A method and system for proximity defect detection of an instrumented cable

Abstract

The present application relates to a kind of instrument control cable short-range defect detection method and system, comprising: determining the cable core of instrument control cable to be measured;To the cable core to be measured input incident signal;Receive incident signal;Judge whether the reflection signal generated based on incident signal of the cable core to be measured is received;If yes, the incident signal and the reflection signal are preprocessed, obtain the preprocessing signal of incident signal and the preprocessing signal of reflection signal;Multiple time-frequency domain analysis is carried out based on the preprocessing signal of incident signal and the preprocessing signal of reflection signal, and normalized time-frequency domain analysis result is obtained;According to the normalized time-frequency domain analysis result, the cable core to be measured is defect detected.The present application can carry out multiple time-frequency domain analysis by changing time-frequency analysis algorithm, dynamically adjust integral interval, so as to judge whether there is the defect caused by multiple wave peak overlapping, effectively detect and distinguish two similar defects, remove measurement blind area, improve the precision of cable defect detection.

Description

Technical Field

[0001] This invention relates to the technical field of power engineering, and more specifically, to a method and system for close-range defect detection of instrumentation and control cables. Background Technology

[0002] Instrumentation and control cables, which monitor the operational information of critical equipment in nuclear power plants and the operation of key equipment within the control station and even the containment, are a crucial link in ensuring the safe operation of nuclear power plants. Because instrumentation and control cables are typically located in the harsh environment of the containment, factors such as cable compression, abrasion from sharp external components, high temperatures, strong chemical corrosion, and nuclear radiation can significantly damage the outer sheath, insulation, and inner core of the cables. While common single defects can be detected using conventional traveling wave methods, low-probability multiple defects that are close together often appear as single-reflection signals and cannot be detected by conventional methods, resulting in a high location error rate. Treating multiple defects as single defects leaves safety hazards at the defect locations, potentially leading to safety accidents in the long term and posing a serious threat to the safe and stable operation of large electrical and control systems, as well as the lives of maintenance personnel. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method and system for close-range defect detection of instrumentation cables.

[0004] The technical solution adopted by this invention to solve its technical problem is: to construct a method for close-range defect detection of instrumentation cables, comprising the following steps:

[0005] Identify the core of the instrument control cable to be tested;

[0006] An incident signal is input to the cable core under test;

[0007] Receive the incident signal;

[0008] Determine whether a reflected signal generated by the cable core under test based on the incident signal is received;

[0009] If so, the incident signal and the reflected signal are preprocessed to obtain a preprocessed signal for the incident signal and a preprocessed signal for the reflected signal;

[0010] Multiple time-frequency domain analyses are performed based on the preprocessed signals of the incident signal and the preprocessed signals of the reflected signal to obtain normalized time-frequency domain analysis results.

[0011] Defect detection is performed on the cable core under test based on the normalized time-frequency domain analysis results.

[0012] In the near-field defect detection method for instrumentation cables described in this embodiment of the invention, the step of performing multiple time-frequency domain analysis based on the preprocessed signal of the incident signal and the preprocessed signal of the reflected signal to obtain normalized time-frequency domain analysis results includes:

[0013] Based on the preprocessed signals of the incident signal and the reflection signal, a cyclic algorithm is used to dynamically adjust the integration interval.

[0014] Multiple time-frequency domain analyses are performed based on the dynamically adjusted integration interval to obtain the time-frequency distribution of the incident signal and the time-frequency distribution of the reflected signal;

[0015] The time-frequency distributions of the incident signal and the reflected signal are normalized to obtain the normalized time-frequency domain analysis results.

[0016] In the near-field defect detection method for instrumentation cables described in this embodiment of the invention, the defect detection of the cable core under test based on the normalized time-frequency domain analysis results includes:

[0017] Obtain the reflection peak value from the normalized time-frequency domain analysis results;

[0018] Defect detection is performed on the cable core under test based on the reflection peak value.

[0019] In the near-range defect detection method for instrumentation cables described in this embodiment of the invention, the defect detection of the cable core under test based on the reflection peak value includes:

[0020] The reflection peak value is compared with a preset peak value;

[0021] Determine whether the reflection peak value is greater than or equal to the preset peak value;

[0022] If so, then it is determined that the cable core under test has a defect;

[0023] If not, then the cable core under test is determined to be without defects.

