Transformer partial discharge location method and device based on bushing CT acquisition

Abstract

The present invention provides a method and device for locating transformer partial discharge based on bushing CT data acquisition. The method comprises: acquiring high-frequency partial discharge pulse signals from current transformers at the transformer bushings; removing background noise from the pulse signals and performing amplitude correction to obtain corrected pulse signals; determining whether the partial discharge is caused by external interference or internal partial discharge based on the polarity distribution of the corrected pulse signals; if the partial discharge is caused by external interference, comparing the amplitudes of the corrected acquired signals corresponding to each bushing; the location corresponding to the current transformer with the largest amplitude is the location where the interference source was injected; and if the partial discharge is caused by internal transformer partial discharge, calculating the distance ratio from the partial discharge location to the winding head end based on the attenuation characteristics of the pulse signal propagating through the windings, combined with a pre-injected calibration square wave signal, to determine the discharge location. The present invention simplifies the method for locating transformer partial discharge, facilitates rapid identification of external interference and internal partial discharge signals, and prevents malfunction of protective devices.

Description

Technical Field

[0001] The present invention relates to the technical field of transformer discharge positioning in a power system, and in particular to a transformer partial discharge positioning method and device based on bushing CT acquisition. Background Art

[0002] Transformers are crucial equipment in power systems, and their safe and stable operation is crucial to their overall operation. Partial discharge (PD), a major cause of transformer failure, is a key method for detecting the insulation condition of transformers. When PD occurs in a transformer, the most pressing issue is determining its location and whether the signal originates from within the transformer.

[0003] Existing transformer partial discharge locating methods primarily include ultrasonic positioning, ultra-high frequency (UHF) signal positioning, and high-frequency multi-terminal detection technology. The ultrasonic positioning method uses ultrasonic sensors to receive the ultrasonic signals generated by partial discharge. Using the time difference between each sensor receiving the signal, the corresponding equations are solved to determine the specific coordinates of the partial discharge location. The ultra-high frequency positioning method uses an antenna to receive the ultra-high frequency electromagnetic signals generated by partial discharge within the transformer, combining arrival time and amplitude attenuation differences to achieve positioning. The principle of high-frequency multi-terminal detection technology is that high-frequency partial discharge pulses generated in multiple windings of the transformer propagate to the head and end of each terminal, forming a partial discharge monitoring network. By simultaneously measuring high-frequency partial discharge pulse signals at multiple terminals and comparing characteristic information such as the partial discharge pulse amplitude and polarity, it is possible to distinguish external interference and determine the type and location of partial discharge.

[0004] However, while ultrasonic positioning has good resistance to electromagnetic interference, it has low sensitivity for detecting internal transformer discharges and results in large errors in the equations it solves. Ultra-high frequency (UHF) positioning is susceptible to interference from on-site UHF electromagnetic signals, placing high demands on receiving devices such as antennas. Furthermore, it also requires solving equations, which limits positioning accuracy. Finally, current high-frequency multi-terminal detection technology uses high-frequency current sensors connected to the bushing end screen to measure partial discharge signals. This device lacks reliability, suffers from severe electromagnetic interference, and exhibits high signal attenuation, which reduces reception performance. Summary of the Invention

[0005] In view of this, the present invention provides a transformer partial discharge location method and device based on bushing CT acquisition to solve at least one of the above-mentioned problems.

[0006] In order to achieve the above object, the present invention adopts the following scheme:

[0007] According to a first aspect of the present invention, a transformer partial discharge location method based on bushing CT acquisition is provided, the method comprising: acquiring a high-frequency partial discharge pulse signal from a current transformer secondary terminal of a transformer bushing, the transformer bushing comprising a high-voltage side bushing, a medium-voltage side bushing, a neutral point bushing, a low-voltage side head-end bushing, and a low-voltage side terminal bushing; performing discrete wavelet decomposition on the high-frequency partial discharge pulse signal to obtain wavelet coefficients; selecting a soft threshold function to perform threshold processing on the wavelet coefficients to remove background noise; reconstructing a signal using the wavelet coefficients after removing the background noise, to obtain the high-frequency partial discharge pulse signal after removing the background noise; and based on the The frequency response characteristics of the current transformer are used to perform amplitude correction on the high-frequency partial discharge pulse signal after background noise removal to obtain a corrected pulse signal; based on the polarity distribution law of the corrected pulse signal, it is determined whether the transformer partial discharge belongs to external interference or internal partial discharge; if it is determined to be external interference, the amplitudes of the corrected acquisition signals corresponding to each bushing are compared, and the position corresponding to the bushing current transformer with the largest amplitude is the interference source injection position; if it is determined to be internal partial discharge of the transformer, the distance ratio from the partial discharge position to the winding head end is calculated according to the attenuation characteristics of the high-frequency pulse signal propagating in the winding, combined with the pre-injected calibration square wave signal, to determine the discharge position.

[0008] As an embodiment of the present invention, the above method includes performing amplitude correction on the high-frequency partial discharge pulse signal after background noise removal based on the frequency response characteristics of each bushing current transformer, which includes: injecting a calibration pulse signal into the end of any selected bushing of the transformer and calculating the spectrum of the calibration pulse signal; collecting the induced signal at the secondary port of the selected bushing and calculating the spectrum of the induced signal; calculating the frequency response of the selected bushing using the spectrum of the calibration pulse signal and the spectrum of the induced signal; calculating the spectrum of the high-frequency partial discharge pulse signal of the selected bushing; calculating the spectrum of the original pulse transmitted to the selected bushing using the spectrum of the high-frequency partial discharge pulse signal and the frequency response; obtaining a time domain signal through an inverse discrete Fourier transform based on the spectrum of the original pulse; taking the modulus of the time domain signal and finding the maximum value to obtain a corrected amplitude.

