Power cable defect time-domain diagnosis method and apparatus based on cross-bonding box structure

Abstract

The present application relates to the technical field of high voltage, and in particular, to a power cable defect time-domain diagnosis method and apparatus based on a cross-bonding box structure. The method comprises: injecting a broadband signal on the basis of crossed wiring terminals of three-phase shielding layers of cross-bonding boxes, so as to collect initial voltage time-domain waveforms of three-phase cables to be monitored, when in a steady state, generated on the basis of the broadband signal; preprocessing the initial voltage time-domain waveforms at the same end to respectively obtain preprocessed voltage time-domain waveforms at the left and right ends of the cross-bonding boxes; and diagnosing defects in outer sheathes and main insulators of said three-phase cables on the basis of the voltage time-domain waveforms at the left and right ends, so as to obtain a final defect time-domain diagnosis result of said three-phase cables. Therefore, the technical problems in the related art that the core of an exposed cable in a power cable system is broken, resulting in damage to the complete topological structure of the power cable system and making online monitoring difficult, field device requirements are increased, leading to high inspection complexity and cost, the practicability is low and the like are solved.

Description

Time domain diagnosis method and device for power cable defects based on cross-connection box structure

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application number "202410426699.1" filed by Tsinghua University on April 10, 2024, entitled "Time domain diagnosis method and device for power cable defects based on cross-connected box structure". Technical Field

[0003] The present application relates to the field of high voltage technology, and in particular to a method and device for time-domain diagnosis of power cable defects based on a cross-connection box structure. Background Art

[0004] Power cables are widely used in various industries, including power systems, urban rail transit, petrochemicals, and metallurgy, and are one of the important equipment for transmitting and distributing electric energy. A cross-connection system is a common design in three-phase power cables, aimed at balancing the capacitance between phases, reducing interphase interference, and improving the transmission capacity and stability of power cables. However, since power cables are buried underground for long periods of time and are affected by various environmental factors, such as temperature, humidity, and chemical corrosion, as well as defects in the manufacturing process, various faults may occur during use, potentially disrupting the balance of the cross-connection system and causing changes in the capacitance value of the faulty phase, seriously affecting the normal operation of the power cable and more likely causing power supply interruptions, bringing great inconvenience to people's production and life.

[0005] In related technologies, commonly used fault location methods include the bridge method and the pulse reflection method. Among them, the bridge method mainly utilizes the linear relationship between the length and resistance of the faulty power cable, and the power cable core resistance and proportional resistance on both sides of the fault point form a bridge; while the pulse reflection method is to send a pulse signal to the power cable. According to the principle that the pulse signal will generate electromagnetic wave reflection when encountering a wave impedance mismatch point when propagating in the power cable line, by analyzing the characteristics of the reflected signal, it can be determined whether there is a fault in the power cable and the location of the fault.

[0006] However, in the related art, the detection signal is injected into the power cable system to be tested, causing the core wires of the exposed cables in the power cable system to be disconnected, thereby destroying the complete topology structure of the power cable system, making it difficult to achieve online monitoring, increasing the demand for on-site equipment, and the complexity and cost of inspections are high. It is not suitable for daily diagnosis of power cable systems, has low practicality, and urgently needs improvement.

[0007] Summary of the Invention

[0008] The application provides a time domain diagnosis method and device for defects of power cables based on a cross-interconnected box structure, to solve the technical problems in the prior art that the core wire of the cable at the exposed part in the power cable system is disconnected, the complete topology structure of the power cable system is damaged, it is difficult to monitor online, the demand for on-site equipment is increased, the complexity and cost of inspection are high, and the practicability is low.

[0009] The first aspect of the application provides a time domain diagnosis method for defects of power cables based on a cross-interconnected box structure, comprising the following steps: injecting a wideband signal into the wiring terminal of the three-phase shielding layer cross of the cross-interconnected box, to collect the initial voltage time domain waveform of the steady state of the three-phase cable to be tested based on the wideband signal; preprocessing the initial voltage time domain waveform of the same end to obtain the voltage time domain waveforms of the left and right ends of the cross-interconnected box after preprocessing respectively; diagnosing the defects existing in the outer sheath and the main insulation in the three-phase cable to be tested based on the voltage time domain waveforms of the left and right ends, to obtain the final defect time domain diagnosis result of the three-phase cable to be tested.

[0010] Optionally, in one embodiment of the application, the preprocessing of the initial voltage time domain waveform of the same end to obtain the voltage time domain waveforms of the left and right ends of the cross-interconnected box after preprocessing respectively comprises: performing discrete wavelet transform on the initial voltage time domain waveform respectively based on the initial voltage time domain waveform, and filtering the initial voltage time domain waveform after the discrete wavelet transform by using a hard threshold value, to obtain the voltage time domain waveform.

[0011] Optionally, in one embodiment of the application, the hard threshold value method can be:

[0012] Wherein, k δ is the wavelet transform coefficient processed according to the hard threshold value method, ψ a,b (t) is the wavelet transform coefficient, and δ is the set hard threshold value, wherein the expression of the hard threshold value can be:

[0013] Wherein, m is the median of the signal decomposition layer, and n is the length of the signal decomposition layer.

[0014] Optionally, in one embodiment of the application, the diagnosis of the defects existing in the outer sheath and the main insulation in the three-phase cable to be tested based on the voltage time domain waveforms of the left and right ends to obtain the final defect time domain diagnosis result of the three-phase cable to be tested comprises: determining the phase where the defect is located according to the voltage time domain waveform; and determining the position and direction of the defect according to the voltage time domain waveform.

