A three-dimensional visualization method and system for locating partial abnormal discharges in substation equipment

Abstract

This invention discloses a three-dimensional visualization method and system for locating partial abnormal discharges in substation equipment, relating to the field of discharge location technology. It acquires the time-domain waveform of partial discharge from an ultra-high frequency sensor within a mixed bay consisting of gas-insulated switchgear and cable terminals. The waveform is processed using a Hanning window and discrete Fourier transform to obtain the power spectrum. The operating band is defined, and the mean power spectrum and cross-channel spectral values ​​are calculated to determine the free spectrum interval, generating a comb center set. The parasitic leakage index is then calculated, and the broadband energy is divided by this index to obtain the equalized broadband energy. Based on this, combined with sensor installation parameters, the spatial coordinates of the partial discharge are calculated. Finally, the location result is visualized in three dimensions by associating it with the equipment's three-dimensional model. This solution eliminates the interference of parasitic resonance on location, restores the comparability of amplitude and distance attenuation, improves location accuracy, and the three-dimensional visualization facilitates rapid identification of discharge locations by maintenance personnel, ensuring the safe operation of substation equipment.

Description

Technical Field

[0001] This invention relates to the field of discharge location technology, specifically to a three-dimensional visualization method and system for locating local abnormal discharges in substation equipment. Background Technology

[0002] In a hybrid compartment consisting of gas-insulated switchgear and cable terminals, the epoxy sheath and stress cone of the cable terminal form a unique axisymmetric thick-walled dielectric body. The ultra-high frequency (UHF) pulse signals generated by partial discharge require multi-sensor acquisition for localization. Existing technologies often rely on the attenuation of UHF pulse amplitude or energy over propagation distance, comparing the amplitude ratios of signals acquired by different sensors to inversely determine the location of the partial discharge source. However, when the UHF pulses generated by partial discharge propagate within the axisymmetric thick-walled dielectric body formed by the epoxy sheath and stress cone of the cable terminal, unexpected parasitic resonance phenomena can occur due to interface reflection between the dielectric and metal components, and the matching relationship between structural geometry and electromagnetic wavelength. This parasitic resonance causes the UHF pulse energy to exhibit a series of equally spaced parasitic comb-like spectral lines in the frequency domain, and the degree of influence of parasitic resonance varies among different UHF sensor channels. This parasitic resonance causes the UHF pulse energy generated by internal defects to be selectively stored within a specific narrow band and then leaked directionally through openings such as flange openings, resin holes, or slits.

[0003] Parasitic resonance echoes cause unequal amplification of the equivalent channel gain of each sensor within the narrow band of parasitic resonance, and the amplification amplitude is closely related to the directionality of the opening. This undermines the localization assumption that the signal amplitude or energy attenuation is only related to the propagation distance and path geometry. Existing partial discharge localization methods suffer from systematic localization errors due to the disruption of amplitude-frequency consistency caused by parasitic resonance and directional leakage, even without considering differences in signal arrival time. This makes it impossible to accurately determine the actual location of the partial discharge source in the substation equipment space, severely impacting the accuracy of equipment insulation condition assessment and fault diagnosis. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a three-dimensional visualization method and system for locating partial abnormal discharges in substation equipment, solving the problem that it cannot accurately determine the actual location of the partial discharge source in the substation equipment space.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] The time-domain waveform of the same partial discharge event is acquired by an ultra-high frequency sensor. The power spectrum is obtained by performing a discrete Fourier transform on the time-domain waveform. The power spectrum includes the power values ​​of frequency points marked at different frequency positions in the sensor channel. The power spectrum mean is obtained. The frequency interval to be tested is preset. The cross-channel spectrum value is calculated based on the product of the difference between the power values ​​of the two frequency points of the frequency interval to be tested and the power spectrum mean. The frequency interval to be tested with the largest cross-channel spectrum value is marked as the free spectrum interval by traversal test. The comb center frequency is generated sequentially with the free spectrum interval as the step size. Each comb center frequency is mapped to the frequency point with the closest interval.

[0007] The comb spectrum energy is obtained by summing the power values ​​of all frequency points corresponding to the center frequencies of the comb lines. The center frequency obtained by adding half of the free spectrum interval to the center frequency of the comb lines is marked as the center frequency of the anti-comb line. The anti-comb spectrum energy is calculated based on the center frequency of the anti-comb line. The value obtained by dividing the comb spectrum energy by the anti-comb spectrum energy is marked as the parasitic leakage index. The value obtained by summing the power values ​​of all frequency points in the power spectrum is marked as the broadband energy. The value obtained by dividing the broadband energy by the parasitic leakage index is marked as the equalized broadband energy. Local abnormal discharges are located based on the equalized broadband energy.

[0008] Furthermore, the time-domain waveforms corresponding to each sensor channel are windowed using a Hanning window and then subjected to a Discrete Fourier Transform. The power spectrum of the sensor channel is obtained by taking the modulus of the Discrete Fourier Transform result and squaring it.

[0009] Define the effective analysis frequency range determined by the ultra-high frequency radiation characteristics of substation equipment and the bandwidth of the sampling system, and mark the effective analysis frequency range as the working band. Within the working band, sum the power values ​​of all frequency points on the power spectrum of each sensor channel, and then divide the sum by the number of frequency points in the working band to obtain the average value of the power spectrum of each sensor channel within the working band, and mark this average value as the power spectrum mean.

[0010] The number of frequency points is the ratio of the difference between the upper and lower frequency limits within the working band to the frequency resolution, where the frequency resolution is the frequency interval between adjacent frequency points in the discrete Fourier transform.

[0011] Furthermore, a preset frequency interval to be measured is defined as the frequency difference between 0 and the upper limit of the operating band.