[0009] As an embodiment of the present invention, the above method determines whether the transformer partial discharge is external interference or internal partial discharge based on the polarity distribution law of the modified pulse signal, including: determining whether the polarities of the modified pulse signals corresponding to each bushing are the same; if they are the same, determining that the transformer partial discharge is external interference; if they are not the same, determining that the transformer partial discharge is internal partial discharge of the transformer.

[0010] As an embodiment of the present invention, the above method calculates the distance ratio from the partial discharge position to the winding head end based on the attenuation characteristics of the high-frequency pulse signal propagating in the winding, combined with a pre-injected calibration square wave signal, to determine the discharge position, including: before the partial discharge detection test begins, injecting a calibration square wave signal with the same charge amount into the head end and the tail end of the winding to be tested, respectively, to obtain the electric field strength at the head end and the tail end of the winding to be tested; based on the electric field strength, obtaining the electromagnetic energy of the high-frequency partial discharge pulse signal collected at the head end and the tail end bushing of the winding to be tested; based on the length of the winding to be tested, the electromagnetic energy, and the electric field strength amplitude of the high-frequency pulse at the partial discharge location, obtaining the signal energy at the head end and the tail end of the winding to be tested; and based on the electromagnetic energy and the signal energy, obtaining the distance ratio from the partial discharge position to the winding head end, thereby determining the discharge position.

[0011] According to a second aspect of the present invention, a transformer partial discharge positioning device based on bushing CT acquisition is provided, the device comprising: a signal acquisition unit for collecting high-frequency partial discharge pulse signals from the secondary-side terminals of the current transformer of the transformer bushing, the transformer bushing comprising a high-voltage side bushing, a medium-voltage side bushing, a neutral point bushing, a low-voltage side head-end bushing, and a low-voltage side terminal bushing; a wavelet decomposition unit for performing discrete wavelet decomposition on the high-frequency partial discharge pulse signals to obtain wavelet coefficients; a denoising unit for selecting a soft threshold function to perform threshold processing on the wavelet coefficients to remove background noise; a signal reconstruction unit for reconstructing a signal using the wavelet coefficients after removing the background noise to obtain the high-frequency partial discharge pulse signals after removing the background noise; and an amplitude correction unit for reconstructing a signal based on the current transformer of each bushing. The high-frequency partial discharge pulse signal after background noise removal is corrected by the frequency response characteristics of the sensor to obtain a corrected pulse signal; a discharge type judgment unit is used to judge whether the transformer partial discharge belongs to external interference or internal partial discharge based on the polarity distribution law of the corrected pulse signal; a first positioning unit is used to compare the amplitudes of the corrected acquisition signals corresponding to each bushing when the discharge type judgment unit determines that it is external interference, and the position corresponding to the bushing current transformer with the largest amplitude is the interference source injection position; a second positioning unit is used to determine the discharge position by calculating the distance ratio from the partial discharge position to the winding head end according to the attenuation characteristics of the high-frequency pulse signal propagating in the winding, combined with the pre-injected calibration square wave signal, when the discharge type judgment unit determines that it is internal partial discharge of the transformer.

[0012] As one embodiment of the present invention, the amplitude correction unit includes: a first spectrum calculation module, which injects a calibration pulse signal into the end of any selected bushing of the transformer and calculates the spectrum of the calibration pulse signal; a second spectrum calculation module, which is used to collect the induced signal at the secondary side port of the selected bushing and calculate the spectrum of the induced signal; a frequency response calculation module, which is used to calculate the frequency response of the selected bushing using the spectrum of the calibration pulse signal and the spectrum of the induced signal; a third spectrum calculation module, which is used to calculate the spectrum of the high-frequency partial discharge pulse signal of the selected bushing; a fourth spectrum calculation module, which is used to inversely deduce the spectrum of the original pulse transmitted to the selected bushing using the spectrum of the high-frequency partial discharge pulse signal and the frequency response; an inverse transformation module, which is used to obtain a time domain signal through an inverse discrete Fourier transform based on the spectrum of the original pulse; and an amplitude correction module, which is used to modulo the time domain signal and find the maximum value to obtain a corrected amplitude.

[0013] As an embodiment of the present invention, the above-mentioned discharge type judgment unit is specifically used to: judge whether the polarities of the corrected pulse signals corresponding to each bushing are the same; if they are the same, it is judged that the partial discharge of the transformer is due to external interference; if they are not the same, it is judged that the partial discharge of the transformer is due to internal partial discharge of the transformer.

[0014] As an embodiment of the present invention, the above-mentioned second positioning unit includes: an electric field strength acquisition module, which is used to inject a calibrated square wave signal with the same charge amount into the beginning and end of the winding to be tested before the start of the partial discharge detection test, so as to obtain the electric field strength at the beginning and end of the winding to be tested; an electromagnetic energy acquisition module, which is used to obtain the electromagnetic energy of the high-frequency partial discharge pulse signal collected at the beginning and end bushings of the winding to be tested based on the electric field strength; a signal energy acquisition module, which is used to obtain the signal energy at the beginning and end of the winding to be tested based on the length of the winding to be tested, the electromagnetic energy and the electric field strength amplitude of the high-frequency pulse at the partial discharge location; and a discharge position determination module, which is used to obtain the distance ratio from the partial discharge position to the beginning of the winding based on the electromagnetic energy and the signal energy, and then determine the discharge position.

