A transformer abnormal fan positioning method based on generalized thermal resistance decomposition

Abstract

The application provides a transformer abnormal fan positioning method based on generalized thermal resistance decomposition, which establishes a transformer overall experiment device, including a direct current power supply, an oil tank, a winding, a radiator, a flowmeter, a thermocouple, an oil pump and a fan. The positioning method establishes generalized thermal resistance for characterizing abnormal fan positions according to the differences in heat exchange between air and oil flow caused by different fan positions. Then, a top oil temperature thermal model is constructed based on the convection heat transfer of transformer oil and air, the generalized thermal resistance is introduced into the air side thermal resistance of the thermal model, and the change law of the top oil temperature and the position parameters of the generalized thermal resistance decomposition is analyzed. Finally, the abnormal fan position is determined by using the amplitude of the reduction multiple of the position parameters. The application utilizes the different oil flow thermal effects caused by the position differences of abnormal fans to realize the position positioning of the transformer abnormal fan, and provides a reference for the subsequent maintenance and repair of the fan.

Description

Technical Field

[0001] This invention relates to the field of transformer fault diagnosis technology, and specifically to a method for locating abnormal fans in transformers based on generalized thermal resistance decomposition. Background Technology

[0002] With the continued impact of high temperatures and harsh environments, the power load increases dramatically in a short period, causing the transformer winding temperature to remain excessively high for extended periods. This accelerates the thermal aging process of the insulation, significantly impacting the transformer's efficiency and lifespan. Transformers are one of the key pieces of equipment in the power system, and their safe and efficient operation plays a crucial role in the stable transmission of electrical energy. Therefore, to ensure that the transformer winding temperature remains within the specified range, it is essential to ensure the normal and reliable operation of the transformer cooling system.

[0003] As my country's power grid expands, higher voltage and larger capacity oil-immersed transformers are being put into use. When these high-voltage transformers operate under overload conditions for extended periods, the overall transformer temperature rises sharply. With the prolonged operation of the cooling system, the probability of cooling equipment failure and aging also increases. As a crucial cooling component, the fan's normal and efficient operation determines the safe and reliable operation of the transformer cooling system. However, current methods rely solely on switch sensors to determine fan operation, making it difficult to effectively locate abnormal fans. The location of faults in abnormal fans remains unclear, hindering real-time continuous monitoring and significantly impacting heat dissipation efficiency, thus greatly interfering with the troubleshooting and maintenance of cooling equipment. Therefore, considering the different oil-heat effects caused by different abnormal fan locations, a transformer abnormal fan location method based on generalized thermal resistance decomposition is proposed. This method improves the accuracy of fan abnormality monitoring and enhances maintenance efficiency for early-stage fan failures. Summary of the Invention

[0004] This invention provides a method for locating abnormal fans in transformers based on generalized thermal resistance decomposition. By establishing different generalized thermal resistances at different abnormal fan locations, the variation law of top oil temperature and the location parameters of generalized thermal resistance decomposition can be obtained, thereby locating the abnormal fan location in the transformer.

[0005] To achieve the above objectives, a transformer abnormal fan location method based on generalized thermal resistance decomposition includes the following steps: establishing a transformer overall experimental setup, including an oil tank (1), windings (2), ultrasonic flowmeter (3), thermocouple (4), oil pump (5), bottom oil passage (6), heat sink (7), fan (8), and DC power supply (9); recording data changes in transformer ambient temperature and load factor; changing the operating status of fan (8); obtaining transformer top oil temperature data; and establishing a transformer top oil temperature thermal model. Then, based on different abnormal fan (8) locations, various fault factors are obtained and introduced into the air-side thermal resistance to form a generalized thermal resistance. Based on the top oil temperature thermal model and parameters of the least squares method, the method is applied to the transformer. The position parameter variation curve of the generalized thermal resistance decomposition is estimated and used as a visualization indicator for the next step of judging the position of the abnormal fan (8). Then, based on the parameter variation of the positions of various abnormal fans (8), the standard range of the positions of various abnormal fans (8) is determined by the criterion of the average value of the reduction factor relative to normal operation ±2 × standard deviation. Finally, based on the relevant data of the abnormal operation of the actual transformer fan, the position parameter variation range is obtained through the above 1~3 steps, and the overlap with the standard curve range is judged. The Pearson correlation coefficient is used to judge the correlation between the reduction factor value of the position parameter and the standard value, and then the abnormal state of the actual transformer fan is inferred.

