Transformer safety assessment method and system based on variable frequency loss test

Abstract

The invention discloses a transformer safety assessment method and system based on a variable frequency loss test, and the method comprises the steps: applying test voltages of different frequencies to a target transformer, and collecting the load loss data, generated by the test voltages of different frequencies, of the target transformer; establishing a loss-frequency characteristic curve relation, analyzing the deviation from an early-stage curve, and carrying out turn-to-turn short circuit analysis and winding fault analysis; introducing an infrared thermal imaging method, and combining turn-to-turn short circuit analysis and winding fault analysis of the transformer to carry out fault positioning and fault judgment on a target transformer; and constructing a transformer safety level scoring model, and performing safety evaluation on the target transformer based on the transformer safety level scoring model. By analyzing the load loss change of the transformer under different frequencies, the working state of the transformer is accurately evaluated, whether faults such as turn-to-turn short circuit exist in the transformer or not is judged, and the effects of improving the fault detection capability and simplifying the test process can be achieved.

Description

Technical Field

[0001] The present invention belongs to the field of transformer testing, and in particular relates to a transformer safety assessment method and system based on variable frequency loss testing. Background Art

[0002] Transformer safety assessment is a crucial method for ensuring safe equipment operation. The primary cause of transformer failure is interturn short circuits. These are primarily detected through DC resistance and load loss tests. While DC resistance testing can detect severe defects, it is not very sensitive. Load loss testing is typically performed at a fixed frequency and can also be insensitive. However, loss values at multiple frequencies may reveal potential problems, particularly for interturn short circuits. Summary of the Invention

[0003] Purpose of the invention: In order to overcome the deficiencies in the prior art, a transformer safety assessment method and system based on variable frequency loss testing is provided. By analyzing the changes in the transformer's load loss at different frequencies, the working status of the transformer can be accurately assessed, and then it can be determined whether the transformer has faults such as inter-turn short circuits, thereby improving fault detection capabilities and simplifying the testing process.

[0004] Technical solution: To achieve the above objectives, the present invention provides a variable frequency transformer safety assessment method based on loss testing, comprising the following steps:

[0005] S1: applying test voltages of different frequencies to the target transformer and collecting load loss data of the target transformer generated by the test voltages of different frequencies;

[0006] S2: Using a finite element simulation algorithm and combined with the load loss data of the target transformer, a loss-frequency characteristic mathematical curve is established to analyze the curve deviation. Based on the analysis results, turn-to-turn short-circuit analysis and winding fault analysis are performed on the target transformer.

[0007] S3: Introducing infrared thermal imaging, combined with transformer turn-to-turn short circuit analysis and winding fault analysis, to locate and determine the fault of the target transformer;

[0008] S4: Based on the fault location and fault determination of the target transformer, a transformer safety level scoring model is constructed, and the safety evaluation of the target transformer is performed based on the transformer safety level scoring model.

[0009] Furthermore, the step S1 specifically includes:

[0010] A1: Calibrate the transformer that needs to be tested for loss as the target transformer, and at the same time identify the electrical equipment connected to the target transformer and calibrate it as the target electrical equipment;

[0011] A2: Connect the target transformer to the target electrical equipment to build the target transformer system and preset two test voltage frequencies: 50 Hz and 200 Hz. The 50 Hz test voltage represents the test voltage at the normal operating frequency, while the 200 Hz test voltage represents the test voltage at the double frequency condition.

[0012] A3: Apply a 50Hz test voltage to the target transformer, preset a thermal stabilization time, and convert the test voltage in the target transformer to a 200Hz test voltage after the thermal stabilization time;

[0013] A4: Perform load tests on the target transformer system while applying a 50 Hz test voltage and a 200 Hz test voltage, and ensure that other operating conditions of the target transformer system remain consistent during the tests.

[0014] A5: Perform a load test on the target transformer system and calculate the power loss data of the target transformer at a test voltage of 50 Hz and a test voltage of 200 Hz, thereby obtaining the load loss data of the target transformer at a test voltage of 50 Hz and a test voltage of 200 Hz.

[0015] Furthermore, other operating conditions of the target transformer system in step A4 include the operating temperature, wiring type and rated current of the target transformer.

[0016] Furthermore, the step S2 specifically includes:

[0017] B1: Obtain the structural parameters of the target transformer in the target transformer system, and construct a finite element model of the target transformer based on the structural parameters of the target transformer, and calibrate it as the target finite element model;

[0018] The target finite element model is a three-dimensional model of the target transformer. The material properties of the target transformer are set in the three-dimensional model, and the load loss data of the target transformer under the test voltage of 50Hz and 200Hz are matched.

