Method and apparatus for frequency domain diagnosis of power cable defect on basis of cross-interconnection box structure

Abstract

A method and apparatus for frequency domain diagnosis of a power cable defect on the basis of a cross-interconnection box structure. The method comprises: by means of a wiring terminal intersecting a three-phase shielding layer of a cross-interconnection box, injecting a broadband signal, and obtaining a time domain result (S101); according to the time domain result being mapped into a frequency domain, performing analysis, and obtaining impedance spectrum results of a left end and a right end of an injection cross-interconnection box (S102); and, according to the impedance spectrum results, diagnosing hidden danger defects of an outer sheath and a main insulation in a three-phase cable (S103). The present disclosure solves the problem in the related technology that traveling wave reflection method diagnosis strategies cannot avoid direct connection to a cable core wire when identifying a main insulation fault in a cable, which limits the application scenarios of a traveling wave injection method to only being applicable to inspection before a cable has been put into operation and cable defect assessment after a cable fault has occurred. Additionally, the present disclosure solves the problems of high device requirements and testing costs, leading to the inability to meet daily operation and maintenance inspection requirements of cables and various test scenarios.

Description

Power cable defect frequency domain diagnosis method and device based on cross-interconnected box structure

[0001] Cross-reference to related applications

[0002] The present application claims priority to the Chinese patent application No. "202410474143.X" filed on April 19, 2024, with the title of "Power cable defect frequency domain diagnosis method and device based on cross-interconnected box structure" of Tsinghua University. TECHNICAL FIELD

[0003] The present application relates to the field of high-voltage technology, in particular to a power cable defect frequency domain diagnosis method and device based on cross-interconnected box structure. BACKGROUND

[0004] As an important part of urban power distribution network, if a cable fails, it will threaten the safe and stable operation of the urban power grid and cause economic losses. If potential hidden faults can be warned before they occur, and fault information can be evaluated and fault locations can be given, it will be beneficial to the operation and maintenance of the cable system and the safety of the urban power grid. Since these potential hidden defects do not substantially threaten the urban cable power grid, traditional positioning strategies based on short-circuit and open-circuit hard faults are limited, and new diagnosis strategies are needed for potential hidden defects, which are soft faults.

[0005] In related technologies, potential hidden defects of power cables are mainly divided into traveling wave method and impedance method. The traveling wave method has higher identification and positioning accuracy than the impedance method. The traveling wave method can be divided into a traveling wave method based on power grid operating parameters and a traveling wave method based on artificially injected signals. Since the traveling wave reflection method based on artificially injected signals can artificially control the frequency components of the injected signals, the injection pole or return pole that injects a wideband signal must be electrically connected directly to the cable core wire, i.e., it is required to disconnect the intermediate joint of the in-service power cable or manually saw open the cable core wire at the exposed part. This has a greater advantage in detecting smaller hidden defects.

[0006] However, the traveling wave reflection method diagnosis strategy in related technologies cannot avoid the great limitation of the electrically direct connection to the cable core wire when identifying the main insulation fault of the cable, which greatly limits the application scenarios of the traveling wave injection method. It can only be applied to pre-commissioning detection of the cable and cable defect evaluation after the cable has failed. Moreover, the equipment requirements and testing costs are high, which cannot meet the requirements of daily operation and maintenance inspection of the cable and various testing scenarios, and needs to be urgently solved.

[0007] SUMMARY

[0008] The application provides a power cable defect frequency domain diagnosis method and device based on a cross-interconnected box structure, to solve the problems in the related art that the traveling wave reflection method diagnosis strategy cannot avoid the great limitation of the electrical direct connection to the cable core when identifying the main insulation fault of the cable, can only be applied to the detection before the cable is put into operation and the cable defect evaluation after the cable has failed, and the device requirement and test cost are high, and the power cable daily operation and maintenance inspection requirements and various test scenes cannot be met.

[0009] The first aspect of the application provides a power cable defect frequency domain diagnosis method based on a cross-interconnected box structure, comprising the following steps: injecting a wideband signal through a cross-interconnected box-based three-phase shielding layer cross connection terminal, obtaining a time domain result; analyzing the time domain result according to the mapping to the frequency domain, obtaining an impedance spectrum result injected into the left and right ends of the cross-interconnected box; and diagnosing hidden defects of the outer sheath and the main insulation in the three-phase cable according to the impedance spectrum result.

