Method for analyzing storage reliability of metalized polyethylene film high-voltage capacitor

Abstract

The invention relates to the technical field of capacitor reliability evaluation, and discloses a metallized polyethylene film high-voltage capacitor storage reliability analysis method, which comprises the following steps: simulating different storage environments covering temperature, humidity and air pressure changes; periodically detecting a capacitance value, a dielectric loss value, an insulation resistance and a partial discharge amount; classifying detection data, drawing a change curve, calculating a change rate, associating environment analysis, forming a performance degradation rule, and judging whether the performance is degraded or not; and the reliability is evaluated by combining the environment and the degradation law, and the reliable storage duration in the set environment is determined. According to the method, the storage environment fits the actual working condition, the performance degradation can be accurately identified, the reliable storage duration can be quantified, and the use safety and usability of the capacitor after storage in the key field are guaranteed.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of capacitor reliability evaluation, and particularly relates to a storage reliability analysis method for a metallized polyethylene film high-voltage capacitor. BACKGROUND

[0002] The metallized polyethylene film high-voltage capacitor is widely used in key fields such as power systems and new energy storage due to low dielectric loss and excellent voltage resistance performance, and storage is a key requirement for ensuring its usability. A large number of capacitors need to be stored for a long time as backup devices or go through the storage link in the production circulation. Environmental changes during storage can easily lead to performance degradation, which directly affects the subsequent use reliability.

[0003] In the prior art, the storage reliability analysis of such capacitors is mostly based on a single fixed environment for evaluation, which cannot simulate the dynamic changes of temperature, humidity and air pressure in the actual storage, resulting in a significant deviation between the evaluation results and the actual storage reliability. In addition, the correlation between the storage environment conditions and the performance degradation law cannot be clearly determined, which makes it difficult to locate the degradation causes and optimize the storage scheme.

[0004] Therefore, there is an urgent need for a reliable storage reliability analysis technology. SUMMARY

[0005] The application aims to provide a storage reliability analysis method for a metallized polyethylene film high-voltage capacitor to solve the technical problems in the background.

[0006] To achieve the above-mentioned purpose, the application discloses the following technical solution: a storage reliability analysis method for a metallized polyethylene film high-voltage capacitor, comprising:

[0007] Step 1: simulate the storage state of the metallized polyethylene film high-voltage capacitor under different storage environment conditions, wherein the storage environment conditions at least include temperature, humidity and air pressure changes;

[0008] Step 2: periodically detect the core performance indicators of the capacitor during the storage process, wherein the core performance indicators at least include capacitance value, dielectric loss value, insulation resistance and partial discharge amount;

[0009] Step 3: process the detected core performance indicator data, classify and arrange the indicator data at different storage stages, draw the change curve of each core performance indicator with the storage time, calculate the change rate of each core performance indicator, and perform correlation analysis based on the storage environment conditions to obtain the change characteristics of each core performance indicator with the storage time, form a performance degradation law based on the change characteristics, and then judge whether the capacitor performance has degraded through the performance degradation law;

[0010] Step 4: Based on the storage environment conditions and the performance degradation rules, the storage reliability of the capacitor is evaluated, and the reliable storage time of the capacitor in the set storage environment is determined.

[0011] Preferably, the storage state of the simulated metallized polyethylene film high-voltage capacitor under different storage environment conditions includes:

[0012] According to the preset time period, different temperature, humidity and pressure combinations are alternately switched to form a dynamically changing storage environment, and after each environment switching, the environment conditions are maintained until the start node of the next preset time period.

[0013] Preferably, the index data of different storage stages is sorted, including:

[0014] According to the change gradient of the storage environment conditions, the storage stages are divided, the storage process in the same environment parameter interval is defined as the same stage, and the core performance index data of all detection times in the stage is sorted to form a corresponding relationship between the environment parameter interval and the index data group.

[0015] Preferably, the correlation analysis based on the storage environment conditions includes:

[0016] For each environment parameter interval and index data group, the temperature fluctuation range, humidity stable time length and pressure change trend in the environment parameter interval are matched, the correlation between the temperature fluctuation range, humidity stable time length and pressure change trend and the change rate of the core performance index in the corresponding index data group is analyzed, and the influence direction of the three factors of temperature fluctuation, humidity stable state and pressure change on the change of each core performance index is determined.