[0015] Optionally, in one embodiment of the application, the absolute value of the position of the defect can be:

[0016] wherein, t ki is the time corresponding to the kth pole point with the absolute value of the amplitude greater than p in the ith test voltage waveform, T 1i is the time corresponding to the injection of the mismatch point in the ith test voltage data, T 2i is the time corresponding to the system mismatch point in the ith test voltage data, k is the label of the pole point, i is the label of the test voltage, L0 is the spacing between the cross-connection boxes.

[0017] The second aspect embodiment of the present application provides a power cable defect time domain diagnosis device based on a cross-connection box structure, comprising: an acquisition module configured to inject a wideband signal based on the cross-connection terminals of the three-phase shielding layer of the cross-connection box to acquire an initial voltage time domain waveform of a steady state of a three-phase cable to be tested based on the wideband signal; a preprocessing module configured to preprocess the initial voltage time domain waveform at the same end to obtain voltage time domain waveforms at the left and right ends of the cross-connection box after preprocessing; and a diagnosis module configured to diagnose defects existing in the outer sheath and the main insulation in the three-phase cable to be tested based on the voltage time domain waveforms at the left and right ends to obtain a final defect time domain diagnosis result of the three-phase cable to be tested.

[0018] Optionally, in an embodiment of the present application, the preprocessing module comprises a generation unit configured to perform discrete wavelet transform based on the initial voltage time domain waveform respectively, and filter the initial voltage time domain waveform after the discrete wavelet transform by using a hard threshold value to obtain the voltage time domain waveform.

[0019] Optionally, in an embodiment of the present application, the hard threshold value method can be:

[0020] wherein, k δ is the wavelet transform coefficient after processing according to the hard threshold value method, ψ a,b (t) is the wavelet transform coefficient, and δ is the set hard threshold value, wherein the expression of the hard threshold value can be:

[0021] wherein, m is the median of the signal decomposition layer, and n is the length of the signal decomposition layer.

[0022] Optionally, in an embodiment of the present application, the diagnosis module comprises a first determination unit configured to determine the phase where the defect is located according to the voltage time domain waveform, and a second determination unit configured to determine the position and direction where the defect is located according to the voltage time domain waveform.

[0023] Optionally, in an embodiment of the present application, the absolute value of the position where the defect is located can be:

[0024] wherein, t ki is the time corresponding to the kth pole with the absolute value of the amplitude greater than p in the ith test voltage waveform, T 1i is the time corresponding to the injected mismatch point in the ith test voltage data, T 2i is the time corresponding to the system mismatch point in the ith test voltage data, k is the label of the pole, i is the label of the test voltage, L0 is the spacing between the cross-connection boxes.

[0025] The third aspect of the present application provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the time-domain diagnosis method for defects of power cable based on the cross-connection box structure as described in the above embodiments.

[0026] The fourth aspect of the present application provides a computer-readable storage medium, which stores a computer program executable by a processor to implement the time-domain diagnosis method for defects of power cable based on the cross-connection box structure as described above.

[0027] The fifth aspect of the present application provides a computer program product comprising a computer program executable to implement the time-domain diagnosis method for defects of power cable based on the cross-connection box structure as described above.

[0028] The present application can inject a wideband signal through the cross-connection terminal of the three-phase shielding layer based on the cross-connection box, diagnose the time-domain diagnosis result of the defects existing in the outer sheath and the main insulation of the three-phase cable according to the voltage time-domain waveform generated in the steady state of the wideband signal, realize the simultaneous diagnosis of the hidden defects of the outer sheath and the main insulation of the three-phase cable and give the diagnosis positioning under the condition that the electrical connection of the three-phase cable system is not disconnected, and further realize the evaluation of the health status of the three-phase cable system, reduce the demand for on-site equipment and cost, improve the practicability, and thus make online monitoring possible. Therefore, the technical problems in the related art, such as the disconnection of the core wire of the exposed cable in the power cable system, the destruction of the complete topology structure of the power cable system, the difficulty in online monitoring, the high complexity and cost of the on-site equipment demand, and the low practicability are solved.

[0029] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0030] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the following description, taken in conjunction with the accompanying drawings, in which:

[0031] Fig. 1 is a structural schematic diagram of a constructed preset circuit according to an embodiment of the present application;

[0032] Fig. 2 is a flow chart of a power cable defect time domain diagnosis method based on a cross interconnection box structure according to an embodiment of the present application;

[0033] Fig. 3 is a block schematic diagram of working principle of a power cable defect time domain diagnosis method based on a cross interconnection box structure according to an embodiment of the present application;

[0034] Fig. 4 is a block schematic diagram of a power cable defect time domain diagnosis device based on a cross interconnection box structure according to an embodiment of the present application;

[0035] Fig. 5 is a structural schematic diagram of an electronic device according to an embodiment of the present application.

[0036] Among them, 201-waveform generating device, 202-signal acquisition device, 203-T-shaped connector, 204-signal connection cable, 2041-first cable segment, 2042-second cable segment, 205-uninterrupted in-service three-phase cable to be tested, 206-cross interconnection box of adjacent segments; 10-power cable defect time domain diagnosis device based on a cross interconnection box structure; 100-acquisition module, 200-preprocessing module, 300-diagnosis module; 501-memory, 502-processor, 503-communication interface. DETAILED DESCRIPTION

[0037] The embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar notations represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0038] A method and device for diagnosing defects in a power cable based on a cross-interconnected box structure are described below with reference to the accompanying drawings. In view of the fact that the core wires of the exposed cable in the power cable system are disconnected, the complete topology of the power cable system is damaged, it is difficult to monitor online, the demand for on-site equipment is increased, and the complexity and cost of inspection are high, the practicality is low, a method for diagnosing defects in a power cable based on a cross-interconnected box structure is provided. In the method, a wideband signal can be injected through the wiring terminal based on the cross of the three-phase shielding layer of the cross-interconnected box. The defect time domain diagnosis result existing in the outer sheath and the main insulation of the three-phase cable can be diagnosed according to the voltage time domain waveform generated by the wideband signal in the steady state. The hidden defects of the outer sheath and the main insulation of the three-phase cable are diagnosed and the diagnosis positioning is given under the condition that the electrical connection of the three-phase cable system is not disconnected. The health status of the three-phase cable system is evaluated. The demand for on-site equipment and cost are reduced. The practicality is improved. Online monitoring is possible. Thus, the technical problems such as the core wires of the exposed cable in the power cable system being disconnected, the complete topology of the power cable system being damaged, the difficulty in online monitoring, the increased demand for on-site equipment, the high complexity and cost of inspection, and the low practicality are solved.