[0010] Optionally, in an embodiment of the application, the impedance spectrum result of each phase fusion impedance spectrum is:

[0011] Z C,X is the capacitance of the X phase corresponding to the cross-interconnected box, X=A, B, C, Z in,1 , Z in,2 , and Z in,3 respectively represent the series fusion impedance spectrum of the corresponding signal, and alpha and beta respectively correspond to the proportional coefficient of the test result, and are respectively:

[0012] Optionally, in an embodiment of the application, the diagnosis of hidden defects of the outer sheath and the main insulation in the three-phase cable according to the impedance spectrum result comprises: obtaining the hidden defects of the outer sheath and the main insulation by using a preset analysis formula based on the fusion impedance spectrum of each phase, wherein the preset analysis formula is:

[0013] wherein X=A, B, C, A, B, C represent the A, B, C phases corresponding to the M-N cross-interconnected box, Z h (f) is the health state impedance spectrum updated in advance in the system, gamma h (f) is the propagation constant in the healthy state, Z X represents the fusion impedance spectrum of each phase, Z X (f) represents the fusion impedance spectrum value of the X phase at the frequency f, f h , f l respectively represent the upper limit frequency fh and the lower limit frequency f l , R X (·) represents the diagnostic result of the X phase, e represents a natural constant, L c represents the total length of the cable to be tested.

[0014] Optionally, in an embodiment of the present application, after obtaining the time domain result, further comprising: filtering the time domain waveform in the time domain result by using a discrete wavelet transform and selecting a hard threshold method, wherein the hard threshold method is:

[0015] wherein ψ a,b is a wavelet transform coefficient, ψ(·) is a wavelet base function, K δ represents a wavelet transform coefficient processed by the hard threshold method, a is a scale parameter in the wavelet transform, b is a time parameter in the wavelet transform, t represents time, and δ represents a set hard threshold value.

[0016] The second aspect embodiment of the present application provides a power cable defect frequency domain diagnosis device based on a cross-interconnected box structure, comprising: a calculation module configured to inject a wideband signal through a cross-interconnected box-based three-phase shielding layer cross-over terminal, to obtain a time domain result; an analysis module configured to analyze according to the time domain result mapped into a frequency domain, to obtain an impedance spectrum result injected into the left and right ends of the cross-interconnected box; and a diagnosis module configured to diagnose hidden defects of an outer sheath and a main insulation in a three-phase cable according to the impedance spectrum result.

[0017] Optionally, in an embodiment of the present application, each phase fusion impedance spectrum of the impedance spectrum result is:

[0018] wherein Z C,X is the capacitance of the X phase corresponding to the cross-interconnected box, X=A, B, C, Z in,1 , Z in,2 , and Z in,3 respectively represent the series fusion impedance spectrum of the corresponding signal, and α and β respectively correspond to the proportional coefficients of the test result, and are respectively:

[0019] Optionally, in an embodiment of the present application, the diagnosis module comprises: a calculation unit configured to obtain hidden defects of the outer sheath and the main insulation by using a preset analysis formula based on the each phase fusion impedance spectrum, wherein the preset analysis formula is:

[0020] wherein X=A, B, C, A, B, and C respectively represent A, B, and C phases corresponding to the M-N cross-interconnected box, and Zh (f) is the pre-updated health state impedance spectrum of the system, β h (f) is the propagation constant in the health state, Z X represents the fusion impedance spectrum of each phase, Z X (f) represents the fusion impedance spectrum value of the X phase at the frequency f, f h , f l respectively represent the upper limit frequency f h and the lower limit frequency f l , R X (·) represents the diagnostic result of the X phase, e represents the natural constant, L c represents the total length of the cable to be measured.

[0021] Optionally, in one embodiment of the present application, after obtaining the time domain result, further comprising: a filtering module, configured to filter the time domain waveform in the time domain result by using a discrete wavelet transform and a hard threshold method, wherein the hard threshold method is:

[0022] wherein ψ a,b is a wavelet transform coefficient, ψ(·) is a wavelet base function, K δ represents the wavelet transform coefficient processed by the hard threshold method, a is a scale parameter in the wavelet transform, b is a time parameter in the wavelet transform, t represents time, and δ represents the set hard threshold value.

[0023] The third aspect embodiment 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, and the processor executes the program to realize the power cable defect frequency domain diagnosis method based on the cross-interconnected box structure as described in the above embodiments.

[0024] The fourth aspect embodiment of the present application provides a computer readable storage medium, which stores a computer program, and the program is executed by a processor to realize the power cable defect frequency domain diagnosis method based on the cross-interconnected box structure as described above.

[0025] The fifth aspect embodiment of the present application provides a computer program product, and the computer program is executed to realize the power cable defect frequency domain diagnosis method based on the cross-interconnected box structure as described above.

