Detection system and detection method for high-voltage cable outer sheath

Abstract

The invention provides a detection system and method for a high-voltage cable outer sheath, and the system comprises a detection system which comprises a signal generator which is used for generating an incident signal; the high-frequency current transformer is connected with the signal generator in series, and the high-frequency current transformer is used for being arranged outside the at least two to-be-tested high-voltage cables in a sleeving mode; and the digital oscilloscope is electrically connected with the high-frequency current transformer and the signal generator respectively. According to the scheme, the detection system is not in contact with the to-be-detected high-voltage cable, the incident signal can be injected into the metal shielding layer of the to-be-detected high-voltage cable, a high-electric-energy wire core is avoided, and then outer sheath detection can be carried out on the running high-voltage cable.

Description

Technical Field

[0001] The present invention relates to the technical field of cable sheath damage detection, and in particular to a detection system and a detection method for a high-voltage cable outer sheath. Background Art

[0002] High-voltage cables work continuously for a long time in cities. As the main equipment for urban power transmission, they play an important role in urban power grids. In the process of operation, the insulation of the cable sheath will inevitably be damaged due to corrosion, external forces and other factors. Due to the complex working environment of the cable, the damage of the outer sheath cannot be detected in time without specific means, which will affect the internal failure of the cable and cause power transmission problems in some areas.

[0003] Traditional methods for testing cable outer sheaths include: insulation resistance measurement method, leakage current test method, etc. The above traditional methods can measure the cable outer sheath, but cannot achieve efficient positioning effect.

[0004] At present, the time-frequency domain detection model is used to locate and detect cable faults. The time-frequency domain detection model injects the time-frequency signal into the cable with the core and the metal shielding layer as the conductor medium. The signal will propagate between the core and the metal shielding layer in the form of electromagnetic waves. When a cable fault occurs, the signal will be reflected due to impedance mismatch, achieving the detection effect. However, during operation, the core has high electrical energy, and direct connection may cause damage to the equipment. Therefore, the above-mentioned time-frequency domain detection model cannot detect the running cable.

[0005] With respect to the above-mentioned technical problem that it is impossible to detect the outer sheath of a cable in operation, no effective solution has been proposed so far. Summary of the invention

[0006] The main purpose of the present invention is to provide a detection system and a detection method for a high-voltage cable outer sheath, so as to solve the technical problem that the detection method in the prior art cannot detect the outer sheath of a cable in operation.

[0007] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, there is provided a detection system for an outer sheath of a high-voltage cable, comprising: a signal generator, the signal generator is used to generate an incident signal; a high-frequency current transformer, the high-frequency current transformer is connected in series with the signal generator, and the high-frequency current transformer is used to be sleeved on the outside of at least two high-voltage cables to be tested; and a digital oscilloscope, the digital oscilloscope is electrically connected to the high-frequency current transformer and the signal generator, respectively.

[0008] Furthermore, the detection system also includes: a filter, and the filter is connected in series with the digital oscilloscope.

[0009] Furthermore, the passband of the high-frequency current transformer is BW, wherein 1 MHz≤BW≤100 MHz.

[0010] According to another aspect of the present invention, a detection method for an outer sheath of a high-voltage cable is provided. The detection method is performed using the above-mentioned detection system, and the detection method includes the following steps: a high-frequency current transformer is sleeved on the outside of two high-voltage cables to be tested; an incident signal is injected into the metal shielding layer of the high-voltage cable to be tested using the detection system so that an electromagnetic wave is formed between the two high-voltage cables to be tested, wherein the incident signal is a time-frequency domain signal; the incident signal and a reflected signal are received using the detection system, wherein the reflected signal is an electrical signal formed by the high-frequency current transformer under the action of the electromagnetic wave; and the damaged position of the high-voltage cable to be tested is analyzed according to the incident signal and the reflected signal.

