Harmonic leakage-based distribution cable insulation aging detection method and device

Abstract

The invention provides a distribution cable insulation aging detection method based on harmonic leakage, and the method comprises the steps: obtaining the magnetic induction intensity generated by the leakage harmonic current outside a detected distribution cable at a plurality of node positions of the distribution cable, and determining the harmonic leakage current at each node position; obtaining corresponding common-mode harmonic components and differential-mode harmonic components under a plurality of preselected harmonic angular frequencies; equivalent capacitance parameters of the power distribution cable insulation under the harmonic angular frequencies are calculated respectively, and the aging degree of the power distribution cable insulation is determined based on the variable quantity of the equivalent capacitance parameters under the harmonic angular frequencies; and carrying out comparative analysis on the differential mode harmonic components at different node positions, and determining the node position of which the amplitude is abnormally increased as the node position corresponding to the insulation aging defect of the distribution cable. According to the method, on-line monitoring, quantitative evaluation and defect positioning of the insulation aging state of the power distribution cable can be realized under the electrified operation condition, and the monitoring accuracy and reliability are improved.

Description

Technical Field

[0001] This invention belongs to the field of cable insulation monitoring technology, and in particular relates to a method and device for detecting the aging of insulation in distribution cables based on harmonic leakage. Background Technology

[0002] With the continuous advancement of new power systems and distribution networks, the proportion of new energy power generation equipment, power electronic conversion devices, and various nonlinear loads connected to distribution networks is constantly increasing, leading to a significant increase in harmonic content in the operating environment of distribution systems. Harmonic currents in distribution cables not only cause voltage distortion and additional losses during operation, but also generate additional electric and thermal stresses in the cable insulation structure, accelerating the dielectric aging process of the insulation material. This, in turn, induces insulation breakdown, leakage current, and grounding faults, adversely affecting the safety, reliability, and power supply continuity of the distribution system. Statistical data shows that a considerable portion of distribution cable faults are closely related to insulation aging, which is typically characterized by strong concealment, long development cycles, and indistinct early characteristics, posing significant challenges to operation and maintenance management.

[0003] Currently, the main techniques for monitoring the insulation condition of power distribution cables include insulation resistance measurement, withstand voltage testing, partial discharge detection, and dielectric loss tangent measurement. Among these, insulation resistance measurement and withstand voltage testing are offline methods that must be performed under power outage conditions. This not only affects normal power supply but may also cause additional damage to the cable insulation due to high electrical stress testing. Consequently, these methods are insufficient to meet the real-time monitoring requirements of power distribution systems operating online and have limited ability to identify early latent insulation aging.

[0004] While partial discharge detection technology can reflect some insulation defect characteristics, high-frequency signals attenuate significantly during propagation in distribution cables. This typically requires multi-point distributed measurements, resulting in complex and costly systems that are susceptible to electromagnetic interference, leading to significant risks of misjudgment and missed detection. Furthermore, its effectiveness in identifying minor aging or moisture-induced defects is limited. The dielectric loss tangent measurement method requires high-precision testing environments. Since the change in dielectric loss parameters during insulation aging is relatively small, measurement errors can easily amplify assessment biases. Moreover, it often relies on analysis based on a single electrical parameter, making it difficult to comprehensively reflect the insulation aging state under the combined effects of multiple factors.

[0005] In summary, existing power distribution cable insulation monitoring technologies still have shortcomings in terms of linearity, sensitivity, anti-interference ability, and quantitative assessment of aging, making it difficult to meet the needs of new power systems for power distribution cable status perception and refined operation and maintenance. Summary of the Invention

[0006] The purpose of this invention is to provide a method and device for detecting the aging of power distribution cable insulation based on harmonic leakage, which can realize online monitoring, quantitative assessment and defect location of the aging state of power distribution cable insulation under energized operation conditions, thereby improving the accuracy and reliability of monitoring.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for detecting the aging of insulation in power distribution cables based on harmonic leakage, comprising: At multiple node locations of the power distribution cable, the magnetic induction intensity signal generated by the leakage harmonic current outside the power distribution cable under test is acquired, and the harmonic leakage current signal at each node location is determined based on the magnetic induction intensity signal. Based on the harmonic leakage current signal at each node location, the corresponding common-mode harmonic components and differential-mode harmonic components are obtained at multiple pre-selected harmonic angular frequencies. Based on the frequency domain calculation correspondence between common-mode harmonic components and equivalent parameters of power distribution cable insulation, the equivalent capacitance parameters of power distribution cable insulation at each harmonic angular frequency are calculated, and the aging degree of power distribution cable insulation is determined based on the change of the equivalent capacitance parameters at each harmonic angular frequency. At each harmonic angular frequency, a lateral comparative analysis is performed on the differential mode harmonic components at different node locations. The node locations where the amplitude of the differential mode harmonic components shows an abnormal increase are identified as the node locations corresponding to the insulation aging defects of the power distribution cable.

[0008] Furthermore, the step of determining the harmonic leakage current signal at each node location based on the magnetic induction intensity signal includes: According to the nodes of the power distribution cable The calculation node for the magnetic field response signal generated by the harmonic leakage current, and the linear relationship expression between the magnetic field response signal and the harmonic leakage current. Harmonic leakage current at the location The linear relationship expression is as follows:

[0009] in, and Based on the preset parameters determined by the experiment, For nodes Located at harmonic angular frequency The magnetic induction intensity below, For nodes Located at harmonic angular frequency Harmonic leakage current.

[0010] Furthermore, obtaining the corresponding common-mode harmonic components and differential-mode harmonic components based on the harmonic leakage current signals at each node location at multiple pre-selected harmonic angular frequencies includes: At harmonic angular frequency At this point, calculate the node according to the following formula. Common-mode harmonic components and difference-mode harmonic components at:

[0011]

[0012]

[0013]

[0014] in, For nodes Located at harmonic angular frequency Harmonic leakage current below, and They are nodes At the harmonic angular frequency Common-mode harmonic components and difference-mode harmonic components, and They are nodes At the harmonic angular frequency The common-mode voltage harmonic components and differential-mode voltage harmonic components to ground under the following conditions. The modal variation coefficient between the common mode and the difference mode. For the insulation of the power distribution cable at the harmonic angular frequency The equivalent capacitance parameters are as follows. The harmonic angular frequency, It is the imaginary unit.

