Transformer insulation paper aging state evaluation method, device and equipment

Abstract

The application provides a transformer insulation paper aging state evaluation method, device and equipment, and relates to the technical field of transformers. The method comprises the following steps: obtaining time sequence operation data of a transformer to be evaluated; wherein the time sequence operation data comprises the temperature of insulation paper in each time period, the water content in insulation oil and the time length of the time period; for each time period, the initial moisture content of the insulation paper in the current time period is calculated according to the starting degree of polymerization, the water content in the oil, the temperature of the current time period and the pre-constructed oil-paper water balance relationship; the instantaneous aging rate of the current time period is calculated according to the initial moisture content and the temperature; the terminal degree of polymerization of the current time period is calculated as the starting degree of polymerization of the next time period by means of an improved second-order aging model according to the instantaneous aging rate, the time length of the time period and the starting degree of polymerization of the current time period; after iteration of all time periods, the aging state evaluation of the insulation paper is completed according to the finally obtained terminal degree of polymerization. The application can improve the accuracy of the aging state evaluation of the insulation paper.

Description

Technical Field

[0001] This invention relates to the field of transformer technology, and in particular to a method, apparatus and equipment for assessing the aging status of transformer insulation paper. Background Technology

[0002] Power transformers are critical equipment in power transmission and distribution systems, and the health of their internal insulating oil and insulating paper directly affects the stable operation of the power grid and the service life of the equipment. Under the combined effects of temperature and moisture, the insulating paper undergoes irreversible cellulose chain breakage aging, resulting in a continuous decrease in the degree of polymerization. Accurately determining the degree of aging of the insulating paper is an important support for transformer condition-based maintenance and remaining life estimation.

[0003] Due to limitations in equipment structure, the moisture content of insulating paper cannot be directly detected. The conventional method is to sample and test the moisture content of the insulating oil, calculate the moisture content of the insulating paper based on the oil-paper moisture balance relationship, and then calculate the aging rate by combining temperature. The degree of polymerization is then deduced through a second-order aging kinetic model to characterize the aging state of the insulating paper.

[0004] Current assessment methods use a fixed moisture content in the insulating paper throughout the calculation process. However, in actual operation, transformer operating conditions fluctuate continuously, and aging reactions generate or consume moisture, causing the moisture content of the insulating paper to change dynamically over time. Moisture is a key parameter affecting the insulation aging rate. If the moisture content is assumed to be constant, there will be a significant deviation between the moisture content of the insulating paper used in the calculation and the actual moisture content inside the equipment, resulting in distorted polymerization degree calculations and a substantial reduction in the accuracy of the insulation paper aging status assessment. Summary of the Invention

[0005] This invention provides a method, apparatus, and equipment for assessing the aging status of transformer insulation paper, thereby solving the problem that existing methods for assessing the aging status of transformer insulation paper use a fixed moisture content, leading to inaccurate assessments.

[0006] In a first aspect, embodiments of the present invention provide a method for assessing the aging state of transformer insulation paper, comprising: acquiring time-series operating data of the transformer to be assessed; wherein the time-series operating data includes the temperature of the insulation paper, the moisture content in the insulating oil, and the duration of each time period; for each time period, calculating the initial moisture content of the insulation paper for the current time period based on the initial degree of polymerization, the moisture content in the oil, the temperature, and a pre-constructed oil-paper moisture balance relationship; wherein the oil-paper moisture balance relationship is constructed based on a correction coefficient that linearly changes with the degree of polymerization; calculating the instantaneous aging rate for the current time period based on the initial moisture content and temperature; calculating the final degree of polymerization for the current time period based on the instantaneous aging rate, the duration of the time period, and the initial degree of polymerization for the current time period, using an improved second-order aging model, as the initial degree of polymerization for the next time period; and after iterating through all time periods, completing the assessment of the aging state of the insulation paper based on the final obtained final degree of polymerization.