[0019] B2: Run the target finite element model and derive the load loss curves at test voltages from 50 Hz to 300 Hz, which are calibrated as loss-frequency characteristic curves.

[0020] B3: Compare the current loss-frequency characteristic curve with the previous loss-frequency characteristic curve and calculate the Pearson correlation coefficient. If the correlation coefficient is less than the preset value, it is determined that the target transformer has an inter-turn short circuit;

[0021] At the same time, the same-frequency load loss ratio is calculated and the same-frequency maximum loss ratio is preset. If the same-frequency load loss ratio is greater than the same-frequency maximum loss ratio, it is determined that the target transformer has a winding fault.

[0022] Furthermore, the step S3 specifically includes:

[0023] C1: During the target transformer system test, infrared thermal imaging data is collected at all locations of the target transformer using an infrared thermal imager to obtain infrared thermal imaging data at different locations of the target transformer.

[0024] C2: Perform Gaussian filtering to reduce noise on the infrared thermal imaging data at different locations of the target transformer, and use the threshold segmentation method to divide the high-temperature areas at different locations of the target transformer to obtain infrared thermal imaging data of the high-temperature areas of the target transformer;

[0025] C3: Compare the infrared thermal imaging data of the target transformer's high-temperature area at different frequencies to obtain temperature difference data at different locations. Build a temperature difference data sorting table, preset dangerous temperature difference data, analyze the temperature difference data sorting table, and mark the target transformer location with temperature difference data greater than the dangerous temperature difference data as the fault location to be analyzed.

[0026] C4: Based on the fault location to be analyzed, fault location and fault determination are performed on the target transformer.

[0027] Furthermore, in step C4, when a turn-to-turn short circuit exists in the target transformer, the temperature rise rate ratio of the fault position to be analyzed at different frequencies is calculated for the fault position to be analyzed, and a standard temperature rise rate ratio is preset. If the temperature rise rate ratio of the fault position to be analyzed is greater than the standard temperature rise rate ratio, the corresponding fault position to be analyzed is diagnosed as a turn-to-turn short circuit position.

[0028] Furthermore, in step C4, when a winding fault occurs in the target transformer, the nature of the winding fault is determined for the transformer in combination with the fault location to be analyzed, specifically including:

[0029] Analyze all fault locations to be analyzed, calculate the distances between different fault locations to be analyzed, and determine the standard distance between the fault locations to be analyzed;

[0030] If the distance between the fault locations to be analyzed is not greater than the standard distance and the proportion is greater than the preset value, it is determined that the overall temperature distribution of the target transformer is uniform and that a winding grounding fault exists in the target transformer;

[0031] The target transformer with a winding grounding fault is calibrated as a winding grounding fault transformer. An insulation resistance test is performed on the possible fault location to be analyzed on the winding grounding fault transformer, and a standard insulation resistance value is preset. The fault location to be analyzed with an insulation resistance less than the standard insulation resistance value is demarcated as a winding grounding fault location.

[0032] Calculate the full-load loss growth rate of the target transformer at different frequencies. If the full-load loss growth rate at 200 Hz remains within the standard threshold and the full-load loss growth rate at 50 Hz is greater than the standard threshold, it is determined that the target transformer has an abnormal winding turns fault.

[0033] Furthermore, the step S4 specifically includes:

[0034] D1: Determine the transformer safety rating model indicators, where the transformer safety rating model indicators include inter-turn short circuit, winding grounding fault and abnormal winding turns fault of the target transformer;

[0035] D2: Introducing a big data network, the network retrieves the hazard states of the transformer when it is affected by inter-turn short circuit, winding ground fault, and abnormal winding turns fault. A historical benefit impact analysis is performed on different hazard states to obtain a historical benefit impact ranking table.

[0036] D3: Based on the historical benefit impact ranking table, dynamically assign weights to different transformer safety rating model indicators, and determine the deduction points when generating different transformer safety rating model indicators based on the dynamic weights of the indicators;

[0037] D4: Based on the deduction scores when generating indicators of different transformer safety level scoring models, set the target transformer safety level scoring model, where the deduction scores are positively correlated with the dynamic weights, and the full score is equal to 100 points;

[0038] D5: Determine the safety level of the target transformer under different total scores, and perform safety scoring on the target transformer in combination with the target transformer safety level scoring model.

