CN117630561A - Cable ageing defect nondestructive positioning method based on transmission line model - Google Patents
Cable ageing defect nondestructive positioning method based on transmission line model Download PDFInfo
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- CN117630561A CN117630561A CN202311360556.7A CN202311360556A CN117630561A CN 117630561 A CN117630561 A CN 117630561A CN 202311360556 A CN202311360556 A CN 202311360556A CN 117630561 A CN117630561 A CN 117630561A
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- 230000007547 defect Effects 0.000 title claims abstract description 40
- 230000032683 aging Effects 0.000 title claims abstract description 19
- 238000000034 method Methods 0.000 title claims abstract description 19
- 230000005540 biological transmission Effects 0.000 title claims abstract description 9
- 238000001453 impedance spectrum Methods 0.000 claims abstract description 5
- 238000003745 diagnosis Methods 0.000 claims abstract description 4
- 238000001914 filtration Methods 0.000 claims abstract description 4
- 238000012545 processing Methods 0.000 claims description 6
- 238000001228 spectrum Methods 0.000 claims description 6
- 238000010586 diagram Methods 0.000 claims description 4
- 238000012935 Averaging Methods 0.000 claims description 3
- 230000008569 process Effects 0.000 claims description 3
- 230000035945 sensitivity Effects 0.000 claims description 3
- 238000001514 detection method Methods 0.000 abstract description 19
- 230000002950 deficient Effects 0.000 abstract description 4
- 230000001066 destructive effect Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 230000002159 abnormal effect Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
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Abstract
The invention relates to the technical field of cable defect detection, and discloses a nondestructive positioning method for cable ageing defects based on a transmission line model, which comprises the following steps: measuring by using professional equipment to obtain impedance spectrum data of the head end of the cable; establishing a cable head end impedance spectrum model containing a defect section; constructing a line characteristic diagnosis function; drawing a positioning waveform through a functional relation; filtering and denoising the positioning waveform; and combining the analysis graph to judge and position the local defect. The method can better detect the actual state of the cable during operation without damaging the cable, detect whether the cable is internally defective and aged at early stage, and realize defect, aging and fault positioning. Compared with the existing detection method, the method can finish detection without damaging the cable, has better voltage class compatibility, and can realize defect point, aging point and fault point positioning.
Description
Technical Field
The invention relates to the technical field of cable ageing defect positioning, in particular to a nondestructive positioning method for cable ageing defects based on a transmission line model.
Background
With the continuous advancement of industrialization and the wide application of electric power equipment, cables have become one of the indispensable important equipment in the modern society as an important component of electric power transmission. The power cable is one of important pillar industries supporting national economy, and annual output value exceeds trillion primordial. Due to the influence of factors such as cable damage, aging of the cable and the like caused by the complexity of a cable laying environment, the occurrence frequency of cable faults is high, and faults such as short circuit and the like of a power system can be possibly caused. And then causes accidents such as fire disaster, large-scale power failure and the like, seriously influences the stable operation of a power system, and brings inconvenience and loss to the life of residents. Cable faults often evolve from early defects, and if the defects are placed regardless of the evolution of the faults into various irreversible faults, the cable defects are detected and positioned in advance, and accurate information of abnormal cable operation conditions is known as early as possible, so that the cable faults have important significance for electricity safety.
Early defects and aging of the cable are not easy to be directly found through a destructive detection method, the destructive detection method can accelerate the aging of fragile parts, and in addition, the positions of the defects and local aging are difficult to accurately position.
Disclosure of Invention
The invention aims to provide a nondestructive positioning method for cable ageing defects based on a transmission line model, which can better detect the actual state of a cable in operation under the condition of not damaging the cable, detect whether the cable is internally defective and aged at an early stage, and can realize defect, ageing and fault positioning. Compared with the existing detection method, the method can finish detection without damaging the cable, has better voltage class compatibility, and can realize defect point, aging point and fault point positioning.
The application provides a nondestructive positioning method for cable ageing defects based on a transmission line model, which is characterized by comprising the following steps of:
measuring the input impedance amplitude and the phase frequency spectrum Z (f) of the head end of the cable by using a vector network analyzer;
assuming that the position of the head end of the cable is the origin of coordinates, the positive direction is the direction from the head end to the tail end, the length of the cable is l, and the coordinates of each position along the length of the cable are x, then the impedance value of the cable is Z x The characteristic impedance of the cable is Z 0 The propagation coefficient is gamma, the head end of the cable containing the defective section (the reflection coefficient at the head end position is ρ L ) The impedance spectrum model of (2) is:
due to Z l Can be measured by a vector network analyzer, thus the ρ can be obtained L A curve changing along with the frequency, namely a reflection coefficient spectrum of the head end of the cable;
the reflection coefficient of the cable defect is greatly different from that of the intact section, the reflection coefficient is unfolded by using the Euler formula, and the trigonometric function part of the real part of the reflection coefficient is considered:
after the analysis and the processing, a cable line diagnosis function F (x) can be constructed;
carrying out refinement treatment by using DFT to obtain local refinement information in a positioning curve;
high frequency sidelobe interference in the waveform diagram is suppressed by using Kaiser window function filtering:
wherein: i 0 Is a zero-order Bessel function of the first class, and beta is a performance parameter;
the spatial resolution of the positioning curve is improved by using distance window processing, the recognition sensitivity of local defects is improved, and the distance window function is as follows:
wherein: d (D) 0 Is the original data; s is the adjustable distance window length; j is the number of data points in the distance window; f (F) mean Representing an averaging process;
and (3) researching and judging the processed image, if a peak appears in the image, indicating that the cable has a local defect, and the position where the peak is located is the position where the defect is located.
