Polypropylene cable insulation aging rapid evaluation method and system

Abstract

The present application relates to the field of high voltage and insulation technology, and particularly relates to a polypropylene cable insulation aging rapid evaluation method and system, the method comprising: setting a plurality of aging day gradients covering the initial, middle and late stages of polypropylene insulation layer aging; placing the cable segment in an aging test box for accelerated thermal aging test; measuring the hardness of samples with different aging days, taking the aging day corresponding to the maximum average hardness value as the demarcation point between the pre-middle and post-aging stages, respectively fitting the data of the pre-middle and post-aging stages to obtain the correlation equation of hardness and aging time conforming to the Arrhenius formula; stripping the outer sheath of the polypropylene cable to be detected to expose the insulation layer, selecting multiple points on the surface of the insulation layer to measure the hardness value and calculating the average value as the field hardness value; substituting the field hardness value into the correlation equation to calculate the equivalent aging time, and determining the aging degree of the insulation layer of the running polypropylene cable according to the equivalent aging time.

Description

Technical Field

[0001] This invention relates to the field of high voltage and insulation technology, and in particular to a method and system for rapid evaluation of insulation aging in polypropylene cables. Background Technology

[0002] Polypropylene (PP) materials possess excellent electrical insulation, heat resistance, and mechanical strength, and are recyclable. They are currently widely used in the preparation of insulation layers for power cables, becoming an important choice for insulation materials in medium- and low-voltage and high-voltage cables. During long-term operation, PP cables are affected by various factors such as ambient temperature, oxygen, and electric fields, leading to aging. Changes such as breakage and cross-linking of the molecular chains in the insulation layer occur, resulting in a decline in insulation performance. If the degree of aging is not detected in time, it may cause cable insulation breakdown, resulting in power transmission interruption and causing serious economic losses and safety hazards.

[0003] In existing technologies, methods for detecting the aging degree of polypropylene cable insulation are mainly divided into two categories: destructive testing and non-destructive testing. Destructive testing methods require cutting insulation samples from the operating cable and determining the aging degree through mechanical property tests such as tensile tests and impact tests, or through chemical analysis and thermal analysis. Although these methods provide accurate results, they damage the cable structure, cannot be used for on-site testing, and are cumbersome and time-consuming, making them unsuitable for large-scale cable maintenance and inspection.

[0004] Non-destructive testing methods mainly include electrical testing and infrared testing. Electrical testing determines the degree of aging by measuring electrical parameters such as insulation resistance and dielectric loss of cables, but the equipment cost is high, the field anti-interference ability is weak, and the professional requirements of the testing personnel are high. Infrared testing determines aging by detecting changes in the infrared spectrum of the insulation layer, but it is greatly affected by environmental interference and has limited detection accuracy.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the general background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] This invention provides a method and system for rapid evaluation of the aging of polypropylene cable insulation, thereby effectively solving the problems in the background art.

[0007] To achieve the above objectives, the technical solution adopted by this invention is: a method for rapid evaluation of the aging of polypropylene cable insulation, comprising the following steps: Select cables from the same batch as the polypropylene cables to be evaluated, cut multiple cable segments, and set multiple aging day gradients for the initial, middle, and late stages of aging of the polypropylene insulation layer. The insulation sample of the cable segment was placed in an aging test chamber for accelerated thermal aging test. After aging, the sample was cooled to room temperature. Hardness was measured on samples with different aging days to obtain the average hardness value corresponding to each aging day. The aging day corresponding to the largest average hardness value was used as the dividing point between the early and middle stages of aging and the late stage of aging. Data fitting was performed on the early and middle stages of aging and the late stage of aging to obtain the correlation equation between hardness and aging time that conforms to the Arrhenius formula. The outer sheath of the polypropylene cable to be tested is peeled off to expose the insulation layer. Multiple points are selected on the surface of the insulation layer to measure the hardness value and the average value is calculated as the field hardness value. After the measurement is completed, the outer sheath is restored. Substituting the field hardness value into the correlation equation, the equivalent aging time is calculated, and the aging degree of the polypropylene cable insulation layer is determined based on the equivalent aging time.

[0008] Furthermore, prior to the accelerated thermal aging test, the method further includes: detecting the melting point of the cable segment insulation layer; setting the aging temperature to 150°C when the melting point is greater than 150°C; and setting the aging temperature to 135°C when the melting point is less than 150°C.