[0015] According to a third aspect of the present invention, an electronic device is provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above method when executing the computer program.

[0016] According to a fourth aspect of the present invention, there is provided a computer-readable storage medium having a computer program stored thereon, wherein the computer program implements the steps of the above method when executed by a processor.

[0017] According to a fifth aspect of the present invention, there is provided a computer program product comprising a computer program / instructions, which implement the steps of the above method when executed by a processor.

[0018] The transformer partial discharge positioning method and device based on bushing CT acquisition proposed in the present invention reduces the interference factor of background noise, eliminates the influence of the bushing current transformer on the reception of high-frequency partial discharge pulse signals, and simplifies the method for determining the location of transformer partial discharge. Specifically, through polarity discrimination, it helps to quickly identify external interference and internal partial discharge signals, avoid malfunction of protection devices, and provide a basis for fault analysis and maintenance work. For external interference, the injection location of the interference source can be directly determined by comparing the signal amplitudes of each bushing current transformer. For internal discharge, the attenuation characteristics of the high-frequency pulse signal in the winding are utilized, combined with the calibration signal, to calculate the distance ratio from the discharge point to the winding head end, thereby achieving precise positioning. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0020] Figure 1 This is a flow chart of a transformer partial discharge location method based on bushing CT acquisition provided in an embodiment of the present application;

[0021] Figure 2 This is a wiring diagram for collecting high-frequency partial discharge pulse signals provided by an embodiment of the present application;

[0022] Figure 3 This is a schematic diagram of a flow chart for performing amplitude correction on a high-frequency partial discharge pulse signal provided by an embodiment of the present application;

[0023] Figure 4 Schematic diagram of the polarity of the windings of the transformer provided by the embodiment of the present application when it is subject to external interference;

[0024] Figure 5 Schematic diagram of the polarity of the windings during partial discharge inside the transformer provided by an embodiment of the present application;

[0025] Figure 6 This is a schematic diagram of the winding discharge point positioning provided by an embodiment of the present application;

[0026] Figure 7 1 is a flow chart of calculating the distance ratio from the partial discharge position to the winding head end provided in an embodiment of the present application;

[0027] Figure 8 1 is a schematic structural diagram of a transformer partial discharge locating device based on bushing CT acquisition provided in an embodiment of the present application;

[0028] Figure 9 Schematic diagram of the structure of the amplitude correction unit provided in an embodiment of the present application;

[0029] Figure 10 is a structural diagram of a second positioning unit provided in an embodiment of the present application;

[0030] Figure 11 It is a structural diagram of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0031] To make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the embodiments of the present invention are further described in detail below with reference to the accompanying drawings. Here, the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0032] Among the existing transformer partial discharge locating methods, the ultrasonic locating method has a low sensitivity to detecting internal discharge in the transformer, resulting in large errors in solving the equation set. The ultra-high frequency locating method is easily interfered with by ultra-high frequency electromagnetic signals on site, places high demands on receiving devices such as antennas, and also requires solving the equation set, which limits the accuracy of positioning. The high-frequency multi-terminal detection technology uses a high-frequency current sensor drawn from the end screen of the bushing to measure the partial discharge signal. The device has insufficient reliability, severe electromagnetic interference, and high signal attenuation, which reduces the receiving performance. Therefore, the purpose of this application is to provide a transformer partial discharge locating method and device that can quickly identify external interference and internal partial discharge signals, is not subject to electromagnetic interference, and accurately locates the discharge position.

[0033] like Figure 1 FIG2 is a flow chart of a transformer partial discharge location method based on bushing CT acquisition provided by an embodiment of the present application. The method includes the following steps:

[0034] Step S101: collecting high-frequency partial discharge pulse signals from the secondary terminals of the current transformer of the transformer bushing, wherein the transformer bushing includes a high-voltage side bushing, a medium-voltage side bushing, a neutral point bushing, a low-voltage side head-end bushing, and a low-voltage side end bushing.

[0035] In this embodiment, the secondary side terminals of the current transformers at these bushings can be connected to an oscilloscope or other observation equipment via a protective resistor to collect the corresponding high-frequency partial discharge pulse signals. Figure 2 FIG. 1 is a wiring diagram of a high-frequency partial discharge pulse signal acquisition method according to an embodiment of the present application. Figure 2 The wiring diagram is drawn to avoid repeated intersections with capacitor branches and does not represent the actual location. Figure 2 In the figure, a, x, Am, A, and X represent the transformer bushing terminals at the low-voltage head end, low-voltage tail end, medium-voltage, high-voltage, and neutral point, respectively. L1 and L2 represent the low-voltage winding, L3 and L4 represent the common winding for the high and medium voltage windings (referred to as the common winding), and L5 and L6 represent the high-voltage series winding. C1, C2, C3, and C4 represent the capacitances between the low-voltage winding and the core, the common winding and the low-voltage winding, the high-voltage series winding and the common winding, and the housing and the high-voltage series winding, respectively.

[0036] Step S102: performing discrete wavelet decomposition on the high-frequency partial discharge pulse signal to obtain wavelet coefficients.

[0037] Because the collected high-frequency partial discharge pulse signals typically contain significant low-frequency background noise, this can mask the pulse signal's polarity characteristics and hinder polarity determination in subsequent steps. Therefore, this application requires removing the background noise from the high-frequency partial discharge pulse signals. This embodiment employs a wavelet threshold denoising algorithm to remove background noise.

