CN108919057B

CN108919057B - Method for processing insertion loss problem in cable fault diagnosis

Info

Publication number: CN108919057B
Application number: CN201810891007.5A
Authority: CN
Inventors: 张刚; 章荣俐; 吕超
Original assignee: Harbin Institute of Technology
Current assignee: Harbin Institute of Technology
Priority date: 2018-08-07
Filing date: 2018-08-07
Publication date: 2020-06-16
Anticipated expiration: 2038-08-07
Also published as: CN108919057A

Abstract

The invention provides a processing method capable of clearly reflecting fault information in a cable after processing, aiming at the problem of signal attenuation caused by cable insertion loss in the cable fault diagnosis process, and belongs to the field of cable fault diagnosis. The invention obtains D through vector network in the process of cable fault diagnosis₂₁And D₁₁Is processed to obtain a transmission coefficient D 'not including attenuation due to cable insertion loss'₂₁And coefficient of reflection

N points are arranged in the length direction of the cable, and the distance between the ith point on the cable and one port of the cable is taken as a cable micro-element section x_iI is 1,2,3 … n, α represents the attenuation constant of unit length corresponding to the model of the cable;

x_jand j represents the j-th cable micro element section with the fault, and takes the corresponding value of the cable micro element section with the fault in n positions.

Description

Method for processing insertion loss problem in cable fault diagnosis

Technical Field

The invention belongs to the field of cable fault diagnosis, and particularly relates to a method for processing a detection signal attenuation problem caused by cable insertion loss in a cable fault diagnosis process.

Background

The importance of the cable to production and life of modern people is self-evident, however, the cable also belongs to a consumable material, and with the continuous increase of service life and the action of influence factors such as electromagnetic field, mechanical stress, chemical corrosion and thermal effect during work, insulation aging and damage can be caused, so that the cable breaks down, and inconvenience is brought to power utilization and communication of users. Therefore, the cable fault effective diagnosis method capable of quickly detecting and searching the fault position has important significance for recovering power supply and communication and reducing the influence caused by the cable fault to the minimum.

At present, a plurality of methods for diagnosing the cable fault are provided, wherein most of the methods adopt a reflection measurement detection method, namely a port of the cable is found out, a detection signal is loaded to the cable through the port, and the difference and the homogeneity of the reflection signal and the incident signal are compared and analyzed to determine the fault type and the fault information of the cable. However, in practice, the cables used are lossy, have an attenuation effect on the transmitted signals, and the attenuation effect becomes more pronounced as the frequency of the detected signals and the length of the cable to be tested increase. This results in a limitation of the diagnostic length of the cable and the frequency of the applied detection signal, which directly affects the resolution and accuracy of the fault diagnosis of the cable, especially when the cable is diagnosed using frequency domain reflectometry. Therefore, how to solve the problem of signal attenuation caused by cable insertion loss (insertion loss) in the cable fault diagnosis process is a key point for breaking through the limitation of the existing cable fault diagnosis method on the cable detection length and the detection signal frequency, pursuing a cable fault diagnosis method with higher resolution and more accuracy and realizing the diagnosis of the cable soft fault. The current solution to this problem is simply to amplify the detected signal, and such a processing method amplifies the useful signal and further amplifies the noise signal, which is not favorable for extracting the fault information. In reality, the attenuation process of the cable to the signal is much more complicated, and the corresponding treatment needs to be carried out according to the internal mechanism of the cable to the signal attenuation action, so that the problem can be effectively solved.

Disclosure of Invention

Aiming at the problem of signal attenuation caused by cable insertion loss in the cable fault diagnosis process, the invention provides a processing method which can clearly reflect fault information in a cable after processing.

The invention relates to a method for processing a loss problem in cable fault diagnosis, which comprises the following steps:

the method comprises the following steps: selecting a cable to be diagnosed, and manufacturing two ends of the cable into connector joints;

step two: connecting the cable in the first step with a vector network analyzer through a connector joint, and selecting a frequency range of a detection signal;

step three: setting the sweep frequency range of the detection signal in the frequency range selected in the step two, and measuring the transmission coefficient D₂₁And a reflection coefficient D₁₁；

Step four: respectively the transmission coefficient D of the cable₂₁And a reflection coefficient D₁₁The initial value supplement of (2) is complete;

step five: to D₂₁Processing to obtain a transmission coefficient D without attenuation caused by cable insertion loss₂′₁：

step six: to D₁₁Is processed to obtain D₁′₁：

Step seven: to D₁′₁Processing to obtain a reflection coefficient D ″, which does not contain attenuation caused by cable insertion loss₁₁；

It is preferable that the first and second liquid crystal layers are formed of,

r, L, G and C respectively represent the equivalent resistance, equivalent inductance, equivalent conductance and equivalent capacitance of the cable, and the values of the parameters are determined by the specific model of the cable.