[0012] For the same sensor channel, the number of frequency points n within the working band that are spaced at the frequency interval to be measured is calculated by multiplying the difference between the power value of the i-th frequency point and the power spectrum mean by the power value of the frequency point at the (i+)-th frequency interval to be measured by ...

[0013] The cross-channel spectral values ​​obtained after traversing and testing each frequency interval to be tested and inputting the above calculation process are used to mark the frequency interval to be tested with the largest cross-channel spectral value as the free spectrum interval. The free spectrum interval reflects the frequency difference between two adjacent spectral lines of the parasitic comb spectral line.

[0014] Furthermore, starting from the lower limit frequency of the working band to the upper limit frequency of the working band, the comb center frequency is generated sequentially with the free spectrum interval as the step size. The comb center frequency = the lower limit frequency of the working band + n × the free spectrum interval, where n is the order in which the comb center frequencies are generated.

[0015] Next, each comb center frequency is mapped to the frequency point with the closest frequency interval, and all mapped frequency points are combined into a comb center set, which includes all comb center frequencies aligned with the frequency points.

[0016] Furthermore, for the m-th sensor channel, the power values ​​of the frequency points corresponding to the frequencies of all comb center frequencies in the comb center set are summed in the power spectrum to obtain the comb spectrum energy of the m-th sensor channel. The comb spectrum energy is the total energy of the frequency points corresponding to the parasitic comb spectral lines.

[0017] Furthermore, for the m-th sensor channel, all comb center frequencies in the comb center set are traversed sequentially, and the anti-comb center frequency is calculated. The specific calculation method is as follows:

[0018] The center frequency of each comb center in the comb center set, after adding half of the free spectrum interval, is marked as the anti-comb center frequency. The anti-comb center frequency is the reference position of the energy of the parasitic comb spectrum.

[0019] For the center frequency of the anti-comb line, each anti-comb line center frequency is mapped to the frequency point with the closest frequency interval. The power values ​​of the corresponding frequency points of all anti-comb line center frequencies in the power spectrum are summed to obtain the anti-comb spectrum energy of the m-th sensor channel. The anti-comb spectrum energy is the total energy of the non-comb spectrum reference position.

[0020] Furthermore, the value obtained by dividing the comb energy of the m-th sensor channel by the anti-comb energy is denoted as the parasitic leakage index, which is a dimensionless parasitic leakage index of the m-th sensor channel.

[0021] For the m-th sensor channel, the summation of the power values ​​at all frequency points within the power spectrum within the working band is marked as the broadband energy of the m-th sensor channel, which is the total energy of the m-th channel within the working band.

[0022] For the m-th sensor channel, the value obtained by dividing the broadband energy of the m-th sensor channel by the parasitic leakage index of the m-th sensor channel is marked as the equalized broadband energy. The equalized broadband energy is the corrected broadband energy of the m-th sensor channel.

[0023] Furthermore, a three-dimensional spatial model is constructed based on the coordinate system within the substation. The three-dimensional coordinates of each UHF sensor in the coordinate system within the substation are obtained. The three-dimensional coordinates of the sensor are calibrated during equipment installation. The geometric allowable domain of the equipment is obtained. The geometric allowable domain of the equipment is the three-dimensional spatial range in which the local discharge power source may exist. The three-dimensional coordinate points within the three-dimensional allowable domain of the equipment are traversed, and the three-dimensional coordinate points within the three-dimensional allowable domain of the equipment are marked as candidate source points. The three-dimensional coordinates of the sensor and the three-dimensional allowable domain of the equipment are imported into the three-dimensional spatial model.

[0024] Calculate the straight-line distance from each candidate source point to each UHF sensor in three-dimensional space, and mark this straight-line distance as the equivalent distance. The equivalent distance is the spatial distance from the candidate source point to the m-th sensor, which reflects the propagation path length of the signal from the local discharge source to the sensor.

[0025] For any two sensor channels, the ratio of the equalized broadband energy generation logarithmic amplitudes based on the sensor channels is as follows:

[0026] The logarithmic amplitude ratio is obtained by taking the natural logarithm of the ratio of the equalized broadband energy of the i-th sensor channel to the equalized broadband energy of the j-th sensor channel. The logarithmic amplitude ratio reflects the logarithmic difference in energy attenuation between the two sensor channels after equalization.

[0027] For any two sensor channels, a logarithmic distance ratio is generated based on the equivalent distance from the candidate source point to the sensor channel, as follows:

[0028] The logarithmic distance ratio is obtained by taking the natural logarithm of the ratio of the equivalent distance from the nth candidate source point to the i-th sensor channel to the equivalent distance from the nth candidate source point to the j-th sensor channel. The logarithmic distance ratio reflects the logarithmic difference between the distances from the candidate source point to the two sensors.

[0029] Furthermore, the sum of the results of multiplying the logarithmic amplitude ratio and logarithmic distance ratio of each pair of sensor channels corresponding to the same candidate source point, and then dividing by the sum of the squares of all the logarithmic distance ratios corresponding to the same candidate source point, is marked as the geometric attenuation ratio coefficient. The geometric attenuation ratio coefficient reflects the proportional relationship between amplitude attenuation and distance attenuation.

[0030] For each pair of sensors corresponding to the same candidate source point, the square of the difference between the logarithmic amplitude ratio of each pair of sensors and the product of the geometric attenuation ratio coefficient and the logarithmic distance ratio is taken, and the squares of the results of each pair of sensors corresponding to the same candidate source point are summed to obtain the total residual.

[0031] Within the geometrically permissible domain of the device, all candidate source points are traversed to obtain the candidate source point that minimizes the total residual value, and this candidate source point is marked as the local abnormal discharge location result.

[0032] The results of locating local abnormal discharges are output to a 3D visualization interface.