[0039] The present invention also provides a frequency converter safety assessment system for loss testing, comprising:

[0040] A load loss acquisition module, configured to apply test voltages of different frequencies to a target transformer and acquire load loss data of the target transformer generated by the test voltages of different frequencies;

[0041] The fault analysis module is used to establish a loss-frequency characteristic mathematical curve through finite element simulation algorithm and combined with the load loss data of the target transformer to perform curve deviation analysis. Based on the analysis results, it also performs turn-to-turn short circuit analysis and winding fault analysis on the target transformer.

[0042] The fault determination and location module uses infrared thermal imaging combined with transformer turn-to-turn short-circuit analysis and winding fault analysis to locate and determine the fault of the target transformer.

[0043] The safety evaluation module is used to construct a transformer safety level scoring model and perform safety evaluation on the target transformer based on the transformer safety level scoring model.

[0044] The method of the present invention is suitable for fault diagnosis and performance testing of transformers, especially for evaluating the working performance and safety of transformers under variable frequency conditions. Through variable frequency testing, especially analyzing the loss changes under different frequencies, various potential faults and design problems of transformer windings can be effectively detected. Under high frequency conditions, the impact of skin effect and frequency changes on losses will make some hidden faults more prominent, including inter-turn short circuits, ground faults, winding design defects, insulation damage and other problems. Therefore, variable frequency loss testing can not only reveal the normal performance of the transformer, but also diagnose potential faults in advance, helping engineers to carry out timely maintenance and optimization.

[0045] Beneficial Effects: Compared with the prior art, the present invention collects load loss data of the target transformer under test voltages of different frequencies, and combines it with a finite element simulation algorithm to perform turn-to-turn short-circuit analysis and winding fault analysis on the target transformer, thereby locating the fault location and fault state of the target transformer. Finally, a transformer safety level scoring model is constructed for safety evaluation of the target transformer. The present invention can provide a variable frequency loss test method that accurately assesses the operating state of the transformer by analyzing the changes in the load loss of the transformer at different frequencies, and then determines whether the transformer has faults such as turn-to-turn short-circuit. This can improve fault detection capabilities and simplify the testing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is a flow chart of the method of the present invention;

[0047] Figure 2 A flow chart of a method for locating and determining faults in a transformer;

[0048] Figure 3 This is the wiring diagram for the high voltage winding to low voltage load experiment;

[0049] Figure 4 This is the wiring diagram for the medium voltage winding to low voltage load experiment;

[0050] Figure 5 This is the wiring diagram for the high voltage winding to medium voltage load experiment. DETAILED DESCRIPTION

[0051] The present invention is further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, modifications of various equivalent forms of the present invention made by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0052] Example 1:

[0053] like Figure 1 As shown, this embodiment provides a variable frequency transformer safety assessment method based on loss testing, comprising the following steps:

[0054] S1: applying test voltages of different frequencies to the target transformer and collecting load loss data of the target transformer generated by the test voltages of different frequencies;

[0055] In this embodiment, step S1 specifically includes:

[0056] A1: Calibrate the transformer that needs to be tested for loss as the target transformer, and at the same time identify the electrical equipment connected to the target transformer and calibrate it as the target electrical equipment;

[0057] A2: Connect the target transformer to the target electrical equipment to build the target transformer system and preset two test voltage frequencies: 50 Hz and 200 Hz. The 50 Hz test voltage represents the test voltage at the normal operating frequency, while the 200 Hz test voltage represents the test voltage at the double frequency condition.

[0058] A3: Apply a 50Hz test voltage to the target transformer, preset a thermal stabilization time, and convert the test voltage in the target transformer to a 200Hz test voltage after the thermal stabilization time;

[0059] Before applying high-frequency voltage, it is necessary to apply normal frequency voltage for thermal stabilization to prevent high-frequency voltage from impacting the transformer and causing damage. The 200Hz frequency multiplication test can compensate for the voltage drop caused by high-frequency eddy current loss.

[0060] A4: Perform load tests on the target transformer system while applying a 50Hz test voltage and a 200Hz test voltage. Ensure that other operating conditions of the target transformer system remain consistent during the tests to eliminate the impact of non-frequency change factors on the loss test. Other operating conditions of the target transformer system include the operating temperature, wiring type, and rated current of the target transformer.

[0061] A5: Perform a load test on the target transformer system and calculate the power loss data of the target transformer at a test voltage of 50 Hz and a test voltage of 200 Hz, thereby obtaining the load loss data of the target transformer at a test voltage of 50 Hz and a test voltage of 200 Hz.