[0039] Before the method for diagnosing defects in a power cable based on a cross-interconnected box structure provided by the embodiments of the present application is explained, the constructed preset circuit involved in the embodiments of the present application is exemplified.

[0040] Specifically, FIG. 1 is a structural schematic diagram of a constructed preset circuit according to the embodiments of the present application.

[0041] As shown in FIG. 1, 201 is a waveform generating device, 202 is a signal collecting device, 203 is a T-shaped connector, 204 is a signal connecting cable, 205 is a three-phase cable under test in service without disconnection, and 206 is a cross-interconnected box of adjacent sections.

[0042] Specifically, the waveform generating device 201 can be a waveform generator with good impedance matching between the internal resistance and the signal connecting cable.

[0043] The signal collecting device 202 can be selected to have as large an input resistance as possible, so as to be approximately in an open circuit state.

[0044] The signal connecting cable 204 can include a first cable section 2041 and a second cable section 2042.

[0045] In addition, the embodiments of the present application can use two adjacent cross-interconnected boxes 206 to collect the initial voltage time domain waveform generated by the three-phase cable 205 in the steady state.

[0046] Specifically, FIG. 2 is a flowchart of a power cable defect time domain diagnosis method based on a cross interconnection box structure according to an embodiment of the present application.

[0047] As shown in FIG. 2, the power cable defect time domain diagnosis method based on the cross interconnection box structure includes the following steps:

[0048] In step S201, a wideband signal is injected into the wiring terminal of the three-phase shielding layer cross of the cross interconnection box 206 to collect the initial voltage time domain waveform of the measured three-phase cable 205 in a steady state based on the wideband signal.

[0049] It can be understood that the measured three-phase cable 205 can be understood as a three-phase cable that has not been subjected to a disconnection process, and can be an in-service measured three-phase cable 205 or a non-in-service measured three-phase cable 205, which is not specifically limited by the present application.

[0050] In actual execution, the present embodiment can construct a preset loop, inject a wideband signal into the wiring terminal of the three-phase shielding layer cross of the cross interconnection box 206, and then collect the initial voltage time domain waveform of the measured three-phase cable 205 in a steady state.

[0051] In some embodiments, the present embodiment can take identifying hidden defects of the measured three-phase cable 205 in the M, N, and O sections as an example, and the constructed preset loop can be as shown in FIG. 1, and the process can be:

[0052] First, the preset loop is constructed and checked. That is, the present embodiment can construct the preset loop in the manner shown in FIG. 1, and after the preset loop is constructed, it is checked whether the connection is electrically reliable.

[0053] Then, the signal is output and collected. That is, the waveform generator of the present embodiment can output a wideband signal with a certain repetition frequency, and the signal collection device 202 can collect the port signal U0.

[0054] Next, the initial voltage time domain waveform of the measured three-phase cable 205 in the M-N section in a steady state is collected. Specifically, the present embodiment can connect the injection poles at the end of the second cable section 2042 to the a / a / b of the M-N section cross interconnection box 206, respectively, connect the return poles at the end of the second cable section 2042 to the c / b / c of the M-N section cross interconnection box 206, respectively, keep the settings of the waveform generator and the signal collection device 202, and collect the port signals U1, U2, and U3 in a single cycle in a steady state under this condition, respectively.

[0055] Further, the embodiment of the present application can also collect the initial voltage time-domain waveform of the N-O section of the three-phase cable 205 under steady state. Specifically, the embodiment of the present application can connect the injection poles at the end of the second cable section 2042 to a / a / b of the N-O section cross bonding box 206 respectively, connect the return poles at the end of the second cable section 2042 to c / b / c of the N-O section cross bonding box 206 respectively, keep the settings of the previous waveform generator and signal collection device 202, and collect the port signals U4, U5 and U6 in a single cycle under steady state in this case respectively.

[0056] In step S202, the same-end initial voltage time-domain waveform is preprocessed to obtain the voltage time-domain waveforms at the left and right ends of the cross bonding box 206 respectively.

[0057] It can be understood that the initial voltage time-domain waveform can contain noise and the like, and the embodiment of the present application can perform noise reduction and the like by preprocessing the initial voltage time-domain waveform.

[0058] As a possible implementation manner, the embodiment of the present application can preprocess the initial voltage time-domain waveforms at the same end respectively, and then obtain the preprocessed voltage time-domain waveforms at the left and right ends of the cross bonding box 206.

[0059] Optionally, in an embodiment of the present application, the same-end initial voltage time-domain waveform is preprocessed to obtain the voltage time-domain waveforms at the left and right ends of the cross bonding box 206 respectively, including: performing discrete wavelet transform on the initial voltage time-domain waveform respectively, and filtering the initial voltage time-domain waveform after the discrete wavelet transform by using a hard threshold value to obtain the voltage time-domain waveform. The hard threshold value method can be:

[0060] Wherein, k δ is the wavelet transform coefficient processed according to the hard threshold value method, ψ a,b (t) is the wavelet transform coefficient, and δ is the set hard threshold value, and the expression of the hard threshold value can be:

[0061] Wherein, m is the median of the signal decomposition layer, and n is the length of the signal decomposition layer.