[0038] Since the collected high-frequency partial discharge pulse signal is a time series, it can be recorded as x(t), t=1, 2, ..., N, and N is the signal length.

[0039] In this step, the original signal x(t) is first decomposed into discrete wavelet by the following formula (1) to obtain the wavelet coefficients:

[0040] (1)

[0041] In the above formula a j ( n ) is the approximate coefficient, d j ( n ) is the detail coefficient, h is a low-pass filter, g is a high-pass filter, j is the number of decomposition layers.

[0042] Step S103: Select a soft threshold function to perform threshold processing on the wavelet coefficients to perform denoising.

[0043] Specifically, this step can be expressed by the following formula (2):

[0044] (2)

[0045] In the above formula W j,k Indicates the j Tierk Wavelet coefficients w j,k The corresponding wavelet coefficients after denoising, sgn(.) is the sign function; λ is a fixed threshold value, the value is:

[0046] (3)

[0047] In the above formula, σ is the standard deviation of the noise signal, N is the signal length.

[0048] Step S104: reconstructing the signal using the denoised wavelet coefficients to obtain a high-frequency partial discharge pulse signal after removing the background noise.

[0049] The signal reconstruction formula is shown in the following formula (4):

[0050] (4)

[0051] In the above formula, y ( t ) is the reconstructed signal, J is the total number of decomposition layers. In this embodiment, the wavelet basis function is selected as db4 wavelet, and the total number of decomposition layers is set to ,in is the floor function.

[0052] Step S105: performing amplitude correction on the high-frequency partial discharge pulse signal after background noise removal based on the frequency response characteristics of the current transformer to obtain a corrected pulse signal.

[0053] In actual work, the models of current transformers in various bushings of transformers are different, resulting in differences in the transmission capabilities of high-frequency partial discharge pulse signals.

[0054] Preferably, in order to eliminate the influence of this factor, this embodiment corrects the pulse signal amplitude based on the characteristic that the frequency response of the bushing current transformer is unchanged, such as Figure 3 As shown, this step may further include the following sub-steps:

[0055] Step S1051: injecting a calibration pulse signal into the end of any selected bushing of the transformer, and calculating the frequency spectrum of the calibration pulse signal.

[0056] Assume that the injected calibration pulse signal is p ( t ), use the following formula (5) to calculate the spectrum of the calibration pulse p ( jω ):

[0057] (5)

[0058] In the above formula, j is the imaginary unit, ω is the normalized angular frequency.

[0059] Step S1052: Collect the induction signal from the secondary port of the selected bushing and calculate the spectrum of the induction signal. Specifically, the spectrum of the induction signal is calculated according to the following formula (6):

[0060] (6)

[0061] In the above formula, R ( jω ) is the spectrum of the induced signal, r ( t ) is the induction signal at the secondary port of the selected bushing.

[0062] Step S1053: Calculate the frequency response of the selected casing using the spectrum of the calibration pulse signal and the spectrum of the sensing signal. Specifically, the frequency response of the selected casing is calculated according to the following formula (7):

[0063] (7)

[0064] In the above formula, H ( jω ) is the frequency response of the selected bushing.

[0065] Step S1054: Calculate the spectrum of the high-frequency partial discharge pulse signal of the selected bushing. The high-frequency partial discharge pulse signal here refers to the pulse signal after removing the background noise, so the calculated spectrum is also the spectrum after removing the noise. Specifically, it is calculated according to the following formula (8):

[0066] (8)

[0067] In the above formula, Y ( jω ) is the spectrum of the high-frequency partial discharge pulse signal after removing the background noise, y ( t ) is the corresponding high-frequency partial discharge pulse time domain signal, j is the imaginary unit, ω is the normalized angular frequency, N is the signal length.

[0068] Step S1055: Calculate the spectrum of the original pulse transmitted to the selected bushing using the spectrum of the high-frequency partial discharge pulse signal and the frequency response. Specifically, the spectrum of the original pulse of the selected bushing is obtained according to the following formula (9):

[0069] (9)

[0070] In the above formula, Z ( jω ) is the spectrum of the original pulse of the selected casing.

[0071] Step S1056: Obtain a time domain signal based on the spectrum of the original pulse by inverse discrete Fourier transform. Specifically, the time domain signal is obtained according to the following formula (10):

[0072] (10)

[0073] In the above formula, z ( t ) is the time domain signal.

[0074] Step S1057: Take the modulus of the time domain signal and find the maximum value to obtain the corrected amplitude, which is shown in the following formula (11):

[0075] (11)

[0076] In the above formula, N is the signal length, M is the correction amplitude.

[0077] Step S106: Based on the polarity distribution rule of the modified pulse signal, determine whether the transformer partial discharge is external interference or internal partial discharge. If it is external interference, proceed to step S107; if it is internal partial discharge, proceed to step S108.

[0078] When the transformer is subject to external interference or internal partial discharge occurs, the high-frequency partial discharge pulse signals induced in different bushing current transformers will exhibit different polarity characteristics.

[0079] When the transformer is subject to external interference, the interference signal penetrates from the top of a bushing, reaches the other end of the winding along the winding direction, and reaches other sensing locations through the capacitance between the windings, the capacitance between the winding and the box shell, and the capacitance between the winding and the iron core. During this period, the current direction does not change, so the pulse signal polarity flowing through the current transformer of each bushing is the same. Taking the high-voltage series winding and the common winding as an example, the current polarity can be seen in Figure 4 shown.