[0062] S2: Using a finite element simulation algorithm and combined with the load loss data of the target transformer, a loss-frequency characteristic mathematical curve is established to analyze the curve deviation. Based on the analysis results, turn-to-turn short-circuit analysis and winding fault analysis are performed on the target transformer.

[0063] In this embodiment, step S2 specifically includes:

[0064] B1: Obtain the structural parameters of the target transformer in the target transformer system, and construct a finite element model of the target transformer based on the structural parameters of the target transformer, and calibrate it as the target finite element model;

[0065] The target finite element model is a three-dimensional model of the target transformer. The material properties of the target transformer are set in the three-dimensional model, and the load loss data of the target transformer under the test voltage of 50Hz and 200Hz are matched.

[0066] B2: Run the target finite element model and derive the load loss curves at test voltages from 50 Hz to 300 Hz, which are calibrated as loss-frequency characteristic curves.

[0067] B3: Compare the current loss-frequency characteristic curve with the previous curve and calculate the Pearson correlation coefficient between the curves. If the coefficient is less than the preset value, it is determined that the target transformer has an inter-turn short circuit;

[0068] At the same time, the same-frequency load loss ratio is calculated and the same-frequency maximum loss ratio is preset. If the same-frequency load loss ratio is greater than the same-frequency maximum loss ratio, it is determined that the target transformer has a winding fault.

[0069] Regarding the above, it's important to note that directly analyzing transformer faults can easily lead to safety issues. Therefore, a finite element model is used to simulate the transformer's load loss, enabling efficient, fast, and safe load loss analysis and fault type determination. First, geometric modeling is performed. A target finite element model is constructed based on the actual transformer structure, such as core spacers, winding turns, and insulation spacing. The target transformer's load loss data and material properties at 50Hz and 200Hz test voltages must also be matched, as these factors also affect the transformer's load loss. After running the target finite element model to generate curves, different curves can be simulated and solved to calculate loss values at different frequencies. Dual-frequency analysis can determine whether the target transformer has inter-turn short circuits, while single-frequency analysis can determine whether the target transformer has winding faults. Inter-turn short circuits can lead to uneven current distribution within the transformer windings, causing local overheating and increased losses. Therefore, by comparing the changes in load loss at different frequencies, it is possible to effectively determine whether the transformer has a turn-to-turn short circuit. If the loss increase at a frequency of 200Hz is much higher than expected and the change trend is abnormal, the transformer may have a turn-to-turn short circuit. In other words, if the difference between the target transformer's load loss at a 50Hz test voltage and the target transformer's load loss at a 200Hz test voltage is greater than the preset value, then the target transformer is judged to have a turn-to-turn short circuit. If the same-frequency load loss ratio is greater than the same-frequency maximum loss ratio at the same frequency, such as 200Hz, it indicates that the high-frequency impedance of the winding is abnormal, indicating that there is a fault at the winding location.

[0070] S3: If Figure 2 As shown in the figure, the infrared thermal imaging method is introduced, combined with the transformer inter-turn short circuit analysis and winding fault analysis, to locate and determine the fault of the target transformer;

[0071] In this embodiment, step S3 specifically includes:

[0072] C1: During the target transformer system test, infrared thermal imaging data is collected at all locations of the target transformer using an infrared thermal imager to obtain infrared thermal imaging data at different locations of the target transformer.

[0073] C2: Perform Gaussian filtering to reduce noise on the infrared thermal imaging data at different locations of the target transformer, and use the threshold segmentation method to divide the high-temperature areas at different locations of the target transformer to obtain infrared thermal imaging data of the high-temperature areas of the target transformer;

[0074] C3: Compare the infrared thermal imaging data of the target transformer's high-temperature area at different frequencies to obtain temperature difference data at different locations. Build a temperature difference data sorting table, preset dangerous temperature difference data, analyze the temperature difference data sorting table, and mark the target transformer location with temperature difference data greater than the dangerous temperature difference data as the fault location to be analyzed.

[0075] C4: Based on the fault location to be analyzed, fault location and fault determination are performed on the target transformer:

[0076] 1. When a turn-to-turn short circuit exists in the target transformer, the temperature rise rate ratio of the fault location to be analyzed at different frequencies is calculated, and a standard temperature rise rate ratio is preset. If the temperature rise rate ratio of the fault location to be analyzed is greater than the standard temperature rise rate ratio, the corresponding fault location to be analyzed is diagnosed as a turn-to-turn short circuit location.