[0017] Preferably, the change rate of each core performance index is calculated, including:

[0018] Taking the index data at the start time of each storage stage as the reference value, the change proportion of the index data at each detection time in the stage relative to the reference value is calculated to obtain the stage change rate.

[0019] Taking the index data at the initial storage time as the total reference value, the change proportion of the index data at each detection time relative to the total reference value is calculated to obtain the cumulative change rate.

[0020] Preferably, the change characteristics of each core performance index with storage time are obtained, including:

[0021] By comparing the stage change rates of different storage stages, the change trend of each core performance index is determined, the continuous storage time of the change trend and the change amplitude of the corresponding stage are counted, and the time when the stage change rate exceeds the preset difference threshold compared with the previous stage is marked to integrate the change characteristics of each core performance index.

[0022] As preferred, the judging whether the capacitor performance appears degradation through the performance degradation rule comprises:

[0023] If the cumulative change rate of any core performance index in the performance degradation rule reaches the preset degradation judging threshold, or the stage change rate of at least two core performance indexes continuously in multiple storage stages exceeds the change rate in the initial storage stage, it is determined that the capacitor performance appears degradation.

[0024] As preferred, the periodically detecting the core performance index of the capacitor comprises:

[0025] In each preset time period, the detection of the core performance index is performed once at the starting time, the middle time and the ending time respectively; before each detection, the capacitor is first placed in a detection environment and kept until the temperature is consistent with the detection environment, and then the detection equipment suitable for the characteristics of each index is used to collect data; wherein the core performance index is collected multiple times, and the average of the multiple collection results is taken as the core performance index data at the time.

[0026] As preferred, the detection of the capacitance value is based on the alternating current capacitance bridge method, and the stable capacitance value is obtained by adjusting the bridge balance;

[0027] The detection of the dielectric loss value is based on the phase difference comparison method, and the influence of external electromagnetic interference on the measurement result is reduced through the shielding structure;

[0028] The detection of the insulation resistance is based on the high resistance meter constant voltage method, and the value is recorded after a constant direct current voltage is applied and kept until the reading is stable;

[0029] The detection of the partial discharge quantity is based on the pulse current method, and the detection sensitivity is improved through signal amplification and filtering.

[0030] As preferred, the determining the reliable storage duration of the capacitor in the set storage environment comprises:

[0031] A fitting relationship of the core performance index changing with the storage time is constructed based on the performance degradation rule, and a preset failure judging standard of the capacitor performance is set;

[0032] The storage time corresponding to the failure judging standard of each core performance index is found in the fitting relationship, and the shortest time is taken as the reliable storage duration of the capacitor in the set storage environment.

[0033] Beneficial effects: the metalized polyethylene film high-voltage capacitor storage reliability analysis method of the application can simulate the storage state of the metalized polyethylene film high-voltage capacitor under different storage environment conditions, regularly detect the core performance indicators during the storage process, process the detection data to form the performance degradation rule and judge whether the performance is degraded, finally evaluate the storage reliability and determine the reliable storage time length under the set storage environment in combination with the storage environment condition and the performance degradation rule, so as to make the capacitor storage reliability evaluation fit the actual storage scene, accurately identify the performance degradation, at the same time provide clear basis for the reliable storage time length under the set storage environment, and effectively guarantee the use reliability of the capacitor after storage. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0035] Figure 1 The flow chart of the metalized polyethylene film high-voltage capacitor storage reliability analysis method provided by the embodiments of the present application. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0037] In this paper, the term "including" is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. Without more limitations, the elements defined by the statement "including" do not exclude the presence of other identical elements in the process, method, article or equipment including the elements.

[0038] The embodiments disclose a metalized polyethylene film high-voltage capacitor storage reliability analysis method as shown in Figure 1 The method aims to solve the problems in the prior art, such as disconnection between environment simulation and actual scene, unclear performance degradation rule, and difficulty in accurately determining the reliable storage time length, etc. The method comprises:

[0039] Step 1: Simulate the storage state of the metallized polyethylene film high-voltage capacitor under different storage environmental conditions, which at least include temperature, humidity and air pressure changes.