[0015] Furthermore, the step of determining the degree of aging of the power distribution cable insulation includes: Based on the frequency domain relationship between the common-mode harmonic components and the corresponding common-mode ground voltage harmonic components, the insulation of the power distribution cable at each of the aforementioned harmonic angular frequencies is calculated. Equivalent capacitance parameters under the following conditions The frequency domain calculation relationship is as follows:

[0016] The change in equivalent capacitance parameters is determined based on the change in equivalent capacitance parameters with harmonic angular frequency. And based on the change in the equivalent capacitance parameter Determine the overall aging degree of the insulation of the power distribution cable.

[0017] Furthermore, the step of determining the node location corresponding to the insulation aging defect of the power distribution cable includes: Under the same harmonic angular frequency condition, the amplitude of the differential mode harmonic component at different node locations along the power distribution cable is compared laterally. When the amplitude of the differential mode harmonic component at a certain node location increases significantly relative to the adjacent node locations or other node locations, or when a significant local maximum is formed in the amplitude distribution of the differential mode harmonic component at each node location along the power distribution cable, the node location is determined to be an abnormal node for the differential mode harmonic component. The abnormal nodes of the differential mode harmonic components are identified as the node locations corresponding to the aging or defects in the insulation of the power distribution cable.

[0018] Furthermore, methods for detecting aging insulation in distribution cables based on harmonic leakage also include: At the node location corresponding to the determined insulation aging defect of the power distribution cable, the amplitude distribution of the common-mode harmonic voltage component and the differential-mode harmonic voltage component at multiple harmonic angular frequencies is obtained. Based on the voltage withstand mode corresponding to different insulation structure types at the node location, at least one of the common-mode harmonic voltage component and the differential-mode harmonic voltage component is selected as the harmonic voltage amplitude acting on the corresponding insulation structure. ; The AC electric stress borne by the insulation structure at the node location is calculated based on the following formula. :

[0019] in, The electric field conversion factor is the one corresponding to the insulation structure type. ; Based on the AC electric stress The aging life of the insulation structure at the node location is evaluated based on the following electrical aging life model for insulation materials:

[0020] in, For the electrical aging life of insulating materials, and These are the lifetime model parameters determined through accelerated aging tests on insulating materials. In the calculation of the electrical aging life of the above-mentioned power distribution cable insulation, the electrical aging life is... Performing a logarithmic transformation, we obtain: ,in, , , .

[0021] Furthermore, the step of acquiring the magnetic induction intensity signal generated by the leakage harmonic current at multiple node locations of the power distribution cable includes: The magnetic induction intensity signal generated by leakage harmonic current is acquired by a dual magnetic core sensing device installed on the outside of the power distribution cable. The dual magnetic core sensing device includes an inner magnetic core and an outer magnetic core arranged coaxially along the radial direction of the power distribution cable. The inner magnetic core is used to suppress the magnetic field influence generated by the normal load current of the power distribution cable, and the outer magnetic core is used to sense the magnetic induction intensity signal generated by leakage harmonic current. The magnetic induction intensity measurement bandwidth corresponding to the outer magnetic core covers 10Hz to 20kHz, and the detection sensitivity to harmonic leakage current is not less than 1mA.

[0022] In a second aspect, the present invention provides a device for detecting the aging of power distribution cable insulation based on harmonic leakage, comprising: The magnetic field acquisition module is used to acquire the magnetic induction intensity signal generated by leakage harmonic current on the exterior of the power distribution cable at multiple node locations. The harmonic leakage current calculation module is used to determine the harmonic leakage current signal at each node location based on the magnetic induction intensity signal. The modal component extraction module is used to obtain the corresponding common-mode harmonic components and differential-mode harmonic components at multiple pre-selected harmonic angular frequencies based on the harmonic leakage current signal at each node location. The aging degree assessment module is used to calculate the equivalent capacitance parameters of the power distribution cable insulation at each harmonic angular frequency based on the frequency domain calculation correspondence between the common mode harmonic components and the equivalent parameters of the power distribution cable insulation, and to determine the aging degree of the power distribution cable insulation based on the change of the equivalent capacitance parameters at each harmonic angular frequency. The aging location module is used to perform a lateral comparative analysis of the differential mode harmonic components at different node locations under each of the harmonic angular frequencies, and to determine the node location where the amplitude of the differential mode harmonic components increases abnormally as the node location corresponding to the aging defect of the power distribution cable insulation.

[0023] In a third aspect, the present invention provides an electronic device including a processor and a memory, the processor being configured to execute a computer program stored in the memory to implement the aforementioned method for detecting aging insulation of power distribution cables based on harmonic leakage.

[0024] In a fourth aspect, the present invention provides a computer-readable storage medium storing at least one instruction that, when executed by a processor, implements the aforementioned method for detecting aging insulation of power distribution cables based on harmonic leakage.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention acquires magnetic induction intensity signals generated by harmonic leakage current at multiple nodes of a power distribution cable, and decomposes them at multiple harmonic angular frequencies to obtain common-mode and differential-mode harmonic components. It establishes a frequency domain correspondence between the harmonic mode components and the equivalent parameters of the power distribution cable insulation, enabling online quantitative assessment of the insulation aging degree and precise location of aging defect nodes. Compared to traditional monitoring methods that can only qualitatively determine the insulation condition, this invention can simultaneously assess the aging degree and identify defect locations under energized operating conditions, improving the accuracy and practicality of power distribution cable insulation condition monitoring.

[0026] 2. This invention utilizes the linear relationship between magnetic induction intensity and harmonic leakage current to convert externally measurable magnetic field signals into harmonic leakage current signals at nodes. Furthermore, it calculates common-mode and differential-mode harmonic components along the harmonic angular frequency dimension, quantifying insulation aging information as equivalent capacitance parameters. The common-mode harmonic components characterize the overall insulation aging level of the distribution cable, while the differential-mode harmonic components characterize the symmetrical damage characteristics of local insulation defects. Through lateral comparative analysis of differential-mode harmonic components at different node locations, accurate identification of aging defect nodes is achieved, thus balancing overall aging assessment with local defect location capabilities.