[0062] In some embodiments, the embodiment of the present application can perform transformation by using discrete wavelet transform, and filter the collected initial voltage time-domain waveform by using the method of hard threshold value according to U1-U6 obtained in step S201, wherein the wavelet transform coefficient ψ a,b (t) can be expressed as:

[0063] Wherein, ψ is the wavelet base function.

[0064] Further, the embodiment of the present application can select a 5-layer decomposition number, and a hard threshold method is used to filter out noise, wherein the hard threshold method can be:

[0065] wherein k δ is the wavelet transform coefficient processed according to the hard threshold method, ψ a,b (t) is the wavelet transform coefficient, and δ is the set hard threshold, wherein the expression of the hard threshold can be:

[0066] wherein m is the median of the signal decomposition layer, and n is the length of the signal decomposition layer.

[0067] Further, the embodiment of the present application uses inverse wavelet transform on the filtered result to obtain the voltage time domain waveform after filtering out noise.

[0068] In step S203, based on the voltage time domain waveforms at the left and right ends, defects existing in the outer sheath and the main insulation of the three-phase cable 205 under test are diagnosed to obtain the final defect time domain diagnosis result of the three-phase cable 205 under test.

[0069] It can be understood that the outer sheath and the main insulation are important components of the three-phase cable 205 under test, and their integrity is crucial for the normal operation and safety of the three-phase cable 205 under test.

[0070] The outer sheath is the outermost protective layer of the three-phase cable 205 under test, and mainly avoids the influence of the external environment on the three-phase cable 205 under test, such as moisture, chemicals, mechanical damage, etc. If the outer sheath has defects such as damage, aging, cracks, etc., external moisture and chemicals may enter the inside of the cable, thereby causing damage to the main insulation layer and affecting normal operation.

[0071] The main insulation layer is an isolation layer between the internal conductor of the three-phase cable 205 under test and the external environment, mainly bearing the voltage during operation of the three-phase cable 205 under test, preventing current leakage and electric shock accidents. If the main insulation layer has defects such as bubbles, impurities, damage, etc., the insulation performance may be reduced, and breakdown or electric leakage may occur, and in severe cases, even fire or electric shock accidents may occur.

[0072] In actual execution process, the embodiment of the present application can use the voltage time domain waveform to diagnose the hidden defects existing in the outer sheath and the main insulation of the three-phase cable 205 under test, and further obtain the final defect time domain diagnosis result of the three-phase cable 205 under test.

[0073] Optionally, in one embodiment of the present application, based on the voltage time-domain waveforms at the left and right ends, defects existing in the outer sheath and the main insulation of the three-phase cable under test 205 are diagnosed, and the final defect time-domain diagnosis result of the three-phase cable under test 205 is obtained, including: determining the phase where the defect is located according to the voltage time-domain waveforms; and determining the position and direction where the defect is located according to the voltage time-domain waveforms. The absolute value of the position where the defect is located can be:

[0074] Wherein, t ki is the time corresponding to the kth pole point with an absolute value greater than p in the ith test voltage waveform, T 1i is the time corresponding to the mismatch point injected in the ith test voltage data, T 2i is the time corresponding to the system mismatch point in the ith test voltage data, k is the pole point label, i is the test voltage label, and L0 is the distance between the cross connection boxes.

[0075] As a possible implementation manner, the final defect time-domain diagnosis result of the three-phase cable under test 205 in the embodiment of the present application determines the phase where the defect is located on one hand, and determines the position and direction where the defect is located on the other hand.

[0076] Wherein, in the embodiment of the present application, to determine the phase where the defect is located, the voltage time-domain waveforms of the three-phase cable under test 205 can be used to diagnose the phase where the hidden defect of the three-phase cable under test 205 is located, and a health diagnosis result is given.

[0077] Specifically, first, the embodiment of the present application can extract the time vectors (T 1i ,T 2i ) corresponding to the injected mismatch point and the systematic mismatch point in the voltage time-domain waveforms, where i = 1, 2, 3,..., 6.

[0078] Then, the embodiment of the present application can set a reflection threshold p, extract the time corresponding to the pole point with an absolute value greater than p in the Ui waveform, denoted as (t 1i ,t 2i ,...,t ni ), where n is the number of pole points with p as the threshold between Ui waveforms (T 1i ,T 2i ).

[0079] Next, the embodiment of the present application can calculate (t 11 -T 11 ,t 21 -T 11 ,...,t (n1)1 -T 11 ), (t 12 -T 12 ,t22 -T 12 ,...,t (n2)2 -T 12 )、(t 13 -T 13 ,t 23 -T 13 ,...,t (n3)3 -T 13 )。

[0080] Finally, the embodiment of the present application can extract the waveform of U1 and compare it with the extracted time vector. Each new time vector is compared one by one. If the time vector of U1 also exists in at least one other vector with an epsilon tolerance, it is considered that the hidden danger is more serious, and the phase with the maximum extreme value at the time point exists. If the time vector of U1 does not exist in another two vectors with an epsilon tolerance, it is considered that the hidden danger is less serious, and the propagation to other phases has been attenuated to be negligible. It is considered that the phase corresponding to the defect is the phase represented by the U1 waveform. The judgment of U2 and U3 is the same.

[0081] Further, in the embodiment of the present application, the position and direction of the defect can also be determined. That is, the embodiment of the present application can also diagnose the direction of the defect and determine the position of the defect.

