A method for axial displacement fault diagnosis of transformer windings based on three-dimensional swept frequency impedance curve analysis

Abstract

This invention discloses a method for diagnosing axial displacement faults in transformer windings based on three-dimensional swept-frequency impedance curve analysis. This method involves scanning the frequency ω and amplitude Z... k (jω) and phase θ k (jω) is concentrated in a three-dimensional plot, forming a three-dimensional swept-frequency impedance curve. The normalized Euclidean distance ED between the measured curve and the fingerprint curve in the mid-frequency band is calculated. * By comparing and analyzing the differences in the resonant point characteristics of the three-dimensional curves from different viewpoints and projection planes, the method can diagnose and determine the severity of winding axial displacement faults. The proposed method incorporates the phase frequency information of the scanning impedance, which includes more fault characteristic information, enabling sensitive identification of winding axial displacement faults. Furthermore, by quantifying the distance of the three-dimensional curves using mathematical indicators, the method can predict the degree of winding faults, providing a reference for relevant personnel to promptly eliminate potential faults and formulate relevant maintenance plans.

Description

Technical Field

[0001] This invention relates to the field of transformer winding condition monitoring and fault diagnosis, specifically to a method for diagnosing transformer winding axial displacement faults based on three-dimensional swept frequency impedance curve analysis. Background Technology

[0002] Power transformers are key assets connecting transmission and distribution networks, playing a crucial role in transforming voltage levels and transmitting electrical energy. The operating environment of power transformers is typically harsh, making them prone to various faults, with axial displacement faults being the most common. If this fault is not detected promptly, its cumulative effect can lead to further winding collapse or failure of the end support structure. Therefore, to maintain the normal and stable operation of transformers, sensitive, reliable, and cost-effective fault diagnosis techniques are needed to detect even minor winding axial displacement faults, thus preventing more serious damage to the transformer.

[0003] Frequency Response Analysis (FRA) is widely used in industrial applications for detecting winding deformation due to its ease of operation and high accuracy. In recent years, researchers have conducted numerous improvements to enhance the sensitivity and accuracy of transformer diagnosis using frequency response curves. Researchers at Xi'an Jiaotong University, building upon the FRA method, first proposed the Sweep Frequency Impedance (SFI) method. This method combines the advantages of both the short-circuit impedance method and the frequency response method, offering a simpler testing procedure, higher signal-to-noise ratio, stronger anti-interference capabilities, and superior sensitivity. However, current techniques do not consider the phase frequency information of the sweep impedance, potentially leading to the loss of crucial fault information. Therefore, incorporating phase information into the transformer winding sweep impedance response and constructing a new curve could potentially improve the accuracy and sensitivity of axial displacement fault diagnosis in transformer windings. Summary of the Invention

[0004] This invention provides a method for diagnosing axial displacement faults in transformer windings based on three-dimensional swept-frequency impedance curve analysis. It integrates the scanned frequency, amplitude, and phase into a three-dimensional graph, forming a three-dimensional swept-frequency impedance curve. This curve incorporates phase frequency information of the scanned impedance, including more fault characteristic information, and effectively improves the sensitivity of identifying transformer axial displacement faults. Analysis of the three-dimensional swept-frequency impedance curve can effectively detect whether an axial displacement fault has occurred in the transformer winding and the severity of the fault, providing a reference for personnel to promptly locate and eliminate potential faults.

[0005] The technical solution adopted in this invention is as follows:

[0006] 1. A method for diagnosing axial displacement faults in transformer windings based on three-dimensional swept-frequency impedance curve analysis, characterized by the following steps:

[0007] Step 1: Short-circuit one side of the transformer winding with a wire, and connect a resistor with a resistance value of [value missing] to the beginning and end of the winding being tested. sampling resistor and A frequency of 1 Hz was injected at the beginning of the winding under test. A 1MHz sinusoidal sweep frequency signal;

[0008] Step 2: Measure the input voltage of the winding under test. Response voltage and the current of the winding under test The sweep frequency impedance value of the winding is calculated according to formula (1). The amplitude of the sweep frequency impedance is calculated according to formulas (2) and (3). and phase ;

[0009] (1)

[0010] (2)

[0011] (3)

[0012] in, It is the swept-frequency impedance of the winding under test, expressed in complex form. The unit representing the imaginary number. Let R be the frequency of the sweep signal, R be the real part of the sweep impedance, and X be the imaginary part of the sweep impedance. , These represent the amplitude and phase of the sweep impedance, respectively.