[0080] When the transformer discharges internally, the local discharge point can be regarded as a pulse source, sending high-frequency current pulse signals with opposite polarities to both sides, causing the pulse signals between the bushing current transformers to have opposite polarities. Taking the high-voltage series winding and the common winding as an example, the current polarity can be seen in Figure 5 As shown, the dotted line and the solid line represent high-frequency partial discharge pulse signals with opposite propagation directions.

[0081] Therefore, this step may further include: determining whether the polarities of the correction pulse signals corresponding to the bushings are the same; if they are the same, determining that the partial discharge of the transformer is external interference; if they are different, determining that the partial discharge of the transformer is internal partial discharge of the transformer.

[0082] Step S107: comparing the amplitudes of the corrected acquisition signals corresponding to the bushings, and the position corresponding to the bushing current transformer with the largest amplitude is the interference source injection position.

[0083] The amplitude of the bushing current transformer injected with external interference signal is the highest, which is obviously larger than that of other bushing current transformers. M A 、MA m 、M a , taking the high-voltage side bushing current transformer as an example, if the following conditions are met at the same time:

[0084] M A > K M MA m and M A > K M M a ;

[0085] It is determined that the interference signal invades from the high voltage side, in the above formula K M is the amplitude coefficient, usually in the range of 1.1~1.2.

[0086] Step S108: Based on the attenuation characteristics of the high-frequency pulse signal propagating in the winding and in combination with the pre-injected calibration square wave signal, the distance ratio between the partial discharge position and the winding head end is calculated to determine the discharge position.

[0087] When partial discharge occurs inside the transformer, the high-frequency pulse signal generated by the discharge source will propagate along both sides of the winding to the bushing current transformer. Since the electric and magnetic field strengths of the high-frequency pulse decay exponentially with increasing propagation distance, the amplitudes of the pulse signals received by the bushing current transformers at both ends of the winding will be different. Figure 2 Take the corresponding low voltage winding as an example, Figure 6 As shown, the total length of the winding is l , the distance between the discharge point and the winding head is d .

[0088] like Figure 7As shown, this step may further include the following sub-steps:

[0089] Step S1081: before the partial discharge detection test begins, a calibration square wave signal with the same charge amount is injected into the beginning and end of the winding to be tested, respectively, to obtain the electric field strength at the beginning and end of the winding to be tested.

[0090] In this embodiment, the winding to be tested is described as a low-voltage winding. That is, in this step, a calibration square wave signal with the same charge amount is injected into the beginning and end of the low-voltage winding respectively. The attenuation constant of the electromagnetic wave in the low-voltage winding is recorded as , at this time:

[0091] (12)

[0092] In the above formula, E a 、 E x are the electric field strengths at the beginning and end of the low-voltage winding respectively.

[0093] Step S1082: obtaining the electromagnetic energy of the high-frequency partial discharge pulse signal collected at the head end and the end bushing of the winding to be measured based on the electric field strength.

[0094] The electromagnetic energy of the high-frequency partial discharge pulse signal is proportional to the square of the electric field strength, that is:

[0095] (13)

[0096] (14)

[0097] In the above formula, C is a constant; 、 is the electromagnetic energy of the high-frequency partial discharge pulse signal received by the low-voltage head-end and end-end bushing current transformers, defined as:

[0098] (15)

[0099] (16)

[0100] in z a ( i ), z x ( i ), i= 1, 2, ..., N It is the time series of the pulse signal collected by the low-voltage head-end and end-end bushing current transformer after amplitude correction.

[0101] From this we can get:

[0102] (17)

[0103] In the above formula is the attenuation constant of electromagnetic waves in the low-voltage winding.

[0104] Step S1083: obtaining the signal energy at the beginning and the end of the winding to be measured based on the length of the winding to be measured, the electromagnetic energy and the electric field strength amplitude of the high-frequency pulse at the partial discharge location.

[0105] If the distance from the low voltage winding head is d Discharge occurs at the test point, and the signal energy at the beginning and end of the low voltage winding are respectively 、 , then:

[0106] (18)

[0107] (19)

[0108] In the above formula 、 The definition of 、 same; c is a constant; E m is the electric field intensity amplitude of the high-frequency pulse at the local discharge location.

[0109] Step S1084: obtaining a distance ratio between the partial discharge position and the winding head end based on the electromagnetic energy and the signal energy, and then determining the discharge position.

[0110] After simplifying and combining the above equations (18) and (19), we have:

[0111] (20)

[0112] (twenty one)

[0113] In the above formula, x is the distance between the partial discharge location and the winding head.

[0114] From this, we can conclude that the ratio of the partial discharge position to the winding head end is:

[0115] (twenty two)

[0116] The common winding and the high voltage series winding also have the same rules as the low voltage winding. For example, the present invention can define the first end of the common winding as the medium voltage side bushing lead terminal A. mThe end is the neutral point bushing lead-out terminal X; the first end of the high-voltage series winding is defined as A, and the end is defined as A m .

[0117] As can be seen from the above, the transformer partial discharge positioning method based on bushing CT acquisition proposed by the present invention reduces the interference factor of background noise, eliminates the influence of the bushing current transformer on the reception of high-frequency partial discharge pulse signals, and simplifies the method for determining the location of transformer partial discharge. Specifically, through polarity discrimination, it helps to quickly identify external interference and internal partial discharge signals, avoid malfunction of protection devices, and provide a basis for fault analysis and maintenance work. For external interference, by comparing the signal amplitudes of each bushing current transformer, the injection position of the interference source can be directly determined. For internal discharge, the attenuation characteristics of the high-frequency pulse signal in the winding are utilized, combined with the calibration signal, and the distance ratio from the discharge point to the winding head end is calculated to achieve precise positioning.

