Method and system for on-line monitoring of high-voltage cable harmonic signal abnormity

Abstract

The invention discloses a method and a system for online monitoring harmonic signal abnormity of a high-voltage cable. The method comprises the following steps: respectively arranging harmonic sensors in grounding wire preset areas at two ends of a tested high-voltage cable; a harmonic signal output by the harmonic sensor is collected through a signal collection module based on a sampling interval, and the harmonic signal is transmitted to a data analysis processing module through a data transmission module; performing windowed Fourier analysis on the harmonic signal through the data analysis processing module to obtain harmonic current data in the harmonic signal; calculating a key quantitative index of the harmonic signal based on the harmonic current data; and analyzing the harmonic abnormal degree of the tested high-voltage cable based on the key quantitative index, and evaluating the deterioration degree of the tested high-voltage cable based on an analysis result. According to the invention, through on-line measurement, the harmonic signal detection result is analyzed in real time according to the on-site actual situation.

Description

Technical Field

[0001] This invention relates to the field of condition monitoring and aging assessment technology, and more specifically, to a method and system for online monitoring of abnormal harmonic signals in high-voltage cables. Background Technology

[0002] In recent years, with the rapid development of online monitoring technology for high-voltage cable lines, a comprehensive and visualized monitoring system has been gradually established, covering partial discharge of the cable body, temperature monitoring, grounding current detection, early warning of external force damage to the channel, and environmental parameter monitoring. However, existing monitoring technologies still have significant technical blind spots in areas such as cable conductor defect identification, insulation condition assessment, and grounding system anomaly detection. Specifically, these include: ① insufficient sensitivity in identifying latent defects; ② low accuracy in early warning under operating conditions; and ③ a lack of dynamic monitoring capabilities for insulation degradation under broadband disturbance environments. Especially under the operating conditions of new power systems, high-voltage cables are subjected to broadband electromagnetic disturbances for extended periods, leading to a significant increase in the risk of accelerated aging of insulation materials. This places higher demands on the technology for sensing potential risks in cable lines.

[0003] Existing research confirms a significant correlation between abnormal characteristics of cable harmonic signals and insulation degradation processes and potential defects. However, current research primarily focuses on the theoretical analysis of harmonic component anomalies, and a practical online monitoring system solution for high-voltage cable harmonic signals has not yet been established, thus limiting the practical application of this technology.

[0004] Therefore, a technology is needed to enable online monitoring of harmonic signal anomalies in high-voltage cables. Summary of the Invention

[0005] The present invention provides a method and system for online monitoring of abnormal harmonic signals in high-voltage cables, thereby solving the problem of how to monitor abnormal harmonic signals in high-voltage cables online.

[0006] To address the aforementioned problems, this invention provides a method for online monitoring of abnormal harmonic signals in high-voltage cables, the method comprising:

[0007] Harmonic sensors are installed in the preset area of ​​the grounding wire at both ends of the high-voltage cable under test;

[0008] The harmonic signal output by the harmonic sensor is acquired by the signal acquisition module based on the sampling interval, and the harmonic signal is transmitted to the data analysis and processing module via the data transmission module.

[0009] The harmonic signal is subjected to windowed Fourier analysis by the data analysis and processing module to obtain the harmonic current data in the harmonic signal;

[0010] Calculate the key quantitative indicators of the harmonic signal based on the harmonic current data.

[0011] The degree of harmonic anomaly of the tested high-voltage cable is analyzed based on the key quantitative indicators, and the degree of degradation of the tested high-voltage cable is evaluated based on the analysis results.

[0012] Preferably, the step of performing windowed Fourier analysis on the harmonic signal through the data analysis and processing module to obtain harmonic current data in the harmonic signal includes:

[0013] The window function-based sample of the Hanning window is:

[0014]

[0015] i ω (n) = i(n)·ω(n)

[0016] Where ω(n) is the window function value of the Hanning window function at the nth discrete point, and i(n) is the instantaneous value of the original current signal at the nth discrete sampling point. ω (n) is the current signal value of the nth discrete sampling point after Hanning window weighting, where N is the upper limit of the harmonic order and n refers to the nth harmonic.

