CN108919057B - A method for handling the problem of insertion loss in cable fault diagnosis - Google Patents

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

A method for handling the problem of insertion loss in cable fault diagnosis

technical field

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

Background technique

The importance of cables to the production and life of modern people is self-evident. However, cables are also consumables. With the continuous increase of service life and the influence of electromagnetic fields, mechanical stress, chemical corrosion and thermal effects in work, it is possible to Lead to insulation aging and damage, make the cable fail, and bring inconvenience to the user's electricity and communication. Therefore, an effective method for diagnosing cable faults that can quickly detect and locate faults is of great significance for restoring power supply and communication, and minimizing the impact of cable faults.

At present, there are many methods for cable fault diagnosis, most of which use reflection measurement detection method, that is, find the port of the cable and load the detection signal to the cable through the port, and then compare and analyze the similarities and differences between the reflected signal and the incident signal to determine the cable. fault type and fault information. However, the cables used in practice are all lossy, which has an attenuation effect on the transmitted signal, and with the increase of the frequency of the detection signal and the length of the cable to be tested, the attenuation effect becomes more obvious. This will limit the diagnostic length of the cable and the frequency of the added detection signal, especially when using the frequency domain reflectometry to diagnose the cable, the limitation on the frequency will directly affect the resolution and accuracy of the fault diagnosis of the cable. Therefore, how to solve the problem of signal attenuation caused by cable insertion loss (insertion loss) in the process of cable fault diagnosis is to break through the limitation of cable detection length and detection signal frequency in existing cable fault diagnosis methods, and pursue higher resolution. And more accurate cable fault diagnosis method, as well as the key to realize the diagnosis of cable soft fault. The current solution to this problem is to simply amplify the detected signal. Such a processing method amplifies the useful signal and further amplifies the noise signal, which is not conducive to the extraction of fault information. In reality, the attenuation process of the cable to the signal is much more complicated, and it is necessary to deal with the internal mechanism of the attenuation of the signal by the cable, so that such a problem can be effectively solved.

SUMMARY OF THE INVENTION

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

A method for processing the insertion loss problem in the cable fault diagnosis of the present invention, the method includes:

Step 1: Select the cable to be diagnosed, and make both ends into connector joints;

Step 2: Connect the cable in step 1 to the vector network analyzer through the connector, and select the frequency range of the detection signal;

Step 3: in the frequency range selected in step 2, set the frequency sweep range of the detection signal, and measure the transmission coefficient D ₂₁ and the reflection coefficient D ₁₁ ;

Step 4: Complete the initial values of transmission coefficient D ₂₁ and reflection coefficient D ₁₁ of the cable respectively;

Step 5: Process D ₂₁ to obtain a transmission coefficient D ₂ ′ ₁ that does not include attenuation due to cable insertion loss:

Set n points in the length direction of the cable, the distance between the i-th point on the cable and a port of the cable is taken as the cable micro-element segment x _i , i=1, 2, 3...n, α represents the model corresponding to the cable The unit length decay constant of ;

Step 6: Process D ₁₁ to obtain D ₁ ′ ₁ :

Step 7: Process D ₁ ′ ₁ to obtain a reflection coefficient D″ ₁₁ that does not include attenuation due to cable insertion loss;

x _j represents the jth cable micro-element segment that has failed, and j takes the corresponding value of the faulty cable micro-element segment in n positions.

Preferably,

Among them, R, L, G and C represent the equivalent resistance, equivalent inductance, equivalent conductance and equivalent capacitance of the cable, respectively, and the parameter values 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 is:

Use a vector network analyzer to detect the insertion loss curve of the cable, and determine the frequency range of the detection signal when the insertion loss value corresponding to the maximum detection frequency does not exceed -45dB.

Preferably, in the fourth step, the extrapolation method of Hermitian interpolation is used to complete the initial values of D ₂₁ and D ₁₁ in the third step.

The above technical features can be combined in various suitable ways or replaced by equivalent technical features, as long as the purpose of the present invention can be achieved.

The beneficial effect of the present invention is that the present invention processes the data of D ₂₁ and D ₁₁ obtained by the vector network in the process of cable fault diagnosis, so that the processed data is close to the detection result of the ideal transmission line. Compared with the existing method of directly using an amplifier circuit to amplify the attenuated signal, the present invention does not require the support of additional hardware such as an amplifier circuit in the diagnostic equipment, and can be processed in a targeted manner according to the attenuation principle of the cable to the signal. The processed result is more accurate, and the fault information in the cable can be clearly reflected.

Description of drawings

FIG. 1 is a schematic diagram of a cable fault diagnosis device of the present invention detecting a cable fault.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below 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, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

It should be noted that the embodiments of the present invention and the features of the embodiments may be combined with each other under the condition of no conflict.