[0006] Furthermore, according to claim 1, the transformer abnormal fan location method based on generalized thermal resistance decomposition is characterized in that, in step 2, the fault factor calculation formula is obtained by utilizing the height difference between the abnormal fan (8) and the bottom oil passage (6) and the oil flow movement law:

[0007] ;

[0008] In the formula, Φ H The fault factor is defined as follows: W(H) is the work done by the oil when the fan is running at full normal speed; W(h) is the work done by the oil when the fan is running abnormally; x is the distance the oil travels to the bottom oil passage; H is the height of the radiator; h is the fault factor. i Let i be the height of each fan reaching the bottom oil passage, where i is 1, 2, ..., m, m is the number of fans, and h is the height of each fan reaching the bottom oil passage. fan This refers to the range within which the fan operates normally.

[0009] Furthermore, according to claim 1, the method for locating abnormal transformer fans based on generalized thermal resistance decomposition is characterized in that, in step 2, the calculation formula for the generalized thermal resistance and its decomposed location parameters is obtained by utilizing the convective heat transfer relationship on the air side:

[0010] ;

[0011] ;

[0012] ;

[0013] ;

[0014] ;

[0015] In the formula, R ’ th-air R is the generalized thermal resistance on the air side. th-air Let A be the initial thermal resistance on the air side. air h represents the heat dissipation area on the air side. ’ n h ’ f Nu represents the heat transfer coefficient of air under natural convection and forced convection. f Re and Pr are the Nusselt number, Reynolds number, and Prandtl number of air under forced convection, respectively, λ is the thermal conductivity of air, and d is the thermal conductivity of air. h V is the length of the fluid flow channel. f The rated wind speed is given by C, u, p, and q, which are positional parameters, and v is the kinematic viscosity of the air.

[0016] Furthermore, according to claim 1, the method for locating abnormal fans in a transformer based on generalized thermal resistance decomposition is characterized in that, in step 3, the average value and standard deviation of the reduction factor of the position parameter are obtained using the position parameter variation curve of the abnormal fan (8), and then the average value ± 2 × standard deviation is used as the standard range for judging the position of the abnormal fan (8); wherein, the reduction factor calculation formula is:

[0017] ;

[0018] In the formula, γ i The reduction factor of parameter u after the fan (8) malfunctions, i takes the values ​​1, 2, ..., n, where n is the number of data records, u i The u parameter value is the value of the fan (8) after the fan malfunctions, where i is 1, 2, ..., n, and n is the number of records. nor The average value of the u parameter when the fan (8) is running normally.

[0019] Furthermore, according to claim 1, the method for locating abnormal fans in transformers based on generalized thermal resistance decomposition is characterized in that, in step 4, the overlap analysis is performed using the range of the actual fan's location parameters after the abnormality and the aforementioned standard range to preliminarily determine the location of the abnormal fan; wherein, the formula for calculating the range overlap is:

[0020] ;

[0021] In the formula, ζ represents the degree of overlap of the range of the reduction factor of the u parameter. σ represents the average value of the reduction factor of the u parameter after the abnormal fan (8). γ This represents the standard deviation of the reduction factor of the u parameter after the abnormal fan (8). ’ σ is the average value of the reduction factor of the u parameter after the actual fan malfunction. ’ γ This represents the standard deviation of the reduction factor of the u parameter after the actual fan malfunction.