[0024] In the near-range defect detection method for instrumentation cables described in this embodiment of the invention, the defect detection of the cable core under test based on the reflection peak value further includes:

[0025] If the cable core under test has a defect, the defect peak value in the cable core under test is obtained; the defect peak value is the reflection peak value that is greater than or equal to the preset peak value.

[0026] Obtain the reference peak value in the incident signal that corresponds to the peak value of the defect;

[0027] The location of the defect in the cable core under test is determined based on the time difference between the reference peak value and the defect peak value.

[0028] The present invention also provides a near-field defect detection system for instrumentation cables, comprising: a signal generation unit, a signal processing unit, a multi-time-frequency domain analysis unit, and a defect detection unit;

[0029] The signal generation unit is used to generate the incident signal;

[0030] The signal processing unit is connected to the signal generating unit and the instrument control cable respectively. The signal processing unit is used to receive the reflected signal generated by the cable core under test of the instrument control cable and the incident signal generated by the signal generating unit, and to preprocess the incident signal and the reflected signal to obtain the preprocessed signal of the incident signal and the preprocessed signal of the reflected signal.

[0031] The multiple time-frequency domain analysis unit is used to perform multiple time-frequency domain analysis based on the preprocessed signal of the incident signal and the preprocessed signal of the reflected signal to obtain normalized time-frequency domain analysis results.

[0032] The defect detection unit is used to detect defects in the cable core under test based on the normalized time-frequency domain analysis results.

[0033] The near-field defect detection system for instrument control cables described in this embodiment of the invention further includes: a switching unit;

[0034] The switching unit is disposed between the signal processing unit and the beginning of the instrumentation cable and connected to the signal generating unit, and is used to control the connection and disconnection between the signal processing unit and the instrumentation cable, as well as the connection and disconnection between the signal generating unit and the instrumentation cable.

[0035] In the near-field defect detection system for instrument-controlled cables according to the embodiments of the present invention, the switching unit includes: a plurality of series switches corresponding to the cable cores of the instrument-controlled cable, each series switch being used to control the connection and disconnection between its corresponding cable core and the signal generation unit and the signal processing unit.

[0036] The near-field defect detection system for instrument-controlled cables described in this embodiment of the invention further includes: a control unit;

[0037] The control unit is connected to the switch unit, and the control unit is used to control the switch unit to be connected or disconnected.

[0038] In the near-field defect detection system for instrument control cables described in this embodiment of the invention, the incident signal is a linear frequency modulated signal with a Gaussian envelope.

[0039] The method and system for near-range defect detection of instrument-controlled cables according to the present invention have the following beneficial effects: It includes: identifying the cable core to be tested in the instrument-controlled cable; inputting an incident signal to the cable core to be tested; receiving the incident signal; determining whether a reflected signal generated by the cable core to be tested based on the incident signal is received; if so, preprocessing the incident signal and the reflected signal to obtain preprocessed signals for the incident signal and the reflected signal; performing multiple time-frequency domain analysis based on the preprocessed signals for the incident signal and the reflected signal to obtain normalized time-frequency domain analysis results; and performing defect detection on the cable core to be tested based on the normalized time-frequency domain analysis results. The present invention can dynamically adjust the integration interval by changing the time-frequency analysis algorithm to perform multiple time-frequency domain analysis, thereby determining whether there are defects caused by multiple overlapping peaks, effectively detecting and distinguishing two close defects, eliminating measurement blind spots, and improving the accuracy of cable defect detection. Attached Figure Description

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0041] Figure 1 This is a flowchart illustrating the method for detecting near-field defects in instrumentation cables provided in an embodiment of the present invention;

[0042] Figure 2 This is a time-frequency cross-correlation result diagram provided in an embodiment of the present invention;

[0043] Figure 3 This is a schematic diagram of the structure of the instrumentation cable near-field defect detection system provided in an embodiment of the present invention. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Figure 1 This invention illustrates a method for close-range defect detection in instrumentation and control cables, which can perform defect detection on multi-core cables. Specifically, this method is based on time-frequency domain reflectometry.