[0040] Step 2: During the storage process, periodically detect the core performance indicators of the capacitor, which at least include capacitance value, dielectric loss value, insulation resistance and partial discharge amount.

[0041] Step 3: Process the core performance indicator data obtained by detection, classify and arrange the indicator data at different storage stages, draw the change curve of each core performance indicator with storage time, calculate the change rate of each core performance indicator, and perform correlation analysis based on the storage environmental conditions to obtain the change characteristics of each core performance indicator with storage time. Based on the change characteristics, form the performance degradation law, and then judge whether the capacitor performance has degraded through the performance degradation law.

[0042] Step 4: Based on the storage environmental conditions and the performance degradation law, evaluate the storage reliability of the capacitor and determine its reliable storage duration under the set storage environment.

[0043] Based on the above, the metallized polyethylene film high-voltage capacitor storage reliability analysis method of the embodiment simulates different storage environments, periodically detects core indicators, processes data to form a performance degradation law, evaluates reliability and determines a reliable storage duration through a complete logical chain. It solves the core shortcomings of the prior art, such as single environment simulation, ambiguous degradation judgment, inability to correlate environment and performance, and no clear reliable duration. It achieves the overall effect of realistic storage environment, accurate performance degradation identification, environment and degradation law correlation, and reliable duration quantification, providing a systematic solution for metallized polyethylene film high-voltage capacitor storage reliability evaluation, and ensuring the safety and usability of the device after storage.

[0044] In the embodiment, the storage state of the metallized polyethylene film high-voltage capacitor under different storage environmental conditions is simulated, including:

[0045] According to the preset time period, different temperature, humidity and air pressure combinations are alternately switched to form a dynamically changing storage environment, and after each environmental switch, the environmental conditions are maintained until the start node of the next preset time period.

[0046] It is feasible that the temperature change range can be set to -40°C to 70°C (covering high latitude low temperature, high temperature in tropical and warehouse air conditioning fluctuation scene), the humidity change range is 10% RH to 95% RH (covering arid areas, high humidity along the coast and poor ventilation in the warehouse), and the air pressure change range is 80kPa to 101kPa (covering plains, plateaus and closed warehouse air pressure fluctuations). The dynamic environment simulation alternately switches the above parameter combinations according to the preset time period (such as 30 days / period), for example: the first period uses (25°C, 50% RH, 101kPa), the second period switches to (40°C, 80% RH, 95kPa), and after each switch, the environment is maintained until the next period starts, to reproduce the phase fluctuation characteristics of the environmental parameters in actual storage.

[0047] Based on the above, the metalized polyethylene film high-voltage capacitor storage reliability analysis method of the embodiment accurately reproduces the seasonal temperature and humidity fluctuations and the phase stability of the air pressure in actual storage (such as high temperature and high humidity for 1 month in summer, low temperature and low humidity for 1 month in winter), avoids the evaluation deviation caused by single fixed environment or irregular frequent switching environment in the prior art, and makes the subsequent performance test data more consistent with the real storage working condition, thereby laying an environmental simulation foundation for the accuracy of subsequent performance degradation rule analysis.

[0048] Further, the index data of different storage stages are classified and arranged, including:

[0049] According to the change gradient of the storage environment conditions, the storage stages are divided, the storage process in the same environmental parameter interval is defined as the same stage, and the core performance index data at all detection times in the stage are correspondingly arranged, to form the corresponding relationship between the environmental parameter interval and the index data group.

[0050] It is feasible that the storage stage division is specifically: the stages are divided according to the change gradient of the environmental parameters, for example, when the temperature fluctuation exceeds ±3°C, the humidity fluctuation exceeds ±10% RH or the air pressure fluctuation exceeds ±5kPa, it is determined that a new stage is entered; the environmental parameter fluctuation in the same stage is within the above range, such as (30°C±3°C, 60% RH±10%, 100kPa±5kPa) can be classified into the same environmental parameter interval, and all detection data in the stage are correspondingly arranged, to provide a basis for subsequent correlation analysis.

[0051] Based on the above, the metalized polyethylene film high-voltage capacitor storage reliability analysis method of the embodiment groups the disordered detection data according to the environmental characteristics, accurately locates the performance change in a certain environmental interval (such as the change trend of the insulation resistance in the interval of 30-40°C, 70-80% RH), provides structured data support for subsequent correlation analysis of the environment and performance, and avoids low analysis efficiency or correlation misplacement caused by unordered data.

