A cable fault point locating method and system

Abstract

The present invention relates to a cable fault point locating method and system, specifically, comprising obtaining a reflection coefficient spectrum of a cable, calculating an upper envelope and a lower envelope of the reflection coefficient spectrum, smoothing the upper envelope and the lower envelope, and denoising the reflection coefficient spectrum using a curve between the upper envelope and the lower envelope after the smoothing process; obtaining a plurality of partially overlapping intervals from the denoised reflection coefficient spectrum, performing integral transformation on the reflection coefficient spectrum of each interval using a plurality of different window functions, taking the average value of the integral transformation results of all window functions in the same interval as the fault locating curve of the interval, obtaining the position of the maximum value point of each interval, grouping the positions according to the proximity of the positions, and taking the average value of the positions in the same group as the position of the cable fault.

Description

Technical Field

[0001] The present invention relates to the electric power field, and in particular to a cable fault point locating method and system. Background Art

[0002] As an infrastructure, cables are the basic carriers of power transmission and distribution, ensuring the normal and stable power supply. However, during the manufacturing and transportation process, cables cannot avoid collisions and extrusions. In addition, during use, due to harsh environmental conditions, they may experience aging, insulation damage, or partial discharge. If these problems are not discovered and resolved in time, they may cause cable performance degradation or even failure, leading to power outages or communication failures. Cable fault location can accurately identify and determine the type, location, and severity of the fault, which can not only significantly reduce downtime and maintenance costs; but also through early detection and control of faults, it can effectively extend the service life of the cable, improve resource utilization efficiency, and reduce safety hazards and social and economic losses caused by cable failures.

[0003] Reflection coefficient spectrum analysis technology is an important way to locate cable faults. Its basic principle is to determine the reflection intensity and position of the signal at different fault locations by analyzing the reflection characteristics of the test signal in the cable. However, in practical applications, due to factors such as environmental noise in the cable line, nonlinear errors of the test equipment itself, and attenuation and multipath interference during signal propagation, there is often serious noise pollution in the reflection coefficient spectrum. These noises not only mask the detailed characteristics of the fault signal, but may also cause errors in fault location and even misjudgment. Effectively removing noise while retaining the characteristics of the fault signal is very helpful in improving positioning accuracy. Summary of the invention

[0004] In order to improve the accuracy of cable fault location, a cable fault point location method is provided in a first aspect of the present invention, the method comprising the following steps:

[0005] Acquire a reflection coefficient spectrum of the cable, calculate an upper envelope and a lower envelope of the reflection coefficient spectrum, smooth the upper envelope and the lower envelope, and denoise the reflection coefficient spectrum using a curve between the upper envelope and the lower envelope after the smoothing process;

[0006] Multiple partially overlapping intervals are obtained from the denoised reflection coefficient spectrum, and the reflection coefficient spectrum of each interval is integrally transformed using multiple different window functions. The average value of the integral transformation results of all window functions in the same interval is used as the fault location curve of the interval, and the position of the maximum point of each interval is obtained. The positions are grouped according to their proximity, and the average value of the positions in the same group is used as the position of the cable fault point.

[0007] Optionally, the smoothing of the upper envelope and the lower envelope is specifically performed as follows:

[0008] Calculate the average value of the upper envelope and the lower envelope to form the middle curve;

[0009] Take multiple reference points from the middle curve, calculate the distance from each reference point to the upper envelope to form an upper envelope distance set, and calculate the distance from each reference point to the lower envelope to form a lower envelope distance set;

[0010] Gaussian filtering is performed on the upper envelope distance set and the lower envelope distance set respectively, and the upper envelope distance set and the lower envelope distance set after filtering are averaged to obtain a reference set;

[0011] Adjust the positions of the points in the upper and lower envelopes that correspond to the distances in the reference set according to the distances in the reference set.