[0082] Specifically, first, the embodiment of the present application can select the voltage time domain waveform of another group of control phases according to the phase where the defect is located.

[0083] Then, the embodiment of the present application can mark the time vector of the pole, and compare and analyze whether the time vector in the waveform contains complementary time elements one by one, to judge whether there exists a time vector that satisfies that the sum of the two times with a psai error is equal to T 2i -T 1i If it is satisfied, it can be determined that the error is in the N section, otherwise, it is determined that the error is in the M section.

[0084] Finally, the embodiment of the present application records the time label of the fault point at the M-N section cross interconnection box 206, and then the absolute value of the position of the defect with the M-N section cross interconnection box 206 as the zero point can be obtained. The absolute value of the position of the defect can be:

[0085] Where t ki is the time corresponding to the kth pole with an absolute value greater than p in the ith test voltage waveform, T 1i is the time corresponding to the injection of the mismatch point in the ith test voltage data, and T 2iis the time corresponding to the system mismatch point in the ith test voltage data, k is the label of the pole, i is the label of the voltage to be measured, L0 is the spacing between the cross-connection boxes, t ki -T 1i is the time label of the fault point at the M-N cross-connection box.

[0086] The embodiment of the present application can analyze the M-N section cross-connection box 206 according to the voltage time domain waveform, and diagnose the phase, position and direction of the hidden defect of the M-N section three-phase cable 205 to be measured with higher accuracy by excluding the cross-connection lead. In addition, in actual execution, the analysis process of the N-O section cross-connection box 206 is similar to that of the M-N section cross-connection box 206, and only the selection of the data set is different, which will not be described in detail here.

[0087] In combination with FIG. 3, the working principle of the power cable defect time domain diagnosis method based on the cross-connection box structure proposed by the embodiment of the present application is described in detail with a specific embodiment.

[0088] FIG. 3 is a block schematic diagram of the working principle of the power cable defect time domain diagnosis method based on the cross-connection box structure according to an embodiment of the present application.

[0089] Step S301: Construct a preset loop and check. That is, the embodiment of the present application can construct a preset loop in the manner shown in FIG. 1, and check whether the connection is electrically reliable after the preset loop is constructed.

[0090] Step S302: Output and collect signals. That is, the waveform generator of the embodiment of the present application can output a wide frequency signal with a certain repetition frequency, and the signal collection device 202 can collect the port signal U0.

[0091] Step S303: Collect the initial voltage time domain waveform of the M-N section three-phase cable 205 to be measured in the steady state. Specifically, the embodiment of the present application can connect the injection poles at the end of the second cable section 2042 to a / a / b of the M-N section cross-connection box 206, respectively, and connect the return flow poles at the end of the second cable section 2042 to c / b / c of the M-N section cross-connection box 206, respectively, and keep the settings of the waveform generator and the signal collection device 202, and collect the port signals U1, U2 and U3 in a single cycle in the steady state under this condition.

[0092] Step S304: Collect the initial voltage time-domain waveforms generated by the N-O section of the to-be-tested three-phase cable 205 in the steady state. Specifically, the second cable section 2042 end injection pole is connected to the a / a / b of the N-O section cross connection box 206, and the second cable section 2042 end return pole is connected to the c / b / c of the N-O section cross connection box 206, the previous waveform generator and signal acquisition device 202 are kept, and the port signals U4, U5, U6 in a single cycle in the steady state are collected.

[0093] Step S305: Initial voltage time-domain waveform preprocessing. That is, the discrete wavelet transform is used to transform U1-U6, and the hard threshold method is used to filter the collected initial voltage time-domain waveforms, wherein the wavelet transform coefficient ψ a,b (t) can be expressed as:

[0094] Where ψ is the wavelet basis function.

[0095] Further, the number of 5-layer decomposition can be selected, and the hard threshold method can be used to filter out noise, wherein the hard threshold method can be:

[0096] Where k δ is the wavelet transform coefficient processed according to the hard threshold method, ψ a,b (t) is the wavelet transform coefficient, and δ is the set hard threshold, wherein the expression of the hard threshold can be:

[0097] Where m is the median of the signal decomposition layer, and n is the length of the signal decomposition layer.

[0098] Further, the wavelet inverse transform is used on the filtered result to obtain the voltage time-domain waveform after filtering out noise.

[0099] Step S306: Determine the phase where the defect is located. That is, to determine the phase where the defect is located, the voltage time-domain waveform of the to-be-tested three-phase cable 205 can be used to diagnose the phase where the to-be-tested three-phase cable 205 hidden defect is located, and a health diagnosis result is given.

[0100] Specifically, first, the time vector (T 1i ,T 2i ) corresponding to the injection mismatch point and the systematic mismatch point in the voltage time-domain waveform can be extracted, wherein i=1, 2, 3,..., 6.

[0101] Then, the embodiment of the present application can set a reflection threshold p, extract the time corresponding to the pole with an absolute value greater than p in the Ui waveform, denoted as (t 1i ,t 2i ,...,t ni ), wherein n is the number of poles with p as the threshold between Ui waveforms (T 1i ,T 2i ).

[0102] Next, the embodiment of the present application can calculate (t 11 -T 11 ,t 21 -T 11 ,...,t (n1)1 -T 11 ), (t 12 -T 12 ,t 22 -T 12 ,...,t (n2)2 -T 12 ), (t 13 -T 13 ,t 23 -T 13 ,...,t (n3)3 -T 13 ).