[0011] Furthermore, according to the incident signal and the reflected signal, the damaged position of the high-voltage cable to be tested is analyzed, including: obtaining a WVD distribution model; inputting the incident signal and the reflected signal into the WVD distribution model respectively to obtain a first time-frequency domain energy distribution diagram corresponding to the incident signal and a second time-frequency domain energy distribution diagram corresponding to the reflected signal; according to the first time-frequency domain energy distribution diagram and the second time-frequency domain energy distribution diagram, the incident signal and the reflected signal are normalized to obtain a normalized correlation coefficient; according to the normalized correlation coefficient, a first receiving time of the reflected signal corresponding to the damaged point of the high-voltage cable to be tested is obtained; based on the electromagnetic wave velocity, the first receiving time and the second receiving time of the incident signal, the damaged position of the high-voltage cable to be tested is calculated.

[0012] Furthermore, according to the first time-frequency domain energy distribution diagram and the second time-frequency domain energy distribution diagram, the incident signal and the reflected signal are normalized to obtain a normalized correlation coefficient, including: according to the first time-frequency domain energy distribution diagram, the total energy of the incident signal is calculated in the time-frequency domain to obtain a first value; according to the second time-frequency domain energy distribution diagram, the total energy of the reflected signal is calculated in the time-frequency domain to obtain a second value; according to the first time-frequency domain energy distribution diagram and the second time-frequency domain energy distribution diagram, the product of the instantaneous energy of the incident signal and the reflected signal is calculated in the time-frequency domain to obtain a third value; the third value is divided by the product of the first value and the second value to obtain a fourth value; and the fourth value is numerically corrected to obtain a normalized correlation coefficient.

[0013] Furthermore, the first receiving time is the display time of the reflection signal corresponding to when the normalized correlation coefficient is 1.

[0014] Furthermore, based on the electromagnetic wave velocity, the first receiving time and the second receiving time of the incident signal, the damaged position of the high-voltage cable to be tested is calculated, including: calculating the time difference between the first receiving time and the second receiving time; calculating the product of the time difference and the electromagnetic wave velocity to obtain the distance between the damaged point of the high-voltage cable to be tested and the emission point of the incident signal.

[0015] Furthermore, before testing the high-voltage cable to be tested, it is necessary to determine whether the passband of the high-frequency current transformer meets the preset frequency range.

[0016] Furthermore, judging whether the passband of the high-frequency current transformer meets the preset frequency range includes: performing equivalent processing on the circuit of the high-frequency current transformer to obtain a corresponding equivalent circuit; calculating the lower limit frequency and the upper limit frequency of the equivalent circuit; comparing the difference between the lower limit frequency and the upper limit frequency with the preset frequency range to obtain a comparison result; judging whether the passband of the high-frequency current transformer meets the preset frequency range based on the comparison result.

[0017] By applying the technical solution of the present invention, the incident signal generated by the signal generator is an electrical signal, and the high-frequency current transformer is electrically connected to the signal generator, so that the current passes through the mutual inductance coil on the high-frequency current transformer, and the space around the mutual inductance coil will generate a magnetic field; when the high-frequency current transformer is sleeved on the outside of at least two high-voltage cables to be tested, current will pass through the metal shielding layer of each high-voltage cable to be tested, and a magnetic field will be generated around the metal shielding layer, and the generated magnetic field will induce an electric field. The changes in the electric field and the magnetic field are continuously and alternately produced to form electromagnetic waves. The electromagnetic waves are located between the metal shielding layers. The outer sheath of the high-voltage cable to be tested serves as a propagation medium for the electromagnetic waves, so that the electromagnetic waves propagate along the length direction of the high-voltage cable to be tested. When the outer sheath is damaged, the propagation medium of the electromagnetic waves changes, thereby causing the electromagnetic waves to be emitted; the digital oscilloscope is used to measure the incident signal generated by the signal generator and the reflected signal generated by the change of the electromagnetic wave. In the above scheme, the detection system has no contact with the high-voltage cable to be tested, and can inject the incident signal into the metal shielding layer of the high-voltage cable to be tested, avoiding the high-power core, and thus can perform outer sheath detection on the running high-voltage cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0019] Figure 1 The schematic diagram of the structure of the detection system in the present invention is shown;

[0020] Figure 2 A schematic flow chart of the detection method of the present invention is shown.