[0007] In one possible implementation, the initial moisture content of the insulating paper for the current period is calculated based on the initial degree of polymerization, moisture content in the oil, temperature, and a pre-established oil-paper moisture balance relationship. This includes: calculating a correction coefficient based on the initial degree of polymerization and a first preset function for the current period; and calculating the initial moisture content of the insulating paper for the current period based on the moisture content in the oil, temperature, correction coefficient, and oil-paper moisture balance relationship.

[0008] In one possible implementation, before calculating the initial moisture content of the insulating paper at the current time period, the following steps are included: constructing a relative humidity relationship based on the partial pressure of water vapor in the air and the saturated vapor pressure; constructing a relative moisture saturation relationship in the oil based on the water content in the oil and the saturated water content in the oil; constructing a relationship between the moisture content in the paper and the water vapor pressure based on the correction coefficient, the partial pressure of water vapor in the air, and the temperature; and constructing an oil-paper moisture balance relationship based on the equivalent assumption of the relative moisture saturation in the oil and the relative humidity of the air, combined with the relative humidity relationship, the relative moisture saturation relationship in the oil, and the relationship between the moisture content in the paper and the water vapor pressure.

[0009] In one possible implementation, before constructing the relationship between air relative humidity based on the partial pressure of water vapor in the air and the saturated vapor pressure, the method further includes: calculating the saturated vapor pressure corresponding to the current temperature based on the temperature and the Antoni equation; and before constructing the relationship between the relative saturation of water in the oil based on the water content in the oil and the saturated water content in the oil, the method further includes: calculating the saturated water content in the oil corresponding to the current temperature based on the temperature and a preset coefficient.

[0010] In one possible implementation, the final degree of polymerization for the current period is calculated using an improved second-order aging model based on the instantaneous aging rate, the duration of the time period, and the initial degree of polymerization for the current period. This includes: calculating the equivalent aging duration under the new conditions based on the instantaneous aging rate, the initial degree of polymerization for the current period, and the factory-issued degree of polymerization of the transformer insulation paper; and inputting the instantaneous aging rate, the equivalent aging duration, the duration of the time period, and the initial degree of polymerization for the current period into the improved second-order aging model to calculate the final degree of polymerization for the current period.

[0011] In one possible implementation, the construction process of the improved second-order aging model includes: establishing a second-order aging kinetic equation describing the decay of the degree of polymerization of the insulating paper; using the instantaneous aging rate, equivalent aging duration, time period duration, and the initial degree of polymerization of the current time period as model input parameters to improve the second-order aging kinetic equation; wherein, the equivalent aging duration is calculated by the instantaneous aging rate, the degree of polymerization at the factory, and the initial degree of polymerization of the current time period; the instantaneous aging rate is defined as a variable that dynamically changes with the temperature and moisture content of the insulating paper in each time period, and the degree of polymerization decays continuously and smoothly with the aging process, thus obtaining the improved second-order aging model.

[0012] In one possible implementation, after iterating through all time periods, the aging status assessment of the insulating paper is completed based on the final obtained end degree of polymerization. This includes: completing iterative calculations for all time periods, extracting the end degree of polymerization for the final time period as a real-time degree of polymerization characteristic value of the insulating paper; and completing the aging status assessment of the transformer insulating paper based on the real-time degree of polymerization characteristic value and a preset insulating paper aging threshold.

[0013] In one possible implementation, after iterating through all time periods and completing the aging status assessment of the insulating paper based on the final obtained degree of polymerization, the following steps are also included: setting the initial expected lifespan of the insulating paper; using the existing moisture content in the oil at the end of the aging assessment as the baseline moisture content; calculating the moisture growth rate of the insulating oil based on the transformer operating conditions; determining the future real-time oil moisture content within each time interval by combining the preset future operating temperature, the baseline moisture content, and the duration of each time interval; calculating the initial moisture content of the insulating paper for the corresponding time period based on the future real-time oil moisture content through the oil-paper moisture balance relationship; calculating the instantaneous aging rate from the initial moisture content and the preset future operating temperature; solving for the degree of polymerization decay in each time interval using the improved second-order aging model; iteratively obtaining the remaining degree of polymerization of the insulating paper under the current expected lifespan; determining whether the remaining degree of polymerization reaches the preset termination calculation condition; wherein, if the termination calculation condition is not met, adjusting the initial expected lifespan and repeating the steps for determining the future real-time oil moisture content and subsequent steps; when the termination calculation condition is met, recording the final expected lifespan and the corresponding remaining degree of polymerization to determine the remaining service life of the insulating paper.