[0103] Finally, the embodiment of the present application can extract the waveform of U1 and compare it with the extracted time vector, compare each new time vector one by one, if the time vector of U1 also exists in at least one other vector with epsilon as the tolerance, it is considered that the hidden danger is more serious, and exists in the phase with the maximum extreme value at that time point; if the time vector of U1 does not exist in another two vectors with epsilon as the tolerance, it is considered that the hidden danger is less serious, and the propagation to other phases has been attenuated to be negligible, then it is considered that the corresponding phase of the defect is the phase represented by the U1 waveform. The judgment of U2 and U3 is the same.

[0104] Step S307: determining the position and direction of the defect. That is, the embodiment of the present application can also determine the position and direction of the defect. It can be understood that the embodiment of the present application can diagnose the direction of the defect and determine the position of the defect.

[0105] Specifically, first, the embodiment of the present application can select another set of voltage time domain waveforms of the reference phase according to the phase where the defect is located.

[0106] Then, the embodiment of the present application can mark the time vector of the pole, compare and analyze whether the time vector in the waveform contains complementary time elements one by one, and judge whether there exists a sum of two times with an error equal to T 2i -T 1iIf the condition is satisfied, it can be determined that the error is in the N section, otherwise, it is determined that the error is in the M section.

[0107] Finally, the embodiment of the present application records the time tag of the fault point at the M-N section cross interconnection box 206, and then the absolute value of the defect location with the M-N section cross interconnection box 206 as the zero point can be obtained. The absolute value of the defect location can be:

[0108] Wherein, t ki is the time corresponding to the kth pole point with an absolute value greater than p in the ith test voltage waveform, T 1i is the time corresponding to the injection mismatch point in the ith test voltage data, T 2i is the time corresponding to the system mismatch point in the ith test voltage data, k is the pole point label, i is the test voltage label, L0 is the distance between the cross interconnection boxes, t ki -T 1i is the time tag of the fault point at the M-N section cross interconnection box.

[0109] The embodiment of the present application can analyze the M-N section cross interconnection box 206 according to the voltage time domain waveform, and diagnose the phase, position and direction of the hidden defect of the M-N section test three-phase cable 205 with higher accuracy by excluding the cross interconnection lead. In addition, in the actual implementation process, the analysis process of the N-O section cross interconnection box 206 is similar to that of the M-N section cross interconnection box 206, only the selection of data groups is different, which will not be described in detail.

[0110] In addition, the embodiment of the present application can inject signals only in adjacent two cross interconnection boxes 206 without disconnecting the test three-phase cable 205, and can realize the identification and positioning of the hidden defects of the outer sheath and main insulation of the test three-phase cable 205, overcoming the pain points of active injection method in related art that may cause system disconnection and is difficult to monitor online, and has great application prospect in defect positioning, identification and diagnosis of the test three-phase cable 205.

[0111] The power cable defect time domain diagnosis method based on the cross interconnection box structure according to the embodiment of the present application can inject a wideband signal through the wiring terminal of the cross interconnection box of the three-phase shielding layer cross, diagnose the defect time domain diagnosis result of the outer sheath and the main insulation existing in the three-phase cable according to the voltage time domain waveform in the steady state generated by the wideband signal, realize the diagnosis of the hidden defects of the outer sheath and the main insulation in the three-phase cable and the diagnosis positioning under the condition that the electrical connection of the three-phase cable system is not disconnected, and further realize the evaluation of the health state of the three-phase cable system, reduce the demand for on-site equipment and cost, improve the practicability, and further make the online monitoring possible. Thus, the technical problems in the related art that the core wire of the exposed cable in the power cable system is disconnected, the complete topology structure of the power cable system is damaged, it is difficult to perform online monitoring, the demand for on-site equipment is increased, the complexity and cost of the inspection are high, and the practicability is low are solved.

[0112] Secondly, the power cable defect time domain diagnosis device based on the cross interconnection box structure according to the embodiment of the present application is described with reference to the accompanying drawings.

[0113] FIG. 4 is a block schematic diagram of the power cable defect time domain diagnosis device based on the cross interconnection box structure according to the embodiment of the present application.

[0114] As shown in FIG. 4, the power cable defect time domain diagnosis device 10 based on the cross interconnection box structure includes a collection module 100, a preprocessing module 200 and a diagnosis module 300.

[0115] Specifically, the collection module 100 is configured to inject a wideband signal through the wiring terminal of the cross interconnection box of the three-phase shielding layer cross, so as to collect the initial voltage time domain waveform in the steady state generated by the wideband signal based on the three-phase cable to be measured.

[0116] The preprocessing module 200 is configured to pre-process the initial voltage time domain waveform at the same end, and obtain the voltage time domain waveforms at the left and right ends of the cross interconnection box after pre-processing, respectively.

[0117] The diagnosis module 300 is configured to diagnose the defects existing in the outer sheath and the main insulation in the three-phase cable to be measured based on the voltage time domain waveforms at the left and right ends, and obtain the final defect time domain diagnosis result of the three-phase cable to be measured.

[0118] Optionally, in an embodiment of the present application, the preprocessing module 200 includes a generation unit.

[0119] The generation unit is configured to perform discrete wavelet transform based on the initial voltage time domain waveform, respectively, and filter the initial voltage time domain waveform after the discrete wavelet transform by using a hard threshold value, so as to obtain the voltage time domain waveform.

[0120] Optionally, in an embodiment of the present application, the hard threshold method can be:

[0121] wherein, k δ is the wavelet transform coefficient processed according to the hard threshold method, ψ a,b (t) is the wavelet transform coefficient, and δ is the set hard threshold value, wherein the expression of the hard threshold value can be:

[0122] wherein, m is the median of the signal decomposition layer, and n is the length of the signal decomposition layer.

[0123] Optionally, in an embodiment of the present application, the diagnosis module 300 comprises a first determination unit and a second determination unit.

[0124] The first determination unit is configured to determine the phase where the defect is located according to the voltage time-domain waveform.