Preferably, in the second step, the method for selecting the frequency range of the detection signal includes:

and detecting the insertion loss curve of the cable by using a vector network analyzer, and determining the frequency range of the detection signal when the insertion loss value corresponding to the maximum detection frequency is not more than-45 dB.

Preferably, in the fourth step, D in the third step is extrapolated by using hermitian interpolation₂₁And D₁₁The initial value complement of (a) is complete.

The features mentioned above can be combined in various suitable ways or replaced by equivalent features as long as the object of the invention is achieved.

The method has the beneficial effects that the D acquired by the vector network in the cable fault diagnosis process is utilized₂₁And D₁₁The data of (2) is processed, so that the processed data is close to the detection result of an ideal transmission line. Compared with the existing method for amplifying the attenuated signal by directly using the amplifying circuit, the method does not need the support of extra hardware such as the amplifying circuit in the diagnosis equipment, and the signal is processed in a targeted manner according to the attenuation principle of the cable to the signal, so that the processed result is more accurate, and the fault information in the cable can be clearly reflected.

Drawings

Fig. 1 is a schematic view of the cable fault diagnosis apparatus of the present invention detecting a cable fault.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

The invention is further described with reference to the following drawings and specific examples, which are not intended to be limiting.

The present embodiment will be described with reference to fig. 1, which shows a high-speed synchronous display card according to the present embodiment,

the method comprises the following steps: selecting a cable to be diagnosed, and manufacturing two ends of the cable into connector joints, namely BNC joints connected with a vector network analyzer in the embodiment;

step two: connecting the cable in the step one with a vector network analyzer through a connector joint, detecting an insertion loss curve of the cable by using the vector network analyzer, and determining the frequency range of a detection signal when an insertion loss value corresponding to the maximum detection frequency is not more than-45 dB;

Step four: respectively using an extrapolation method of Hermite interpolation to convert D in the third step₂₁And D₁₁The initial value supplement of (2) is complete;

step five: to D₂₁Processing to obtain a reflection coefficient D without attenuation caused by cable insertion loss₂′₁：

r, L, G and C respectively represent the equivalent resistance, equivalent inductance, equivalent conductance and equivalent capacitance of the cable, and the parameter values are determined according to the specific model of the cable;

step six: to D₁₁Is processed to obtain D₁′₁：

After two treatments, D' can be considered₁₁Is a reflection coefficient that does not include attenuation due to cable insertion loss.

The embodiment further processes the data obtained by the cable reflection measurement, so that the influence caused by cable insertion loss can be eliminated as much as possible in the processed data, and the fault diagnosis of the actual cable is equivalent to the fault diagnosis of an ideal transmission line. The detection length of the cable can be greatly increased by processing the cable insertion loss problem, so that the bottleneck of a cable fault diagnosis technology is broken through.

Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that features described in different dependent claims and herein may be combined in ways different from those described in the original claims. It is also to be understood that features described in connection with individual embodiments may be used in other described embodiments.

Claims

1. A method for handling a loss problem in cable fault diagnosis, the method comprising:

step five: transmission coefficient to cable D₂₁Treated to obtain a transmission coefficient D 'not including attenuation due to cable insertion loss'₂₁：

step six: to D₁₁Is processed to obtain D'₁₁：

Step seven: to D'₁₁Processing to obtain a reflection coefficient D ″, which does not contain attenuation caused by cable insertion loss₁₁；

2. The method for processing the insertion loss problem in the cable fault diagnosis according to claim 1, wherein in the second step, the method for selecting the frequency range of the detection signal comprises:

3. The method as claimed in claim 2, wherein in the fourth step, D in the third step is interpolated by Hermite interpolation₂₁And D₁₁The initial value complement of (a) is complete.