[0014] Secondly, embodiments of the present invention provide a transformer insulation paper aging status assessment device, comprising: a communication module for acquiring time-series operation data of the transformer to be assessed; wherein the time-series operation data includes the temperature of the insulation paper, the moisture content in the insulating oil, and the duration of each time period; a processing module for calculating the initial moisture content of the insulation paper for each time period based on the initial degree of polymerization, the moisture content in the oil, the temperature, and a pre-constructed oil-paper moisture balance relationship; wherein the oil-paper moisture balance relationship is constructed based on a correction coefficient that linearly changes with the degree of polymerization; calculating the instantaneous aging rate for the current time period based on the initial moisture content and temperature; calculating the final degree of polymerization for the current time period based on the instantaneous aging rate, the duration of the time period, and the initial degree of polymerization for the current time period using an improved second-order aging model, which is used as the initial degree of polymerization for the next time period; and completing the insulation paper aging status assessment based on the final obtained final degree of polymerization after all time periods have been iterated.

[0015] Thirdly, embodiments of the present invention provide an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the method described in the first aspect or any possible implementation thereof.

[0016] This invention provides a method, apparatus, and equipment for assessing the aging state of transformer insulation paper. First, based on the initial degree of polymerization, oil moisture content, and temperature at each time period, the real-time initial moisture content of the insulation paper is calculated segment by segment. This adapts to the moisture distribution pattern of the oil-paper mixture as the insulation paper ages, thus accommodating the dynamic moisture content conditions of the transformer. Then, the instantaneous aging rate is calculated using the real-time initial moisture content and temperature in tandem, aligning with the aging mechanism where temperature and moisture synergistically accelerate cellulose chain breakage, thereby improving the accuracy of the instantaneous aging rate calculation. Second, based on a second-order aging model under varying operating conditions, the degree of polymerization is iteratively updated time-by-time, and the aging attenuation is continuously accumulated over all time periods. This adapts to the nonlinear aging characteristics of insulation paper, which are initially rapid and then slow down, realistically reproducing the long-term, variable-condition, sequential aging process of the transformer. Finally, the aging state of the insulation paper is quantitatively assessed based on the final end-stage polymerization quantity after all-time iterations, improving the accuracy of the transformer insulation paper aging state assessment results. Attached Figure Description

[0017] Figure 1 It is an aging kinetic model; Figure 2 This is a flowchart illustrating the implementation of the transformer insulation paper aging status assessment method provided in this embodiment of the invention. Figure 3 This is a schematic diagram of the moisture balance test results of oil paper provided in an embodiment of the present invention; Figure 4 This is a schematic diagram illustrating the relationship between the correction coefficient and the degree of polymerization provided in an embodiment of the present invention; Figure 5(a) is a schematic diagram of the change of DP over time provided in the embodiment of the present invention; Figure 5(b) shows the 1 / DP provided in the embodiment of the present invention. t Schematic diagram of -1 / DP0 changing over time; Figure 6 The ln provided in the embodiments of the present invention k 10 ln k 2 and 1 / T Relationship diagram; Figure 7 This is a schematic diagram illustrating the relationship between frequency coefficient and moisture content provided in an embodiment of the present invention; Figure 8 This is a flowchart of insulation aging calculation provided in an embodiment of the present invention; Figure 9 This is a schematic diagram of the aging rate transition method when aging conditions change, provided in an embodiment of the present invention. Figure 10 This is a schematic diagram of temperature time-series data provided in an embodiment of the present invention; Figure 11 This is a flowchart of the insulation paper life prediction method provided in an embodiment of the present invention; Figure 12This is a schematic diagram of the structure of the transformer insulation paper aging status assessment device provided in an embodiment of the present invention; Figure 13 This is a schematic diagram of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0018] Power transmission and transformation equipment bears the heavy responsibility of power transmission and transformation. Ensuring its safe and reliable operation is a crucial condition for maintaining the stable operation of the power grid. Timely monitoring of the current operating status of power transmission and transformation equipment, early detection of potential faults, and advance prediction of future operating trends are all essential for its safe and stable operation. As a vital piece of equipment in the power system's transmission and transformation chain, the safe and stable operation of power transformers directly impacts the reliability of the entire power supply service.

