CN-120522513-B - Cable defect detection device based on double-path coupling frequency domain reflection

CN120522513BCN 120522513 BCN120522513 BCN 120522513BCN-120522513-B

Abstract

The invention provides a cable defect detection device based on double-path coupling frequency domain reflection, and belongs to the technical field of power cable detection. The system comprises a master control module, a double-path coupling signal generator, a first coupler, a second coupler, a first signal comparator and a second signal comparator, wherein the master control module is electrically connected with the double-path coupling signal generator, the input end of the first coupler is connected with the double-path coupling signal generator, the coupling port of the first coupler is connected with a cable to be tested, the output end of the first coupler is connected with the input end of the first signal comparator, the output end of the first signal comparator is connected with the input end of the second signal comparator, the input end of the second coupler is connected with the double-path coupling signal generator, the output end of the second coupler is connected with the second signal comparator, and the output ends of the first signal comparator and the second signal comparator are electrically connected with the master control module. The invention overcomes the problem of phase ambiguity of single-path measurement by utilizing the double-path signal comparison structure, and remarkably improves the accuracy and reliability of cable defect detection.

Inventors

LIU HAOLIANG
FU KAI
PAN XINYUE
ZHAO LANXI
Du Yike
JI YI
XIA TIANYANG
XIAO MENG
DU BOXUE

Assignees

天津大学

Dates

Publication Date: 20260508
Application Date: 20250703

Claims (8)

1. The cable defect detection device based on the double-path coupling frequency domain reflection is characterized by comprising a master control module, a double-path coupling signal generator, a first coupler, a second coupler, a first signal comparator and a second signal comparator; the master control module is electrically connected with the two-way coupling signal generator; the input end of the first coupler is connected with the double-path coupling signal generator, the coupling port of the first coupler is connected with a cable to be tested, the output end of the first coupler is connected with the input end of the first signal comparator, and the output end of the first signal comparator is connected with the input end of the second signal comparator; The master control module determines the phase of the reflected signal R 1 by combining the phase characteristics of the preset test signal S 1 and the reference signal S 2 based on the phase difference information output by the first signal comparator and the phase difference information output by the second signal comparator, and the specific process is as follows: Firstly, decomposing the same reflected signal R 1 along the direction of a reference signal S 2 to obtain a real part and an imaginary part; Next, a predetermined phase difference between the test signal S 1 and the reference signal S 2 The relationship is established for the known quantity: ; Finally, the phase difference is checked by comparing the real part and the imaginary part decomposed along the directions of the test signal S 1 and the reference signal S 2 to eliminate the phase ambiguity caused by the uniqueness of the cosine function generated by the single-path measurement, thereby determining the phase information of the reflected signal R 1 ; The master control module further utilizes the phase of the verified reflected signal R 1 and combines the amplitude of the reflected signal R 1 to perform windowing function processing and inverse Fourier transformation on the spectrum characteristics of the reflected signal to obtain time domain reflection characteristics, and determines the defect position of the cable by combining the propagation speed of electromagnetic waves in the cable to be tested.
2. The device for detecting cable defects based on dual-path coupling frequency domain reflection according to claim 1, wherein the dual-path coupling signal generator is controlled by the master control module to generate an associated test signal S 1 and a reference signal S 2 , and the test signal S 1 and the reference signal S 2 are sinusoidal sweep signals.
3. The device according to claim 2, wherein the first coupler is configured to inject the test signal S 1 into the cable under test and separate the reflected signal R 1 generated by the defect, and the first coupler outputs the test signal S 1 and the reflected signal R 1 to the first signal comparator, respectively.
4. The device for detecting a cable defect based on two-way coupling frequency domain reflection according to claim 3, wherein the first signal comparator is configured to compare the amplitude and the phase between the test signal S 1 and the reflected signal R 1 , and output the amplitude difference and the phase difference information between the test signal S 1 and the reflected signal R 1 , and the phase difference calculation formula is: ; Wherein, the For the phase of the reflected signal R 1 , Is the phase of the test signal S 1 .
5. The device of claim 4, wherein the second signal comparator is configured to compare phases of the reference signal S 2 and the reflected signal R 1 , and output phase difference information between the reference signal S 2 and the reflected signal R 1 , where the formula is: ; Wherein, the Is the phase of the reference signal S 2 .
6. The device for detecting cable defects based on two-way coupling frequency domain reflection according to claim 5, wherein the master control module is based on a phase difference output by the first signal comparator The reflected signal R 1 is decomposed into real and imaginary parts along the phase direction of the test signal S 1 , denoted as: real part: ; The imaginary part: ; Component size and phase difference through real and imaginary parts The amplitude of the reflected signal R 1 is determined, with the formula: ; Wherein, the The amplitude of the reflected signal R 1 , and the amplitude of the test signal S 1 and the reflected signal R 1 are combined with the known amplitude of the test signal S 1 .
7. The device of claim 6, wherein the second coupler is configured to transmit a reference signal S 2 to the second signal comparator.
8. The device for detecting a cable defect based on two-way coupling frequency domain reflection according to claim 1, wherein the same reflected signal R 1 is decomposed along the direction of the reference signal S 2 , and the real part and the imaginary part obtained are: real part: ; The imaginary part: ; Wherein, the For the amplitude of the reflected signal R 1 , Is the phase difference between the reference signal S 2 and the reflected signal R 1 .