[0013] Step 3: Using the frequency of the sweep signal as... The phase response of the axis and the swept frequency impedance is The amplitude response of the axis and sweep frequency impedance is The axis forms a three-dimensional swept frequency impedance curve, which is then used as the fingerprint curve of the normal winding.

[0014] Step 4: After the transformer has been running for a period of time, under the same experimental conditions, repeat steps 1-3 to form a three-dimensional swept frequency impedance curve to be compared, and calculate the Euclidean distance of the mid-frequency band (100kHz-600kHz) between the curve to be compared and the fingerprint curve according to formula (4). Normalize the mid-frequency band Euclidean distance according to formula (5):

[0015] (4)

[0016] (5)

[0017] in This represents the actual Euclidean distance calculated, where N is the number of points swept in the mid-frequency band. and These represent the first and second fingerprint curves, respectively. The phase and amplitude values ​​corresponding to each point; and They represent the first and second curves in the curves to be compared. The phase and amplitude values ​​corresponding to each point; This is the normalized Euclidean distance. The mid-frequency Euclidean distance of the normal winding fingerprint curve;

[0018] Step 5: Compare and analyze the three-dimensional swept frequency impedance curve to be compared with the fingerprint curve. If the following characteristics appear:

[0019] 1) Normalized Euclidean distance between the three-dimensional swept impedance curve and the fingerprint curve in the mid-frequency band of 100kHz-600kHz Greater than , To determine the threshold for axial displacement faults in the winding;

[0020] 2) In the XY projection plane of the three-dimensional swept impedance curve, the overall resonant point of the curve shifts to the right, and the amplitude of the resonant point in the high-frequency band decreases.

[0021] 3) In the XZ projection plane of the three-dimensional swept impedance curve, the overall resonant point of the curve shifts to the right, and the amplitude of the resonant point in the high-frequency band increases.

[0022] This indicates that the transformer winding has experienced an axial displacement fault, and based on... The magnitude of the fault is used to estimate the extent of the axial displacement of the winding.

[0023] This invention provides a method for diagnosing axial displacement faults in transformer windings based on three-dimensional swept-frequency impedance curve analysis, with the following technical advantages:

[0024] 1) This method incorporates phase frequency information of the swept impedance into the original swept impedance amplitude curve, thereby constructing a three-dimensional swept impedance curve. The three-dimensional swept impedance curve contains more fault characteristic information, enabling the assessment and analysis of the transformer winding health status through comparative analysis of changes in the three-dimensional swept impedance curve.

[0025] 2) Compared with the original two-dimensional swept frequency impedance amplitude curve, this method has an additional parameter that reflects winding faults, which has higher sensitivity in diagnosing transformer winding axial displacement faults and improves the accuracy of transformer winding deformation diagnosis.

[0026] 3) This method can sensitively and effectively distinguish between the normal state of the winding and the axial displacement fault state by analyzing the resonant point offset and the resonant point amplitude change of the three-dimensional swept impedance curve in different frequency bands from different perspectives.

[0027] 4) The method of the present invention can effectively diagnose whether the transformer winding has an axial displacement fault, and can quantify the degree of deviation between the two curves by calculating the normalized Euclidean distance between the curve to be analyzed and the fingerprint curve in the mid-frequency band through mathematical index method, and thus assess the severity of the winding fault, providing a more reliable reference for transformer maintenance decisions. Attached Figure Description

[0028] Figure 1 This is a flowchart of the present invention.

[0029] Figure 2 This is the original two-dimensional swept frequency impedance curve when the transformer winding is in normal condition.

[0030] Figure 3(a) shows the perspective proposed in this invention. Three-dimensional sweep impedance curve at the specified time.

[0031] Figure 3(b) shows the perspective proposed in this invention. Three-dimensional sweep impedance curve at the specified time.

[0032] Figure 3(c) shows the perspective proposed in this invention. Three-dimensional sweep impedance curve at the specified time.

[0033] Figure 3(d) is a projection of the three-dimensional swept frequency impedance curve proposed in this invention onto the XY plane.