[0009] Furthermore, the aging days gradient is set every 7 days starting from day 0, with the aging endpoint being the sample's elongation at break decreasing to 50% of the initial value.

[0010] Furthermore, the hardness measurement is performed using a Shore D hardness tester. Hardness values ​​are measured at no less than 3 points for each sample, with a distance of no less than 6 mm between the points. The average value of the measured values ​​at each point is calculated as the average hardness value of the sample.

[0011] Furthermore, the correlation equation between hardness and aging time, which conforms to the Arrhenius formula, is as follows: ; In the formula, This is the hardness value, measured in HD. The aging time is expressed in days, and A and B are fitting constants. The activation energy for polypropylene thermo-oxidative aging. Boltzmann's constant is . , The absolute aging temperature is expressed in Kelvin (K).

[0012] Furthermore, the goodness of fit of the data is R²≥0.9; the correlation equation in the early and middle stages of aging reflects the law that hardness increases with aging time, while the correlation equation in the later stage of aging reflects the law that hardness decreases with aging time.

[0013] Furthermore, the cooling to room temperature includes: placing the aged sample in a room temperature environment for natural cooling for 24 hours to restore the sample temperature to 23±2℃.

[0014] Furthermore, the process of stripping the outer sheath of the polypropylene cable under test to expose the insulation layer includes: Use specialized tools to peel off the outer sheath while avoiding damage to the insulation layer. Clean the surface of the insulation layer of oil and debris, avoiding areas with scratches or damage, and select a flat area for measurement. The restoration of the outer sheath includes: using the same material as the original outer sheath, restoring the outer sheath according to the original cable structure standards, and ensuring that the insulation and mechanical properties of the cable after restoration are consistent with those before treatment.

[0015] Furthermore, determining the degree of aging of the insulation layer of the operating polypropylene cable also includes: The actual service life of the polypropylene cable is obtained, and the equivalent aging time is combined with the actual service life to comprehensively determine the aging degree of the cable insulation layer and assess future performance changes.

[0016] The present invention also includes a rapid evaluation device for the insulation aging of polypropylene cables, using the method described above, wherein the device comprises: The sample preparation module is used to select cables from the same batch as the polypropylene cables to be evaluated, cut multiple cable segments, and set multiple aging day gradients. The accelerated aging module is used to place the insulation layer sample of the cable segment in the aging test chamber for accelerated thermal aging test, and cool the sample to room temperature after aging is completed; The hardness measurement and fitting module is used to measure the hardness of samples with different aging days to obtain the average hardness value. The aging days corresponding to the maximum average hardness value are used as the dividing point. Data fitting is performed on the early, middle and late stages of aging to obtain the correlation equation between hardness and aging time that conforms to the Arrhenius formula. The on-site testing module is used to peel off the outer sheath of the polypropylene cable under test to expose the insulation layer, measure the hardness value at multiple points on the surface of the insulation layer and calculate the average value as the on-site hardness value, and restore the outer sheath after the measurement is completed. The aging determination module is used to substitute the on-site hardness value into the correlation equation to calculate the equivalent aging time, and to determine the degree of aging of the cable insulation layer based on the equivalent aging time.

[0017] The beneficial effects of this invention are as follows: This invention solves the problems of destructiveness, expensive equipment, and complex operation of existing detection methods, clarifies the correlation principle between hardness and aging, obtains a mathematical equation that conforms to the Arrhenius formula through data fitting, clarifies the detection method, and realizes a rapid, low-cost, and accurate evaluation of the aging degree of polypropylene cable insulation layer. Attached Figure Description

[0018] 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 recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a schematic diagram of the system structure of the present invention; Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0021] Example 1: like Figure 1 As shown: A rapid evaluation method for insulation aging of polypropylene cables includes the following steps: Select cables from the same batch as the polypropylene cables to be evaluated, cut multiple cable segments, and set multiple aging day gradients for the initial, middle, and late stages of aging of the polypropylene insulation layer. The insulation sample of the cable section was placed in an aging test chamber for accelerated thermal aging test. After aging, the sample was cooled to room temperature. Hardness was measured on samples with different aging days to obtain the average hardness value corresponding to each aging day. The aging day corresponding to the maximum average hardness value was used as the dividing point between the early and middle stages of aging and the late stage of aging. Data fitting was performed on the early and middle stages of aging and the late stage of aging to obtain the correlation equation between hardness and aging time that conforms to the Arrhenius formula. The outer sheath of the polypropylene cable to be tested is peeled off to expose the insulation layer. Multiple points on the surface of the insulation layer are selected to measure the hardness value and the average value is calculated as the field hardness value. After the measurement is completed, the outer sheath is restored. Substituting the on-site hardness value into the correlation equation, the equivalent aging time is calculated, and the degree of aging of the polypropylene cable insulation layer is determined based on the equivalent aging time.

