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46 results about "Modulus maxima" patented technology
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Power distribution network fault positioning method based on wavelet transformation and CNN
ActiveCN108732465ARealize automatic identificationImprove anti-interference abilityFault location by conductor typesInformation technology support systemFeature extractionImage resolution
The invention relates to the power distribution network fault positioning technology field and particularly relates to a power distribution network fault positioning method based on wavelet transformation and the CNN. Wavelet transform multi-scale analysis is utilized to decompose fault current data, in the parallel coordinate system, modulus maxima are calibrated in order, points are connected insequence to form a line graph, and lastly, the line graph is processed to be a grayscale image used as the input of the CNN, the powerful feature extraction capability of the CNN is utilized to extract hidden topological structure features in the data, a machine is enabled to automatically identify the traveling wave head, and the B-type traveling wave ranging method is utilized to realize faultpositioning. The method is advantaged in that shortcomings of not-enough wavelet transform high-scale time resolution, large low-scale noise interference and easy false determination of the travelingwave head are overcome, the parallel coordinate system is utilized to fully combine the characteristics of wavelet transform and the convolutional neural network to achieve high-scale to low-scale automatic search for the traveling wave head, and strong anti-interference ability and high accuracy are achieved.
Owner:GUANGDONG POWER GRID CO LTD +1
Same-tower double-circuit DC transmission line double end range finding method having wave velocity correction
ActiveCN106093708AMitigating Ranging ErrorsFault location by conductor typesElectric power systemEngineering
The invention relates to a same-tower double-circuit DC transmission line double end range finding method having wave velocity correction and belongs to the technical field of electric power system protection. The method includes the following steps: firstly acquiring a line rectification side and inversion side voltage fault component, adopting a phase-model transformation matrix to decouple the voltage fault component and resolve an aerial mode fault component voltage traveling wave; calculating the wavelet transform modulus maxima of the aerial mode fault component voltage traveling wave, obtaining the time t"M, t"N corresponding to the first and the second modulus maxima points; earth faults are arranged every 10 km along the whole length of the same-tower double-circuit DC transmission line and resolving the wave velocities of the earth faults, fitting the wave velocities of the earth faults to obtain an aerial mode wave velocity curve, adopting the iterative method to resolve an aerial mode fault voltage wave velocity v; secondly substituting the aerial mode fault voltage wave velocity v and the time t"M and t"N corresponding to the wavelet transform modulus maxima to a fault range finding formula to resolve x; based on the polarity of the front two modulus maxima points of the aerial mode fault component voltage traveling wave at the rectification side M terminal after head wave alignment, it can be determined that the fault point occurs within a half line length from the rectification side M terminal or out of the half line length.
Owner:KUNMING UNIV OF SCI & TECH
Method for ranging single terminal fault of single outlet power transmission line based on opposite terminal bus reflected wave identification
ActiveCN107632236AImprove accuracyHigh precisionFault locationElectric power systemMeasurement point
The invention relates to a method for ranging the single terminal fault of a single outlet power transmission line based on opposite terminal bus reflected wave identification, and belongs to the technical field of fault ranging of power systems. When a power transmission line has a fault, the method includes the following steps: acquiring three-phase currents of the line from a head terminal of the line and separately resolving a zero modulus component and an aerial modulus component of the three-phase currents; separately performing continuous wavelet transform on the zero modulus componentsand the aerial modulus components to resolve the modulus maxima thereof, and separately determining the time t<0>, t<1> when the zero modulus current travelling wave and the aerial modulus current travelling wave arrive at the measurement point at the head terminal; determining the wave head of the zero modulus current travelling wave of the opposite terminal bus reflected wave, determining the time t<2> when the zero modulus current reflected wave which is reflected by the opposite terminal bus arrives at the measurement point at the head terminal; based on the determined wave head of the zero modulus current travelling wave of the opposite terminal bus reflected wave, determining the wave head of the opposite terminal bus reflected wave that corresponds to the aerial modulus current travelling wave, and determining the time t3 when the measurement point arrives at the head terminal; and resolving the fault distance x by using the wave head of the aerial modulus current travelling wave and a novel fault ranging formula of the wave head of the opposite terminal bus reflected wave.
