Distribution network cable aging detection device based on broadband impedance spectroscopy

Abstract

The invention discloses a distribution network cable aging detection device based on a broadband impedance spectrum, and the device comprises a broadband signal generation module, a frequency coupling interference resistance module, a signal conditioning module, a test clamp, a data collection module, a main control module, a local aging positioning module, a temperature compensation module, a service life evaluation module, and a display storage module. The test fixture is detachably connected with the device through a shielding cable, and the device inhibits field interference through a frequency coupling interference resisting module, avoids impedance spectrum data distortion, and improves the detection accuracy. Based on the orthogonal transformation and diagnosis function algorithm of the local aging positioning module, aging sections and defects are accurately positioned, and the operation and maintenance cost is reduced. Through cooperation of a clamp embedded temperature sensor and a compensation module, temperature influence is corrected, cross-working-condition data consistency is guaranteed, a life evaluation module is combined with an EAB correlation model and time temperature equivalent conversion, a full-dimension evaluation result is output, and accurate data support is provided for operation and maintenance of a distribution network.

Description

Technical Field

[0001] This invention relates to the field of cable insulation material aging testing technology, specifically to a distribution network cable aging testing device based on broadband impedance spectrum. Background Technology

[0002] As the core carrier of power distribution in the power system, distribution cables are widely used in urban underground pipe networks, industrial parks, and residential communities. Their operational stability directly determines the reliability of power supply. Among them, cross-linked polyethylene (XLPE) cables have become the mainstream choice in the distribution network field due to their excellent insulation performance and convenient laying. However, during long-term operation, the cable insulation layer is prone to aging defects such as water treeing and electrical treeing due to environmental temperature fluctuations, soil moisture erosion, power grid harmonic interference, and mechanical stress. The conductor may also undergo oxidation and corrosion, leading to a decrease in insulation strength, increased partial discharge, and in severe cases, insulation breakdown and short circuit faults, causing large-scale power outages and significant losses to production and daily life.

[0003] To proactively identify potential aging issues in distribution network cables, the industry has developed various detection technologies, such as partial discharge detection, dielectric loss detection, and broadband impedance spectroscopy. Among these, broadband impedance spectroscopy, based on the characteristic that the equivalent impedance of a cable changes with frequency, infers the aging state by analyzing the impedance response spectrum at different frequencies. It has advantages such as being non-destructive and having a wide detection range. The relevant technology is embodied in patent CN121231958A, which achieves a preliminary judgment of the degree of cable aging through broadband impedance spectrum acquisition, reflection coefficient analysis, and calculation of the dielectric loss tangent.

[0004] However, existing distribution network cable aging detection devices based on broadband impedance spectroscopy still have many technical shortcomings in practical applications, making it difficult to meet the precision requirements of distribution network operation and maintenance: First, they have weak anti-interference capabilities. There are a large number of harmonic signals and grounding current interference in the distribution network field, and broadband excitation signals are prone to frequency coupling, resulting in distortion of impedance spectrum data and affecting the accuracy of aging judgment. Second, they lack local aging location function, and can only judge the overall degree of cable aging, but cannot locate the aging section and the location of concentrated defects, which brings inconvenience to fault diagnosis and maintenance. Third, they do not consider the influence of temperature on detection parameters. Changes in ambient temperature will cause the dielectric parameters of the cable to drift, making the detection results under different operating conditions incomparable and limiting the detection accuracy. Fourth, they can only output the degree of aging, and cannot assess the remaining service life of the cable, making it difficult to provide data support for the replacement and operation and maintenance planning of distribution network cables. Summary of the Invention