[0046] Specifically, the working principle of the time-frequency domain reflection method is as follows: When an electromagnetic wave signal travels through a conductor and encounters a point of impedance discontinuity, reflection and refraction occur. A peak value appears at the defect point in the collected reflected wave. The defect location can then be calculated based on the time difference between this peak value and the peak value of the incident signal. Therefore, when a signal is emitted from one end of the cable core, the oscilloscope receives the incident signal at that end. At the other end of the cable core, the incident signal undergoes total reflection, and the oscilloscope receives the totally reflected signal at that end. However, if two defects are close together, the reflections caused by the defects will overlap, forming a single peak, causing the defect to be ignored and undetectable. To avoid this, the present invention provides a method for detecting near-field defects in instrumentation and control cables. This method can effectively achieve comprehensive detection of all cable cores within the instrumentation and control cable, eliminating measurement blind spots and thus significantly improving the accuracy of cable core defect detection.

[0047] like Figure 1 As shown, in this embodiment, the method for detecting near-field defects in the instrument control cable includes the following steps:

[0048] Step S101: Determine the core of the instrument control cable to be tested.

[0049] In this step, the determination of the cable core to be tested in the instrument control cable can be carried out in any existing way, and the present invention does not make any specific limitation.

[0050] Specifically, when defect detection is required on instrumentation cables, since a single instrumentation cable contains multiple cores, the first step is to identify the core to be tested, and then input an incident signal to that core. Of course, this step can be omitted when the instrumentation cable is a single-core cable.

[0051] Step S102: Input the incident signal into the cable core to be tested.

[0052] In this embodiment, the incident signal is a linear frequency modulated (LFM) signal with a Gaussian envelope. Since LFM signals with a Gaussian envelope possess certain anti-interference capabilities and good time-domain analyzability, the incident signal in this invention uses an LFM signal with a Gaussian envelope, thereby improving the anti-interference capabilities and time-domain performance of the signal analysis.

[0053] Step S103: Receive the incident signal.

[0054] In this embodiment, while inputting the incident signal to the cable core under test in step S102, the incident signal is also sent to the signal processing unit 12.

[0055] Step S104: Determine whether the reflected signal generated by the cable core under test based on the incident signal is received.

[0056] Specifically, after receiving the incident signal, the signal processing unit 12 also needs to monitor whether it receives the reflected signal generated by the incident signal at the end of the cable core under test.

[0057] In this embodiment, when an incident signal is input to the cable core under test, the incident signal is transmitted from the input end (set as the head end) of the cable core under test to the end end of the cable core under test, and undergoes total reflection at the end end of the cable core under test. The generated total reflection signal is transmitted back from the cable core under test to the head end and transmitted to the signal receiving unit, where it is received by the signal processing unit 12.

[0058] Step S105: If yes, preprocess the incident signal and the reflected signal to obtain the preprocessed signal of the incident signal and the preprocessed signal of the reflected signal.

[0059] In this embodiment, the preprocessed signal of the incident signal is a digital signal. Similarly, the preprocessed signal of the reflected signal is a digital signal. Specifically, after receiving the incident signal, the signal processing unit 12 performs conversion processing on the incident signal to output the corresponding digital signal. After receiving the reflected signal, the signal processing unit 12 performs conversion processing on the reflected signal to output the corresponding digital signal.

[0060] Step S106: Perform multiple time-frequency domain analysis based on the preprocessed signals of the incident signal and the preprocessed signals of the reflected signal to obtain normalized time-frequency domain analysis results.

[0061] In this embodiment, multiple time-frequency domain analyses are performed based on the preprocessed signals of the incident signal and the preprocessed signals of the reflected signal to obtain normalized time-frequency domain analysis results. This includes: dynamically adjusting the integration interval using a cyclic algorithm based on the preprocessed signals of the incident signal and the preprocessed signals of the reflected signal; performing multiple time-frequency domain analyses based on the dynamically adjusted integration interval to obtain the time-frequency distribution of the incident signal and the time-frequency distribution of the reflected signal; and normalizing the time-frequency distribution of the incident signal and the time-frequency distribution of the reflected signal to obtain normalized time-frequency domain analysis results.