[0125] The second determination unit is configured to determine the position and direction where the defect is located according to the voltage time-domain waveform.

[0126] Optionally, in an embodiment of the present application, the absolute value of the position where the defect is located can be:

[0127] wherein, t ki is the time corresponding to the kth pole point with an absolute value greater than p in the ith test voltage waveform, T 1i is the time corresponding to the injected mismatch point in the ith test voltage data, T 2i is the time corresponding to the system mismatch point in the ith test voltage data, k is the pole point label, i is the label of the voltage to be tested, and L0 is the spacing between the cross-connection boxes.

[0128] It should be noted that the foregoing explanation and description of the embodiment of the power cable defect time-domain diagnosis method based on the cross-connection box structure also applies to the embodiment of the power cable defect time-domain diagnosis device based on the cross-connection box structure, which will not be described here again.

[0129] According to the power cable defect time domain diagnosis device based on the cross-interconnected box structure provided in the embodiments of the present application, the wideband signal can be injected through the wiring terminal based on the cross-interconnection of the three-phase shielding layer of the cross-interconnected box, and the defect time domain diagnosis result of the defects existing in the outer sheath and the main insulation in the three-phase cable can be diagnosed according to the voltage time domain waveform generated by the wideband signal in the steady state, so that the hidden defects of the outer sheath and the main insulation in the three-phase cable are diagnosed and the diagnosis positioning is given at the same time under the condition that the electrical connection of the three-phase cable system is not disconnected, and the health status of the three-phase cable system is evaluated, thereby reducing the demand for on-site equipment and cost, improving the practicability, and further making it possible to realize online monitoring. Thus, the technical problems in the related art that the core wire of the exposed cable in the power cable system is disconnected, the complete topology structure of the power cable system is damaged, it is difficult to realize online monitoring, the demand for on-site equipment is increased, the complexity and cost of the inspection are high, and the practicability is low are solved.

[0130] Fig. 5 is a structural schematic diagram of an electronic device provided by the embodiments of the present application. The electronic device can include:

[0131] The memory 501, the processor 502, and the computer program stored in the memory 501 and executable on the processor 502.

[0132] The processor 502 implements the power cable defect time domain diagnosis method based on the cross-interconnected box structure provided in the above embodiments when executing the program.

[0133] Further, the electronic device further includes:

[0134] The communication interface 503 is used for communication between the memory 501 and the processor 502.

[0135] The memory 501 is used to store the computer program executable on the processor 502.

[0136] The memory 501 can include a high-speed RAM memory, and can also include a non-volatile memory such as at least one disk memory.

[0137] If the memory 501, the processor 502 and the communication interface 503 are implemented independently, the communication interface 503, the memory 501 and the processor 502 can be connected with each other through a bus and complete communication between each other. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. For convenience of representation, only one thick line is used in FIG. 5, but it does not mean that there is only one bus or only one type of bus.

[0138] Optionally, in a specific implementation, if the memory 501, the processor 502 and the communication interface 503 are integrated on a chip, the memory 501, the processor 502 and the communication interface 503 can complete communication between each other through an internal interface.

[0139] The processor 502 can be a Central Processing Unit (CPU), or an Application Specific Integrated Circuit (ASIC), or one or more integrated circuits configured to implement one or more embodiments of the present application.

[0140] The embodiment of the present application further provides a computer readable storage medium, which has a computer program stored thereon, and the program is executed by a processor to implement the power cable defect time domain diagnosis method based on the cross-connection box structure as described above.

[0141] The embodiment of the present application further provides a computer program product, which includes a computer program, and the computer program is executed to implement the power cable defect time domain diagnosis method based on the cross-connection box structure as described above.

[0142] In the description of the application, reference to "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" means that a particular feature, structure, material, or characteristic being described is included in at least one embodiment or example of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment or example. Furthermore, the described specific features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples. In addition, the usage of "N" means at least two, for example, two, three or the like, unless explicitly stated otherwise.

[0143] Furthermore, the terms "first", "second", or the like, are used merely as a designation of certain elements or features of the application, and do not imply or connote relative importance or a specific order of precedence. Thus, features defined with "first", "second", etc. can include at least one of the features, either explicitly or implicitly.

[0144] Any process or method descriptions or blocks in flow charts or otherwise described herein represent embodiments of modules, segments, or portions of code which include one or more executable instructions for implementing specific logic functions or steps, and alternate implementations are possible. In some embodiments, the processes or methods described in flow charts or otherwise described herein are not necessarily performed in the order shown or discussed, including, for example, performing or depending from other operations or stages, in parallel, in reverse order, or in some other suitable manner.

[0145] The logic and / or steps represented in the flowcharts and / or described herein, for example, can be considered as a sequence of executable instructions stored in a computer readable medium, which can be executed by an instruction execution system, apparatus or device, such as a computer-based system, a processor-based system, or other system that can fetch the instructions from the instruction execution system, apparatus or device and execute the instructions, or a combination of the above. For the purposes of this specification, a "computer readable medium" can be any apparatus that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus or device. The computer readable medium can be a computer readable storage medium or a computer readable signal medium. The computer readable storage medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or a propagation medium. The computer readable signal medium can include, but is not limited to, a computer readable medium that facilitates transfer of the program from one place to another. A specific example of a computer readable medium is a non-transitory computer-readable storage medium. A specific example of a computer readable signal medium is a source or destination of the computer readable medium. Another specific example of a computer readable signal medium is a computer readable signal travelling through space. Thus, a computer readable medium can take many forms of hardware to carry out the program for use by or in connection with the instruction execution system, apparatus or device.