[0077] It should be noted that if a fault occurs during transformer operation, the temperature at the fault location will be significantly higher than at other locations. For example, the presence of a short-circuit path can cause uneven current distribution within the winding, leading to localized heating in some areas. As frequency increases, the frequency of magnetic field reversals increases, causing stronger Joule heating in the short-circuit area, resulting in higher temperatures. Under variable frequency conditions, increased frequency can increase losses in the ground fault area. Especially at high frequencies, the current path and distribution change, making leakage current between the winding and ground more likely to cause overheating. Therefore, infrared thermal imaging can be used to locate the hottest location, i.e., the fault location to be analyzed. Determining whether the fault location is a turn-to-turn short circuit can be done by determining its temperature characteristics. If, at high frequency, the temperature rise rate at the short-circuit point is two to three times that at standard frequency—that is, the temperature rise rate ratio at the fault location is greater than the standard temperature rise rate ratio—this indicates a turn-to-turn short circuit. Turn-to-turn short circuits typically cause localized current concentration, increasing local losses, particularly copper and some iron losses. Under high-frequency conditions, the skin effect is more obvious, and the current mainly flows through the surface of the winding, which makes the impact of the short-circuit area more prominent, resulting in a faster heating rate, which is a signal of inter-turn short circuit.

[0078] 2. When a winding fault occurs in the target transformer, the nature of the winding fault is determined based on the fault location to be analyzed, including:

[0079] Analyze all fault locations to be analyzed, calculate the distances between different fault locations to be analyzed, and determine the standard distance between the fault locations to be analyzed;

[0080] If the distance between the fault locations to be analyzed is not greater than the standard distance and the proportion is greater than the preset value, it is determined that the overall temperature distribution of the target transformer is uniform and that a winding grounding fault exists in the target transformer;

[0081] The target transformer with a winding grounding fault is calibrated as a winding grounding fault transformer. An insulation resistance test is performed on the possible fault location to be analyzed on the winding grounding fault transformer, and a standard insulation resistance value is preset. The fault location to be analyzed with an insulation resistance less than the standard insulation resistance value is demarcated as a winding grounding fault location.

[0082] The 50Hz and 200Hz loss-frequency characteristic mathematical curves are analyzed to calculate the full-load loss growth rate of the target transformer at different frequencies. If the full-load loss growth rate at 200Hz remains within the standard threshold and the full-load loss growth rate at 50Hz is greater than the standard threshold, it is determined that the target transformer has an abnormal winding turns fault.

[0083] It should be noted that a winding ground fault refers to an abnormal electrical connection between a transformer's winding and ground. This problem may be caused by aging, moisture, mechanical damage, or cracked insulation. The temperature characteristic of a winding ground fault is that the ground current flows through a large area of metal components in the transformer, resulting in a relatively uniform temperature distribution. The location of a transformer ground fault can be diagnosed by testing the insulation resistance. If the winding-to-ground insulation resistance is less than 1 megohm, a ground fault exists. The fault location under analysis is defined as a winding ground fault if the insulation resistance is less than the standard insulation resistance. Another type of winding fault is abnormal turns count. Diagnosing this fault involves checking if the full-load loss at the standard frequency differs significantly from the standard value, while the loss growth rate at high frequencies is normal. Inconsistent turns count or design flaws in transformer windings can lead to mismatches in resistance, inductance, and impedance, thereby affecting the transformer's operating efficiency and load capacity. Winding design flaws may include incorrect turns count, inter-turn shorts, and irregular winding arrangement.

[0084] S4: Based on the fault location and fault determination of the target transformer, a transformer safety level scoring model is constructed, and the safety evaluation of the target transformer is performed based on the transformer safety level scoring model;

[0085] In this embodiment, step S4 specifically includes:

[0086] D1: Determine the transformer safety rating model indicators, where the transformer safety rating model indicators include inter-turn short circuit, winding grounding fault and abnormal winding turns fault of the target transformer;

[0087] D2: Introducing a big data network, the network retrieves the hazard states of the transformer when it is affected by inter-turn short circuit, winding ground fault, and abnormal winding turns fault. A historical benefit impact analysis is performed on different hazard states to obtain a historical benefit impact ranking table.

[0088] D3: Based on the historical benefit impact ranking table, dynamically assign weights to different transformer safety rating model indicators, and determine the deduction points when generating different transformer safety rating model indicators based on the dynamic weights of the indicators;

[0089] D4: Based on the deduction scores when generating indicators of different transformer safety level scoring models, set the target transformer safety level scoring model, where the deduction scores are positively correlated with the dynamic weights, and the full score is equal to 100 points;

[0090] D5: Determine the safety level of the target transformer under different total scores, and perform safety scoring on the target transformer in combination with the target transformer safety level scoring model.

