46 results about "Modulus maxima" patented technology

The invention is a multi-directional and multi-scale edge detection method of a potential field, and is a technology for fast inversion of a shallow three-dimensional crustal structure based on potential field data. The present invention realizes the calculation of the modulus and argument of the wavelet transform after the coordinate system is rotated by using the directional wavelet transform, thereby realizing the calculation of the modulus maximum points of the wavelet transform along the vertical direction of the gradient vector after the coordinate system rotates at different angles. A method for multiscale fringing of potential fields. The present invention overcomes the shortcomings of the analytical signal method, the Euler deconvolution method, the horizontal derivative method, the multi-scale edge detection method of the potential field, etc., which are not sensitive to directional information, and can quickly obtain the geophysical potential field at different depths. Accurate anomaly boundary position information, thereby generating a more accurate three-dimensional structure map of the shallow crust.

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.

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.

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.

A method for extracting partial discharge characteristics of cross-linked polyethylene high-voltage cables belongs to the technical field of high-voltage cables. The purpose of the present invention is to solve the problem of inaccurate extraction of partial discharge features existing in the current partial discharge detection method for high-voltage cables, and to provide a method for extracting partial discharge features of high-voltage cables. The present invention first utilizes the high-frequency current transformer to realize the acquisition of the metal sheath grounding current signal when the partial discharge of the cross-linked polyethylene high-voltage cable occurs, and then converts the current signal into a digital signal, and then decomposes the digital signal into a wavelet packet and analyzes the The decomposed wavelet packet node coefficients or reconstructed signals are sequentially subjected to modulus maximum extraction and singularity detection, and wavelet packet energy index entropy calculation is performed. Finally, discharge characteristic curves are drawn according to the calculation results to realize the partial discharge characteristics of XLPE high-voltage cables. extraction. The invention can improve the extraction accuracy of cable partial discharge features, and provide technical support for the identification of high-voltage cable partial discharge in the next step.

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.