[0052] Secondly, based on the storage environment conditions, correlation analysis is carried out, including:

[0053] For each environmental parameter interval and index data set, the temperature fluctuation range, humidity stable duration and air pressure change trend in the environmental parameter interval are matched, the correlation between the temperature fluctuation range, humidity stable duration and air pressure change trend and the change rate of the core performance index in the corresponding index data set is analyzed, and the influence direction of the three factors of temperature fluctuation, humidity stable state and air pressure change on the change of each core performance index is determined.

[0054] Feasibly, the specific way of correlation analysis is: for each environmental parameter interval and index data set, the correlation between the temperature fluctuation range (such as ±2℃ vs ±5℃), humidity stable duration (such as continuous 5-day stable vs daily fluctuation), air pressure change trend (such as continuous decline vs fluctuation) and performance change rate is calculated through Pearson correlation coefficient (Pearson correlation coefficient), for example, the quantitative relationship of "the average increase of dielectric loss value stage change rate is 0.0002 per ±3℃ increase of temperature fluctuation" can be obtained, and the influence degree of environment on performance is determined.

[0055] Based on the above, the metalized polyethylene film high-voltage capacitor storage reliability analysis method of the embodiment quantifies the specific effect of environmental factors on performance (such as the greater the temperature fluctuation, the higher the dielectric loss value change rate; the shorter the humidity stable duration, the faster the insulation resistance decreases), so that the performance degradation analysis can not only find the degradation phenomenon, but also find the environmental inducement of degradation, and provide targeted basis for optimizing the storage scheme (such as adjusting the warehouse temperature and humidity control accuracy, increasing the air pressure compensation device).

[0056] In the embodiment, the change rate of each core performance index is calculated, including:

[0057] Taking the index data at the starting time of each storage stage as the reference value, the change proportion of the index data at each detection time in the stage relative to the reference value is calculated respectively to obtain the stage change rate;

[0058] Taking the index data at the initial storage time as the total reference value, the change proportion of the index data at each detection time relative to the total reference value is calculated to obtain the cumulative change rate.

[0059] Feasibly, the specific way of change rate calculation is:

[0060] Stage change rate = (index data at a certain time - starting data of this stage) / starting data of this stage x 100%

[0061] Cumulative change rate = (index data at a certain time - initial storage data) / initial storage data x 100%

[0062] For example, the initial capacitance value is 1000 pF, the capacitance value at a certain time in the second stage is 1030 pF, and the starting data in the second stage is 1010 pF. The stage change rate is 1.98%, and the cumulative change rate is 3.00%. The performance change range of different stages can be quantified.

[0063] Based on the above, the metalized polyethylene film high-voltage capacitor storage reliability analysis method of the embodiment can capture the short-term performance change in a certain environmental stage (such as the rapid rise of dielectric loss value in a certain high-temperature stage), and the cumulative change rate can reflect the long-term performance degradation in the entire storage period (such as the total decline range of insulation resistance after 2 years of storage). It provides accurate and multi-dimensional quantitative data support for subsequent performance change feature extraction and degradation judgment, avoiding the one-sidedness of single change rate.

[0064] Further, the change characteristics of each core performance index with storage time are obtained, including:

[0065] By comparing the stage change rates of different storage stages, the change trend of each core performance index (such as the continuous decline of insulation resistance and the continuous rise of dielectric loss value) is determined. The duration of the change trend and the change range of the corresponding stage are counted. The time when the stage change rate exceeds the preset difference threshold (such as the preset difference threshold being twice the change rate of the previous stage) is marked, and the change characteristics corresponding to each core performance index are integrated.

[0066] Based on the above, the metalized polyethylene film high-voltage capacitor storage reliability analysis method of the embodiment converts the change rate data into perceptible and comparable performance characteristics (such as the continuous decline trend of insulation resistance, the stage change range of dielectric loss value, and the mutation node of partial discharge quantity), so that the performance change characteristics change from vague description to specific quantifiable information. Clear and unified input is provided for the formation of subsequent performance degradation rules, ensuring consistent understanding of performance changes by different testers.