[0012] Optionally, the denoising of the reflection coefficient spectrum is performed by using the curve between the smoothed upper envelope and the lower envelope, specifically:

[0013] Obtaining the point in the upper envelope corresponding to the maximum value in the reflection coefficient spectrum as the characteristic point of the upper envelope, and obtaining the point in the lower envelope corresponding to the minimum value in the reflection coefficient spectrum as the characteristic point of the lower envelope;

[0014] Calculate the normal vector of the feature point of the upper envelope, and obtain the intersection of the normal vector and the lower envelope, and use the line segment formed by the feature point of the upper envelope and the corresponding intersection as the feature line segment; calculate the normal vector of the feature point of the lower envelope, and obtain the intersection of the normal vector and the upper envelope, and use the line segment formed by the feature point of the lower envelope and the corresponding intersection as the feature line segment;

[0015] Taking a preset number of points at equal intervals on each characteristic line segment, and sorting the preset number of points on each characteristic line segment according to the distance from the upper envelope line;

[0016] Take out the points with the same serial number in each characteristic line segment and perform curve fitting to obtain the curve between the upper and lower envelopes;

[0017] Dividing the reflection coefficient spectrum into a plurality of regions according to the maximum and minimum values, wherein the regions are composed of adjacent maximum and minimum value regions;

[0018] Calculate the number of intersections of each curve between the reflection coefficient spectrum and the upper and lower envelope lines in each region. If the number of intersections is greater than 1, obtain the previous and next curves of the curve with the number of intersections greater than 1, and use the intersections of the previous and next curves with the reflection coefficient spectrum in the region to regenerate the curve between the intersections of the previous and next curves with the reflection coefficient spectrum in the region.

[0019] Optionally, the step of obtaining a plurality of partially overlapping intervals from the denoised reflection coefficient spectrum is specifically as follows:

[0020] A frequency range in the reflection coefficient spectrum is obtained, and a plurality of partially overlapping intervals are obtained within the frequency range, wherein a ratio of a length of each interval to the frequency range is greater than a preset value.

[0021] Optionally, after obtaining the position of the maximum point of each interval, the method further includes:

[0022] Determine whether the position of the maximum point is within the preset range. If so, keep the maximum point; otherwise, delete the maximum point.

[0023] On the other hand, the present invention provides a cable fault point locating system, the system comprising the following modules:

[0024] A denoising module, used for obtaining a reflection coefficient spectrum of the cable, calculating an upper envelope and a lower envelope of the reflection coefficient spectrum, smoothing the upper envelope and the lower envelope, and denoising the reflection coefficient spectrum using a curve between the smoothed upper envelope and the lower envelope;

[0025] The fault location module is used to obtain multiple partially overlapping intervals from the denoised reflection coefficient spectrum, use multiple different window functions to perform integral transformation on the reflection coefficient spectrum of each interval, take the average value of the integral transformation results of all window functions in the same interval as the fault location curve of the interval, obtain the position of the maximum point of each interval, group the positions according to their proximity, and take the average value of the positions in the same group as the position of the cable fault point.

[0026] Optionally, the smoothing of the upper envelope and the lower envelope is specifically performed as follows:

[0027] Calculate the average value of the upper envelope and the lower envelope to form the middle curve;

[0028] Take multiple reference points from the middle curve, calculate the distance from each reference point to the upper envelope to form an upper envelope distance set, and calculate the distance from each reference point to the lower envelope to form a lower envelope distance set;

[0029] Gaussian filtering is performed on the upper envelope distance set and the lower envelope distance set respectively, and the upper envelope distance set and the lower envelope distance set after filtering are averaged to obtain a reference set;

[0030] Adjust the positions of the points in the upper and lower envelopes that correspond to the distances in the reference set according to the distances in the reference set.

[0031] Optionally, the denoising of the reflection coefficient spectrum is performed by using the curve between the smoothed upper envelope and the lower envelope, specifically:

[0032] Obtaining the point in the upper envelope corresponding to the maximum value in the reflection coefficient spectrum as the characteristic point of the upper envelope, and obtaining the point in the lower envelope corresponding to the minimum value in the reflection coefficient spectrum as the characteristic point of the lower envelope;

[0033] Calculate the normal vector of the feature point of the upper envelope, and obtain the intersection of the normal vector and the lower envelope, and use the line segment formed by the feature point of the upper envelope and the corresponding intersection as the feature line segment; calculate the normal vector of the feature point of the lower envelope, and obtain the intersection of the normal vector and the upper envelope, and use the line segment formed by the feature point of the lower envelope and the corresponding intersection as the feature line segment;

