Cable detection method and device

Abstract

The invention relates to the technical field of cable detection, and provides a cable detection method and device, and the method comprises the steps: repeatedly transmitting spread spectrum signals with different parameter settings to one end of a detected cable, and receiving reflection signals at the same end of the detected cable; after the reflection signal is obtained each time, converting the reflection signal into a first cable model curve through a spread spectrum signal receiving algorithm; comparing the first cable model curve with the reference model curve Crf to obtain a comparison difference; the reference model curve Crf is a cable model curve when the cable is not damaged; if the comparison difference cannot be zero, judging that the cable is damaged; and calculating the terminal position of the damaged cable, the damage position and the aging degree of the cable based on the obtained cable model curve. According to the invention, the problems of limited detection, influence on equipment and poor accuracy in the existing rail transit cable detection technology can be solved.

Description

Technical Field

[0001] The present disclosure belongs to the technical field of cable detection, and particularly relates to a cable detection method and device. Background Art

[0002] As a signal transmission carrier, the health of a cable is related to the signal transmission quality. As the usage time increases, the cable will age, and it is necessary to evaluate the cable status in order to maintain the cable in a timely manner. When a cable break occurs, it is necessary to determine the break position for corresponding construction and repair.

[0003] The existing rail transit cable detection technologies have the following limitations: 1) Optical inspection: Imaging the cable through X-ray or the like, and visually judging the aging condition according to experience. The disadvantage is that the cable needs to be exposed, which is not suitable for buried cables and cables hidden in the vehicle body.

[0004] 2) Current signal inspection: Sending a current signal at one end and receiving the signal at the other end, and judging the signal characteristics to reflect the cable parameters. The disadvantage is that both the receiving end and the sending end need to be tested simultaneously, which is not suitable for long-distance cables.

[0005] 3) Dielectric withstand test: Injecting a high-voltage signal to check the insulation performance and judge the cable status. The disadvantages are that the high-voltage signal will damage the connected equipment, affect the working signal, power-off inspection is required, and it may cause complete damage to the aged cable.

[0006] 4) Inspection of electrical characteristic parameters such as impedance: Injecting a special signal to test the electrical characteristic parameters such as the impedance of the cable. The disadvantage is that pure cable testing is required, and the cable cannot be connected to external equipment, otherwise the parameters will be distorted.

[0007] 5) Environmental parameter prediction: Predicting the cable aging time through external conditions such as vibration, electromagnetism, temperature, and corrosion. The disadvantage is that this method is only a probabilistic prediction and cannot give a definite conclusion for an individual. Summary of the Invention

[0008] To solve the above problems, the present disclosure provides a cable detection method and device. By inputting a spread spectrum signal to one end of the cable to be measured and receiving the reflected signal at the same end, changing the signal parameters to obtain multiple reflected signals, and processing them through an algorithm to obtain a cable model curve, and using the numerical value of the cable model curve for cable detection. It can solve the problems of limited detection, affecting equipment, and poor accuracy in the existing rail transit cable detection technologies.

[0009] The following are the technical details of the present invention: A cable detection method, characterized by comprising: Repeatedly sending spread spectrum signals with different parameter settings to one end of the cable to be measured, and simultaneously receiving the reflected signals at the same end of the cable to be measured; After receiving the reflected signal each time, the reflected signal is converted into a first cable model curve through a spread spectrum signal receiving algorithm; Compare the first cable model curve with the reference model curve Crf to obtain a comparison difference; the reference model curve Crf is the cable model curve when the set cable has no damage; if the comparison difference cannot be zero, it is determined that the cable is damaged; Based on the obtained cable model curve, calculate the terminal position, damage position, and cable aging degree of the damaged cable.

[0010] Furthermore, The repeatedly sending spread spectrum signals with different parameter settings to one end of the cable under test includes: Adjust and change the parameter settings of the spread spectrum signal based on the difference between the first cable model curve and the reference model curve Crf, so that the difference between the cable model curve obtained next time and the reference model curve Crf is less than the difference of the previous time; If the difference between the cable model curve and the reference model curve Crf cannot be zero, after obtaining M cable model curves, stop sending spread spectrum signals to the same end of the cable under test; M is the number threshold.

