Method and device for evaluating the insulation performance of ac polypropylene cables under impulse voltage

Abstract

The application discloses a kind of AC polypropylene cable insulation performance evaluation method and device under impulse voltage, to solve the technical problem that there is no AC polypropylene cable insulation performance evaluation under impulse voltage at present.The method comprises: obtaining the cable slice of AC polypropylene cable;Based on the rise and fall method test, obtain the polypropylene probabilistic breakdown field strength of cable slice;According to the polypropylene probabilistic breakdown field strength, combined with cumulative breakdown test under multiple impulse voltages, construct the life model for the life prediction of AC polypropylene cable;Combined with cumulative loss test under multiple impulse voltages, the dielectric property of cable slice is tested, and the aging model for the insulation performance parameter evaluation of AC polypropylene cable is constructed.

Description

Technical Field

[0001] This invention relates to the field of cable material performance evaluation technology, and in particular to a method for evaluating the insulation performance of AC polypropylene cables under impulse voltage, a device for evaluating the insulation performance of AC polypropylene cables under impulse voltage, an electronic device, and a storage medium. Background Technology

[0002] As the primary medium for electrical energy transmission in power systems, power cables play a crucial role. Nowadays, with the continuous increase in transmission voltage levels, the requirements for power cable insulation materials are also becoming increasingly stringent.

[0003] During long-term operation, due to conductor heating and ambient heat, power cable insulation materials generally operate at a certain temperature level. Currently, widely used cross-linked polyethylene (XLPE) power cables typically have a maximum operating temperature of 90℃, lower than that of polypropylene (PP) power cables (110℃). Therefore, polypropylene cables have the advantage of a higher operating temperature compared to XLPE cables, which is beneficial for increasing their current carrying capacity. Furthermore, the production process of XLPE cables easily forms cross-linking byproducts, affecting insulation performance. Additionally, XLPE cable materials are difficult to recycle after service, failing to meet the requirements of today's environmentally friendly power cables. In conclusion, polypropylene has become one of the new environmentally friendly power cable insulation materials to replace XLPE. Therefore, research on the dielectric properties and aging characteristics of polypropylene insulation materials has gradually attracted researchers' attention.

[0004] Under the long-term operation of power frequency electrical stress, insulation materials inevitably deteriorate to some extent. This phenomenon is considered the electrical aging process of cables under long-term operation. Currently, the inverse power model is mainly used to describe the lifespan of insulation materials under long-term electrical stress. This model allows for the quantitative calculation of the insulation material's lifespan at a given electric field strength. However, in reality, in addition to the conventional long-term power frequency electrical stress, power cables also experience impulse voltages under certain conditions due to lightning, resonance, and switching overvoltages. For AC polypropylene high-voltage cables operating in actual power systems, it is necessary to evaluate their performance under multiple external impulse voltages. Currently, there is no complete method for evaluating the insulation performance of AC polypropylene cables under impulse voltages. Summary of the Invention

[0005] This invention provides a method for evaluating the insulation performance of AC polypropylene cables under impulse voltage, a device for evaluating the insulation performance of AC polypropylene cables under impulse voltage, an electronic device, and a storage medium, which are used to solve or partially solve the technical problem that there is currently no method for evaluating the insulation performance of AC polypropylene cables under impulse voltage.

[0006] This invention provides a method for evaluating the insulation performance of AC polypropylene cables under impulse voltage, the method comprising:

[0007] Obtain cable slices of AC polypropylene cable;

[0008] The probabilistic breakdown field strength of the polypropylene in the cable slice was obtained based on the rise-fall method test.

[0009] Based on the probabilistic breakdown field strength of polypropylene, a lifetime model is constructed by combining cumulative breakdown tests under multiple impulse voltages; the lifetime model is used to predict the lifetime of the AC polypropylene cable.

[0010] The dielectric properties of the cable slices were tested by combining cumulative loss tests under multiple impulse voltages to construct an aging model; the aging model was used to evaluate the insulation performance parameters of the AC polypropylene cable.

[0011] Optionally, obtaining the probabilistic breakdown field strength of the polypropylene in the cable slice based on the rise-fall method test includes:

[0012] Obtain voltage level data;

[0013] A breakdown test based on voltage rise and fall adjustment is performed on the cable slice according to the voltage level data to obtain the breakdown probability and the breakdown voltage at the breakdown probability.

[0014] The breakdown field strength at the breakdown probability is calculated based on the breakdown voltage, and is used as the probabilistic breakdown field strength of the polypropylene in the cable slice.

[0015] Optionally, the voltage level data includes several voltage levels with increasing voltage differentials; the step of performing a breakdown test on the cable slice based on voltage rise and fall adjustment according to the voltage level data to obtain the breakdown probability and the breakdown voltage at the breakdown probability includes:

[0016] Step S1: Select a target voltage level in ascending order of voltage level;

[0017] Step S2: Apply the multiple breakdown test voltage corresponding to the target voltage level to the cable slices one by one;

[0018] Step S3: Determine whether a breakdown occurs during the voltage application process; if not, select the next voltage level after the current target voltage level as the new target voltage level and proceed to step S2; if yes, select the previous voltage level after the current target voltage level as the new target voltage level and proceed to step S2.

[0019] Step S4: When all voltage levels of breakdown tests are completed, calculate the breakdown probability and the breakdown voltage at the breakdown probability based on the breakdown test results.

[0020] Optionally, the step of constructing a lifetime model based on the probabilistic breakdown field strength of the polypropylene and combined with cumulative breakdown tests under multiple impact voltages includes:

[0021] Based on the probabilistic breakdown field strength of the polypropylene, the cable slice was subjected to a cumulative breakdown test under multiple impulse voltages to obtain the UN characteristic curve between the impulse voltage amplitude U and the number of impulse voltages N.

[0022] Based on the UN characteristic curve, a linear fitting was performed to obtain the life model of the AC polypropylene cable under different impulse voltages.

[0023] Optionally, the step of conducting cumulative breakdown tests on the cable slice under multiple impulse voltages based on the probabilistic breakdown field strength of the polypropylene, and obtaining the UN characteristic curve between the impulse voltage amplitude U and the number of impulse voltages N, includes:

[0024] Based on the probabilistic breakdown field strength of the polypropylene, and according to the breakdown voltage, multiple impact voltage amplitudes U are determined to perform a stepped voltage reduction with a preset voltage drop amplitude.