[0062] In this embodiment, the integration interval can be dynamically adjusted through a cyclic algorithm to perform multiple time-frequency domain analyses, and finally the time-frequency domain analysis results of multiple peaks can be normalized.

[0063] Specifically, the input incident signal expression for the traditional Time-Frequency Domain Reflectometer (TFDR) is:

[0064]

[0065] (1) In the formula, s(t) is the functional expression of the incident signal; (α / π) 1 / 4Let be the peak amplitude of the signal, exp[-α(t-t0)]. 2 / 2)] represents the Gaussian window portion, exp[jβ(t-t0)] 2 [ / 2+jω0(t-t0)] represents the linear frequency modulation part; α is the width factor of the Gaussian distribution, and β is the time coefficient of the frequency growth rate. Together, they determine the duration T of the signal. s and frequency bandwidth B s ; t0 and ω0 represent the time center and frequency center of the signal, respectively.

[0066] Traditional TFDR performs time-frequency domain analysis on the digital signals of the incident and reflected signals, first performing a Wigner transform on both signals. This Wigner transform can be performed using the following formula:

[0067]

[0068] (2) In the formula, D(t,ω) represents the time-frequency distribution function of the signal, t represents the time position, ω represents the frequency, s represents the incident signal, s* is the conjugate function of the incident signal, τ is the integration variable, j represents the imaginary unit, and π represents pi.

[0069] That is, the traditional time-frequency analysis method uses Equation (2) to perform Wigner transform on the incident signal and the reflected signal to obtain the corresponding time-frequency distribution (time-frequency distribution of the incident signal and time-frequency distribution of the reflected signal), and then performs time-frequency cross-correlation normalization on the time-frequency distribution of the incident signal and the time-frequency distribution of the reflected signal. The time-frequency cross-correlation normalization function (TFCC) is shown in Equation (3).

[0070]

[0071] (2) In the formula, C sr (τ) represents the time-frequency cross-correlation function between signals, and E(x) is the time-frequency domain energy of the signal. The subscripts s and r represent the incident signal and the reflected signal, respectively. D(t,ω) is the time-frequency distribution function, where the subscripts s and r represent the incident and reflected signals, respectively. s D represents the duration of the signal, where τ is the integral variable; s (t-τ,ω) represents the time-frequency distribution function when the incident signal moves τ units in time.

[0072] In traditional time-frequency analysis methods, the final time-frequency analysis result can be obtained through equations (2) and (3). However, when there are defects at close range, they cannot be detected by traditional time-frequency analysis methods. Therefore, this invention uses a cyclic algorithm to dynamically adjust the integration interval and performs multiple time-frequency domain analyses based on the dynamically adjusted integration interval, which can achieve the detection of defects at close range.

[0073] Specifically, in this embodiment, by changing E in the time-frequency cross-correlation normalization function r The integration interval, i.e., changing the selected energy range of the reflected signal, is helpful in reducing the lobe width of the TFCC positioning peak. The upper and lower limits of the integration with respect to time in the original formula (3) are τ+Ts and τ-Ts, respectively, where T s Let the duration of the incident signal be half of the total duration. The modified upper and lower limits of integration are now set to τ+Ts and τ-Ts, respectively, where Ty is a predetermined time length, with a value of the same order of magnitude as Ts. The modified formula is:

[0074]

[0075] Using a loop algorithm, from T y =T s Initially, T was continuously adjusted. y / T s The value is decreased in steps of 0.05. By comparing the peak values ​​of each new time-frequency cross-correlation result with the old time-frequency cross-correlation results, it is determined whether each peak is composed of two or more reflected waves. Finally, when T y / T s When the value is 0.65, a final time-frequency cross-correlation is performed, and the result is normalized to obtain the final time-frequency analysis result. When the peak consists of two reflected waves, it can be seen that dynamically adjusting T... y / T s The value can effectively achieve peak separation; please refer to [reference needed]. Figure 2 .