[0011] Furthermore, The calculating the terminal position, damage position, and cable aging degree of the damaged cable based on the obtained cable model curve includes: Select the second to the Mth cable model curves C2...C m from the M cable model curves, and apply a decision algorithm to screen the cable model curves in the second to the Mth cable model curves C2...C m in which the terminal peak value is lower than the threshold; Use a fusion algorithm to merge the screened cable model curves into a final cable model curve Cout; Use the final cable model curve Cout to calculate the terminal position, damage position, and cable aging degree of the damaged cable.

[0012] Furthermore, The calculating the terminal position, damage position, and cable aging degree of the damaged cable by using the final cable model curve Cout includes: The terminal position of the cable is: the highest peak position of Cout × the propagation factor of the cable under test under different parameter signals; The damage position of the cable is: the other small peak positions of Cout × the propagation factor of the cable under test under different parameter signals; The cable aging degree Ac is: Ac = Yc × K2 Where Ac = Yc × K2, K2 is a preset aging correction factor, and Yc is the average or maximum value of the peak amplitudes of other small peaks of Cout.

[0013] Further, After receiving the reflected signal at the same end of the cable under test each time, the filtering algorithm is applied to filter out the initial reflected signal, and then the reflected signal is converted into the first cable model curve through the spread spectrum signal receiving algorithm.

[0014] Further, The filtering algorithm is: using coherent demodulation to extract specific delay signals.

[0015] Further, The parameters of the spread spectrum signal include: Carrier frequency fi, pseudo-spread spectrum code frequency fcn, pseudo-spread spectrum code pattern Dn, pseudo-spread spectrum code length Ln; where n is a natural number from 1 to N, and N is the number of groups of pseudo-spread spectrum codes.

[0016] A cable detection device for performing the cable detection method described above, characterized in that it includes: A signal sending module for repeatedly sending spread spectrum signals with different parameter settings to one end of the cable under test; A signal receiving module for simultaneously receiving reflected signals at the same end of the cable under test; A signal analysis module for, after obtaining the reflected signal each time, converting the reflected signal into the first cable model curve through the spread spectrum signal receiving algorithm, comparing the first cable model curve with the reference model curve Crf, and obtaining the comparison difference; the reference model curve Crf is the cable model curve when the set cable has no damage; If the comparison difference cannot be zero, it is determined that the cable is damaged; Based on the obtained cable model curve, calculate the terminal position, damage position, and cable aging degree of the damaged cable.

[0017] Further, It further includes: a signal generation module for generating a standard test vector; The signal sending module converts the standard test vector into an analog signal Sa1 and outputs the analog signal Sa1 as a spread spectrum signal to one end of the cable under test.

[0018] Further, When the cable under test is not disconnected from the external device: The signal analysis module also adjusts the test parameters according to the results analyzed by it, outputs the new test parameters to the signal generation module through feedback information, and is used for the signal generation module to adjust the test vector according to the new parameters for a new round of testing; The signal analysis module obtains the model curve of the final cable aging state according to the multi-round test results and the comparison algorithm.

[0019] Compared with the prior art, the present disclosure has the following advantages: This method uses single-ended testing, only needs to send a spread spectrum signal at one end of the cable and receive the reflected signal, without exposing the whole cable, and is not restricted by the cable length and whether external devices are connected, greatly expanding the applicable scope of detection; and because the power of the spread spectrum signal of this method is low, it will not affect the normal operation of the device, nor cause damage to the cable, avoiding adverse effects on the device and the cable due to detection. Secondly, this method changes the parameters of the spread spectrum signal multiple times. The signals with different parameters have different propagation and reflection situations in the cable, which can comprehensively reflect the cable characteristics; after receiving the reflected signal, the spread spectrum signal receiving algorithm is used to convert the reflected signal into a cable model curve, and then compared with the reference model curve to judge whether there is damage to the cable. Based on the cable model curve, the terminal position, damage position and aging degree are calculated, making the detection result more accurate and capable of giving an accurate evaluation for individual cables.