[0033] Furthermore, a three-dimensional visualization substation equipment partial abnormal discharge location system is proposed to implement the partial abnormal discharge location method described above, including:

[0034] The comb center generation module acquires the time-domain waveform of the same partial discharge event collected by the UHF sensor. After processing the time-domain waveform through the Hanning window, it performs a discrete Fourier transform to obtain the power spectrum, defines the working band, calculates the mean power spectrum of each sensor channel and the cross-channel spectrum value, determines the free spectrum interval, generates the comb center frequency from the lower limit frequency of the working band with the free spectrum interval as the step size, and maps it to the frequency points to form a comb center set.

[0035] The parasitic index calculation module accumulates the power spectrum power value of the comb center set corresponding to the comb energy, calculates the center frequency of the anti-comb, maps it to the frequency point, accumulates its power value to obtain the anti-comb energy, divides the comb energy by the anti-comb energy to obtain the parasitic leakage index, which reflects the strength of the channel affected by the circumferential parasitic resonance echo.

[0036] The broadband energy equalization module accumulates the power spectrum power values ​​of all frequency points within the working band to obtain the broadband energy. The broadband energy is then divided by its parasitic leakage index to obtain the equalized broadband energy. This eliminates narrowband amplification interference caused by parasitic resonance, restores the comparability of amplitude and distance attenuation, and ensures that the equalized broadband energy is determined only by the distance from the partial discharge source to the sensor and the propagation path.

[0037] The discharge location calculation module, based on the equalized broadband energy of each sensor channel and combined with the sensor installation position parameters, calculates the three-dimensional spatial coordinates of the local discharge source according to the physical law of amplitude attenuation with distance, and determines the specific location of the local abnormal discharge.

[0038] The 3D visualization module associates the location results of localized discharge with the 3D spatial model, and uses visualization technology to display the spatial location of the discharge point in the equipment, realizing the 3D visualization of the localized abnormal discharge location results, which facilitates the operation and maintenance personnel to accurately identify the discharge location.

[0039] Compared with existing technologies, it has the following advantages:

[0040] This solution proposes a three-dimensional visualization method and system for locating local abnormal discharges in substation equipment. It acquires time-domain waveforms from ultra-high frequency sensors within a mixed interval consisting of gas-insulated switchgear and cable terminals. After processing with a Hanning window, it performs a discrete Fourier transform to obtain the power spectrum, defines the working band, calculates the mean of the power spectrum, and then determines the free spectrum interval that maximizes this value through cross-channel spectrum values. Subsequently, it generates comb center frequencies from the lower limit frequency of the working band with the free spectrum interval as the step size and forms a comb center set, accurately locking the parasitic resonance related frequency points.

[0041] This scheme achieves quantitative comparison of parasitic interference in each sensor channel through the parasitic leakage index. The comb spectrum energy is obtained by accumulating the power of the corresponding frequency points of the comb center set, and the anti-comb spectrum energy is obtained by calculating the center frequency of the anti-comb and accumulating the power of the corresponding frequency points. The ratio of the two is the parasitic leakage index. This index is dimensionless and can accurately reflect the strength of the influence of circumferential parasitic resonance echo on each channel. At the same time, it eliminates the interference of the overall energy level difference of different channels on the interference judgment, and solves the problems of existing technologies being unable to quantify the degree of channel interference and difficult to unify the analysis standard.

[0042] This solution completely solves the core problem of positioning distortion caused by parasitic resonance by broadband energy equalization. The broadband energy obtained by summing the power of all frequency points within the working band of the sensor channel is divided by its parasitic leakage index to obtain the equalized broadband energy. This process regards the abnormal amplification of narrowband energy by parasitic resonance as an equivalent multiplicative gain and removes it. This makes the equalized broadband energy determined only by the distance and propagation path from the local discharge source to the sensor, restoring the physical law of amplitude attenuation with distance. This avoids the distance judgment deviation caused by the destruction of amplitude-frequency consistency in existing technologies and greatly improves positioning accuracy.

[0043] This solution enhances the practicality of operation and maintenance by combining 3D visualization. Based on the equalized broadband energy and sensor installation parameters, the spatial coordinates of the discharge are calculated according to the amplitude attenuation law. The positioning results are then associated with the 3D model of the equipment to intuitively display the specific location of the discharge point within the mixed interval. This solves the problem that operation and maintenance personnel have difficulty in quickly locating the parts to be repaired, and significantly improves the efficiency of fault diagnosis and the operational safety of substation equipment. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the method flow of the present invention;

[0045] Figure 2 This is a schematic diagram of the system framework of the present invention; Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] First Embodiment

[0048] This application provides a three-dimensional visualization method for locating local abnormal discharges in substation equipment;

[0049] The method specifically includes the following steps:

[0050] The time-domain waveform of the same partial discharge event is acquired by an ultra-high frequency sensor. The power spectrum is obtained by performing a discrete Fourier transform on the time-domain waveform. The power spectrum includes the power values ​​of frequency points marked at different frequency positions in the sensor channel. The power spectrum mean is obtained. The frequency interval to be tested is preset. The cross-channel spectrum value is calculated based on the product of the difference between the power values ​​of the two frequency points of the frequency interval to be tested and the power spectrum mean. The frequency interval to be tested with the largest cross-channel spectrum value is marked as the free spectrum interval by traversal test. The comb center frequency is generated sequentially with the free spectrum interval as the step size. Each comb center frequency is mapped to the frequency point with the closest interval.

[0051] The comb spectrum energy is obtained by summing the power values ​​of all frequency points corresponding to the center frequencies of the comb lines. The center frequency obtained by adding half of the free spectrum interval to the center frequency of the comb lines is marked as the center frequency of the anti-comb line. The anti-comb spectrum energy is calculated based on the center frequency of the anti-comb line. The value obtained by dividing the comb spectrum energy by the anti-comb spectrum energy is marked as the parasitic leakage index. The value obtained by summing the power values ​​of all frequency points in the power spectrum is marked as the broadband energy. The value obtained by dividing the broadband energy by the parasitic leakage index is marked as the equalized broadband energy. Local abnormal discharges are located based on the equalized broadband energy.