[0091] It should be noted that the purpose of the target transformer safety rating scoring model to process the target transformer's safety score is to systematically evaluate the transformer's safety status and provide a quantitative basis for fault warning, life management, and maintenance strategies. Different levels of transformers are handled differently. For example, when a turn-to-turn short circuit and a ground fault occur simultaneously, the transformer is scored. If the score is lower than a certain value, it is necessary to pay and operate and repair it first, or even shut down immediately for troubleshooting. The weights of the indicators in the transformer safety rating scoring model are divided according to the economic benefits brought by different hazard states. For example, different hazard states cause different losses, and the weights are allocated according to the percentage of losses, thereby realizing the setting of deduction points and processing the safety score of the target transformer.

[0092] Example 2:

[0093] Based on the evaluation method of Example 1, this embodiment provides a variable frequency transformer safety evaluation system for loss testing, including:

[0094] A load loss acquisition module, configured to apply test voltages of different frequencies to a target transformer and acquire load loss data of the target transformer generated by the test voltages of different frequencies;

[0095] The fault analysis module is used to establish a loss-frequency characteristic mathematical curve through finite element simulation algorithm and combined with the load loss data of the target transformer to perform curve deviation analysis. Based on the analysis results, it also performs turn-to-turn short circuit analysis and winding fault analysis on the target transformer.

[0096] The fault determination and location module uses infrared thermal imaging combined with transformer turn-to-turn short-circuit analysis and winding fault analysis to locate and determine the fault of the target transformer.

[0097] The safety evaluation module is used to construct a transformer safety level scoring model and perform safety evaluation on the target transformer based on the transformer safety level scoring model.

[0098] This embodiment also provides a computer storage medium that stores a computer program that can implement the method described above when a processor executes the computer program. The computer-readable medium can be considered to be tangible and non-transitory. Non-limiting examples of non-transitory tangible computer-readable media include non-volatile memory circuits (such as flash memory circuits, erasable programmable read-only memory circuits, or mask read-only memory circuits), volatile memory circuits (such as static random access memory circuits or dynamic random access memory circuits), magnetic storage media (such as analog or digital tapes or hard drives), and optical storage media (such as CDs, DVDs, or Blu-ray discs). The computer program includes processor-executable instructions stored on at least one non-transitory tangible computer-readable medium. The computer program may also include or rely on stored data. The computer program may include a basic input / output system (BIOS) that interacts with the hardware of a special-purpose computer, device drivers that interact with specific devices of the special-purpose computer, one or more operating systems, user applications, background services, background applications, etc.

[0099] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0100] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0101] Example 3:

[0102] In order to verify the effectiveness and effect of the present invention, this embodiment conducted a transformer load loss test, as follows:

[0103] 1. This test uses the HDBS-Z power transformer low voltage frequency conversion no-load parameter tester. The technical parameters of the HDBS-Z power transformer low voltage frequency conversion no-load parameter tester are as follows:

[0104] Input power: 380V±10%, 50Hz;

[0105] Output voltage: 0-1000V;

[0106] Frequency range: 50Hz, 150Hz, 200Hz;

[0107] Current: 0.5A~5A;

[0108] Power (50Hz): <±0.5% when the power factor is 0.1~1.00, <±1.0% when the power factor is 0.02~0.1;

[0109] Voltage measurement (50Hz): <±0.2%;

[0110] Current measurement (50Hz): <±0.2%;

[0111] Size: 500*500*1143mm;

[0112] Weight: 141kg.

[0113] 2. Conduct test wiring

[0114] The 500kV transformer is a single-phase transformer, and the test wiring is as follows: Figures 3 to 5 shown.

[0115] 3. Testing process:

[0116] (1) Perform a 5A current load test at 50Hz using the same wiring as for the low-load test for a single-phase transformer. Record the measured data after it stabilizes.

[0117] (2) Reduce the voltage to 0, adjust the frequency output to 200 Hz, and increase the voltage to 5 A. Record the data after it stabilizes.

[0118] (3) Adjust the transformer gear to the rated gear and repeat test steps 1-2, and name the test record numbers in sequence.

[0119] (4) Adjust the transformer gear to the negative limit gear and repeat test steps 1-2, and name the test record numbers in sequence.

[0120] (5) Conduct a 5A current load test on the transformer at 50Hz using the transformer high-to-low load test wiring. Record the measured data after it stabilizes.

