An insulating oil deterioration flow heat transfer characteristic test module and test method

Abstract

The application discloses a kind of insulating oil deterioration flow heat transfer characteristic test module and test method, test module includes circulating oil path unit, flow characteristic test unit, heat transfer characteristic test unit, valve switching unit, dynamic monitoring unit and data processing unit.Flow test, heat transfer test, collaborative test and the selective switching of bypass circulation mode can be realized by valve switching unit;Dynamic monitoring unit includes oil quality detection piece and image acquisition piece, for synchronously collecting oil quality parameter and flow pattern image;Data processing unit carries out time synchronization, normalization and weighted fusion to flow parameter, heat transfer parameter, oil quality parameter and flow pattern image parameter, and calculates comprehensive performance deterioration index.The application can simulate transformer cold start, steady state, load fluctuation and overload and other actual working conditions, realize the synchronous monitoring and fusion evaluation of "chemical-flow-heat-flow pattern" multi-source information in insulating oil deterioration process.

Description

Technical Field

[0001] This invention relates to the field of electrical equipment insulation medium condition detection and flow heat transfer testing technology, and particularly to a test module and test method for the flow heat transfer characteristics of deteriorated insulating oil. Background Technology

[0002] With the advancement of green power grid construction, natural ester insulating oil, due to its high ignition point, biodegradability, and good hygroscopic properties, is gradually being used as a substitute or supplementary medium for traditional mineral oil in some high-voltage transformers. However, natural ester insulating oil differs from mineral oil in its physicochemical properties. During operation, it may not only undergo oxidative aging but also hydrolytic aging under the combined effects of moisture, temperature, and the paper insulation material. After the insulating oil deteriorates, its viscosity, acid value, moisture content, and dielectric loss factor may change, further leading to increased flow resistance and decreased heat transfer efficiency, thus affecting the transformer's heat dissipation performance and operational safety.

[0003] Currently, research on the degradation process of insulating oil mainly focuses on the detection of oil chemical indicators, such as acid value, dielectric loss factor, and moisture content. However, there is a lack of systematic testing methods for the dynamic changes in the flow and heat transfer characteristics of insulating oil during degradation. Existing flow and heat transfer testing devices are mostly designed for ordinary liquid or mineral insulating oils, and usually do not fully consider the changes in the flow and heat transfer performance of natural ester insulating oils under conditions of high-temperature oxidation, hydrolytic degradation, changes in viscosity-temperature characteristics, and interaction with oil-paper insulation materials. This leads to discrepancies between test data and actual transformer operating conditions.

[0004] Specifically, existing technologies have at least the following shortcomings: First, the testing functions are relatively limited, lacking the ability to monitor multiple parameters simultaneously. Traditional testing devices can typically only measure flow pressure drop or heat transfer parameters individually, making it difficult to simultaneously acquire information on flow resistance coefficient, Nusselt number, oil chemical properties, and flow regime changes under the same oil sample, the same degradation stage, and the same test conditions. Therefore, it is difficult to comprehensively depict the dynamic correspondence between changes in chemical properties, flow resistance, and heat transfer performance during the degradation of insulating oil.

[0005] Second, existing testing methods are insufficient to accurately simulate the actual operating conditions of transformers. During actual operation, transformers experience various conditions such as cold start, steady-state load, load fluctuations, short-term overload, and cooling recovery, and oil temperature and oil velocity are not constant. Existing testing equipment mostly conducts tests under constant temperature, constant current, or single operating conditions, lacking a testing platform capable of dynamically reproducing temperature changes, flow rate changes, and load fluctuations. This results in laboratory test results failing to fully reflect the actual operating conditions of the engineering project.

[0006] Third, the evaluation dimensions are relatively singular, lacking a comprehensive evaluation method that integrates multi-source information. Traditional methods usually rely on a single or a few parameters such as acid value, moisture content, dielectric loss factor, and viscosity to judge the degree of insulation oil degradation. They fail to incorporate flow resistance, heat transfer performance, oil chemical indicators, and bubble flow behavior into a unified evaluation model, making it difficult to accurately determine the comprehensive impact of insulation oil degradation on transformer heat dissipation reliability and oil flow reliability. Summary of the Invention

[0007] To address the problem that existing testing methods for insulating oil degradation processes primarily focus on detecting oil chemical indicators, making it difficult to simultaneously obtain information on the flow resistance, heat transfer performance, oil quality, and flow regime changes of the same oil sample under the same operating conditions, and also difficult to dynamically simulate the temperature, flow velocity, and load changes during actual transformer operation, one objective of this invention is to provide a testing module for the flow and heat transfer characteristics of insulating oil degradation. To achieve the above objectives, the present invention adopts the following technical solution: a test module for the deterioration flow and heat transfer characteristics of insulating oil, comprising a circulating oil circuit unit, a flow characteristic test unit, a heat transfer characteristic test unit, a valve switching unit, a dynamic monitoring unit, and a data processing unit; The circulating oil circuit unit includes an oil pump, a heating component, a cooling component, a circulating pipeline, and a bypass pipeline. The oil pump is used to drive the insulating oil to circulate in the circulating pipeline, and the heating component and the cooling component are used to regulate the temperature of the insulating oil. The flow characteristic testing unit includes a measuring pipe section, a differential pressure sensor, and a flow velocity detection device. The measuring pipe section is selectively connected to the circulation pipeline through the valve switching unit to obtain differential pressure data and flow velocity data during the flow of insulating oil. The heat transfer characteristic testing unit includes a heat exchange tube section, an oil-side temperature detection device, a cooling-side temperature detection device, and a cooling medium flow detection device. The heat exchange tube section is selectively connected to the circulation pipeline through the valve switching unit to obtain heat transfer data between the insulating oil and the cooling medium. The valve switching unit is connected between the circulating oil circuit unit, the flow characteristic test unit, the heat transfer characteristic test unit, and the bypass pipeline, and is used to switch between flow test mode, heat transfer test mode, cooperative test mode, or bypass circulation mode. The dynamic monitoring unit includes an oil quality detection device connected to the circulation pipeline, and an image acquisition device positioned towards the measurement pipe section; The data processing unit is communicatively connected to each detection element; the data processing unit is configured to: perform time synchronization, normalization and weighted fusion on the collected flow parameters, heat transfer parameters, oil quality parameters and flow state image parameters, calculate the comprehensive performance degradation index, and obtain the evaluation result of the insulation oil degradation state based on the comprehensive performance degradation index.

[0008] Furthermore, the measuring pipe section includes a transparent pressure-resistant pipe section and an oil passage simulation plug detachably disposed within the transparent pressure-resistant pipe section, the oil passage simulation plug having at least one of a reduced diameter section, an expanded diameter section, a curved section, a narrow slit section, and a rough wall section.

[0009] Furthermore, the differential pressure sensor is connected across the upstream and downstream sides of the oil passage simulation module, and the flow rate detection element is located at the upstream or downstream straight pipe section of the oil passage simulation module.

[0010] Furthermore, the valve switching unit includes a first branch valve disposed at the inlet of the flow characteristic test unit, a second branch valve disposed at the inlet of the heat transfer characteristic test unit, and a bypass valve disposed at the inlet of the bypass pipeline; the first branch valve, the second branch valve, and the bypass valve are configured to be able to open individually or in combination, so that the insulating oil enters the flow characteristic test unit, enters the heat transfer characteristic test unit, enters both the flow characteristic test unit and the heat transfer characteristic test unit simultaneously, or flows back to the circulation pipeline via the bypass pipeline.