[0052] Second Embodiment

[0053] Please see Figure 1 As a second embodiment of this application, this embodiment is implemented based on the first embodiment, and the method provided in this embodiment includes the following steps:

[0054] Step 1: Obtain the time-domain waveform of the same partial discharge event collected in the mixed interval formed by the gas-insulated switchgear and the cable terminal. For example, install four or more UHF sensors at the cable terminal flange or the detection port of the gas-insulated switchgear housing to collect the time-domain signal of the same partial discharge event, and convert the time-domain signal into a time-domain waveform.

[0055] The time-domain waveforms corresponding to each sensor channel are windowed using a Hanning window and then subjected to a Discrete Fourier Transform (DFT). The power spectrum of the sensor channel is obtained by taking the modulus of the DFT result and squaring it. The power spectrum reflects the power values ​​at different frequency points of the sensor channel. The frequency point is a discrete point in the frequency domain used to mark different frequency positions, obtained by multiplying the frequency resolution of the DFT by the frequency point index. The frequency resolution is equal to the ratio of the sensor's sampling rate to the truncation length set by the number of sample points used to analyze the time-domain waveform, which is the frequency interval between adjacent frequency points in the DFT.

[0056] Define the effective analysis frequency range determined by the ultra-high frequency radiation characteristics of substation equipment and the bandwidth of the sampling system, for example, the range is [300MHz, 1.5GHz], and mark the effective analysis frequency range as the working band. Within the working band, sum the power values ​​of all frequency points on the power spectrum of each sensor channel, and then divide the sum by the number of frequency points in the working band to obtain the average value of the power spectrum of each sensor channel within the working band. This average value is marked as the power spectrum mean. The power spectrum mean is used to eliminate the interference of the overall energy level difference of the channel on subsequent analysis. Specifically, the number of frequency points = the ratio of the difference between the upper and lower frequency limits in the working band to the frequency resolution.

[0057] For the same sensor channel, the number of frequency points n within the working band that are spaced at the frequency intervals to be measured is calculated by multiplying the difference between the power value of the i-th frequency point and the power spectral mean by the power value of the frequency point at the (i+)-th frequency interval to be measured by the power spectral mean. This yields a product of n-1 frequency point pairs. These n-1 frequency point pairs are then summed. The summation of these products across all sensor channels yields the cross-channel spectrum value. Specifically, assuming the same sensor channel... There are 10 frequency points in the working band, and 5 frequency points with an interval equal to the frequency to be measured. There are a total of 4 frequency point pairs. For example, the first frequency point and the second frequency point are one frequency point pair, the second and the third frequency point are one frequency point pair, and the fifth frequency point is only paired with the fourth frequency point. This will result in 4 products. The sum of these 4 products is the sum of the values ​​in a single sensor channel. The sum of the values ​​in all sensor channels is then added together to obtain the cross-channel spectrum value.

[0058] Specifically, the frequency interval to be measured is a series of frequency differences between 0 and the upper limit of the working band, which is used to find the interval that maximizes the cross-channel spectral value. The cross-channel spectral value measures the similarity of the power spectrum at the frequency interval to be measured. If there are equally spaced comb lines in the power spectrum, the cross-channel spectral value will reach its maximum value when the frequency interval to be measured is equal to the comb line interval.

[0059] The cross-channel spectrum value obtained after traversing and testing each frequency interval to be tested and inputting the above calculation process will mark the frequency interval to be tested with the largest cross-channel spectrum value as the free spectrum interval. The free spectrum interval reflects the frequency difference between two adjacent spectral lines of the parasitic comb line and is one of the core characteristics of parasitic resonance, providing an interval basis for the subsequent generation of the comb line center set.

[0060] Specifically, in the mixed compartment formed by gas-insulated switchgear and cable terminals, the epoxy sheath and stress cone of the cable terminal constitute an axisymmetric thick-walled dielectric. When ultra-high frequency pulses generated by local discharge propagate within this structure, unexpected electromagnetic resonance phenomena can occur due to factors such as the interface between the dielectric and metal components and the structural geometry. This type of resonance, which is not actively designed by the equipment but is incidentally generated by the structure, is called parasitic resonance. When parasitic resonance occurs, the energy of the ultra-high frequency pulse will oscillate repeatedly at a specific frequency and store energy. After converting the signal from the time domain to the frequency domain, the energy distribution will show a series of equally spaced frequency peaks. These peaks, arranged like the teeth of a comb, are called parasitic comb-like spectral lines. The free spectral interval refers to the frequency difference between two adjacent spectral lines in a parasitic comb. It is determined by the structure of the medium that produces the parasitic resonance, such as the thickness and geometry of the epoxy component, and reflects the resonance characteristics of the structure. If equally spaced comb peaks appear in the frequency domain, the presence of parasitic resonance can be determined by measuring the frequency difference between adjacent peaks, i.e., the free spectral interval. At the same time, when extracting the energy of parasitic comb spectral lines, it is necessary to first determine the center frequency position of these spectral lines. The free spectral interval provides the step size. Starting from a certain initial frequency, the center frequency of all parasitic comb spectral lines can be accurately determined by recursively calculating the free spectral interval, laying the foundation for subsequent operations such as energy extraction and leakage quantization.

[0061] Starting from the lower limit frequency of the working band to the upper limit frequency of the working band, the center frequencies of the comb lines are generated sequentially with the free spectrum interval as the step size. The center frequency of the comb line = the lower limit frequency of the working band + n × the free spectrum interval, where n = 0, 1, 2, etc. Then, each center frequency of the comb line is mapped to the frequency point with the closest interval. All the mapped frequency points are combined into a comb center set, which is the set of center frequencies of all parasitic comb spectral lines aligned with the frequency points.

