistance of the system;

[0042] Step S9, based on the set ratio of the total resistance of the system, accurately select the head of the submersible pump of the system, wherein the set ratio is preferably 120%.

[0043] The beneficial effect of the present invention is that, compared with the prior art, the universal test platform for transformer oil flow cooling system provided by the present invention can simulate the resistance of the transformer oil tank and the heat exchanger by providing the transformer oil tank equivalent resistance part and the heat exchanger equivalent resistance part, and facilitate the adjustment of the resistance of the transformer oil tank and the heat exchanger. At the same time, the pressure difference detection component provided can measure the pressure difference at both ends of the transformer oil tank equivalent resistance part and the pressure difference at both ends of the heat exchanger equivalent resistance part, and the pressure difference can be combined with the flow data measured by the flowmeter to calculate the resistance of the transformer oil tank equivalent resistance part and the heat exchanger equivalent resistance part, so as to obtain the total system resistance of the universal test platform for transformer oil flow cooling system, and select the head of the submersible pump according to the set ratio of the total system resistance, so that the selection of the head of the submersible pump is more accurate, and can cope with the complex transformer cooling system design, can improve the effectiveness of the cooling system, and ensure the safe and stable operation of large power transformers.

[0044] In addition, the method for selecting the head of a submersible pump for a transformer oil flow cooling system provided by the present invention, based on the principle of fluid mechanics, constructs a transformer oil tank resistance simulation model and a heat exchanger tube resistance simulation model, so as to facilitate the design of the equivalent resistance of the transformer oil tank equivalent resistance parts and the heat exchanger equivalent resistance parts of the universal test platform for the transformer oil flow cooling system. And by using the pressure difference data measured by the designed universal test platform, the local resistance coefficient in the constructed transformer oil tank resistance simulation model and the heat exchanger tube resistance simulation model can be corrected, thereby improving the accuracy of the resistance model simulation. Finally, based on the mass and momentum balance principle of the flow equation, the corrected transformer oil tank resistance simulation model and the heat exchanger tube resistance simulation model are coupled to obtain the total system resistance, so as to facilitate the selection of the submersible pump.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A universal test platform for transformer oil flow cooling system, comprising: The submersible pump (3) and the pressure difference detection assembly are characterized by: The transformer oil flow cooling system universal test platform also includes: A transformer oil tank equivalent resistance component (1) is used to simulate the transformer oil tank resistance; A heat exchanger equivalent resistance member (4) is arranged on one side of the transformer oil tank equivalent resistance member (1) and is used to simulate the heat exchanger resistance; The oil flow outlet of the transformer oil tank equivalent resistance component (1) and the oil flow inlet of the heat exchanger equivalent resistance component (4) are connected via a submersible oil pump (3); the oil flow inlet of the transformer oil tank equivalent resistance component (1) and the oil flow outlet of the heat exchanger equivalent resistance component (4) are connected via a flow meter (5) and a valve (6); The pressure difference detection component is connected to the transformer oil tank equivalent resistance component (1) and the heat exchanger equivalent resistance component (4), and is used to detect the pressure difference at both ends of the transformer oil tank equivalent resistance component (1) and the heat exchanger equivalent resistance component (4). The pressure difference at both ends of the resistance member (4).

2. The universal test platform for transformer oil flow cooling system according to claim 1 is characterized in that: The transformer oil tank equivalent resistance member (1) comprises: an equivalent oil tank, a first insert pipe (11) and A first screw thread (12); The oil flow inlet of the equivalent oil tank is connected to the oil flow outlet of the flow meter (5); the oil flow outlet of the equivalent oil tank is connected to the oil flow inlet of the submersible oil pump (3); At least one first insertion tube (11) is provided, and one end of the first insertion tube (11) is detachably inserted into the Inserted into the interior of the equivalent oil tank, used to adjust the equivalent resistance of the transformer oil tank equivalent resistance member (1); The first screw thread (12) is detachably arranged on the side wall of the equivalent oil tank and is used to fix the first inserting tube (11).

3. The universal test platform for transformer oil flow cooling system according to claim 1 is characterized in that: The heat exchanger equivalent resistance member (4) comprises: a main body, a second insert pipe (13) and a second screw thread (14); The inlet of the main body is connected to the oil flow inlet of the submersible pump (3), and the outlet of the main body is connected to the flow connected to the oil flow inlet of the meter (5); At least one second insert tube (13) is provided, and one end of the second insert tube (13) is detachably inserted into the interior of the main body, so as to adjust the equivalent resistance of the heat exchanger equivalent resistance component (4); The second screw thread (13) is detachably arranged on the side wall of the main body and is used to fix the second insertion tube (13).