[0011] Furthermore, the heat exchange tube section has an oil-side channel for insulating oil to pass through and a cooling-side channel for cooling medium to pass through; the heat exchange tube section is a shell-and-tube type heat exchange tube section, the oil-side channel is an inner tube, the cooling-side channel is an outer heat exchange channel located outside the inner tube, and the cooling medium is cooling water.

[0012] Furthermore, the oil-side temperature detection devices are respectively installed at the oil inlet and oil outlet of the inner tube, the cooling-side temperature detection devices are respectively installed at the cooling water inlet and cooling water outlet of the outer heat exchange channel, and the cooling medium flow detection device is installed in the cooling water pipeline connected to the outer heat exchange channel.

[0013] Furthermore, the circulating oil circuit unit also includes a frequency converter and a temperature controller. The frequency converter is electrically connected to the oil pump, and the temperature controller is electrically connected to the heating component, the cooling component, and the oil temperature detection element disposed in the circulating pipeline.

[0014] Furthermore, the cooling assembly includes a cooling sleeve, a cooling water pump, and a flow regulating valve. The cooling sleeve is fitted onto the outside of the circulation pipeline, and the cooling water pump, the flow regulating valve, and the cooling sleeve are connected through the cooling water circulation pipeline.

[0015] Furthermore, the oil quality testing device includes at least two of the following: acid value testing device, moisture testing device, and dielectric loss testing device; the image acquisition device is a high-speed camera device, and the measuring tube section is provided with an observation window opposite to the high-speed camera device.

[0016] The insulating oil deterioration flow heat transfer characteristic testing module of the present invention has at least the following beneficial effects: By coordinating the flow characteristic testing unit, heat transfer characteristic testing unit, and valve switching unit, the flow resistance coefficient and Nusselt number during the deterioration of insulating oil can be measured synchronously or at different times. This solves the problem in existing technologies where it is difficult to dynamically obtain the degradation law of flow performance and heat transfer performance under the same oil sample and the same operating conditions. It enables the continuous tracking of the correlation between changes in oil quality indicators, changes in flow resistance, and changes in heat transfer efficiency during the deterioration of insulating oil, facilitating a comprehensive evaluation of the impact of insulating oil deterioration on the heat dissipation performance and flow reliability of transformers.

[0017] By cooperating with the valve switching unit, bypass pipeline, and circulating oil circuit unit, the insulating oil can selectively enter the flow test mode, heat transfer test mode, collaborative test mode, or bypass circulation mode. This solves the problems of traditional test devices having single functions and inconvenient test task switching. It enables the same set of test modules to meet different test requirements such as independent measurement of voltage drop, independent measurement of heat transfer parameters, joint measurement of flow heat transfer parameters, and bypass temperature stabilization circulation, facilitating the automated control and multi-mode switching operation of the test process.

[0018] By cooperating with the oil quality detection components, image acquisition components, and data processing units in the dynamic monitoring unit, the oil quality parameters such as acid value, moisture, and dielectric loss of insulating oil, as well as visual information such as the number of bubbles, bubble size distribution, bubble area ratio, or flow pattern type during the flow process, can be collected simultaneously. This solves the problem of single evaluation dimensions and isolated information in traditional testing methods, enabling multi-source data to be aligned and integrated on the same time axis, facilitating comprehensive perception and judgment of the deterioration state of insulating oil.

[0019] By using a data processing unit to synchronize, normalize, and weight the flow parameters, heat transfer parameters, oil quality parameters, and flow pattern image parameters over time, a comprehensive performance degradation index can be calculated. This solves the problem of existing technologies lacking a unified quantitative index to evaluate the impact of insulating oil degradation on the overall flow and heat transfer performance. It allows the degree of insulating oil degradation to be presented in the form of a comprehensive index and compared with a preset threshold, making it convenient for testing or maintenance personnel to determine when to treat, re-inspect, or replace the oil.

[0020] By coordinating the heating and cooling components, the frequency converter, and the oil pump, the oil temperature and flow rate can be adjusted. The system simulates transformer cold start, steady-state operation, load fluctuation, or overload conditions according to preset temperature and flow rate curves. This solves the problem of insufficient matching between laboratory test conditions and the actual operating environment of transformers, making the test data closer to the actual service state of insulating oil and facilitating the study of the degradation law of the flow and heat transfer performance of insulating oil under dynamic conditions.

[0021] To address the lack of existing testing methods capable of simultaneously acquiring, fusing, analyzing, and comprehensively evaluating flow parameters, heat transfer parameters, oil quality parameters, and flow pattern image parameters during the deterioration process of insulating oil under dynamic operating conditions, another objective of this invention is to provide a testing method for the flow and heat transfer characteristics of deteriorated insulating oil. To achieve the above objectives, the present invention adopts the following technical solution: a method for testing the flow and heat transfer characteristics of deteriorated insulating oil, using an insulating oil circulation testing system. The insulating oil circulation testing system includes a circulation oil circuit, a flow characteristic testing branch selectively connected to the circulation oil circuit, a heat transfer characteristic testing branch selectively connected to the circulation oil circuit, a bypass pipeline, an oil quality detection device, and an image acquisition device; the method includes: The insulating oil is circulated in the circulating oil circuit and adjusted to the preset test conditions; The insulating oil can be selectively allowed to enter the flow characteristic test branch, the heat transfer characteristic test branch, or both the flow characteristic test branch and the heat transfer characteristic test branch, or it can be returned to the circulating oil circuit via the bypass pipeline. Collect pressure difference data and flow velocity data in the flow characteristic test branch, and obtain flow parameters based on the pressure difference data and the flow velocity data; Collect oil-side temperature data, cooling-side temperature data, and cooling medium flow rate data in the heat transfer characteristic test branch, and obtain heat transfer parameters based on the oil-side temperature data, the cooling-side temperature data, and the cooling medium flow rate data; During the test, the oil quality parameters of the insulating oil are collected through the oil quality detection device, and the flow image of the insulating oil is collected through the image acquisition device. The flow parameters, heat transfer parameters, oil quality parameters, and flow image parameters obtained from the flow image are time-synchronized and normalized, and then weighted and fused according to preset weights to obtain a comprehensive performance degradation index. The evaluation results of the insulation oil's deterioration status are obtained based on the comprehensive performance degradation index.

[0022] Furthermore, obtaining the overall performance degradation index includes calculation using the following formula: F(t)=α·Ff(t)+β·FNu(t)+γ·FAV(t)+δ·FW(t)+ε·FB(t); Wherein, F(t) is the comprehensive performance degradation index, Ff(t) is the normalized flow resistance index, FNu(t) is the normalized heat transfer attenuation index, FAV(t) is the normalized acid value index, FW(t) is the normalized moisture index, FB(t) is the normalized bubble characteristic index, and α, β, γ, δ, and ε are weighting coefficients, and α+β+γ+δ+ε=1; the heat transfer attenuation index is determined based on the ratio between the Nusselt number or the reference Nusselt number and the real-time Nusselt number.

[0023] Furthermore, adjusting to the preset test conditions includes: adjusting the heating power and cooling medium flow rate according to the preset temperature curve, and adjusting the oil pump speed according to the preset flow rate curve; the preset temperature curve and the preset flow rate curve are configured to simulate the cold start condition, steady-state operation condition, load fluctuation condition or overload condition of the transformer.

[0024] Furthermore, the flow parameters include a drag coefficient, which is calculated based on the geometric parameters of the measuring pipe section, the density of the insulating oil, the differential pressure data, and the flow velocity data; the heat transfer parameters include the Nusselt number, which is calculated based on the cooling medium flow rate, the oil-side temperature data, the cooling-side temperature data, and the heat exchange area.