Owner:YUNNAN POWER GRID +2
Marine internal wave detection algorithm based on multi-scale mathematical morphological feature fusion
InactiveCN109410228APreserve edge featuresEffectively eraseImage enhancementImage analysisPattern recognitionWavelet decomposition
The invention discloses a marine internal wave detection algorithm based on multi-scale mathematical morphological feature fusion, which comprises the following steps: multi-scale edge detection basedon wavelet transform modulus maximum obtains multi-scale edge information; the multi-scale edge detection obtains multi-scale edge information based on wavelet transform modulus maximum. Multi-scalemorphology is used to detect the edges of the low-frequency sub-images after wavelet decomposition. Then the small interference area is erased by using the connected domain method. Multi-scale waveletedge detection results of modulus maxima and multi-scale morphological edge detection results are fused to obtain multi-structure element multi-scale edge detection image. Compared with the existingtexture filtering method, the filtering result of the invention can not only keep the structure information of the image well, but also filter out some unnecessary texture details. The structure detection and the texture filtering algorithm provided by the invention obtain better effects in identifying and maintaining the weak gradient structure, inhibiting and smoothing the multi-scale and stronggradient texture and the like compared with the existing algorithm.
Owner:NANJING UNIV OF SCI & TECH
Ear image recognition method amalgamating wavelet analysis and matrix feature
The invention relates to an ear image recognition method combining wavelet analysis and moment features, which is characterized in that the method comprises following steps: (1) preprocessing collected ear images: using wavelet transform modulus maxima to denoise for the collected ear images, and extracting ear image edge to gain wavelet decomposition modulus maxima edge images in various scales; (2) extracting characteristic value of the ear images: making use of an improved wavelet moment invariants arithmetic to calculate the wavelet moment invariants used for extracting the characteristic value of the ear images; (3) recognizing the ear: processing weighting and classifying the characteristic value of the ear images gained in the step (2), and recognizing the ear. The invention processes to extract the characteristic value of the ear via wavelet modulus maxima and the improved wavelet moment invariants arithmetic, and not only has a high calculation accuracy and a fast calculation speed, but also can improve discrimination of the collected ear images in the environment of poor illumination, illumination change and noise jamming.
Owner:CHONGQING UNIV
Method for extracting lightning strike signals and transient harmonic signals in power system
InactiveCN101655520AInextensiveEnhanced inhibitory effectSpectral/fourier analysisMeasurement using digital techniquesLightning strikeElectric power system
The invention relates to a method for extracting lightning strike signals and transient harmonic signals in a power system, which overcomes the problem of inaccurate extraction of the method for extracting the lightning strike signals and the transient harmonic signals in the power system in the prior art. The method comprises the steps of firstly converting the collected current signals to digital signals, further carrying out fast Fourier transform on the digital signals, determining the sampling frequency and the decomposition scale of wavelet decomposition according to the transform result, then carrying out wavelet decomposition on the digital signals, sequentially carrying out modulus maxima extraction, singularity detection and generalized wavelet entropy calculation on wavelet coefficients or single-branch wavelet reconstruction signals after the decomposition, and finally extracting the lightning strike signals and the transient harmonic signals according to the calculation result. The method can overcome the deficiencies of the prior art and be applicable to representing information features of the lightning signals and the transient harmonic signals in the time-frequencydomain.