[0027] 3. This invention further integrates a dual-core sensing device to effectively suppress the magnetic field of normal load current, improving the signal-to-noise ratio of harmonic leakage current detection. Based on this, an insulation electrical aging life model is introduced, converting common-mode and differential-mode harmonic voltage components into AC electrical stress borne by the insulation structure, enabling the assessment of the aging life of different insulation structure types. This scheme not only reflects the current insulation aging state of distribution cables but also predicts their remaining life, providing a quantitative basis for condition-based maintenance and refined operation of distribution cables, improving operational reliability and reducing maintenance costs. Attached Figure Description

[0028] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the aging detection method for power distribution cable insulation based on harmonic leakage according to an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the principle of power distribution cable insulation monitoring based on harmonic multimode in an embodiment of the present invention. Figure 3 This is a schematic diagram of the finite element simulation results of the differential mode leakage current based on the power distribution cable structure in an embodiment of the present invention; Figure 4 This is a schematic diagram of the analytical results of magnetic induction intensity in an embodiment of the present invention; Figure 5 This is a schematic diagram of the process for assessing the impact of aging on the insulation of power distribution cables according to an embodiment of the present invention; Figure 6 This is a schematic diagram of a power distribution cable insulation aging detection device based on harmonic leakage according to an embodiment of the present invention; Figure 7 A structural block diagram of an electronic device according to an embodiment of the present invention. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0030] The following detailed description is exemplary and intended to provide further detailed explanation of the invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention.

[0031] Example 1 like Figure 1 As shown, this embodiment provides a method for detecting the insulation aging of distribution cables based on harmonic leakage, including steps S1 to S4. This method addresses the characteristics of harmonic leakage current caused by defects such as insulation aging and moisture during the operation of distribution cables. It combines the propagation characteristics of harmonic common modes and differential modes with broadband mode transfer function modeling to achieve online assessment of the degree of cable insulation aging and location of aging defects. The magnetic induction intensity signal generated by leakage harmonic current is acquired by a dual-core sensing device installed on the outside of the power distribution cable. The dual-core sensing device includes an inner core and an outer core arranged coaxially along the radial direction of the power distribution cable. The inner core is used to suppress the magnetic field influence generated by the normal load current of the power distribution cable, and the outer core is used to sense the magnetic induction intensity signal generated by leakage harmonic current. The magnetic induction intensity measurement bandwidth corresponding to the outer core covers 10 Hz to 20 kHz, and the detection sensitivity for harmonic leakage current is not less than 1 mA. Furthermore, the dual-core sensing device meets the requirements for harmonic leakage current measurement of 0–400 A load current, 1–30 mA range, 1 mA sensitivity, and 100 kHz bandwidth.

[0032] In step S1, magnetic induction intensity signals generated by leakage harmonic currents outside the tested power distribution cable are acquired at multiple node locations. The harmonic leakage current signal at each node location is then determined based on these magnetic induction intensity signals. Specifically, multiple node locations (hereinafter referred to as nodes) are selected along the power distribution cable. (Representing any node position), magnetic induction intensity signals are collected at each node position using the dual-core sensing device. To obtain harmonic characteristic parameters for subsequent modal analysis and modeling, the collected magnetic induction intensity signals or their corresponding current signals can be processed, including filtering to suppress environmental noise and normal load current interference, and frequency domain analysis is performed on the filtered signals to extract the component amplitude and phase information at different harmonic angular frequencies. Furthermore, characteristic parameters such as harmonic amplitude, phase shift, and harmonic distortion rate can be extracted for subsequent evaluation. Node The magnetic field response signal generated by the harmonic leakage current and the harmonic leakage current satisfy a linear relationship expression. The node is calculated using this linear relationship expression. Located at harmonic angular frequency Harmonic leakage current The linear relationship expression is as follows:

[0033] in, and Based on the preset parameters determined by the experiment, For nodes Located at harmonic angular frequency The magnetic induction intensity below, For nodes Located at harmonic angular frequency The harmonic leakage current below. k 1 = 0.2332, k 2 = 2.164 × 10, the variance of the fitting residual of the linear relationship is 2.710 × 10, which is used to characterize the fitting accuracy of the linear mapping relationship between magnetic induction intensity and harmonic leakage current.

[0034] like Figure 2 As shown, a test voltage is injected into a power distribution cable under controlled voltage source excitation. This injected voltage forms voltage, current, and harmonic components propagating along the transmission direction within the cable. During operation, the cable's insulation system, voltage distribution, harmonic components, and AC load all contribute to the formation and transmission of electrical quantities. The cable's insulation system includes ground insulation, interlayer insulation, and interlayer metal insulation. Different insulation structures exhibit different electrical response characteristics under harmonic excitation.

[0035] Under harmonic excitation conditions, the voltage and current signals inside the cable can be decomposed into common-mode components and differential-mode components. The common-mode components mainly reflect the symmetrical coupling characteristics between the conductor and the ground, while the differential-mode components mainly reflect the anti-symmetrical coupling characteristics between the conductors. The common-mode and differential-mode signals, after being combined by the distribution cable and its insulation system, form a broadband electrical response related to the insulation equivalent parameters.

[0036] Based on voltage, current, and harmonic information collected at different node locations of the power distribution cable, a broadband mode transfer function (MTF) is constructed to describe the propagation characteristics of harmonic signals in the power distribution cable. This broadband MTF is not an independent detection object, but rather a frequency domain representation of the correspondence between harmonic leakage current, common-mode harmonic components, differential-mode harmonic components, and the equivalent insulation parameters of the power distribution cable. It reflects the propagation characteristics of harmonic signals along each node location of the power distribution cable under different harmonic angular frequencies and their sensitivity to changes in insulation parameters.