[0025] For each of the aforementioned impulse voltage amplitudes U, the impulse voltage amplitude U is repeatedly applied to the cable slice until the cable slice breaks down, and the number of impulse voltage counts N is recorded.

[0026] Based on each of the stated impulse voltage amplitudes U and their corresponding impulse voltage number N, plot the UN characteristic curve between the impulse voltage amplitude U and the impulse voltage number N.

[0027] Optionally, the dielectric performance testing of the cable slices combined with the cumulative loss test under multiple impulse voltages to construct an aging model includes:

[0028] The cable slices were subjected to cumulative breakdown tests under multiple impulse voltages to obtain the dielectric properties of the AC polypropylene cable after being subjected to different numbers of impulse voltages; the dielectric properties were used to evaluate the cumulative loss effect of multiple impulse voltages on the AC polypropylene cable.

[0029] Based on the dielectric performance parameters, an aging model of the AC polypropylene cable under different impulse voltages was constructed.

[0030] Optionally, the dielectric performance parameters include the breakdown field strength, steady-state conduction current, isothermal relaxation depolarization current, and maximum space charge density after the impulse voltage; the step of constructing an aging model of the AC polypropylene cable under different impulse voltages based on the dielectric performance parameters includes:

[0031] Based on the impulse voltage amplitude, the number of impulse voltages, and the breakdown field strength, a power frequency breakdown field strength model is constructed; the power frequency breakdown field strength model is used to evaluate the remaining breakdown field strength of the AC polypropylene cable after the impulse voltage.

[0032] A conductivity current model is constructed based on the impulse voltage amplitude, the number of impulse voltages, and the steady-state conductivity current; the conductivity current model is used to evaluate the conductivity characteristics of the AC polypropylene cable after the impulse voltage.

[0033] Based on the fitting results of the isothermal relaxation depolarization current, the life index of the insulation material after the impact voltage is calculated, and an aging degree assessment model is constructed according to the impact voltage amplitude, the number of impact voltages, and the life index of the insulation material; the aging degree assessment model is used to assess the aging degree of the AC polypropylene cable after the impact voltage.

[0034] A space charge model is constructed based on the impulse voltage amplitude, the number of impulse voltages, and the maximum space charge density; the space charge model is used to evaluate the space charge characteristics of the AC polypropylene cable after the impulse voltage.

[0035] The power frequency breakdown field strength model, the electrical conductivity current model, the aging degree assessment model, and the space charge model are integrated to form the aging model of the AC polypropylene cable under different impulse voltages.

[0036] The present invention also provides a device for evaluating the insulation performance of AC polypropylene cables under impulse voltage, comprising:

[0037] Cable slice acquisition unit, used to acquire cable slices of AC polypropylene cable;

[0038] The rise-fall test unit is used to obtain the probabilistic breakdown field strength of the polypropylene in the cable slice based on the rise-fall test.

[0039] The lifetime model construction unit is used to construct a lifetime model based on the probabilistic breakdown field strength of the polypropylene and the cumulative breakdown test under multiple impulse voltages; the lifetime model is used to predict the lifetime of the AC polypropylene cable.

[0040] The aging model construction unit is used to conduct dielectric performance tests on the cable slices by combining cumulative loss tests under multiple impulse voltages, and to construct an aging model; the aging model is used to evaluate the insulation performance parameters of the AC polypropylene cable.

[0041] The present invention also provides an electronic device, the device comprising a processor and a memory:

[0042] The memory is used to store program code and transmit the program code to the processor;

[0043] The processor is configured to execute, according to instructions in the program code, the insulation performance evaluation method for AC polypropylene cables under impulse voltage as described in any of the preceding claims.

[0044] The present invention also provides a computer-readable storage medium for storing program code for executing the insulation performance evaluation method for AC polypropylene cables under impulse voltage as described in any of the preceding claims.

[0045] As can be seen from the above technical solutions, the present invention has the following advantages:

[0046] A method for evaluating the insulation performance of AC polypropylene cables under impulse voltage is provided. First, cable sections of the AC polypropylene cable are obtained, directly using actual cable sections as the research object, which makes the evaluation results more reliable. Next, the probabilistic breakdown field strength of the polypropylene in the cable sections is obtained based on the rise-fall method test. Then, based on the probabilistic breakdown field strength of polypropylene, combined with cumulative breakdown tests under multiple impulse voltages, a lifetime model for predicting the lifetime of the AC polypropylene cable is constructed. Simultaneously, the dielectric properties of the cable sections are tested by cumulative loss tests under multiple impulse voltages, constructing an aging model for evaluating the insulation performance parameters of the AC polypropylene cable. Thus, the probabilistic breakdown field strength is obtained through the rise-fall method test, and the lifetime model of the AC polypropylene insulation material is obtained through cumulative breakdown tests under multiple impulse voltages. Simultaneously, the cumulative loss characteristic model is constructed using the dielectric property parameters measured after multiple impulse voltages as an aging model of the polypropylene insulation material under the cumulative action of impulse voltages, characterizing the impact of multiple impulse voltages on the insulation material performance. By focusing on the actual operating status and insulation performance degradation of power cables after being subjected to impulse voltage, this paper provides a complete description of the breakdown characteristics, cumulative loss characteristics, and life model of polypropylene under impulse voltage, which is of guiding significance for the condition assessment of power cables after being subjected to corresponding impulses in actual operation. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 A schematic diagram of a cross-section of an AC polypropylene cable;

[0049] Figure 2 A flowchart illustrating the steps of a method for evaluating the insulation performance of AC polypropylene cables under impulse voltage.

[0050] Figure 3 This is a schematic diagram of a typical impulse voltage waveform;

[0051] Figure 4 This is a schematic diagram of a commonly used circuit for impulse voltage.

[0052] Figure 5 This is a schematic diagram of a multi-stage impulse voltage generator;

[0053] Figure 6 A schematic diagram of a step-up method for measuring the breakdown field strength of probabilistic impulse voltage;

[0054] Figure 7 This is a schematic diagram of the UN characteristic curve of a polypropylene insulating material.

