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CN-121978460-A - Cable fault positioning method based on non-fault phase current cross correlation

CN121978460ACN 121978460 ACN121978460 ACN 121978460ACN-121978460-A

Abstract

A cable fault positioning method based on non-fault phase current cross correlation comprises the following steps of S1, performing indirect reconstruction of fault traveling wave signals and obtaining reconstructed signals Step S2 of reconstructing the signal obtained in step S1 Performing extremely-overlapped discrete wavelet transform multi-scale decomposition and obtaining optimal detail coefficients Step S3, obtaining the optimal detail coefficient obtained in step S2 Is the autocorrelation function of (2) And obtain traveling wave propagation time difference Step S4, determining the propagation speed v of the traveling wave in the cable, and finally determining the distance L between the fault point and the measuring point, and positioning the fault point of the cable through the steps.

Inventors

  • Zhu Zongzhang
  • ZENG XU
  • Ke Youliang
  • LEI KAI
  • GONG JUQIANG
  • CHEN YONG
  • LIU ZHIHUA
  • LIU JUN
  • WANG WANBING
  • HAO SIYU
  • Hong Siyun

Assignees

  • 国网湖北省电力有限公司十堰东风供电公司

Dates

Publication Date
20260505
Application Date
20260204

Claims (10)

  1. 1. The cable fault positioning method based on non-fault phase current cross correlation is characterized by comprising the following steps of: Step S1, performing indirect reconstruction of fault traveling wave signals and obtaining reconstructed signals ; Step S2 for the reconstructed signal obtained in step S1 Performing extremely-overlapped discrete wavelet transform multi-scale decomposition and obtaining optimal detail coefficients ; Step S3, obtaining the optimal detail coefficient obtained in the step S2 Is the autocorrelation function of (2) And obtain traveling wave propagation time difference ; Step S4, determining the propagation speed v of the traveling wave in the cable, and finally determining the distance L between the fault point and the measuring point; the positioning of the cable fault point is realized through the steps.
  2. 2. The method of claim 1, wherein in step S1, when a fault occurs in one of the phases in the three-phase cable system, current transient signals of the remaining non-faulty phases are collected And Reconstructing traveling wave current signals of fault phases through kirchhoff current law The method specifically comprises the following steps: (1); Wherein, the And Is the traveling wave component extracted from the non-fault phase current.
  3. 3. The method according to claim 1, characterized in that in step S2, optimal detail coefficients are selected based on signal-to-noise ratio and energy concentration criteria For subsequent analysis.
  4. 4. A method according to claim 3, characterized in that in step S3, an autocorrelation function is obtained The following formula is adopted: (2); Wherein, the Refers to delay The optimal detail coefficient is obtained.
  5. 5. The method according to claim 4, wherein in step S3, the step of detecting is performed by detecting At the position of First significant peak position within interval Acquiring traveling wave propagation time difference : (3)。
  6. 6. Method according to one of claims 1 to 5, characterized in that in step S4 the distance L of the fault point from the measuring point is calculated from the cable wave speed v and the time difference Δt: (4)。
  7. 7. the method of claim 6, wherein the wave velocity v is defined by the inductance per unit length of the cable And capacitor And (3) determining: (5)。
  8. 8. The method of claim 1, further comprising the step of 5 performing an error analysis and confidence assessment by assessing a total error range of the positioning result At the same time, the signal-to-noise ratio SNR and the peak value ratio of the autocorrelation function of the integrated signal Sum wave velocity relative error These multiple factors construct and calculate the integrated confidence function C. Final output of the fault distance L, possible error range ± And confidence level, provide the quantization basis for operation and maintenance decision.
  9. 9. The method according to claim 1, wherein in step 2, the number of decomposed layers J is adaptively determined according to the cable length and the sampling rate, and the preferred frequency band is a high frequency scale corresponding to the energy concentration of the traveling wave head. In step 4, if the cable model is known, the wave speed v of the cable is directly obtained from the parameter library, otherwise, the wave speed is calibrated through the cable section with known length.
  10. 10. The method according to claim 1, wherein in step 3, a dynamic threshold is set for removing false peaks caused by noise Where α ε (0, 1) only if the peak is greater than Is identified as a valid peak.