[0025] Furthermore, the bubble characteristic indicators are determined based on at least one of the following: bubble number, bubble size distribution, bubble area ratio, and bubble migration speed.

[0026] Furthermore, during the test, the flow characteristic test branch and the heat transfer characteristic test branch are switched at preset time intervals, and the flow parameters, heat transfer parameters and oil quality parameters at the corresponding time points are recorded respectively.

[0027] The method for testing the flow and heat transfer characteristics of deteriorated insulating oil according to the present invention has at least the following beneficial effects: By circulating the insulating oil in the circulating oil circuit and adjusting it to the preset test conditions, and selectively allowing the insulating oil to enter the flow characteristic test branch, the heat transfer characteristic test branch, or both simultaneously, and by simultaneously acquiring flow parameters, heat transfer parameters, oil quality parameters, and flow pattern image parameters in step three, multi-source test data of the insulating oil degradation process can be dynamically acquired on the same time axis. This solves the problem of the separation between flow testing, heat transfer testing, and oil quality monitoring in the existing technology, making it difficult to establish a dynamic correlation. This allows the impact of insulating oil degradation on flow resistance and heat transfer performance to be continuously tracked and analyzed, facilitating the study of the insulating oil degradation mechanism and condition assessment.

[0028] By combining flow parameters obtained from differential pressure and flow velocity data with heat transfer parameters obtained from oil-side temperature data, cooling-side temperature data, and cooling medium flow rate data, the drag coefficient and Nusselt number can be obtained under the same oil sample and the same deterioration stage. This solves the problem of difficulty in establishing a dynamic mapping relationship between flow characteristics and heat transfer characteristics due to separate measurements in existing tests. It enables quantitative analysis of the correlation between viscosity changes, flow resistance changes, flow rate changes, and heat dissipation performance changes during the deterioration process of insulating oil, facilitating the evaluation of transformer heat dissipation reliability and the research on improving insulating oil performance.

[0029] By performing time synchronization, normalization, and weighted fusion of flow parameters, heat transfer parameters, oil quality parameters, and flow pattern parameters, and coordinating this with the acquisition of a comprehensive performance degradation index to evaluate the degradation state of insulating oil, multi-dimensional and heterogeneous test data can be uniformly transformed into a comprehensive performance degradation index. This solves the problem that traditional methods rely on single parameters such as acid value, viscosity, or moisture content, which cannot comprehensively reflect the combined impact of insulating oil degradation on equipment heat dissipation performance and flow reliability. The degree of insulating oil degradation can be characterized by a comprehensive index and compared with a preset threshold, making it convenient for testing or maintenance personnel to determine the timing of oil treatment, re-inspection, or replacement.

[0030] By adjusting the heating power, cooling medium flow rate, and oil pump speed according to the preset temperature and flow rate curves in the dynamic operating condition simulation step, and cooperating with the switching of the flow characteristic test branch and the heat transfer characteristic test branch at preset time intervals in the cyclic switching step, typical operating conditions such as transformer cold start, steady-state operation, load fluctuation, or overload can be simulated. This solves the problem that the test data has limited engineering reference value due to insufficient matching between laboratory constant temperature and constant current test conditions and actual dynamic operating conditions. It makes the test results closer to the degradation law of flow and heat transfer performance of insulating oil under actual service conditions, which facilitates equipment condition assessment and reliability prediction. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the overall structure of a test module for the flow heat transfer characteristics of insulating oil degradation in this invention.

[0032] Figure 2 This is a schematic diagram of the flow characteristic testing unit structure in this invention.

[0033] Figure 3 This is a schematic diagram of the heat transfer characteristic testing unit structure in this invention.

[0034] In the diagram: 1. High-speed camera equipment; 2. Temperature controller; 3. Electric heating belt; 4. Temperature bulb; 5. Flow characteristic measurement unit; 6. Oil inlet two; 7. Sampling port; 8. Oil pump; 9. Frequency converter; 10. Vortex flow meter; 11. Cooling jacket; 12. Oil outlet; 13. Oil inlet one; 14. Oil quality sensor; 15. Heat transfer characteristic measurement unit; 16. Pressure sensor one; 17. Ultrasonic flow meter; 18. Pressure sensor two; 19. Three-way valve assembly; 5-1. Differential pressure sensor one; 5-2. Differential pressure sensor two; 16. Pressure sensor one; 17. Ultrasonic flow meter; 18. Pressure sensor two; 15-1 Temperature sensor one; 15-2 Temperature sensor two; 15-3 Temperature sensor three; 15-4 Temperature sensor four; 15-5 Flow meter; 15-6 Cooling water; 15-7 Cooling water pump; 15-8 Shell-and-tube heat exchanger section; 15-9 Flow regulating valve; 15-10 Cooling water inlet; 15-11 Cooling water outlet. Detailed Implementation

[0035] To make the objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0036] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0037] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0038] Example 1 Reference Figure 1This is the first embodiment of the present invention, which provides a test module for the flow and heat transfer characteristics of deteriorated insulating oil. This module can perform flow characteristic testing, heat transfer characteristic testing, oil quality status monitoring, and flow pattern image acquisition of insulating oil within the same circulation system. It includes a circulating oil circuit unit, a flow characteristic testing unit 5, a heat transfer characteristic testing unit 15, a valve switching unit, a dynamic monitoring unit, and a data processing unit. The circulating oil circuit unit forms the main channel for the circulating flow of insulating oil. The flow characteristic testing unit 5 facilitates the acquisition of differential pressure and flow velocity data during the flow process. The heat transfer characteristic testing unit 15 facilitates the acquisition of heat transfer parameters between the insulating oil and the cooling medium. The valve switching unit facilitates switching between flow test mode, heat transfer test mode, collaborative test mode, and bypass circulation mode. The dynamic monitoring unit facilitates the simultaneous acquisition of oil quality parameters and flow pattern image parameters. The data processing unit facilitates the simultaneous processing and comprehensive evaluation of multi-source data.

[0039] Specifically, the circulating oil circuit unit includes an oil pump 8, a heating assembly, a cooling assembly, a circulating pipeline, and a bypass pipeline. The oil pump 8 is located on the circulating pipeline and drives the insulating oil to circulate within it. The heating assembly is connected to the circulating pipeline and heats the insulating oil within it; the cooling assembly is connected to the circulating pipeline for heat exchange and cools the insulating oil. By including the oil pump 8, heating assembly, and cooling assembly, the temperature and flow rate of the insulating oil can be easily adjusted during circulation, ensuring that the insulating oil reaches the preset test conditions.

[0040] The circulating oil circuit unit also includes an oil inlet 13, an oil inlet 2 6, a sampling port 7, an oil outlet 12, and a vortex flow meter 10; the oil inlet 13 and the oil inlet 2 6 are used to inject insulating oil, the oil outlet 12 is used to discharge insulating oil, the sampling port 7 is used to collect oil samples, and the vortex flow meter 10 is used to detect the flow rate of insulating oil in the circulating oil circuit.

[0041] Furthermore, the heating assembly may include an electric heating element 3 and a temperature sensor 4. The electric heating element 3 covers or is disposed on the outside of the circulation pipeline, and the temperature sensor 4 is used to detect the oil temperature or pipe wall temperature in the heating area. The cooling assembly may include a cooling sleeve 11, a cooling water pump 15-7, and a flow regulating valve 15-9. The cooling sleeve 11 is connected to the circulation pipeline for heat exchange, and the cooling water pump 15-7 and the flow regulating valve 15-9 are used to regulate the cooling water flow rate. By setting up the electric heating element 3, the temperature sensor 4, the cooling sleeve 11, the cooling water pump 15-7, and the flow regulating valve 15-9, it is convenient to achieve the raising, lowering, and stabilizing control of the oil temperature.