[0055] Figure 8 This is a schematic diagram of the overall process for evaluating the insulation performance of AC polypropylene cables under impulse voltage.

[0056] Figure 9 This is a structural block diagram of a device for evaluating the insulation performance of AC polypropylene cables under impulse voltage. Detailed Implementation

[0057] This invention provides a method for evaluating the insulation performance of AC polypropylene cables under impulse voltage, a device for evaluating the insulation performance of AC polypropylene cables under impulse voltage, an electronic device, and a storage medium, which are used to solve or partially solve the technical problem that there is currently no method for evaluating the insulation performance of AC polypropylene cables under impulse voltage.

[0058] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0059] As an example, taking AC polypropylene cable insulation material as an example, under the long-term operation of power frequency electrical stress, the insulation material will inevitably deteriorate to a certain extent. This phenomenon is regarded as the electrical aging process of the cable under long-term operation. Currently, the lifetime model of insulation material under long-term electrical stress is mainly described by an inverse power model. Through this model, the lifetime of insulation material under a certain electric field strength can be quantitatively calculated.

[0060] However, in reality, in addition to the conventional long-term power frequency electrical stress, power cables also experience impulse voltages under certain circumstances due to lightning, resonance, and switching overvoltages. For AC polypropylene high-voltage cables operating in actual power systems, it is necessary to evaluate their performance under multiple external impulse voltages. Currently, there is no complete method for evaluating the insulation performance of AC polypropylene cables under impulse voltages.

[0061] Through further analysis, this invention suggests that the insulation performance evaluation and life model of AC polypropylene insulation materials under impulse voltage can mainly include the following aspects.

[0062] (a) Probabilistic breakdown field strength of AC polypropylene insulation material under impulse voltage

[0063] Due to the special nature of impulse voltage, the breakdown characteristics of insulating materials are generally described by probabilistic breakdown field strength. Currently, the most widely used is the 50% impulse breakdown field strength. That is, under this impulse voltage amplitude, the insulating material has a 50% probability of breakdown. However, different locations and uses of insulating materials require corresponding breakdown field strengths. For example, for critical insulation materials, where a larger margin is required in the design, a 10% breakdown field strength or a lower probability breakdown field strength is more appropriate. For non-critical insulation materials, a 90% breakdown field strength may also meet system requirements.

[0064] (II) Breakdown characteristics of polypropylene insulation material under multiple impulse voltages

[0065] In actual operation, the probability of insulation breakdown due to a single impulse voltage is relatively small. Breakdown of the insulation material by applying impulse voltage mainly stems from the cumulative effect of multiple impulse voltages. Therefore, it is also necessary to consider the breakdown characteristics of AC polypropylene insulation material under the cumulative effect of multiple impulse voltages. The primary objective of this process is to obtain the UN characteristic curve between the impulse voltage amplitude U and the number of breakdowns N. This curve can be used to further derive the life model of AC polypropylene under impulse voltage.

[0066] (III) Cumulative loss characteristics of polypropylene insulation material under multiple impulse voltages

[0067] Even if long-term impulse voltages do not directly break down the insulation material, the cumulative losses they cause will gradually render it unsuitable for long-term operation in power systems. The effects of long-term impulse voltages on insulation materials include, but are not limited to, degradation of their inherent properties and a decrease in their ability to withstand long-term electrical stress. Therefore, it is necessary to evaluate the cumulative loss characteristics of AC polypropylene insulation materials under multiple impulse voltages.

[0068] Therefore, one of the core inventive points of this invention is to propose a method for evaluating the insulation performance of AC polypropylene cables under impulse voltage, taking into full account the operating characteristics of AC polypropylene materials under impulse voltage. Using actual cable slices of AC polypropylene cables as the research object, the probabilistic breakdown field strength is obtained through a rise-fall method test. A lifetime model of the AC polypropylene insulation material is obtained through cumulative breakdown tests with multiple impulse voltages. Simultaneously, a cumulative loss characteristic model is constructed using the dielectric performance parameters measured after multiple impulse voltages, serving as an aging model for the polypropylene insulation material under the cumulative effect of impulse voltages, to characterize the impact of multiple impulse voltages on the insulation material's performance. This invention primarily focuses on the actual operating state and insulation performance degradation of power cables after impulse voltage. The proposed scheme can fully describe the breakdown characteristics, cumulative loss characteristics, and lifetime model of polypropylene under impulse voltage, thus providing guidance for the condition assessment of power cables after being subjected to corresponding impulses in actual operation.

[0069] This invention provides a ring-shaped cable slicing device. This device can cut cable slices of different thicknesses along the ring direction of the cable. Compared to the commonly used parallel slicing method, the schematic diagram of the AC polypropylene cable slice provided in this invention is shown below. Figure 1 As shown, the specific circular slicing method can be seen in r4.

[0070] After cutting cable slices at the desired research locations, probabilistic breakdown field strength tests can be conducted. Based on the obtained impulse voltage breakdown field strength, the UN characteristic curve between the impulse voltage amplitude U and the number of impulse voltages N required for the cable slice sample to break down is obtained by reducing the voltage amplitude. A lifetime model is then obtained through curve fitting. The insulation performance of AC polypropylene cables under multiple impulse voltages is evaluated using various dielectric performance assessment methods, such as power frequency breakdown tests, conductivity current tests, space charge tests, and isothermal relaxation current tests.

[0071] Reference Figure 2 The diagram illustrates a flowchart of a method for evaluating the insulation performance of an AC polypropylene cable under impulse voltage, as provided in an embodiment of the present invention. Specifically, it may include the following steps:

[0072] Step 201: Obtain a cable slice of the AC polypropylene cable;

[0073] Firstly, a ring-shaped cable slicing device can be used to obtain cable slices of AC polypropylene cable at different locations. The specific slice locations can be set according to actual research needs.

[0074] Step 202: Obtain the probabilistic breakdown field strength of the polypropylene in the cable slice based on the rise and fall method test;

[0075] In this step, the probabilistic breakdown field strength of polypropylene (including the 50% impact breakdown field strength, which has the widest applicability) is obtained through the rise-fall method test. By obtaining the breakdown field strength of AC polypropylene cables under multiple probabilities, the impact breakdown characteristics of the insulation material can be fully evaluated.