[0034] Taking a preset number of points at equal intervals on each characteristic line segment, and sorting the preset number of points on each characteristic line segment according to the distance from the upper envelope line;

[0035] Take out the points with the same serial number in each characteristic line segment and perform curve fitting to obtain the curve between the upper and lower envelopes;

[0036] Dividing the reflection coefficient spectrum into a plurality of regions according to the maximum and minimum values, wherein the regions are composed of adjacent maximum and minimum value regions;

[0037] Calculate the number of intersections of each curve between the reflection coefficient spectrum and the upper and lower envelope lines in each region. If the number of intersections is greater than 1, obtain the previous and next curves of the curve with the number of intersections greater than 1, and use the intersections of the previous and next curves with the reflection coefficient spectrum in the region to regenerate the curve between the intersections of the previous and next curves with the reflection coefficient spectrum in the region.

[0038] Optionally, the step of obtaining a plurality of partially overlapping intervals from the denoised reflection coefficient spectrum is specifically as follows:

[0039] A frequency range in the reflection coefficient spectrum is obtained, and a plurality of partially overlapping intervals are obtained within the frequency range, wherein a ratio of a length of each interval to the frequency range is greater than a preset value.

[0040] Optionally, after obtaining the position of the maximum point of each interval, the method further includes:

[0041] Determine whether the position of the maximum point is within the preset range. If so, keep the maximum point; otherwise, delete the maximum point.

[0042] In order to eliminate the influence of noise on cable fault location, the present invention uses the curve between the upper envelope and the lower envelope of the smoothed reflection coefficient spectrum to denoise the reflection coefficient spectrum; and uses different window functions to perform integral transformation on different frequency ranges of the reflection coefficient spectrum, and then uses the integral transformation results of different frequency ranges to determine the fault position, thereby improving the accuracy of cable fault location. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a flow chart of Embodiment 1;

[0044] Figure 2 is a schematic diagram of the reflection coefficient spectrum;

[0045] Figure 3 It is a schematic diagram of the upper and lower envelopes of the reflection coefficient spectrum;

[0046] Figure 4 It is a schematic diagram of characteristic line segments and points on the characteristic line segments;

[0047] Figure 5 A schematic diagram showing the use of the curve between the upper and lower envelopes to determine the noise area;

[0048] Figure 6 This is a comparison chart of the reflection coefficient spectrum before and after denoising;

[0049] Figure 7 A comparison chart of the integral transformation of the reflection coefficient spectrum in different frequency ranges. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0051] Embodiment 1, in this embodiment, provides a method for locating a cable fault point, such as Figure 1 As shown, the method comprises the following steps:

[0052] Step 1, obtaining a reflection coefficient spectrum of the cable, calculating an upper envelope and a lower envelope of the reflection coefficient spectrum, smoothing the upper envelope and the lower envelope, and denoising the reflection coefficient spectrum using a curve between the smoothed upper envelope and the lower envelope;

[0053] When locating cable faults, a network analyzer such as a vector network analyzer is used to obtain the reflection coefficient spectrum of the cable. The network analyzer transmits a sweep signal to one end of the cable through a sweep signal generator, collects the reflected signal, extracts the reflection coefficient based on the incident signal and the reflected signal, and then forms a reflection coefficient spectrum. Figure 2 A schematic diagram of a reflection coefficient spectrum is shown. Figure 2It can be seen that the horizontal axis of the reflection coefficient spectrum is the frequency, and the vertical axis is the normalized reflection coefficient amplitude. In the reflection coefficient collection, due to environmental noise, network analyzer noise and other electromagnetic interference, the reflection coefficient spectrum composed of the collected reflection coefficient has some noise. Since the positioning curve is directly calculated based on the reflection coefficient spectrum, if the reflection coefficient spectrum has noise, it will directly cause the positioning curve to have errors. In order to eliminate the noise in the reflection coefficient spectrum, the present invention first calculates the upper envelope and the lower envelope of the reflection coefficient spectrum, smoothes the upper envelope and the lower envelope, and then denoises the reflection coefficient spectrum using the curve between the smoothed upper envelope and the lower envelope. Among them, the upper envelope is obtained based on the maximum point in the reflection coefficient spectrum. Specifically, the upper envelope is obtained by curve fitting the maximum point in the reflection coefficient spectrum. Similarly, the lower envelope is obtained based on the minimum point in the reflection coefficient spectrum. Specifically, the lower envelope is obtained by curve fitting the minimum point in the reflection coefficient spectrum. Figure 3 The upper envelope and the lower envelope obtained by curve fitting the maximum and minimum values ​​of the reflection coefficient spectrum are shown. Cable faults include but are not limited to aging, insulation damage or partial discharge.