[0062] Specifically, assuming the free spectrum interval between adjacent spectral lines of the parasitic comb spectrum is 50MHz, the cross-channel spectral value will show a significant peak when the free spectrum interval is 50MHz. Starting from the lower limit frequency of the working band, such as 300MHz, comb center frequencies of 300MHz, 350MHz, and 400MHz are generated, and the comb center frequencies are mapped to the frequency points closest in frequency interval to obtain the comb center set.

[0063] Step 2: For the m-th sensor channel, sum the power values ​​of the frequency points corresponding to the frequencies of all comb center frequencies in the comb center set in the power spectrum to obtain the comb spectrum energy of the m-th sensor channel. The comb spectrum energy is the total energy of the frequency points corresponding to the parasitic comb spectral lines, reflecting the comb spectral energy leaked by the sensor channel due to parasitic resonance.

[0064] For the m-th sensor channel, iterate through all the comb center frequencies in the comb center set and calculate the anti-comb center frequency. The anti-comb center frequency is calculated by adding half of the free spectrum interval to the center frequency of each comb center frequency in the comb center set. The anti-comb center frequency is the reference position of the energy of the parasitic comb spectrum.

[0065] For the center frequency of the anti-comb line, each anti-comb line center frequency is mapped to the frequency point with the closest interval. The power values ​​of the corresponding frequency points of all anti-comb line center frequencies in the power spectrum are summed to obtain the anti-comb spectrum energy of the m-th sensor channel. The anti-comb spectrum energy is the total energy of the non-comb spectrum reference position, which reflects the background energy level of the non-parasitic comb spectrum reference position of the channel.

[0066] The value obtained by dividing the comb spectrum energy of the m-th sensor channel by the anti-comb spectrum energy is tagged as the parasitic leakage index. The parasitic leakage index is a dimensionless parasitic leakage index of the m-th sensor channel, which reflects the strength of the influence of the circumferential parasitic resonance echo on the sensor channel. The larger the parasitic leakage index, the more energy the channel leaks due to parasitic resonance relative to the background energy, and the stronger the influence.

[0067] Specifically, by using the ratio of comb spectrum energy to anti-comb spectrum energy, the intensity of parasitic resonant leakage of each sensor channel relative to the background energy is quantified, eliminating the interference of the overall energy level difference between different channels on the judgment of the degree of parasitic leakage, and making the leakage degree of each channel dimensionless and comparable.

[0068] Step 3: For the m-th sensor channel, within the working band, the summation of the power values ​​at all frequency points in the power spectrum is marked as the broadband energy of the m-th sensor channel. The broadband energy is the total energy of the m-th channel within the working band. Due to the destruction of amplitude-frequency consistency caused by parasitic resonance, different channels have different amplification levels in the parasitic narrowband.

[0069] For the m-th sensor channel, the broadband energy of the m-th sensor channel is divided by the parasitic leakage index of the m-th sensor channel and the value obtained is marked as the equalized broadband energy. The equalized broadband energy is the broadband energy of the m-th sensor channel after correction. It eliminates the narrowband amplification caused by parasitic resonance and restores the comparability of amplitude and distance attenuation. That is, the equalized broadband energy of different channels is determined only by the distance from the partial discharge source to the sensor and the propagation path.

[0070] Specifically, assuming the broadband energy of the i-th sensor channel is 1000 and the parasitic leakage index of the i-th sensor channel is 2.32, then the equalized broadband energy of the i-th sensor channel is approximately 431. Assuming the broadband energy of the j-th sensor channel is 900 and the parasitic leakage index of the j-th sensor channel is 1.8, then the equalized broadband energy of the j-th sensor channel is 500. At this point, the difference in equalized broadband energy between the i-th and j-th sensor channels is determined only by the distance and path from the partial discharge source to the two sensors, and is no longer affected by parasitic resonance amplification. By using the equalized broadband energy, the abnormal amplification of narrowband energy by parasitic resonance is regarded as an equivalent multiplicative gain and removed, so that the broadband energy of each channel once again satisfies the law of amplitude attenuation with distance. This solves the core problem of positioning distortion caused by amplitude-frequency inconsistency and ensures the positioning accuracy of subsequent local abnormal discharges.

[0071] Step 4: Construct a three-dimensional spatial model based on the substation coordinate system, obtain the three-dimensional coordinates of each sensor in the substation coordinate system. The sensor three-dimensional coordinates are calibrated during equipment installation, and the range of values ​​is the actual installation space of the sensor. Obtain the geometric allowable domain of the equipment. The geometric allowable domain of the equipment is the three-dimensional spatial range in which local discharge sources may exist. It is determined by the structural dimensions and insulation range of equipment such as gas-insulated switchgear and cable terminals. Traverse the three-dimensional coordinate points in the three-dimensional allowable domain of the equipment and mark the three-dimensional coordinate points in the three-dimensional allowable domain of the equipment as candidate source points. Import the sensor three-dimensional coordinates and the three-dimensional allowable domain of the equipment into the three-dimensional spatial model to clarify the boundary of the three-dimensional space and the sensor distribution and the area where local discharge sources may exist.

[0072] Calculate the straight-line distance from each candidate source point to each sensor in three-dimensional space, and mark this straight-line distance as the equivalent distance. The equivalent distance is the spatial distance from the candidate source point to the m-th sensor, which reflects the propagation path length of the signal from the local discharge source to the sensor.

[0073] For any two sensor channels, the logarithmic amplitude ratio is generated based on the equalized broadband energy of the sensor channels. Specifically, the natural logarithm of the ratio of the equalized broadband energy of the i-th sensor channel to the equalized broadband energy of the j-th sensor channel is taken to obtain the logarithmic amplitude ratio. The logarithmic amplitude ratio reflects the logarithmic difference in energy attenuation between the two sensor channels after equalization. Since energy attenuation with distance is usually exponential, the logarithmic amplitude ratio obtained after taking the natural logarithm can be transformed into a linear relationship.