[0037] Specifically, in the method for detecting the aging of distribution cable insulation based on harmonic leakage described in this invention, the broadband mode transfer function is used to characterize the propagation law of common-mode harmonic components and differential-mode harmonic components in the distribution cable along the harmonic angular frequency dimension, thereby supporting the extraction of common-mode harmonic components and differential-mode harmonic components based on the harmonic leakage current signal, and further calculating the equivalent capacitance parameters of the distribution cable insulation at different harmonic angular frequencies.

[0038] like Figure 3 As shown, the finite element simulation results of differential leakage current based on the power distribution cable structure are presented. The figure shows the load current magnetic field distribution curve formed under the action of load current, the composite magnetic field distribution curve formed by the superposition of the load current magnetic field and the leakage current magnetic field, and the leakage current magnetic field distribution curve corresponding to the harmonic leakage current caused by insulation aging.

[0039] Depend on Figure 3 It can be seen that when only normal load current exists, the magnetic field distribution exhibits obvious symmetrical characteristics, and its variation with spatial angle is smooth and the amplitude variation range is stable. When the insulation of the power distribution cable ages and generates harmonic leakage current, the leakage current magnetic field exhibits obvious asymmetrical characteristics in spatial angle distribution and forms local magnetic field disturbances in a specific angle range.

[0040] By differentially processing the magnetic field of the load current and the magnetic field of the leakage current, the influence of the normal load current magnetic field on the measurement results can be effectively suppressed, making the magnetic field variation characteristics caused by the harmonic leakage current more prominent. The differential magnetic field distribution results are consistent with the spatial angular distribution characteristics of the harmonic leakage current, verifying the feasibility of extracting the harmonic leakage current signal using the differential magnetic field method.

[0041] therefore, Figure 3 The finite element simulation results shown indicate that by acquiring the magnetic induction intensity signal generated by leakage harmonic current outside the power distribution cable and combining it with differential processing, effective sensing of harmonic leakage current can be achieved without relying on direct electrical access. This provides support for subsequent extraction of common-mode and differential-mode harmonic components based on the harmonic leakage current signal, and further evaluation of the insulation aging degree and defect location of the power distribution cable.

[0042] like Figure 4 As shown, the analytical results of magnetic induction intensity are given to illustrate the working mechanism of the dual magnetic core sensing device used in this invention in terms of magnetic field suppression and leakage harmonic sensing, as well as the correspondence between magnetic induction intensity and harmonic leakage current.

[0043] like Figure 4 As shown in the left figure, under the condition that load current and harmonic leakage current coexist, the magnetic field of the load current exhibits a distribution characteristic with a large amplitude and gradual change in spatial angular dimension, while the magnetic field amplitude caused by the harmonic leakage current is relatively small and is easily submerged by the magnetic field of the load current during direct measurement. Through the magnetic field suppression effect of the inner magnetic core in the dual-core sensing device, the main magnetic field component generated by the normal load current can be effectively weakened, making the magnetic field change caused by the harmonic leakage current stand out in the composite magnetic field.

[0044] like Figure 4 As shown in the right figure, after processing by the dual-core sensing device, the magnetic field component generated by the load current in the synthetic magnetic field is significantly suppressed, while the magnetic field component generated by the harmonic leakage current maintains a stable response characteristic in the spatial angular distribution, enabling the leakage harmonic magnetic field to be effectively sensed without relying on direct electrical connection.

[0045] Furthermore, Figure 4 The analytical results of the magnetic flux density show that, under the action of the dual-core sensing device, there is an approximately linear relationship between the magnetic flux density and the harmonic leakage current, thus providing a theoretical basis for inverting the harmonic leakage current signal based on the externally measured magnetic flux density signal. Based on this relationship, harmonic leakage current signals can be obtained at multiple node locations of the distribution cable, providing an input basis for subsequently extracting common-mode and differential-mode harmonic components at multiple harmonic angular frequencies, and further evaluating the insulation aging degree and defect location of the distribution cable.

[0046] In step S2, based on the harmonic leakage current signals at each node obtained in step S1, the harmonic leakage current is decomposed at multiple pre-selected harmonic angular frequencies to obtain the corresponding common-mode harmonic components and differential-mode harmonic components. To this end, harmonic mode characteristic analysis is first performed. The core classification of harmonic modes is based on signal propagation characteristics, mainly divided into two categories: common-mode and differential-mode. Common-mode harmonics are symmetrical harmonic components formed between the three-phase conductors of the cable and ground. Their propagation path is mainly coupled to ground, and the amplitude distribution is relatively uniform, mainly reflecting the overall state of the cable's main insulation to ground. When defects such as aging or moisture damage occur in the main insulation to ground, the equivalent capacitance parameters change, leading to a significant increase in the amplitude of the 3rd, 5th, and 11th order characteristic components of the common-mode harmonics, and the trend of change is positively correlated with the degree of aging. Differential mode harmonics are antisymmetric harmonic components formed between three-phase conductors. Their propagation depends on electromagnetic coupling between conductors, and their characteristic parameters are more sensitive to local insulation defects such as interlayer and inter-turn defects. Local defects can disrupt the electromagnetic coupling balance between conductors, leading to an increase in the phase offset of differential mode harmonics and abnormal peak values ​​of harmonic components in specific frequency bands.