The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but it is not intended to limit the present invention.

This embodiment will be described with reference to FIG. 1. The high-speed synchronous display card described in this embodiment,

A method for processing the insertion loss problem in the cable fault diagnosis of the present invention includes:

Step 1: Select the cable to be diagnosed, and make both ends into connector joints, in this embodiment, make into BNC joints connected to the vector network analyzer;

Step 2: Connect the cable in step 1 to the vector network analyzer through the connector, use the vector network analyzer to detect the insertion loss curve of the cable, and determine the detection signal when the insertion loss value corresponding to the maximum detection frequency does not exceed -45dB. Frequency Range;

Step 3: in the frequency range selected in step 2, set the frequency sweep range of the detection signal, and measure the transmission coefficient D ₂₁ and the reflection coefficient D ₁₁ ;

Step 4: Use the extrapolation method of Hermitian interpolation to complete the initial values of D ₂₁ and D ₁₁ in Step 3 respectively;

Step 5: Process D ₂₁ to obtain a reflection coefficient D ₂ ′ ₁ that does not include attenuation due to cable insertion loss:

Set n points in the length direction of the cable, the distance between the i-th point on the cable and a port of the cable is taken as the cable micro-element segment x _i , i=1, 2, 3...n, α represents the model corresponding to the cable The unit length decay constant of ;

Among them, R, L, G and C represent the equivalent resistance, equivalent inductance, equivalent conductance and equivalent capacitance of the cable, respectively, and the parameter values depend on the specific model of the cable;

Step 6: Process D ₁₁ to obtain D ₁ ′ ₁ :

Step 7: Process D ₁ ′ ₁ to obtain a reflection coefficient D″ ₁₁ that does not include attenuation due to cable insertion loss;

x _j represents the jth cable micro-element segment that has failed, and j takes the corresponding value of the faulty cable micro-element segment in n positions.

After two treatments, it can be considered that D″ ₁₁ is a reflection coefficient that does not include attenuation due to cable insertion loss.

This embodiment further processes the data obtained by the cable reflection measurement, so that the influence of the 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 the ideal transmission line. . By dealing with the problem of cable insertion loss, the detection length of the cable can be greatly increased, thereby breaking through the bottleneck of cable fault diagnosis technology.

Although the invention has been described herein with reference to specific embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and other arrangements may be devised without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that the features described in the various dependent claims and herein may be combined in different ways than are described in the original claims. It will also be appreciated that features described in connection with a single embodiment may be used in other described embodiments.

Claims (3)

1. a method for processing the problem of insertion loss in cable fault diagnosis, characterized in that the method comprises: Step 1: Select the cable to be diagnosed, and make both ends into connector joints; Step 2: Connect the cable in step 1 to the vector network analyzer through the connector, and select the frequency range of the detection signal; Step 3: in the frequency range selected in step 2, set the frequency sweep range of the detection signal, and measure the transmission coefficient D ₂₁ and the reflection coefficient D ₁₁ ; Step 4: Complete the initial values of transmission coefficient D ₂₁ and reflection coefficient D ₁₁ of the cable respectively; Step 5: Process the transmission coefficient D ₂₁ of the cable to obtain the transmission coefficient D′ ₂₁ that does not include attenuation due to cable insertion loss:

Set n points in the length direction of the cable, the distance between the i-th point on the cable and a port of the cable is taken as the cable micro-element segment x _i , i=1, 2, 3...n, α represents the model corresponding to the cable The unit length decay constant of ;

Among them, R, L, G and C represent the equivalent resistance, equivalent inductance, equivalent conductance and equivalent capacitance of the cable, respectively, and the parameter values depend on the specific model of the cable; Step 6: Process D ₁₁ to obtain D' ₁₁ :

Step 7: Process D′ ₁₁ to obtain a reflection coefficient D″ ₁₁ that does not include attenuation due to cable insertion loss;

x _j represents the jth cable micro-element segment that has failed, and j takes the corresponding value of the faulty cable micro-element segment in n positions. 2. The method for processing the insertion loss problem in cable fault diagnosis according to claim 1, wherein in the step 2, the method for selecting the frequency range of the detection signal is: Use a vector network analyzer to detect the insertion loss curve of the cable, and determine the frequency range of the detection signal when the insertion loss value corresponding to the maximum detection frequency does not exceed -45dB. 3. the processing method to the insertion loss problem in cable fault diagnosis according to claim 2, is characterized in that, in described step 4, use the extrapolation method of Hermitian interpolation to divide _D21 and D in step 3 The initial value of ₁₁ is complete.

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