Owner:HARBIN INST OF TECH
Crosslinked polyethylene high-voltage cable partial discharge feature extraction method
ActiveCN104765971AImprove extraction accuracyAvoid undefined valuesTesting dielectric strengthSpecial data processing applicationsEngineeringCross-linked polyethylene
The invention provides a crosslinked polyethylene high-voltage cable partial discharge feature extraction method, and belongs to the technical field of high-voltage cables. The high-voltage cable partial discharge feature extraction method aims to solve the problem that partial discharge feature extraction is inaccurate in an existing high-voltage cable partial detection method. According to the method, firstly, metal sheath grounding current signals generated when crosslinked polyethylene high-voltage cable partial discharge happens is acquired through a high-frequency current mutual inductor; then, current signals are converted into digital signals; next, wavelet packet decomposition is conducted on the digital signals, modulus maxima extraction and singularity detection are sequentially conducted on decomposed wavelet packet node coefficients or reconstructed signals, and wavelet packet energy index entropy calculation is conducted; finally, a discharge feature curve is drawn according to the operation result, and crosslinked polyethylene high-voltage cable partial discharge feature extraction is achieved. By means of the crosslinked polyethylene high-voltage cable partial discharge feature extraction method, the cable partial discharge feature extraction accuracy can be improved, and technical support is provided for next high-voltage cable partial discharge.
Owner:NORTHEAST DIANLI UNIVERSITY +2
Power distribution network system's electric energy quality disturbance positioning and identifying method
InactiveCN106940407AHigh precisionHigh speedElectrical testingNeural learning methodsPower qualityAdaptive learning
The invention discloses an electric energy quality disturbance positioning and identifying method based on the lifting of the wavelet and the improvement of a BP neural network. The method comprises the following steps: using the Euclidean decomposition algorithm to obtain a db4 wavelet lifting scheme; performing lifting wavelet decomposition to the disturbance signal; in combination with the modulus maxima, performing the positioning detection to the disturbance mutation point peak; and utilizing the method of combining the self-adaptive learning rate with the incremental momentum term to improve and carry out disturbance identification to the BP neural network. The method of the invention can better obtain the disturbance period information, achieves fast positioning and high precision, and overcomes the shortcoming that a traditional BP neural network is prone to fall into local minimal points and slow convergence speed, therefore, achieving a high identifying rate for the power distribution network system's electric energy quality disturbance.
Owner:XIANGTAN UNIV
Novel double end fault location method for double DC circuits on same tower
ActiveCN106019079AThe principle is simpleThe ranging result is accurate and reliableFault location by conductor typesElectrical resistance and conductanceElectric power system
The invention relates to a novel double end fault location method for double DC circuits on same tower and belongs to the technical field of power system relay protection. The method includes steps of obtaining voltage of a measuring end M and a measuring end N and solving a fault component and solving a line mode voltage component by adopting phase mode conversion when the double DC circuits on same tower meets a grounding fault; applying a Bergeron transfer equation and the measuring end line mode voltage component for calculating line-side voltage and current travelling wave variations; cubing a product of the line-side voltage traveling wave variation of the a measuring end M and the line-side current traveling wave variation of the measuring end N and constructing a fault location function through integrating in an observation time window; realizing fault location through combining line-side mutation rules of the fault location function and the polarity of the wavelet transform modulus maxima of fault voltage traveling waves. According to the invention, fault location is performed for the double DC circuits on same tower and the principle is simple. Wave heads of the fault traveling waves do not need to marked and influence caused by fault instantaneity, fault transition resistance variation and the like is eliminated. The fault location result is accurate and reliable.
Owner:KUNMING UNIV OF SCI & TECH
Fetal electrocardiogram signal extracting method based on wavelet threshold denoising
InactiveCN102783945ASuppress heart rateEfficient and accurate extractionDiagnostic recording/measuringSensorsEcg signalDenoising algorithm
The invention discloses a fetal electrocardiogram signal extracting method based on wavelet threshold denoising. The method comprises the following steps of: carrying out stationary wavelet transform processing on a maternal abdomen signal, and decomposing to obtain each layer of wavelet coefficient; independently processing each layer of wavelet detail coefficient, removing fetal electrocardiogram wavelet coefficients, reconstructing remained maternal electrocardiogram wavelet coefficients, and obtaining maternal electrocardiogram in the abdomen signal; removing the reconstructed maternal electrocardiogram from the abdomen signal to obtain a fetal electrocardiogram signal; and denoising the extracted fetal electrocardiogram by utilizing a wavelet correlation denoising algorithm to obtain a clear fetal electrocardiogram signal. Due to the method, the accurate extraction of the fetal electrocardiogram signal can be realized. The method is based on a single channel, the computation of wavelet transform modulus maxima is avoided, and better instantaneity is realized.