[0076] For example, Figure 3 A schematic diagram of a typical impulse voltage waveform is shown.

[0077] Figure 3 middle, The wavefront time is defined as the time it takes to pass through the wavefront. and The x-coordinate distance between the straight line and the intersection points of the zero point and the peak point. The tail time is defined as the abscissa distance between zero and half-peak. The impulse voltage waveform can be described using a double exponential waveform, as shown in the following equation:

[0078]

[0079] in, This represents the voltage value at time t; Indicates peak voltage; , All represent exponential fitting coefficients.

[0080] Figure 4 A schematic diagram of a common impulse voltage circuit is shown. The relationship between resistance / capacitance and wavefront / tail time can be calculated as follows:

[0081]

[0082]

[0083] In practical applications, the waveform of the impulse voltage can be altered by changing the resistance and capacitance. Those skilled in the art can modify the corresponding parameters according to their own experimental needs. It is understood that this invention does not impose any limitations on this.

[0084] When a higher surge voltage is required, it can be achieved through... Figure 5 The multi-stage impulse voltage generator shown is an example of this. The multi-stage impulse voltage generator primarily utilizes the principle of "series charging and parallel discharging" to generate high-amplitude impulse voltages.

[0085] During charging, the spark gap is not broken down, therefore this branch is considered open in the charging circuit. At this time, the capacitors C at each stage are connected in parallel through a number of charging resistors R with a voltage of... The power supply charges the generator. During the discharge process, once the first gap F1 breaks down, gaps F2, F3, and so on are broken down in sequence. The series connection of the capacitors causes the generator to change from a charging state to a discharging state. During the discharge process, because the resistance R of each charging resistor is relatively large, the resistor branch can be simplified to an open circuit during the short discharge process.

[0086] Based on the above analysis, during the discharge process, the voltage on all parallel capacitors is released in series, which can form a high-amplitude instantaneous high voltage.

[0087] In some embodiments, the process of obtaining the probabilistic breakdown field strength of polypropylene in cable slices based on the rise-fall method test can be achieved by performing the following sub-steps from 2021 to 2023:

[0088] Step 2021: Obtain voltage level data;

[0089] Step 2022: Perform a breakdown test on the cable slices based on voltage level data and voltage ramp-up / downgrade adjustment to obtain the breakdown probability and the breakdown voltage at the breakdown probability.

[0090] Furthermore, the voltage level data includes several voltage levels with increasing voltage differentials. The process of performing breakdown tests on cable segments based on voltage rise / fall adjustments according to the voltage level data to obtain the breakdown probability and the breakdown voltage at that probability can be achieved by executing the following sub-steps S1 to S4:

[0091] Step S1: Select a target voltage level in ascending order of voltage level;

[0092] Step S2: Apply the multiple breakdown test voltage corresponding to the target voltage level to the cable slices one by one;

[0093] Step S3: Determine whether a breakdown occurs during the voltage application process; if not, select the next voltage level after the current target voltage level as the new target voltage level and proceed to step S2; if yes, select the previous voltage level after the current target voltage level as the new target voltage level and proceed to step S2.

[0094] Step S4: When all voltage levels of breakdown tests are completed, calculate the breakdown probability and the breakdown voltage at the breakdown probability based on the breakdown test results.

[0095] Step 2023: Calculate the breakdown field strength under the breakdown probability based on the breakdown voltage, and use it as the probabilistic breakdown field strength of polypropylene in the cable slice.

[0096] In practical applications, for the voltage ramp-up test described in the preceding steps, assume there are m groups of applied voltage levels, each group containing n constant voltage changes. During the ramp-up test, if the current voltage level... If no breakdown occurs in any of the corresponding n voltage increases, then at the current voltage level... Add a voltage difference to the basis ,Will As the next voltage level, continue with the breakdown test. If the current voltage level If breakdown occurs during a set of n voltage increases, then reduce the corresponding voltage, i.e., reduce the voltage difference by one. To obtain the previous voltage level Continue performing breakdown tests. Through several sets of breakdown tests, the probabilistic breakdown voltage can be obtained. As shown in the following formula:

[0097]

[0098] In the formula, For voltage The number of groups to which voltage is applied, where m is the total number of groups.

[0099] Probabilistic breakdown voltage Breakdown probability The result can be calculated using the following formula:

[0100]

[0101] It can be clearly seen from the above formula that when the number of pressurization cycles n=1, the result is the 50% impulse breakdown voltage of the insulating material.

[0102] It is understood that those skilled in the art can adjust the test parameters of the rise and fall method according to different needs to obtain the breakdown field strength at different probabilities (such as 50%, 10%, 90%, etc.). For example, Figure 6 A schematic diagram of a step-up / step-down method for measuring the probabilistic impulse voltage breakdown field strength is shown. The process calculates the 50% impulse breakdown voltage.

[0103] Step 203: Based on the probabilistic breakdown field strength of the polypropylene, a lifetime model is constructed by combining the cumulative breakdown test under multiple impulse voltages; the lifetime model is used to predict the lifetime of the AC polypropylene cable.

[0104] In the specific implementation, based on the probabilistic breakdown field strength of polypropylene, and combined with the cumulative breakdown test under multiple impulse voltages, a life model is constructed. This model can be: using the probabilistic breakdown field strength of polypropylene as a benchmark, the cable slices are subjected to cumulative breakdown tests under multiple impulse voltages to obtain the UN characteristic curve between the impulse voltage amplitude U and the number of impulse voltages N; based on the UN characteristic curve, linear fitting is performed to obtain the life model of AC polypropylene cable under different impulse voltages.

[0105] In some embodiments, the process of obtaining the UN characteristic curve between the impulse voltage amplitude U and the number of impulse voltages N by performing cumulative breakdown tests on cable slices under multiple impulse voltages based on the probabilistic breakdown field strength of polypropylene can be achieved by performing the following sub-steps 2031 to 2033:

[0106] Step 2031: Based on the probabilistic breakdown field strength of polypropylene, determine multiple impulse voltage amplitudes U for step-down voltage reduction according to the breakdown voltage.