[0026] The embodiments of the present application can obtain the impedance spectrum results injected into the left and right ends of the cross interconnection box by analyzing the time domain results of the wideband signal injected into the cross interconnection box based on the three-phase shielding layer cross connection, thereby diagnosing the hidden defects of the outer sheath and the main insulation in the three-phase cable. The method based on time domain testing can analyze the impedance spectrum of the cable system under the condition of only testing the voltage response, thereby reducing the device requirements and testing cost of the field test. The test based on two cross interconnection boxes can analyze the hidden defects of the outer sheath and the main insulation in the three-phase cable and give a diagnosis and positioning, thereby realizing that the response characteristics of the cable system can be tested by injecting a wideband signal from the metal access point of the cross interconnection box without disconnecting any electrical connection of the cable network, so that the frequency domain reflection method can be applied to the online testing or non-disconnection system testing scene. Thus, the problems in the related art that the traveling wave reflection method diagnosis strategy cannot avoid the electrical direct connection to the cable core when identifying the main insulation fault of the cable, greatly limits the application scene of the traveling wave injection method, can only be applied to the detection before the cable is put into operation and the cable defect evaluation after the cable has failed, and the device requirements and testing cost are high, and cannot meet the daily operation and maintenance inspection requirements and various testing scenes of the cable are solved.

[0027] Additional aspects and advantages of the present application will be made apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0028] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the following description, taken in conjunction with the accompanying drawings, in which:

[0029] FIG. 1 is a flowchart of a power cable defect frequency domain diagnosis method based on a cross interconnection box structure according to an embodiment of the present application;

[0030] FIG. 2 is a test circuit schematic diagram of an online diagnosis test method according to an embodiment of the present application;

[0031] FIG. 3 is a structural schematic diagram of a power cable defect frequency domain diagnosis device based on a cross interconnection box structure according to an embodiment of the present application;

[0032] FIG. 4 is a structural schematic diagram of an electronic device according to an embodiment of the present application.

[0033] BRIEF DESCRIPTION OF DRAWINGS: 10-power cable defect frequency domain diagnosis device based on a cross interconnection box structure: 100-computing module, 200-analysis module, and 300-diagnosis module; 401-memory, 402-processor, and 403-communication interface. DETAILED DESCRIPTION

[0034] Embodiments of the present application are described below in detail with reference to the accompanying drawings, examples of which are shown in the drawings, wherein the same or similar notations represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by reference to the drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0035] The power cable defect frequency domain diagnosis method and device based on the cross-interconnected box structure of the embodiments of the present application are described below with reference to the accompanying drawings. In order to solve the problem that the traveling wave reflection method diagnosis strategy in the background art cannot avoid electrical direct connection to the cable core when identifying the main insulation fault of the cable, greatly limits the application scene of the traveling wave injection method, can only be applied to the detection before the cable is put into operation, the cable defect evaluation after the cable has occurred fault, and the device requirement and test cost are high, and cannot meet the daily operation and maintenance inspection requirements and various diagnosis scenes of the cable, the present application provides a power cable defect frequency domain diagnosis method based on a cross-interconnected box structure. In the method, the time domain results obtained by injecting a wideband signal through the cross-interconnected box based on the three-phase shielding layer cross-over terminal can be analyzed, and then the impedance spectrum results injected into the left and right ends of the cross-interconnected box can be obtained, thereby diagnosing the hidden defects of the outer sheath and the main insulation of the three-phase cable. Thus, the problem of the related art that the traveling wave reflection method diagnosis strategy cannot avoid electrical direct connection to the cable core when identifying the main insulation fault of the cable, greatly limits the application scene of the traveling wave injection method, can only be applied to the detection before the cable is put into operation, the cable defect evaluation after the cable has occurred fault, and the device requirement and test cost are high, and cannot meet the daily operation and maintenance inspection requirements and various diagnosis scenes of the cable, and the like are solved.

[0036] Specifically, FIG. 1 is a flow diagram of a power cable defect frequency domain diagnosis method based on a cross-interconnected box structure provided by an embodiment of the present application.

[0037] As shown in FIG. 1, the power cable defect frequency domain diagnosis method based on the cross-interconnected box structure includes the following steps:

[0038] In step S101, a wideband signal is injected through the cross-interconnected box based on the three-phase shielding layer cross-over terminal to obtain time domain results.

[0039] In the actual execution process, when performing power cable defect frequency domain diagnosis, a wideband signal can be injected through the cross-interconnected box based on the three-phase shielding layer cross-over terminal, and thus the time domain results can be obtained.