[0021] The above drawings include the following reference numerals:

[0022] 1. Signal generator;

[0023] 2. High frequency current transformer;

[0024] 3. Digital oscilloscope;

[0025] 4. Filter;

[0026] 5. High voltage cable to be tested. DETAILED DESCRIPTION

[0027] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0028] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0029] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0030] Now, exemplary embodiments according to the present application will be described in more detail with reference to the accompanying drawings. However, these exemplary embodiments may be implemented in a variety of different forms and should not be construed as being limited to the embodiments described herein. It should be understood that these embodiments are provided to make the disclosure of the present application thorough and complete, and to fully convey the concepts of these exemplary embodiments to those of ordinary skill in the art. In the accompanying drawings, for the sake of clarity, the thickness of the layers and regions may be enlarged, and the same reference numerals are used to represent the same devices, and thus their descriptions will be omitted.

[0031] Combination Figure 1 As shown, according to a specific embodiment of the present application, a detection system for an outer sheath of a high-voltage cable is provided.

[0032] Specifically, the detection system includes: a signal generator 1, a high-frequency current transformer 2 and a digital oscilloscope 3. The signal generator 1 is used to generate an incident signal, the high-frequency current transformer 2 is connected in series with the signal generator 1, the high-frequency current transformer 2 is used to be sleeved on the outside of at least two high-voltage cables 5 to be tested, and the digital oscilloscope 3 is electrically connected to the high-frequency current transformer 2 and the signal generator 1 respectively.

[0033] In the embodiment of the present application, the incident signal generated by the signal generator 1 is an electrical signal, and the high-frequency current transformer 2 is electrically connected to the signal generator 1, so that the current passes through the mutual inductance coil on the high-frequency current transformer 2, and a magnetic field will be generated in the space around the mutual inductance coil; when the high-frequency current transformer 2 is sleeved on the outside of at least two high-voltage cables 5 to be tested, current will pass through the metal shielding layer of each high-voltage cable 5 to be tested, and a magnetic field will be generated around the metal shielding layer, and the generated magnetic field will induce an electric field. The changes in the electric field and the magnetic field are constantly alternating to form electromagnetic waves. The electromagnetic waves are located between the metal shielding layers. The outer sheath of the high-voltage cable 5 to be tested serves as a propagation medium for the electromagnetic waves, so that the electromagnetic waves propagate along the length direction of the high-voltage cable 5 to be tested. When the outer sheath is damaged, the propagation medium of the electromagnetic waves changes, which leads to the emission of electromagnetic waves; the digital oscilloscope 3 is used to measure the incident signal generated by the signal generator 1 and the reflected signal generated by the change of the electromagnetic wave. In the above scheme, the detection system has no contact with the high-voltage cable 5 to be tested, and can inject the incident signal into the metal shielding layer of the high-voltage cable 5 to be tested, avoiding the high-power core, thereby being able to perform outer sheath detection on the running high-voltage cable.

[0034] Furthermore, the detection system further comprises a filter 4, which is connected in series with the digital oscilloscope 3. The setting of the filter 4 can filter out the electrical signal induced in the outer sheath of the charged high-voltage cable 5 to be tested, thereby making the measured reflected signal more accurate.

[0035] In the embodiment of the present application, the frequency of the electrical signal induced in the outer sheath of the energized high-voltage cable 5 to be tested is 50Hz. In order to ensure that the reflected signal received by the digital oscilloscope 3 is more effective, the focus is mainly on the reflected signal generated by the characteristic impedance change caused by the damage of the outer sheath. Among them, the cutoff frequency of the filter 4 can be selected between 50Hz-950kHz, ensuring that the signal between 1MHz and 100MHz is retained, while shielding the low-frequency interference signal.

[0036] Furthermore, the passband of the high-frequency current transformer 2 is BW, wherein 1 MHz≤BW≤100 MHz.

[0037] In the embodiment of the present application, the frequency of the incident signal generated by the signal generator 1 is between 1 MHz and 100 MHz. In order to inject the incident signal into the metal shielding layer of the high-voltage cable 5 to be tested, the frequency range of the passband of the high-frequency current transformer 2 is between 1 MHz and 100 MHz.