[0107] Step 2032: For each impulse voltage amplitude U, repeatedly apply the impulse voltage amplitude U to the cable slice until the cable slice breaks down, and record the number of impulse voltages N;

[0108] Step 2033: Based on each impulse voltage amplitude U and its corresponding impulse voltage number N, plot the UN characteristic curve between the impulse voltage amplitude U and the impulse voltage number N.

[0109] Specifically, to obtain a lifetime model for polypropylene insulation material under impulse voltage, the probabilistic breakdown field strength of polypropylene obtained from the aforementioned steps is used as a benchmark. This is achieved by continuously reducing the impulse voltage amplitude, for example, by setting the voltage difference of the impulse voltage amplitude as... By accumulating multiple impulse voltages, the UN characteristic curve between the impulse voltage amplitude U and the number of impulse voltages N required for the cable slice sample to break down can be obtained. Then, curve fitting is performed to obtain the life model of the polypropylene insulation material under impulse voltage. The UN characteristic curve of the polypropylene insulation material is shown below. Figure 7 As shown.

[0110] The UN characteristic curve can be fitted using an exponential model to obtain the life model of AC polypropylene cable under different impulse voltages, as shown in the following formula:

[0111]

[0112] 1 represents the slope of the curve. This represents the fit index.

[0113] Using the above life model, the service life of polypropylene insulation material under different impulse voltage amplitudes can be calculated.

[0114] Step 204: The dielectric properties of the cable slices are tested by combining the cumulative loss test under multiple impulse voltages to construct an aging model; the aging model is used to evaluate the insulation performance parameters of the AC polypropylene cable.

[0115] This step mainly involves using a dielectric performance testing system to measure the dielectric properties of polypropylene insulation material after being subjected to different numbers of impact voltages. Based on the measured parameters, the cumulative effect of multiple impact voltages on cable slice samples is evaluated, and an aging model of AC polypropylene cables under impact voltage is constructed.

[0116] In the specific implementation, the dielectric properties of the cable slices are tested by combining the cumulative loss test under multiple impulse voltages, and an aging model is constructed. This can be done as follows: First, the cable slices are subjected to cumulative breakdown tests under multiple impulse voltages to obtain the dielectric properties of the AC polypropylene cable after being subjected to different impulse voltages. The dielectric properties are used to evaluate the cumulative loss effect of multiple impulse voltages on the AC polypropylene cable. Then, based on the dielectric properties, an aging model of the AC polypropylene cable under different impulse voltages is constructed.

[0117] In some embodiments, the dielectric performance parameters include the breakdown field strength, steady-state conduction current, isothermal relaxation depolarization current, and maximum space charge density after the application of an impulse voltage. Therefore, the process of constructing an aging model of an AC polypropylene cable under different impulse voltages based on the dielectric performance parameters can be achieved by performing the following sub-steps 2041 to 2045:

[0118] Step 2041: Construct a power frequency breakdown field strength model based on the impulse voltage amplitude, the number of impulse voltages, and the breakdown field strength; the power frequency breakdown field strength model is used to evaluate the residual breakdown field strength of the AC polypropylene cable after the impulse voltage.

[0119] For breakdown field strength tests, a functional relationship can be constructed between the number of impulse voltages N, the impulse voltage amplitude U, and the breakdown field strength E after the impulse voltage is applied, which can be used as a power frequency breakdown field strength model:

[0120]

[0121] The power frequency breakdown field strength of polypropylene insulation material after an impulse voltage can be quantitatively calculated using a power frequency breakdown field strength model. If the calculated breakdown field strength value is less than the system requirements, replacement should be considered.

[0122] Step 2042: Construct a conduction current model based on the impulse voltage amplitude, the number of impulse voltages, and the steady-state conduction current; the conduction current model is used to evaluate the conductivity characteristics of the AC polypropylene cable after the impulse voltage.

[0123] For conduction current tests, the number of impulse voltages N, the impulse voltage amplitude U, and the steady-state conduction current after the impulse voltage is applied can be constructed. The functional relationship between them serves as a model for electrical conduction and current:

[0124]

[0125] Step 2043: Calculate the insulation material lifetime index after the impact voltage based on the fitting results of the isothermal relaxation depolarization current, and construct an aging degree assessment model based on the impact voltage amplitude, the number of impact voltages and the insulation material lifetime index; the aging degree assessment model is used to assess the aging degree of AC polypropylene cables after the impact voltage.

[0126] For isothermal relaxation current tests, the isothermal relaxation depolarization current can first be fitted using the following triple-exponential model:

[0127]

[0128] Among them, the morphology of the cable slice sample is a coexistence of spherulites and amorphous forms. Its relaxation mechanism can be divided into three types: (1) macroscopic relaxation formed by the sample and the electrode. Although AC polypropylene is a weakly polar medium, there is a shift in the charge center on the side chains and end groups of its molecules, and it still exhibits certain dipole characteristics. Therefore, AC polypropylene has dipole polarization. Reflected in macroscopic polarization, it is the polarization mechanism formed by the electrode and the medium. (2) Considering that the morphology of the cable slice sample is a spherulite and amorphous form, there is an interface between the spherulites and amorphous forms. Therefore, there is spherulite and amorphous interface polarization, which is represented as a mesoscopic polarization. (3) There may be some small molecule impurities in the polypropylene insulation material, and these impurities also interact with the molecules. In the above formula, and This relates to the three relaxation mechanisms in polypropylene described above. That is, the relaxation time constant of the relevant relaxation mechanism. This represents the corresponding relaxation strength.

[0129] The life index of insulation materials can be calculated from the fitting results. :

[0130]

[0131]

[0132]

[0133] Next, the number of impulse voltages N, the impulse voltage amplitude U, and the lifetime index of the insulation material after the impulse voltage can be constructed. The functional relationship between them serves as a model for assessing the degree of aging:

[0134]

[0135] When calculated A value greater than 2.1 indicates severe aging of the polypropylene insulation material. By using an aging assessment model and considering the actual operating conditions of the cable, the operational status of the AC polypropylene cable at this point can be qualitatively analyzed. If severe aging is achieved, enhanced testing and evaluation of that section of the cable should be considered, or even partial replacement of the cable may be necessary.

[0136] Step 2044: Construct a space charge model based on the impulse voltage amplitude, the number of impulse voltages, and the maximum space charge density; the space charge model is used to evaluate the space charge characteristics of the AC polypropylene cable after impulse voltage.