[0054] In an optional embodiment, the smoothing of the upper envelope and the lower envelope is specifically performed as follows:

[0055] Calculate the average value of the upper envelope and the lower envelope to form the middle curve;

[0056] Take multiple reference points from the middle curve, calculate the distance from each reference point to the upper envelope to form an upper envelope distance set, and calculate the distance from each reference point to the lower envelope to form a lower envelope distance set;

[0057] Gaussian filtering is performed on the upper envelope distance set and the lower envelope distance set respectively, and the upper envelope distance set and the lower envelope distance set after filtering are averaged to obtain a reference set;

[0058] Adjust the positions of the points in the upper and lower envelopes that correspond to the distances in the reference set according to the distances in the reference set.

[0059] Since the reflection coefficient spectrum itself has noise, and the upper envelope and the lower envelope are obtained by fitting, there are also certain errors. In this embodiment, by calculating the point-to-point average value of the upper envelope and the lower envelope, an intermediate curve between the upper and lower envelopes is obtained. On the intermediate curve, a series of reference points are selected, such as reference points evenly distributed, and for each reference point, its vertical distance or the closest distance to the upper envelope and the lower envelope is calculated. Each reference point has a vertical distance or the closest distance on the upper and lower envelopes. According to the arrangement order of the reference points on the intermediate curve, the points corresponding to the reference points on the upper envelope are placed in the upper envelope distance set in the order described. Similarly, the lower envelope distance set can be obtained. Each element in the upper envelope distance set and the lower envelope distance set is a distance, and the number of elements in the upper and lower envelope distance sets is the same as the number of reference points.

[0060] Gaussian filtering is performed on the upper envelope distance set and the lower envelope distance set respectively to obtain two smoother sets. Gaussian filtering is a smoothing technique used to eliminate noise and reduce drastic changes to obtain a more stable distance set. Then, the distances with the same sequence number in the upper envelope distance set and the lower envelope distance set are averaged, for example, the 5th distance in the upper envelope distance set and the 5th distance in the lower envelope distance set are averaged. The smoothed reference distance set is used to adjust the intermediate curve to generate new upper envelope and lower envelope curves respectively. Specifically, each distance in the reference set corresponds to a position in the upper envelope, and the position of the corresponding point in the upper envelope is adjusted according to the distance in the reference set. For example, the 5th distance in the reference set corresponds to the 5th distance in the upper envelope distance set, and the 5th distance in the reference set is used as the 5th distance in the upper envelope distance set. The 5th distance in the upper envelope distance set is adjusted according to the 5th point on the intermediate curve and the 5th distance in the reference set. That is to say, the method of adjusting the positions of points in the upper and lower envelope lines corresponding to the distances in the reference set according to the distances in the reference set is to use the reference set as the upper envelope distance set and the lower envelope distance set, and then recalculate the positions of the points on the upper envelope line according to the reference points on the middle curve and the upper envelope distance set, and recalculate the positions of the points on the lower envelope line according to the reference points on the middle curve and the lower envelope distance set.

[0061] After obtaining the smoothed upper and lower envelopes, in one embodiment, the reflection coefficient spectrum is denoised using the curve between the smoothed upper and lower envelopes, specifically:

[0062] Obtaining the point in the upper envelope corresponding to the maximum value in the reflection coefficient spectrum as the characteristic point of the upper envelope, and obtaining the point in the lower envelope corresponding to the minimum value in the reflection coefficient spectrum as the characteristic point of the lower envelope;

[0063] Calculate the normal vector of the feature point of the upper envelope, and obtain the intersection of the normal vector and the lower envelope, and use the line segment formed by the feature point of the upper envelope and the corresponding intersection as the feature line segment; calculate the normal vector of the feature point of the lower envelope, and obtain the intersection of the normal vector and the upper envelope, and use the line segment formed by the feature point of the lower envelope and the corresponding intersection as the feature line segment;

