CN114355007A - Oil-immersed transformer deformation diagnosis method based on self-oscillation - Google Patents
Oil-immersed transformer deformation diagnosis method based on self-oscillation Download PDFInfo
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- CN114355007A CN114355007A CN202111459468.3A CN202111459468A CN114355007A CN 114355007 A CN114355007 A CN 114355007A CN 202111459468 A CN202111459468 A CN 202111459468A CN 114355007 A CN114355007 A CN 114355007A
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Abstract
The oil-immersed transformer is one of important devices of an electric power system and is used for measuring and protecting the electric power system, and the degree of deformation of the oil-immersed transformer directly influences the functions of the oil-immersed transformer. The invention discloses a deformation diagnosis method of an oil-immersed transformer based on self-oscillation. Firstly, measuring an oscillation wave signal of the oil-immersed transformer, then processing the oscillation wave signal to convert the oscillation wave signal into a time-frequency diagram, extracting a characteristic parameter of deformation of the oil-immersed transformer from the time-frequency diagram, and finally evaluating the deformation degree of the oil-immersed transformer based on the characteristic parameter.
Description
Technical Field
The invention belongs to the field of performance evaluation of oil-immersed transformers, and particularly relates to a deformation diagnosis method of an oil-immersed transformer based on self-oscillation.
Background
With the development of modern power system technology, the oil-immersed transformer is used more frequently. During transport or operation of the device, however, the windings inside the transformer may be deformed, the winding is positioned in the oil-immersed transformer, the occurrence of deformation can not be directly observed, the winding deformation can cause the damage of insulating materials, the insulation strength is reduced, the mechanical performance of the oil-immersed transformer is reduced, the faults of the transformer are increased, the normal operation of a power system can be influenced seriously, common winding deformation diagnosis methods comprise a short-circuit impedance method, a capacitance variation method, a frequency response method and the like, but the short-circuit impedance method has long detection time, needs off-line test, cannot judge the deformation condition of the winding during operation, has simple operation, however, the method can only judge the severe deformation condition, the frequency response method is insensitive to the detection of the slight deformation of the winding, and a method capable of detecting the slight deformation of the oil-immersed transformer on line is needed.
Disclosure of Invention
In order to overcome the defects of the background art, the invention provides a method for deformation diagnosis of an oil-immersed transformer, which can effectively and accurately evaluate the deformation degree of the oil-immersed transformer, and comprises the following steps:
firstly, measuring an oscillation wave signal of the oil-immersed transformer
An experimental platform for testing oscillatory wave signals is set up and mainly comprises (1) a high-voltage direct-current power supply, (2) a protective resistor, (3) a high-frequency switch, (4) an inductor, (5) an oil-immersed transformer, wherein the experimental platform comprises (6) a porcelain sleeve, (7) a winding and (8) an iron core, the tail end of the transformer is connected with (9) a terminal, (10) the resistor, (11) the capacitor, (10) the resistor and (11) the capacitor form a resistance-capacitance voltage division circuit, (1) the high-frequency direct-current power supply (2) the protective resistor, (4) the inductor is connected with a signal detection device (5) the oil-immersed transformer after being connected in series, (5) the oil-immersed transformer and (4) the inductor form an LC damping oscillation circuit, (3) the high-frequency switch is led out from the protective resistor and (4) the inductor and is grounded, and the oil-immersed transformer is firstly connected with the resistor and (10) the capacitor to form the resistance-capacitance voltage division circuit, then is connected with a terminal of the signal collecting device (9); when the test is started, a high-voltage direct-current power supply (1) is turned off, an oil-immersed transformer (5) is grounded through a high-frequency switch (3) to be fully discharged, the high-frequency switch (3) is in a disconnected state after the full discharge, the high-voltage direct-current power supply (1) is turned on, the high-voltage direct-current power supply (1) transmits an electric signal into the oil-immersed transformer (5) through a protection resistor (2) and an inductor (4), the voltage of the high-voltage direct-current power supply (1) is gradually increased from 0V, the generated electric signal is transmitted into a winding (7) of the oil-immersed transformer (5) through the winding (7) at the other end, the electric signal is output to a terminal (9) through a protection circuit formed by a resistor (10) and a capacitor (11), and an oscillation-free electric signal is obtained; then closing the high-frequency switch (3), grounding the high-frequency switch (3), and collecting an oscillation wave voltage signal on a terminal (9);