[0038] Combination Figure 2 As shown, according to another specific embodiment of the present application, a method for detecting an outer sheath of a high-voltage cable is provided.

[0039] Specifically, the detection method for the outer sheath of the high-voltage cable is to use the above detection system for detection, and the detection method includes the following steps:

[0040] Step S1: The high-frequency current transformer 2 is mounted outside two high-voltage cables 5 to be tested.

[0041] Step S2: using the detection system to inject an incident signal onto the metal shielding layer of the high-voltage cable 5 to be tested, so as to form an electromagnetic wave between the two high-voltage cables 5 to be tested, wherein the incident signal is a time-frequency domain signal.

[0042] Step S3: using a detection system to receive an incident signal and a reflected signal, wherein the reflected signal is an electrical signal generated by the high-frequency current transformer 2 under the action of electromagnetic waves.

[0043] Step S4: Analyze the damaged position of the high-voltage cable 5 to be tested according to the incident signal and the reflected signal.

[0044] In the embodiment of the present application, the incident signal is injected into the metal shielding layer of the high-voltage cable 5 to be tested, and a magnetic field is generated around the metal shielding layer, and the generated magnetic field will induce an electric field. The changes in the electric field and the magnetic field are constantly alternating to form electromagnetic waves. The electromagnetic waves are located between the metal shielding layers. The outer sheath of the high-voltage cable 5 to be tested serves as the propagation medium of the electromagnetic waves, so that the electromagnetic waves propagate along the length direction of the high-voltage cable 5 to be tested. When the outer sheath is damaged, the propagation medium of the electromagnetic waves changes, which leads to the emission of electromagnetic waves; under the action of the electromagnetic waves, the mutual inductance coil of the high-frequency current transformer 2 may generate a corresponding current, that is, the reflected signal generated by the change of the electromagnetic wave is injected into the mutual inductance coil of the high-frequency current transformer 2, and then the reflected signal is measured. In the above scheme, the detection system has no contact with the high-voltage cable 5 to be tested, and can inject the incident signal into the metal shielding layer of the high-voltage cable 5 to be tested, avoiding the high-power core, and then the outer sheath detection of the high-voltage cable in operation can be performed.

[0045] It should be noted that the high-voltage cable 5 to be tested includes a wire core, an insulating layer, a metal shielding layer and an outer sheath, and the wire core, the insulating layer, the metal shielding layer and the outer sheath are arranged in sequence from the inside to the outside.

[0046] In step S4, the damaged position of the high-voltage cable 5 to be tested is analyzed according to the incident signal and the reflected signal, including the following steps:

[0047] Step S41: Obtain the WVD distribution model.

[0048] Specifically, the WVD distribution model is a Fourier transform model of the instantaneous correlation function of the signal, which reflects the instantaneous time-frequency relationship of the signal.

[0049] Step S42: inputting the incident signal and the reflected signal into the WVD distribution model respectively to obtain a first time-frequency domain energy distribution diagram corresponding to the incident signal and a second time-frequency domain energy distribution diagram corresponding to the reflected signal.

[0050] Step S43: performing normalization processing on the incident signal and the reflected signal according to the first time-frequency domain energy distribution diagram and the second time-frequency domain energy distribution diagram to obtain a normalized correlation coefficient.

[0051] Step S44: according to the normalized correlation coefficient, the first receiving time of the reflected signal corresponding to the damaged point of the high-voltage cable 5 to be tested is obtained.

[0052] Step S45: Calculate the damage position of the high-voltage cable 5 to be tested based on the electromagnetic wave velocity, the first receiving time and the second receiving time of the incident signal.

[0053] Through the above steps S41 to S45, the incident signal and the reflected signal are processed using the WVD distribution model, and a normalized correlation coefficient related to the incident signal and the reflected signal is established. The normalized correlation coefficient is used to intuitively reflect whether the outer sheath of the high-voltage cable 5 to be tested is damaged and the receiving time of the incident signal, thereby accurately locating the damaged point of the high-voltage cable 5 to be tested.