[0019] The expected service life of a transformer at the time of manufacture is generally 30 to 40 years. However, due to various factors in the field operating environment, the service life of a transformer often falls short of the preset limit. Guidelines and reports issued by CIGRET, IEC, and State Grid indicate that the vast majority of transformer failures are related to insulation. Studies have shown that the insulation performance of aged insulating oil can be improved or restored through oil filtration / replacement. However, since the insulating paper cannot be replaced, the loss of mechanical strength caused by its aging is irreversible. Therefore, both domestically and internationally, it is generally agreed that the state of solid insulation is the key factor determining the overall performance and service life of the transformer's oil-paper insulation. Thus, timely monitoring of the aging state of the insulating paper is essential.

[0020] The main component of paper insulation is cellulose, which accounts for approximately 90% of ordinary kraft paper. Cellulose is a glucose polymer, and the degree of polymerization (DP) is commonly used as an indicator of polymer molecule size, based on the number of repeating units, i.e., the average number of repeating units contained in the polymer macromolecular chain. The density of the physical structure of cellulose and its mechanical and electrical properties are positively correlated with the DP value; moreover, DP decreases as the insulation ages. Therefore, the degree of polymerization of cellulose is usually used to reflect the aging degree of the insulating paper. As aging progresses, the average degree of polymerization of cellulose insulating paper gradually decreases from 1000-1200 in the unaged state, and the mechanical strength also gradually deteriorates. When the degree of polymerization of the insulating paper at any point on a transformer drops to approximately 200, its mechanical strength has fallen below 50%, meaning that the insulating paper is nearing its lifespan limit, and the transformer has also reached the end of its service life.

[0021] The decrease in the degree of polymerization is a macroscopic manifestation of the aging and degradation reaction of cellulose insulating paper. The cellulose aging kinetic model is a theoretical calculation method for the degree of polymerization based on regular analysis, which is mainly affected by aging time, temperature, and moisture. Therefore, the aging kinetic model can be used to describe the process of the decrease in the degree of polymerization of insulating paper, thereby realizing the quantitative analysis and evaluation of the insulation aging state.

[0022] Existing research has shown that the aging rate is affected by temperature and the moisture content of the insulating paper. In addition, it is not easy to measure the moisture content of the insulating paper in either the aging experiment in the insulation box or in the actual aging process of transformer oil-paper insulation, while the moisture content of the oil is easier to obtain. Furthermore, since there is an equilibrium relationship between the moisture content of the insulating oil and the insulating paper under steady conditions, the moisture content of the oil can be measured first, and then the moisture content of the paper can be calculated through the equilibrium relationship.

[0023] Aging kinetic models, as a theoretical method for calculating dynamic aging (DP), are commonly used to assess the aging state of transformer insulation paper. Commonly used aging kinetic models include... Figure 1 As shown, the second-order model better reflects the change in aging rate over time. Typically, the above model is only used to fit DP measurement data under isothermal experimental conditions with different initial moisture contents, and the relevant parameters in the model are considered as average values ​​throughout the aging process, without considering the rate changes caused by moisture variations due to the reaction.