Owner:BEIJING UNIV OF TECH
Method for identifying oil spilling and suspected object in SAR dark shadow image
InactiveCN102831444AImprove computing efficiencyCharacter and pattern recognitionFeature vectorSynthetic aperture radar
The invention discloses a method for identifying oil spilling and suspected objects in an SAR (synthetic aperture radar) dark shadow image. The method comprises inputting an SAR image, establishing an oil-spilling image library and a suspected object image library; choosing M pictures at random to form a training sample image library, calculating a fractal characteristic vector of each image in the training sample image library by using a difference box counting method and a wavelet transformation modulus maxima method, forming a training sample set; using the training sample set and labels of the training samples to train an SVM grader; determining a to-be-identified dark shadow area in the SAR image by using a self-adaptive threshold value method, scanning spots pixel by pixel in the dark shadow area, calculating fractal characteristic vector thereof to form a test sample set; and using the trained SVM grader to classify test samples, and outputting a classification result. The method has relatively high operation efficiency, and can be used in identification and classification of oil spilling and suspected objects in the SAR dark shadow image.
Owner:JIANGSU UNIV OF SCI & TECH
Bearing outer ring surface defect area detection method
PendingCN112862760AImprove accuracyImprove robustnessImage enhancementImage analysisMultiscale decompositionStructural engineering
The invention discloses a method for detecting a surface defect area of a bearing outer ring. The method comprises the steps: carrying out multi-scale decomposition on an original bearing outer ring image, solving modulus maxima of each scale, and realizing edge preselection of a defect area of the bearing outer ring; clustering the edge of the defect area on the surface of the bearing outer ring to obtain each cluster, and calculating the center of each cluster to determine a growth seed point of the defect area; taking the growth seed point as a base point, taking four neighborhood pixels of the base point as a to-be-selected growth point set, traversing each pixel in the to-be-selected growth point set, and judging whether a growth termination condition is met or not so as to realize the detection of the surface defect area of the bearing outer ring. According to the bearing outer ring surface defect area detection method, higher accuracy is shown when the problem of multi-surface multi-type defect detection of the bearing outer ring is solved, meanwhile, the robustness is higher, the method can adapt to surface defect area detection under different brightness and illumination conditions, and the detection effect better than that of other bearing surface defect detection algorithms is obtained.
Owner:ZHEJIANG UNIV
Cable low-resistance fault positioning method using single-end and double-end combination
ActiveCN106841918AAvoid wave aliasingUncertainty impactFault location by conductor typesEngineeringLow resistance
A cable low-resistance fault positioning method using single-end and double-end combination includes the steps that fault traveling waves are collected at the two ends of a cable respectively; denoising processing is conducted to obtain a denoised signal; wavelet transformation is conducted, and modulus maximas are solved; first Y modulus maximas at each end are obtained; an absolute value maximum value and an absolute value secondary maximum value in the first Y modulus maximas at each end are selected; the ratio of the absolute value maximum value to the absolute value secondary maximum value at each end is obtained; whether the two ratios are smaller than or equal to a preset threshold is judged; if the two judgment results are both positive, two-end fault positioning is conducted; if any of the two judgment result is negative, single-end fault positioning is conducted on the end where the smaller ratio in the two ratios is located. By means of the method, two-end fault positioning and single-end fault positioning can be flexibly used according to conditions by means of fault positioning and classifying of the two ends, and the method has the technical advantage that fault positioning is accurate.