[0022] Furthermore, by utilizing the reduction factor of the position parameters and the Pearson correlation coefficient, the correlation between the reduction factor of the actual transformer fan position parameters and the standard abnormal fan (8) is analyzed to further determine the position of the actual abnormal fan; wherein, the formula for calculating the correlation coefficient is:

[0023] ;

[0024] ;

[0025] In the formula, σ γ-type The standard deviation of the reduction factor of u parameter under various abnormal fan (8) positions, σ ’ γ σ represents the standard deviation of the reduction factor of the u parameter after the actual fan malfunction. at γ is the covariance between the actual and standard conditions. ’ i This represents the reduction factor of the u parameter after the actual fan malfunction, where i takes values ​​of 1, 2, ..., n, and n is the number of data records. ’ This represents the average reduction factor of the u-parameter after the actual fan malfunction. ƞ represents the average reduction factor of u parameter after various fan malfunctions, and ƞ is the correlation coefficient between the standard reduction factor and the actual reduction factor.

[0026] By analyzing and comparing the curve changes of the actual location parameters, and combining the two judgment methods mentioned above, the location of the abnormal fan of the actual transformer can be located. Attached Figure Description

[0027] Figure 1 This is a structural diagram of the transformer device in the present invention;

[0028] The above description is merely an illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific structure described, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, and all such modifications or additions should fall within the protection scope of the present invention. Example

[0029] This invention proposes a method for locating abnormal fans in transformers based on generalized thermal resistance decomposition, comprising the following steps:

[0030] Step 1: Establish the overall experimental device for the transformer, including the oil tank (1), winding (2), ultrasonic flow meter (3), thermocouple (4), oil pump (5), bottom oil channel (6), heat sink (7), fan (8) and DC power supply (9). Record the data changes of the transformer ambient temperature and load factor, change the operating status of the fan (8), obtain the top oil temperature data of the transformer, and establish the thermal model of the top oil temperature of the transformer.

[0031] Step 2: Based on the different abnormal fan (8) locations, various fault factors are obtained and introduced into the air-side thermal resistor to form a generalized thermal resistance. Based on the top oil temperature thermal model and the parameter estimation of the least squares method, the position parameter change curve of the generalized thermal resistance decomposition is obtained as a visualization indicator for the next step of judging the abnormal fan (8) location.

[0032] Step 3: Based on the parameter changes of various abnormal fan (8) positions, determine the standard range of various abnormal fan (8) positions using the criterion of the average value of the reduction factor relative to normal operation ±2 × standard deviation;

[0033] Step 4: Based on the relevant data of the actual abnormal operation of the transformer fan, obtain the range of position parameter variation through the above steps 1 to 3, determine the degree of overlap with the standard curve range, and use the Pearson correlation coefficient to determine the correlation between the reduction factor of the position parameter and the standard value, thereby inferring the abnormal state of the actual transformer fan.

[0034] In step 2, using the height difference between the abnormal fan (8) and the bottom oil passage (6) and the movement law of the oil flow, the formula for calculating the fault factor is obtained as follows:

[0035] ;

[0036] In the formula, Φ H The fault factor is defined as follows: W(H) is the work done by the oil when the fan is running at full normal speed; W(h) is the work done by the oil when the fan is running abnormally; x is the distance the oil travels to the bottom oil passage; H is the height of the radiator; h is the fault factor. i Let i be the height of each fan reaching the bottom oil passage, where i is 1, 2, ..., m, m is the number of fans, and h is the height of each fan reaching the bottom oil passage. fan This refers to the range within which the fan operates normally.

[0037] In step 2, using the convective heat transfer relationship on the air side, the formulas for calculating the generalized thermal resistance and its decomposed location parameters are obtained as follows:

[0038] ;

[0039] ;

[0040] ;

[0041] ;

[0042] ;

[0043] In the formula, R ’ th-air R is the generalized thermal resistance on the air side. th-air Let A be the initial thermal resistance on the air side. air h represents the heat dissipation area on the air side. ’ n h ’ f Nu represents the heat transfer coefficient of air under natural convection and forced convection. f Re and Pr are the Nusselt number, Reynolds number, and Prandtl number of air under forced convection, respectively, λ is the thermal conductivity of air, and d is the thermal conductivity of air. h V is the length of the fluid flow channel. f Where C is the rated wind speed, u, p, and q are position parameters, and v is the kinematic viscosity of the air.