[0017] The spectrum of the measured harmonic signal sample after windowed Fourier analysis is as follows:

[0018]

[0019] Where I(k) is the spectral amplitude (or spectral coefficient) at the corresponding frequency point k after windowed Fourier analysis, j is the imaginary unit, and k is the frequency index.

[0020] Preferably, the key quantitative indicator includes the effective value of the harmonic current I. RMS The effective value of the harmonic current I RMS The calculation formula is:

[0021]

[0022] Where I1, I2, ..., I n , which are the effective current values ​​of the fundamental wave and the 2nd to nth harmonics in the harmonic signal, respectively.

[0023] Preferably, the key quantitative indicator includes total harmonic distortion (THD). I The total harmonic distortion (THD) I The calculation formula is:

[0024]

[0025] Wherein, N is the upper limit of the harmonic order in the harmonic signal.

[0026] Preferably, the key quantitative indicator includes the nth harmonic content K of the defective cable. n The nth harmonic content K of the defective cable n The calculation formula is:

[0027]

[0028] Preferably, the key quantitative indicator includes the relative harmonic content R. n The relative harmonic content R n The calculation formula is:

[0029]

[0030] Among them, K n * The nth harmonic content of a defect-free cable.

[0031] Based on another aspect of the present invention, the present invention provides a system for online monitoring of abnormal harmonic signals in high-voltage cables, the system comprising:

[0032] The setting unit is used to set harmonic sensors in the preset area of ​​the grounding wire at both ends of the high-voltage cable under test.

[0033] The acquisition unit is used to acquire the harmonic signal output by the harmonic sensor based on the sampling interval through the signal acquisition module, and the harmonic signal is transmitted to the data analysis and processing module via the data transmission module.

[0034] The analysis unit is used to perform windowed Fourier analysis on the harmonic signal through the data analysis and processing module to obtain harmonic current data in the harmonic signal;

[0035] The calculation unit is used to calculate the key quantitative indicators of the harmonic signal based on the harmonic current data;

[0036] The results unit is used to analyze the degree of harmonic anomaly of the tested high-voltage cable based on the key quantitative indicators, and to evaluate the degree of degradation of the tested high-voltage cable based on the analysis results.

[0037] Preferably, the analysis unit is configured to perform windowed Fourier analysis on the harmonic signal through the data analysis and processing module to obtain harmonic current data in the harmonic signal, and is further configured to:

[0038] The window function-based sample of the Hanning window is:

[0039]

[0040] iω (n) = i(n)·ω(n)

[0041] Where ω(n) is the window function value of the Hanning window function at the nth discrete point, and i(n) is the instantaneous value of the original current signal at the nth discrete sampling point. ω (n) is the current signal value of the nth discrete sampling point after Hanning window weighting, where N is the upper limit of the harmonic order and n refers to the nth harmonic.

[0042] The spectrum of the measured harmonic signal sample after windowed Fourier analysis is as follows:

[0043]

[0044] Where I(k) is the spectral amplitude (or spectral coefficient) at the corresponding frequency point k after windowed Fourier analysis, j is the imaginary unit, and k is the frequency index.

[0045] Preferably, the key quantitative indicator includes the effective value of the harmonic current I. RMS The effective value of the harmonic current I RMS The calculation formula is:

[0046]

[0047] Where I1, I2, ..., I n , which are the effective current values ​​of the fundamental wave and the 2nd to nth harmonics in the harmonic signal, respectively.

[0048] Preferably, the key quantitative indicator includes total harmonic distortion (THD). I The total harmonic distortion (THD) I The calculation formula is:

[0049]

[0050] Wherein, N is the upper limit of the harmonic order in the harmonic signal.

[0051] Preferably, the key quantitative indicator includes the nth harmonic content K of the defective cable. n The nth harmonic content K of the defective cable n The calculation formula is:

[0052]

[0053] Preferably, the key quantitative indicator includes the relative harmonic content R. n The relative harmonic content R n The calculation formula is:

[0054]

[0055] Among them, K n * The nth harmonic content of a defect-free cable.