[0022] This embodiment solves the problems of destructiveness, expensive equipment, and complex operation of existing detection methods. It clarifies the correlation principle between hardness and aging, obtains a mathematical equation that conforms to the Arrhenius formula through data fitting, clarifies the detection method, and realizes a rapid, low-cost, and accurate evaluation of the aging degree of polypropylene cable insulation layer.

[0023] Before the accelerated thermal aging test, the following steps are also included: testing the melting point of the cable section insulation layer. When the melting point is greater than 150°C, the aging temperature is set to 150°C; when the melting point is less than 150°C, the aging temperature is set to 135°C.

[0024] The aging days gradient starts from day 0 and is set every 7 days, with the aging endpoint being when the sample's elongation at break drops to 50% of the initial value.

[0025] In this embodiment, a Shore D hardness tester is used to measure the hardness of each sample. The hardness values ​​at no less than 3 points are measured, and the distance between the points is no less than 6 mm. The average value of the measured values ​​at each point is calculated as the average hardness value of the sample.

[0026] As a preferred embodiment of the above, the correlation equation between hardness and aging time, conforming to the Arrhenius formula, is as follows: ; In the formula, This is the hardness value, measured in HD. The aging time is expressed in days, and A and B are fitting constants. The activation energy for polypropylene thermo-oxidative aging. Boltzmann's constant is . , The absolute aging temperature is expressed in Kelvin (K).

[0027] Among them, the goodness of fit of the data R² ≥ 0.9; the correlation equation in the early and middle stages of aging reflects the law that hardness increases with aging time, while the correlation equation in the later stage of aging reflects the law that hardness decreases with aging time.

[0028] As a preferred embodiment of the above, cooling to room temperature includes: placing the aged sample in a room temperature environment for natural cooling for 24 hours to restore the sample temperature to 23±2℃.

[0029] In this embodiment, stripping the outer sheath of the polypropylene cable under test to expose the insulation layer includes: Use specialized tools to peel off the outer sheath while avoiding damage to the insulation layer. Clean the surface of the insulation layer of oil and debris, avoiding areas with scratches or damage, and select a flat area for measurement. Restoring the outer sheath includes using materials consistent with the original outer sheath and restoring the outer sheath according to the original cable structure standards to ensure that the insulation and mechanical properties of the cable after restoration are consistent with those before treatment.

[0030] As a preferred embodiment of the above embodiments, determining the degree of aging of the insulation layer of the operating polypropylene cable further includes: The actual service life of the polypropylene cable is obtained, and the equivalent aging time is combined with the actual service life to comprehensively judge the aging degree of the cable insulation layer and assess future performance changes.

[0031] like Figure 2 As shown, this embodiment also includes a rapid evaluation device for the insulation aging of polypropylene cables, using the method described above. The device includes: The sample preparation module is used to select cables from the same batch as the polypropylene cables to be evaluated, cut multiple cable segments, and set multiple aging day gradients. The accelerated aging module is used to place the insulation layer sample of the cable segment in the aging test chamber for accelerated thermal aging test, and cool the sample to room temperature after aging is completed; The hardness measurement and fitting module is used to measure the hardness of samples with different aging days to obtain the average hardness value. The aging days corresponding to the maximum average hardness value are used as the dividing point. Data fitting is performed on the early, middle and late stages of aging to obtain the correlation equation between hardness and aging time that conforms to the Arrhenius formula. The on-site testing module is used to peel off the outer sheath of the polypropylene cable under test to expose the insulation layer, measure the hardness value at multiple points on the surface of the insulation layer and calculate the average value as the on-site hardness value, and restore the outer sheath after the measurement is completed. The aging determination module is used to substitute the on-site hardness value into the correlation equation to calculate the equivalent aging time, and to determine the degree of aging of the cable insulation layer based on the equivalent aging time.