[0005] To address the technical deficiencies in the background technology, this invention proposes a distribution network cable aging detection device based on broadband impedance spectrum, which solves the aforementioned technical problems and meets practical needs. The specific technical solution is as follows: A distribution network cable aging detection device based on broadband impedance spectrum includes a broadband signal generation module, an anti-frequency coupling interference module, a signal conditioning module, a test fixture, a data acquisition module, a main control module, a local aging positioning module, a temperature compensation module, a life assessment module, and a display and storage module. The testing device has a housing, with the main control module located in the center inside the housing. The broadband signal generation module and the anti-frequency coupling interference module are stacked one on top of each other on one side of the main control module. The signal conditioning module is located below the anti-frequency coupling interference module. The data acquisition module is located on the other side of the main control module. The display and storage module is embedded in the front of the housing. The test fixture is detachably connected to the signal conditioning module via a shielded cable. The signal output port of the main control module is electrically connected to the control input terminal of the broadband signal generation module, and the signal output terminal of the broadband signal generation module is electrically connected to the input terminal of the anti-frequency coupling interference module. The output terminal of the frequency coupling interference suppression module is electrically connected to the input terminal of the signal conditioning module, and the output terminal of the signal conditioning module is electrically connected to the signal transmission terminal of the test fixture through a shielded cable. The signal feedback terminal of the test fixture is electrically connected to the input terminal of the data acquisition module, and the temperature sensor signal terminal of the test fixture is electrically connected to the input terminal of the temperature compensation module. The output terminal of the data acquisition module is electrically connected to the data input terminal of the main control module and the input terminal of the local aging positioning module, respectively. The output terminal of the local aging positioning module and the output terminal of the temperature compensation module are both electrically connected to the signal input terminal of the main control module. The evaluation signal output terminal of the main control module is electrically connected to the input terminal of the life evaluation module, and the output terminal of the life evaluation module is electrically connected to the input terminal of the display and storage module. The anti-frequency coupling interference module includes a wideband signal amplitude-frequency control loop, a series-parallel adjustable isolation transformer, and an LC filter circuit. The wideband signal amplitude-frequency control loop communicates bidirectionally with the main control module. The local aging localization module includes a phase orthogonal transformation unit and a diagnostic function calculation unit. The diagnostic function calculation unit identifies abrupt peaks in the aging segment based on the imaginary component of the impedance phase spectrum. The temperature compensation module has a pre-stored dielectric parameter temperature correction database, and the lifetime assessment module has a built-in EAB correlation model and a time-temperature equivalent conversion unit.

[0006] As an improvement to the above solution, the wideband signal generation module adopts a programmable signal generator, with an output signal frequency range of 0.1Hz to 10MHz and a signal amplitude adjustment range of 0.1V to 10V.

[0007] As an improvement to the above scheme, the wideband signal amplitude-frequency control loop of the anti-frequency coupling interference module synthesizes a wideband disturbance signal. The starting frequency of the wideband disturbance signal is 0.1Hz and the interval frequency is 50Hz. The adjustable isolation transformer has an adjustable ratio range of 1:1 to 1:10 and is compatible with 10kV and 0.4kV distribution network cables.

[0008] As an improvement to the above solution, the test fixture includes two symmetrically arranged conductive clamping heads, and the temperature sensor is embedded in the inner clamping surface of the conductive clamping head. The temperature sensor has a measurement range of -20℃ to 80℃ and a measurement accuracy of ±0.1℃.

[0009] As an improvement to the above solution, the data acquisition module includes a voltage sensor, a current sensor, and a phase acquisition unit. The accuracy class of the voltage sensor and the current sensor is not lower than 0.1, and the sampling frequency of the phase acquisition unit is not lower than 1MHz.

[0010] As an improvement to the above scheme, the diagnostic function calculation unit of the local aging location module locates the aging section in the following way: it performs an orthogonal transformation on the impedance phase spectrum, extracts the imaginary component after the transformation to construct a diagnostic function, and when a unipolar abrupt peak appears in the diagnostic function, it is determined to be the beginning or end of the aging section; when a continuous anisopolar abrupt peak appears, it is determined to be a concentrated defect, and the physical location coordinates corresponding to the abrupt peak are calculated in combination with the cable wave velocity.