[0040] For example, as shown in FIG. 2, it is a test circuit diagram of a non-invasive online diagnosis test method for power cable hidden defect injection based on a cross-interconnected box according to an embodiment of the present application.

[0041] In the test, the tested object can be an in-service three-phase cable without any disconnection treatment, and the test site can be the cross-connection box of adjacent sections; the test circuit is composed of a waveform generator, a signal acquisition device, a T-shaped connector and a signal connection cable.

[0042] In actual testing, the internal resistance of the selected waveform generator and the signal connection cable should be well impedance-matched; the input resistance of the signal acquisition device should be as large as possible, and be in an open-circuit state. The three-phase cable test based on the cross-connection box injection is composed of two groups of tests, which are respectively performed in two adjacent cross-connection boxes, as shown in FIG. 2.

[0043] As shown in FIG. 2, taking the identification of hidden defects of the cables of sections M, N and O as an example, the specific operation steps can be as follows:

[0044] Step 1: After the test circuit is established according to the circuit of FIG. 2, it is checked whether the connection is electrically reliable, and the lengths of the connection signal cable 1 and the connection signal cable 2 are recorded, which are l1 and l2 respectively;

[0045] Step 2: The injection electrode and the return electrode at the end of the cable section 2 are suspended, the waveform generator outputs a wideband signal with a certain repetition frequency, and the port signal U0 in the steady state is acquired;

[0046] Step 3: The injection electrode at the end of the cable section 2 is connected to the a / a / b of the cross-connection box M-N, the return electrode at the end of the cable section 2 is connected to the c / b / c of the cross-connection box M-N, the settings of the waveform generator and the signal acquisition device are kept, and the port signals U1, U2 and U3 in a single cycle in the steady state under this condition are acquired respectively;

[0047] Step 4: The injection electrode at the end of the cable section 2 is connected to the a / a / b of the cross-connection box N-O, the return electrode at the end of the cable section 2 is connected to the c / b / c of the cross-connection box N-O, the settings of the waveform generator and the signal acquisition device are kept, and the port signals U4, U5 and U6 in a single cycle in the steady state under this condition are acquired respectively.

[0048] The embodiments of the present application can obtain the time-domain results by injecting a wideband signal based on the cross-connection box three-phase shielding layer cross connection terminal, so that the wideband signal can be injected from the metal access point of the cross-connection box without the electrical connection of the cable core, the response characteristics of the cable system are tested, the limitation that the injection electrode or the return electrode of the injected wideband signal must be directly connected to the cable core is solved, the frequency domain reflection method can be applied to the online test or the test scene of the non-disconnection system, and the application range is greatly expanded.

[0049] Optionally, in one embodiment of the present application, after obtaining the time domain result, further comprising: filtering the time domain waveform in the time domain result by using discrete wavelet transform and selecting a hard threshold method, wherein the hard threshold method can be represented as:

[0050] wherein ψ a,b is a wavelet transform coefficient, ψ(·) is a wavelet base function, K δ represents a wavelet transform coefficient processed by the hard threshold method, a is a scale parameter in the wavelet transform, b is a time parameter in the wavelet transform, and t represents time.

[0051] In some embodiments, after injecting a wideband signal by a wiring terminal based on three-phase shielding layer cross of a cross-connection box to obtain a time domain result, it is necessary to analyze the result, at this time, discrete wavelet transform can be used first, and a hard threshold method is selected to filter the collected time domain waveform, and the formula can be represented as follows:

[0052] wherein ψ a,b is a wavelet transform coefficient, ψ(·) is a wavelet base function, a is a scale parameter in the wavelet transform, and b is a time parameter in the wavelet transform.

[0053] Here, but not limited to, 5 layers of decomposition number, the hard threshold method is used to filter out noise, that is:

[0054] wherein ψ a,b is a wavelet transform coefficient, ψ(·) is a wavelet base function, K δ represents a wavelet transform coefficient processed by the hard threshold method, a is a scale parameter in the wavelet transform, b is a time parameter in the wavelet transform, and t represents time.

[0055] For the result obtained after filtering, inverse wavelet transform can be used to obtain the time domain waveform after filtering out noise.

[0056] In the embodiments of the present application, after obtaining the time domain result, the hard threshold method is selected to filter the time domain waveform in the time domain result by using discrete wavelet transform, which effectively overcomes the interference caused by accidental factors and has good filtering effect on errors caused by random interference or unstable samplers.

[0057] In step S102, the time domain result is mapped to the frequency domain for analysis to obtain impedance spectrum results injected into the left and right ends of the cross-connection box.