[0118] like Figure 8 The figure shows a schematic diagram of the structure of a transformer partial discharge positioning device based on bushing CT acquisition provided by an embodiment of the present application. The device includes: a signal acquisition unit 810, a wavelet decomposition unit 820, a denoising unit 830, a signal reconstruction unit 840, an amplitude correction unit 850, a discharge type determination unit 860, a first positioning unit 870, and a second positioning unit 880. Among them:

[0119] The signal acquisition unit 810 is used to collect high-frequency partial discharge pulse signals from the secondary side terminals of the current transformer of the transformer bushing, wherein the transformer bushing includes a high-voltage side bushing, a medium-voltage side bushing, a neutral point bushing, a low-voltage side head end bushing and a low-voltage side end bushing.

[0120] The wavelet decomposition unit 820 is configured to perform discrete wavelet decomposition on the high-frequency partial discharge pulse signal to obtain wavelet coefficients.

[0121] The denoising unit 830 is configured to select a soft threshold function to perform threshold processing on the wavelet coefficients to remove background noise.

[0122] The signal reconstruction unit 840 is configured to reconstruct the signal using the wavelet coefficients after background noise removal, to obtain the high-frequency partial discharge pulse signal after background noise removal.

[0123] The amplitude correction unit 850 is configured to perform amplitude correction on the high-frequency partial discharge pulse signal after background noise removal based on the frequency response characteristics of each bushing current transformer to obtain a corrected pulse signal.

[0124] The discharge type determination unit 860 is configured to determine whether the transformer partial discharge is caused by external interference or internal partial discharge based on the polarity distribution rule of the modified pulse signal.

[0125] The first positioning unit 870 is configured to compare the amplitudes of the corrected acquisition signals corresponding to the bushings when the discharge type determination unit determines that the signal is external interference, and the position corresponding to the bushing current transformer with the largest amplitude is the interference source injection position.

[0126] The second positioning unit 880 is used to determine the discharge position when the discharge type judgment unit determines that there is partial discharge inside the transformer, based on the attenuation characteristics of the high-frequency pulse signal propagating in the winding, combined with the pre-injected calibration square wave signal, by calculating the distance ratio from the partial discharge position to the winding head end.

[0127] Preferably, Figure 9 As shown, the amplitude correction unit 850 may further include:

[0128] The first spectrum calculation module 851 injects a calibration pulse signal into the end of any selected bushing of the transformer and calculates the spectrum of the calibration pulse signal.

[0129] The second spectrum calculation module 852 is configured to collect the induction signal from the secondary port of the selected bushing and calculate the spectrum of the induction signal.

[0130] The frequency response calculation module 853 is configured to calculate the frequency response of the selected casing using the frequency spectrum of the calibration pulse signal and the frequency spectrum of the sensing signal.

[0131] The third spectrum calculation module 854 is configured to calculate the spectrum of the high-frequency partial discharge pulse signal of the selected bushing.

[0132] The fourth spectrum calculation module 855 is configured to calculate the spectrum of the original pulse transmitted to the selected bushing using the spectrum of the high-frequency partial discharge pulse signal and the frequency response.

[0133] The inverse transform module 856 is configured to obtain a time domain signal by performing an inverse discrete Fourier transform based on the spectrum of the original pulse.

[0134] The amplitude correction module 857 is used to take the modulus of the time domain signal and find the maximum value to obtain the corrected amplitude.

[0135] Preferably, the above-mentioned discharge type judgment unit 860 is specifically used to: judge whether the polarity of the correction pulse signal corresponding to each bushing is the same; if so, it is judged that the partial discharge of the transformer belongs to external interference; if not, it is judged that the partial discharge of the transformer belongs to internal partial discharge of the transformer.

[0136] Preferably, Figure 10 As shown, the second positioning unit 880 may further include:

[0137] The electric field strength acquisition module 881 is used to inject calibration square wave signals with the same charge amount into the beginning and end of the winding to be tested before the partial discharge detection test begins, so as to obtain the electric field strength at the beginning and end of the winding to be tested.

[0138] The electromagnetic energy acquisition module 882 is used to obtain the electromagnetic energy of the high-frequency partial discharge pulse signal collected at the head end and the end bushing of the winding to be tested based on the electric field strength.

[0139] The signal energy acquisition module 883 is used to obtain the signal energy at the beginning and end of the winding to be measured based on the length of the winding to be measured, the electromagnetic energy and the electric field strength amplitude of the high-frequency pulse at the partial discharge.

[0140] The discharge position determination module 884 is configured to obtain a distance ratio between the local discharge position and the winding head end based on the electromagnetic energy and the signal energy, and then determine the discharge position.

[0141] As can be seen from the above, the transformer partial discharge positioning device based on bushing CT acquisition proposed by the present invention reduces the interference factor of background noise, eliminates the influence of the bushing current transformer on the reception of high-frequency partial discharge pulse signals, and simplifies the method of determining the transformer partial discharge position. Specifically, through polarity discrimination, it helps to quickly identify external interference and internal partial discharge signals, avoid malfunction of protection devices, and provide a basis for fault analysis and maintenance work. For external interference, by comparing the signal amplitudes of each bushing current transformer, the injection position of the interference source can be directly determined. For internal discharge, the attenuation characteristics of the high-frequency pulse signal in the winding are utilized, combined with the calibration signal, and the distance ratio from the discharge point to the winding head end is calculated to achieve precise positioning.