secondly, the oscillation wave signal is converted into a time-frequency diagram
Normalizing the collected oscillation wave signals, wherein the calculation formula between the normalized signals f (t) and the original signals X (t) is as follows:
converting the signal image into a time-frequency image by using short-time Fourier transform, and performing gray scale conversion on the time-frequency image to obtain an oscillation wave signal gray scale frequency spectrum image y (i, j), wherein the image size is 256 multiplied by 256, and y (i, j) is an oscillation wave signal gray scale frequency spectrum image pixel value;
thirdly, extracting the characteristic parameters of the deformation of the oil-immersed transformer
The 256 × 256 pixel matrix after the gray conversion is y (i, j), the input image is normalized by the gray space correction method, the pixel matrix is normalized first, the obtained matrix is h (i, j), and the calculation formula is satisfied:
i, j are coordinates of the pixel matrix, max (h (i, j) is a maximum value of the gray scale spectrum image pixel values, and min (h (i, j) is a minimum value of the gray scale spectrum image pixel values;
the calculation formula of the matrix G (i, j) obtained after the matrix is subjected to pre-compensation processing is as follows:
g (i, j) is a matrix after pre-compensation processing, η is a pre-compensation coefficient, η is 2.2, and the formula of G (i, j) is as follows:
calculating a characteristic matrix, wherein the expression is as follows:
let | λ E-Gi,jI is 0, and the characteristic value lambda of the matrix is obtained after matrix transformation1，λ2，λ3，…，λ256；
And recording a matrix formed by the characteristic values as L, and calculating the formula as follows:
L＝(λ1,λ2,λ3...λ256)T (6)
calculating a weighting matrix M according to the following formula:
M＝(M1,M2,M3...M256)T (8)
calculating a deformation characteristic parameter gamma of the oil-immersed transformer, wherein the calculation formula is as follows:
γ＝LT·M (9)
and (3) calculating a deformation evaluation coefficient epsilon of the oil-immersed transformer, wherein the calculation formula is as follows:
γnfor a detected deformation characteristic parameter, gamma, of the oil-immersed transformer0The deformation characteristic parameter of the oil immersed transformer is normal;
fourthly, evaluating the deformation degree of the oil-immersed transformer
The deformation degree of the oil-immersed transformer is evaluated by the deformation evaluation coefficient epsilon of the oil-immersed transformer obtained through calculation, if epsilon is more than 0.8 and less than 1.25, the fact that no deformation or deformation of a winding in the oil-immersed transformer is not obvious is indicated, the function of the oil-immersed transformer is not affected, and if epsilon is more than 1.25 or epsilon is less than 0.8, the fact that the deformation of the winding in the oil-immersed transformer is serious is indicated, the operation of a power system is greatly affected, and the maintenance or the replacement needs to be carried out at once.
Drawings
FIG. 1 is a flow chart of a deformation diagnosis method for an oil-immersed transformer based on self-oscillation
FIG. 2 is a schematic diagram of a test platform for oscillating wave signals of an oil-immersed transformer
Detailed Description
The following is further detailed with reference to the accompanying drawings, and the specific method steps are as follows:
firstly, measuring an oscillation wave signal of the oil-immersed transformer