[0034] Figure 3(e) is a projection of the three-dimensional swept frequency impedance curve proposed in this invention onto the XZ plane.

[0035] Figure 4(a) shows the three-dimensional swept frequency impedance curves when the transformer windings experience axial displacement faults of different severity.

[0036] Figure 4(b) shows the projection of the three-dimensional swept frequency impedance curves on the XY plane when the transformer windings experience axial displacement faults of different severity.

[0037] Figure 4(c) shows the projection of the three-dimensional swept frequency impedance curve on the XZ plane when the transformer windings experience axial displacement faults of different severity. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and specific implementation process.

[0039] Figure 1 This is a flowchart of a method for diagnosing transformer winding axial displacement faults based on three-dimensional swept-frequency impedance curve analysis. Figure 1 It can be seen that the method includes the following steps:

[0040] Step 1: Short-circuit one side of the transformer winding with a wire, and connect a resistor with a resistance value of [value missing] to the beginning and end of the winding being tested. sampling resistor and A frequency of 1 Hz was injected at the beginning of the winding under test. A 1MHz sinusoidal sweep frequency signal;

[0041] Step 2: Measure the input voltage of the winding under test. Response voltage and the current of the winding under test The sweep frequency impedance value of the winding is calculated according to formula (1). The amplitude of the sweep frequency impedance is calculated according to formulas (2) and (3). and phase ;

[0042] (1)

[0043] (2)

[0044] (3)

[0045] in, It is the swept-frequency impedance of the winding under test, expressed in complex form. The unit representing the imaginary number. Let R be the frequency of the sweep signal, R be the real part of the sweep impedance, and X be the imaginary part of the sweep impedance. , These represent the amplitude and phase of the sweep impedance, respectively.

[0046] Step 3: Using the frequency of the sweep signal as... The phase response of the axis and the swept frequency impedance is The amplitude response of the axis and sweep frequency impedance is The axis forms a three-dimensional swept frequency impedance curve, which is then used as the fingerprint curve of the normal winding.

[0047] Step 4: After the transformer has been running for a period of time, under the same experimental conditions, repeat steps 1-3 to form a three-dimensional swept frequency impedance curve to be compared, and calculate the Euclidean distance of the mid-frequency band (100kHz-600kHz) between the curve to be compared and the fingerprint curve according to formula (4). Normalize the mid-frequency band Euclidean distance according to formula (5):

[0048] (4)

[0049] (5)

[0050] in This represents the actual Euclidean distance calculated, where N is the number of points swept in the mid-frequency band. and These represent the first and second fingerprint curves, respectively. The phase and amplitude values ​​corresponding to each point; and They represent the first and second curves in the curves to be compared. The phase and amplitude values ​​corresponding to each point; This is the normalized Euclidean distance. The mid-frequency Euclidean distance of the normal winding fingerprint curve;

[0051] In step 4, the normalized Euclidean distance It is a mathematical metric used to assess the degree of winding deformation faults. Normalized Euclidean distance. This represents the distance between the two consecutive three-dimensional swept impedance curves. The larger the value, the greater the deviation between the two curves, indicating a more severe fault. The closer the value is to 0, the smaller the deviation between the two curves, meaning the smaller the degree of failure.

[0052] Step 5: Compare and analyze the three-dimensional swept frequency impedance curve to be compared with the fingerprint curve. If the following characteristics appear:

[0053] 1) Normalized Euclidean distance between the three-dimensional swept impedance curve and the fingerprint curve in the mid-frequency band of 100kHz-600kHz Greater than , To determine the threshold for axial displacement faults in the winding;

[0054] 2) In the XY projection plane of the three-dimensional swept impedance curve, the overall resonant point of the curve shifts to the right, and the amplitude of the resonant point in the high-frequency band decreases.

[0055] 3) In the XZ projection plane of the three-dimensional swept impedance curve, the overall resonant point of the curve shifts to the right, and the amplitude of the resonant point in the high-frequency band increases.

[0056] This indicates that the transformer winding has experienced an axial displacement fault, and based on... The magnitude of the fault is used to estimate the extent of the axial displacement of the winding.