[0011] As an improvement to the above scheme, the temperature compensation module's dielectric parameter temperature correction database includes correction coefficients for the real part of the relative permittivity and correction coefficients for the attenuation constant within the range of -20℃ to 80℃, and performs real-time correction on the collected dielectric parameters using a linear interpolation algorithm.

[0012] As an improvement to the above scheme, the EAB correlation model of the life assessment module is a linear regression model of "dielectric loss tangent - elongation at break", and the time-temperature equivalent conversion unit converts the actual operating time into the equivalent time of accelerated aging at 70℃.

[0013] As an improvement to the above solution, the main control module adopts a combination architecture of ARM Cortex-A9 embedded processor and FPGA chip. The FPGA chip has a built-in phase orthogonal transformation algorithm, and the embedded processor has a built-in reflection coefficient analysis and dielectric loss tangent calculation algorithm.

[0014] As an improvement to the above solution, the display storage module includes a touch screen, an SD memory card slot, and a communication module, and supports local display, storage, and cloud upload of aging level, aging location coordinates, and remaining lifespan data.

[0015] The beneficial effects of this invention are as follows: This technical solution, by setting up an anti-frequency coupling interference module, can accurately synthesize a broadband excitation signal without frequency coupling, while suppressing interference such as harmonics and grounding current in the distribution network. Combined with shielded cables and impedance matching design, it effectively avoids impedance spectrum data distortion and significantly improves the anti-interference capability and data accuracy of the detection. Relying on the phase orthogonal transformation unit and diagnostic function calculation unit of the local aging location module, the impedance phase spectrum is transformed into identifiable feature components. By identifying abrupt peaks, the beginning and end of the aging section and the location of concentrated defects are accurately located, thus achieving accurate local aging location and reducing operation and maintenance costs. By working together with the temperature sensor embedded in the test fixture and the temperature compensation module, the ambient temperature is corrected in real time based on the pre-stored dielectric parameter temperature correction database and linear interpolation algorithm, reducing the influence of temperature and calibrating the test data under different temperature conditions to the standard state. The life assessment module, through the EAB correlation model and time-temperature equivalent conversion unit, outputs the remaining life of the cable in segments based on the aging degree, forming a full-dimensional assessment result of "aging degree - aging location - remaining life", realizing full-dimensional aging assessment and providing accurate data support for distribution network operation and maintenance personnel to formulate cable replacement and maintenance plans. Attached Figure Description

[0016] Figure 1 This is a core structural framework diagram of the power distribution cable aging detection device of the present invention. Detailed Implementation

[0017] The embodiments of the present invention will be described below with reference to the accompanying drawings and related examples. The embodiments of the present invention are not limited to the following examples, and the present invention relates to the relevant necessary components in this technical field, which should be regarded as well-known technology in this technical field and can be known and mastered by those skilled in this technical field.