[0064] Taking a preset number of points at equal intervals on each characteristic line segment, and sorting the preset number of points on each characteristic line segment according to the distance from the upper envelope line;

[0065] Take out the points with the same serial number in each characteristic line segment and perform curve fitting to obtain the curve between the upper and lower envelopes;

[0066] Dividing the reflection coefficient spectrum into a plurality of regions according to the maximum and minimum values, wherein the regions are composed of adjacent maximum and minimum value regions;

[0067] Calculate the number of intersections of each curve between the reflection coefficient spectrum and the upper and lower envelope lines in each region. If the number of intersections is greater than 1, obtain the previous and next curves of the curve with the number of intersections greater than 1, and use the intersections of the previous and next curves with the reflection coefficient spectrum in the region to regenerate the curve between the intersections of the previous and next curves with the reflection coefficient spectrum in the region.

[0068] The upper envelope and lower envelope are obtained based on the maximum and minimum values ​​in the reflection coefficient spectrum. Each maximum value has a corresponding point on the upper envelope, and the point corresponding to this point in the upper envelope is used as a feature point; each minimum value point has a corresponding point in the lower envelope, and the point corresponding to this point in the lower envelope is used as a feature point. For example, the point corresponding to the third maximum value point in the reflection coefficient spectrum in the upper envelope is (0.6, 2), so the point (0.6, 2) is a feature point.

[0069] Then, get the normal vector of the feature point on the upper envelope line. Along the direction of this normal vector, there will be an intersection with the lower envelope. Assuming the intersection is (0.3, 2.2), then the points (0.6, 2) and (0.3, 2.2) constitute the feature line segment, such as Figure 4 shown.

[0070] A preset number of points are taken at equal intervals on the feature line segment, and each feature line segment will take a preset number of points at equal intervals. The points taken on each feature line segment are sorted according to the distance of the envelope. For example, if the preset number is 4, the first line segment will have 4 points, and the second line segment will also have 4 points. Further assume that the points of the first feature line segment after sorting are A1-A4, and the points of the second feature line segment are B1-B4. At the same time, take out the same sequence number, for example, take out A3 and B3 at the same time, and perform curve fitting. In this way, a curve will be obtained, and this curve is between the upper and lower envelopes. If the preset number is 4, 4 curves will be obtained.

[0071] The reflection coefficient spectrum is divided into several regions according to the extreme value points. Each region consists of a maximum value and a minimum value next to each other. The intersection points of each region and the curve between the upper and lower envelopes are calculated. If the number of intersection points is greater than 1, for example, two, the part between the intersection points belonging to the same curve and the same region is deleted from the reflection coefficient spectrum, and the intersection points of other curves adjacent to the curve and the reflection coefficient spectrum are interpolated to regenerate the deleted part. Figure 5 As shown, for example, if curve 3 has three intersections in region 4, the content between the intersections of curve 2, curve 4 and region 4 is deleted, and regenerated by interpolation based on the intersections of curve 2 and region 4, and curve 4 and region 4. If the intersection of the adjacent curve and the reflection coefficient spectrum in the region is still greater than 1, the next adjacent curve of the adjacent curve is found until the intersection of the curve and the reflection coefficient spectrum in the region is found to be 1.

[0072] Among them, using the intersection points of the previous curve and the next curve with the reflection coefficient spectrum in the region refers to the intersection point of the previous curve with the reflection coefficient spectrum in the region, and the intersection point of the next curve with the reflection coefficient spectrum in the region. Regenerating the curve between the intersection points of the previous curve and the next curve with the reflection coefficient spectrum in the region refers to the intersection point of the previous curve with the reflection coefficient spectrum in the region, the intersection point of the next curve with the reflection coefficient spectrum in the region, and the curve between the two intersection points. Figure 6 The comparison of the reflection coefficient spectrum before and after denoising is shown.

[0073] Step 2: obtain multiple partially overlapping intervals from the denoised reflection coefficient spectrum, use multiple different window functions to perform integral transformation on the reflection coefficient spectrum of each interval, take the average value of the integral transformation results of all window functions in the same interval as the fault location curve of the interval, obtain the position of the maximum point of each interval, group the positions according to their proximity, and take the average value of the positions in the same group as the position of the cable fault point.