[0057] In step 5, the three-dimensional swept frequency impedance curve to be compared is compared and analyzed with the fingerprint curve. The results can be divided into the following three categories:

[0058] First, there are no physical faults in the transformer windings;

[0059] Second, an axial displacement fault occurred in the winding at a certain location of the transformer;

[0060] Third, the transformer experienced other types of winding deformation faults;

[0061] If there are no faults in the transformer windings, the three-dimensional swept frequency impedance curve constructed in step 4 will basically overlap with the fingerprint swept frequency impedance curve constructed in step 3, and will not show significant differences.

[0062] If an axial displacement fault occurs in the transformer winding, the parameter values ​​in the transformer equivalent model will change accordingly, causing the characteristics of the three-dimensional swept frequency impedance curve constructed in step 4 to change accordingly. The main manifestations are: (a) the normalized Euclidean distance between the three-dimensional swept frequency impedance curve and the fingerprint curve in the mid-frequency band. Greater than the judgment threshold , (a) The threshold for judging the axial displacement fault of the winding using the normalized Euclidean distance can be obtained by data when the winding has a small axial displacement fault. In this invention, it is set to 0.0814; (b) In the XY projection plane of the three-dimensional swept frequency impedance curve, the curve resonance point shifts to the right as a whole, and the amplitude of the high-frequency resonance point decreases; (c) In the XZ projection plane of the three-dimensional swept frequency impedance curve, the curve resonance point shifts to the right as a whole, and the amplitude of the high-frequency resonance point increases.

[0063] If other types of winding faults occur in the tested winding, the three-dimensional swept frequency impedance curve will show characteristics different from those used to determine axial displacement faults. This invention only addresses the case of axial displacement faults in transformer windings, so other types of winding faults will not be discussed here.

[0064] To further analyze the differences in the three-dimensional swept-frequency impedance curve characteristics between normal windings and windings with axial displacement faults, winding circuit models at low and high frequencies were established in the circuit simulation software PSpice for a specific transformer model. The parameters of the low-frequency model were obtained through transformer open-circuit and short-circuit experiments, while the parameters of the high-frequency model were obtained through finite element analysis. The winding in the high-frequency model had 10 winding sections. Simulations were performed on normal windings and windings with different degrees of axial displacement faults, and the characteristic changes of the constructed three-dimensional swept-frequency impedance curves were compared and analyzed.

[0065] contrast Figure 2 As shown in Figures 3(a), 3(b), and 3(c), the three-dimensional swept impedance curve extends the original two-dimensional plane to three-dimensional space, allowing for different curve views to be observed from different perspectives, and enabling the extraction of more curve feature information from the three-dimensional curve.

[0066] contrast Figure 2 As shown in Figures 3(d) and 3(e), the projection of the three-dimensional swept impedance curve onto the XY plane is the phase frequency curve of the swept impedance, and its projection onto the YZ plane is the amplitude frequency curve of the swept impedance, which is the original two-dimensional swept impedance curve. Since the phase frequency curve also changes when the winding is deformed, the three-dimensional swept impedance curve has higher sensitivity in reflecting winding faults.

[0067] Comparing Figures 4(a), 4(b), and 4(c), it can be seen that when the transformer winding experiences axial displacement faults of varying degrees, the three-dimensional swept-frequency impedance curve and the fingerprint curve exhibit different characteristic changes. Based on these changes, the axial displacement fault of the winding can be diagnosed. Compared with the original two-dimensional swept-frequency impedance curve, the changes in the three-dimensional swept-frequency impedance curve are more obvious, and the curve's change characteristics can be extracted from multiple perspectives and projection planes, which will increase the accuracy of winding fault judgment. In the three-dimensional swept-frequency impedance curve and its XY and XZ projection planes, windings with different degrees of axial displacement faults show obvious characteristic differences from the fingerprint curve. Based on these characteristic changes in the curve, the identification of axial displacement faults and the calculation of fault severity can be achieved.

[0068] For the specific transformer winding model established, taking a 10% axial displacement fault in the winding as an example, the characteristic changes of the three-dimensional swept frequency impedance curve are as follows:

[0069] a) Normalized Euclidean distance between the three-dimensional swept impedance curve and the fingerprint curve in the mid-frequency range of 100kHz-600kHz. ;

[0070] b) In the XY projection plane of the three-dimensional swept impedance curve, the second resonant point of the curve shifts to the right by approximately 5000Hz, and the amplitude decreases by approximately... The last resonant point of the curve shifted to the right by approximately 3724 Hz, and the amplitude decreased by approximately...