Owner:SOUTH CHINA UNIV OF TECH +1
Through type cophase traction power supply system traction network fault interval traveling wave positioning method
InactiveCN105203917AImprove power supply reliabilityNarrow down the scope of troubleshootingFault locationData acquisitionTraction power supply
The invention relates to a through type cophase traction power supply system traction network fault interval traveling wave positioning method, and belongs to the technical field of electrified railway traction network fault interval positioning research. The method comprises the steps that A, after a fault occurs on a through type cophase traction power supply system traction network, the data acquisition devices of all traction substations acquire current within 10ms time window after occurrence of the fault; B, the fault current signal wavelet transform modulus maxima of the outlet of each traction substation is obtained; and C, the polarities of the current traveling wave signal modulus maximas of all the outputs are compared. If the polarities of the fault current traveling wave modulus maximas of the two adjacent traction substations are opposite, the fault occurs between the two traction substations; or the fault position is not between the two traction substations. According to the method, the through type cophase traction power supply system fault interval traveling wave positioning method is indicated to be accurate and reliable through the simulation result.
Owner:KUNMING UNIV OF SCI & TECH
Equal-even length anti-symmetrical biorthogonal wavelet filter group based edge detection method
InactiveCN104036508AAccurate borderImprove the speed of edge detectionImage enhancementImage analysisWavelet decompositionBiorthogonal wavelet
The invention discloses an equal-even length anti-symmetrical biorthogonal wavelet filter group based edge detection method. The equal-even length anti-symmetrical biorthogonal wavelet filter group based edge detection method comprises the following steps of performing three-layer wavelet decomposition on an image through an equal-even length anti-symmetrical biorthogonal wavelet by a Mallat algorithm; calculating a gradient vector modulus value graph and a phase angle graph according to every scale of wavelet decomposition data of the image; detecting a modulus maxima point of every scale according to the direction determined by the phase angle graph; removing pseudo boundary points by a threshold value method; integrating obtained scales of boundary point sets so as to obtain the accurate single pixel width of boundary. According to the equal-even length anti-symmetrical biorthogonal wavelet filter group based edge detection method, the wavelet decomposition is performed through an equal-even length anti-symmetrical biorthogonal wavelet filter group with the differential operator function, the boundary information of every scale is comprehensively utilized, and accordingly the integrity and the accuracy of edge detection of the image are improved and certain anti-noise performance is achieved.
Owner:SHANDONG UNIV
Traveling wave fault detection and locating method under IEC61850 standard
InactiveCN106483428AImprove detection accuracyImprove securityFault location by conductor typesInformation technology support systemExtensibilityElectrical polarity
The invention discloses a traveling wave fault detection and locating method under the IEC61850 standard. The implementation process of the method includes the following steps that: 1) a traveling wave fault locating system model under the IEC 61850 standard is constructed; 2) traveling wave signals are collected through the traveling wave fault locating system model; 3) the traveling wave signals are pre-processed; 4) wavelet transformation is performed on signals obtained after pre-processing, so that modulus maxima can be obtained, and locations where singular points are located are found out; and 5) after the locations of the singular points are obtained, a fault distance is calculated through the locations of spike pulses of which the polarities are opposite in waveforms. The traveling wave fault detection and locating method under the IEC61850 standard of the invention has the advantages of accurate and reliable alternating-current and direct-current fault locating, high safety, high reliability and excellent expandability.
Owner:STATE GRID CORP OF CHINA +2
Fault starting method, system and high-voltage power transmission line relay protection system
ActiveCN107482596ACurrent/voltage measurementEmergency protective circuit arrangementsEngineeringReaction speed
The present invention provides a fault starting method, a system and a high-voltage power transmission line relay protection system, wherein the fault starting method comprises: acquiring at least one first current value at preset intervals in a first period; determining the current sudden change sub-value corresponding to each current value and determining the sudden change value corresponding to the current sudden change sub-value; determining the average of the wavelet model corresponding to the sudden change value; and if the average of the wavelet model satisfies a preset formula, determining that the fault start-up is executed when the first current value time is collected. Through the technical scheme of the invention, the singularity of the signal is reflected by the integrated average of the modulus maxima, and the reaction speed can be promptly responded to various kinds of line faults. The movement speed is improved, and the accurate judgment of the no-action action is performed when the noise interference and the pulse interference are disturbed, making the system more reliable.