[0047] The amplitude-frequency and phase-frequency characteristics show the following patterns: In the low-to-mid frequency band (10 Hz–1 kHz), the common-mode harmonic amplitude exhibits a linear distribution, primarily dominated by inductive parameters; in the wide frequency band (1 kHz–20 kHz), the inductive-capacitive parameters are highly coupled, resulting in nonlinear fluctuations in the differential-mode harmonic amplitude. Local defects can cause abrupt amplitude changes at specific frequency points, and the location of these abrupt changes is quantitatively correlated with the distance to the defect. The phase-frequency characteristics reflect changes in insulation parameters through variations in harmonic phase difference. Insulation aging leads to increased dielectric loss, which in turn causes a phase difference shift between the common-mode and differential-mode harmonics. A shift exceeding 5° typically indicates moderate to severe insulation aging. Based on these modal characteristics, the harmonic leakage current signals at each node location are analyzed under multiple pre-selected harmonic angular frequencies. Perform mode decomposition at harmonic angular frequencies At this point, calculate the node according to the following formula. Common-mode harmonic components and difference-mode harmonic components at:

[0048]

[0049]

[0050]

[0051] in, For nodes Located at harmonic angular frequency Harmonic leakage current below, and They are nodes At the harmonic angular frequency Common-mode harmonic components and difference-mode harmonic components, and They are nodes At the harmonic angular frequency The common-mode and differential-mode voltage harmonic components to ground are given, where K is the mode ratio coefficient between the common-mode and differential-mode voltages. For the insulation of the power distribution cable at the harmonic angular frequency The equivalent capacitance parameter below is used to characterize the insulation state of power distribution cables. It is the imaginary unit.

[0052] This embodiment focuses on the 3rd, 5th, and 11th harmonic components that are strongly correlated with insulation aging. It effectively eliminates external harmonic interference from nonlinear loads of the power grid and frequency converters through adaptive filtering and load harmonic separation algorithms. It also employs multimodal harmonic component analysis and multiple signal processing techniques to extract features of different components, ensuring stable output of defect identification results in complex electromagnetic environments. It can combine intelligent models such as principal component analysis and clustering algorithms to quantify the degree of aging and distinguish different aging mechanisms such as thermal aging and moisture absorption. The embodiment also provides a description of an identification accuracy rate of over 95%.

[0053] In step S3, based on the frequency domain calculation correspondence between the common-mode harmonic components and the equivalent parameters of the power distribution cable insulation, the equivalent capacitance parameters of the power distribution cable insulation at each of the harmonic angular frequencies are calculated, and the aging degree of the power distribution cable insulation is determined based on the change of the equivalent capacitance parameters at each of the harmonic angular frequencies.

[0054] To clarify the mathematical correspondence between externally measurable electrical quantities and the equivalent parameters of the internal insulation of power distribution cables, this embodiment introduces a broadband mode transfer function (MTF) as a frequency domain modeling tool to describe the propagation characteristics of harmonic signals in power distribution cables without changing the detection process. The broadband MTF is not an independent detection object, but rather used to characterize the frequency domain mapping relationship between harmonic leakage current, common-mode harmonic components, differential-mode harmonic components, and the equivalent parameters of the power distribution cable insulation, thereby providing theoretical support for calculating the equivalent capacitance parameters of the power distribution cable insulation based on the harmonic leakage current signal.

[0055] Specifically, under harmonic excitation conditions, a broadband transmission response model is constructed based on monitoring results of voltage and current harmonic components at different node locations of the distribution cable. This model describes the voltage distribution characteristics along the transmission direction of the distribution cable. A column vector of model parameters is defined. , used to characterize the voltage transfer relationship between adjacent nodes, where This represents the voltage harmonic components at the cable joint. This represents the voltage response after model mapping.

[0056] Under any harmonic angular frequency condition, the first harmonic in the finite element model of the cable... The voltage amplitude at each node is determined by the order of the circuit transmission model. Node capacitance matrix and the node inverse inductance matrix A joint decision, in which and This represents the equivalent parameter matrix, which is independent of the input nodes and only related to the cable structure and insulation condition.

[0057] To distinguish the effects of different modes on voltage distribution, the model parameter column vector is... Decoupling is achieved by dividing the common-mode parameter matrix into a difference-mode parameter matrix, which is expressed as follows:

[0058] in, and The transmission coefficients are used to characterize the proportion of contributions from common-mode and differential-mode modes. The common mode parameter matrix, This is the differential mode parameter matrix. Under the condition of neutral point voltage harmonic excitation, by analyzing the amplitude-frequency characteristics of common mode voltage and differential mode voltage at different harmonic angular frequencies, the changes in the equivalent capacitive parameters of the distribution cable insulation can be reflected, thus providing a basis for assessing the degree of insulation aging.

[0059] At any harmonic angular frequency The transmission relationship between voltage amplitudes of adjacent nodes in the finite element model of a cable can be expressed as follows:

[0060] In the low-to-mid frequency range, the equivalent impedance of each insulated branch is much larger than the inductive equivalent impedance, and the influence of inductive electrical parameters on voltage distribution is dominant. At this time, the parameter vector... Each element in the equation can be approximated as a constant coefficient, and the harmonic angular frequency is related to the constant coefficient. Regardless of changes in the insulation equivalent capacitance parameter, the cable voltage exhibits an approximately linear distribution along the transmission direction. However, at higher frequency ranges, the inductive and capacitive electrical parameters are highly coupled, causing the voltage distribution to degenerate into a non-linear pattern. In this case, the model parameter vector... The correction is based on the harmonic angular frequency, and its expression is:

[0061] in, and Representing the locations of the defect nodes respectively and insulation aging degree The relevant node equivalent capacitance matrix and node equivalent inductance matrix, This indicates the change in equivalent capacitance caused by insulation aging.

[0062] Based on the aforementioned broadband modal modeling, to establish the frequency domain correspondence between harmonic leakage current and voltage harmonics, broadband current transfer functions and broadband voltage transfer functions are further constructed. This is based on the ground harmonic leakage current. and neutral point input voltage The broadband current transfer function can be expressed as:

[0063] The broadband voltage transfer function can be expressed as:

[0064] The aforementioned broadband mode transfer function (MTF) describes the frequency domain response relationship between harmonic voltage and harmonic leakage current under different harmonic angular frequencies. Its amplitude-frequency characteristics are jointly determined by the equivalent parameters of the internal insulation of the distribution cable. By analyzing the response characteristics of the broadband MTF with changes in harmonic angular frequency, a correspondence can be established between the externally measurable harmonic leakage current signal and the equivalent capacitance parameters of the internal insulation of the distribution cable. This provides support for subsequently determining the degree of insulation aging of the distribution cable based on changes in equivalent capacitance parameters, and for locating defect nodes based on differential mode harmonic components.