[0121] (6) Reduce the voltage to 0, adjust the frequency output to 200 Hz, and increase the current to 5 A. Record the data after it stabilizes.

[0122] (7) Perform a 5A current load test at 50Hz using the transformer's high-to-medium load test wiring. Record the measured data after it stabilizes.

[0123] (8) Reduce the voltage to 0, adjust the frequency output to 200 Hz, and increase the current to 5 A. Record the data after it stabilizes.

[0124] (9) Adjust the transformer gear to the rated gear and repeat test steps 7-8, and name the test record numbers in sequence.

[0125] (10) Adjust the transformer gear to the minimum negative tap position and repeat test steps 7-8, naming the test record numbers in sequence.

[0126] (11) After the test, clean up the test site and ensure that the transformer is restored to its original state.

[0127] 4. Test Results

[0128] The test data is shown in Table 1:

[0129] Table 1 Load test data

[0130]

[0131]

[0132] 5. Test Conclusion

[0133] According to the data in Table 1, the low-voltage variable-frequency load parameter test of the transformer was analyzed according to the above method and no obvious abnormalities were found.

Claims

1. A transformer safety assessment method based on variable frequency loss testing, characterized in that: The steps include: S1: applying test voltages of different frequencies to the target transformer and collecting load loss data of the target transformer generated by the test voltages of different frequencies; S2: Using a finite element simulation algorithm and combined with the load loss data of the target transformer, a loss-frequency characteristic mathematical curve is established to analyze the curve deviation. Based on the analysis results, turn-to-turn short-circuit analysis and winding fault analysis are performed on the target transformer. S3: Introducing infrared thermal imaging, combined with transformer turn-to-turn short circuit analysis and winding fault analysis, to locate and determine the fault of the target transformer; S4: Based on the fault location and fault determination of the target transformer, a transformer safety level scoring model is constructed, and the safety evaluation of the target transformer is performed based on the transformer safety level scoring model.

2. The method for safety assessment of variable frequency transformer based on loss test according to claim 1, characterized in that: The step S1 specifically includes: A1: Calibrate the transformer that needs to be tested for loss as the target transformer, and at the same time identify the electrical equipment connected to the target transformer and calibrate it as the target electrical equipment; A2: Connect the target transformer to the target electrical equipment to build the target transformer system and preset two test voltage frequencies: 50 Hz and 200 Hz. The 50 Hz test voltage represents the test voltage at the normal operating frequency, while the 200 Hz test voltage represents the test voltage at the double frequency condition. A3: Apply a 50Hz test voltage to the target transformer, preset a thermal stabilization time, and convert the test voltage in the target transformer to a 200Hz test voltage after the thermal stabilization time; A4: Perform load tests on the target transformer system while applying a 50 Hz test voltage and a 200 Hz test voltage, and ensure that other operating conditions of the target transformer system remain consistent during the tests. A5: Perform a load test on the target transformer system and calculate the power loss data of the target transformer at a test voltage of 50 Hz and a test voltage of 200 Hz, thereby obtaining the load loss data of the target transformer at a test voltage of 50 Hz and a test voltage of 200 Hz.

3. The transformer safety assessment method based on variable frequency loss test according to claim 2, characterized in that: Other operating conditions of the target transformer system in step A4 include the operating temperature, wiring type, and rated current of the target transformer.

4. The transformer safety assessment method based on variable frequency loss test according to claim 2, characterized in that: The step S2 specifically includes: B1: Obtain the structural parameters of the target transformer in the target transformer system, and construct a finite element model of the target transformer based on the structural parameters of the target transformer, and calibrate it as the target finite element model; The target finite element model is a three-dimensional model of the target transformer. The material properties of the target transformer are set in the three-dimensional model, and the load loss data of the target transformer under the test voltage of 50Hz and 200Hz are matched. B2: Run the target finite element model and derive the load loss curves under the test voltage of 50Hz-300Hz, which are calibrated as loss-frequency characteristic curves; B3: Compare the current loss-frequency characteristic curve with the previous curve and calculate the Pearson correlation coefficient between the two curves. If the coefficient is greater than a preset value, it is determined that the target transformer has an inter-turn short circuit; At the same time, the same-frequency load loss ratio is calculated and the same-frequency maximum loss ratio is preset. If the same-frequency load loss ratio is greater than the same-frequency maximum loss ratio, it is determined that the target transformer has a winding fault.