[0024] However, due to the changes in the moisture content of the insulating paper caused by the generation or consumption of water during the actual aging process, and the fact that the transformer operating temperature is not constant, the instantaneous values ​​of parameters related to the aging rate will be constantly changing. Therefore, it is necessary to consider improving the aging kinetic model so that it can perform DP calculations under varying temperatures and moisture levels, thereby achieving the assessment of the aging status of the insulating paper under varying aging conditions.

[0025] To address the shortcomings of existing technologies in accurately assessing the aging of insulating paper under varying temperature and moisture conditions, this invention proposes an improved second-order aging kinetic model for evaluating the aging state of transformer insulating paper. By constructing a dynamic oil-paper moisture balance relationship that adapts to the degree of aging, updating the instantaneous aging rate time-by-time, and iteratively solving for the aggregation degree in segments, this method achieves accurate quantitative assessment of the aging state of insulating paper under complex varying operating conditions.

[0026] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0027] See Figure 2 The document illustrates a flowchart of the transformer insulation paper aging status assessment method provided in this embodiment of the invention, detailed below: Step S201: Obtain the time-series operation data of the transformer to be evaluated; wherein, the time-series operation data includes the temperature of the insulating paper, the moisture content in the insulating oil, and the duration of each time period.

[0028] In some embodiments, time-series operational data refers to long-term transformer operation monitoring data collected in time segments, reflecting the dynamic changes in load, temperature, and moisture over time. The temperature of the insulating paper is the hot spot temperature of the transformer winding insulating paper itself, the core temperature driving moisture migration and cellulose chain breakage aging, distinct from the top oil temperature and ambient temperature. The insulating oil is the mineral insulating oil impregnated with the insulating paper inside the transformer; moisture content can be sampled and tested on-site. Moisture in the oil is the dissolved water content within the insulating oil; it can be sampled and tested non-destructively on-site and is the only directly measurable moisture parameter. The time period duration is the continuous operating time of a single period, used to accumulate aging damage.

[0029] In this embodiment, continuous operating time-series data is collected in different time periods to fully reconstruct the dynamic changes in temperature and water caused by transformer load fluctuations.

[0030] Step S202: For each time period, calculate the initial moisture content of the insulating paper for the current time period based on the initial degree of polymerization, moisture content in the oil, temperature, and the pre-constructed oil-paper moisture balance relationship; wherein, the oil-paper moisture balance relationship is constructed based on a correction coefficient that changes linearly with the degree of polymerization.

[0031] In some embodiments, the initial degree of polymerization is the average degree of polymerization of cellulose in the insulating paper at the beginning of the time period, characterizing the initial aging degree of that time period; the degree of polymerization of new insulating paper is approximately 1000~1200, and continues to decrease after aging. The oil-paper moisture balance relationship is based on the Oommen oil-paper moisture balance theory, which is the mathematical relationship between oil and paper moisture reaching adsorption / desorption steady state at the same temperature; conventional models do not have an aging correction coefficient. The initial moisture content is the mass fraction of internal moisture in the insulating paper at the beginning of the current time period; moisture significantly accelerates cellulose hydrolysis and chain breakage aging. The degree of polymerization is the average number of glucose monomers in the cellulose molecular chain, a core quantitative indicator of insulating paper aging; the lower the degree of polymerization, the more severe the aging.

[0032] In this embodiment, a correction coefficient that changes linearly with the degree of polymerization is introduced to dynamically correct the balance relationship, which conforms to the real physical law of moisture migration in the oil paper during the aging process. The internal moisture content of the insulating paper that cannot be directly sampled and detected can be accurately calculated by relying solely on the moisture content in the oil that can be measured on-site, which greatly reduces the distortion of moisture calculation and solves the core underlying defects of the existing technology.

[0033] Step S203: Calculate the instantaneous aging rate for the current period based on the initial moisture content and temperature.