[0137] For space charge experiments, the number of impulse voltages N, the impulse voltage amplitude U, and the maximum space charge density after the impulse voltage can be constructed. The functional relationship between them serves as a model for space charge:

[0138]

[0139] An increase in space charge density may lead to an increase in the electric field strength inside the dielectric, thereby accelerating the aging process of the AC polypropylene cable insulation material. If the calculated space charge density is large, the actual situation of this part of the cable in subsequent operation should be given special consideration.

[0140] Step 2045: Integrate the power frequency breakdown field strength model, the electrical conductivity current model, the aging degree assessment model, and the space charge model to form an aging model for AC polypropylene cables under different impulse voltages.

[0141] By integrating the power frequency breakdown field strength model, electrical conductivity current model, aging degree assessment model, and space charge model constructed in the aforementioned steps, an aging model of AC polypropylene cable under different impulse voltages can be obtained.

[0142] Based on all the above steps, a comprehensive analysis can be conducted to determine the trend of insulation performance changes of AC polypropylene insulation material under multiple impulse voltages, which has certain guiding significance for actual power cables in operation.

[0143] In this invention embodiment, considering the operating characteristics of AC polypropylene materials under impulse voltage, a method for evaluating the insulation performance of AC polypropylene cables under impulse voltage is proposed. Using actual cable slices of AC polypropylene cables as the research object, the probabilistic breakdown field strength is obtained through a rise-fall method test. A lifetime model of the AC polypropylene insulation material is obtained through cumulative breakdown tests with multiple impulse voltages. Simultaneously, a cumulative loss characteristic model is constructed using the dielectric performance parameters measured after multiple impulse voltages as an aging model of the polypropylene insulation material under the cumulative effect of impulse voltage, characterizing the impact of multiple impulse voltages on the insulation material performance. This invention mainly focuses on the actual operating state and insulation performance degradation of power cables after impulse voltage. The proposed scheme can fully describe the breakdown characteristics, cumulative loss characteristics, and lifetime model of polypropylene under impulse voltage, thus providing guidance for the state assessment of power cables after being subjected to corresponding impulses in actual operation.

[0144] For better illustration, refer to Figure 8 This diagram illustrates the overall flow of a method for evaluating the insulation performance of AC polypropylene cables under impulse voltage, as provided in an embodiment of the present invention. It should be noted that this embodiment only provides a brief overview of the general process for evaluating the insulation performance of AC polypropylene cables under impulse voltage. The specific implementation process of each step can be understood by referring to the relevant content in the foregoing embodiments, and will not be elaborated upon here. It is understood that the present invention does not impose any limitations on this.

[0145] Step 801: Obtain cable slices and voltage rating data of AC polypropylene cable;

[0146] Step 802: Perform a breakdown test on the cable slice based on voltage rise and fall adjustment according to the voltage level data to obtain the breakdown probability and the breakdown voltage under the breakdown probability, and calculate the breakdown field strength under the breakdown probability based on the breakdown voltage, which is used as the probabilistic breakdown field strength of the polypropylene of the cable slice.

[0147] Step 803: Using the probabilistic breakdown field strength of polypropylene as a benchmark, conduct cumulative breakdown tests on the cable slices under multiple impulse voltages to obtain the UN characteristic curve between the impulse voltage amplitude U and the number of impulse voltages N. Based on the UN characteristic curve, perform linear fitting to obtain the life model of AC polypropylene cable under different impulse voltages.

[0148] Step 804: Perform cumulative breakdown tests on the cable slices under multiple impulse voltages to obtain the dielectric performance parameters of the AC polypropylene cable after being subjected to different impulse voltages, and construct an aging model of the AC polypropylene cable under different impulse voltages based on the dielectric performance parameters.

[0149] Step 805: Predict the lifespan of the AC polypropylene cable based on the lifespan model, and evaluate the insulation performance parameters of the AC polypropylene cable based on the aging model.

[0150] Reference Figure 9 The diagram illustrates a structural block diagram of an AC polypropylene cable insulation performance evaluation device under impulse voltage according to an embodiment of the present invention, which may specifically include:

[0151] The cable slice acquisition unit 901 is used to acquire cable slices of AC polypropylene cables;

[0152] The rise-fall test unit 902 is used to obtain the probabilistic breakdown field strength of the polypropylene of the cable slice based on the rise-fall test.

[0153] The lifetime model construction unit 903 is used to construct a lifetime model based on the probabilistic breakdown field strength of the polypropylene and the cumulative breakdown test under multiple impulse voltages; the lifetime model is used to predict the lifetime of the AC polypropylene cable.

[0154] The aging model construction unit 904 is used to perform dielectric performance testing on the cable slice by combining cumulative loss tests under multiple impulse voltages, and to construct an aging model; the aging model is used to evaluate the insulation performance parameters of the AC polypropylene cable.

[0155] In one optional embodiment, the lifting method test unit 902 includes:

[0156] The data acquisition unit is used to acquire voltage level data;

[0157] A breakdown test unit is used to perform a breakdown test on the cable slice based on voltage rise and fall adjustment according to the voltage level data, and to obtain the breakdown probability and the breakdown voltage at the breakdown probability.

[0158] The breakdown field strength calculation unit is used to calculate the breakdown field strength under the breakdown probability based on the breakdown voltage, which is the probabilistic breakdown field strength of the polypropylene of the cable slice.

[0159] In one optional embodiment, the voltage level data includes several voltage levels with increasing voltage differentials; the breakdown test unit includes:

[0160] The target voltage level selection unit is used to execute step S1: select a target voltage level in ascending order of voltage levels;

[0161] The multiple breakdown test voltage application unit is used to perform step S2: applying the multiple breakdown test voltage corresponding to the target voltage level to the cable slice one by one;

[0162] The voltage boost / down execution unit is used to execute step S3: determine whether a breakdown occurs during the voltage application process; if not, select the next voltage level of the current target voltage level as the new target voltage level and jump to execute step S2; if yes, select the previous voltage level of the current target voltage level as the new target voltage level and jump to execute step S2.

[0163] The breakdown voltage calculation unit is used to perform step S4: when all voltage levels of breakdown tests are completed, calculate the breakdown probability and the breakdown voltage at the breakdown probability based on the breakdown test results.