[0067] Secondly, the performance degradation rule is used to determine whether the capacitor performance has degraded, including:

[0068] If the cumulative change rate of any core performance index in the performance degradation rule reaches the preset degradation judgment threshold, or the stage change rate of at least two core performance indexes exceeds the change rate of the initial storage stage (i.e. the first divided storage stage) for continuous multiple storage stages, it is determined that the capacitor performance has degraded.

[0069] It is feasible that the degradation judgment specifically includes: preset degradation judgment threshold values (such as a cumulative change rate of a capacitance value ±10%, a cumulative change rate of a dielectric loss value 50%, a cumulative change rate of an insulation resistance -30%, and a cumulative change rate of a partial discharge amount 100%), if any index reaches the threshold value, or the stage change rate of at least two indexes (such as the dielectric loss value and the partial discharge amount) continuously exceeds the divided first stage change rate for two stages, it is determined that the performance is degraded.

[0070] Based on the above, the metalized polyethylene film high-voltage capacitor storage reliability analysis method of the embodiment can identify long-term slow degradation (such as a cumulative decrease of 30% in insulation resistance after 2 years of storage) by using cumulative threshold standards, and can identify short-term accelerated degradation (such as a change rate of dielectric loss value and partial discharge amount exceeding the initial stage for two stages in succession) by using multiple indexes continuously exceeding the initial stage standard. The double standards take into account different degradation modes, ensure the accuracy and comprehensiveness of the degradation judgment, and avoid excessive replacement costs due to misjudgment or hidden safety hazards due to missed judgment.

[0071] In the embodiment, the core performance indicators of the capacitor are detected periodically, including:

[0072] In each preset time period, the detection of the core performance indicators is performed once at the starting time, the middle time, and the ending time. Before each detection, the capacitor is first placed in a detection environment and left until the temperature is consistent with the detection environment, and then a detection device suitable for the characteristics of each index is used to collect data. Each core performance indicator is collected multiple times, and the average of the multiple collection results is taken as the core performance indicator data at the time.

[0073] It is feasible that the detection frequency and data processing process includes: detecting once at the starting time, the middle time (such as the 15th day of the period), and the ending time of each preset period, and placing the capacitor in a detection environment (25°C±2°C, 50%RH±5%) for 2 hours before each detection to ensure that the temperature is consistent with the environment. Each index is collected continuously for 3 times, and the arithmetic mean is taken as the core performance indicator data at the time, which reduces the influence of random errors and improves the data reliability.

[0074] Based on the above, the metalized polyethylene film high-voltage capacitor storage reliability analysis method of the embodiment can cover the stable and fluctuating periods of the environment by using three-node detection, avoid the randomness of single-time-point detection, eliminate the misjudgment of dielectric loss value and insulation resistance caused by direct detection after low / high temperature storage by using temperature control during standing, control the random error to ≤0.5% by taking the average of multiple collections, ensure the accuracy and reliability of the detection data, provide a high-quality data source for subsequent data processing and degradation analysis, and avoid distortion of the analysis conclusion caused by inaccurate data.

[0075] Further, the detection of the capacitance value is based on the AC capacitance bridge method (prior art, such as the Xilin bridge derivative structure), and the stable capacitance value is obtained by adjusting the bridge balance.

[0076] The detection of the dielectric loss value is based on the phase difference comparison method (prior art, in line with the IEC60384 standard), and the influence of external electromagnetic interference on the measurement result is reduced through the shielding structure.

[0077] The detection of the insulation resistance is based on the high resistance meter constant voltage method (prior art, such as the GB / T1410 standard method), a constant DC voltage is applied and the value is recorded after the reading is stable.

[0078] The detection of the partial discharge quantity is based on the pulse current method (prior art, IEC60270 standard method), and the detection sensitivity is improved through signal amplification and filtering.