An experimental platform for testing oscillatory wave signals is set up and mainly comprises (1) a high-voltage direct-current power supply, (2) a protective resistor, (3) a high-frequency switch, (4) an inductor, (5) an oil-immersed transformer, wherein the experimental platform comprises (6) a porcelain sleeve, (7) a winding and (8) an iron core, the tail end of the transformer is connected with (9) a terminal, (10) the resistor, (11) the capacitor, (10) the resistor and (11) the capacitor form a resistance-capacitance voltage division circuit, (1) the high-frequency direct-current power supply (2) the protective resistor, (4) the inductor is connected with a signal detection device (5) the oil-immersed transformer after being connected in series, (5) the oil-immersed transformer and (4) the inductor form an LC damping oscillation circuit, (3) the high-frequency switch is led out from the protective resistor and (4) the inductor and is grounded, and the oil-immersed transformer is firstly connected with the resistor and (10) the capacitor to form the resistance-capacitance voltage division circuit, then is connected with a terminal of the signal collecting device (9); when the test is started, a high-voltage direct-current power supply (1) is turned off, an oil-immersed transformer (5) is grounded through a high-frequency switch (3) to be fully discharged, the high-frequency switch (3) is in a disconnected state after the full discharge, the high-voltage direct-current power supply (1) is turned on, the high-voltage direct-current power supply (1) transmits an electric signal into the oil-immersed transformer (5) through a protection resistor (2) and an inductor (4), the voltage of the high-voltage direct-current power supply (1) is gradually increased from 0V, the generated electric signal is transmitted into a winding (7) of the oil-immersed transformer (5) through the winding (7) at the other end, the electric signal is output to a terminal (9) through a protection circuit formed by a resistor (10) and a capacitor (11), and an oscillation-free electric signal is obtained; then closing the high-frequency switch (3), grounding the high-frequency switch (3), and collecting an oscillation wave voltage signal on a terminal (9);
secondly, the oscillation wave signal is converted into a time-frequency diagram
Normalizing the collected oscillation wave signals, wherein the calculation formula between the normalized signals f (t) and the original signals X (t) is as follows:
converting the signal image into a time-frequency image by using short-time Fourier transform, and performing gray scale conversion on the time-frequency image to obtain an oscillation wave signal gray scale frequency spectrum image y (i, j), wherein the image size is 256 multiplied by 256, and y (i, j) is an oscillation wave signal gray scale frequency spectrum image pixel value;
thirdly, extracting the characteristic parameters of the deformation of the oil-immersed transformer
The 256 × 256 pixel matrix after the gray conversion is y (i, j), the input image is normalized by the gray space correction method, the pixel matrix is normalized first, the obtained matrix is h (i, j), and the calculation formula is satisfied:
i, j are coordinates of the pixel matrix, max (h (i, j) is a maximum value of the gray scale spectrum image pixel values, and min (h (i, j) is a minimum value of the gray scale spectrum image pixel values;
the calculation formula of the matrix G (i, j) obtained after the matrix is subjected to pre-compensation processing is as follows:
g (i, j) is a matrix after pre-compensation processing, η is a pre-compensation coefficient, η is 2.2, and the formula of G (i, j) is as follows:
calculating a characteristic matrix, wherein the expression is as follows:
let | λ E-Gi,jI is 0, and the characteristic value lambda of the matrix is obtained after matrix transformation1，λ2，λ3，…，λ256；
And recording a matrix formed by the characteristic values as L, and calculating the formula as follows:
L＝(λ1,λ2,λ3...λ256)T (6)
calculating a weighting matrix M according to the following formula:
M＝(M1,M2,M3...M256)T (8)
calculating a deformation characteristic parameter gamma of the oil-immersed transformer, wherein the calculation formula is as follows:
γ＝LT·M (9)
and (3) calculating a deformation evaluation coefficient epsilon of the oil-immersed transformer, wherein the calculation formula is as follows:
γnfor a detected deformation characteristic parameter, gamma, of the oil-immersed transformer0The deformation characteristic parameter of the oil immersed transformer is normal;
fourthly, evaluating the deformation degree of the oil-immersed transformer
The deformation degree of the oil-immersed transformer is evaluated by the deformation evaluation coefficient epsilon of the oil-immersed transformer obtained through calculation, if epsilon is more than 0.8 and less than 1.25, the fact that no deformation or deformation of a winding in the oil-immersed transformer is not obvious is indicated, the function of the oil-immersed transformer is not affected, and if epsilon is more than 1.25 or epsilon is less than 0.8, the fact that the deformation of the winding in the oil-immersed transformer is serious is indicated, the operation of a power system is greatly affected, and the maintenance or the replacement needs to be carried out at once.