[0020] Other features and advantages of the present disclosure will be described in the following specification, and part of them will be obvious from the specification, or understood by implementing the present disclosure. The objectives and other advantages of the present disclosure can be achieved and obtained through the structures pointed out in the specification, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present disclosure. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0022] Figure 1 Shows a schematic diagram of the method of the present invention; Figure 2 Shows a schematic diagram of the device of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] To make the objectives, technical solutions and advantages of the embodiments of the present disclosure clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present disclosure with reference to the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are some but not all of the embodiments of the present disclosure. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present disclosure without creative efforts belong to the scope of protection of the present disclosure.

[0024] To solve the problems, the present invention proposes... The technical solutions adopted by the present invention to solve its technical problems are as follows: A cable detection method, as Figure 1 shown, includes: 1. Testing: Output the spread-spectrum analog signal Sa1 to one end of the cable under test; At the same end of the cable under test, simultaneously with the transmission, receive the analog signal Ra1 and convert it into a digital-format received vector Rd1; Apply a filtering algorithm to filter out the initial reflection signal; Apply a spread-spectrum signal receiving algorithm to analyze Rd1 to obtain the first cable model curve C1; Adjust the signal parameters of the spread-spectrum signal multiple times and input them into one end of the cable under test to obtain multiple cable model curves C2...C m . (For the selection of parameters, different parameter adjustment methods are selected according to the parameters of the cable under test and the test results. For example, adjust the signal frequency, adjust the code pattern, adjust the signal power) Specifically, the generation of the analog signal Sa1 includes: Generate a digital test vector according to the initial default parameter group. (The parameter group includes the carrier frequency fi of the spread-spectrum signal, the pseudo-spread-spectrum code frequency fcn, the pseudo-spread-spectrum code pattern Dn, and the pseudo-spread-spectrum code length Ln, where n is a natural number, and the maximum value N of n represents that the signal contains N groups of pseudo-spread-spectrum codes with different parameters).

[0025] Convert the first group of digital test vectors Sd1 into the analog signal Sa1.

[0026] 2. Signal processing: Set a reference curve reference model curve Crf, and the reference model curve Crf is the cable model curve when it is set that the cable has no damage; Compare the first cable model curve C1 (the first cable model curve) with the reference model curve C rf to obtain the comparison difference; Based on the difference between the first cable model curve C1 and the reference model curve Crf, adjust the parameter settings of the spread-spectrum signal so that the difference between the next obtained cable model curve and the reference model curve Crf is less than the previous difference; If the difference between the cable model curve and the reference model curve Crf can be 0, it means that the cable has no damage and there is no need to detect the terminal position, damage position, and cable aging degree of the cable.

[0027] If the difference between the cable model curve and the reference model curve Crf is always not 0 and cannot be 0, obtain M cable model curves C2...C mAfter that, stop sending spread spectrum signals with different parameter settings to the same end of the cable under test.

[0028] Compare C2...C m The terminal peaks V2,..., VM, apply the decision algorithm to delete C2...C m Among them, for the curves with too low terminal peaks, in the remaining curves, apply the fusion algorithm to merge multiple curves into the same curve, denoted as Cout.

[0029] 3. Detection and analysis: Based on the highest peak position of Cout, determine the cable terminal position. Based on the positions of other small peaks of Cout, determine the cable damage position.

[0030] The terminal position of the cable is: the highest peak position of Cout × the propagation factor of the cable under test under different parameter signals; The damage position of the cable is: the positions of other small peaks of Cout × the propagation factor of the cable under test under different parameter signals; Among them, the terminal position of the cable or the damage position of the cable is Pc, the highest peak position of Cout or the positions of other small peaks is Tc, and the relationship between Pc and Tc is: Pc = Tc × K1 Among them, K1 represents the propagation factor of cables of different materials under different parameter signals.

[0031] According to the peak amplitude Yc of other small peaks of Cout, calculate the cable aging degree Ac; Among them, Ac = Yc × K2, K2 is a preset aging correction factor, and Yc is the average value or maximum value of the peak amplitudes of other small peaks of Cout.