[0034] In some embodiments, the instantaneous aging rate is the rate at which the cellulose molecular chains break down in real time under a fixed temperature and water condition; the underlying layer is obtained by coupling a second-order model and is dynamically updated time-by-time.

[0035] In this embodiment, the instantaneous aging rate is solved segment by segment by synchronously coupling the real-time paper moisture content and the hot spot temperature of the insulating paper, which is consistent with the two-factor aging mechanism of cellulose chain breakage. The reaction speed is updated independently for each operating condition, which significantly improves the calculation accuracy of aging damage in a single time period.

[0036] Step S204: Based on the instantaneous aging rate, time period duration, and the initial aggregation degree of the current time period, the final aggregation degree of the current time period is calculated using the improved second-order aging model, and used as the initial aggregation degree of the next time period.

[0037] In some embodiments, the improved second-order aging model is a modified mathematical model based on the traditional second-order degradation kinetic equation of cellulose, with the addition of an equivalent duration and dynamic constraints on only the instantaneous rate. The degree of polymerization at the end of the current period is used as the initial value for calculating the next period, thus realizing the continuous accumulation of aging damage.

[0038] In this embodiment, only the instantaneous aging rate changes dynamically with temperature and water, and the degree of polymerization is continuous, smooth and without abrupt changes. It is combined with the equivalent aging time to adapt to the differences in working conditions. The degree of polymerization at the end is calculated for each time period and used as the input for the next period. The aging damage of the whole cycle is continuously accumulated, and the nonlinear aging characteristics of the insulating paper, which are rapid aging in the early stage and slow decay in the later stage, are accurately reproduced.

[0039] Step S205: After all time periods have been iterated, the aging status of the insulating paper is evaluated based on the final obtained degree of polymerization.

[0040] In some embodiments, the full-time iteration involves traversing all historical operating periods of the transformer to complete the segmented aggregation degree calculation. The final aggregation degree obtained is the final aggregation degree value after the cumulative aging of the entire cycle, serving as the sole quantitative indicator for aging determination. The aging status of the insulation paper is classified into insulation integrity, mild aging, moderate aging, and severe failure levels based on the aggregation degree. Aging status assessment quantitatively determines the remaining carrying capacity of the insulation, supporting condition-based maintenance of the transformer.

[0041] In this embodiment, the degree of polymerization after continuous iteration and convergence throughout the entire time series is used as a quantitative criterion to avoid the problem of the accumulation and amplification of multi-segment calculation errors. The degree of polymerization directly reflects the degree of intact breakage of cellulose molecules and can be matched with the industry standard aging threshold to achieve graded quantitative assessment. The assessment results are objective and quantitative, providing a reliable numerical basis for transformer maintenance cycle and risk management.

[0042] This invention provides a method for assessing the aging state of transformer insulation paper. First, based on the initial degree of polymerization, oil moisture content, and temperature at each time period, the real-time initial moisture content of the insulation paper is calculated segment by segment. This method adapts to the moisture distribution pattern of the oil-paper mixture as the insulation paper ages, thus accommodating the dynamic moisture content conditions of the transformer. Then, the instantaneous aging rate is calculated using the real-time initial moisture content and temperature in tandem, aligning with the aging mechanism where temperature and moisture synergistically accelerate cellulose chain breakage, thereby improving the accuracy of the instantaneous aging rate calculation. Second, based on a second-order aging model under varying operating conditions, the degree of polymerization is iteratively updated time-by-time, and the aging attenuation is continuously accumulated over all time periods. This adapts to the nonlinear aging characteristics of insulation paper, which are initially rapid and then slow down, realistically reproducing the long-term, variable-condition, sequential aging process of the transformer. Finally, the aging state of the insulation paper is quantitatively assessed based on the final end-stage polymerization quantification after all-time iterations, improving the accuracy of the transformer insulation paper aging state assessment results.

[0043] To further refine the precise calculation logic of the moisture content of insulating paper and improve the realization process of dynamic oil paper moisture balance, this invention constructs a dynamic correction model adapted to the aging state through multi-layer relational derivation.