[0074] For any two sensor channels, a logarithmic distance ratio is generated based on the equivalent distance from the candidate source point to the sensor channel. Specifically, the natural logarithm of the ratio of the equivalent distance from the nth candidate source point to the ith sensor channel to the equivalent distance from the nth candidate source point to the jth sensor channel is taken to obtain the logarithmic distance ratio. The logarithmic distance ratio reflects the logarithmic difference in the distance from the candidate source point to the two sensors and forms a linear correspondence with the logarithmic magnitude ratio.

[0075] Specifically, converting the magnitude ratio and distance ratio into the logarithmic domain makes their linear relationship more significant, providing a linear model basis for subsequent least squares fitting, reducing fitting difficulty, and improving fitting efficiency.

[0076] The geometric attenuation ratio is calculated by multiplying the logarithmic amplitude ratio and logarithmic distance ratio of a pair of sensor channels corresponding to the same candidate source point, summing the results of multiplying the logarithmic amplitude ratio and logarithmic distance ratio of each pair of sensor channels corresponding to the same candidate source point, and then dividing the sum by the sum of the squares of all the logarithmic distance ratios corresponding to the same candidate source point. This result is denoted as the geometric attenuation ratio coefficient. The geometric attenuation ratio coefficient reflects the proportional relationship between amplitude attenuation and distance attenuation. Specifically, assuming a total of four UHF sensors are installed, there will be six pairs of sensor channels. That is, for the same candidate source point, there will be six corresponding logarithmic amplitude ratios and logarithmic distance ratios. The geometric attenuation ratio coefficient is the result of multiplying the logarithmic amplitude ratio and logarithmic distance ratio of each pair of sensors for the same candidate source point, summing the results, and then dividing the sum by the sum of the squares of the six logarithmic amplitude ratios.

[0077] For each pair of sensors corresponding to the same candidate source point, the square of the difference between the logarithmic amplitude ratio and the product of the geometric attenuation ratio and the logarithmic distance ratio is taken, and the squares of the differences are summed for each pair of sensors corresponding to the same candidate source point to obtain the total residual. The smaller the total residual, the more consistent the distance relationship between the candidate source point and the sensor is with the energy relationship of the actual local discharge source. Specifically, the global matching degree of the amplitude ratio and the distance ratio is quantified by least squares fitting. The obtained total residual can objectively measure the rationality of the candidate point and improve the reliability of local abnormal discharge location.

[0078] Within the geometrically permissible domain of the device, all candidate source points are traversed to obtain the candidate source point that minimizes the total residual value. This candidate source point is then marked as the local abnormal discharge location result. The local abnormal discharge location result is the candidate source point that minimizes the total residual, and its distance relationship is most consistent with the energy relationship of the actual partial discharge source. Specifically, through global traversal and residual minimization, the location of the partial discharge source that best matches the consistency of amplitude ratio and distance ratio is determined, ensuring the accuracy and objectivity of partial discharge location, achieving precise location of the partial discharge source, and solving the problem of location distortion caused by the destruction of amplitude-frequency consistency due to parasitic resonance.

[0079] Step 5: In the 3D visualization platform, load the 3D spatial model, mark the sensor's 3D coordinates with different colors, and display the device's 3D permissible domain as a transparent block;

[0080] The candidate source points are visualized by color mapping based on the total residual of the candidate source points. For example, the smaller the total residual of the candidate source point, the closer the color is to red, and the larger the total residual, the closer the color is to blue, which intuitively presents the spatial distribution of the total residual.

[0081] In the three-dimensional spatial model, the local abnormal discharge location results are highlighted with special markers, such as flashing red dots, and their coordinate values ​​are marked.

[0082] Output a 3D visualization interface, which includes the spatial coordinates of substation equipment, the 3D coordinates of sensors, the 3D coordinates of candidate source points, and the local abnormal discharge location results.

[0083] Specifically, the numerical calculation results are transformed into intuitive three-dimensional visualization spatial images, which makes it easier for operators to quickly and intuitively discover the spatial location of local abnormal power discharge in substation equipment, providing direct guidance for equipment maintenance.

[0084] Third Embodiment

[0085] Reference Figure 2 As shown, a three-dimensional visualization substation equipment partial abnormal discharge localization system is proposed to realize a three-dimensional visualization substation equipment partial abnormal discharge localization method, including:

[0086] The comb center generation module acquires the time-domain waveform of the same partial discharge event collected by the UHF sensor. After processing the time-domain waveform through the Hanning window, it performs a discrete Fourier transform to obtain the power spectrum, defines the working band, calculates the mean power spectrum of each sensor channel and the cross-channel spectrum value, determines the free spectrum interval, generates the comb center frequency from the lower limit frequency of the working band with the free spectrum interval as the step size, and maps it to the frequency points to form a comb center set.

[0087] The parasitic index calculation module accumulates the power spectral energy of the comb spectrum at the frequency corresponding to the comb center set, calculates the center frequency of the anti-comb line, maps it to the frequency point, and accumulates its power value to obtain the anti-comb spectrum energy. The comb spectrum energy is divided by the anti-comb spectrum energy to obtain the parasitic leakage index, which reflects the strength of the influence of circumferential parasitic resonance echo on the channel.

[0088] The broadband energy equalization module accumulates the power spectrum power values ​​of all frequency points within the working band to obtain the broadband energy. The broadband energy is then divided by its parasitic leakage index to obtain the equalized broadband energy. This eliminates narrowband amplification interference caused by parasitic resonance, restores the comparability of amplitude and distance attenuation, and ensures that the equalized broadband energy is determined only by the distance from the partial discharge source to the sensor and the propagation path.