[0079] It should be noted that:

[0080] Capacitance value: represents the ability of the capacitor to store charge, the normal range is usually ±5% of the nominal value, the detection uses the AC capacitance bridge method (such as the Xilin bridge structure, test frequency 1kHz), the lead parasitic capacitance interference is eliminated by adjusting the bridge balance to ensure the measurement error ≤0.1%, which meets the precision requirements of IEC and GB series standards for high-voltage film capacitor capacitance detection;

[0081] Dielectric loss value (dielectric loss factor): reflects the degree of energy loss of the medium, usually ≤0.001 in high-voltage scenarios, uses the phase difference comparison method (in line with the IEC60384 standard), reduces external electromagnetic interference through shielding shell and grounding treatment, measurement accuracy reaches 0.0001, avoids detection deviation caused by interference;

[0082] Insulation resistance: represents the insulation ability of the medium, high-voltage capacitors usually require ≥10 10 Ω, uses the high resistance meter constant voltage method (according to GB / T1410 standard, applies 1000V DC voltage), records after 1 minute of standing to stabilize the reading, eliminates the influence of medium polarization effect on resistance value;

[0083] Partial discharge quantity: reflects the early characteristics of internal defects, the qualified standard is usually ≤10pC, uses the pulse current method (in line with the IEC60270 standard), captures weak discharge pulses through a 50dB gain signal amplifier and a 1MHz low-pass filter, and realizes early defect identification.

[0084] Based on the above, the metalized polyethylene film high-voltage capacitor storage reliability analysis method of the embodiment eliminates the interference of parasitic capacitance by the alternating current capacitance bridge method, ensures the measurement accuracy of the capacitance value, reduces electromagnetic interference by shielding through the phase difference comparison method, ensures the accuracy of the dielectric loss value, eliminates the dielectric polarization effect by the high resistance meter constant voltage method, and ensures the stability of the insulation resistance, and captures weak discharge pulses through signal amplification and filtering by the pulse current method, thereby improving the industry consistency of the detection data and providing a basis for the comparison of analysis results across scenes and laboratories

[0085] In the embodiment, the reliable storage duration under the set storage environment is determined, including:

[0086] Based on the performance degradation law, a fitting relationship of the core performance indicators changing with the storage time is constructed, and a preset failure judgment standard of the capacitor performance is set.

[0087] In the fitting relationship, the storage time corresponding to when each core performance indicator reaches the failure judgment standard is found, and the shortest time among them is taken as the reliable storage duration under the set storage environment.

[0088] Feasibly, the least square method is used to construct the fitting relationship of the core performance indicators changing with the storage time, for example, the capacitance value change rate and the time present a linear relationship: ΔC(t)=k×T+b, ΔC(t) is the change proportion of the capacitance value at t time relative to the initial storage time (t=0), the calculation formula is: ΔC(t)=(C(t)-C0) / C0×100%; wherein C(t) is the measured capacitance value at t time; C0 is the capacitance value at the initial storage time (without experiencing storage) (i.e. the nominal value or initial detection value of the capacitor out of the factory); T is the storage time, that is, the cumulative duration of the capacitor from the beginning of storage to detection / evaluation, k is the linear fitting slope, that is, the average change rate of the relative change rate of the capacitance value, if k>0: represents that the capacitance value changes positively with the storage time (such as the capacitance value rises due to the slight shrinkage of the film medium); if k<0: represents that the capacitance value changes negatively with the storage time (such as the capacitance value decreases due to the corrosion of the electrode metal layer); the greater the absolute value of k, the faster the capacitance value changes with time, and the poorer the performance stability; b is the linear fitting intercept, that is, the relative change rate of the capacitance value at the initial storage time. The dielectric loss value change rate and the time present an exponential relationship: Δtanδ(t)=a×e gt, Delta tan delta (t) is the relative change rate of the dielectric loss value (dielectric loss factor) at time t, i.e. the change proportion of the dielectric loss value at time t relative to the initial storage time, Delta tan delta (t) = (tan delta (t) - tan delta 0) / tan delta 0 * 100%; wherein tan delta (t) is the measured dielectric loss value at time t, and tan delta 0 is the dielectric loss value at the initial storage time; a is the exponential fitting initial coefficient, i.e. the relative change rate of the dielectric loss value at the initial storage time; g is the exponential growth coefficient, i.e. the acceleration growth coefficient of the relative change rate of the dielectric loss value, because the metalized polyethylene film will accelerate the dielectric aging under the action of temperature and humidity (the greater the humidity and the higher the temperature, the faster the aging), therefore g is always positive, representing an accelerated upward trend of the dielectric loss value with the storage time (in line with the physical law of material aging); the value of g is directly related to the storage environment: the value of g is larger in a high-temperature and high-humidity environment (for example, g is about 0.3 per year at 40 DEG C and 80% RH), and the value of g is smaller in a normal temperature and humidity environment (for example, g is about 0.1 per year at 25 DEG C and 50% RH).