[0018] A distribution network cable aging detection device based on broadband impedance spectrum includes a broadband signal generation module, an anti-frequency coupling interference module, a signal conditioning module, a test fixture, a data acquisition module, a main control module, a local aging positioning module, a temperature compensation module, a life assessment module, and a display and storage module. In the technical solution of this testing device, the testing device has a housing, the main control module is located in the center inside the housing, the broadband signal generation module and the anti-frequency coupling interference module are stacked one on the side of the main control module, the signal conditioning module is located below the anti-frequency coupling interference module, the data acquisition module is located on the other side of the main control module, the display and storage module is embedded in the front of the housing, and the test fixture is detachably connected to the signal conditioning module through a shielded cable. The signal output port of the main control module is electrically connected to the control input terminal of the broadband signal generation module, and the signal output terminal of the broadband signal generation module is electrically connected to the input terminal of the anti-frequency coupling interference module. The output terminal of the frequency coupling interference suppression module is electrically connected to the input terminal of the signal conditioning module, and the output terminal of the signal conditioning module is electrically connected to the signal transmission terminal of the test fixture through a shielded cable. The signal feedback terminal of the test fixture is electrically connected to the input terminal of the data acquisition module, and the temperature sensor signal terminal of the test fixture is electrically connected to the input terminal of the temperature compensation module. The output terminal of the data acquisition module is electrically connected to the data input terminal of the main control module and the input terminal of the local aging positioning module, respectively. The output terminal of the local aging positioning module and the output terminal of the temperature compensation module are both electrically connected to the signal input terminal of the main control module. The evaluation signal output terminal of the main control module is electrically connected to the input terminal of the life evaluation module, and the output terminal of the life evaluation module is electrically connected to the input terminal of the display and storage module. The anti-frequency coupling interference module includes a wideband signal amplitude-frequency control loop, a series-parallel adjustable isolation transformer, and an LC filter circuit. The wideband signal amplitude-frequency control loop communicates bidirectionally with the main control module. The local aging localization module includes a phase orthogonal transformation unit and a diagnostic function calculation unit. The diagnostic function calculation unit identifies abrupt peaks in the aging segment based on the imaginary component of the impedance phase spectrum. The temperature compensation module has a pre-stored dielectric parameter temperature correction database, and the lifetime assessment module has a built-in EAB correlation model and a time-temperature equivalent conversion unit.

[0019] It should be noted that in the above technical solution, the main control module is located in the middle of the housing, allowing it to connect the left signal link module and the right data acquisition module with the shortest distance, thereby reducing signal transmission delay. The broadband signal generation module and the anti-frequency coupling interference module are stacked vertically on the left side of the main control module. The anti-interference module is adjacent to the signal conditioning module, ensuring that the optimized broadband signal can be directly transmitted to the signal conditioning module, reducing secondary interference. The data acquisition module is located on the right side of the main control module, which can quickly receive feedback signals from the test fixture and transmit them to the main control module and the local aging positioning module. The display and storage module is embedded in the front and right interface areas of the housing, making it convenient for on-site operators to view data and plug and unplug storage devices. The test fixture is detachably connected to the signal conditioning module through a shielded cable, adapting to the testing of distribution network cables of different lengths and specifications.

[0020] Furthermore, in the above scheme, the broadband signal generation module adopts a programmable signal generator. The frequency and amplitude of the output signal are adjusted by the main control module. A broadband power amplifier is used to amplify the signal to ensure that the signal can penetrate long-distance distribution network cables and maintain a stable amplitude. The frequency range of the output signal is 0.1Hz~10MHz, and the amplitude adjustment range is 0.1V~10V. The low frequency band (0.1Hz~1kHz) is used to detect conductor oxidation and insulation conductivity characteristics, and the mid-to-high frequency band (1kHz~10MHz) is used to detect insulation polarization loss and water tree and electrical tree defects. The amplitude can be adjusted to adapt to the signal attenuation requirements of cables of different lengths.

[0021] Specifically, the main control module controls the broadband signal generation module to generate a broadband excitation signal of 0.1Hz~10MHz with 50Hz intervals. This signal is amplified by a broadband power amplifier and then transmitted to the anti-frequency coupling interference module. The broadband signal amplitude-frequency control loop optimizes the amplitude and frequency of the signal to synthesize a broadband signal without frequency coupling. The isolation transformer blocks grounding current and harmonic interference, and the LC filter circuit filters out residual high-frequency interference to ensure the purity of the output signal.