Description

Cable defect detection device based on double-path coupling frequency domain reflection Technical Field The invention relates to the technical field of power cable detection, in particular to a cable defect detection device based on double-path coupling frequency domain reflection. Background With the continuous upgrade of infrastructure, power cables play an important role in modern power transmission and distribution systems. However, there are various factors such as defects in the installation process, damage from external forces, and severe environmental conditions, which may cause the insulation properties of the cable to be impaired throughout its life cycle from production, installation to operation. These hazards may develop into partial discharges, eventually leading to serious consequences of insulation failure. Therefore, the local damage points on the cable can be accurately positioned, so that the method is not only a key means for preventing the power line from malfunctioning, but also a necessary guarantee for ensuring the safe and reliable operation of the power network. Current techniques for cable fault localization include impedance measurement, partial discharge detection, and traveling wave reflection. Among them, the traveling wave reflection method is favored because it is easy to implement and requires less hardware. The basic idea of the method is to transmit a low-voltage single pulse signal to one end of a cable, when the signal propagates along the cable and encounters a fault point or an impedance discontinuity, reflection is generated, and the position of the fault point can be calculated by analyzing the time delay between the transmitted pulse and the reflected pulse and according to the propagation rate of electromagnetic waves in a medium. However, the travelling wave reflection method has significant disadvantages. The single pulse used by the method has limited energy, when encountering larger or multiple fault points, the reflected signals become very weak, so that the positioning effectiveness is reduced, meanwhile, the single pulse signal has poor capability of resisting the interference of environmental noise, and in the field with complex electromagnetic interference, useful reflected signals are easily submerged by noise, so that the positioning accuracy is influenced. The high frequency components in the pulse attenuate strongly during long distance transmission, which makes it difficult to detect minor insulation imperfections. In addition, in a cable network including a plurality of branches, reflected signals from different paths are superimposed on each other, which may cause signal confusion, resulting in an increase in positioning error. In summary, the application range of the method is often limited to short-distance and simple fault situations, and it is difficult to cope with the higher requirements of the modern power system for high precision and detection under complex conditions. In addition, there are significant limitations to determining defect locations using single-pass frequency domain reflection. Due to the non-uniqueness of the phase of the reflected signal, the true phase of the reflected signal cannot be accurately determined. For example, when the phase difference between the reflected signal R 1 and the incident signal S 1 is Δθ 1, the real part of the reflected signal R 1 can be expressed by the following formula: Wherein, the However, due to the periodicity and symmetry of the cosine function, there are several possible solutions for such characterization, namely that the real part of the reflected signal may correspond to several phase states when the phase difference Δθ 1 is a certain value. The phenomenon can not uniquely determine the phase of the reflected signal only by relying on a single-path signal, thereby causing phase ambiguity and affecting the accuracy of defect positioning. Disclosure of Invention In order to overcome the defects of the prior art, the invention aims to provide the cable defect detection device based on the double-path coupling frequency domain reflection, which solves the problem of phase ambiguity of single-path measurement by utilizing a double-path signal comparison structure and remarkably improves the accuracy and reliability of cable defect detection. In order to achieve the above object, the present invention provides the following solutions: The cable defect detection device based on double-path coupling frequency domain reflection comprises a master control module, a double-path coupling signal generator, a first coupler, a second coupler, a first signal comparator and a second signal comparator, wherein the master control module is electrically connected with the double-path coupling signal generator, the input end of the first coupler is connected with the double-path coupling signal generator, the coupling port of the first coupler is connected with a cable to be detected, the output end of th