[0054] In step S43, according to the first time-frequency domain energy distribution diagram and the second time-frequency domain energy distribution diagram, the incident signal and the reflected signal are normalized to obtain a normalized correlation coefficient, including the following steps:

[0055] Step S431: According to the first time-frequency domain energy distribution diagram, the total energy of the incident signal is calculated in the time-frequency domain to obtain a first value.

[0056] Specifically, the total energy of the incident signal is calculated as: E s =∫∫W r (t, ω)dωdt, where E s is the total energy of the incident signal (i.e., the first value), W r (t, ω) is the instantaneous energy of the incident signal.

[0057] Step S432: Calculate the total energy of the reflected signal in the time-frequency domain according to the second time-frequency domain energy distribution diagram to obtain a second value.

[0058] Specifically, the total energy of the reflected signal is calculated as: E r =∫∫W r (t-τ, ω)dωdt, where E r is the total energy of the reflected signal (i.e., the second value), W r (t-τ, ω) is the instantaneous energy of the reflected signal.

[0059] Step S433: Calculate the product of the instantaneous energy of the incident signal and the reflected signal in the time-frequency domain according to the first time-frequency domain energy distribution diagram and the second time-frequency domain energy distribution diagram to obtain a third value.

[0060] Specifically, the calculation formula of the third value is: C1 = ∫∫W r (t,ω)W r (t-τ, ω)dωdt, where C1 is the third value.

[0061] Step S434: Calculate the quotient of the third value and the product of the first value and the second value to obtain a fourth value.

[0062] Specifically, the calculation formula of the fourth value is: Among them, C2 is the fourth value.

[0063] Step S435: Perform numerical correction on the fourth value to obtain a normalized correlation coefficient.

[0064] Specifically, let the value range of the fourth value C2 be [0, 1], and it is necessary to set a constant C3 to perform numerical correction on the fourth value, and the corrected fourth value is the normalized correlation coefficient.

[0065] Among them, the calculation formula of the normalized correlation coefficient is: C sr is the normalized correlation coefficient.

[0066] Furthermore, the first receiving time is the display time of the reflection signal corresponding to when the normalized correlation coefficient is 1.

[0067] It should be noted that, when the outer sheath of the high-voltage cable 5 to be tested is damaged, the propagation medium of the electromagnetic wave changes, thereby causing the electromagnetic wave to be emitted, wherein the larger the reflected signal, the greater the possibility that the outer sheath is damaged. When the outer sheath of the high-voltage cable 5 to be tested is not damaged, the propagation medium of the electromagnetic wave does not change, thereby causing the electromagnetic wave to not be emitted, that is, the reflected signal is 0.

[0068] When the normalized correlation coefficient is 1, the larger the value of the reflected signal is, the more it indicates that the signal received by the oscilloscope at this moment is a reflected signal.

[0069] In step S45, based on the electromagnetic wave velocity, the first receiving time and the second receiving time of the incident signal, calculating the damage position of the high-voltage cable 5 to be tested includes the following steps:

[0070] Step S451: Calculate the time difference between the first receiving time and the second receiving time.

[0071] Specifically, when the normalized correlation coefficient is 1, the corresponding time is the first receiving time t of the incident signal, and the second receiving time of the incident signal is t0, wherein the second receiving time is defined as the zero point, that is, the time difference between the first receiving time and the second receiving time is t.

[0072] Step S452: Calculate the product of the time difference and the electromagnetic wave velocity to obtain the distance between the damaged point of the high-voltage cable 5 to be tested and the emission point of the incident signal.

[0073] It should be noted that the time for the electromagnetic wave to be transmitted from the incident point to the reflection point (the damaged point of the outer sheath) is t / 2, the electromagnetic wave velocity is v, and the distance between the damaged point of the high-voltage cable 5 to be tested and the emission point of the incident signal is S, where:

[0074] Furthermore, before testing the high-voltage cable 5 to be tested, it is necessary to determine whether the passband of the high-frequency current transformer 2 meets the preset frequency range.