[0076] Depend on Figure 2 As can be seen, when T y =T s At that time, the peak on the horizontal axis at 950 ns was almost invisible, and this was achieved by gradually adjusting T. y / T s After obtaining the numerical values, the peak corresponding to the horizontal axis at 950 ns appeared, achieving separation from the peak at 700 ns. Finally, the algorithm system integrated and judged to give the final time-frequency analysis result, realizing the separation of similar defects and improving the accuracy of defect detection.

[0077] Step S107: Perform defect detection on the cable core under test based on the normalized time-frequency domain analysis results.

[0078] In this embodiment, defect detection of the cable core under test based on the normalized time-frequency domain analysis results includes: obtaining the reflection peak value in the normalized time-frequency domain analysis results; and performing defect detection on the cable core under test based on the reflection peak value. Specifically, performing defect detection on the cable core under test based on the reflection peak value includes: comparing the reflection peak value with a preset peak value; determining whether the reflection peak value is greater than or equal to the preset peak value; if yes, determining that the cable core under test has a defect; if no, determining that the cable core under test has no defect.

[0079] In this embodiment, defect detection of the cable core under test based on the reflection peak value further includes: if there is a defect in the cable core under test, obtaining the defect peak value in the cable core under test; the defect peak value is the reflection peak value that is greater than or equal to a preset peak value; obtaining the reference peak value in the incident signal corresponding to the defect peak value; and determining the defect location of the cable core under test based on the time difference between the reference peak value and the defect peak value.

[0080] Figure 3 This invention illustrates a near-field defect detection system for instrumentation cables.

[0081] like Figure 3 As shown, the near-field defect detection system for the instrument control cable includes: a signal generation unit 11, a signal processing unit 12, a multi-time-frequency domain analysis unit 13, and a defect detection unit 14.

[0082] The signal generation unit 11 is used to generate an incident signal; the signal processing unit 12 is connected to the signal generation unit 11 and the instrument control cable respectively, and the signal processing unit 12 is used to receive the reflected signal generated by the cable core under test of the instrument control cable and the incident signal generated by the signal generation unit 11, and preprocess the incident signal and the reflected signal to obtain the preprocessed signal of the incident signal and the preprocessed signal of the reflected signal; the multiple time-frequency domain analysis unit 13 is used to perform multiple time-frequency domain analysis based on the preprocessed signal of the incident signal and the preprocessed signal of the reflected signal to obtain the normalized time-frequency domain analysis result; the defect detection unit 14 is used to perform defect detection on the cable core under test according to the normalized time-frequency domain analysis result.

[0083] Furthermore, in this embodiment, as Figure 3 As shown, the near-field defect detection system for the instrument control cable also includes a switch unit 15. The switch unit 15 is disposed between the signal processing unit 12 and the beginning of the instrument control cable and is connected to the signal generation unit 11. It is used to control the connection and disconnection between the signal processing unit 12 and the instrument control cable, as well as the connection and disconnection between the signal generation unit 11 and the instrument control cable.

[0084] Optionally, in this embodiment, the switching unit 15 includes: a plurality of series switches corresponding to the cable cores of the instrument control cable, each series switch being used to control the connection and disconnection between its corresponding cable core and the signal generation unit 11 and the signal processing unit 12.

[0085] Furthermore, in this embodiment, as Figure 3 As shown, the instrument control cable near-field defect detection system also includes: a control unit 16; the control unit 16 is connected to the switch unit 15, and the control unit 16 is used to control the switch unit 15 to be connected or disconnected.

[0086] Specifically, in this embodiment, as Figure 2 As shown, the series switches can be implemented using electronic switches. The control unit 16 controls the on / off state of each series switch. By controlling the on / off state of the series switches at one end of the cable through the control unit 16, the cable core to be tested can be determined.

[0087] like Figure 2 As shown in this embodiment, each series switch in the switch unit 15 is marked with a number (or code), which is consistent with the number of the corresponding cable core, thereby realizing the association and one-to-one correspondence between the series switches and the cable cores.

[0088] Specifically, such as Figure 2 As shown, S0 is the first end of the multi-core cable 100, which includes five cable cores: X1, X2, X3, X4, and X5. Correspondingly, five series switches need to be installed, namely K11, K12, K13, K14, and K15.