[0164] In one alternative embodiment, the lifetime model construction unit 903 includes:

[0165] The UN characteristic curve construction unit is used to conduct cumulative breakdown tests on the cable slice under multiple impulse voltages based on the probabilistic breakdown field strength of the polypropylene, and obtain the UN characteristic curve between the impulse voltage amplitude U and the number of impulse voltages N.

[0166] A linear fitting unit is used to perform linear fitting based on the UN characteristic curve to obtain the life model of the AC polypropylene cable under different impulse voltages.

[0167] In one alternative embodiment, the UN characteristic curve construction unit includes:

[0168] The impulse voltage amplitude determination unit is used to determine multiple impulse voltage amplitudes U based on the probabilistic breakdown field strength of the polypropylene and the breakdown voltage, with a preset voltage drop amplitude for step-wise voltage reduction.

[0169] An impulse voltage amplitude application unit is used to repeatedly apply the impulse voltage amplitude U to the cable slice for each impulse voltage amplitude U until the cable slice breaks down, and record the number of impulse voltages N.

[0170] The characteristic curve plotting unit is used to plot the UN characteristic curve between the impulse voltage amplitude U and the impulse voltage number N according to each impulse voltage amplitude U and the corresponding impulse voltage number N.

[0171] In one alternative embodiment, the aging model construction unit 904 includes:

[0172] The dielectric performance parameter measurement unit is used to perform a cumulative breakdown test on the cable slice under multiple impulse voltages to obtain the dielectric performance parameters of the AC polypropylene cable after being subjected to different impulse voltages; the dielectric performance parameters are used to evaluate the cumulative loss effect of multiple impulse voltages on the AC polypropylene cable.

[0173] An aging model construction subunit is used to construct an aging model of the AC polypropylene cable under different impulse voltages based on the dielectric performance parameters.

[0174] In one optional embodiment, the dielectric performance parameters include the breakdown field strength after impulse voltage, steady-state conduction current, isothermal relaxation depolarization current, and maximum space charge density; the aging model construction subunit includes:

[0175] The power frequency breakdown field strength model construction unit is used to construct a power frequency breakdown field strength model based on the impulse voltage amplitude, the number of impulse voltages, and the breakdown field strength; the power frequency breakdown field strength model is used to evaluate the remaining breakdown field strength of the AC polypropylene cable after the impulse voltage.

[0176] The conductivity current model construction unit is used to construct a conductivity current model based on the impulse voltage amplitude, the number of impulse voltages, and the steady-state conductivity current; the conductivity current model is used to evaluate the conductivity characteristics of the AC polypropylene cable after the impulse voltage.

[0177] An aging degree assessment model construction unit is used to calculate the insulation material life index after the impact voltage based on the fitting result of the isothermal relaxation depolarization current, and to construct an aging degree assessment model based on the impact voltage amplitude, the number of impact voltages and the insulation material life index; the aging degree assessment model is used to assess the aging degree of the AC polypropylene cable after the impact voltage.

[0178] The space charge model construction unit is used to construct a space charge model based on the impulse voltage amplitude, the number of impulse voltages, and the maximum space charge density; the space charge model is used to evaluate the space charge characteristics of the AC polypropylene cable after the impulse voltage.

[0179] The model integration unit is used to integrate the power frequency breakdown field strength model, the electrical conductivity current model, the aging degree assessment model, and the space charge model as the aging model of the AC polypropylene cable under different impulse voltages.

[0180] As the device embodiment is basically similar to the method embodiment, it is described in a relatively simple way. For relevant details, please refer to the description of the method embodiment above.

[0181] This invention also provides an electronic device, which includes a processor and a memory:

[0182] The memory is used to store program code and transfer the program code to the processor;

[0183] The processor is used to execute the insulation performance evaluation method of AC polypropylene cable under impulse voltage according to the instructions in the program code of any embodiment of the present invention.

[0184] This invention also provides a computer-readable storage medium for storing program code for executing the insulation performance evaluation method for AC polypropylene cables under impulse voltage according to any embodiment of this invention.

[0185] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0186] In the embodiments provided by this invention, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection between devices or units through some interfaces, and may be electrical, mechanical, or other forms.

[0187] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0188] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0189] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0190] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for evaluating the insulation performance of AC polypropylene cables under impulse voltage, characterized in that, include: Obtain cable slices of AC polypropylene cable; The probabilistic breakdown field strength of the polypropylene in the cable slice was obtained based on the rise-fall method test. Based on the probabilistic breakdown field strength of polypropylene, a lifetime model is constructed by combining cumulative breakdown tests under multiple impulse voltages; the lifetime model is used to predict the lifetime of the AC polypropylene cable. The dielectric properties of the cable slices were tested by combining cumulative loss tests under multiple impulse voltages to construct an aging model; the aging model was used to evaluate the insulation performance parameters of the AC polypropylene cable. The step of combining cumulative loss tests under multiple impulse voltages to perform dielectric performance testing on the cable slices and constructing an aging model includes: The cable slices were subjected to cumulative breakdown tests under multiple impulse voltages to obtain the dielectric performance parameters of the AC polypropylene cable after being subjected to different numbers of impulse voltages. The dielectric performance parameters include the breakdown field strength, steady-state conduction current, isothermal relaxation depolarization current, and maximum space charge density after the impulse voltage. The dielectric performance parameters are used to evaluate the cumulative loss effect of multiple impulse voltages on the AC polypropylene cable. Based on the impulse voltage amplitude, the number of impulse voltages, and the breakdown field strength, a power frequency breakdown field strength model is constructed; the power frequency breakdown field strength model is used to evaluate the remaining breakdown field strength of the AC polypropylene cable after the impulse voltage. A conductivity current model is constructed based on the impulse voltage amplitude, the number of impulse voltages, and the steady-state conductivity current; the conductivity current model is used to evaluate the conductivity characteristics of the AC polypropylene cable after the impulse voltage. Based on the fitting results of the isothermal relaxation depolarization current, the life index of the insulation material after the impact voltage is calculated, and an aging degree assessment model is constructed according to the impact voltage amplitude, the number of impact voltages, and the life index of the insulation material; the aging degree assessment model is used to assess the aging degree of the AC polypropylene cable after the impact voltage. A space charge model is constructed based on the impulse voltage amplitude, the number of impulse voltages, and the maximum space charge density; the space charge model is used to evaluate the space charge characteristics of the AC polypropylene cable after the impulse voltage. The power frequency breakdown field strength model, the electrical conductivity current model, the aging degree assessment model, and the space charge model are integrated to form the aging model of the AC polypropylene cable under different impulse voltages.