[0058] Based on the description of other embodiments, it can be understood that after obtaining the time domain result, a discrete wavelet transform can be used to filter the time domain waveform in the time domain result by using a hard threshold method, and in addition, the application can also analyze the mapping to the frequency domain according to the time domain result, so as to obtain the impedance spectrum result injected into the left and right ends of the cross-connection box.

[0059] Specifically, for the filtered signal, a fast Fourier transform can be performed to obtain U i,f , i = 0, 1, …, 6;

[0060] For the transformed result, the following calculation method can be used to obtain the series fusion impedance spectrum corresponding to each test result, where i = 1, 2, …, 6, and the formula can be expressed as follows:

[0061] , where the variable S i is

[0062] , γ 1, γ 2 are the propagation constants of the cable section 1 and the cable section 2 respectively, Z 1, Z 2, Z i are the characteristic impedance of the cable section 1, the characteristic impedance of the cable section 2, and the input impedance of the waveform generating device respectively, Z in,i is the series fusion impedance spectrum, U 0,f , U i,f are the frequency domain waveforms of the measured steady-state signal in the empty state and the frequency domain waveforms of the measured steady-state signal numbered i (i = 1, 2, …, 6) respectively, S i is the variable S in,i in Z i , l 1, l 2 are the lengths of the connecting cable 1 and the connecting cable 2 respectively, and tanh(·) is the hyperbolic tangent function.

[0063] Step S103, diagnosing hidden defects of the outer sheath and the main insulation in the three-phase cable according to the impedance spectrum result.

[0064] Optionally, in an embodiment of the application, diagnosing hidden defects of the outer sheath and the main insulation in the three-phase cable according to the impedance spectrum result comprises: obtaining hidden defects of the outer sheath and the main insulation based on each phase fusion impedance spectrum by using a preset analysis formula, wherein the preset analysis formula can be:

[0065] , X = A, B, C, A, B, C represent phases A, B, C corresponding to the M-N cross-connection box respectively, Z h (f) is the health state impedance spectrum updated in advance in the system, γ h (f) is the propagation constant in the health state, Z X represents each phase fusion impedance spectrum, Z X(f) represents the fusion impedance spectrum value of X phase at frequency f, f h , f l represent the upper limit frequency f h and the lower limit frequency f l for integral transform analysis, respectively, R X (·) represents the diagnostic result of X phase, e represents the natural constant, L c represents the total length of the cable to be tested.

[0066] Optionally, in an embodiment of the present application, the fusion impedance spectrum of each phase of the impedance spectrum result can be:

[0067] wherein Z C,X is the capacitance of the X phase corresponding to the cross-connection box, X=A, B, C, Z in,1 , Z in,2 , Z in,3 respectively represent the series fusion impedance spectrum of the corresponding signal, and α and β respectively correspond to the proportional coefficient of the test result, which are:

[0068] In some embodiments, the fusion impedance spectrum of each phase can then be obtained in turn based on the known structural parameters of the test system in an integral transform manner:

[0069] For the M-N cross-connection box, the fusion impedance spectrum of each phase is

[0070] wherein Z C,X is the capacitance of the X phase corresponding to the cross-connection box, X=A, B, C, Z in,1 , Z in,2 , Z in,3 respectively represent the series fusion impedance spectrum of the corresponding signal, and α and β respectively correspond to the proportional coefficient of the test result, which are:

[0071] After obtaining the fusion impedance spectrum of each phase, the hidden defects of the outer sheath and the main insulation in the three-phase cable can be analyzed according to the obtained fusion impedance spectrum of each item and a certain analysis formula, wherein the analysis formula can be represented as:

[0072] wherein X=A, B, C, A, B, C represent the A, B, C phases corresponding to the M-N cross-connection box, respectively, Z h (f) is the health state impedance spectrum updated in advance in the system, γ h(f) is the propagation constant in the healthy state, Z X represents the fusion impedance spectrum of each phase, Z X (f) represents the fusion impedance spectrum value of the X phase at the frequency f, f h , f i respectively represent the upper limit frequency f h and the lower limit frequency f l , R X (·) represents the diagnostic result of the X phase, e represents the natural constant, L c represents the total length of the cable to be tested. The fusion impedance spectrum analysis of the N-O cross interconnection box is the same, and given the identification threshold k, the positioning vectors Vmn and Vno are given in the form of R(x)>k and taking the extreme left: V mn =[a0,a1,…,a s ] V no =[b0,b1,…,b p ]

[0073] Compare each phase positioning vector one by one, if |a i +b j -L c |<ε, it is considered that the two positioning vectors correspond to the same defect, which is in the N section, otherwise in the M section or the O section. Wherein, ε is the error allowed limit, which is recommended to be set to 0.005Lc. Fm, Fn and Fo are respectively the fault positioning vectors identified by the M, N and O sections.

