Cable fault positioning technology based on broadband impedance spectrum

Abstract

The invention discloses a cable fault positioning technology based on a broadband impedance spectrum, and relates to the technical field of cable diagnosis, and the technology comprises the following steps: S1, selecting a proper signal injection point and a proper measurement point according to the actual condition of a cable, injecting a broadband signal at one end of the cable by using a signal generation module according to a set frequency range, the frequency range of the signal is fmin to fmax; s2, measuring voltage and current signals at the same end of the injected signal or the other end of the cable, calculating the actual broadband impedance of the cable according to the measured voltage and current signals, and obtaining a broadband impedance spectrum of the actual impedance changing along with the frequency; and S3, analyzing the broadband impedance spectrum. According to the invention, the electrical characteristics of the cable at different frequencies can be comprehensively obtained by using the broadband impedance spectrum, and compared with the traditional single-frequency or narrow-band positioning technology, the fault characteristics can be identified more accurately, so that the accuracy of fault positioning is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of cable diagnosis, and in particular to a cable fault location technology based on broadband impedance spectrum. Background Art

[0002] With the widespread use of power cables in power transmission systems, timely and accurate detection and positioning of cable faults have become crucial. Cable faults not only lead to power supply interruptions, affecting industrial production and residents' lives, but may also cause safety accidents.

[0003] Traditional cable fault location methods, such as the bridge method and pulse reflection method, have certain limitations. The bridge method requires measurements at both ends of the cable and has high requirements for cable symmetry, which limits its application in actual complex cable networks. Although the pulse reflection method can detect fault points in the cable, for some high-resistance faults or flashover faults, its reflected signal is weak, making it difficult to accurately determine the fault location.

[0004] In recent years, fault location methods based on impedance analysis have gradually attracted attention. However, most existing impedance-based methods use single-frequency or narrow-band signals for measurement, which cannot fully reflect the complex characteristics of cables, resulting in low fault location accuracy.

[0005] Therefore, it is necessary to invent a cable fault location technology based on broadband impedance spectrum to solve the above problems. Summary of the Invention

[0006] The object of the present invention is to provide a cable fault location technology based on broadband impedance spectrum to solve the problems raised in the above background technology.

[0007] To achieve the above object, the present invention provides the following technical solution: a cable fault location technology based on broadband impedance spectrum, comprising the following steps: S1: Select appropriate signal injection and measurement points based on the actual cable conditions. Use the signal generator module to inject a broadband signal at one end of the cable within the set frequency range. The signal frequency range is from fmin to fmax. S2: Measure the voltage and current signals at the same end as the signal injection or at the other end of the cable. Calculate the actual broadband impedance of the cable based on the measured voltage and current signals, and obtain a broadband impedance spectrum showing how the actual impedance changes with frequency. S3: Analyze the broadband impedance spectrum, use signal processing algorithms to extract characteristic parameters related to cable faults, and establish a broadband impedance model of the cable based on the structural and material parameters of the cable; S4: Compare the broadband impedance obtained from actual measurement with the broadband impedance obtained through model calculation, calculate the difference between the two, analyze the abnormal points and characteristic frequency bands in the difference, and determine the fault type and fault location based on the pre-established fault feature database.

[0008] Preferably, in S1, the fmin is the lowest frequency, the fmax is the highest frequency, and fmin < fmax. The frequency range fmin and fmax of the broadband can be adjusted according to the length and type of the cable.

[0009] Preferably, in S2, the calculation method of the actual broadband impedance of the cable is:

[0010] where U(f) is the voltage and I(f) is the current.

[0011] Preferably, in S3, the broadband impedance calculation model of the cable is:

[0012] where Z(f) is the impedance of the cable at the frequency, R(f) is the resistance, L(f) is the inductance, and C(f) is the capacitance. .

[0013] Preferably, in S4, the difference is the broadband impedance obtained from actual measurement - the broadband impedance obtained through model calculation, and the calculation method is:

[0014] where Zm(f) is the broadband impedance obtained from actual measurement and Z(f) is the broadband impedance obtained through model calculation.

[0015] Preferably, in S2, signal processing techniques such as Fourier transform, wavelet transform, etc. are used to preprocess the broadband impedance spectrum.

[0016] Preferably, in S3, the characteristic parameters include the peak and valley values of the impedance amplitude in the broadband impedance spectrum and their corresponding frequencies, the mutation points of the impedance phase and their corresponding frequencies, and the regions with relatively large slope change rates in the broadband impedance spectrum and their corresponding frequency ranges.