[0089] According to the fitting relationship, the fitting model is ensured to fit the actual trend of performance degradation. The preset failure criteria of capacitor performance (such as the deviation of the capacitance value from the nominal value of ±15%, the dielectric loss value exceeding 0.002, the insulation resistance being lower than 10 9 Ω, and the partial discharge amount exceeding 50 pC) are set, the corresponding time when each index reaches the failure criteria (such as 5 years for the capacitance value, 4 years for the dielectric loss value, 6 years for the insulation resistance, and 5.5 years for the partial discharge amount) is found in the fitting relationship, and the shortest time (4 years) is taken as the reliable storage time in the set storage environment, thereby providing a quantitative basis for the replacement of spare devices and the planning of storage cycles.

[0090] Based on the above, the metalized polyethylene film high-voltage capacitor storage reliability analysis method of the embodiment converts the performance degradation law into a predictable mathematical model, avoids the limitations of inferences based on existing data, clearly defines the performance failure boundary through the failure criteria, takes the shortest time to ensure that the time length is determined by the most stringent index (such as 5 years for the capacitance value and 4 years for the dielectric loss value, with 4 years as the reliable time length), meets the demand for high reliability of capacitors in key fields, provides clear quantitative basis for the planning of spare device replacement cycles and the setting of warehouse storage cycles, and ensures that the use performance of the devices after storage meets the standards.

[0091] In the embodiments provided by the present application, it should be understood that the embodiments described herein can be realized by hardware, software, firmware, middleware, codes or any proper combination thereof. For hardware implementation, the processor can be realized in one or more of the following components: an application specific integrated circuit (ASIC), a digital signal processor (DSP), a digital signal processing device (DSPD), a programmable logic device (PLD), a field programmable gate array (FPGA), a processor, a controller, a microcontroller, a microprocessor, other electronic units designed to perform the functions described herein, or a combination thereof. For software implementation, the procedures described herein can be implemented with a computer program that is written in any suitable programming language. The program can be stored in a computer readable storage medium or transmitted as one or more instructions or codes on the computer readable storage medium. The computer readable storage medium includes any storage medium that can be accessed by a computer. The computer readable storage medium can include but is not limited to the following media: a RAM, a ROM, an EEPROM, a CD-ROM or other optical disc storage, a magnetic disk storage medium or other magnetic storage device, or any other medium that can be used to carry or store desired program codes in the form of instructions or data structures and can be accessed by a computer.

[0092] Finally, it should be noted that the above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, modifications or equivalent replacements of some technical features described in the foregoing embodiments can be made by those skilled in the art, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for storage reliability analysis of metallized polyethylene film high-voltage capacitors, characterized in that, include: Step 1: Simulate the storage conditions of metallized polyethylene film high voltage capacitors under different storage environment conditions, wherein the storage environment conditions include at least temperature, humidity and air pressure changes; Step 2: During storage, the core performance indicators of the capacitor are tested periodically. The core performance indicators include at least capacitance, dielectric loss, insulation resistance and partial discharge. Step 3: Process the core performance index data obtained from the test. Classify and organize the index data of different storage stages, draw the change curve of each core performance index with storage time, calculate the change rate of each core performance index, and conduct correlation analysis based on storage environment conditions to obtain the change characteristics of each core performance index with storage time. Based on the change characteristics, form the performance degradation law, and then use the performance degradation law to determine whether the capacitor performance has degraded. Step 4: Based on storage environment conditions and performance degradation patterns, evaluate the storage reliability of the capacitor and determine its reliable storage duration under the specified storage environment.

2. The method for storage reliability analysis of metallized polyethylene film high-voltage capacitors according to claim 1, characterized in that, The storage conditions of the simulated metallized polyethylene film high-voltage capacitor under different storage environments include: According to a preset time cycle, different combinations of temperature, humidity and air pressure are alternately switched to form a dynamically changing storage environment, and the environmental conditions are maintained until the beginning of the next preset time cycle after each environmental switch.