[0074] The embodiments of the present application can diagnose the hidden defects of the outer sheath and the main insulation in the three-phase cable according to the impedance spectrum results based on the fusion impedance spectrum of each phase, and can analyze the hidden defects of the outer sheath and the main insulation in the three-phase cable and give diagnostic positioning based on the test of two cross interconnection boxes, so as to test the response characteristics of the cable system by injecting a wideband signal from the metal access point of the cross interconnection box without disconnecting any electrical connection of the cable network, thereby reducing the equipment requirements and test cost, and meeting the daily operation and maintenance inspection requirements and various diagnostic needs of the cable.

[0075] The power cable defect frequency domain diagnosis method provided in the embodiment of the present application can obtain the impedance spectrum results injected into the left and right ends of the cross interconnection box by analyzing the time domain results of the wideband signal injected through the wiring terminal based on the cross interconnection box of the three-phase shielding layer cross, and thus diagnose the hidden defects of the outer sheath and the main insulation in the three-phase cable. Thus, the problems in the related art that the traveling wave reflection method diagnosis strategy cannot avoid the great limitation of the electrical direct connection to the cable core wire when identifying the main insulation fault of the cable, greatly limits the application scene of the traveling wave injection method, can only be applied to the detection before the cable is put into operation and the cable defect evaluation after the cable has failed, and the device requirement and test cost are high, and the power cable daily operation and maintenance inspection requirements and various diagnosis scenes cannot be met are solved.

[0076] Secondly, the power cable defect frequency domain diagnosis device based on the cross interconnection box structure provided in the embodiment of the present application is described with reference to the accompanying drawings.

[0077] FIG. 3 is a structural schematic diagram of the power cable defect frequency domain diagnosis device based on the cross interconnection box structure of the embodiment of the present application.

[0078] As shown in FIG. 3, the power cable defect frequency domain diagnosis device 10 based on the cross interconnection box structure includes a calculation module 100, an analysis module 200 and a diagnosis module 300.

[0079] The calculation module 100 is configured to inject a wideband signal through the wiring terminal based on the cross interconnection box of the three-phase shielding layer cross to obtain time domain results.

[0080] The analysis module 200 is configured to analyze the time domain results mapped to the frequency domain to obtain impedance spectrum results injected into the left and right ends of the cross interconnection box.

[0081] The diagnosis module 300 is configured to diagnose hidden defects of the outer sheath and the main insulation in the three-phase cable according to the impedance spectrum results.

[0082] Optionally, in an embodiment of the present application, the fusion impedance spectrum of each phase of the impedance spectrum results can be:

[0083] wherein, Z C,X is the capacitance of the X phase corresponding to the cross interconnection box, X=A, B, C, Z in,1 , Z in,2 , Z in,3 respectively represent the series fusion impedance spectrum of the corresponding signal, and α and β respectively correspond to the proportional coefficients of the test results, and are respectively:

[0084] Optionally, in an embodiment of the present application, the diagnosis module 300 comprises a calculation unit.

[0085] The calculation unit is configured to obtain the hidden defects of the outer sheath and the main insulation based on the per-phase fusion impedance spectrum by using a preset analysis formula, wherein the preset analysis formula can be:

[0086] wherein X = A, B, C, A, B, C represent A, B, C phases corresponding to the M-N cross-connection box, respectively, Z h (f) is the pre-updated health state impedance spectrum in the system, β h (f) is the propagation constant in the health state, Z X represents the per-phase fusion impedance spectrum, Z X (f) represents the fusion impedance spectrum resistance value of the X phase at the frequency f, f h , f l respectively represent the upper limit frequency f h and the lower limit frequency f l of the integral transform analysis, R X (·) represents the diagnosis result of the X phase, e represents the natural constant, L c represents the total length of the cable to be measured.

[0087] Optionally, in an embodiment of the present application, after obtaining the time domain result, the method further comprises a filtering module.

[0088] The filtering module is configured to filter the time domain waveform in the time domain result by using a discrete wavelet transform and selecting a hard threshold method, wherein the hard threshold method can be represented as:

[0089] wherein ψ a,b is a wavelet transform coefficient, ψ(·) is a wavelet base function, K δ represents the wavelet transform coefficient after the hard threshold method processing, a is a scale parameter in the wavelet transform, b is a time parameter in the wavelet transform, t represents time, and δ represents the set hard threshold value.