[0044] In one possible implementation, the initial moisture content of the insulating paper for the current period is calculated based on the initial degree of polymerization, moisture content in the oil, temperature, and a pre-established moisture balance between the oil and paper, including: Calculate the correction coefficient based on the initial aggregation degree of the current time period and the first preset function; The initial moisture content of the insulating paper at the current time period is calculated based on the moisture content in the oil, temperature, correction factor, and moisture balance formula of the oil-paper mixture.

[0045] In some embodiments, the first preset function is a pre-calibrated linear function. By inputting the initial aggregation degree of the current time period, the correction coefficient under the corresponding aging degree can be output.

[0046] In this embodiment, by pre-setting a linear function to correlate the degree of polymerization and a correction coefficient, the moisture balance law of the oil-paper can be dynamically corrected according to the real-time aging degree of the insulation. This solves the shortcomings of traditional balance models that do not distinguish between new and old insulation and uniformly use a fixed moisture absorption curve. By combining the moisture content in the oil, the temperature of the insulating paper, and the correction coefficient into the balance relationship calculation, the weakening effect of aging on the paper's water absorption capacity is fully considered, significantly reducing the calculation deviation of the moisture content of the insulating paper. This overcomes the core pain point of existing methods that assume constant hygroscopic characteristics and distort moisture calculations. Moisture content is a key parameter for calculating the aging rate. By outputting a high-precision initial moisture content of the paper, the overall accuracy of subsequent instantaneous aging rate and degree of polymerization decay calculations is ensured, improving the accuracy of the entire evaluation method from the bottom up.

[0047] To clarify the construction principle and mathematical derivation process of the dynamic oil paper moisture balance relationship, and to support the effective embedding of correction coefficients and accurate moisture conversion, this invention completes the construction of a dynamic balance model by combining multiple fundamental relationships.

[0048] In one possible implementation, before calculating the initial moisture content of the insulating paper for the current time period, the following is also included: Based on the partial pressure of water vapor in the air and the saturated vapor pressure, a formula for the relationship between relative humidity of air is constructed. Based on the water content and saturated water content in the oil, a formula for the relative water saturation of the oil is constructed. Based on the correction factor, the partial pressure of water vapor in the air, and the temperature, a formula is constructed to describe the relationship between the moisture content and water vapor pressure in paper. Based on the equivalent assumption of relative saturation of water in oil and relative humidity of air, and combining the relationship between relative humidity of air, relative saturation of water in oil, and the relationship between water content in paper and water vapor pressure, the moisture balance relationship of oil and paper is constructed.

[0049] In some embodiments, the partial pressure of water vapor in the air is the pressure generated solely by water vapor in an equivalent simulated water vapor environment at the oil-paper interface. It is a physical quantity characterizing the water vapor content and is used to construct the humidity correlation equation. The saturated vapor pressure is the limiting partial pressure of water vapor at which water vapor reaches gas-liquid equilibrium under the current insulating paper temperature conditions. It is solved by the Antoni equation and is the benchmark value for calculating relative humidity. The relative humidity relationship is a mathematical formula using water vapor partial pressure and saturated vapor pressure as variables to characterize the humidity of the equivalent air environment. The water content in the oil is the dissolved water content inside the insulating oil, a measurable parameter that can be directly measured by on-site sampling. The saturated water content in the oil is the maximum limit of water that the insulating oil can dissolve at the current temperature; the higher the temperature, the stronger the saturated water-holding capacity of the oil. The relative saturation relationship of water in the oil is a formula constructed based on the actual water content in the oil and the saturated water content of the oil, characterizing the current water saturation level of the insulating oil. The correction coefficient is a correction parameter that changes linearly with the degree of polymerization of the insulating paper and is used to characterize the degree of decay of the hygroscopic performance of the insulating paper after aging. The relationship between the moisture content of paper and the water vapor pressure is established by introducing a correction factor to create a mathematical correlation between the partial pressure of water vapor and the moisture content adsorbed by the insulating paper at the same temperature, reflecting the influence of aging on the paper's water absorption capacity. The equivalent assumption of the relative saturation of water in oil and the relative humidity of air is a classic equivalent theory in the field of oil-paper moisture balance. At the same temperature, the water saturation of insulating oil is equivalent to the relative humidity of the equivalent air at the oil-paper interface, thus building a bridge for the conversion between oil and paper moisture.