[0142] Figure 11 is a schematic diagram of an electronic device provided by an embodiment of the present invention. Figure 11 The electronic device shown is a general-purpose data processing device comprising a general-purpose computer hardware structure, including at least a processor 801 and a memory 802. Processor 801 and memory 802 are connected via a bus 803. Memory 802 is adapted to store one or more instructions or programs executable by processor 801. These one or more instructions or programs are executed by processor 801 to implement the steps of the aforementioned method for locating transformer partial discharge based on bushing CT acquisition.

[0143] The above-mentioned processor 801 can be an independent microprocessor or a collection of one or more microprocessors. Thus, the processor 801 executes the commands stored in the memory 802, thereby executing the method flow of the embodiment of the present invention as described above to realize the processing of data and the control of other devices. The bus 803 connects the above-mentioned multiple components together, and at the same time connects the above-mentioned components to the display controller 804 and the display device and the input / output (IO) device 805. The input / output (IO) device 805 can be a mouse, keyboard, modem, network interface, touch input device, somatosensory input device, printer and other devices known in the art. Typically, the input / output (IO) device 805 is connected to the system through the input / output (IO) controller 806.

[0144] The memory 802 may store software components such as an operating system, a communication module, an interaction module, and an application program. Each of the modules and applications described above corresponds to a set of executable program instructions that implement one or more functions and methods described in the embodiments of the invention.

[0145] An embodiment of the present invention further provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the transformer partial discharge location method based on bushing CT acquisition are implemented.

[0146] An embodiment of the present invention further provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the steps of the transformer partial discharge location method based on bushing CT acquisition.

[0147] The transformer partial discharge positioning method and device based on bushing CT acquisition proposed in the present invention reduces the interference factor of background noise, eliminates the influence of the bushing current transformer on the reception of high-frequency partial discharge pulse signals, and simplifies the method for determining the location of transformer partial discharge. Specifically, through polarity discrimination, it helps to quickly identify external interference and internal partial discharge signals, avoid malfunction of protection devices, and provide a basis for fault analysis and maintenance work. For external interference, the injection location of the interference source can be directly determined by comparing the signal amplitudes of each bushing current transformer. For internal discharge, the attenuation characteristics of the high-frequency pulse signal in the winding are utilized, combined with the calibration signal, to calculate the distance ratio from the discharge point to the winding head end, thereby achieving precise positioning.

[0148] Preferred embodiments of the present invention have been described above with reference to the accompanying drawings. Many features and advantages of these embodiments are apparent from this detailed description, and thus the appended claims are intended to cover all such features and advantages of these embodiments that fall within their true spirit and scope. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, the embodiments of the present invention are not intended to be limited to the precise construction and operation illustrated and described, but are intended to cover all suitable modifications and equivalents that fall within the scope thereof.

[0149] It will be understood by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take 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.) containing computer-usable program code.

[0150] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, 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 processes in the flowcharts and / or block diagrams. 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.

[0151] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0152] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0153] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A transformer partial discharge location method based on bushing CT acquisition, characterized in that: The method comprises: Collecting high-frequency partial discharge pulse signals from the secondary terminals of the current transformer of the transformer bushing, wherein the transformer bushing includes a high-voltage side bushing, a medium-voltage side bushing, a neutral point bushing, a low-voltage side head-end bushing, and a low-voltage side end bushing; performing discrete wavelet decomposition on the high-frequency partial discharge pulse signal to obtain wavelet coefficients; Selecting a soft threshold function to perform threshold processing on the wavelet coefficients to remove background noise; Reconstructing the signal using the wavelet coefficients after removing the background noise to obtain the high-frequency partial discharge pulse signal after removing the background noise; performing amplitude correction on the high-frequency partial discharge pulse signal after background noise removal based on the frequency response characteristics of the current transformer to obtain a corrected pulse signal; Determining whether the transformer partial discharge is external interference or internal partial discharge based on the polarity distribution rule of the modified pulse signal; If it is determined to be external interference, the amplitudes of the corrected acquisition signals corresponding to each bushing are compared, and the position corresponding to the bushing current transformer with the largest amplitude is the interference source injection position; If it is determined to be partial discharge inside the transformer, the discharge location is determined by calculating the ratio of the distance from the partial discharge location to the winding head end based on the attenuation characteristics of the high-frequency pulse signal propagating in the winding and the pre-injected calibration square wave signal; The amplitude correction of the high-frequency partial discharge pulse signal after background noise removal based on the frequency response characteristics of each bushing current transformer includes: injecting a calibration pulse signal into the end of any selected bushing of the transformer, and calculating the spectrum of the calibration pulse signal; Collecting the induction signal from the secondary port of the selected bushing and calculating the frequency spectrum of the induction signal; Calculating a frequency response of the selected casing using the frequency spectrum of the calibration pulse signal and the frequency spectrum of the sensing signal; Calculating the frequency spectrum of the high-frequency partial discharge pulse signal corresponding to the selected bushing; Calculating the spectrum of the original pulse transmitted to the selected bushing using the spectrum of the high-frequency partial discharge pulse signal and the frequency response; Obtaining a time domain signal through inverse discrete Fourier transform based on the spectrum of the original pulse; The time domain signal is modulo-ed, and the maximum value is found to obtain a corrected amplitude.