[0089] The discharge location calculation module, based on the equalized broadband energy of each sensor channel and combined with the sensor installation position parameters, calculates the three-dimensional spatial coordinates of the local discharge source according to the physical law of amplitude attenuation with distance, and determines the specific location of the local abnormal discharge.

[0090] The 3D visualization module associates the location results of localized discharge with the 3D spatial model, and uses visualization technology to display the spatial location of the discharge point in the equipment, realizing the 3D visualization of the localized abnormal discharge location results, which facilitates the operation and maintenance personnel to accurately identify the discharge location.

[0091] The above embodiments are only used to illustrate the technical methods of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical methods of the present invention without departing from the spirit and scope of the technical methods of the present invention.

Claims

1. A three-dimensional visualization method for locating partial abnormal discharges in substation equipment, characterized in that, include: The time-domain waveform of the same partial discharge event is acquired by an ultra-high frequency sensor. The power spectrum is obtained by performing a discrete Fourier transform on the time-domain waveform. The power spectrum includes the power values ​​of frequency points marked at different frequency positions in the sensor channel. The power spectrum mean is obtained. The frequency interval to be tested is preset. The cross-channel spectrum value is calculated based on the product of the difference between the power values ​​of the two frequency points of the frequency interval to be tested and the power spectrum mean. The frequency interval to be tested with the largest cross-channel spectrum value is marked as the free spectrum interval by traversal test. The comb center frequency is generated sequentially with the free spectrum interval as the step size. Each comb center frequency is mapped to the frequency point with the closest interval. The comb spectrum energy is obtained by summing the power values ​​of all frequency points corresponding to the center frequencies of the comb lines. The center frequency obtained by adding half of the free spectrum interval to the center frequency of the comb lines is marked as the center frequency of the anti-comb line. The anti-comb spectrum energy is calculated based on the center frequency of the anti-comb line. The value obtained by dividing the comb spectrum energy by the anti-comb spectrum energy is marked as the parasitic leakage index. The value obtained by summing the power values ​​of all frequency points in the power spectrum is marked as the broadband energy. The value obtained by dividing the broadband energy by the parasitic leakage index is marked as the equalized broadband energy. Local abnormal discharges are located based on the equalized broadband energy.

2. The method for locating partial abnormal discharge in substation equipment using three-dimensional visualization according to claim 1, characterized in that, Methods for obtaining the power spectrum mean include: The time-domain waveforms corresponding to each sensor channel are windowed using a Hanning window and then subjected to a Discrete Fourier Transform. The power spectrum of the sensor channel is obtained by taking the modulus of the Discrete Fourier Transform result and squaring it. Define the effective analysis frequency range determined by the ultra-high frequency radiation characteristics of substation equipment and the bandwidth of the sampling system, and mark the effective analysis frequency range as the working band. Within the working band, sum the power values ​​of all frequency points on the power spectrum of each sensor channel, and then divide the sum by the number of frequency points in the working band to obtain the average value of the power spectrum of each sensor channel within the working band, and mark this average value as the power spectrum mean. The number of frequency points is the ratio of the difference between the upper and lower frequency limits within the working band to the frequency resolution, where the frequency resolution is the frequency interval between adjacent frequency points in the discrete Fourier transform.

3. The method for locating partial abnormal discharge in substation equipment using three-dimensional visualization according to claim 1, characterized in that, The calculation methods for cross-channel spectrum values ​​include: The preset test frequency interval is the frequency difference between 0 and the upper limit of the working band. For the same sensor channel, the number of frequency points n within the working band that are spaced at the frequency interval to be measured is calculated by multiplying the difference between the power value of the i-th frequency point and the power spectrum mean by the power value of the frequency point at the (i+)-th frequency interval to be measured by ... The cross-channel spectral values ​​obtained after traversing and testing each frequency interval to be tested and inputting the above calculation process are used to mark the frequency interval to be tested with the largest cross-channel spectral value as the free spectrum interval. The free spectrum interval reflects the frequency difference between two adjacent spectral lines of the parasitic comb spectral line.

4. The method for locating partial abnormal discharge in substation equipment using three-dimensional visualization according to claim 1, characterized in that, The center frequency of the comb includes: Starting from the lower limit frequency of the working band to the upper limit frequency of the working band, the comb center frequency is generated sequentially with the free spectrum interval as the step size. The comb center frequency = the lower limit frequency of the working band + n × free spectrum interval, where n is the order in which the comb center frequencies are generated. Next, each comb center frequency is mapped to the frequency point with the closest frequency interval, and all mapped frequency points are combined into a comb center set, which includes all comb center frequencies aligned with the frequency points.

5. The three-dimensional visualization method for locating partial abnormal discharge in substation equipment according to claim 4, characterized in that, Spectral energy, including: For the m-th sensor channel, the comb spectrum energy of the m-th sensor channel is obtained by summing the power values ​​of the frequency points corresponding to the frequencies of all comb center frequencies in the comb center set. The comb spectrum energy is the total energy of the frequency points corresponding to the parasitic comb spectral lines.

6. The method for locating partial abnormal discharge in substation equipment using three-dimensional visualization according to claim 5, characterized in that, Methods for calculating the energy of an anticomb spectrum include: For the m-th sensor channel, iterate through all the comb center frequencies in the comb center set and calculate the reverse comb center frequency. The specific calculation method is as follows: The center frequency of each comb center in the comb center set, after adding half of the free spectrum interval, is marked as the anti-comb center frequency. The anti-comb center frequency is the reference position of the energy of the parasitic comb spectrum. For the center frequency of the anti-comb line, each anti-comb line center frequency is mapped to the frequency point with the closest frequency interval. The power values ​​of the corresponding frequency points of all anti-comb line center frequencies in the power spectrum are summed to obtain the anti-comb spectrum energy of the m-th sensor channel. The anti-comb spectrum energy is the total energy of the non-comb spectrum reference position.