4. The universal test platform for transformer oil flow cooling system according to any one of claims 1 to 3, characterized in that: The pressure difference detection component comprises: A first differential pressure sensor (7) is connected to two ends of the transformer oil tank equivalent resistance member (1) and is used to detect the differential pressure at the two ends of the transformer oil tank equivalent resistance member (1); A second differential pressure sensor (8) is connected to both ends of the submersible pump (3) and is used to detect the differential pressure at both ends of the submersible pump (3); A third differential pressure sensor (9) is connected to both ends of the heat exchanger equivalent resistance element (4) and is used to detect the differential pressure at both ends of the heat exchanger equivalent resistance element (4); The fourth differential pressure sensor (10) is connected to both ends of the valve (6) and is used to detect the differential pressure at both ends of the valve (6).

5. The universal test platform for transformer oil flow cooling system according to any one of claims 1 to 3, characterized in that: The transformer oil flow cooling system universal test platform also includes: The high-position oil tank (2) is arranged above the transformer oil tank equivalent resistance member (1) and connected to the transformer oil tank equivalent resistance member (1) and is used for collecting transformer cooling oil overflowing from the transformer oil tank equivalent resistance member (1).

6. A method for selecting the head of a submersible oil pump of a transformer oil flow cooling system using the universal test platform for transformer oil flow cooling system according to any one of claims 1 to 5, characterized in that: The following steps are involved: Construct the transformer tank resistance simulation model and the heat exchanger tube resistance simulation model; Given the local resistance coefficient, the resistance of the transformer tank and the resistance of the flow channel in the heat exchanger tube are calculated respectively by constructing the transformer tank resistance simulation model and the heat exchanger tube resistance simulation model; Adjusting the equivalent resistance of the transformer oil tank equivalent resistance component (1) and the heat exchanger equivalent resistance component (4) in the universal test platform for transformer oil flow cooling system to be equal to the calculated resistance of the transformer oil tank and the resistance of the flow channel in the heat exchanger tube, respectively; Using a universal test platform for transformer oil flow cooling system, pressure difference data is measured, including pressure difference data at both ends of the transformer equivalent resistance component (1) and pressure difference data at both ends of the heat exchanger equivalent resistance component (4); Substituting the obtained pressure difference data into the transformer oil tank resistance simulation model and the heat exchanger tube resistance simulation model, correcting the local resistance coefficient, and obtaining the corrected transformer oil tank resistance simulation model and the heat exchanger tube resistance simulation model; Based on the mass and momentum balance principle of the flow equation, the modified transformer oil tank resistance simulation model and the heat exchanger tube resistance simulation model are coupled to establish the transformer oil flow cooling system resistance simulation model. The total resistance of the transformer oil flow cooling system is calculated using the total resistance simulation model, and the head of the submersible pump is selected according to the set ratio of the total resistance of the system.

7. The method for selecting the head of a submersible oil pump in a transformer oil flow cooling system according to claim 6, characterized in that: The setting ratio is 120%.

8. The method for selecting the head of a submersible oil pump in a transformer oil flow cooling system according to claim 6, characterized in that: The construction of the transformer oil tank resistance simulation model comprises the following steps: Establish physical models of transformer tank structure and internal windings, core and oil flow channels; Divide the physical model into grids and set boundary conditions; Using fluid mechanics, a transformer tank resistance simulation model is constructed.

9. The method for selecting the head of a submersible oil pump in a transformer oil flow cooling system according to claim 6, characterized in that: The construction of the heat exchanger tube internal resistance simulation model comprises the following steps: Determine the heat exchanger type, fin shape and arrangement, and structural parameters of the heat exchanger; Determine the physical parameters of transformer cooling oil; A heat exchanger tube resistance simulation model is established based on the heat exchanger structure, type, fin shape and arrangement, and transformer cooling oil properties.

10. The method for selecting the head of a submersible oil pump in a transformer oil flow cooling system according to claim 6, characterized in that: The transformer oil flow cooling system submersible pump head selection method also includes the following steps: Construct the pipeline along-the-line resistance calculation model and the elbow valve local resistance calculation model; The local pressure difference of connecting pipes, elbows and valves is measured using the universal test platform for transformer oil flow cooling system; Substituting the measured local pressure difference of the connecting pipeline, elbow and valve into the pipeline along-line resistance calculation model and the elbow valve local resistance calculation model, correcting the local resistance parameters, and obtaining the corrected pipeline along-line resistance calculation model and the elbow valve local resistance calculation model; The revised pipeline along-the-line resistance calculation model and elbow valve local resistance calculation model are coupled with the revised transformer oil tank resistance simulation model and heat exchanger tube resistance simulation model according to the mass and momentum balance principle of the flow equation to obtain an updated transformer oil flow cooling system resistance simulation overall model. Based on the updated overall model of transformer oil flow cooling system resistance simulation, the head of the submersible oil pump is selected.

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