Description

Cable fault positioning method based on non-fault phase current cross correlation Technical Field The invention relates to the technical field of power systems and related equipment, in particular to a power cable fault detection and positioning technology, and particularly relates to a cable fault accurate positioning method based on parallel non-fault phase current signal indirect acquisition and cross correlation analysis. Background Along with the continuous improvement of the urban power grid cabling rate, the rapid and accurate positioning of cable faults has important significance for guaranteeing the power supply reliability. The traditional cable fault positioning method is mainly dependent on outage detection or artificial waveform analysis, has the problems of high safety risk, low efficiency, large influence by human factors and the like, and the traveling wave method has the advantage of high theoretical precision, but the traditional implementation of the traveling wave method needs to be directly coupled with high-voltage signals, and the wave head identification is obviously influenced by noise, so that the traveling wave method is difficult to safely and reliably apply in an electrified detection scene; the existing cable fault positioning technology mainly has the following problems: 1. The safety risk is high, the traditional traveling wave detection needs to be directly connected with a high-voltage fault phase, and the electric potential safety hazard exists, so that the method is not suitable for electrified detection of urban cables. For example, "development and application of an on-line monitoring and positioning system for power distribution network cable faults" proposes a four-in-one on-line monitoring system (partial discharge+sheath circulation+traveling wave line selection+ranging), but traveling wave signals still need to be collected from the vicinity of a fault phase (incompletely isolated high voltage), and the wave head identification depends on a "fixed threshold value+manual assistance", and the positioning error is about 80-120m under strong noise (20 dB). The potential safety hazard of the technology is rooted in the physical mode of signal acquisition. The traveling wave distance measurement function depends on that a sensor is arranged on a fault phase cable or bus to directly measure transient traveling wave signals generated by faults, and the principle can be simplified as follows: The direct contact measurement requires direct electrical connection or tight electromagnetic coupling of the sensor, the acquisition circuit and the high-voltage conductor, which leads to exposure of the whole process of equipment deployment, operation and maintenance to high-voltage risk, and essentially bears additional safety risks for acquiring signals. 2. The positioning accuracy is not enough, and the time difference extraction accuracy is limited due to the subjective influence of noise interference and artificial wave head identification, so that the positioning error is larger. Depending on experience judgment, an automatic and intelligent signal processing and fault recognition mechanism is lacked. For example, in the field of cable fault location, the efficiency and cost of fault investigation are directly determined by the location precision of the underground power cable fault location research. Recent studies (e.g., downhole power cable fault localization studies) have focused on improving accuracy under strong noise through complex signal processing combinations (e.g., SSA-VMD-NTEO), which in turn has proven that conventional approaches present significant challenges in accuracy. Therefore, a safe, high-precision and automatic cable fault positioning method is urgently needed to meet the requirements of intelligent operation and maintenance of urban cable networks. Disclosure of Invention The invention aims to solve the technical defects of high safety risk and insufficient positioning precision of the existing live cable fault positioning technology, so that the existing fault type and the positioning fault position are difficult to effectively identify, and therefore the invention provides a more advanced live cable fault positioning detection technology to meet the requirements of urban cable operation and maintenance. In order to solve the technical problems, the invention adopts the following technical scheme: A cable fault positioning method based on non-fault phase current cross correlation comprises the following steps: Step S1, performing indirect reconstruction of fault traveling wave signals and obtaining reconstructed signals ; Step S2 for the reconstructed signal obtained in step S1Performing extremely-overlapped discrete wavelet transform multi-scale decomposition and obtaining optimal detail coefficients; Step S3, obtaining the optimal detail coefficient obtained in the step S2Is the autocorrelation function of (2)And obtain traveling wave propagation ti