2. The insulation performance evaluation method according to claim 1, characterized in that, The probabilistic breakdown field strength of the polypropylene in the cable slice obtained based on the rise-fall method test includes: Obtain voltage level data; A breakdown test based on voltage rise and fall adjustment is performed on the cable slice according to the voltage level data to obtain the breakdown probability and the breakdown voltage at the breakdown probability. The breakdown field strength at the breakdown probability is calculated based on the breakdown voltage, and is used as the probabilistic breakdown field strength of the polypropylene in the cable slice.

3. The insulation performance evaluation method according to claim 2, characterized in that, The voltage level data includes several voltage levels with increasing voltage differentials; the step of performing a breakdown test on the cable slice based on voltage rise and fall adjustment according to the voltage level data to obtain the breakdown probability and the breakdown voltage at the breakdown probability includes: Step S1: Select a target voltage level in ascending order of voltage level; Step S2: Apply the multiple breakdown test voltage corresponding to the target voltage level to the cable slices one by one; Step S3: Determine whether a breakdown occurs during the voltage application process; if not, select the next voltage level after the current target voltage level as the new target voltage level and proceed to step S2; if yes, select the previous voltage level after the current target voltage level as the new target voltage level and proceed to step S2. Step S4: When all voltage levels of breakdown tests are completed, calculate the breakdown probability and the breakdown voltage at the breakdown probability based on the breakdown test results.

4. The insulation performance evaluation method according to claim 2, characterized in that, The process of constructing a lifetime model based on the probabilistic breakdown field strength of polypropylene and cumulative breakdown tests under multiple impact voltages includes: Based on the probabilistic breakdown field strength of the polypropylene, the cable slice was subjected to a cumulative breakdown test under multiple impulse voltages to obtain the UN characteristic curve between the impulse voltage amplitude U and the number of impulse voltages N. Based on the UN characteristic curve, a linear fitting was performed to obtain the life model of the AC polypropylene cable under different impulse voltages.

5. The insulation performance evaluation method according to claim 4, characterized in that, The method of using the probabilistic breakdown field strength of the polypropylene as a benchmark to conduct cumulative breakdown tests on the cable slices under multiple impulse voltages, and obtaining the UN characteristic curve between the impulse voltage amplitude U and the number of impulse voltages N, includes: Based on the probabilistic breakdown field strength of the polypropylene, and according to the breakdown voltage, multiple impact voltage amplitudes U are determined to perform a stepped voltage reduction with a preset voltage drop amplitude. For each of the aforementioned impulse voltage amplitudes U, the impulse voltage amplitude U is repeatedly applied to the cable slice until the cable slice breaks down, and the number of impulse voltage counts N is recorded. Based on each of the stated impulse voltage amplitudes U and their corresponding impulse voltage number N, plot the UN characteristic curve between the impulse voltage amplitude U and the impulse voltage number N.

6. A device for evaluating the insulation performance of AC polypropylene cables under impulse voltage, characterized in that, include: Cable slice acquisition unit, used to acquire cable slices of AC polypropylene cable; The rise-fall test unit is used to obtain the probabilistic breakdown field strength of the polypropylene in the cable slice based on the rise-fall test. The lifetime model construction unit is used to construct a lifetime model based on the probabilistic breakdown field strength of the polypropylene and the cumulative breakdown test under multiple impulse voltages; the lifetime model is used to predict the lifetime of the AC polypropylene cable. The aging model construction unit is used to test the dielectric properties of the cable slice by combining the cumulative loss test under multiple impulse voltages and construct the aging model. The aging model is used to evaluate the insulation performance parameters of the AC polypropylene cable. The aging model construction unit includes: The dielectric performance parameter measurement unit is used to perform cumulative breakdown tests on the cable slices under multiple impulse voltages to obtain the dielectric performance parameters of the AC polypropylene cable after being subjected to different numbers of impulse voltages. The dielectric performance parameters include the breakdown field strength, steady-state conduction current, isothermal relaxation depolarization current, and maximum space charge density after the impulse voltage is applied. The dielectric performance parameters are used to evaluate the cumulative loss effect of multiple impulse voltages on the AC polypropylene cable. The power frequency breakdown field strength model construction unit is used to construct a power frequency breakdown field strength model based on the impulse voltage amplitude, the number of impulse voltages, and the breakdown field strength; the power frequency breakdown field strength model is used to evaluate the remaining breakdown field strength of the AC polypropylene cable after the impulse voltage. The conductivity current model construction unit is used to construct a conductivity current model based on the impulse voltage amplitude, the number of impulse voltages, and the steady-state conductivity current; the conductivity current model is used to evaluate the conductivity characteristics of the AC polypropylene cable after the impulse voltage. An aging degree assessment model construction unit is used to calculate the insulation material life index after the impact voltage based on the fitting result of the isothermal relaxation depolarization current, and to construct an aging degree assessment model based on the impact voltage amplitude, the number of impact voltages and the insulation material life index; the aging degree assessment model is used to assess the aging degree of the AC polypropylene cable after the impact voltage. The space charge model construction unit is used to construct a space charge model based on the impulse voltage amplitude, the number of impulse voltages, and the maximum space charge density; the space charge model is used to evaluate the space charge characteristics of the AC polypropylene cable after the impulse voltage. The model integration unit is used to integrate the power frequency breakdown field strength model, the electrical conductivity current model, the aging degree assessment model, and the space charge model as the aging model of the AC polypropylene cable under different impulse voltages.

7. An electronic device, characterized in that, The device includes a processor and a memory: The memory is used to store program code and transmit the program code to the processor; The processor is configured to execute the insulation performance evaluation method for AC polypropylene cables under impulse voltage according to any one of the claims 1-5, based on the instructions in the program code.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium is used to store program code for executing the insulation performance evaluation method for AC polypropylene cables under impulse voltage as described in any one of claims 1-5.

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