[0017] Technical effects and advantages of the present invention: The present invention utilizes the broadband impedance spectrum to comprehensively obtain the electrical characteristics of the cable at different frequencies. Compared with traditional single-frequency or narrow-band positioning techniques, it can more accurately identify fault characteristics, thereby improving the accuracy of fault location. Brief Description of the Drawings

[0018] Figure 1 It is a schematic flow diagram of the present invention. Detailed Embodiments

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0020] The present invention provides a cable fault location technology based on broadband impedance spectrum as shown in Figure 1 and includes the following steps: S1: According to the actual situation of the cable, select appropriate signal injection points and measurement points, and use the signal generation module to inject a broadband signal at one end of the cable within the set frequency range. The frequency range of the signal is from fmin to fmax; S2: Measure the voltage and current signals at the same end where the signal is injected or at the other end of the cable. According to the measured voltage and current signals, calculate the actual broadband impedance of the cable to obtain a broadband impedance spectrum showing the change of the actual impedance with frequency; S3: Analyze the broadband impedance spectrum, use signal processing algorithms to extract characteristic parameters related to cable faults, and establish a cable broadband impedance model based on the structural parameters and material parameters of the cable; S4: Compare the actually measured broadband impedance with the broadband impedance calculated by the model, calculate the difference between the two, analyze the abnormal points and characteristic frequency bands in the difference, and determine the fault type and fault location according to the pre-established fault feature database.

[0021] In S1, fmin is the lowest frequency, fmax is the highest frequency, and fmin < fmax. The frequency range fmin and fmax of the broadband can be adjusted according to the length and type of the cable.

[0022] In S2, the calculation method of the actual broadband impedance of the cable is:

[0023] where U(f) is the voltage and I(f) is the current.

[0024] In S3, the cable broadband impedance calculation model is:

[0025] where Z(f) is the impedance of the cable at the frequency, R(f) is the resistance, L(f) is the inductance, and C(f) is the capacitance. .

[0026] In S4, the difference is the actually measured broadband impedance - the broadband impedance calculated by the model, and the calculation method is:

[0027] Where Zm(f) is the broadband impedance obtained by actual measurement, and Z(f) is the broadband impedance obtained by model calculation.

[0028] In S2, signal processing techniques, such as Fourier transform and wavelet transform, are used to pre-process the broadband impedance spectrum.

[0029] In S3, the characteristic parameters include the impedance amplitude peak value, valley value and corresponding frequency in the broadband impedance spectrum, the impedance phase mutation point and corresponding frequency, the area with a larger slope change rate in the broadband impedance spectrum and its corresponding frequency range.

[0030] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A cable fault location technology based on broadband impedance spectroscopy, characterized by: It includes the following steps: S1: According to the actual situation of the cable, select appropriate signal injection points and measurement points. In accordance with the set frequency range, use the signal generation module to inject a broadband signal at one end of the cable, and the frequency range of the signal is from fmin to fmax; S2: Measure the voltage and current signals at the same end where the signal is injected or at the other end of the cable. According to the measured voltage and current signals, calculate the actual broadband impedance of the cable, and obtain a broadband impedance spectrum showing the variation of the actual impedance with frequency; S3: Analyze the broadband impedance spectrum, use signal processing algorithms to extract the characteristic parameters related to cable faults, and establish a broadband impedance model of the cable based on the structural parameters and material parameters of the cable; S4: Compare the broadband impedance obtained from actual measurement with the broadband impedance calculated through the model, calculate the difference between the two, analyze the abnormal points and characteristic frequency bands in the difference, and determine the fault type and fault location according to the pre-established fault characteristic database.

2. The cable fault location technology based on broadband impedance spectroscopy according to claim 1, characterized in that: In S1, fmin is the lowest frequency, fmax is the highest frequency, and fmin < fmax. The frequency range fmin and fmax of the broadband can be adjusted according to the length and type of the cable.

3. The cable fault location technology based on broadband impedance spectroscopy according to claim 1, characterized in that: In S2, the calculation method of the actual broadband impedance of the cable is as follows: Where U(f) is voltage and I(f) is current.

4. The cable fault location technology based on broadband impedance spectroscopy according to claim 1, characterized in that: In S3, the cable broadband impedance calculation model is: Where Z(f) is the impedance of the cable at the frequency, R(f) is the resistance, L(f) is the inductance, and C(f) is the capacitance. .

5. The cable fault location technology based on broadband impedance spectroscopy according to claim 1, characterized in that: In S4, the difference is the broadband impedance obtained by actual measurement minus the broadband impedance calculated by the model, which is calculated as follows: Where Zm(f) is the broadband impedance obtained by actual measurement, and Z(f) is the broadband impedance obtained by model calculation.

6. The cable fault location technology based on broadband impedance spectroscopy according to claim 1, characterized in that: In S2, signal processing techniques such as Fourier transform, wavelet transform, etc. are used to preprocess the broadband impedance spectrum.

7. The cable fault location technology based on broadband impedance spectroscopy according to claim 1, characterized in that: In S3, the characteristic parameters include the peak and valley values of the impedance amplitude in the broadband impedance spectrum and their corresponding frequencies, the mutation points of the impedance phase and their corresponding frequencies, and the regions with relatively large slope change rates in the broadband impedance spectrum and their corresponding frequency ranges.

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