[0022] Furthermore, in the above scheme, the wideband signal amplitude-frequency control loop of the anti-frequency coupling interference module synthesizes a wideband disturbance signal. The starting frequency of the wideband disturbance signal is 0.1Hz and the interval frequency is 50Hz. The adjustable ratio of the adjustable isolation transformer is adjustable from 1:1 to 1:10 and is compatible with 10kV and 0.4kV distribution network cables. It should be noted that the wideband signal amplitude-frequency control loop synthesizes signals at fixed frequency intervals to prevent the coupling and superposition of adjacent frequency signals; the isolation transformer adapts to cables of different voltage levels by adjusting the turns ratio to achieve signal isolation and impedance matching. The broadband signal amplitude-frequency control loop communicates bidirectionally with the main control module, receives frequency parameter commands from the main control module, and synthesizes a frequency-coupled broadband signal according to preset rules to avoid mutual interference between multiple frequency signals from the source. The series-parallel adjustable isolation transformer can switch the connection mode according to the cable voltage level to adapt to 10kV / 0.4kV distribution network cables, blocking grounding current and external harmonics from intruding into the signal link. The LC filter circuit further filters the optimized signal to remove residual high-frequency interference impurities.

[0023] Furthermore, in the above scheme, the test fixture includes two symmetrically arranged conductive clamping heads. The temperature sensor is embedded in the inner clamping surface of the conductive clamping head. The conductive clamping head ensures close contact with the cable conductor, reducing the influence of contact resistance on the detection signal. The embedded temperature sensor is close to the cable surface, collecting the cable operating temperature in real time and providing accurate data for temperature compensation. The temperature sensor has a measurement range of -20℃ to 80℃ and a measurement accuracy of ±0.1℃.

[0024] Furthermore, in the above scheme, the data acquisition module includes a voltage sensor, a current sensor, and a phase acquisition unit. The high-precision voltage and current sensors capture weak signals at both ends of the cable, the 16-bit AD conversion ensures the accuracy of signal acquisition, and the high-sampling-frequency phase acquisition unit synchronously captures impedance phase changes, providing high-quality data for subsequent analysis. The voltage sensor and current sensor have an accuracy class of no less than 0.1, and the phase acquisition unit has a sampling frequency of no less than 1MHz. It synchronously acquires impedance phase signals at different frequencies to ensure the integrity and accuracy of the phase spectrum data. The acquired data is preprocessed and then transmitted to the main control module and the local aging positioning module.

[0025] Furthermore, in the above scheme, the diagnostic function calculation unit of the local aging positioning module locates the aging segment in the following way: it performs an orthogonal transformation on the impedance phase spectrum, extracts the imaginary component after the transformation to construct a diagnostic function, and when the diagnostic function shows a unipolar abrupt peak, it is determined to be the beginning or end of the aging segment; when a continuous anisopolar abrupt peak appears, it is determined to be a concentrated defect, and the physical location coordinates corresponding to the abrupt peak are calculated in combination with the cable wave velocity.

[0026] It should be noted that the orthogonal transformation separates the real and imaginary components of the phase spectrum. The imaginary component is more sensitive to local structural abrupt changes. By inferring the aging section and defects from the type and location of the abrupt peaks, and by combining the physical coordinates with the cable wave velocity, we can accurately distinguish between uniform aging and local aging, and accurately locate the aging section and concentrated defect location without having to inspect the entire length of the cable, thus greatly shortening the fault location time.

[0027] Furthermore, in the above scheme, the dielectric parameter temperature correction database of the temperature compensation module includes the real part correction coefficient of the relative permittivity and the attenuation constant correction coefficient in the range of -20℃ to 80℃, and the collected dielectric parameters are corrected in real time by a linear interpolation algorithm.

[0028] It should be noted that, during use, the temperature compensation module pre-stores the dielectric parameter compensation coefficient of XLPE cable within the range of -20℃ to 80℃, receives the real-time temperature signal collected by the temperature sensor embedded in the test fixture, and combines it with the original dielectric parameters obtained by the data acquisition module. It then calculates the correction coefficient through a linear interpolation algorithm and outputs the real part of the corrected relative permittivity and the attenuation constant. This eliminates the influence of temperature fluctuations on the detection parameters, ensuring that the deviation of the detection data under different temperature conditions is ≤2%, guaranteeing the consistency of cross-condition detection, and broadening the applicable scenarios of the device in extreme environments such as high temperature and low temperature.