[0032] The present invention determines the terminal and damage positions based on the relationship between the signal propagation speed in the cable (reflected by the propagation factor K1) and the time delay of the reflected signal (curve peak position); The change in electrical performance caused by cable aging is reflected in the amplitude of the reflected signal. By establishing a quantitative relationship between the small peak amplitude Yc and the aging degree through the preset aging correction factor K2 to calculate the aging degree, it overcomes the drawbacks of traditional detection techniques.

[0033] Specifically, 1) There are various types of pseudo-spread spectrum codes, typical examples are: M sequence, and the selection of polynomials can be arbitrary.

[0034] 2) There are various types of filtering algorithms, typical examples are: coherent demodulation to extract specific delay signals.

[0035] 3) There are various types of spread spectrum signal reception algorithms, typical examples are: correlation operation.

[0036] 4. There are various types of decision algorithms. Typical examples are: setting a preset threshold as the decision threshold; or taking the median of each value as the decision threshold.

[0037] 5. There are various types of fusion algorithms. Typical examples are: superimposing multiple curves.

[0038] 6. The propagation factor K1 and the aging correction factor K2 are calculated based on a large amount of measured data combined with theoretical analysis. There are various types of quantization algorithms. Typical examples are: the expert scoring method; or normalizing with respect to the relative peak value.

[0039] The present invention has the following functions: 1. Compared with the existing optical inspection scheme, the scheme of the present invention does not require the exposure of the cable. As long as one end of the cable joint is exposed, there are no construction requirements, which saves costs.

[0040] 2. Compared with the existing current signal inspection scheme, only single-end testing of the cable is required, without the need for outdoor long-distance operations, nor the coordination of simultaneous operations at both ends. It is relatively easy to implement and avoids the influence brought by the synchronous error of long-distance operations.

[0041] 3. Compared with the existing withstand voltage inspection scheme, the present invention injects a low signal power, does not affect the operation of the equipment, and does not damage the cable.

[0042] 4. Compared with the inspection of electrical characteristic parameters such as impedance, through iterative testing of multiple groups of signals, the curve with the least influence is selected, excluding the influence of the terminal connection device on signal reflection. There is no requirement to cut off the external connection, which is beneficial to maintaining the connection of the existing equipment on site and reducing the possible impact of construction on safety.

[0043] 5. Compared with the prediction of environmental parameters, it can give an evaluation curve for each individual, with high accuracy and strong pertinence.

[0044] Based on the method of the present invention, the embodiments of the present disclosure also provide a device for executing the above method, as Figure 2 shown, including: A signal sending module, configured to repeatedly send spread spectrum signals with different parameter settings to one end of the cable under test; A signal receiving module, configured to simultaneously receive reflected signals at the same end of the cable under test; A signal analysis module, configured to, after obtaining the reflected signal each time, convert the reflected signal into a first cable model curve through a spread spectrum signal receiving algorithm, compare the first cable model curve with a reference model curve Crf, and obtain a comparison difference; the reference model curve Crf is a cable model curve when it is set that the cable has no damage; If the comparison difference cannot be zero, it is determined that the cable is damaged; Calculate the terminal position, damage position, and cable aging degree of the damaged cable based on the obtained cable model curve.

[0045] When the cable is not disconnected from the external device, the signal analysis module also needs to adjust the test parameters according to the results obtained by the analysis algorithm, output the new parameters to the signal generation module through the feedback information, and the signal generation module adjusts the test vector according to the new parameters for a new round of testing. The signal analysis module obtains the model curve of the final cable aging state according to the comparison algorithm based on the results of multiple rounds of testing.

[0046] Although the present disclosure has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. A cable detection method, characterized in that, Including: Repeatedly sending spread spectrum signals with different parameter settings to one end of the cable under test, and simultaneously receiving reflected signals at the same end of the cable under test; After obtaining the reflected signal each time, converting the reflected signal into a first cable model curve through a spread spectrum signal receiving algorithm; Comparing the first cable model curve with the reference model curve Crf to obtain a comparison difference; the reference model curve Crf is the cable model curve when it is set that the cable has no damage; if the comparison difference cannot be zero, it is determined that the cable has damage; Calculating the terminal position, damage position, and cable aging degree of the damaged cable based on the obtained cable model curve.