[0042] The valve switching unit may include a three-way valve group 19, a multi-way valve group, or multiple branch valves. The valve switching unit is connected between the circulating oil circuit unit, the flow characteristic testing unit 5, and the heat transfer characteristic testing unit 15. When the valve switching unit uses a three-way valve group 19, the insulating oil can be switched between the flow characteristic testing unit 5, the heat transfer characteristic testing unit 15, and the bypass pipeline in a time-sharing manner. When the valve switching unit uses a multi-way valve group or multiple branch valves, the insulating oil can simultaneously enter both the flow characteristic testing unit 5 and the heat transfer characteristic testing unit 15 to form a coordinated testing mode. By setting up the valve switching unit, it is convenient to switch between different test paths according to test requirements, avoiding the need to rebuild the oil circuit every time the test content is changed.

[0043] Furthermore, the circulating oil circuit unit also includes a frequency converter 9 and a temperature controller 2. The frequency converter 9 is electrically connected to the oil pump 8 and is used to adjust the speed of the oil pump 8; the temperature controller 2 is electrically connected to the heating component, the cooling component, and the oil temperature detection component, respectively, and is used to adjust the heating power and cooling capacity according to the oil temperature feedback. By setting up the frequency converter 9 and the temperature controller 2, it is convenient to perform closed-loop control of the flow rate and temperature of the insulating oil.

[0044] In this embodiment, the dynamic monitoring unit includes an oil quality detection component and an image acquisition component. The oil quality detection component can be an oil quality sensor 14, which is connected to the circulation pipeline and is used to detect oil quality parameters such as acid value, moisture content, and dielectric loss factor. The image acquisition component can be a high-speed camera device 1, which is positioned towards the measurement section of the flow characteristic testing unit 5 to acquire images of bubbles and flow patterns during the flow of insulating oil. By setting up the oil quality sensor 14 and the high-speed camera device 1, it is convenient to simultaneously obtain information on oil quality changes and flow pattern changes during the flow heat transfer test.

[0045] The data processing unit is communicatively connected to the differential pressure sensor, flow velocity detector, oil-side temperature detector, cooling-side temperature detector, cooling medium flow rate detector, oil quality detector, and image acquisition unit. The data processing unit receives data collected by each detector and performs time synchronization, normalization, and weighted fusion of flow parameters, heat transfer parameters, oil quality parameters, and flow pattern image parameters to calculate the comprehensive performance degradation index. Based on this comprehensive performance degradation index, the unit obtains the evaluation result of the insulating oil's degradation state.

[0046] Working Principle: During use, insulating oil is injected into the circulation pipeline through inlet 13 and / or inlet 6. The oil pump 8 is started, causing the insulating oil to circulate at low speed in the circulation oil circuit unit and expel residual gas from the pipeline. The temperature controller 2 controls the electric heating belt 3 and cooling components to reach the preset oil temperature; the frequency converter 9 adjusts the speed of the oil pump 8 to reach the preset flow rate. Subsequently, the test path is selected through a three-way valve group 19, a multi-way valve group, or multiple branch valves, allowing the insulating oil to enter the flow characteristic test unit 5, the heat transfer characteristic test unit 15, or both simultaneously, or bypass the pipeline for bypass circulation. The insulating oil is discharged or recovered through outlet 12, and the circulation flow rate is fed back through the vortex flow meter 10. During the test, the dynamic monitoring unit simultaneously collects oil quality parameters and flow images, and the data processing unit processes the multi-source data to obtain the evaluation results of the insulating oil's deterioration state.

[0047] In summary, by setting up a circulating oil circuit unit, a flow characteristic testing unit 5, a heat transfer characteristic testing unit 15, a valve switching unit, a dynamic monitoring unit, and a data processing unit for coordinated use, flow testing, heat transfer testing, oil quality monitoring, and flow pattern image acquisition of insulating oil during the same circulating system can be achieved. This solves the problem that existing testing devices have limited functionality and are difficult to obtain multi-source test data under the same oil sample and operating conditions.

[0048] Example 2 Reference Figure 1 and Figure 2 This is the second embodiment of the present invention. Unlike embodiment 1, this embodiment further provides a specific structure for the flow characteristic testing unit 5, which can realize the testing of pressure difference, flow velocity and flow resistance parameters of insulating oil under different oil channel geometry conditions. This is beneficial for simulating the influence of local contraction, expansion, narrow channels or rough walls in transformer oil channels on the flow resistance of insulating oil.

[0049] Specifically, the flow characteristic testing unit 5 includes a measuring pipe section, a differential pressure sensor, and a flow velocity detection device. For example... Figure 2 As shown, the corresponding measurement pipe section Figure 2 The test area is between differential pressure sensor 5-1 and differential pressure sensor 5-2. The inlet of the measuring pipe section is connected to the valve switching unit, and the outlet of the measuring pipe section is connected to the return oil side of the circulation pipeline, allowing insulating oil to enter the measuring pipe section and return to the circulation pipeline under the control of the valve switching unit. By setting up the measuring pipe section, a limited flow area for measuring differential pressure and flow velocity can be easily formed.

[0050] Furthermore, the measuring section includes a transparent pressure-resistant pipe section and an oil channel simulation plug detachably installed within the transparent pressure-resistant pipe section. The oil channel simulation plug has at least one of the following: a reduced diameter section, an expanded diameter section, a curved section, a narrow slit section, and a rough wall section. By setting up a transparent pressure-resistant pipe section, the image acquisition device can easily observe the flow state of the insulating oil from the outside; by setting up a detachable oil channel simulation plug, it is convenient to simulate the oil channel structure of different types of transformers.

[0051] The differential pressure sensor can be differential pressure sensor 5-1 or differential pressure sensor 5-2, which are respectively arranged at two pressure tapping positions or different range test positions in the measuring pipe section. The two pressure tapping ends of the differential pressure sensor are connected to the upstream and downstream pressure tapping positions of the measuring pipe section, respectively. Furthermore, the differential pressure sensor is connected across the upstream and downstream sides of the oil passage simulation module to measure the pressure drop of the insulating oil before and after passing through the oil passage simulation module. By setting up differential pressure sensors, it is convenient to obtain the differential pressure data generated when the insulating oil passes through different oil passage structures.

[0052] Furthermore, the flow velocity detection device can be an ultrasonic flow meter 17, which is installed at the measuring pipe section, or at the upstream or downstream straight pipe section of the oil passage simulation plug-in, to measure the cross-sectional average flow velocity of the insulating oil. Pressure sensor 16 and pressure sensor 2 18 can also be installed upstream and downstream of the measuring pipe section, respectively, to monitor the pressure status at the inlet and outlet sides of the flow characteristic test unit 5. By installing the ultrasonic flow meter 17, pressure sensor 16, and pressure sensor 2 18, synchronous data of differential pressure, pressure, and flow velocity can be easily obtained.

[0053] In one specific implementation, the flow parameters include the Reynolds number Re and the flow drag coefficient f. The Reynolds number Re can be calculated using the following formula: Re=ρ·v·D / μ Where ρ is the density of insulating oil, v is the flow velocity, D is the characteristic diameter of the measuring pipe section, and μ is the dynamic viscosity of insulating oil.