[0074] The horizontal axis of the reflection coefficient spectrum is frequency. When performing integral transformation, it is not necessary to perform integral transformation on all frequencies. Figure 7 The left side in the middle is the integral transformation of all frequencies. Figure 7 The right side of is the integral transformation of the reflection coefficient spectrum in the range of 0-0.8. It can be seen that the fault positions in the two are basically the same, but the amplitudes are different. In order to more accurately determine the fault position, the denoised reflection coefficient spectrum is divided into multiple partially overlapping areas. Specifically, the frequency range in the reflection coefficient spectrum is obtained, and multiple partially overlapping intervals are obtained within the frequency range. The ratio of the length of each interval to the frequency range is greater than a preset value. Preferably, the start of each interval is 0Hz.

[0075] At the same time, in order to avoid the influence of the window function in the integral transformation, multiple window functions are used for integral transformation in each area, and then the integral transformation results of different window functions in the same interval are averaged as the integral transformation result of this interval, that is, the fault location curve. Each interval will have a fault location curve, and the faults in the fault location curves of all intervals are grouped according to their positions, and the fault positions with a distance less than the threshold are grouped into one group, and the average value of the positions in the same group is used as the location of the cable fault.

[0076] from Figure 7 It can be seen that there will be signal jumps at the end of the cable. In order to prevent this part of the signal from being identified as a fault location, in one embodiment, after obtaining the position of the maximum point of each interval, it also includes: judging whether the position of the maximum point is within a preset range, if so, retaining the maximum point, otherwise, deleting the maximum point. The preset range refers to the position close to the end of the cable. Preferably, the lower limit of the preset position is 90% of the cable length, and the upper limit is the cable length.

[0077] On the other hand, the present invention provides a cable fault point locating system, the system comprising the following modules:

[0078] A denoising module, used for obtaining a reflection coefficient spectrum of the cable, calculating an upper envelope and a lower envelope of the reflection coefficient spectrum, smoothing the upper envelope and the lower envelope, and denoising the reflection coefficient spectrum using a curve between the smoothed upper envelope and the lower envelope;

[0079] The fault location module is used to obtain multiple partially overlapping intervals from the denoised reflection coefficient spectrum, use multiple different window functions to perform integral transformation on the reflection coefficient spectrum of each interval, take the average value of the integral transformation results of all window functions in the same interval as the fault location curve of the interval, obtain the position of the maximum point of each interval, group the positions according to their proximity, and take the average value of the positions in the same group as the position of the cable fault point.

[0080] Optionally, the smoothing of the upper envelope and the lower envelope is specifically performed as follows:

[0081] Calculate the average value of the upper envelope and the lower envelope to form the middle curve;

[0082] Take multiple reference points from the middle curve, calculate the distance from each reference point to the upper envelope to form an upper envelope distance set, and calculate the distance from each reference point to the lower envelope to form a lower envelope distance set;

[0083] Gaussian filtering is performed on the upper envelope distance set and the lower envelope distance set respectively, and the upper envelope distance set and the lower envelope distance set after filtering are averaged to obtain a reference set;

[0084] Adjust the positions of the points in the upper and lower envelopes that correspond to the distances in the reference set according to the distances in the reference set.

[0085] Optionally, the denoising of the reflection coefficient spectrum is performed by using the curve between the smoothed upper envelope and the lower envelope, specifically:

[0086] Obtaining the point in the upper envelope corresponding to the maximum value in the reflection coefficient spectrum as the characteristic point of the upper envelope, and obtaining the point in the lower envelope corresponding to the minimum value in the reflection coefficient spectrum as the characteristic point of the lower envelope;

[0087] Calculate the normal vector of the feature point of the upper envelope, and obtain the intersection of the normal vector and the lower envelope, and use the line segment formed by the feature point of the upper envelope and the corresponding intersection as the feature line segment; calculate the normal vector of the feature point of the lower envelope, and obtain the intersection of the normal vector and the upper envelope, and use the line segment formed by the feature point of the lower envelope and the corresponding intersection as the feature line segment;

[0088] Taking a preset number of points at equal intervals on each characteristic line segment, and sorting the preset number of points on each characteristic line segment according to the distance from the upper envelope line;