[0065] Differentiated monitoring can be performed for different frequency bands: In the low and medium frequency bands, the equivalent capacitive electrical parameters of the insulation are ignored, and online monitoring of cable insulation aging is achieved through high-precision sensing of harmonic leakage current; based on the online monitoring technology of common and differential mode equivalent capacitance, referencing the linear distribution of cable voltage, the applicable frequency range is in the low and medium frequency bands; different switching modulation strategies and topologies result in different harmonic distribution patterns of the output voltage's inherent characteristics. The key to this strategy is to determine the appropriate monitoring frequency within the wide-band inherent harmonics of the distribution cable, and to obtain high-precision differential harmonic leakage current through differential measurement; the common-mode frequency and differential-mode frequency can be accurately calculated within the wide-band range, or effective common-mode and differential-mode components can be selected based on the online measured differential leakage current spectrum results to describe the equivalent capacitance distribution location. Based on the frequency domain calculation relationship between the common-mode harmonic components and the corresponding common-mode voltage-to-ground harmonic components, the insulation of the distribution cable at each harmonic angular frequency is calculated. Equivalent capacitance parameters under the following conditions The frequency domain calculation relationship is as follows:

[0066] The change in equivalent capacitance parameter ΔC is determined based on the change in equivalent capacitance parameter with harmonic angular frequency, and then the overall aging degree of the distribution cable insulation is determined based on ΔC. The common-mode harmonic component is related to the aging degree ΔC of local insulation defects but independent of location information. The differential-mode harmonic component is related to both the aging degree of defects and location information. When the cable node... When insulation aging occurs, the equivalent capacitance increment is ΔC, and the differential leakage current common-mode harmonic variation is ΔI. CM Sum and difference mode harmonic variation ΔI DM With ΔC and respectively The correlation is used to locate defects and quantify the degree of aging.

[0067] In step S4, at each harmonic angular frequency, a lateral comparative analysis is performed on the differential mode harmonic components at different node locations. The node locations where the differential mode harmonic component amplitude shows an abnormal increase are identified as the node locations corresponding to insulation aging defects in the power distribution cable. Specifically, under the same harmonic angular frequency condition, a lateral comparison is performed on the differential mode harmonic component amplitudes at different node locations along the power distribution cable. When the differential mode harmonic component amplitude at a certain node location is significantly increased relative to adjacent node locations or other node locations, or when a clearly prominent local maximum value is formed in the differential mode harmonic component amplitude distribution along each node location of the power distribution cable, the node location is determined to be an abnormal node for the differential mode harmonic components, and the abnormal node for the differential mode harmonic components is identified as the node location corresponding to insulation aging or defects in the power distribution cable.

[0068] After the aforementioned defect location is completed, this embodiment can further perform a lifetime assessment. The output voltage of the distribution cable exhibits a wide frequency distribution, with common-mode harmonic components and differential-mode harmonic components acting simultaneously on the distribution cable. The electrical stress generated by the AC electric field affects the electrical aging of the insulation material according to a probability distribution, ultimately manifesting as insulation failure (breakdown). When an insulation material operates under a certain AC electric field E (unit: kV / mm) for a long period, its electrical aging condition is typically assessed using probabilistic lifetime L. Based on surface discharge breakdown tests of the insulation material, the exponential model for electrical aging lifetime assessment is obtained as follows:

[0069] Where γ is the test coefficient and η is the voltage withstand coefficient of the test material. At the node location corresponding to the determined insulation aging defect of the distribution cable, the amplitude distribution of the common-mode harmonic voltage component and the differential-mode harmonic voltage component at multiple harmonic angular frequencies is obtained at that node location; according to the voltage withstand mode corresponding to different insulation structure types at the node location, at least one of the common-mode harmonic voltage component and the differential-mode harmonic voltage component is selected as the harmonic voltage amplitude U acting on the corresponding insulation structure; the AC stress E borne by the corresponding insulation structure at the node location is calculated based on the following formula:

[0070] Where ν is the electric field conversion coefficient corresponding to the insulation structure type, and the aging life of the insulation structure corresponding to the node location is evaluated based on the AC electric stress E. Further, in the calculation of the electrical aging life of the distribution cable insulation, the electrical aging life L is logarithmically transformed to obtain:

[0071] in , , The values ​​of γ and η are related to the characteristics of the test material itself. The higher the voltage excitation frequency, the more intense the movement of free charges inside the insulating material and the greater the dielectric loss. Therefore, γ and η have a significant frequency correlation.

[0072] like Figure 5 As shown, a cable circuit model is established based on the distributed insulation structure of the power distribution cable. Under single-frequency voltage excitation, the insulation aging process is described using an electrical aging life model of the insulation material. The life model parameters are obtained through accelerated aging tests, and the aging life is characterized by probability distribution statistics. The single-frequency electrical aging life model is used to characterize the aging trend of a single insulation component under equivalent voltage.

[0073] Based on this, considering the multi-frequency harmonic voltage excitation situation that exists in the actual operation of power distribution cables, the single-frequency lifetime model is extended to the electrical aging assessment under multi-frequency harmonic conditions. The distributed structure of the power distribution cable along the transmission direction is equivalently represented by the M-Stage circuit model, and the insulation structure at different node locations is mapped to the corresponding equivalent insulation branches, thereby distinguishing different insulation types such as ground insulation, inter-turn insulation, and inter-layer insulation.

[0074] Furthermore, under harmonic excitation conditions, the harmonic voltage acting on the insulation structure is decomposed into common-mode harmonic voltage and differential-mode harmonic voltage. Based on the voltage withstand mode of different insulation structures, the common-mode harmonic voltage, differential-mode harmonic voltage, or a combination of both is selected as the equivalent harmonic voltage amplitude for calculating AC electrical stress. Through this method, the influence mechanism of common-mode and differential-mode harmonic voltages on different insulation structures can be introduced into the electrical aging life assessment process without changing the testing procedure, enabling quantitative analysis of the aging degree of composite insulation systems.