[0032] The beneficial effects of this embodiment are as follows: (1) Recoverability: The cable treatment only involves stripping the outer sheath to expose the insulation layer without damaging the insulation layer itself. After the measurement is completed, the original structure of the cable can be restored without affecting the subsequent normal operation of the cable, thus solving the drawbacks of existing destructive testing. (2) Clear principle and accurate judgment: The linear relationship between hardness and polypropylene crystallinity is clarified, as well as the Arrhenius variation law of crystallinity and aging time. A standardized mathematical equation is obtained through data fitting. The degree of aging can be accurately determined by substituting the hardness value on site into the equation, which solves the problem of insufficient accuracy of existing methods. (3) Simple and fast operation: The detection process only requires three core steps: processing the cable, measuring hardness, and substituting into the equation for calculation. The operation is simple and the detection time for a single cable is short, making it suitable for large-scale cable operation and maintenance detection. (4) Low cost: The test can be completed using a conventional Shore hardness tester. The equipment cost is low, and there is no need for complicated testing instruments and professional testing personnel, which can significantly reduce the cost of cable operation and maintenance testing.

[0033] Example 2: This specific embodiment provides a rapid detection method for insulation aging of polypropylene cables, and the specific implementation steps are as follows: 1. Preliminary preparations Select cables from the same batch as the polypropylene cables to be evaluated, and cut multiple cable segments of the same length to ensure that the conductor, inner and outer shielding, and insulation layer of each cable segment are intact, without damage, defects, or oil stains, so as to avoid affecting the test results due to incomplete structure. At the same time, test the melting point of the insulation layer of this batch of polypropylene cables to determine whether it is high-melting-point polypropylene insulation with a melting point >150℃ or low-melting-point polypropylene insulation with a melting point <150℃, so as to set the corresponding high-temperature accelerated thermal aging temperature.

[0034] Prepare the testing equipment: an aging test chamber that meets the temperature control accuracy of ±1℃ and is suitable for the thermal accelerated aging test requirements of polypropylene materials; a Shore D hardness tester with an accuracy of 0.1HD to ensure the accuracy of hardness measurement, and the hardness tester needs to be calibrated regularly to ensure the accuracy of the measuring instrument.

[0035] 2. Accelerated aging test

[0036] The prepared polypropylene insulation layer samples were placed in an aging test chamber. If the sample was high-melting-point polypropylene, the aging temperature was set to 150℃; if the sample was low-melting-point polypropylene, the aging temperature was set to 135℃. The test was conducted according to GB / T 7141, the accelerated aging test method for plastics in hot air. Multiple different aging day gradients were set, specifically starting from day 0 (unaged) and increasing in increments of 7 days until the elongation at break of the sample decreased to 50% of its initial value.

[0037] After the parallel samples corresponding to each aging day have completed the aging test, the samples should be taken out in time and placed in a room temperature environment to cool naturally for 24 hours to allow the sample temperature to recover to 23±2℃, so as to avoid the temperature difference affecting the hardness measurement results.

[0038] 3. Hardness Measurement and Data Fitting

[0039] The hardness of polypropylene insulation layer samples with different aging days was measured according to GB / T 39693.4-2025 Shore hardness test method for plastics.

[0040] During measurement, place a sample with a total thickness of not less than 6 mm on a flat, hard surface. Without vibration, press the indenter onto the sample as quickly as possible, at least 12 mm from any edge of the sample, or vice versa, keeping the indenter and sample surface parallel so that the indenter is perpendicular to the rubber surface. Once the indenter and sample are in close contact, maintain the pressure and take the reading after 15 seconds. Measure the hardness at three different points on each sample, with a minimum distance of 6 mm between the points. Calculate the average of the three measurements as the average hardness value of the polypropylene insulation sample after that number of aging days.

[0041] After completing the hardness measurements for all samples with varying aging days, based on the core principle that "hardness is linearly correlated with polypropylene crystallinity, and crystallinity and aging time conform to the Arrhenius equation," the aging days corresponding to the highest hardness value were used as the dividing points for the pre-aging, mid-aging, and late-aging stages. Linear regression fitting was then performed on the correlation data between the aging days and the corresponding average hardness values ​​for the pre-aging, mid-aging, and late-aging stages, using the Arrhenius equation, which is in the following form: (1) in, This refers to the hardness value (HD). Where A is the aging time (days), and B are fitting constants. The activation energy for polypropylene thermo-oxidative aging is 0.9 eV. Boltzmann constant ( ), The absolute temperature for aging is (K).

[0042] When the actual running time is less than or equal to the breakpoint time: (2) When the actual running time is greater than the breakpoint time: (3) During the fitting process, ensure that the goodness of fit R² ≥ 0.9 to guarantee the reliability of the formula.