[0054] The flow resistance coefficient f can be calculated based on the geometric parameters of the measuring pipe section, the density of the insulating oil, the differential pressure data, and the flow velocity data. For example, for the friction loss test section, the flow resistance coefficient f can be calculated using the following formula: f = 2·ΔP·D / (ρ·L·v²) Where ΔP is the pressure difference between the upstream and downstream pressure tapping positions of the measuring pipe section, L is the pressure tapping interval, D is the characteristic diameter of the measuring pipe section, ρ is the density of the insulating oil, and v is the flow velocity.

[0055] For the local resistance test section, the local resistance coefficient ξ can also be used to represent it: ξ = 2·ΔP / (ρ·v²) Working Principle: During flow characteristic testing, the valve switching unit allows insulating oil to enter the measuring pipe section. After the insulating oil flows through the oil channel simulation module, the differential pressure sensor collects the pressure difference data between the upstream and downstream sides, the ultrasonic flow meter 17 collects the flow velocity data, and pressure sensors 16 and 18 collect the pressure data before and after the test section. The high-speed camera 1 captures flow images through the observation window. The data processing unit calculates the flow resistance coefficient based on the differential pressure data, flow velocity data, and geometric parameters of the measuring pipe section, and analyzes the impact of insulating oil degradation on flow resistance in conjunction with oil quality parameters.

[0056] In summary, by using a combination of measuring pipe sections, oil channel simulation plugs, differential pressure sensors, and flow velocity detection devices, the pressure drop, flow velocity, and resistance coefficient of insulating oil under different oil channel structure conditions can be obtained, solving the problem that existing technologies cannot quantitatively evaluate the impact of insulating oil degradation on flow resistance.

[0057] Example 3 Reference Figure 1 and Figure 3 This is the third embodiment of the present invention. Unlike embodiment 1 or embodiment 2, this embodiment further provides a specific structure of the heat transfer characteristic testing unit 15, which can realize the testing of heat transfer parameters during the heat exchange process between insulating oil and cooling medium, and solves the problem that it is difficult to quantitatively obtain the heat transfer coefficient and Nusselt number of insulating oil after deterioration in the prior art.

[0058] Specifically, the heat transfer characteristic testing unit 15 includes a heat exchange tube section, an oil-side temperature sensor, a cooling-side temperature sensor, and a cooling medium flow rate sensor. The heat exchange tube section has an oil-side channel for the insulating oil and a cooling-side channel for the cooling medium. The inlet of the oil-side channel is connected to the valve switching unit, and the outlet of the oil-side channel is connected to the return oil side of the circulation pipeline. By setting up the heat exchange tube section, it is convenient for the insulating oil and the cooling medium to exchange heat under relatively stable heat exchange boundary conditions.

[0059] Furthermore, the heat exchange tube section is a shell-and-tube heat exchange tube section 15-8, with the oil-side channel being the inner tube and the cooling-side channel being the outer heat exchange channel located outside the inner tube. The cooling medium is cooling water 15-6, and the cooling water pump 15-7 drives the cooling water 15-6 to circulate in the cooling water pipeline. The cooling water 15-6 enters the outer heat exchange channel through the cooling water inlet 15-10 and flows out through the cooling water outlet 15-11. By setting up the shell-and-tube heat exchange tube section 15-8, a heat transfer test area with a simple structure and a clearly defined heat exchange area can be easily formed.

[0060] The oil-side temperature detection components can include temperature sensor 15-1 and temperature sensor 15-2. Temperature sensor 15-1 is installed at the oil inlet of the inner tube, and temperature sensor 15-2 is installed at the oil outlet of the inner tube, used to collect the inlet and outlet temperatures of the insulating oil. The cooling-side temperature detection components can include temperature sensor 35-3 and temperature sensor 45-4. Temperature sensor 35-3 is installed at the cooling water inlet 15-10, and temperature sensor 45-4 is installed at the cooling water outlet 15-11, used to collect the inlet and outlet temperatures of the cooling water. The cooling medium flow detection component can be a flow meter 15-5, installed in the cooling water pipeline, used to collect the cooling water flow rate. By setting temperature sensors 15-1, 15-2, 15-3, 15-4, and flow meter 15-5, the temperature and flow data required for calculating heat transfer parameters can be easily obtained.

[0061] In one specific embodiment, the heat exchange capacity Q on the cooling water side can be calculated using the following formula: Q = ρw·Cw·qw·(Tw,out-Tw,in) Where ρw is the density of cooling water, Cw is the specific heat capacity of cooling water, qw is the volumetric flow rate of cooling water, Tw,in is the inlet temperature of cooling water, and Tw,out is the outlet temperature of cooling water.

[0062] In one specific implementation, when the shell-and-tube heat exchanger section 15-8 adopts a counter-current heat exchange method, the logarithmic mean temperature difference ΔTm between oil and water can be calculated using the following formula: ΔTm=[(To,in-Tw,out)-(To,out-Tw,in)] / ln[(To,in-Tw,out) / (To,out-Tw,in)] Where To,in is the oil inlet temperature, To,out is the oil outlet temperature, Tw,in is the cooling water inlet temperature, and Tw,out is the cooling water outlet temperature. In other embodiments, ΔTm can also be determined based on the specific flow direction relationship of the heat exchange tube section according to the oil-side inlet and outlet temperatures and the cooling-side inlet and outlet temperatures.

[0063] The convective heat transfer coefficient h can be calculated using the following formula: h=Q / (A·ΔTm) Where A is the heat exchange area.

[0064] The Nusselt number Nu can be calculated using the following formula: Nu=h·D / λ Where D is the characteristic diameter of the heat exchange tube section, and λ is the thermal conductivity of the insulating oil.

[0065] Working Principle: During heat transfer characteristic testing, the valve switching unit allows insulating oil to enter the inner tube of the shell-and-tube heat exchanger section 15-8, while cooling water enters the outer heat exchange channel. Temperature sensors 15-1 and 15-2 collect the oil-side inlet and outlet temperatures, respectively; temperature sensors 15-3 and 15-4 collect the cooling water-side inlet and outlet temperatures, respectively; and flow meter 15-5 collects the cooling water flow rate. The data processing unit calculates the heat transfer, heat transfer coefficient, and Nusselt number based on the cooling water flow rate, the cooling water inlet and outlet temperature difference, the oil-side temperature data, and the heat exchange area, and further analyzes the impact of insulating oil degradation on heat transfer performance.

[0066] In summary, by using the shell-and-tube heat exchanger section 15-8, temperature sensors 15-1 to 15-4, and flow meter 15-5 in combination, the heat transfer coefficient and Nusselt number of insulating oil during the deterioration process can be quantitatively obtained, solving the problem that existing technologies are unable to evaluate the changes in the heat transfer performance of insulating oil under dynamic oil sample conditions.

[0067] Example 4 Reference Figures 1 to 3 This is the fourth embodiment of the present invention. Unlike the previous embodiments, this embodiment further provides a dynamic operating condition control and multi-source information fusion processing method, which can realize the flow heat transfer performance test of insulating oil under cold start, steady-state operation, load fluctuation and overload conditions, and solve the problem of insufficient matching between existing laboratory test conditions and actual transformer operating conditions.

[0068] Specifically, temperature controller 2 is electrically connected to the heating component, cooling component, and oil temperature detection device, while frequency converter 9 is electrically connected to oil pump 8. Temperature controller 2 adjusts the heating power and cooling medium flow rate according to a preset temperature curve, and frequency converter 9 adjusts the speed of oil pump 8 according to a preset flow rate curve. By setting up temperature controller 2, heating component, cooling component, frequency converter 9, and oil pump 8, the oil temperature and flow rate can be easily adjusted, allowing the insulating oil to operate according to the preset operating condition curve.