[0090] It should be noted that the foregoing explanation and description of the embodiment of the power cable defect frequency domain diagnosis method based on the cross-connection box structure also applies to the embodiment of the power cable defect frequency domain diagnosis device based on the cross-connection box structure, which will not be described here.

[0091] The power cable defect frequency domain diagnosis device based on the cross-interconnected box structure provided by the embodiment of the application can obtain the time domain results of the wideband signal injected based on the cross-interconnected box three-phase shielding layer cross connection, and then obtain the impedance spectrum results of the left and right ends of the cross-interconnected box, so as to diagnose the hidden defects of the outer sheath and the main insulation of the three-phase cable. Thus, the problem that the traveling wave reflection method diagnosis strategy in the related art cannot avoid the great limitation of the electrical direct connection to the cable core wire when identifying the main insulation fault of the cable, and can only be applied to the detection before the cable is put into operation and the cable defect evaluation after the cable has failed, and the device requirement and the test cost are high, and the daily operation and maintenance inspection requirements and various diagnosis scenes of the cable cannot be met, and other problems are solved.

[0092] Fig. 4 is a structural schematic diagram of an electronic device provided by the embodiment of the application. The electronic device can include:

[0093] The memory 401, the processor 402, and the computer program stored on the memory 401 and executable on the processor 402.

[0094] The processor 402 implements the power cable defect frequency domain diagnosis method based on the cross-interconnected box structure provided in the above embodiments when executing the program.

[0095] Further, the electronic device further includes:

[0096] The communication interface 403 is used for communication between the memory 401 and the processor 402.

[0097] The memory 401 is used to store the computer program executable on the processor 402.

[0098] The memory 401 can include a high-speed RAM memory, and can also include a non-volatile memory, for example, at least one disk memory.

[0099] If the memory 401, the processor 402 and the communication interface 403 are implemented independently, the communication interface 403, the memory 401 and the processor 402 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. 4, but it does not mean that there is only one bus or only one type of bus.

[0100] Optionally, in a specific implementation, if the memory 401, the processor 402 and the communication interface 403 are integrated on a chip, the memory 401, the processor 402 and the communication interface 403 can complete communication between each other through an internal interface.

[0101] The processor 402 can be a Central Processing Unit (CPU), or an Application Specific Integrated Circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present application.

[0102] The embodiments of the present application further provide a computer readable storage medium, which stores a computer program, and the program is executed by a processor to implement the power cable defect frequency domain diagnosis method based on the cross-interconnected box structure as described above.

[0103] The embodiments of the present application further provide a computer program product, which can run computer instructions, and the computer instructions are executed by a processor to implement the power cable defect frequency domain diagnosis method based on the cross-interconnected box structure provided by the embodiments of the present application.

[0104] 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.

[0105] Furthermore, the terms "first", "second", or the like, are used merely as a designation of certain elements or features, and do not imply or connote relative importance or a specific order of categorization of the indicated features. Accordingly, features described as "first" or "second" can be explicitly or implicitly included in at least one of the features. In the description of the application, the term "N" means at least two, for example, two, three, etc., unless explicitly stated otherwise.

[0106] Any process or method descriptions or blocks in flow charts or otherwise described herein represent embodiments which can be managed as one or more 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 and methods described can be executed by one or more apparatuses or devices, either directly or after conversion to another language. Alternate implementations are possible.

[0107] The logic and / or steps represented in the flowcharts and / or described herein, for example, can be considered as a sequence of executable instructions, and can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor- containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For 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 specifically include the following, which are non-exhaustive examples: electrical connection (electrical) having one or N wires, portable computer diskette (magnetic), random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or Flash memory), optical fiber device, and portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium can even be paper or other suitable medium upon which the program is printed, as the program can be electronically captured, via the optically scanned or other suitable techniques, then compiled, interpreted, or otherwise processed in a suitable manner, if necessary, and stored in a computer memory.

[0108] It should be understood that aspects of the application can be implemented in hardware, software, firmware or combinations 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 all well known in the art: a discrete logic circuit having logic gates for implementing logic functions upon data signals, an application specific integrated circuit having appropriate combinational logic gates, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0109] Those of skill in the art could readily implement the above described example methods with all or a portion of the procedures carried out by a program for instructing relevant hardware, and the program can be stored in a computer readable storage medium, which, when executed, includes one of the steps of the method embodiments or a combination thereof.

[0110] 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.