2. The cable detection method according to claim 1, wherein The repeatedly sending spread spectrum signals with different parameter settings to one end of the cable under test includes: Adjusting and changing the parameter settings of the spread spectrum signal based on the difference between the first cable model curve and the reference model curve Crf, so that the difference between the cable model curve obtained next time and the reference model curve Crf is less than the difference of the previous time; If the difference between the cable model curve and the reference model curve Crf cannot be zero, after obtaining M cable model curves, stop sending spread spectrum signals to the same end of the cable under test; M is the number threshold.

3. A cable detection method according to claim 2, characterized in that, The calculating the terminal position, damage position, and cable aging degree of the damaged cable based on the obtained cable model curve includes: Among the M cable model curves, select the second to the Mth cable model curves C2...C m , and apply the decision algorithm to screen the second to the Mth cable model curves C2...C m to select the cable model curves whose terminal peak values are lower than the threshold; Using a fusion algorithm to merge the selected cable model curves into a final cable model curve Cout; Calculating the terminal position, damage position, and cable aging degree of the damaged cable using the final cable model curve Cout.

4. A cable detection method according to claim 3, characterized in that, The calculating the terminal position, damage position, and cable aging degree of the damaged cable using the final cable model curve Cout includes: The terminal position of the cable is: the highest peak position of Cout × the propagation factor of the cable under test under different parameter signals; The damage position of the cable is: other small peak positions of Cout × the propagation factor of the cable under test under different parameter signals; The cable aging degree Ac is: Ac = Yc × K2 Where Ac = Yc × K2, K2 is a preset aging correction factor, and Yc is the average value or maximum value of the peak amplitudes of other small peaks of Cout.

5. A cable detection method according to claim 1, characterized in that, After receiving the reflected signal at the same end of the cable under test each time, applying a filtering algorithm to filter out the initial reflected signal, and then converting the reflected signal into a first cable model curve through a spread spectrum signal receiving algorithm.

6. A cable detection method according to claim 5, characterized in that The filtering algorithm is: using coherent demodulation to extract the delay signal.

7. A cable detection method according to claim 1, characterized in that The parameters of the spread spectrum signal include: Carrier frequency fi, pseudo-spread spectrum code frequency fcn, pseudo-spread spectrum code pattern Dn, pseudo-spread spectrum code length Ln; where n is a natural number from 1 to N, and N is the number of groups of pseudo-spread spectrum codes.

8. A cable detection device for performing the method according to claim 1, characterized in that, Including: A signal sending module for repeatedly sending spread spectrum signals with different parameter settings to one end of the cable under test; A signal receiving module for simultaneously receiving reflected signals at the same end of the cable under test; A signal analysis module, which is used to convert the reflected signal into a first cable model curve through a spread-spectrum signal receiving algorithm every time a reflected signal is obtained, compare the first cable model curve with a reference model curve Crf, and obtain a comparison difference; the reference model curve Crf is a cable model curve when it is set that the cable has no damage. If the comparison difference cannot be zero, it is determined that the cable is damaged. Based on the obtained cable model curve, calculate the terminal position, damage position, and cable aging degree of the damaged cable.

9. A cable detection device according to claim 8, characterized in that, It further includes: A signal generation module, which is used to generate a standard test vector. The signal sending module converts the standard test vector into an analog signal Sa1 and outputs the analog signal Sa1 as a spread-spectrum signal to one end of the cable under test.

10. A cable detection device according to claim 9, characterized in that, When the cable under test is not disconnected from the external device: The signal analysis module also adjusts the test parameters according to the result analyzed by it, outputs the new test parameters to the signal generation module through feedback information, and is used for the signal generation module to adjust the test vector according to the new parameters for a new round of testing. The signal analysis module obtains the model curve of the final cable aging state according to the comparison and selection algorithm based on the results of multiple rounds of testing.

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