[0089] Take out the points with the same serial number in each characteristic line segment and perform curve fitting to obtain the curve between the upper and lower envelopes;

[0090] Dividing the reflection coefficient spectrum into a plurality of regions according to the maximum and minimum values, wherein the regions are composed of adjacent maximum and minimum value regions;

[0091] Calculate the number of intersections of each curve between the reflection coefficient spectrum and the upper and lower envelope lines in each region. If the number of intersections is greater than 1, obtain the previous and next curves of the curve with the number of intersections greater than 1, and use the intersections of the previous and next curves with the reflection coefficient spectrum in the region to regenerate the curve between the intersections of the previous and next curves with the reflection coefficient spectrum in the region.

[0092] Optionally, after obtaining the position of the maximum point of each interval, the method further includes:

[0093] Determine whether the position of the maximum point is within the preset range. If so, keep the maximum point; otherwise, delete the maximum point.

[0094] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or terminal including the element.

[0095] Of course, those skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by instructing related hardware (such as a processor, a controller, etc.) through a computer program, and the program can be stored in a computer-readable storage medium that can be read by a computer, and the program can include the processes of the above-mentioned method embodiments when executed. The computer-readable storage medium can be a memory, a disk, an optical disk, etc.

[0096] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A cable fault point location method, characterized in that: The method comprises the following steps: Acquire a reflection coefficient spectrum of the cable, calculate an upper envelope and a lower envelope of the reflection coefficient spectrum, smooth the upper envelope and the lower envelope, and denoise the reflection coefficient spectrum using a curve between the upper envelope and the lower envelope after the smoothing process; A plurality of partially overlapping intervals are obtained from the denoised reflection coefficient spectrum, and the reflection coefficient spectrum of each interval is integrally transformed using a plurality of different window functions. The average value of the integral transformation results of all window functions in the same interval is used as the fault location curve of the interval, and the position of the maximum point of each interval is obtained. The positions with a distance less than a threshold are grouped into one group, and the average value of the positions in the same group is used as the position of the cable fault point. The method of denoising the reflection coefficient spectrum by using the curve between the smoothed upper envelope and the lower envelope is as follows: Obtaining the point in the upper envelope corresponding to the maximum value in the reflection coefficient spectrum as the characteristic point of the upper envelope, and obtaining the point in the lower envelope corresponding to the minimum value in the reflection coefficient spectrum as the characteristic point of the lower envelope; Calculate the normal vector of the feature point of the upper envelope, and obtain the intersection of the normal vector and the lower envelope, and use the line segment formed by the feature point of the upper envelope and the corresponding intersection as the feature line segment; calculate the normal vector of the feature point of the lower envelope, and obtain the intersection of the normal vector and the upper envelope, and use the line segment formed by the feature point of the lower envelope and the corresponding intersection as the feature line segment; Taking a preset number of points at equal intervals on each characteristic line segment, and sorting the preset number of points on each characteristic line segment according to the distance from the upper envelope line; Take out the points with the same serial number in each characteristic line segment and perform curve fitting to obtain the curve between the upper and lower envelopes; Dividing the reflection coefficient spectrum into a plurality of regions according to the maximum and minimum values, wherein the regions are composed of adjacent maximum and minimum value regions; Calculate the number of intersections of each curve between the reflection coefficient spectrum and the upper and lower envelope lines in each region. If the number of intersections is greater than 1, obtain the previous and next curves of the curve with the number of intersections greater than 1, and use the intersections of the previous and next curves with the reflection coefficient spectrum in the region to regenerate the curve between the intersections of the previous and next curves with the reflection coefficient spectrum in the region.

2. The method according to claim 1, characterized in that The smoothing process of the upper envelope and the lower envelope is specifically as follows: Calculate the average value of the upper envelope and the lower envelope to form the middle curve; Take multiple reference points from the middle curve, calculate the distance from each reference point to the upper envelope to form an upper envelope distance set, and calculate the distance from each reference point to the lower envelope to form a lower envelope distance set; Gaussian filtering is performed on the upper envelope distance set and the lower envelope distance set respectively, and the upper envelope distance set and the lower envelope distance set after filtering are averaged to obtain a reference set; Adjust the positions of the points in the upper and lower envelopes that correspond to the distances in the reference set according to the distances in the reference set.