Owner:TSINGHUA UNIV
Post-wavelet analysis treating method and device for electric power transient signal
InactiveCN100520425CMeet the requirements of high transmission rateFault locationElectric power transmissionPower quality
The invention discloses a wavelet analysis post-processing method and device for a power transient signal. The method is to conduct the following one or more post-processing on the wavelet coefficients after the power transient signal is analyzed by wavelet, and the result is to send power Monitoring center processing: modulus maximum extraction, singularity detection, obtaining modulus maximum points and singularity; statistical processing or cluster analysis of wavelet coefficients; neural network classification, that is, wavelet coefficients or wavelet post-processed data as neural Network input, output neural network classification results; energy analysis, to obtain energy distribution coefficient and energy fluctuation coefficient; wavelet entropy calculation, to obtain wavelet energy spectrum entropy or wavelet time entropy or wavelet singular entropy or wavelet time-frequency entropy or wavelet average entropy or wavelet distance entropy. It can effectively extract the characteristics of power transient signals, which can be applied to power system transmission line traveling wave distance measurement and fault identification, power quality analysis and equipment fault diagnosis.
Owner:SOUTHWEST JIAOTONG UNIV
Orbit period identification method based on wavelet transform modulus maxima algorithm
InactiveCN106199726AEasy to implementSeismic signal processingSeismology for water-loggingWell loggingEuclidean vector
The invention relates to an orbit period identification method based on a wavelet transform modulus maxima algorithm, and belongs to the technical field of geophysics, and aims at solving the problems that in the prior art, intuitive qualification and intuitive quantification are different, and implementation is difficult. The method comprises the following steps that 1, a continuous wavelet transform coefficient matrix of a one-dimensional well logging curve model is solved; 2, an absolute value of the wavelet transform coefficient matrix obtained in the step 1 is solved; 3, an average value of each line of the absolute value matrix obtained in the step 2 is solved, and then the average values form a column vector; 4, a sequence extreme point of the column vector obtained in the step 3 is solved; 5, the scale corresponding to the extreme point is a response of a preferred period, and the size of the preferred period is converted through a corresponding relation expression of the frequency and the scale in wavelet analysis; 6, an energy spectrum diagram is obtained through wavelet analysis, and then the ratio of the energy ring number is obtained. According to the method, modulus maxima operation is conducted with the help of the continuous wavelet transform energy spectrum diagram, and therefore not only are intuitive qualification and intuitive quantification combined, but also implementation is convenient and rapid.
Owner:SHANDONG UNIV OF SCI & TECH
Small current line selection method utilizing wavelet analysis
InactiveCN110554272ALine selection is accurateHigh speedFault location by conductor typesComplex mathematical operationsTransient stateElectrical polarity
The invention discloses a small current line selection method using wavelet analysis. Wavelet transform and modulus maximum representation thereof can accurately score fault characteristics of transient traveling waves; the method has a step of extracting grounded traveling wave information to form effective grounding line selection criterion; initial transient traveling waves of a fault line anda sound line have obvious characteristic difference. Therefore, the modulus maximum value of wavelet transform is used for representing the amplitude and polarity characteristics of the initial traveling wave on each line; according to the method, the fault line selection criterion can be formed according to the amplitude and polarity difference of the modulus maxima of the initial traveling wavesof all the lines, and line selection is accurate and high in speed according to the amplitude and polarity difference of the modulus maxima of the initial traveling waves of all the lines by means ofthe wavelet analysis small current line selection method.