[0069] Furthermore, the preset operating conditions may include at least one of the following: cold start condition, steady-state operation condition, load fluctuation condition, overload condition, and cooling recovery condition.

[0070] For example, in a cold start condition, the oil temperature can be raised from ambient temperature to the no-load operating temperature, and the flow rate can be gradually increased from a lower value to a set flow rate to simulate the process of a transformer transitioning from a shutdown state to an operating state. For instance, the oil temperature is linearly increased from approximately 20°C to 50°C at a rate of 0.5°C / min, and the flow rate is linearly increased from 0 m / s to 0.5 m / s at a rate of 0.1 m / s / min, with a simulation duration of 60 minutes.

[0071] Under steady-state operating conditions, the oil temperature can be maintained between 50℃ and 70℃, and the flow velocity can be maintained between 0.5m / s and 1.2m / s to simulate the rated load or near-rated load operating conditions of a transformer. Temperature fluctuations can be controlled within ±0.3℃, flow velocity fluctuations can be controlled within ±0.02m / s, and the simulation duration can be set according to research needs.

[0072] Under fluctuating load conditions, the oil temperature can change periodically according to a preset load curve, and the rate of change can be adjusted between 0.2℃ / min and 1.0℃ / min. The flow rate and oil temperature can be decoupled and controlled, or they can be controlled in conjunction with the load curve to simulate the daily load curve of the transformer.

[0073] Under overload conditions, the oil temperature can be rapidly increased to 90℃ to 120℃, with a heating rate of 2℃ / min. The flow rate can be simultaneously increased to 1.5m / s to 2.0m / s. The simulation duration can be set to 30min to 120min, followed by a simulation of the cooling and recovery process.

[0074] The temperature control model can employ PID control. The heating power Ph(t) can be calculated using the following formula: Ph(t)=Kp·eT(t)+Ki·∫eT(t)dt+Kd·deT(t) / dt Where eT(t) is the temperature deviation, that is, the difference between the set temperature and the measured temperature; Kp, Ki, and Kd are the proportional coefficient, integral coefficient, and derivative coefficient of the temperature PID control, respectively.

[0075] Under a simplified heat balance model, the cooling medium flow rate Qw(t) can be estimated using the following formula: Qw(t)=mo·Co·(dTo / dt) / [ρw·Cw·(Tw,out-Tw,in)] Where mo is the total mass of the oil circuit, Co is the specific heat capacity of the insulating oil, To is the oil temperature, ρw is the density of the cooling water, Cw is the specific heat capacity of the cooling water, Tw,in is the inlet temperature of the cooling water, and Tw,out is the outlet temperature of the cooling water.

[0076] The oil pump speed n(t) can be adjusted by the frequency converter 9 according to the flow velocity deviation, for example, by calculating the following formula: n(t) = nbase + Kv·eV(t) Where n(t) is the pump speed at time t, eV(t) is the speed deviation, i.e., the difference between the set flow rate and the measured flow rate, nbase is the base speed to overcome pipeline resistance, and Kv is the flow rate adjustment coefficient. In other embodiments, the pump speed n(t) can also be adjusted using a PID controller.

[0077] Furthermore, all sensor signals are connected to the data processing unit or a multi-channel high-speed data acquisition card. The sampling frequency can be uniformly set to 100Hz, and a unified clock synchronization triggering method is used to align temperature, pressure, differential pressure, flow rate, oil quality parameters, and image parameters on the same time axis. The data processing unit filters and denoises the raw data, removes outliers, and extracts feature parameters. The extracted flow resistance coefficient, Nusselt number, acid value, moisture content, and bubble feature parameters are normalized by dividing by the corresponding reference value to eliminate the influence of dimensional differences on the fusion effect. Among these, wavelet threshold denoising algorithm can be used for filtering and outlier removal; the 3σ criterion can be used for outlier removal.

[0078] The data processing unit extracts flow characteristics, heat transfer characteristics, oil quality characteristics, and visual characteristics from the preprocessed data. Flow characteristics may include pressure drop ΔP, flow velocity v, Reynolds number Re, and drag coefficient f; heat transfer characteristics may include inlet and outlet temperature difference ΔT, heat flow rate Q, heat transfer coefficient h, and Nusselt number Nu; oil quality characteristics may include acid number AV, moisture content W, and medium loss factor tanδ; visual characteristics may include bubble number, bubble size distribution, bubble area ratio, and flow regime type.

[0079] In one specific implementation, the overall performance degradation index F(t) can be calculated using the following formula: F(t)=α·f(t) / f0+β·Nu0 / Nu(t)+γ·AV(t) / AV0+δ·W(t) / W0+ε·B(t) / B0 Wherein, F(t) is the comprehensive performance degradation index at time t; f(t) is the flow resistance coefficient at time t; f0 is the baseline flow resistance coefficient; Nu(t) is the Nusselt number at time t; Nu0 is the baseline Nusselt number; AV(t) is the acid value at time t; AV0 is the baseline acid value; W(t) is the moisture content at time t; W0 is the baseline moisture content; B(t) is the bubble characteristic parameter at time t; B0 is the baseline bubble characteristic parameter; α, β, γ, δ, and ε are weighting coefficients, and satisfy α+β+γ+δ+ε=1. The baseline values ​​f0, Nu0, AV0, W0, and B0 can be obtained by testing fresh, undegraded insulating oil under the same operating conditions using the same test module before the test begins, or they can be set according to the transformer safety operation standards.

[0080] Wherein, B(t) can be the area ratio of the bubbles in the observation window, or it can be determined based on the number of bubbles, the distribution of bubble size, or the bubble migration speed. When F(t) increases, it indicates that the overall performance of the insulating oil is deteriorating more severely; when F(t) is greater than the preset threshold, the data processing unit outputs an early warning result to indicate that oil treatment, replacement, or offline re-inspection is required.

[0081] Working principle: During dynamic operating condition testing, temperature controller 2 adjusts the heating and cooling components according to the preset temperature curve, and frequency converter 9 adjusts the speed of oil pump 8 according to the preset flow rate curve, so that the insulating oil is subjected to test conditions such as cold start, steady-state operation, load fluctuation, or overload. During the test, the data processing unit performs time synchronization and normalization processing on flow parameters, heat transfer parameters, oil quality parameters, and flow pattern image parameters, and evaluates the deterioration state of the insulating oil according to the comprehensive performance degradation index F(t).

[0082] In summary, by setting up temperature controller 2, frequency converter 9, oil pump 8, heating components, cooling components and data processing unit in combination, typical operating conditions of transformers can be simulated, and the flow, heat transfer, oil quality and flow state parameters during the deterioration process of insulating oil can be evaluated in a fusion. This solves the problem that existing technologies are unable to comprehensively evaluate the degradation of the flow and heat transfer performance of insulating oil under dynamic operating conditions.

[0083] Example 5 Reference Figures 1 to 3 This is the fifth embodiment of the present invention, which provides a method for testing the flow and heat transfer characteristics of insulating oil during degradation. This method enables the simultaneous acquisition and comprehensive evaluation of flow parameters, heat transfer parameters, oil quality parameters, and flow pattern parameters of the insulating oil during the degradation process. This method can be performed using the insulating oil degradation flow and heat transfer characteristic testing module from any of Embodiments 1 to 4.

[0084] Specifically, the method includes the following steps: Step 1: System Initialization. Insulating oil is injected into the circulating oil circuit unit through the inlet. Oil pump 8 is started to circulate the insulating oil at a low speed to remove residual gas from the circulation pipeline. Simultaneously, the system pressure is monitored using pressure sensor 16, pressure sensor 18, or a differential pressure sensor to confirm that the circulating oil circuit unit is in a sealed state. In one embodiment, relevant valves can be closed and pressure maintained for 30 minutes. If there is no significant pressure drop, the system's sealing performance is confirmed to meet the test requirements.