Claims (1)
1. A deformation diagnosis method for an oil-immersed transformer based on self-oscillation is characterized by comprising the following steps:
firstly, measuring an oscillation wave signal of the oil-immersed transformer
An experimental platform for testing oscillatory wave signals is set up, which mainly comprises (1) a high-voltage direct-current power supply, (2) a protective resistor, (3) a high-frequency switch and (4) an inductor, (5) the oil immersed transformer comprises (6) a porcelain bushing, (7) a winding and (8) an iron core, wherein the tail end of the porcelain bushing, (7) a terminal (9), (10) a resistor, (11) a capacitor, (10) the resistor and the capacitor (11) form a resistance-capacitance voltage division circuit, (1) a high-frequency direct current power supply (2) a protective resistor, (4) the inductor is connected with a signal detection device (5) the oil immersed transformer after being connected in series, (5) the oil immersed transformer and the inductor (4) form an LC damping oscillation circuit, (3) a high-frequency switch is led out from the protective resistor (2) and the inductor (4) and is grounded, (5) the oil immersed transformer is firstly connected with the resistor (10) and the capacitor (11) to form the resistance-capacitance voltage division circuit and then is connected with the terminal of a signal collection device (9); when the test is started, a high-voltage direct-current power supply (1) is turned off, an oil-immersed transformer (5) is grounded through a high-frequency switch (3) to be fully discharged, the high-frequency switch (3) is in a disconnected state after the full discharge, the high-voltage direct-current power supply (1) is turned on, the high-voltage direct-current power supply (1) transmits an electric signal into the oil-immersed transformer (5) through a protection resistor (2) and an inductor (4), the voltage of the high-voltage direct-current power supply (1) is gradually increased from 0V, the generated electric signal is transmitted into a winding (7) of the oil-immersed transformer (5) through the winding (7) at the other end, the electric signal is output to a terminal (9) through a protection circuit formed by a resistor (10) and a capacitor (11), and an oscillation-free electric signal is obtained; then closing the high-frequency switch (3), grounding the high-frequency switch (3), and collecting an oscillation wave voltage signal on a terminal (9);
secondly, the oscillation wave signal is converted into a time-frequency diagram
Normalizing the collected oscillation wave signals, wherein the calculation formula between the normalized signals f (t) and the original signals X (t) is as follows:
converting the signal image into a time-frequency image by using short-time Fourier transform, and performing gray scale conversion on the time-frequency image to obtain an oscillation wave signal gray scale frequency spectrum image y (i, j), wherein the image size is 256 multiplied by 256, and y (i, j) is an oscillation wave signal gray scale frequency spectrum image pixel value;
thirdly, extracting the characteristic parameters of the deformation of the oil-immersed transformer
The 256 × 256 pixel matrix after the gray conversion is y (i, j), the input image is normalized by the gray space correction method, the pixel matrix is normalized first, the obtained matrix is h (i, j), and the calculation formula is satisfied:
i, j are coordinates of the pixel matrix, max (h (i, j) is a maximum value of the gray scale spectrum image pixel values, and min (h (i, j) is a minimum value of the gray scale spectrum image pixel values;
the calculation formula of the matrix G (i, j) obtained after the matrix is subjected to pre-compensation processing is as follows:
g (i, j) is a matrix after pre-compensation processing, η is a pre-compensation coefficient, η is 2.2, and the formula of G (i, j) is as follows:
calculating a characteristic matrix, wherein the expression is as follows:
let | λ E-Gi,jI is 0, and the characteristic value lambda of the matrix is obtained after matrix transformation1，λ2，λ3，…，λ256；
And recording a matrix formed by the characteristic values as L, and calculating the formula as follows:
L＝(λ1,λ2,λ3...λ256)T (6)
calculating a weighting matrix M according to the following formula:
M＝(M1,M2,M3...M256)T (8)
calculating a deformation characteristic parameter gamma of the oil-immersed transformer, wherein the calculation formula is as follows:
γ＝LT·M (9)
and (3) calculating a deformation evaluation coefficient epsilon of the oil-immersed transformer, wherein the calculation formula is as follows:
γnfor a detected deformation characteristic parameter, gamma, of the oil-immersed transformer0The deformation characteristic parameter of the oil immersed transformer is normal;
fourthly, evaluating the deformation degree of the oil-immersed transformer
The deformation degree of the oil-immersed transformer is evaluated by the deformation evaluation coefficient epsilon of the oil-immersed transformer obtained through calculation, if epsilon is more than 0.8 and less than 1.25, the fact that no deformation or deformation of a winding in the oil-immersed transformer is not obvious is indicated, the function of the oil-immersed transformer is not affected, and if epsilon is more than 1.25 or epsilon is less than 0.8, the fact that the deformation of the winding in the oil-immersed transformer is serious is indicated, the operation of a power system is greatly affected, and the maintenance or the replacement needs to be carried out at once.
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