[0056] This invention provides a method and system for online monitoring of harmonic signal anomalies in high-voltage cables. The method includes: setting harmonic sensors within a preset area on the grounding wires at both ends of the high-voltage cable under test; acquiring harmonic signals output by the sensors based on sampling intervals using a signal acquisition module; transmitting the harmonic signals to a data analysis and processing module via a data transmission module; performing windowed Fourier analysis on the harmonic signals using the data analysis and processing module to obtain harmonic current data; calculating key quantitative indicators of the harmonic signals based on the harmonic current data; analyzing the degree of harmonic anomaly in the high-voltage cable under test based on the key quantitative indicators; and assessing the degree of degradation of the high-voltage cable under test based on the analysis results. This invention provides a method and system for online monitoring of harmonic signal anomalies in high-voltage cables, enabling online measurement without power outages and offering ease of use. The technical means employed in this invention are convenient, allowing for real-time analysis of harmonic signal detection results based on actual on-site conditions. Attached Figure Description

[0057] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0058] Figure 1 This is a flowchart of a method for online monitoring of harmonic signal anomalies in high-voltage cables according to a preferred embodiment of the present invention.

[0059] Figure 2 This is a schematic diagram of high-voltage cable harmonic signal measurement according to a preferred embodiment of the present invention;

[0060] Figure 3 This is a schematic cross-sectional view of a non-contact harmonic signal sensor according to a preferred embodiment of the present invention;

[0061] Figure 4 This is a schematic diagram of the metal sheath and harmonic sensor coil according to a preferred embodiment of the present invention;

[0062] Figure 5 This is a schematic diagram of an integral correction circuit according to a preferred embodiment of the present invention;

[0063] Figure 6 This is a schematic diagram of an online monitoring device according to a preferred embodiment of the present invention;

[0064] Figure 7 This is a schematic diagram of the harmonic signal detection results of a high-voltage cable according to a preferred embodiment of the present invention;

[0065] Figure 8 This is a schematic diagram of the harmonic signal analysis and processing results of a high-voltage cable according to a preferred embodiment of the present invention; and

[0066] Figure 9 This is a system structure diagram for online monitoring of harmonic signal anomalies in high-voltage cables according to a preferred embodiment of the present invention. Detailed Implementation

[0067] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0068] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0069] Figure 1 This is a flowchart of a method for online monitoring of harmonic signal anomalies in high-voltage cables according to a preferred embodiment of the present invention.

[0070] The present invention aims to achieve online monitoring of abnormal harmonic signals in high-voltage cable lines by using non-contact harmonic current sensors at both ends of the grounding wire of the high-voltage cable to collect the amplitude-frequency characteristics of harmonic signals in the metal sheath of the high-voltage cable under test.

[0071] like Figure 1 As shown, this invention provides a method for online monitoring of abnormal harmonic signals in high-voltage cables, the method comprising:

[0072] Step 101: Set up harmonic sensors in the preset areas of the grounding wires at both ends of the high-voltage cable under test;

[0073] This invention addresses the typical structural characteristics of double-ended grounding in high-voltage cable systems by employing a non-contact measurement scheme, the topology of which is as follows: Figure 2 As shown. Measurement points are set at both ends of the grounding area (x=0 and x=L) of the cable grounding wire (length L). Harmonic sensors are deployed at a distance of 5-10cm from the grounding wire to achieve long-term monitoring of the amplitude-frequency characteristics of harmonic current in the metal sheath.

[0074] The non-contact harmonic signal sensor provided by this invention adopts a composite magnetic core structure design, consisting of ferrite, multi-turn coil, analog data acquisition board, battery, and housing, etc. Figure 3 As shown. The harmonic sensor has a coil radius r, permeability μ, number of coil turns N, coil resistance R, distance a between the sensor and the wire, distance x between the coil and the wire, and ω is the angular frequency of the sheath current. Figure 4 As shown.

[0075] When the cable sheath current I in =I m When cos(ωt) passes through, the coil in the sensor induces a voltage V. in for:

[0076]

[0077] V in This is the differential form of the cable sheath current signal. To prevent slight high-frequency components from inducing excessively high output voltage at the coil output, thus causing the signal to be overwhelmed, an integral correction circuit is used to restore the induced voltage of the sensor coil, such as... Figure 5 As shown, the output voltage V of the coil is obtained. out and current signal I out for:

[0078]

[0079] Step 102: The harmonic signal output by the harmonic sensor is acquired by the signal acquisition module based on the sampling interval, and the harmonic signal is transmitted to the data analysis and processing module via the data transmission module.