[0043] 4. On-site testing

[0044] For the polypropylene cable to be tested, after stopping the relevant maintenance operations, the following steps should be taken: First, use a special tool to peel off the outer sheath of the cable to expose the insulation layer. During the peeling process, strictly avoid damaging the surface and internal structure of the insulation layer to ensure that the insulation layer is intact. Use a clean, soft cloth to clean the surface of the insulation layer of oil, dust, debris, etc. If there are obvious scratches or damages on the surface of the insulation layer that affect the measurement accuracy, avoid that area and select a flat, undamaged area for measurement.

[0045] Using the same model and calibrated Shore D hardness tester as in previous tests, and without vibration, press the indenter onto the sample as quickly as possible, at a distance of at least 12 mm from any edge, or vice versa, keeping the indenter and sample surface parallel so that the indenter is perpendicular to the rubber surface. Once the indenter and sample are in close contact, maintain the pressure and take the reading after 15 seconds. Measure the hardness value at three different points on each sample, with a minimum distance of 6 mm between the points. Select at least three measurement points on the cable insulation surface, evenly distributed among them, and maintain the same measurement pressure as in previous sample measurements to avoid deviations due to pressure variations.

[0046] The hardness value of each measurement point was measured sequentially, and the measurement data of all points were recorded. The average value of the measurements from multiple points was calculated as the field hardness value of the polypropylene cable insulation layer in operation. After the measurement was completed, the cable outer sheath was restored using a material consistent with the original outer sheath material, according to the original cable structure standard. After restoration, the insulation performance and mechanical properties of the cable were checked to ensure that they were consistent with those before the treatment and would not affect subsequent normal operation.

[0047] V. Determination of Aging Level

[0048] 1. Substitute the measured hardness value of the cable insulation layer into the mathematical equation obtained in step 3 to calculate the corresponding equivalent aging time. Based on the position of the measured cable hardness on the Arrhenius curve and combined with the actual number of days the cable has been in operation, determine the degree of aging of the cable insulation layer, assess future performance changes, and guide the maintenance of cable operation.

[0049] Example 3: In this embodiment, a batch of 35kV polypropylene cables in operation was selected for evaluation. Multiple cable segments of uniform length were cut to ensure that the conductor, inner and outer shielding, and insulation layer of each cable segment were intact, without damage, defects, or oil contamination. Since the insulation layer of this cable is made of high-melting-point polypropylene, an aging temperature of 150℃ was selected.

[0050] Accelerated aging tests were conducted at 150℃ for 0, 7, 14, 21, 28, 35, and 42 days (tests showed that the elongation at break of the sample decreased to less than 50% of its initial value by day 49 of aging). After aging, the samples were naturally cooled to 23℃, and the hardness values ​​of each group of samples were measured using a Shore D hardness tester (accuracy 0.1HD), and the average value was taken. The measurement results are as follows: 0-day (unaged) hardness value 43.67HD, 7-day hardness value 46.00HD, 14-day hardness value 48.00HD, 21-day hardness value 47.33HD, 28-day hardness value 46.00HD, 35-day hardness value 46.00HD, and 42-day hardness value 45.33HD. It can be seen that the highest hardness corresponds to day 14. Assuming the normal operating temperature of the cable is 60℃, the actual aging period corresponding to 14 days is calculated to be 5.18 years according to the Arrhenius equation.

[0051] Therefore, the fitting formula is: when the actual operating days of the cable are ≤ 5.18 years (4) When the actual number of days the cable has been in operation exceeds 5.18 years (5) In the formula This represents the measured hardness value (HD) of the cable. Equivalent aging time of the cable (days).

[0052] Substitute the field hardness value of the cable insulation obtained from on-site measurements into the above formula to calculate the corresponding equivalent aging time. This allows for the assessment of the aging degree of the cable insulation and evaluation of future performance changes, guiding the maintenance of the cable operation.

[0053] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. "A plurality of" means two or more, unless otherwise explicitly specified.

[0054] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0055] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0056] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0057] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0058] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0059] Those skilled in the art will understand that all or part of the steps of the methods described in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it includes one or a combination of the steps of the method embodiments.