Compared with the existing cable running state detection algorithm, the method has the main advantages that:
1. nondestructive detection can be realized, the cable is not damaged during the test, and the service life of the cable is not influenced;
2. the voltage range is compatible, so that the method is applicable to voltages of all levels, and equipment is not required to be reconfigured according to voltage grades;
3. the cable fault detection device can realize the detection in advance, and the detection is carried out on the weak points of the insulation and the defect points instead of the fault after the fault of the cable.
Drawings
FIG. 1 is a schematic illustration of the effect of non-destructive localization of aging defects for cable samples A and B according to the present invention;
fig. 2 is a schematic diagram showing the effect of performing nondestructive positioning of an aging defect on a cable sample C and a cable sample D according to the present invention.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative only and are not to be construed as limiting the invention.
In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present invention.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present invention, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
In the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
In the present invention, unless expressly stated or limited otherwise, a first feature "up" or "down" a second feature may be the first and second features in direct contact, or the first and second features in indirect contact via an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.
The implementation of the present invention will be described in detail below with reference to specific embodiments.
1-2, a nondestructive positioning method for cable ageing defect based on a transmission line model is characterized by comprising the following steps:
measuring the input impedance amplitude and the phase frequency spectrum Z (f) of the head end of the cable by using a vector network analyzer;
assuming that the position of the head end of the cable is the origin of coordinates, the positive direction is the direction from the head end to the tail end, the length of the cable is l, and the coordinates of each position along the length of the cable are x, then the impedance value of the cable is Z x The characteristic impedance of the cable is Z 0 The propagation coefficient is gamma, the head end of the cable containing the defective section (the reflection coefficient at the head end position is ρ L ) The impedance spectrum model of (2) is:
due to Z l Can be measured by a vector network analyzer, thus the ρ can be obtained L A curve changing along with the frequency, namely a reflection coefficient spectrum of the head end of the cable;
the reflection coefficient of the cable defect is greatly different from that of the intact section, the reflection coefficient is unfolded by using the Euler formula, and the trigonometric function part of the real part of the reflection coefficient is considered:
after the analysis and the processing, a cable line diagnosis function F (x) can be constructed;
carrying out refinement treatment by using DFT to obtain local refinement information in a positioning curve;
high frequency sidelobe interference in the waveform diagram is suppressed by using Kaiser window function filtering:
wherein: i 0 Is a zero-order Bessel function of the first class, and beta is a performance parameter;
the spatial resolution of the positioning curve is improved by using distance window processing, the recognition sensitivity of local defects is improved, and the distance window function is as follows:
wherein: d (D) 0 Is the original data; s is the adjustable distance window length; j is the number of data points in the distance window; f (F) mean Representing an averaging process;
and (3) researching and judging the processed image, if a peak appears in the image, indicating that the cable has a local defect, and the position where the peak is located is the position where the defect is located.
Compared with the existing cable running state detection algorithm, the method has the main advantages that:
1. nondestructive detection can be realized, the cable is not damaged during the test, and the service life of the cable is not influenced;
2. the voltage range is compatible, so that the method is applicable to voltages of all levels, and equipment is not required to be reconfigured according to voltage grades;
3. the cable fault detection device can realize the detection in advance, and the detection is carried out on the weak points of the insulation and the defect points instead of the fault after the fault of the cable.
Fig. 1 and fig. 2 are experimental results of cable defect detection by the method of the present application, and as can be seen from fig. 1 and fig. 2, peak positions are obviously observed in waveform graphs, so that feasibility of the cable defect detection is verified, and cable defects can be effectively detected and located.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
While embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the invention.
Claims (1)
1. The nondestructive positioning method for the cable ageing defect based on the transmission line model is characterized by comprising the following steps of:
measuring the input impedance amplitude and the phase frequency spectrum Z (f) of the head end of the cable by using a vector network analyzer;
assuming that the position of the head end of the cable is the origin of coordinates, the positive direction is the direction from the head end to the tail end, the length of the cable is l, and the coordinates of each position along the length of the cable are x, then the impedance value of the cable is Z x The characteristic impedance of the cable is Z 0 The propagation coefficient is gamma, the cable head-end (head-end)The reflection coefficient of the position is ρ L ) The impedance spectrum model of (2) is:
due to Z l Can be measured by a vector network analyzer, thus the ρ can be obtained L A curve changing along with the frequency, namely a reflection coefficient spectrum of the head end of the cable;
the reflection coefficient of the cable defect is greatly different from that of the intact section, the reflection coefficient is unfolded by using the Euler formula, and the trigonometric function part of the real part of the reflection coefficient is considered:
after the analysis and the processing, a cable line diagnosis function F (x) can be constructed;
carrying out refinement treatment by using DFT to obtain local refinement information in a positioning curve;
high frequency sidelobe interference in the waveform diagram is suppressed by using Kaiser window function filtering:
wherein: i 0 Is a zero-order Bessel function of the first class, and beta is a performance parameter;
the spatial resolution of the positioning curve is improved by using distance window processing, the recognition sensitivity of local defects is improved, and the distance window function is as follows:
wherein: d (D) 0 Is the original data; s is the adjustable distance window length; j is the number of data points in the distance window; f (F) mean Representing an averaging process;
and (3) researching and judging the processed image, if a peak appears in the image, indicating that the cable has a local defect, and the position where the peak is located is the position where the defect is located.
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| CN202311360556.7A CN117630561A (en) | 2023-10-20 | 2023-10-20 | Cable ageing defect nondestructive positioning method based on transmission line model |
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| CN202311360556.7A CN117630561A (en) | 2023-10-20 | 2023-10-20 | Cable ageing defect nondestructive positioning method based on transmission line model |
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