[0146] It should be understood that aspects of the application can be implemented in hardware, software, firmware or a combination thereof. In the above embodiments, the N steps or methods can be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. If implemented in hardware and in another embodiment, the hardware can be implemented using any or a combination of the following technologies, which are each well known in the art: a discrete logic circuit(s) having logic gates for implementing logic functions upon an application of data signals, an application specific integrated circuit having appropriate combinational logic gates, a programmable gate array(s) (PGA), a field programmable gate array (FPGA), etc.

[0147] Those of skill in the art would understand that the steps of the methods carried out above can be carried out wholly or partly by a program instructing relevant hardware, and the program can be stored in a computer readable storage medium, and when executed, includes one or a combination of the steps of the method embodiments.

[0148] In addition, each of the functional units in the various embodiments of the present application can be integrated in one processing module, or each of the units can be physically present separately, or two or more units can be integrated in one module. The integrated module can be implemented in the form of hardware or in the form of a software functional module. When the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it can also be stored in a computer readable storage medium.

[0149] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A time domain diagnosis method for power cable defects based on a cross-connection box structure, characterized in that: The following steps are involved: Injecting a broadband signal into the wiring terminals of the three-phase shielding layer cross of the cross-connection box to collect the initial voltage time domain waveform of the three-phase cable to be tested in a steady state generated by the broadband signal; Preprocessing the initial voltage time domain waveform at the same end to obtain preprocessed voltage time domain waveforms at the left and right ends of the cross-connection box; Defects in the outer sheath and main insulation of the three-phase cable to be tested are diagnosed based on the voltage time-domain waveforms at the left and right ends, and a final defect time-domain diagnosis result of the three-phase cable to be tested is obtained.

2. The method according to claim 1, characterized in that The preprocessing of the initial voltage time domain waveform at the same end to obtain the preprocessed voltage time domain waveforms at the left and right ends of the cross-connection box respectively includes: Discrete wavelet transform is performed on the initial voltage time domain waveform respectively, and a hard threshold is selected to filter the initial voltage time domain waveform after discrete wavelet transform to obtain the voltage time domain waveform.

3. The method according to claim 2, characterized in that The hard threshold method is: Among them, k δ is the wavelet transform coefficient after hard thresholding, ψ a,b (t) is the wavelet transform coefficient, δ is the set hard threshold, where the expression of the hard threshold is: Where m is the median of the signal decomposition layer, and n is the length of the signal decomposition layer.

4. The method according to claim 1, wherein The diagnosing defects in the outer sheath and main insulation of the three-phase cable to be tested based on the voltage time domain waveforms at the left and right ends to obtain a final defect time domain diagnosis result of the three-phase cable to be tested includes: determining the phase where the defect is located according to the voltage time domain waveform; The position and direction of the defect are determined according to the voltage time domain waveform.

5. The method according to claim 4, characterized in that The absolute value of the position of the defect is: Among them, t ki T is the time corresponding to the kth extreme point in the i-th test voltage waveform whose absolute value of the amplitude is greater than p, 1i T is the time corresponding to the injection of the mismatch point in the i-th test voltage data. 2i is the time corresponding to the system mismatch point in the i-th test voltage data, k is the number of the pole, i is the number of the voltage to be measured, and L0 is the distance between the cross-connection boxes.

6. A time domain diagnostic device for power cable defects based on a cross-connection box structure, characterized in that: include: The acquisition module is used to inject broadband signals into the wiring terminals of the three-phase shielding layer of the cross-connection box to collect An initial voltage time domain waveform of the three-phase cable to be tested in a steady state generated based on the broadband signal; A preprocessing module, configured to preprocess the initial voltage time domain waveform at the same end to obtain preprocessed voltage time domain waveforms at the left and right ends of the cross-connection box; The diagnostic module is used to diagnose defects in the outer sheath and main insulation of the three-phase cable to be tested based on the voltage time domain waveforms at the left and right ends, and obtain a final defect time domain diagnostic result of the three-phase cable to be tested.

7. The device according to claim 6, characterized in that The preprocessing module includes: The generating unit is configured to perform discrete wavelet transform on the initial voltage time domain waveform, and select a hard threshold to filter the initial voltage time domain waveform after discrete wavelet transform to obtain the voltage time domain waveform.

8. The device according to claim 7, characterized in that The hard threshold method is: Among them, k δ is the wavelet transform coefficient after hard thresholding, ψ a,b (t) is the wavelet transform coefficient, δ is the set hard threshold, where the expression of the hard threshold is: Where m is the median of the signal decomposition layer, and n is the length of the signal decomposition layer.

9. The device according to claim 6, characterized in that The diagnostic module comprises: A first determining unit, configured to determine the phase where the defect is located according to the voltage time domain waveform; The second determining unit is configured to determine the position and direction of the defect according to the voltage time domain waveform.

10. The device according to claim 9, characterized in that The absolute value of the position of the defect is: Among them, t ki T is the time corresponding to the kth extreme point in the i-th test voltage waveform whose absolute value of the amplitude is greater than p, 1i T is the time corresponding to the injection of the mismatch point in the i-th test voltage data. 2i is the time corresponding to the system mismatch point in the i-th test voltage data, k is the number of the pole, i is the number of the voltage to be measured, and L0 is the distance between the cross-connection boxes.

11. An electronic device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the time domain diagnosis method for power cable defects based on a cross-connection box structure according to any one of claims 1 to 5.

12. A computer-readable storage medium having a computer program stored thereon, characterized in that: The program is executed by a processor to implement the time-domain diagnosis method for power cable defects based on a cross-connection box structure as described in any one of claims 1 to 5.

13. A computer program product, characterized in that The invention comprises a computer program, which, when executed, is used to implement the time domain diagnosis method for power cable defects based on a cross-connection box structure according to any one of claims 1 to 5.

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