3. The method according to claim 1, characterized in that The method of obtaining a plurality of partially overlapping intervals from the denoised reflection coefficient spectrum is specifically as follows: A frequency range in the reflection coefficient spectrum is obtained, and a plurality of partially overlapping intervals are obtained within the frequency range, wherein a ratio of a length of each interval to the frequency range is greater than a preset value.

4. The method according to claim 1, characterized in that After obtaining the position of the maximum point of each interval, the method further includes: Determine whether the position of the maximum point is within the preset range. If so, keep the maximum point; otherwise, delete the maximum point.

5. A cable fault point locating system, characterized in that: The system includes the following modules: A denoising module, used for obtaining a reflection coefficient spectrum of the cable, calculating an upper envelope and a lower envelope of the reflection coefficient spectrum, smoothing the upper envelope and the lower envelope, and denoising the reflection coefficient spectrum using a curve between the smoothed upper envelope and the lower envelope; A fault location module is used to obtain multiple partially overlapping intervals from the denoised reflection coefficient spectrum, perform integral transformation on the reflection coefficient spectrum of each interval using multiple different window functions, take the average value of the integral transformation results of all window functions in the same interval as the fault location curve of the interval, obtain the position of the maximum point of each interval, group the positions with a distance less than a threshold into one group, and take the average value of the positions in the same group as the position of the cable fault point; The method of denoising the reflection coefficient spectrum by using the curve between the smoothed upper envelope and the lower envelope is as follows: Obtaining the point in the upper envelope corresponding to the maximum value in the reflection coefficient spectrum as the characteristic point of the upper envelope, and obtaining the point in the lower envelope corresponding to the minimum value in the reflection coefficient spectrum as the characteristic point of the lower envelope; Calculate the normal vector of the feature point of the upper envelope, and obtain the intersection point of the normal vector and the lower envelope, and use the line segment formed by the feature point of the upper envelope and the corresponding intersection point as the feature line segment; Calculate the normal vector of the feature point of the lower envelope, and obtain the intersection point of the normal vector and the upper envelope, and use the line segment formed by the feature point of the lower envelope and the corresponding intersection point as the feature line segment; Taking a preset number of points at equal intervals on each characteristic line segment, and sorting the preset number of points on each characteristic line segment according to the distance from the upper envelope line; Take out the points with the same serial number in each characteristic line segment and perform curve fitting to obtain the curve between the upper and lower envelopes; Dividing the reflection coefficient spectrum into a plurality of regions according to the maximum and minimum values, wherein the regions are composed of adjacent maximum and minimum value regions; Calculate the number of intersections of each curve between the reflection coefficient spectrum and the upper and lower envelope lines in each region. If the number of intersections is greater than 1, obtain the previous and next curves of the curve with the number of intersections greater than 1, and use the intersections of the previous and next curves with the reflection coefficient spectrum in the region to regenerate the curve between the intersections of the previous and next curves with the reflection coefficient spectrum in the region.

6. The system according to claim 5, characterized in that The smoothing process of the upper envelope and the lower envelope is specifically as follows: Calculate the average value of the upper envelope and the lower envelope to form the middle curve; Take multiple reference points from the middle curve, calculate the distance from each reference point to the upper envelope to form an upper envelope distance set, and calculate the distance from each reference point to the lower envelope to form a lower envelope distance set; Gaussian filtering is performed on the upper envelope distance set and the lower envelope distance set respectively, and the upper envelope distance set and the lower envelope distance set after filtering are averaged to obtain a reference set; Adjust the positions of the points in the upper and lower envelopes that correspond to the distances in the reference set according to the distances in the reference set.

7. The system according to claim 5, characterized in that The method of obtaining a plurality of partially overlapping intervals from the denoised reflection coefficient spectrum is specifically as follows: A frequency range in the reflection coefficient spectrum is obtained, and a plurality of partially overlapping intervals are obtained within the frequency range, wherein a ratio of a length of each interval to the frequency range is greater than a preset value.

8. The system according to claim 5, characterized in that After obtaining the position of the maximum point of each interval, the method further includes: Determine whether the position of the maximum point is within the preset range. If so, keep the maximum point; otherwise, delete the maximum point.

Images