Owner:江苏莱尔曼电气科技有限公司
Method for checking margin of potential field polydirectionally and multiple dimensions
ActiveCN100559400COvercome the shortcomings of directional information insensitivityImage enhancement3D modellingBit fieldPotential field
Owner:INST OF MINERAL RESOURCES CHINESE ACAD OF GEOLOGICAL SCI
A new double-terminal fault location method for double-circuit DC lines on the same tower
ActiveCN106019079BThe principle is simpleThe ranging result is accurate and reliableFault location by conductor typesElectrical resistance and conductanceElectric power system
Owner:KUNMING UNIV OF SCI & TECH
A double-terminal fault location method for double-circuit DC transmission lines on the same tower with wave velocity correction
ActiveCN106093708BMitigating Ranging ErrorsFault location by conductor typesElectric power systemEngineering
Owner:KUNMING UNIV OF SCI & TECH
A fault signal analysis method based on complex wavelet modulus maxima connection line
InactiveCN109086248AQuick pickComplex wavelet vanishing momentComplex mathematical operationsVanishing momentsAlgorithm
The invention discloses a fault signal analysis method based on a complex wavelet modulus maximum connecting line, which comprises steps that: the fault signal is obtained and processed by continuouswavelet transform; the vanishing moment of complex wavelet is optimized and the vanishing moment of complex wavelet is judged to be optimal; then the order n of vanishing moment is chosen to be greater than Lipschitz exponent alpha and the complex wavelet transform is carried out; the modulus maxima of continuous wavelet transform coefficients are plotted; the singular point x0 is determined alongthe modulus maxima connection line, and the corresponding slope of log2 | Wf (s, k) | along the modulus maxima connection line converging to x0 is calculated, which slope is alpha + 1 / 2, so that theLipschitz exponent alpha at x0 point is obtained. Compared with the prior art, the invention has strong practical function, simple steps and can be extended to the singularity analysis of other signals.
Owner:XIAN UNIV OF SCI & TECH
Wireless positioning method based on wavelet transform modulus maxima
PendingCN114222241ALocation information based serviceComplex mathematical operationsMulti resolution analysisAlgorithm
The invention belongs to the technical field of wireless positioning, and relates to a wireless positioning method based on a Wavelet Transform (WT) modulus maximum value. The method mainly comprises the following steps of: performing multi-resolution analysis (MRA) on a signal at a signal preprocessing end; solving modulus maxima of each scale according to the wavelet transform coefficient on each scale; selecting a proper threshold value to process the modulus maximum value, and reserving extreme points greater than or equal to the threshold value; from the highest scale J to the scale 1, searching a propagation point of a modulus maximum value on an adjacent scale, and according to a propagation rule that the modulus extreme values of the signal and the noise are different, retaining the modulus extreme points of the signal and removing the modulus extreme points of the noise; and the processed modulus maximum point is utilized to reconstruct a signal for subsequent conventional positioning operation. According to the method, the signal noise reduction effect can be greatly improved, the signal-to-noise ratio (SNR) is improved, the positioning precision is improved, and convenience is provided for positioning.
Owner:CHINA UNIV OF PETROLEUM (EAST CHINA)
A Method of Using Wavelet Transform to Extract Vibration Signal Index Quantities Characterizing the Operating State of On-load Tap Switches
ActiveCN104748837BAccurate time calculationEasy to detectMachine part testingSubsonic/sonic/ultrasonic wave measurementElectric power systemSwitching time
The invention provides a method for extracting a vibration signal index quantity representing the operating state of an on-load tap changer by using wavelet transform, which belongs to the field of power system fault detection. After obtaining the envelope of the high-frequency vibration signal of the on-load tap changer, the maximum value of the wavelet transform modulus is obtained for the envelope of the high-frequency vibration signal, and the maximum value of the modulus is used to accurately extract the difference between the first mutation amount and the largest mutation amount. Time t1 and switch switching action time t2, and then use t1 and t2 to obtain the maximum amplitude f1 and f2 in the vibration high-frequency signal envelope within two periods of time, and use t2, f1 and f2 to judge the operating state of the on-load tap changer . When f1 is greater than the threshold value, it is judged that the driving mechanism of the OLTC is insufficiently lubricated, otherwise, it is normal; when t2 is not within the threshold range and f2 is less than the threshold value, it is judged that the spring force of the OLTC is weakened, and on the contrary , it is normal. The simulation experiment proves that the method transforms the analysis of the sudden vibration signal into the analysis of its modulus maximum value, and the method is effective.