3. The method for storage reliability analysis of metallized polyethylene film high-voltage capacitors according to claim 1 or 2, characterized in that, The aforementioned classification and organization of indicator data for different storage stages includes: Storage stages are divided according to the gradient of changes in storage environment conditions. Storage processes within the same environmental parameter range are defined as the same stage, and the core performance index data of all detection times within that stage are organized accordingly to form a correspondence between environmental parameter ranges and index data groups.

4. The method for storage reliability analysis of metallized polyethylene film high-voltage capacitors according to claim 3, characterized in that, The correlation analysis based on storage environment conditions includes: For each environmental parameter range and index data group, the temperature fluctuation range, humidity stability duration, and air pressure change trend within that environmental parameter range are matched. The correlation between the temperature fluctuation range, humidity stability duration, and air pressure change trend and the change rate of the core performance index in the corresponding index data group is analyzed. The influence direction of the three types of factors—temperature fluctuation, humidity stability, and air pressure change—on the changes of each core performance index is clarified.

5. The method for storage reliability analysis of metallized polyethylene film high-voltage capacitors according to claim 1, characterized in that, The calculation of the rate of change of each core performance indicator includes: Using the index data at the beginning of each storage stage as the baseline value, the change ratio of the index data at each detection time within that stage relative to the baseline value is calculated to obtain the stage change rate. Using the index data at the initial storage time as the total baseline value, the change ratio of the index data at each detection time relative to the total baseline value is calculated to obtain the cumulative change rate.

6. The method for storage reliability analysis of metallized polyethylene film high-voltage capacitors according to claim 5, characterized in that, The obtained characteristics of the changes in each core performance index over storage time include: By comparing the rate of change at different storage stages, the changing trends of each core performance indicator are determined; the duration of continuous storage of the changing trends and the magnitude of change at the corresponding stages are statistically analyzed; the moment when the rate of change at a stage exceeds a preset difference threshold compared to the previous stage is marked, and the changes are integrated to form the change characteristics corresponding to each core performance indicator.

7. The method for storage reliability analysis of metallized polyethylene film high-voltage capacitors according to claim 6, characterized in that, The method of determining whether capacitor performance has degraded based on performance degradation patterns includes: If the cumulative change rate of any core performance indicator in the performance degradation pattern reaches the preset deterioration judgment threshold, or if the stage change rate of at least two core performance indicators exceeds the change rate of the initial storage stage for multiple consecutive storage stages, the capacitor performance is judged to have degraded.

8. The method for storage reliability analysis of metallized polyethylene film high-voltage capacitors according to claim 1, characterized in that, The core performance indicators of the capacitors to be periodically tested include: Within each preset time period, core performance indicators are tested once at the start, middle, and end times. Before each test, the capacitor is placed in the testing environment and allowed to stand until the temperature matches the testing environment. Then, data is collected using testing equipment adapted to the characteristics of each indicator. Each core performance indicator is collected multiple times, and the average of the multiple collection results is taken as the core performance indicator data at that moment.

9. The method for storage reliability analysis of metallized polyethylene film high-voltage capacitors according to claim 8, characterized in that, The capacitance value is detected based on the AC capacitance bridge method, and a stable capacitance value is obtained by adjusting the bridge circuit balance. The detection of dielectric loss value is based on the phase difference comparison method, and the shielding structure reduces the influence of external electromagnetic interference on the measurement results. The insulation resistance is detected based on the constant voltage method of a high resistance meter, by applying a constant DC voltage and maintaining it until the reading stabilizes before recording the value. The detection of partial discharge is based on the pulse current method, and the detection sensitivity is improved by signal amplification and filtering.

10. The method for storage reliability analysis of metallized polyethylene film high-voltage capacitors according to claim 1, characterized in that, Determining its reliable storage duration under a specified storage environment includes: Based on the performance degradation law, a fitting relationship between the core performance indicators and storage time is constructed, and a preset failure judgment standard for capacitor performance is set. Find the storage time corresponding to each core performance index reaching the failure judgment criteria in the fitted relationship, and take the shortest time as the reliable storage time under the set storage environment.

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