5. The transformer safety assessment method based on variable frequency loss test according to claim 4 is characterized in that: The step S3 specifically includes: C1: During the target transformer system test, infrared thermal imaging data is collected at all locations of the target transformer using an infrared thermal imager to obtain infrared thermal imaging data at different locations of the target transformer. C2: Perform Gaussian filtering to reduce noise on the infrared thermal imaging data at different locations of the target transformer, and use the threshold segmentation method to divide the high-temperature areas at different locations of the target transformer to obtain infrared thermal imaging data of the high-temperature areas of the target transformer; C3: Compare the infrared thermal imaging data of the target transformer's high-temperature area at different frequencies to obtain temperature difference data at different locations. Build a temperature difference data sorting table, preset dangerous temperature difference data, analyze the temperature difference data sorting table, and mark the target transformer location with temperature difference data greater than the dangerous temperature difference data as the fault location to be analyzed. C4: Based on the fault location to be analyzed, fault location and fault determination are performed on the target transformer.

6. A transformer safety assessment method based on variable frequency loss testing according to claim 5, characterized in that: In step C4, when a turn-to-turn short circuit exists in the target transformer, the temperature rise rate ratio of the fault position to be analyzed at different frequencies is calculated for the fault position to be analyzed, and a standard temperature rise rate ratio is preset. If the temperature rise rate ratio of the fault position to be analyzed is greater than the standard temperature rise rate ratio, the corresponding fault position to be analyzed is diagnosed as a turn-to-turn short circuit position.

7. The transformer safety assessment method based on variable frequency loss test according to claim 5, characterized in that: In step C4, when a winding fault occurs in the target transformer, the nature of the winding fault is determined for the transformer in combination with the fault location to be analyzed, specifically including: Analyze all fault locations to be analyzed, calculate the distances between different fault locations to be analyzed, and determine the standard distance between the fault locations to be analyzed; If the distance between the fault locations to be analyzed is not greater than the standard distance and the proportion is greater than the preset value, it is determined that the overall temperature distribution of the target transformer is uniform and that a winding grounding fault exists in the target transformer; The target transformer with a winding grounding fault is calibrated as a winding grounding fault transformer. An insulation resistance test is performed on the possible fault location to be analyzed on the winding grounding fault transformer, and a standard insulation resistance value is preset. The fault location to be analyzed with an insulation resistance less than the standard insulation resistance value is demarcated as a winding grounding fault location. Calculate the full-load loss growth rate of the target transformer at different frequencies. If the full-load loss growth rate at 200 Hz remains within the standard threshold and the full-load loss growth rate at 50 Hz is greater than the standard threshold, it is determined that the target transformer has an abnormal winding turns fault.

8. The transformer safety assessment method based on variable frequency loss test according to claim 5, characterized in that: The step S4 specifically includes: D1: Determine the transformer safety rating model indicators, where the transformer safety rating model indicators include inter-turn short circuit, winding grounding fault and abnormal winding turns fault of the target transformer; D2: Introducing a big data network, the network retrieves the hazard states of the transformer when it is affected by inter-turn short circuit, winding ground fault, and abnormal winding turns fault. A historical benefit impact analysis is performed on different hazard states to obtain a historical benefit impact ranking table. D3: Based on the historical benefit impact ranking table, dynamically assign weights to different transformer safety rating model indicators, and determine the deduction points when generating different transformer safety rating model indicators based on the dynamic weights of the indicators; D4: Based on the deduction scores when generating indicators of different transformer safety level scoring models, set the target transformer safety level scoring model, where the deduction scores are positively correlated with the dynamic weights, and the full score is equal to 100 points; D5: Determine the safety level of the target transformer under different total scores, and perform safety scoring on the target transformer in combination with the target transformer safety level scoring model.

9. A transformer safety assessment system based on variable frequency loss testing, characterized in that: include: A load loss acquisition module, configured to apply test voltages of different frequencies to a target transformer and acquire load loss data of the target transformer generated by the test voltages of different frequencies; The fault analysis module is used to establish a loss-frequency characteristic mathematical curve through finite element simulation algorithm and combined with the load loss data of the target transformer to perform curve deviation analysis. Based on the analysis results, it also performs turn-to-turn short circuit analysis and winding fault analysis on the target transformer. The fault determination and location module uses infrared thermal imaging combined with transformer turn-to-turn short-circuit analysis and winding fault analysis to locate and determine the fault of the target transformer. The safety evaluation module is used to construct a transformer safety level scoring model and perform safety evaluation on the target transformer based on the transformer safety level scoring model.

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