[0080] Preferably, the harmonic signal is subjected to windowed Fourier analysis by a data analysis and processing module to obtain harmonic current data in the harmonic signal, including:

[0081] The window function-based sample of the Hanning window is:

[0082]

[0083] i ω (n) = i(n)·ω(n)

[0084] Where ω(n) is the window function value of the Hanning window function at the nth discrete point, and i(n) is the instantaneous value of the original current signal at the nth discrete sampling point. ω (n) is the current signal value of the nth discrete sampling point after Hanning window weighting, where N is the upper limit of the harmonic order and n refers to the nth harmonic.

[0085] The spectrum of the measured harmonic signal sample after windowed Fourier analysis is as follows:

[0086]

[0087] Where I(k) is the spectral amplitude (or spectral coefficient) at the corresponding frequency point k after windowed Fourier analysis, j is the imaginary unit, and k is the frequency index.

[0088] Step 103: Perform windowed Fourier analysis on the harmonic signal using the data analysis and processing module to obtain the harmonic current data in the harmonic signal;

[0089] Step 104: Calculate the key quantitative indicators of the harmonic signal based on the harmonic current data;

[0090] Preferably, the key quantitative indicators include the effective value of the harmonic current I. RMS The effective value of harmonic current I RMS The calculation formula is:

[0091]

[0092] Where I1, I2, ..., I n , which are the effective current values ​​of the fundamental wave and the 2nd to nth harmonics in the harmonic signal, respectively.

[0093] Preferably, key quantitative indicators include total harmonic distortion (THD). I Total Harmonic Distortion (THD) I The calculation formula is:

[0094]

[0095] Where N is the upper limit of the harmonic order in the harmonic signal.

[0096] Preferably, the key quantitative indicator includes the nth harmonic content K of the defective cable. n The nth harmonic content K of the defective cable n The calculation formula is:

[0097]

[0098] Preferably, the key quantitative indicators include the relative harmonic content R. n Relative harmonic content R n The calculation formula is:

[0099]

[0100] Among them, K n * The nth harmonic content of a defect-free cable.

[0101] The online harmonic signal monitoring system provided by this invention includes a non-contact harmonic signal sensor, a data acquisition module, a data transmission module, a data analysis and processing module, a storage device, a power management module, and a display module, such as... Figure 6 As shown.

[0102] The signal acquisition module includes a digital signal processor (DSP) with a sampling rate set at 51.2 kHz, meaning 1024 sampling points per cycle waveform. This DSP employs a 16-bit synchronous sampling A / D converter chip, enabling high-precision, fast-response, and synchronous sampling of harmonic signals from the harmonic signal sensor. Furthermore, to eliminate measurement errors caused by frequency deviations, the module utilizes a hardware-software combined phase-locked loop (PLL) technology for automatic frequency tracking (±0.01 Hz frequency tracking accuracy) and real-time adjustment of the sampling interval, avoiding frequency loss. After digital signal acquisition, the data transmission module transmits the monitoring data to the data analysis and processing module based on a synchronous transmission protocol over fiber optic media, achieving a signal delay of <1 μs.

[0103] The data analysis and processing module utilizes a microprocessor with an Advanced Reduced Instruction Set Machine (ARM) architecture for data calculation, statistics, display, and storage, and is controlled via a Linux embedded operating system as the software platform. This module performs windowed Fourier analysis on the acquired high-voltage cable harmonic signals, extracting the 2nd to 20th harmonic current data from the measured signal. It observes the amplitude-frequency characteristics of specific harmonic currents, clarifies the amplification factor setting, and analyzes the degree of harmonic anomaly in the high-voltage cable's metallic sheath by calculating key quantitative indicators of harmonic current, such as the effective value (RMS), total harmonic distortion (THD), individual harmonic content (Kn), and relative harmonic content (Rn), thereby assessing the degree of cable insulation degradation. Specifically:

[0104] The window function-based sample of the Hanning window is:

[0105]

[0106] i ω (n)=i(n)·ω(n) (5)

[0107] The spectrum of the measured harmonic signal sample after windowed Fourier analysis is as follows:

[0108]

[0109] The effective value of harmonic current is a physical quantity that characterizes the magnitude of alternating current and reflects the total heating effect of the current containing fundamental and harmonic components.