[0075] In summary, this invention acquires magnetic induction intensity signals related to harmonic leakage current under energized operating conditions of distribution cables. Combined with common-mode and differential-mode harmonic component analysis and broadband mode transfer function modeling, it establishes a stable frequency domain correspondence between externally measurable harmonic electrical quantities and the equivalent parameters of the internal insulation of the distribution cable. This enables online quantitative assessment of the insulation aging degree of distribution cables and precise location of aging defect nodes. Furthermore, it introduces an insulation electrical aging lifetime model to evaluate the remaining lifetime of different insulation structures under multi-frequency harmonic excitation conditions. Compared to existing offline detection, partial discharge, or dielectric loss angle measurement methods, this invention offers advantages such as non-invasiveness, strong anti-interference capability, high detection sensitivity, quantifiable evaluation results, and lifetime prediction capabilities. It effectively meets the practical needs of new power systems for distribution cable condition awareness and refined operation and maintenance.

[0076] Example 2 like Figure 6 As shown, based on the same inventive concept as the above embodiments, the present invention also provides a device for detecting the aging of power distribution cable insulation based on harmonic leakage, characterized in that it includes: The magnetic field acquisition module is used to acquire the magnetic induction intensity signal generated by leakage harmonic current on the exterior of the power distribution cable at multiple node locations. The harmonic leakage current calculation module is used to determine the harmonic leakage current signal at each node location based on the magnetic induction intensity signal. The modal component extraction module is used to obtain the corresponding common-mode harmonic components and differential-mode harmonic components at multiple pre-selected harmonic angular frequencies based on the harmonic leakage current signal at each node location. The aging degree assessment module is used to calculate the equivalent capacitance parameters of the power distribution cable insulation at each harmonic angular frequency based on the frequency domain calculation correspondence between the common mode harmonic components and the equivalent parameters of the power distribution cable insulation, and to determine the aging degree of the power distribution cable insulation based on the change of the equivalent capacitance parameters at each harmonic angular frequency. The aging location module is used to perform a lateral comparative analysis of the differential mode harmonic components at different node locations under each of the harmonic angular frequencies, and to determine the node location where the amplitude of the differential mode harmonic components increases abnormally as the node location corresponding to the aging defect of the power distribution cable insulation.

[0077] Example 3 like Figure 7 As shown, the present invention also provides an electronic device 100 for implementing a method for detecting the insulation aging of power distribution cables based on harmonic leakage; The electronic device 100 includes a memory 101, at least one processor 102, a computer program 103 stored in the memory 101 and executable on at least one processor 102, and at least one communication bus 104.

[0078] The memory 101 can be used to store the computer program 103. The processor 102 implements the method for detecting the insulation aging of power distribution cables based on harmonic leakage in Embodiment 1 by running or executing the computer program stored in the memory 101 and calling the data stored in the memory 101.

[0079] The memory 101 may primarily include a program storage area and a data storage area. The program storage area may store the operating system, application programs required for at least one function (such as sound playback function, image playback function, etc.), etc.; the data storage area may store data created based on the use of the electronic device 100 (such as audio data), etc. In addition, the memory 101 may include non-volatile memory, such as hard disk, RAM, plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, at least one disk storage device, flash memory device, or other non-volatile solid-state storage device.

[0080] At least one processor 102 may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. Processor 102 may be a microprocessor or any conventional processor. Processor 102 is the control center of electronic device 100, connecting various parts of electronic device 100 via various interfaces and lines.

[0081] The memory 101 in the electronic device 100 stores multiple instructions to implement a method for detecting the insulation aging of power distribution cables based on harmonic leakage. The processor 102 can execute multiple instructions to achieve: acquiring magnetic induction intensity signals generated by leakage harmonic current outside the power distribution cable under test at multiple node locations, and determining the harmonic leakage current signal at each node location based on the magnetic induction intensity signals. Based on the harmonic leakage current signal at each node location, the corresponding common-mode harmonic components and differential-mode harmonic components are obtained at multiple pre-selected harmonic angular frequencies. Based on the frequency domain calculation correspondence between common-mode harmonic components and equivalent parameters of power distribution cable insulation, the equivalent capacitance parameters of power distribution cable insulation at each harmonic angular frequency are calculated, and the aging degree of power distribution cable insulation is determined based on the change of the equivalent capacitance parameters at each harmonic angular frequency. At each harmonic angular frequency, a lateral comparative analysis is performed on the differential mode harmonic components at different node locations. The node locations where the amplitude of the differential mode harmonic components shows an abnormal increase are identified as the node locations corresponding to the insulation aging defects of the power distribution cable.

[0082] Example 4 If the modules / units integrated in the electronic device 100 are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, and read-only memory (ROM).

[0083] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0084] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0085] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0086] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0087] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for detecting the aging of power distribution cable insulation based on harmonic leakage, characterized in that, include: At multiple node locations of the power distribution cable, the magnetic induction intensity signal generated by the leakage harmonic current outside the power distribution cable under test is acquired, and the harmonic leakage current signal at each node location is determined based on the magnetic induction intensity signal. Based on the harmonic leakage current signal at each node location, the corresponding common-mode harmonic components and differential-mode harmonic components are obtained at multiple pre-selected harmonic angular frequencies. Based on the frequency domain calculation correspondence between common-mode harmonic components and equivalent parameters of power distribution cable insulation, the equivalent capacitance parameters of power distribution cable insulation at each harmonic angular frequency are calculated, and the aging degree of power distribution cable insulation is determined based on the change of the equivalent capacitance parameters at each harmonic angular frequency. At each harmonic angular frequency, a lateral comparative analysis is performed on the differential mode harmonic components at different node locations. The node locations where the amplitude of the differential mode harmonic components shows an abnormal increase are identified as the node locations corresponding to the insulation aging defects of the power distribution cable.

2. The method for detecting aging insulation of power distribution cables based on harmonic leakage according to claim 1, characterized in that, The step of determining the harmonic leakage current signal at each node location based on the magnetic induction intensity signal includes: According to the nodes of the power distribution cable The calculation node for the magnetic field response signal generated by the harmonic leakage current, and the linear relationship expression between the magnetic field response signal and the harmonic leakage current. Harmonic leakage current at the location The linear relationship expression is as follows: in, and Based on the preset parameters determined by the experiment, For nodes Located at harmonic angular frequency The magnetic induction intensity below, For nodes Located at harmonic angular frequency Harmonic leakage current.