Owner:XISHUANGBANNA POWER SUPPLY BUREAU OF YUNNAN POWER GRID CO LTD +1
BP neural network-based power distribution network fault section positioning method
InactiveCN112710920AOvercome the problem of positioning misjudgmentImprove accuracyFault locationTransient stateCurrent sample
The invention discloses a power distribution network fault section positioning method based on a BP neural network. The method comprises steps of firstly obtaining transient zero-sequence current sampling data in a 1 / 2 cycle after a single-phase grounding fault moment according to zero-sequence current collection equipment installed in a power distribution network; wavelet analysis being carried out on the measured transient zero-sequence current along the line under different fault sections to obtain a corresponding modulus maximum value; taking a certain number of transient zero-sequence current modulus maxima obtained under different fault sections and inputting the modulus maxima into the BP network for training to obtain a relationship between the modulus maxima and the fault sections; wavelet transformation being carried out on a group of transient zero-sequence current data of an actual fault to obtain a modulus maximum value, trained BP parameters being read in for testing, and a fault section positioning result being obtained. The method can avoid the influence caused by the branch line, and is not affected by the cable overhead hybrid line.
Owner:WENZHOU ELECTRIC POWER BUREAU +2
A Feature Extraction Method for Partial Discharge of XLPE High Voltage Cable
ActiveCN104765971BImprove extraction accuracyOvercome deficienciesTesting dielectric strengthSpecial data processing applicationsPresent methodEngineering
Owner:NORTHEAST DIANLI UNIVERSITY +2
A single-ended traveling wave ranging method for double-circuit DC lines on the same tower based on energy mutation along the line
ActiveCN106019080BThe principle is simpleThe ranging result is accurate and reliableFault locationElectrical resistance and conductanceElectric power system
The invention relates to a line-side energy mutation based single-end travelling wave fault location method for double DC circuits on the same tower and belongs to the technical field of power system relay protection. The method includes steps of obtaining voltage of a measuring end and solving a fault component and solving a line mode voltage component by adopting phase mode conversion when the double DC circuits on same tower meets a grounding fault; applying a Bergeron transfer equation and the measuring end line mode voltage component for calculating line-side voltage and current travelling wave variations; cubing a product of the line-side voltage traveling wave variation and the line-side current traveling wave variation and constructing a fault location function through integrating in an observation time window; realizing fault location through combining line-side mutation rules of the fault location function and the polarity of the wavelet transform modulus maxima of fault voltage traveling waves. According to the invention, fault location is performed for the double DC circuits on same tower and the principle is simple. Wave heads of the fault traveling waves do not need to marked and influence caused by fault instantaneity, fault transition resistance variation and the like is eliminated. The fault location result is accurate and reliable.
Owner:KUNMING UNIV OF SCI & TECH
Method for identifying oil spilling and suspected object in SAR dark shadow image
InactiveCN102831444BImprove computing efficiencyCharacter and pattern recognitionFeature vectorSynthetic aperture radar
The invention discloses a method for identifying oil spilling and suspected objects in an SAR (synthetic aperture radar) dark shadow image. The method comprises inputting an SAR image, establishing an oil-spilling image library and a suspected object image library; choosing M pictures at random to form a training sample image library, calculating a fractal characteristic vector of each image in the training sample image library by using a difference box counting method and a wavelet transformation modulus maxima method, forming a training sample set; using the training sample set and labels of the training samples to train an SVM grader; determining a to-be-identified dark shadow area in the SAR image by using a self-adaptive threshold value method, scanning spots pixel by pixel in the dark shadow area, calculating fractal characteristic vector thereof to form a test sample set; and using the trained SVM grader to classify test samples, and outputting a classification result. The method has relatively high operation efficiency, and can be used in identification and classification of oil spilling and suspected objects in the SAR dark shadow image.
Owner:JIANGSU UNIV OF SCI & TECH
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