[0044] In step 3, the average value and standard deviation of the reduction factor of the position parameter are obtained using the position parameter variation curve of the abnormal fan (8), and then the average value ± 2 × standard deviation is used as the standard range for judging the position of the abnormal fan (8); wherein, the reduction factor is calculated by the formula:

[0045] ;

[0046] In the formula, γ i The reduction factor of parameter u after the fan (8) malfunctions, i takes the values ​​1, 2, ..., n, where n is the number of data records, u i The u parameter value is the value of the fan (8) after the fan malfunctions, where i is 1, 2, ..., n, and n is the number of records. nor The average value of the u parameter when the fan (8) is running normally.

[0047] In step 4, the overlap analysis is performed using the range of the actual fan location parameters after the malfunction and the aforementioned standard range to preliminarily determine the location of the malfunctioning fan; wherein, the formula for calculating the range overlap is:

[0048] ;

[0049] In the formula, ζ represents the degree of overlap of the range of the reduction factor of the u parameter. σ represents the average value of the reduction factor of the u parameter after the abnormal fan (8).γ This represents the standard deviation of the reduction factor of the u parameter after the abnormal fan (8). ’ σ is the average value of the reduction factor of the u parameter after the actual fan malfunction. ’ γ The standard deviation represents the factor by which the u-parameter decreases after the actual fan malfunction;

[0050] By utilizing the reduction factor of the position parameters and the Pearson correlation coefficient, the correlation between the reduction factor of the actual transformer fan position parameters and the standard abnormal fan (8) is analyzed to further determine the position of the actual abnormal fan; wherein, the formula for calculating the Pearson correlation coefficient is:

[0051] ;

[0052] ;

[0053] In the formula, σ γ-type The standard deviation of the reduction factor of u parameter under various abnormal fan (8) positions, σ ’ γ σ represents the standard deviation of the reduction factor of the u parameter after the actual fan malfunction. at γ is the covariance between the actual and standard conditions. ’ i This represents the reduction factor of the u parameter after the actual fan malfunction, where i takes values ​​of 1, 2, ..., n, and n is the number of data records. ’ This represents the average reduction factor of the u-parameter after the actual fan malfunction. ƞ represents the average reduction factor of u parameter after various fan malfunctions, and ƞ is the correlation coefficient between the standard reduction factor and the actual reduction factor.

[0054] By analyzing and comparing the curve changes of the actual location parameters, and combining the two judgment methods mentioned above, the location of the abnormal fan of the actual transformer can be located.

[0055] As can be seen from the above technical solutions, this invention provides a method for locating abnormal fans in transformers based on generalized thermal resistance decomposition. By introducing fault factors to construct generalized thermal resistance, the complex fluid thermal effects are transformed into quantifiable location parameters *u*, and fault identification is performed using the overlap and correlation of the reduced factor. This method can not only determine whether a fan is abnormal, but also accurately locate the specific fan location where the fault occurs, providing a reliable basis for refined maintenance of transformer cooling systems. In the above embodiments, the invention is only described exemplarily; however, those skilled in the art can make various modifications to the invention without departing from its spirit and scope after reading this patent application.