[0110]

[0111] Total harmonic distortion (THD) reflects the ratio of the amplitudes of all harmonic currents to the amplitude of the fundamental current, and its calculation formula is:

[0112]

[0113] Individual harmonic content refers to the magnitude of harmonic current at a single frequency. They are typically used to analyze the specific impact of harmonics at a particular frequency on a system. I1, I2, ..., I n , respectively, are the effective values ​​of the fundamental frequency and the 2nd to nth harmonics, where N is the upper limit of the harmonic order, and K is the effective value of the fundamental frequency and the 2nd to nth harmonics. n and K n * R represents the nth harmonic content of defective and non-defective cables, respectively. n The relative harmonic content of the defective cable sample.

[0114]

[0115] The relative harmonic content refers to the ratio of the nth harmonic of a defective cable to that of a defect-free cable. It is used to characterize the effect of defects on the induced current of the cable's metal shielding layer under the same measurement conditions.

[0116]

[0117] The display module provides a user interface, allowing for intuitive and convenient operation of the device, display of test results, and adjustment of test parameters. Furthermore, the power management module, equipped with a 2000mAh lithium battery, provides a stable and reliable power supply, enabling the device to operate stably for 24 hours without an external power source.

[0118] This online harmonic signal monitoring method and system, through the aforementioned highly integrated and precise hardware components, can provide efficient and accurate harmonic signal monitoring in the field. After verification, the measured accuracy of the equipment is shown in Table 1, meeting the requirements of the national standard Class A for harmonic signal monitoring indicators. It is well-suited for online monitoring and analysis of abnormal harmonic signals in high-voltage cables.

[0119] Table 1 Accuracy of Harmonic Signal Monitoring System

[0120]

[0121] Step 105: Analyze the degree of harmonic anomaly of the tested high-voltage cable based on key quantitative indicators, and evaluate the degree of degradation of the tested high-voltage cable based on the analysis results.

[0122] The beneficial effects of this invention are:

[0123] 1) It can achieve online measurement without interrupting the power supply to the cable, making it convenient to use.

[0124] 2) The technology is convenient and can analyze the harmonic signal detection results in real time according to the actual situation on site.

[0125] This invention proposes an online monitoring method for harmonic signals in high-voltage cables, comprising: non-contact measurement of sheath harmonic current based on a double-grounded structure, windowed Fourier spectrum analysis, and calculation of harmonic distortion quantification index. This invention acquires and analyzes the amplitude-frequency characteristics of harmonic signals in the tested cable line by using non-contact sensors to monitor harmonic currents through grounding wires at both ends of the high-voltage cable, thereby achieving online monitoring of abnormal harmonic signals in high-voltage cable lines.

[0126] Through field testing and verification on a 150m long cross-linked polyethylene high-voltage cable in a 220kV transmission line, this system continuously monitors the harmonic current signal of the metal sheath of the grounding wire (x=0 / L) at both ends of the cable under different load conditions. Figure 7 The image shows the harmonic current spectrum i(f) captured under typical operating conditions. After windowed Fourier transform and Hanning window function processing, it is as follows: Figure 8 As shown, the amplitudes of the 3rd (150Hz), 5th (250Hz), and 7th (350Hz) harmonic components were found to be significantly higher, indicating that there may be latent defects in the cable insulation.

[0127] Figure 9 This is a system structure diagram for online monitoring of harmonic signal anomalies in high-voltage cables according to a preferred embodiment of the present invention.

[0128] like Figure 9 As shown, this invention provides a system for online monitoring of abnormal harmonic signals in high-voltage cables. The system includes:

[0129] Setting unit 901 is used to set harmonic sensors in the preset area of ​​the grounding wire at both ends of the high voltage cable under test;

[0130] The acquisition unit 902 is used to acquire the harmonic signal output by the harmonic sensor based on the sampling interval through the signal acquisition module. The harmonic signal is transmitted to the data analysis and processing module via the data transmission module.