[0060] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A rapid evaluation method for the insulation aging of polypropylene cables, characterized in that, Includes the following steps: Select cables from the same batch as the polypropylene cables to be evaluated, cut multiple cable segments, and set multiple aging day gradients for the initial, middle, and late stages of aging of the polypropylene insulation layer. The insulation sample of the cable segment was placed in an aging test chamber for accelerated thermal aging test. After aging, the sample was cooled to room temperature. Hardness was measured on samples with different aging days to obtain the average hardness value corresponding to each aging day. The aging day corresponding to the largest average hardness value was used as the dividing point between the early and middle stages of aging and the late stage of aging. Data fitting was performed on the early and middle stages of aging and the late stage of aging to obtain the correlation equation between hardness and aging time that conforms to the Arrhenius formula. The outer sheath of the polypropylene cable to be tested is peeled off to expose the insulation layer. Multiple points are selected on the surface of the insulation layer to measure the hardness value and the average value is calculated as the field hardness value. After the measurement is completed, the outer sheath is restored. Substituting the field hardness value into the correlation equation, the equivalent aging time is calculated, and the aging degree of the polypropylene cable insulation layer is determined based on the equivalent aging time.

2. The method according to claim 1, characterized in that, Before the accelerated thermal aging test, the method further includes: detecting the melting point of the cable segment insulation layer, setting the aging temperature to 150°C when the melting point is greater than 150°C, and setting the aging temperature to 135°C when the melting point is less than 150°C.

3. The method according to claim 2, characterized in that, The aging days gradient starts from day 0 and is set every 7 days, with the aging endpoint being when the sample's elongation at break drops to 50% of the initial value.

4. The method according to claim 3, characterized in that, The hardness was measured using a Shore D hardness tester. Hardness values ​​were measured at no less than 3 points for each sample, with a distance of no less than 6 mm between the points. The average value of the measured values ​​at each point was calculated as the average hardness value of the sample.

5. The method according to claim 1, characterized in that, The equation relating hardness and aging time, which conforms to the Arrhenius formula, is as follows: ； In the formula, This is the hardness value, measured in HD. The aging time is expressed in days, and A and B are fitting constants. The activation energy for polypropylene thermo-oxidative aging. Boltzmann's constant is . , The absolute aging temperature is expressed in Kelvin (K).

6. The method according to claim 5, characterized in that, The goodness of fit of the data is R²≥0.9; the correlation equations in the early and middle stages of aging reflect the law that hardness increases with aging time, while the correlation equations in the later stages of aging reflect the law that hardness decreases with aging time.

7. The method according to claim 1, characterized in that, The cooling to room temperature includes: placing the aged sample in a room temperature environment for natural cooling for 24 hours to restore the sample temperature to 23±2℃.

8. The method according to claim 1, characterized in that, The process of stripping the outer sheath of the polypropylene cable under test to expose the insulation layer includes: Use specialized tools to peel off the outer sheath while avoiding damage to the insulation layer. Clean the surface of the insulation layer of oil and debris, avoiding areas with scratches or damage, and select a flat area for measurement. The restoration of the outer sheath includes: using the same material as the original outer sheath, restoring the outer sheath according to the original cable structure standards, and ensuring that the insulation and mechanical properties of the cable after restoration are consistent with those before treatment.

9. The method according to any one of claims 1 to 8, characterized in that, The determination of the aging degree of the insulation layer of the operating polypropylene cable also includes: The actual service life of the polypropylene cable is obtained, and the equivalent aging time is combined with the actual service life to comprehensively determine the aging degree of the cable insulation layer and assess future performance changes.

10. A rapid evaluation device for the insulation aging of polypropylene cables, characterized in that, Using the method as described in any one of claims 1 to 9, the apparatus comprises: The sample preparation module is used to select cables from the same batch as the polypropylene cables to be evaluated, cut multiple cable segments, and set multiple aging day gradients. The accelerated aging module is used to place the insulation layer sample of the cable segment in the aging test chamber for accelerated thermal aging test, and cool the sample to room temperature after aging is completed; The hardness measurement and fitting module is used to measure the hardness of samples with different aging days to obtain the average hardness value. The aging days corresponding to the maximum average hardness value are used as the dividing point. Data fitting is performed on the early, middle and late stages of aging to obtain the correlation equation between hardness and aging time that conforms to the Arrhenius formula. The on-site testing module is used to peel off the outer sheath of the polypropylene cable under test to expose the insulation layer, measure the hardness value at multiple points on the surface of the insulation layer and calculate the average value as the on-site hardness value, and restore the outer sheath after the measurement is completed. The aging determination module is used to substitute the on-site hardness value into the correlation equation to calculate the equivalent aging time, and to determine the degree of aging of the cable insulation layer based on the equivalent aging time.

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