[0089] like Figure 2 As shown, when defect detection is required on cable core X1, cable core X1 is the cable core to be tested. At the start of the test, control unit 16 controls K11 to close. Signal generation unit 11 inputs an incident signal to cable core X1 through K11, and this incident signal is also received by signal processing unit 12. This incident signal is transmitted through K11 to the beginning of cable core X1, and after being transmitted through cable core X1 to its end, it is reflected back along the same path and received by signal processing unit 12. Signal processing unit 12 then converts and processes the signal before sending it to multiple time-frequency domain analysis unit 13. Multiple time-frequency domain analysis unit 13 then analyzes and processes the signal before sending it to defect detection unit 14, completing the defect detection of cable core X1.

[0090] Similarly, the detection principle for defects in other cable cores is the same as that for cable core X1.

[0091] In this embodiment, the digital signals sent by the signal processing unit 12 to the multiple time-frequency domain analysis unit 13 are grouped, that is, each group of digital signals includes the incident data of the incident signal and the reflection data of the reflected signal corresponding to the incident signal.

[0092] Optionally, in this embodiment, the signal processing unit 12 can be an oscilloscope.

[0093] In this embodiment, the multiple time-frequency domain analysis unit 13 performs multiple time-frequency domain analyses on each received digital signal across different integration intervals to obtain normalized time-frequency domain analysis results. Specifically, the multiple time-frequency domain analysis unit 13 performs multiple time-frequency domain analyses on each set of incident data and the corresponding reflected data to obtain normalized time-frequency domain analysis results for each set of digital signals. This allows for defect detection of the corresponding cable core under test based on the normalized time-frequency domain analysis results.

[0094] In this embodiment, after receiving the normalized time-frequency domain analysis result output by the multi-weight time-frequency domain analysis unit, the defect detection unit 14 analyzes the obtained normalized time-frequency domain analysis result to obtain its position on the time axis. The peak value of the two signals is taken as the reference, and the distance between the two peak values ​​on the time axis is the time difference, also known as the peak time difference. Then, the defect location can be calculated using the wave velocity. Finally, based on the calculated defect location, peak time difference, and cable core number, it can be determined whether the cable core under test has a defect and to locate which specific cable core has a defect and its location.

[0095] It should be noted that the specific coordination and operation process between the units in the instrumentation and control cable close-range defect detection system can be referred to the above-mentioned instrumentation and control cable close-range defect detection method, and will not be repeated here.

[0096] For instrumentation and control cables in nuclear power plants that operate for extended periods, minor defects may develop due to various factors. When two defects are too close together, the reflected waves may overlap to form a new reflected wave, causing one defect to be overlooked and the other defect to be poorly located. This invention can determine whether there are multiple overlapping wave peaks that cause errors in the number of defects by changing the time-frequency analysis algorithm and dynamically adjusting the integration interval. This effectively detects and distinguishes two similar defects, thereby improving the accuracy of cable core defect detection.

[0097] For instrumentation and control cables that have been in operation for a long time in nuclear power plants, a series of defects may appear on the outside and inside the cables due to the harsh environment they are in, including nuclear radiation stress, temperature stress, chemical stress, and mechanical stress. While common single defects can be detected using the conventional traveling wave method, for low-probability multiple defects that are close together, conventional detection methods can only detect individual defects, resulting in relatively large location errors. Therefore, this invention improves the time-frequency cross-correlation algorithm in the time-frequency domain reflection method, enabling the differentiation and location of defects that are close together, thereby improving the reliability of safe operation of nuclear power plants.

[0098] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0099] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0100] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0101] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They do not limit the scope of protection of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A method for close-range defect detection of instrumentation and control cables, characterized in that, Includes the following steps: Identify the core of the instrument control cable to be tested; An incident signal is input to the cable core under test; Receive the incident signal; Determine whether the reflected signal generated by the cable core under test based on the incident signal is received; If so, the incident signal and the reflected signal are preprocessed to obtain a preprocessed signal for the incident signal and a preprocessed signal for the reflected signal; Multiple time-frequency domain analyses are performed based on the preprocessed signals of the incident signal and the preprocessed signals of the reflected signal to obtain normalized time-frequency domain analysis results. The preprocessed signals based on the incident signal and the reflected signal are subjected to multiple time-frequency domain analysis to obtain normalized time-frequency domain analysis results, including: Based on the preprocessed signals of the incident signal and the reflection signal, a cyclic algorithm is used to dynamically adjust the integration interval. Multiple time-frequency domain analyses are performed based on the dynamically adjusted integration interval to obtain the time-frequency distribution of the incident signal and the time-frequency distribution of the reflected signal; The time-frequency distribution of the incident signal and the time-frequency distribution of the reflected signal are normalized to obtain the normalized time-frequency domain analysis results; Defect detection is performed on the cable core under test based on the normalized time-frequency domain analysis results.