[0075] Specifically, the passband of the high-frequency current transformer 2 is within the frequency range of the incident signal, so that the incident signal can be injected into the metal shielding layer of the high-voltage cable 5 to be tested through the high-frequency current transformer 2 .

[0076] Further, judging whether the passband of the high-frequency current transformer 2 meets the preset frequency range includes the following steps:

[0077] Step S01: Perform equivalent processing on the circuit of the high-frequency current transformer 2 to obtain a corresponding equivalent circuit.

[0078] Specifically, in the equivalent circuit, the equivalent resistance of the mutual inductance coil is R s , the equivalent inductance of the mutual inductance coil is L s , the equivalent capacitance of the mutual inductance coil is C s , the load equivalent resistance connected to the mutual inductance coil is R, wherein the load equivalent resistance is the resistance of the high-voltage cable 5 to be tested acting on the mutual inductance coil.

[0079] Step S02: Calculate the lower limit frequency and the upper limit frequency of the equivalent circuit.

[0080] Specifically, the lower limit frequency f L The calculation formula is:

[0081] Upper frequency f H The calculation formula is:

[0082] Step S03: Compare the difference between the lower limit frequency and the upper limit frequency with a preset frequency range to obtain a comparison result.

[0083] Specifically, the passband of the high-frequency current transformer 2 is BW, and the BW value is compared with the preset frequency range, wherein the calculation formula of BW is: BW=f H -f L .

[0084] Step S04: judging whether the passband of the high-frequency current transformer 2 meets the preset frequency range according to the comparison result.

[0085] Specifically, if the BW value is within the preset frequency range, the selection of the high-frequency current transformer 2 meets the requirements.

[0086] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0087] The incident signal generated by the signal generator 1 is an electrical signal. The high-frequency current transformer 2 is electrically connected to the signal generator 1, so that the current passes through the mutual inductance coil on the high-frequency current transformer 2, and a magnetic field will be generated in the space around the mutual inductance coil; when the high-frequency current transformer 2 is set on the outside of at least two high-voltage cables 5 to be tested, current will pass through the metal shielding layer of each high-voltage cable 5 to be tested, and a magnetic field will be generated around the metal shielding layer. The generated magnetic field will induce an electric field. The changes in the electric field and the magnetic field are constantly alternating to form electromagnetic waves. The electromagnetic waves are located between the metal shielding layers. The outer sheath of the high-voltage cable 5 to be tested serves as a propagation medium for the electromagnetic waves, so that the electromagnetic waves propagate along the length direction of the high-voltage cable 5 to be tested. When the outer sheath is damaged, the propagation medium of the electromagnetic waves changes, which leads to the emission of electromagnetic waves; the digital oscilloscope 3 is used to measure the incident signal generated by the signal generator 1 and the reflected signal generated by the change of the electromagnetic wave. In the above scheme, the detection system has no contact with the high-voltage cable 5 to be tested, and can inject the incident signal into the metal shielding layer of the high-voltage cable 5 to be tested, avoiding the high-power core, thereby being able to perform outer sheath detection on the running high-voltage cable.

[0088] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0089] In addition to the above, it should be noted that "one embodiment", "another embodiment", "embodiment", etc. mentioned in this specification refer to the specific features, structures or characteristics described in conjunction with the embodiment included in at least one embodiment generally described in this application. The same expression appearing in multiple places in the specification does not necessarily refer to the same embodiment. Further, when describing a specific feature, structure or characteristic in conjunction with any embodiment, it is claimed that the realization of such feature, structure or characteristic in conjunction with other embodiments also falls within the scope of the present invention.

[0090] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A detection system for a high voltage cable outer sheath, characterized in that: include: A signal generator (1), the signal generator (1) being used to generate an incident signal; A high-frequency current transformer (2), the high-frequency current transformer (2) being connected in series with the signal generator (1), and the high-frequency current transformer (2) being used for being sleeved on the outside of at least two high-voltage cables (5) to be tested; A digital oscilloscope (3), wherein the digital oscilloscope (3) is electrically connected to the high-frequency current transformer (2) and the signal generator (1) respectively.