[0029] Furthermore, in the above scheme, the EAB correlation model of the life assessment module is a linear regression model of "dielectric loss tangent - elongation at break", and the time-temperature equivalent conversion unit converts the actual operating time into the equivalent time of accelerated aging at 70℃. It should be noted that the life assessment module has a built-in EAB correlation model and a time-temperature equivalent conversion unit. It receives the dielectric loss tangent value after temperature compensation, uses the EAB correlation model to back-calculate the current EAB value of the cable, and then converts the actual operating time into the equivalent time of 70℃ accelerated aging. Combined with the EAB decay rate, it outputs the remaining life value of each aging segment, realizing a full-dimensional assessment of "aging degree - aging location - remaining life". This provides maintenance personnel with accurate data support for cable replacement and maintenance plans, preventing the risk of failure caused by over-maintenance or under-maintenance.

[0030] Furthermore, in the above scheme, the main control module adopts a combination architecture of ARM Cortex-A9 embedded processor and FPGA chip. The FPGA chip has a built-in phase orthogonal transformation algorithm, and the embedded processor has a built-in reflection coefficient analysis and dielectric loss tangent calculation algorithm.

[0031] It should be noted that the ARM Cortex-A9 processor of the main control module is responsible for module control, data integration and remaining lifetime assessment calculation. It has built-in reflection coefficient analysis and dielectric loss tangent calculation algorithms. The FPGA chip has built-in phase orthogonal transformation algorithm to realize high-speed orthogonal transformation and feature extraction of impedance phase spectrum. The processing speed is ≥1GB / s, which can realize real-time detection and evaluation and meet the needs of rapid on-site detection.

[0032] Furthermore, in the above solution, the display storage module includes a touch screen, an SD storage card slot, and a communication module, and supports local display, storage, and cloud upload of aging level, aging location coordinates, and remaining lifespan data. In use, the touch screen enables human-computer interaction, the SD storage module locally saves the test data, and the communication module enables data upload to the cloud, thus balancing local operation and remote management needs.

[0033] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A distribution network cable aging detection device based on broadband impedance spectrum, characterized in that, It includes a broadband signal generation module, an anti-frequency coupling interference module, a signal conditioning module, a test fixture, a data acquisition module, a main control module, a local aging positioning module, a temperature compensation module, a life assessment module, and a display and storage module; The testing device has a housing, with the main control module located in the center inside the housing. The broadband signal generation module and the anti-frequency coupling interference module are stacked one on top of each other on one side of the main control module. The signal conditioning module is located below the anti-frequency coupling interference module. The data acquisition module is located on the other side of the main control module. The display and storage module is embedded in the front of the housing. The test fixture is detachably connected to the signal conditioning module via a shielded cable. The signal output port of the main control module is electrically connected to the control input terminal of the broadband signal generation module, and the signal output terminal of the broadband signal generation module is electrically connected to the input terminal of the anti-frequency coupling interference module. The output terminal of the frequency coupling interference suppression module is electrically connected to the input terminal of the signal conditioning module, and the output terminal of the signal conditioning module is electrically connected to the signal transmission terminal of the test fixture through a shielded cable. The signal feedback terminal of the test fixture is electrically connected to the input terminal of the data acquisition module, and the temperature sensor signal terminal of the test fixture is electrically connected to the input terminal of the temperature compensation module. The output terminal of the data acquisition module is electrically connected to the data input terminal of the main control module and the input terminal of the local aging positioning module, respectively. The output terminal of the local aging positioning module and the output terminal of the temperature compensation module are both electrically connected to the signal input terminal of the main control module. The evaluation signal output terminal of the main control module is electrically connected to the input terminal of the life evaluation module, and the output terminal of the life evaluation module is electrically connected to the input terminal of the display and storage module. The anti-frequency coupling interference module includes a wideband signal amplitude-frequency control loop, a series-parallel adjustable isolation transformer, and an LC filter circuit. The wideband signal amplitude-frequency control loop communicates bidirectionally with the main control module. The local aging localization module includes a phase orthogonal transformation unit and a diagnostic function calculation unit. The diagnostic function calculation unit identifies abrupt peaks in the aging segment based on the imaginary component of the impedance phase spectrum. The temperature compensation module has a pre-stored dielectric parameter temperature correction database, and the lifetime assessment module has a built-in EAB correlation model and a time-temperature equivalent conversion unit.