2. The method for close-range defect detection of instrumentation and control cables according to claim 1, characterized in that, The defect detection of the cable core under test based on the normalized time-frequency domain analysis results includes: Obtain the reflection peak value from the normalized time-frequency domain analysis results; Defect detection is performed on the cable core under test based on the reflection peak value.

3. The method for close-range defect detection of instrumentation and control cables according to claim 2, characterized in that, The defect detection of the cable core under test based on the reflection peak value includes: The reflection peak value is compared with a preset peak value; Determine whether the reflection peak value is greater than or equal to the preset peak value; If so, then it is determined that the cable core under test has a defect; If not, then the cable core under test is determined to be without defects.

4. The method for close-range defect detection of instrumentation and control cables according to claim 3, characterized in that, The defect detection of the cable core under test based on the reflection peak value also includes: If the cable core under test has a defect, the defect peak value in the cable core under test is obtained; the defect peak value is the reflection peak value that is greater than or equal to the preset peak value. Obtain the reference peak value in the incident signal that corresponds to the peak value of the defect; The location of the defect in the cable core under test is determined based on the time difference between the reference peak value and the defect peak value.

5. A near-field defect detection system for instrument control cables, characterized in that, include: Signal generation unit, signal processing unit, multiple time-frequency domain analysis unit, and defect detection unit; The signal generation unit is used to generate the incident signal; The signal processing unit is connected to the signal generating unit and the instrument control cable respectively. The signal processing unit is used to receive the reflected signal generated by the cable core under test of the instrument control cable and the incident signal generated by the signal generating unit, and to preprocess the incident signal and the reflected signal to obtain the preprocessed signal of the incident signal and the preprocessed signal of the reflected signal. The multiple time-frequency domain analysis unit is used to perform multiple time-frequency domain analysis based on the preprocessed signal of the incident signal and the preprocessed signal of the reflected signal to obtain normalized time-frequency domain analysis results. The preprocessed signals based on the incident signal and the reflected signal are subjected to multiple time-frequency domain analysis to obtain normalized time-frequency domain analysis results, including: Based on the preprocessed signals of the incident signal and the reflection signal, a cyclic algorithm is used to dynamically adjust the integration interval. Multiple time-frequency domain analyses are performed based on the dynamically adjusted integration interval to obtain the time-frequency distribution of the incident signal and the time-frequency distribution of the reflected signal; The time-frequency distribution of the incident signal and the time-frequency distribution of the reflected signal are normalized to obtain the normalized time-frequency domain analysis results; The defect detection unit is used to detect defects in the cable core under test based on the normalized time-frequency domain analysis results.

6. The near-field defect detection system for instrument control cables according to claim 5, characterized in that, Also includes: Switching unit; The switching unit is disposed between the signal processing unit and the beginning of the instrumentation cable, and is connected to the signal generating unit, for controlling the connection and disconnection between the signal processing unit and the instrumentation cable, as well as the connection and disconnection between the signal generating unit and the instrumentation cable.

7. The near-field defect detection system for instrument control cables according to claim 6, characterized in that, The switching unit includes a plurality of series switches corresponding to the cable cores of the instrumentation cable, each series switch being used to control the connection and disconnection between its corresponding cable core and the signal generation unit and the signal processing unit.

8. The near-field defect detection system for instrument control cables according to claim 6, characterized in that, Also includes: Control unit; The control unit is connected to the switch unit, and the control unit is used to control the switch unit to be connected or disconnected.

9. The near-field defect detection system for instrument control cables according to claim 5, characterized in that, The incident signal is a linear frequency modulated signal with a Gaussian envelope.

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