2. The detection system according to claim 1, characterized in that: The detection system also includes: A filter (4), wherein the filter (4) is connected in series with the digital oscilloscope (3).

3. The detection system according to claim 1, characterized in that: The passband of the high-frequency current transformer (2) is BW, wherein 1 MHz≤BW≤100 MHz.

4. A method for detecting an outer sheath of a high voltage cable, characterized in that: The detection method is performed using the detection system according to any one of claims 1 to 3, and the detection method comprises the following steps: The high-frequency current transformer (2) is sleeved outside the two high-voltage cables (5) to be tested; Using the detection system to inject an incident signal onto the metal shielding layer of the high-voltage cable (5) to be tested, so that an electromagnetic wave is formed between the two high-voltage cables (5) to be tested, wherein the incident signal is a time-frequency domain signal; Using the detection system to receive the incident signal and the reflected signal, wherein the reflected signal is an electrical signal generated by the high-frequency current transformer (2) under the action of the electromagnetic wave; The damaged position of the high-voltage cable (5) to be tested is analyzed according to the incident signal and the reflected signal.

5. The detection method according to claim 4, characterized in that: Analyzing the damaged position of the high-voltage cable (5) to be tested according to the incident signal and the reflected signal, comprising: Get the WVD distribution model; Inputting the incident signal and the reflected signal into the WVD distribution model respectively to obtain a first time-frequency domain energy distribution diagram corresponding to the incident signal and a second time-frequency domain energy distribution diagram corresponding to the reflected signal; According to the first time-frequency domain energy distribution diagram and the second time-frequency domain energy distribution diagram, normalizing the incident signal and the reflected signal to obtain a normalized correlation coefficient; According to the normalized correlation coefficient, a first receiving time of a reflected signal corresponding to a damaged point of the high-voltage cable (5) to be tested is obtained; Based on the electromagnetic wave velocity, the first receiving time and the second receiving time of the incident signal, the damaged position of the high-voltage cable (5) to be tested is calculated.

6. The detection method according to claim 5, characterized in that: According to the first time-frequency domain energy distribution diagram and the second time-frequency domain energy distribution diagram, the incident signal and the reflected signal are normalized to obtain a normalized correlation coefficient, including: Calculating the total energy of the incident signal in the time-frequency domain according to the first time-frequency domain energy distribution diagram to obtain a first value; Calculating the total energy of the reflected signal in the time-frequency domain according to the second time-frequency domain energy distribution diagram to obtain a second value; Calculating the product of the instantaneous energy of the incident signal and the reflected signal in the time-frequency domain according to the first time-frequency domain energy distribution diagram and the second time-frequency domain energy distribution diagram to obtain a third value; The third value is divided by the product of the first value and the second value to obtain a fourth value; The fourth value is numerically corrected to obtain the normalized correlation coefficient.

7. The detection method according to claim 6, characterized in that: The first receiving time is the display time of the reflected signal corresponding to when the normalized correlation coefficient is 1.

8. The detection method according to claim 7, characterized in that: Calculating the damaged position of the high-voltage cable (5) to be tested based on the electromagnetic wave velocity, the first receiving time and the second receiving time of the incident signal comprises: Calculate the time difference between the first receiving time and the second receiving time; The product of the time difference and the wave velocity of the electromagnetic wave is calculated to obtain the distance between the damaged point of the high-voltage cable (5) to be tested and the emission point of the incident signal.

9. The detection method according to claim 4, characterized in that: Before testing the high-voltage cable (5) to be tested, it is necessary to determine whether the passband of the high-frequency current transformer (2) conforms to a preset frequency range.

10. The detection method according to claim 9, characterized in that: Determining whether the passband of the high-frequency current transformer (2) meets a preset frequency range includes: Performing equivalent processing on the circuit of the high-frequency current transformer (2) to obtain a corresponding equivalent circuit; Calculating a lower frequency limit and an upper frequency limit of the equivalent circuit; Compare the difference between the lower frequency limit and the upper frequency limit with the preset frequency range to obtain a comparison result; According to the comparison result, it is determined whether the passband of the high-frequency current transformer (2) meets the preset frequency range.

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