Claims

1. A method for locating abnormal fans in transformers based on generalized thermal resistance decomposition, characterized in that, Includes the following steps: Step 1: Establish the overall experimental device for the transformer, including the oil tank (1), winding (2), ultrasonic flow meter (3), thermocouple (4), oil pump (5), bottom oil channel (6), heat sink (7), fan (8) and DC power supply (9). Record the changes in the transformer ambient temperature and load factor, change the operating status of the fan (8), obtain the top oil temperature data of the transformer, and establish a thermal model of the top oil temperature of the transformer. Step 2: Based on the different abnormal fan (8) locations, various fault factors are obtained and introduced into the air-side thermal resistor to form a generalized thermal resistance. Based on the top oil temperature thermal model and the parameter estimation of the least squares method, the position parameter change curve of the generalized thermal resistance decomposition is obtained as a visualization indicator for the next step of judging the abnormal fan (8) location. Step 3: Based on the parameter changes of various abnormal fan (8) positions, determine the standard range of various abnormal fan (8) positions using the criterion of the average value of the reduction factor relative to normal operation ±2 × standard deviation; Step 4: Based on the relevant data of the actual abnormal operation of the transformer fan, obtain the range of position parameter variation through the above steps 1 to 3, determine the degree of overlap with the standard curve range, and use the Pearson correlation coefficient to determine the correlation between the reduction factor of the position parameter and the standard value, thereby inferring the abnormal state of the actual transformer fan. In step 2, using the height difference between the abnormal fan (8) and the bottom oil passage (6) and the movement law of the oil flow, the formula for calculating the fault factor is obtained as follows: ； In the formula, Φ H The fault factor is defined as follows: W(H) is the work done by the oil when the fan is running at full normal speed, W(h) is the work done by the oil when the fan is running abnormally, x is the distance the oil travels to the bottom oil passage, H is the height of the radiator, and h is the fault factor. i Let i be the height of each fan reaching the bottom oil passage, where i is 1, 2, ..., m, m is the number of fans, and h is the height of each fan reaching the bottom oil passage. fan This refers to the range within which the fan operates normally. In step 2, using the convective heat transfer relationship on the air side, the formulas for calculating the generalized thermal resistance and its decomposed location parameters are obtained as follows: ； ； ； ； ； In the formula, R ’ th-air R is the generalized thermal resistance on the air side. th-air Let A be the initial thermal resistance on the air side. air h represents the heat dissipation area on the air side. ’ n h ’ f Nu represents the heat transfer coefficient of air under natural convection and forced convection. f Re and Pr are the Nusselt number, Reynolds number, and Prandtl number of air under forced convection, respectively, λ is the thermal conductivity of air, and d is the thermal conductivity of air. h V is the length of the fluid flow channel. f Where C is the rated wind speed, u, p, and q are position parameters, and v is the kinematic viscosity of the air. In step 3, the average value and standard deviation of the reduction factor of the position parameter are obtained using the position parameter variation curve of the abnormal fan (8), and then the average value ± 2 × standard deviation is used as the standard range for judging the position of the abnormal fan (8); wherein, the reduction factor is calculated by the formula: ； In the formula, γ i The reduction factor of parameter u after the fan (8) malfunctions, i takes the values ​​1, 2, ..., n, where n is the number of recorded data, u i The u parameter value is the value after the fan (8) malfunctions, where i takes the values ​​1, 2, ..., n, and n is the number of data records. nor The average value of the u parameter when the fan (8) is running normally; 2. The transformer abnormal fan location method based on generalized thermal resistance decomposition according to claim 1, characterized in that, In step 4, the overlap analysis is performed using the range of the actual fan location parameters after the malfunction and the aforementioned standard range to preliminarily determine the location of the malfunctioning fan; wherein, the formula for calculating the range overlap is: ； In the formula, ζ represents the degree of overlap of the range of the reduction factor of the u parameter. σ represents the average value of the reduction factor of the u parameter after the abnormal fan (8). γ This represents the standard deviation of the reduction factor of the u parameter after the abnormal fan (8). ’ σ is the average value of the reduction factor of the u parameter after the actual fan malfunction. ’ γ The standard deviation represents the factor by which the u-parameter decreases after the actual fan malfunction; By utilizing the reduction factor of the position parameters and the Pearson correlation coefficient, the correlation between the reduction factor of the actual transformer fan position parameters and the standard abnormal fan (8) is analyzed to further determine the position of the actual abnormal fan; wherein, the formula for calculating the Pearson correlation coefficient is: ； ； In the formula, σ γ-type The standard deviation of the reduction factor of u parameter under various abnormal fan (8) positions, σ ’ γ σ represents the standard deviation of the reduction factor of the u parameter after the actual fan malfunction. at γ is the covariance between the actual and standard conditions. ’ i This represents the reduction factor of the u parameter after the actual fan malfunction, where i takes values ​​of 1, 2, ..., n, and n is the number of data records. ’ This represents the average reduction factor of the u-parameter after the actual fan malfunction. ƞ represents the average reduction factor of u parameter after various fan malfunctions, and ƞ is the correlation coefficient between the standard reduction factor and the actual reduction factor. By analyzing and comparing the curve changes of the actual location parameters, and combining the two judgment methods mentioned above, the location of the abnormal fan of the actual transformer can be located.

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