2. The transformer partial discharge location method based on bushing CT acquisition according to claim 1, characterized in that: The determining whether the transformer partial discharge is external interference or internal partial discharge based on the polarity distribution rule of the modified pulse signal includes: Determine whether the polarities of the correction pulse signals corresponding to the bushings are the same. If they are the same, it is determined that the partial discharge of the transformer is external interference. If they are different, it is determined that the partial discharge of the transformer is internal partial discharge of the transformer.

3. The transformer partial discharge location method based on bushing CT acquisition according to claim 1, characterized in that: The method of determining the discharge position by calculating the ratio of the distance from the partial discharge position to the winding head end based on the attenuation characteristics of the high-frequency pulse signal propagating in the winding in combination with the pre-injected calibration square wave signal includes: Before the partial discharge detection test begins, a calibration square wave signal with the same charge amount is injected into the beginning and end of the winding to be tested, respectively, to obtain the electric field strength at the beginning and end of the winding to be tested; Obtaining electromagnetic energy of the high-frequency partial discharge pulse signal collected at the head end and the end bushing of the winding to be measured based on the electric field strength; Obtaining signal energy at the beginning and end of the winding to be measured based on the length of the winding to be measured, the electromagnetic energy, and the electric field strength amplitude of the high-frequency pulse at the partial discharge; The distance ratio between the partial discharge position and the winding head end is obtained based on the electromagnetic energy and the signal energy, and the discharge position is then determined.

4. A transformer partial discharge positioning device based on bushing CT acquisition, characterized in that: The device comprises: A signal acquisition unit, configured to acquire high-frequency partial discharge pulse signals from the secondary terminals of the current transformer of the transformer bushing, wherein the transformer bushing includes a high-voltage side bushing, a medium-voltage side bushing, a neutral point bushing, a low-voltage side head-end bushing, and a low-voltage side end bushing; A wavelet decomposition unit, configured to perform discrete wavelet decomposition on the high-frequency partial discharge pulse signal to obtain wavelet coefficients; a denoising unit, configured to select a soft threshold function to perform threshold processing on the wavelet coefficients to remove background noise; A signal reconstruction unit, configured to reconstruct a signal using the wavelet coefficients after background noise removal to obtain the high-frequency partial discharge pulse signal after background noise removal; an amplitude correction unit, configured to perform amplitude correction on the high-frequency partial discharge pulse signal after background noise removal based on the frequency response characteristics of each bushing current transformer, to obtain a corrected pulse signal; a discharge type determination unit, configured to determine whether the transformer partial discharge is caused by external interference or internal partial discharge based on the polarity distribution rule of the modified pulse signal; a first positioning unit, configured to, when the discharge type determination unit determines that the signal is external interference, compare the amplitudes of the corrected acquisition signals corresponding to the bushings, and the position corresponding to the bushing current transformer with the largest amplitude is the interference source injection position; a second positioning unit, configured to, when the discharge type determination unit determines that partial discharge is occurring inside the transformer, determine the discharge location by calculating the ratio of the distance between the partial discharge location and the winding head end based on the attenuation characteristics of the high-frequency pulse signal propagating in the winding and a pre-injected calibration square wave signal; The amplitude correction unit includes: A first spectrum calculation module injects a calibration pulse signal into the end of any selected bushing of the transformer and calculates the spectrum of the calibration pulse signal; a second spectrum calculation module, configured to collect an induction signal from a selected casing secondary port and calculate a spectrum of the induction signal; a frequency response calculation module, configured to calculate a frequency response of the selected casing using a frequency spectrum of the calibration pulse signal and a frequency spectrum of the induction signal; a third spectrum calculation module, configured to calculate the spectrum of the high-frequency partial discharge pulse signal of the selected bushing; a fourth spectrum calculation module, configured to calculate the spectrum of the original pulse transmitted to the selected bushing by using the spectrum of the high-frequency partial discharge pulse signal and the frequency response; An inverse transform module, configured to obtain a time domain signal by performing an inverse discrete Fourier transform based on the spectrum of the original pulse; The amplitude correction module is used to take the modulus of the time domain signal and find the maximum value to obtain the corrected amplitude.

5. The transformer partial discharge location device based on bushing CT acquisition according to claim 4, characterized in that: The discharge type judgment unit is specifically used to judge whether the polarities of the correction pulse signals corresponding to the bushings are the same. If they are the same, it is determined that the partial discharge of the transformer is external interference; if they are not the same, it is determined that the partial discharge of the transformer is internal partial discharge of the transformer.

6. The transformer partial discharge location device based on bushing CT acquisition according to claim 4, characterized in that: The second positioning unit includes: An electric field strength acquisition module is used to inject a calibration square wave signal of the same charge amount into the beginning and end of the winding to be tested before the partial discharge detection test begins, so as to obtain the electric field strength at the beginning and end of the winding to be tested; An electromagnetic energy acquisition module, configured to obtain the electromagnetic energy of the high-frequency partial discharge pulse signal collected at the head end and the end bushing of the winding to be tested based on the electric field strength; A signal energy acquisition module is used to obtain the signal energy of the beginning and the end of the winding to be measured based on the length of the winding to be measured, the electromagnetic energy and the electric field strength amplitude of the high-frequency pulse at the partial discharge; The discharge position determination module is used to obtain the distance ratio between the local discharge position and the winding head end based on the electromagnetic energy and the signal energy, and then determine the discharge position.

7. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 3 are implemented.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 3 are implemented.

9. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instructions are executed by a processor, the steps of the method according to any one of claims 1 to 3 are implemented.

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