[0131] Analysis unit 903 is used to perform windowed Fourier analysis on harmonic signals through data analysis and processing module to obtain harmonic current data in harmonic signals;

[0132] Preferably, the analysis unit 903 is used to perform windowed Fourier analysis on the harmonic signal through the data analysis and processing module to obtain harmonic current data in the harmonic signal, and is also used for:

[0133] The window function-based sample of the Hanning window is:

[0134]

[0135] i ω (n) = i(n)·ω(n)

[0136] Where ω(n) is the window function value of the Hanning window function at the nth discrete point, and i(n) is the instantaneous value of the original current signal at the nth discrete sampling point. ω (n) is the current signal value of the nth discrete sampling point after Hanning window weighting, where N is the upper limit of the harmonic order and n refers to the nth harmonic.

[0137] The spectrum of the measured harmonic signal sample after windowed Fourier analysis is as follows:

[0138]

[0139] Where I(k) is the spectral amplitude (or spectral coefficient) at the corresponding frequency point k after windowed Fourier analysis, j is the imaginary unit, and k is the frequency index.

[0140] Calculation unit 904 is used to calculate key quantitative indicators of harmonic signals based on harmonic current data;

[0141] Preferably, the key quantitative indicators include the effective value of the harmonic current I. RMS The effective value of harmonic current I RMS The calculation formula is:

[0142]

[0143] Where I1, I2, ..., I n , which are the effective current values ​​of the fundamental wave and the 2nd to nth harmonics in the harmonic signal, respectively.

[0144] Preferably, key quantitative indicators include total harmonic distortion (THD). I Total Harmonic Distortion (THD) I The calculation formula is:

[0145]

[0146] Where N is the upper limit of the harmonic order in the harmonic signal.

[0147] Preferably, the key quantitative indicator includes the nth harmonic content K of the defective cable. n The nth harmonic content K of the defective cable n The calculation formula is:

[0148]

[0149] Preferably, the key quantitative indicators include the relative harmonic content R. n Relative harmonic content R n The calculation formula is:

[0150]

[0151] Among them, K n * The nth harmonic content of a defect-free cable.

[0152] Result unit 905 is used to analyze the degree of harmonic anomaly of the tested high-voltage cable based on key quantitative indicators, and to evaluate the degree of degradation of the tested high-voltage cable based on the analysis results.

[0153] The preferred embodiment of the present invention provides a system for online monitoring of harmonic signal anomalies in high-voltage cables, which corresponds to another preferred embodiment of the present invention, a method for online monitoring of harmonic signal anomalies in high-voltage cables, and will not be described in detail here.

[0154] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0155] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0156] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1The function specified in one or more boxes.

[0157] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0158] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0159] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

[0160] The invention has been described with reference to a few embodiments. However, as will be known to those skilled in the art, and as defined in the appended claims, other embodiments besides those disclosed above fall equivalently within the scope of the invention.

[0161] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the art, unless otherwise expressly defined herein. All references to “a / the / the [device, component, etc.]” ​​are openly interpreted as at least one instance of said device, component, etc., unless otherwise expressly stated. The steps of any method disclosed herein need not be performed in the exact order disclosed unless explicitly stated otherwise.

Claims

1. A method for online monitoring of abnormal harmonic signals in high-voltage cables, the method comprising: Harmonic sensors are installed in the preset area of ​​the grounding wire at both ends of the high-voltage cable under test; The harmonic signal output by the harmonic sensor is acquired by the signal acquisition module based on the sampling interval, and the harmonic signal is transmitted to the data analysis and processing module via the data transmission module. The harmonic signal is subjected to windowed Fourier analysis by the data analysis and processing module to obtain the harmonic current data in the harmonic signal; Calculate the key quantitative indicators of the harmonic signal based on the harmonic current data. The degree of harmonic anomaly of the tested high-voltage cable is analyzed based on the key quantitative indicators, and the degree of degradation of the tested high-voltage cable is evaluated based on the analysis results.