[0111] 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 method for diagnosing defects in power cables in the frequency domain based on a cross-interconnected box structure, characterized by, The method comprises the following steps: Injecting broadband signals through the wiring terminals of the three-phase shield layer cross of the cross-connection box to obtain time-domain results; Mapping the time-domain results to the frequency domain for analysis to obtain impedance spectrum results of the left and right ends of the cross-connection box; Diagnosing hidden defects of the outer sheath and main insulation of the three-phase cable according to the impedance spectrum results.

2. The method of claim 1, wherein, Each phase fusion impedance spectrum of the impedance spectrum result is: wherein Z C,X is the capacitance of the X phase corresponding to the cross-connection box, X = A, B, C, Z in,1 , Z in,2 , Z in,3 respectively represent the series fusion impedance spectrum of the corresponding signal, and α and β respectively correspond to the proportional coefficient of the test result, and are respectively:

3. The method of claim 2, wherein, The diagnosing hidden defects of the outer sheath and main insulation of the three-phase cable according to the impedance spectrum results comprises: Based on the fusion impedance spectrum of each phase, the hidden defects of the outer sheath and the main insulation are obtained by using a preset analysis formula, wherein the preset analysis formula is: where X = A, B, C, A, B, C represent A, B, C phase corresponding to M-N cross interconnection box respectively, Z h (f) is the pre-updated health state impedance spectrum in the system, γ h (f) is the propagation constant in the health state, Z X represents the fusion impedance spectrum of each phase, Z X (f) represents the fusion impedance spectrum resistance value of X phase at frequency f, f h , f l respectively represent the upper limit frequency f h and the lower limit frequency f l of the integral transform analysis, R X (·) represents the diagnosis result of X phase, e represents the natural constant, L c represents the total length of the cable to be measured.

4. The method of claim 1, wherein, After obtaining the time-domain results, the method further comprises: The time-domain waveform in the time-domain result is filtered by using discrete wavelet transform and selecting a hard threshold method, wherein the hard threshold method is: where ψ a,b is the wavelet transform coefficient, ψ(·) is the wavelet base function, K δ represents the wavelet transform coefficient processed by the hard threshold method, a is the scale parameter in the wavelet transform, b is the time parameter in the wavelet transform, t represents the time, and δ represents the set hard threshold value.

5. A power cable defect frequency domain diagnostic apparatus based on a cross-interconnected box structure, characterized by, The method comprises the following steps: A calculating module is configured to inject broadband signals through the wiring terminals of the three-phase shield layer cross of the cross-connection box to obtain time-domain results; An analyzing module is configured to map the time-domain results to the frequency domain for analysis to obtain impedance spectrum results of the left and right ends of the cross-connection box; A diagnosing module is configured to diagnose hidden defects of the outer sheath and main insulation of the three-phase cable according to the impedance spectrum results.

6. The apparatus of claim 5, wherein, Each phase fusion impedance spectrum of the impedance spectrum result is: wherein Z C,X is the capacitance of the X phase corresponding to the cross-connection box, X = A, B, C, Z in,1 , Z in,2 , Z in,3 respectively represent the series fusion impedance spectrum of the corresponding signal, and α and β respectively correspond to the proportional coefficient of the test result, and are respectively:

7. The apparatus of claim 6, wherein, The diagnosing module comprises: A computing unit is configured to obtain the hidden defects of the outer sheath and the main insulation by using a preset analysis formula based on the per-phase fusion impedance spectrum, wherein the preset analysis formula is: where X = A, B, C, A, B, C represent A, B, C phase corresponding to M-N cross interconnection box respectively, Z h (f) is the pre-updated health state impedance spectrum in the system, γ h (f) is the propagation constant in the health state, Z X represents the fusion impedance spectrum of each phase, Z X (f) represents the fusion impedance spectrum resistance value of X phase at frequency f, f h , f l respectively represent the upper limit frequency f h and the lower limit frequency f l of the integral transform analysis, R X (·) represents the diagnostic result of X phase, e represents the natural constant, L c represents the total length of the cable to be measured.

8. An electronic device, comprising: The method comprises the following steps: 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 method for diagnosing defects of a power cable in the frequency domain based on a cross-connection box structure according to any one of claims 1-4.

9. A computer readable storage medium having stored thereon a computer program, characterized in that, The program is executed by the processor to implement the method for diagnosing defects of a power cable in the frequency domain based on a cross-connection box structure according to any one of claims 1-4.

10. A computer program product, characterised in that, The computer program is executed to implement the method for diagnosing defects of a power cable in the frequency domain based on a cross-connection box structure according to any one of claims 1-4.

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