[0071] c) In the XZ projection plane of the three-dimensional swept impedance curve, the second resonant point of the curve shifts to the right by approximately 5200 Hz, and the amplitude increases by approximately... The rightward shift of the last resonant point of the curve is approximately 50 Hz, while its amplitude increases by approximately... ;

[0072] By analyzing the three-dimensional swept frequency impedance curve and its curve characteristics on different projection planes, the axial displacement fault of the transformer winding can be identified.

[0073] On the other hand, the normalized Euclidean distance between the three-dimensional swept impedance curve and the fingerprint curve increases with the degree of fault. For example, the normalized Euclidean distance when a 30% axial displacement fault occurs in the winding... Meanwhile, the changes in the resonant points of the three-dimensional swept impedance curve in the XY and YZ projection planes also increase with the severity of the winding fault. Therefore, by quantitatively calculating characteristic parameters such as the normalized Euclidean distance between the three-dimensional swept impedance curve and the fingerprint curve, the magnitude of the resonant point offset, and the magnitude of the resonant point amplitude change, the severity of the winding axial displacement fault can be predicted.

Claims

1. A method for diagnosing axial displacement faults in transformer windings based on three-dimensional swept-frequency impedance curve analysis, characterized in that... Includes the following steps: Step 1: Short-circuit one side of the transformer winding with a wire, and connect a resistor with a resistance value of [value missing] to the beginning and end of the winding being tested. sampling resistor and A frequency of 1 Hz was injected at the beginning of the winding under test. A 1MHz sinusoidal sweep frequency signal; Step 2: Measure the input voltage of the winding under test. Response voltage and the current of the winding under test The sweep frequency impedance value of the winding is calculated according to formula (1). The amplitude of the sweep frequency impedance is calculated according to formulas (2) and (3). and phase ; （1） （2） （3） in, It is the swept-frequency impedance of the winding under test, expressed in complex form. The unit representing the imaginary number. Let R be the frequency of the sweep signal, R be the real part of the sweep impedance, and X be the imaginary part of the sweep impedance. , These represent the amplitude and phase of the sweep impedance, respectively. Step 3: Using the frequency of the sweep signal as... The phase response of the axis and the swept frequency impedance is The amplitude response of the axis and sweep frequency impedance is The axis forms a three-dimensional swept frequency impedance curve, which is then used as the fingerprint curve of the normal winding. Step 4: After the transformer has been running for a period of time, under the same experimental conditions, repeat steps 1-3 to form a three-dimensional swept frequency impedance curve to be compared, and calculate the Euclidean distance of the mid-frequency band (100kHz-600kHz) between the curve to be compared and the fingerprint curve according to formula (4). Normalize the mid-frequency band Euclidean distance according to formula (5): （4） （5） in This represents the actual Euclidean distance calculated, where N is the number of points swept in the mid-frequency band. and These represent the first and second fingerprint curves, respectively. The phase and amplitude values ​​corresponding to each point; and They represent the first and second curves in the curves to be compared. The phase and amplitude values ​​corresponding to each point; This is the normalized Euclidean distance. The mid-frequency Euclidean distance of the normal winding fingerprint curve; Step 5: Compare and analyze the three-dimensional swept frequency impedance curve to be compared with the fingerprint curve. If the following characteristics appear: 1) Normalized Euclidean distance between the three-dimensional swept impedance curve and the fingerprint curve in the mid-frequency band of 100kHz-600kHz Greater than , To determine the threshold for axial displacement faults in the winding; 2) In the XY projection plane of the three-dimensional swept impedance curve, the overall resonant point of the curve shifts to the right, and the amplitude of the resonant point in the high-frequency band decreases. 3) In the XZ projection plane of the three-dimensional swept impedance curve, the overall resonant point of the curve shifts to the right, and the amplitude of the resonant point in the high-frequency band increases. This indicates that the transformer winding has experienced an axial displacement fault, and based on... The magnitude of the fault is used to estimate the extent of the axial displacement of the winding.

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