2. The method according to claim 1, wherein performing windowed Fourier analysis on the harmonic signal through the data analysis and processing module to obtain harmonic current data in the harmonic signal includes: The window function-based sample of the Hanning window is: i ω (n)=i(n)·ω(n) Where ω(n) is the window function value of the Hanning window function at the nth discrete point, and i(n) is the instantaneous value of the original current signal at the nth discrete sampling point. ω (n) is the current signal value of the nth discrete sampling point after Hanning window weighting, where N is the upper limit of the harmonic order and n refers to the nth harmonic. The spectrum of the measured harmonic signal sample after windowed Fourier analysis is as follows: Where I(k) is the spectral amplitude or spectral coefficient at the corresponding frequency point k after windowed Fourier analysis, j is the imaginary unit, and k is the frequency index.

3. The method according to claim 1, wherein the key quantitative indicator includes the effective value of harmonic current I. RMS The effective value of the harmonic current I RMS The calculation formula is: in, I1, I2, ..., I n , which are the effective current values ​​of the fundamental wave and the 2nd to nth harmonics in the harmonic signal, respectively.

4. The method according to claim 3, wherein the key quantitative indicator includes total harmonic distortion (THD). I The total harmonic distortion (THD) I The calculation formula is: in, N is the upper limit of the harmonic order in the harmonic signal.

5. The method according to claim 3, wherein the key quantitative indicator includes the nth harmonic content K of the defective cable. n The nth harmonic content K of the defective cable n The calculation formula is:

6. The method according to claim 5, wherein the key quantitative indicator includes the relative harmonic content R. n The relative harmonic content R n The calculation formula is: in, K n * The nth harmonic content of a defect-free cable.

7. A system for online monitoring of abnormal harmonic signals in high-voltage cables, the system comprising: The setting unit is used to set harmonic sensors in the preset area of ​​the grounding wire at both ends of the high-voltage cable under test. The acquisition unit is used to acquire the harmonic signal output by the harmonic sensor based on the sampling interval through the signal acquisition module, and the harmonic signal is transmitted to the data analysis and processing module via the data transmission module. The analysis unit is used to perform windowed Fourier analysis on the harmonic signal through the data analysis and processing module to obtain harmonic current data in the harmonic signal; The calculation unit is used to calculate the key quantitative indicators of the harmonic signal based on the harmonic current data; The results unit is used to analyze the degree of harmonic anomaly of the tested high-voltage cable based on the key quantitative indicators, and to evaluate the degree of degradation of the tested high-voltage cable based on the analysis results.

8. The system according to claim 7, wherein the analysis unit is configured to perform windowed Fourier analysis on the harmonic signal through the data analysis and processing module to obtain harmonic current data in the harmonic signal, and is further configured to: The window function-based sample of the Hanning window is: i ω (n)=i(n)·ω(n) in, ω(n) is the value of the Hanning window function at the nth discrete point, and i(n) is the instantaneous value of the original current signal at the nth discrete sampling point. ω (n) is the current signal value of the nth discrete sampling point after Hanning window weighting, where N is the upper limit of the harmonic order and n refers to the nth harmonic. The spectrum of the measured harmonic signal sample after windowed Fourier analysis is as follows: Where I(k) is the spectral amplitude or spectral coefficient at the corresponding frequency point k after windowed Fourier analysis, j is the imaginary unit, and k is the frequency index.

9. The system according to claim 7, wherein the key quantitative indicator includes the effective value of the harmonic current I. RMS The effective value of the harmonic current I RMS The calculation formula is: in, I1, I2, ..., I n , which are the effective current values ​​of the fundamental wave and the 2nd to nth harmonics in the harmonic signal, respectively.

10. The system according to claim 9, wherein the key quantitative indicator includes total harmonic distortion (THD). I The total harmonic distortion (THD) I The calculation formula is: in, N is the upper limit of the harmonic order in the harmonic signal.

11. The system according to claim 9, wherein the key quantitative indicator includes the nth harmonic content K of the defective cable. n The nth harmonic content K of the defective cable n The calculation formula is:

12. The system according to claim 11, wherein the key quantitative indicator includes the relative harmonic content R. n The relative harmonic content R n The calculation formula is: in, K n * The nth harmonic content of a defect-free cable.

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