[0085] Step 2: Set initial operating conditions. Connect the power supply and start the data processing unit, temperature controller 2, and frequency converter 9. Adjust the speed of oil pump 8 through frequency converter 9 to make the flow rate of insulating oil in the circulating oil circuit reach the preset value; start the heating component to raise the oil temperature to the preset initial temperature through temperature bulb 4 and temperature controller 2; start the cooling component to allow cooling water to enter the cooling jacket 11 or the jacket-type heat exchange tube section 15-8, thereby achieving stable oil temperature control.

[0086] Step 3: Test mode selection and data acquisition. Select the flow test mode, heat transfer test mode, collaborative test mode, or bypass circulation mode through the valve switching unit.

[0087] In the flow test mode, the valve switching unit allows the insulating oil to enter the flow characteristic test unit 5. The differential pressure sensor collects the differential pressure data between the upstream and downstream pressure taps of the measuring pipe section, the ultrasonic flow meter 17 collects the flow velocity data, the pressure sensor 16 and the pressure sensor 18 collect the pressure data, and the high-speed camera 1 collects the flow image at the observation window.

[0088] In the heat transfer test mode, the valve switching unit allows insulating oil to enter the heat transfer characteristic test unit 15. Temperature sensor 15-1 and temperature sensor 25-2 collect the oil side inlet and outlet temperatures, temperature sensor 35-3 and temperature sensor 45-4 collect the cooling water side inlet and outlet temperatures, and flow meter 15-5 collects the cooling water flow rate. The data processing unit calculates the heat exchange, heat transfer coefficient, and Nusselt number based on the above data.

[0089] In the collaborative testing mode, the valve switching unit allows the insulating oil to simultaneously enter the flow characteristic test unit 5 and the heat transfer characteristic test unit 15, and synchronously collects differential pressure data, flow rate data, oil side temperature data, cooling side temperature data, cooling medium flow rate data, oil quality parameters and flow pattern image parameters.

[0090] In bypass circulation mode, the valve switching unit allows the insulating oil to flow back to the circulation pipeline via the bypass pipeline for venting, temperature stabilization, stable operating conditions, or circulation maintenance during test intervals.

[0091] Step four: Multi-source information synchronization and preprocessing. The data processing unit receives data collected by the differential pressure sensor, ultrasonic flow meter 17, temperature sensors 15-1 to 15-4, flow meter 15-5, oil quality sensor 14, and high-speed camera 1, and performs time synchronization on the data from different sources. The data processing unit performs wavelet threshold denoising and 3σ outlier removal on the raw data, and then extracts flow characteristics, heat transfer characteristics, oil quality characteristics, and visual characteristics from the preprocessed data.

[0092] Step 5, parameter calculation. The data processing unit calculates the drag coefficient based on the differential pressure data, flow velocity data, geometric parameters of the measuring pipe section, and insulating oil density; it calculates the heat transfer, heat transfer coefficient, and Nusselt number based on the cooling water flow rate, oil side temperature data, cooling side temperature data, and heat transfer area; it obtains the acid value, moisture content, and dielectric loss factor based on the data collected by the oil quality sensor 14; and it obtains the number of bubbles, bubble size distribution, bubble area ratio, and flow pattern type based on the images collected by the high-speed camera device 1.

[0093] Step Six, Comprehensive Evaluation. The data processing unit calculates the comprehensive performance degradation index F(t) according to the following formula: F(t)=α·f(t) / f0+β·Nu0 / Nu(t)+γ·AV(t) / AV0+δ·W(t) / W0+ε·B(t) / B0 Wherein, F(t) is the comprehensive performance degradation index at time t; f(t) is the flow resistance coefficient at time t; f0 is the baseline flow resistance coefficient; Nu(t) is the Nusselt number at time t; Nu0 is the baseline Nusselt number; AV(t) is the acid value at time t; AV0 is the baseline acid value; W(t) is the moisture content at time t; W0 is the baseline moisture content; B(t) is the bubble characteristic parameter at time t; B0 is the baseline bubble characteristic parameter; α, β, γ, δ, and ε are weighting coefficients, and α+β+γ+δ+ε=1. The baseline values ​​f0, Nu0, AV0, W0, and B0 can be obtained by testing fresh, undegraded insulating oil under the same operating conditions using the same test module before the start of the test.

[0094] Step 7, Status Assessment. When the comprehensive performance degradation index F(t) exceeds the preset threshold, the data processing unit outputs the insulation oil degradation status evaluation result or an early warning. The preset threshold can be set according to the transformer's safe operation requirements, for example, 1.5. When F(t) is greater than the preset threshold, it indicates that oil analysis, oil treatment, replacement, or offline re-inspection is required.

[0095] Furthermore, during long-term degradation testing, the flow characteristic test branch and the heat transfer characteristic test branch can be switched at preset time intervals. For example, every 24 hours of operation, the system automatically performs a simplified flow characteristic test and a heat transfer characteristic test, recording the drag coefficient, Nusselt number, and oil quality parameters at the corresponding time points; every 168 hours of operation, insulating oil samples are collected through sampling port 7 for offline acid value, kinematic viscosity, or Fourier transform infrared spectroscopy analysis for comparison with online data.

[0096] Working principle: This method first circulates the insulating oil in the circulating oil circuit to reach the preset temperature and flow rate, and then selects different test paths through the valve switching unit; during the flow test, the pressure difference and flow rate are obtained, and during the heat transfer test, the oil side and cooling side temperatures and cooling medium flow rate are obtained. During the entire test, oil quality parameters and flow pattern image parameters are obtained simultaneously; finally, the data processing unit performs fusion calculation on the multi-source data, and judges the deterioration state of the insulating oil based on the comprehensive performance degradation index.

[0097] In summary, by combining system initialization, initial operating condition settings, test mode selection, multi-source information synchronization and preprocessing, parameter calculation, and comprehensive evaluation steps, flow parameters, heat transfer parameters, oil quality parameters, and flow pattern parameters during the degradation process of insulating oil can be obtained under the same oil sample, the same time axis, and controllable dynamic conditions. This solves the problem of the disconnect between flow testing, heat transfer testing, and oil quality monitoring in existing testing methods, and facilitates the study and evaluation of the degradation law of flow and heat transfer performance during the degradation process of insulating oil.

Claims

1. A test module for the flow and heat transfer characteristics of deteriorated insulating oil, characterized in that, It includes a circulating oil circuit unit, a flow characteristic testing unit, a heat transfer characteristic testing unit, a valve switching unit, a dynamic monitoring unit, and a data processing unit; The circulating oil circuit unit includes an oil pump, a heating component, a cooling component, a circulating pipeline, and a bypass pipeline. The oil pump is used to drive the insulating oil to circulate in the circulating pipeline, and the heating component and the cooling component are used to regulate the temperature of the insulating oil. The flow characteristic testing unit includes a measuring pipe section, a differential pressure sensor, and a flow velocity detection device. The measuring pipe section is selectively connected to the circulation pipeline through the valve switching unit to obtain differential pressure data and flow velocity data during the flow of insulating oil. The heat transfer characteristic testing unit includes a heat exchange tube section, an oil-side temperature detection device, a cooling-side temperature detection device, and a cooling medium flow detection device. The heat exchange tube section is selectively connected to the circulation pipeline through the valve switching unit to obtain heat transfer data between the insulating oil and the cooling medium. The valve switching unit is connected between the circulating oil circuit unit, the flow characteristic test unit, the heat transfer characteristic test unit, and the bypass pipeline, and is used to switch between flow test mode, heat transfer test mode, cooperative test mode, or bypass circulation mode. The dynamic monitoring unit includes an oil quality detection device connected to the circulation pipeline, and an image acquisition device positioned towards the measurement pipe section; The data processing unit is communicatively connected to each detection element; the data processing unit is configured to: perform time synchronization, normalization and weighted fusion on the collected flow parameters, heat transfer parameters, oil quality parameters and flow state image parameters, calculate the comprehensive performance degradation index, and obtain the evaluation result of the insulation oil degradation state based on the comprehensive performance degradation index.