2. The distribution network cable aging detection device based on broadband impedance spectrum according to claim 1, characterized in that, The wideband signal generation module uses a programmable signal generator, with an output signal frequency range of 0.1Hz to 10MHz and a signal amplitude adjustment range of 0.1V to 10V.

3. The distribution network cable aging detection device based on broadband impedance spectrum according to claim 1, characterized in that, The wideband signal amplitude-frequency control loop of the anti-frequency coupling interference module synthesizes a wideband disturbance signal. The starting frequency of the wideband disturbance signal is 0.1Hz and the interval frequency is 50Hz. The adjustable isolation transformer has an adjustable ratio range of 1:1 to 1:10 and is compatible with 10kV and 0.4kV distribution network cables.

4. The distribution network cable aging detection device based on broadband impedance spectrum according to claim 1, characterized in that, The test fixture includes two symmetrically arranged conductive clamping heads. The temperature sensor is embedded in the inner clamping surface of the conductive clamping head. The temperature sensor has a measurement range of -20℃ to 80℃ and a measurement accuracy of ±0.1℃.

5. The distribution network cable aging detection device based on broadband impedance spectrum according to claim 1, characterized in that, The data acquisition module includes a voltage sensor, a current sensor, and a phase acquisition unit. The voltage sensor and the current sensor have an accuracy class of not less than 0.1, and the phase acquisition unit has a sampling frequency of not less than 1MHz.

6. The distribution network cable aging detection device based on broadband impedance spectrum according to claim 1, characterized in that, The diagnostic function calculation unit of the local aging location module locates the aging section in the following way: it performs an orthogonal transformation on the impedance phase spectrum, extracts the imaginary part of the transformed component to construct a diagnostic function, and when a unipolar abrupt peak appears in the diagnostic function, it is determined to be the beginning or end of the aging section; when a continuous anisopolar abrupt peak appears, it is determined to be a concentrated defect, and the physical location coordinates corresponding to the abrupt peak are calculated in combination with the cable wave velocity.

7. The distribution network cable aging detection device based on broadband impedance spectrum according to claim 1, characterized in that, The temperature compensation module's dielectric parameter temperature correction database includes correction coefficients for the real part of the relative permittivity and correction coefficients for the attenuation constant within the range of -20℃ to 80℃. The collected dielectric parameters are corrected in real time using a linear interpolation algorithm.

8. The distribution network cable aging detection device based on broadband impedance spectrum according to claim 1, characterized in that, The EAB correlation model of the life assessment module is a linear regression model of "dielectric loss tangent - elongation at break", and the time-temperature equivalent conversion unit converts the actual operating time into the equivalent time of accelerated aging at 70℃.

9. The distribution network cable aging detection device based on broadband impedance spectrum according to claim 1, characterized in that, The main control module adopts a combination architecture of ARM Cortex-A9 embedded processor and FPGA chip. The FPGA chip has a built-in phase orthogonal transformation algorithm, and the embedded processor has a built-in reflection coefficient analysis and dielectric loss tangent calculation algorithm.

10. The distribution network cable aging detection device based on broadband impedance spectrum according to claim 1, characterized in that, The display and storage module includes a touch screen, an SD memory card slot, and a communication module, and supports local display, storage, and cloud upload of aging level, aging location coordinates, and remaining lifespan data.

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