7. The method for locating partial abnormal discharge in substation equipment using three-dimensional visualization according to claim 6, characterized in that, The calculation methods for equalized broadband energy include: The value obtained by dividing the comb energy of the m-th sensor channel by the anti-comb energy is denoted as the parasitic leakage index. The parasitic leakage index is a dimensionless parasitic leakage index of the m-th sensor channel. For the m-th sensor channel, the summation of the power values ​​at all frequency points within the power spectrum within the working band is marked as the broadband energy of the m-th sensor channel, which is the total energy of the m-th channel within the working band. For the m-th sensor channel, the value obtained by dividing the broadband energy of the m-th sensor channel by the parasitic leakage index of the m-th sensor channel is marked as the equalized broadband energy. The equalized broadband energy is the corrected broadband energy of the m-th sensor channel.

8. The method for locating partial abnormal discharge in substation equipment using three-dimensional visualization according to claim 7, characterized in that, Methods for locating localized anomalous discharges based on equalized broadband energy include: A three-dimensional spatial model is constructed based on the coordinate system within the substation. The three-dimensional coordinates of each UHF sensor in the coordinate system within the substation are obtained. The three-dimensional coordinates of the sensor are calibrated during equipment installation. The geometric allowable domain of the equipment is obtained. The geometric allowable domain of the equipment is the three-dimensional spatial range in which the local discharge power source may exist. The three-dimensional coordinate points within the three-dimensional allowable domain of the equipment are traversed, and the three-dimensional coordinate points within the three-dimensional allowable domain of the equipment are marked as candidate source points. The three-dimensional coordinates of the sensor and the three-dimensional allowable domain of the equipment are imported into the three-dimensional spatial model. Calculate the straight-line distance from each candidate source point to each UHF sensor in three-dimensional space, and mark this straight-line distance as the equivalent distance. The equivalent distance is the spatial distance from the candidate source point to the m-th sensor, which reflects the propagation path length of the signal from the local discharge source to the sensor. For any two sensor channels, the ratio of the equalized broadband energy generation logarithmic amplitudes based on the sensor channels is as follows: The logarithmic amplitude ratio is obtained by taking the natural logarithm of the ratio of the equalized broadband energy of the i-th sensor channel to the equalized broadband energy of the j-th sensor channel. The logarithmic amplitude ratio reflects the logarithmic difference in energy attenuation between the two sensor channels after equalization. For any two sensor channels, a logarithmic distance ratio is generated based on the equivalent distance from the candidate source point to the sensor channel, as follows: The logarithmic distance ratio is obtained by taking the natural logarithm of the ratio of the equivalent distance from the nth candidate source point to the i-th sensor channel to the equivalent distance from the nth candidate source point to the j-th sensor channel. The logarithmic distance ratio reflects the logarithmic difference between the distances from the candidate source point to the two sensors.

9. A three-dimensional visualization method for locating partial abnormal discharges in substation equipment according to claim 8, characterized in that, include: The result of multiplying the logarithmic amplitude ratio and logarithmic distance ratio of each pair of sensor channels corresponding to the same candidate source point, summing them up, and then dividing by the sum of the squares of all the logarithmic distance ratios corresponding to the same candidate source point, is marked as the geometric attenuation ratio coefficient. The geometric attenuation ratio coefficient reflects the proportional relationship between amplitude attenuation and distance attenuation. For each pair of sensors corresponding to the same candidate source point, the square of the difference between the logarithmic amplitude ratio of each pair of sensors and the product of the geometric attenuation ratio coefficient and the logarithmic distance ratio is taken, and the squares of the results of each pair of sensors corresponding to the same candidate source point are summed to obtain the total residual. Within the geometrically permissible domain of the device, all candidate source points are traversed to obtain the candidate source point that minimizes the total residual value, and this candidate source point is marked as the local abnormal discharge location result. The results of locating local abnormal discharges are output to a 3D visualization interface.

10. A three-dimensional visualization substation equipment partial abnormal discharge location system, used to implement the partial abnormal discharge location method as described in any one of claims 1-9, characterized in that, include: The comb center generation module acquires the time-domain waveform of the same partial discharge event collected by the UHF sensor. After processing the time-domain waveform through the Hanning window, it performs a discrete Fourier transform to obtain the power spectrum, defines the working band, calculates the mean power spectrum of each sensor channel and the cross-channel spectrum value, determines the free spectrum interval, generates the comb center frequency from the lower limit frequency of the working band with the free spectrum interval as the step size, and maps it to the frequency points to form a comb center set. The parasitic index calculation module accumulates the power spectrum power value of the comb center set corresponding to the comb energy, calculates the center frequency of the anti-comb, maps it to the frequency point, accumulates its power value to obtain the anti-comb energy, divides the comb energy by the anti-comb energy to obtain the parasitic leakage index, which reflects the strength of the channel affected by the circumferential parasitic resonance echo. The broadband energy equalization module accumulates the power spectrum power values ​​of all frequency points within the working band to obtain the broadband energy. The broadband energy is then divided by its parasitic leakage index to obtain the equalized broadband energy. This eliminates narrowband amplification interference caused by parasitic resonance, restores the comparability of amplitude and distance attenuation, and ensures that the equalized broadband energy is determined only by the distance from the partial discharge source to the sensor and the propagation path. The discharge location calculation module, based on the equalized broadband energy of each sensor channel and combined with the sensor installation position parameters, calculates the three-dimensional spatial coordinates of the local discharge source according to the physical law of amplitude attenuation with distance, and determines the specific location of the local abnormal discharge. The 3D visualization module associates the location results of localized discharge with the 3D spatial model, and uses visualization technology to display the spatial location of the discharge point in the equipment, realizing the 3D visualization of the localized abnormal discharge location results, which facilitates the operation and maintenance personnel to accurately identify the discharge location.

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