2. The insulating oil deterioration flow heat transfer characteristic testing module according to claim 1, characterized in that, The measuring pipe section includes a transparent pressure-resistant pipe section and an oil passage simulation plug detachably disposed within the transparent pressure-resistant pipe section. The oil passage simulation plug has at least one of a reduced diameter section, an expanded diameter section, a curved section, a narrow slit section, and a rough wall section.

3. The insulating oil deterioration flow heat transfer characteristic testing module according to claim 2, characterized in that, The differential pressure sensor is connected across the upstream and downstream sides of the oil passage simulation module, and the flow velocity detection device is located at the upstream or downstream straight pipe section of the oil passage simulation module.

4. The insulating oil deterioration flow heat transfer characteristic testing module according to claim 1, characterized in that, The valve switching unit includes a first branch valve located at the inlet of the flow characteristic test unit, a second branch valve located at the inlet of the heat transfer characteristic test unit, and a bypass valve located at the inlet of the bypass pipeline. The first branch valve, the second branch valve, and the bypass valve are configured to be able to open individually or in combination, so that insulating oil enters the flow characteristic test unit, enters the heat transfer characteristic test unit, enters both the flow characteristic test unit and the heat transfer characteristic test unit simultaneously, or flows back to the circulation pipeline via the bypass pipeline.

5. The insulating oil deterioration flow heat transfer characteristic testing module according to claim 1, characterized in that, The heat exchange tube section has an oil-side channel for insulating oil to pass through and a cooling-side channel for cooling medium to pass through; the heat exchange tube section is a shell-and-tube type heat exchange tube section, the oil-side channel is an inner tube, the cooling-side channel is an outer heat exchange channel located outside the inner tube, and the cooling medium is cooling water.

6. The insulating oil deterioration flow heat transfer characteristic testing module according to claim 5, characterized in that, The oil-side temperature sensors are respectively installed at the oil inlet and oil outlet of the inner tube, the cooling-side temperature sensors are respectively installed at the cooling water inlet and cooling water outlet of the outer heat exchange channel, and the cooling medium flow sensor is installed in the cooling water pipeline connected to the outer heat exchange channel.

7. The insulating oil deterioration flow heat transfer characteristic testing module according to claim 1, characterized in that, The circulating oil circuit unit also includes a frequency converter and a temperature controller. The frequency converter is electrically connected to the oil pump, and the temperature controller is electrically connected to the heating component, the cooling component, and the oil temperature detection element installed in the circulating pipeline.

8. The insulating oil deterioration flow heat transfer characteristic testing module according to claim 7, characterized in that, The cooling assembly includes a cooling sleeve, a cooling water pump, and a flow regulating valve. The cooling sleeve is fitted onto the outside of the circulation pipeline, and the cooling water pump, the flow regulating valve, and the cooling sleeve are connected through the cooling water circulation pipeline.

9. The insulating oil deterioration flow heat transfer characteristic testing module according to claim 1, characterized in that, The oil quality testing device includes at least two of the following: acid value testing device, moisture testing device, and dielectric loss testing device; the image acquisition device is a high-speed camera device, and the measuring tube section is provided with an observation window opposite to the high-speed camera device.

10. A method for testing the flow and heat transfer characteristics of deteriorated insulating oil, characterized in that, The test is conducted using an insulating oil circulation testing system, which includes a circulation oil circuit, a flow characteristic testing branch selectively connected to the circulation oil circuit, a heat transfer characteristic testing branch selectively connected to the circulation oil circuit, a bypass pipeline, an oil quality detection device, and an image acquisition device; the method includes: The insulating oil is circulated in the circulating oil circuit and adjusted to the preset test conditions; The insulating oil can be selectively allowed to enter the flow characteristic test branch, the heat transfer characteristic test branch, or both the flow characteristic test branch and the heat transfer characteristic test branch, or it can be returned to the circulating oil circuit via the bypass pipeline. Collect pressure difference data and flow velocity data in the flow characteristic test branch, and obtain flow parameters based on the pressure difference data and the flow velocity data; Collect oil-side temperature data, cooling-side temperature data, and cooling medium flow rate data in the heat transfer characteristic test branch, and obtain heat transfer parameters based on the oil-side temperature data, the cooling-side temperature data, and the cooling medium flow rate data; During the test, the oil quality parameters of the insulating oil are collected through the oil quality detection device, and the flow image of the insulating oil is collected through the image acquisition device. The flow parameters, heat transfer parameters, oil quality parameters, and flow image parameters obtained from the flow image are time-synchronized and normalized, and then weighted and fused according to preset weights to obtain a comprehensive performance degradation index. The evaluation results of the insulation oil's deterioration status are obtained based on the comprehensive performance degradation index.

11. The method for testing the flow and heat transfer characteristics of deteriorated insulating oil according to claim 10, characterized in that, The overall performance degradation index is obtained by calculation using the following formula: F(t)=α·Ff(t)+β·FNu(t)+γ·FAV(t)+δ·FW(t)+ε·FB(t); Wherein, F(t) is the comprehensive performance degradation index, Ff(t) is the normalized flow resistance index, FNu(t) is the normalized heat transfer attenuation index, FAV(t) is the normalized acid value index, FW(t) is the normalized moisture index, FB(t) is the normalized bubble characteristic index, and α, β, γ, δ, and ε are weighting coefficients, and α+β+γ+δ+ε=1; the heat transfer attenuation index is determined based on the ratio between the Nusselt number or the reference Nusselt number and the real-time Nusselt number.

12. The method for testing the deterioration flow heat transfer characteristics of insulating oil according to claim 10, characterized in that, Adjusting to the preset test conditions includes: adjusting the heating power and cooling medium flow rate according to the preset temperature curve, and adjusting the oil pump speed according to the preset flow rate curve; the preset temperature curve and the preset flow rate curve are configured to simulate the cold start condition, steady-state operation condition, load fluctuation condition or overload condition of the transformer.

13. The method for testing the deterioration flow heat transfer characteristics of insulating oil according to claim 10, characterized in that, The flow parameters include a drag coefficient, which is calculated based on the geometric parameters of the measuring pipe section, the density of the insulating oil, the differential pressure data, and the flow velocity data; the heat transfer parameters include the Nusselt number, which is calculated based on the cooling medium flow rate, the oil side temperature data, the cooling side temperature data, and the heat exchange area.

14. The method for testing the flow and heat transfer characteristics of deteriorated insulating oil according to claim 11, characterized in that, The bubble characteristic index is determined based on at least one of the following: bubble number, bubble size distribution, bubble area ratio, and bubble migration speed.

15. The method for testing the flow and heat transfer characteristics of deteriorated insulating oil according to claim 10, characterized in that, During the test, the flow characteristic test branch and the heat transfer characteristic test branch are switched at preset time intervals, and the flow parameters, heat transfer parameters and oil quality parameters at the corresponding time points are recorded respectively.

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