3. The method for detecting aging insulation of power distribution cables based on harmonic leakage according to claim 2, characterized in that, The process of obtaining the corresponding common-mode harmonic components and differential-mode harmonic components based on the harmonic leakage current signals at each node location at multiple pre-selected harmonic angular frequencies includes: At harmonic angular frequency At this point, calculate the node according to the following formula. Common-mode harmonic components and difference-mode harmonic components at: in, For nodes Located at harmonic angular frequency Harmonic leakage current below, and They are nodes At the harmonic angular frequency Common-mode harmonic components and difference-mode harmonic components, and They are nodes At the harmonic angular frequency The common-mode voltage harmonic components and differential-mode voltage harmonic components to ground under the following conditions. The modal variation coefficient between the common mode and the difference mode. For the insulation of the power distribution cable at the harmonic angular frequency The equivalent capacitance parameters are as follows. The harmonic angular frequency, It is the imaginary unit.

4. The method for detecting aging insulation of power distribution cables based on harmonic leakage according to claim 3, characterized in that, The steps for determining the degree of aging of the insulation of the power distribution cable include: Based on the frequency domain relationship between the common-mode harmonic components and the corresponding common-mode ground voltage harmonic components, the insulation of the power distribution cable at each of the aforementioned harmonic angular frequencies is calculated. Equivalent capacitance parameters under the following conditions The frequency domain calculation relationship is as follows: The change in equivalent capacitance parameters is determined based on the change in equivalent capacitance parameters with harmonic angular frequency. And based on the change in the equivalent capacitance parameter Determine the overall aging degree of the insulation of the power distribution cable.

5. The method for detecting the aging of power distribution cable insulation based on harmonic leakage according to claim 4, characterized in that, The step of determining the node location corresponding to the insulation aging defect of the power distribution cable includes: Under the same harmonic angular frequency condition, the amplitude of the differential mode harmonic component at different node locations along the power distribution cable is compared laterally. When the amplitude of the differential mode harmonic component at a certain node location increases significantly relative to the adjacent node locations or other node locations, or when a significant local maximum is formed in the amplitude distribution of the differential mode harmonic component at each node location along the power distribution cable, the node location is determined to be an abnormal node for the differential mode harmonic component. The abnormal nodes of the differential mode harmonic components are identified as the node locations corresponding to the aging or defects in the insulation of the power distribution cable.

6. The method for detecting the aging of distribution cable insulation based on harmonic leakage according to claim 5, characterized in that, Also includes: At the node location corresponding to the determined insulation aging defect of the power distribution cable, the amplitude distribution of the common-mode harmonic voltage component and the differential-mode harmonic voltage component at multiple harmonic angular frequencies is obtained. Based on the voltage withstand mode corresponding to different insulation structure types at the node location, at least one of the common-mode harmonic voltage component and the differential-mode harmonic voltage component is selected as the harmonic voltage amplitude acting on the corresponding insulation structure. ; The AC electric stress borne by the insulation structure at the node location is calculated based on the following formula. : in, The electric field conversion factor is the one corresponding to the insulation structure type. ; Based on the AC electric stress The aging life of the insulation structure at the node location is evaluated based on the following electrical aging life model for insulation materials: in, For the electrical aging life of insulating materials, and These are the lifetime model parameters determined through accelerated aging tests on insulating materials. In the calculation of the electrical aging life of the above-mentioned power distribution cable insulation, the electrical aging life is... Performing a logarithmic transformation, we obtain: ,in, , , .

7. The method for detecting aging insulation of power distribution cables based on harmonic leakage according to claim 6, characterized in that, The step of acquiring the magnetic induction intensity signal generated by leakage harmonic current at multiple node locations of the power distribution cable includes: The magnetic induction intensity signal generated by leakage harmonic current is acquired by a dual magnetic core sensing device installed on the outside of the power distribution cable. The dual magnetic core sensing device includes an inner magnetic core and an outer magnetic core arranged coaxially along the radial direction of the power distribution cable. The inner magnetic core is used to suppress the magnetic field influence generated by the normal load current of the power distribution cable, and the outer magnetic core is used to sense the magnetic induction intensity signal generated by leakage harmonic current. The magnetic induction intensity measurement bandwidth corresponding to the outer magnetic core covers 10Hz to 20kHz, and the detection sensitivity to harmonic leakage current is not less than 1mA.

8. A device for detecting the aging of power distribution cable insulation based on harmonic leakage, characterized in that, include: The magnetic field acquisition module is used to acquire the magnetic induction intensity signal generated by leakage harmonic current on the exterior of the power distribution cable at multiple node locations. The harmonic leakage current calculation module is used to determine the harmonic leakage current signal at each node location based on the magnetic induction intensity signal. The modal component extraction module is used to obtain the corresponding common-mode harmonic components and differential-mode harmonic components at multiple pre-selected harmonic angular frequencies based on the harmonic leakage current signal at each node location. The aging degree assessment module is used to calculate the equivalent capacitance parameters of the power distribution cable insulation at each harmonic angular frequency based on the frequency domain calculation correspondence between the common mode harmonic components and the equivalent parameters of the power distribution cable insulation, and to determine the aging degree of the power distribution cable insulation based on the change of the equivalent capacitance parameters at each harmonic angular frequency. The aging location module is used to perform a lateral comparative analysis of the differential mode harmonic components at different node locations under each of the harmonic angular frequencies, and to determine the node location where the amplitude of the differential mode harmonic components increases abnormally as the node location corresponding to the aging defect of the power distribution cable insulation.

9. An electronic device, characterized in that, It includes a processor and a memory, the processor being used to execute a computer program stored in the memory to implement the method for detecting the insulation aging of power distribution cables based on harmonic leakage as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores at least one instruction, which, when executed by a processor, implements the method for detecting aging insulation of power distribution cables based on harmonic leakage as described in any one of claims 1 to 7.

Images