[0050] In practice, aging causes changes in the cellulose structure of the insulating paper, thus altering its water absorption. Consequently, the moisture balance between the insulating paper and mineral oil changes with the degree of aging. DP (dihydropyridine) is used to measure the degree of aging. Experimental data on the moisture balance of insulating paper and mineral oil (i.e., insulating oil) with different DP values ​​at different temperatures were obtained from known literature. Data at 70℃ are shown below. Figure 3 As shown.

[0051] The relationship between the moisture content and water vapor pressure in paper with a correctable coefficient is shown in the following formula: In the formula, A This is a correction factor, dimensionless; p v This is the partial pressure of water vapor in the air, expressed in mmHg. T The temperature of the paper insulation is measured in K.

[0052] p v The relationship between relative humidity and air humidity can be expressed as follows: In the formula, RH is the relative humidity of the air; p v_sat This is the saturated vapor pressure, expressed in mmHg.

[0053] p v_sat It can be obtained from the antoine equation, as shown in the following equation: In the formula, A 1. B 1. C 1 is the antoine constant, which is taken as 8.07, 1730.63, and 233.42 in the range of 0~150℃.

[0054] In addition, the relative water saturation RS in oil is defined as the ratio of the water content in the oil to the saturated water content in the oil at that temperature, as shown in the following formula: In the formula, C oil This represents the water content in the oil, expressed in ppm (mass fraction). C oil_sat This represents the saturated water content in the oil, expressed in ppm (mass fraction). C oil_sat It can be calculated using the following formula: In the formula,B 2. C 2 is a specific coefficient. B The value of 2 ranges from 7.09 to 7.42. C The value of 2 is between 1567 and 1670.

[0055] Oommen proposed the following hypothesis in the literature: RH=RS Using the relationship between moisture content and water vapor pressure in paper mentioned above, Oommen proposed a hypothesis in the literature that the moisture content of paper can be used to establish... C pap and water content in oil C oil The balance relationship is shown in the following formula: Using the above balance relationship Figure 3 The data at medium and other temperatures were fitted to obtain the values ​​at different DP and temperatures. A The values ​​are shown in Table 1.

[0056] Table 1. Temperature and DP at different levels A value The table shows that under different DP conditions A Significant changes will occur, and under the same DP conditions, at different temperatures... A The only irregular deviations were considered random errors in the experiment, therefore the temperature was deemed incorrect. A The magnitude of has an impact. To eliminate random errors, A The average temperature was taken, as shown in the last column of Table 1. A The relationship between the average value and DP is as follows: Figure 4 As shown, A The linear relationship between DP and DP is relatively obvious, and the linear fitting result is as follows: Therefore, based on the above linear fitting results, the moisture balance relationship between the oil and paper at any temperature and any degree of aging (DP) of the insulating paper can be obtained, thus allowing the determination of the moisture content of the insulating oil. C oil Insulating paper DP, temperature T The moisture content in the insulating paper was calculated. C pap .

[0057] In this embodiment, independent relationships are established from three dimensions: equivalent air humidity, insulating oil water saturation, and insulating paper water absorption characteristics. This breaks down complex coupling relationships, providing the oil-paper moisture balance model with a clear and step-by-step mathematical foundation. Traditional oil-paper balance formulas do not differentiate between the aging states of insulating paper, and the moisture absorption curve is permanently fixed. This invention embeds a correction coefficient that varies with the degree of polymerization into the paper moisture content calculation formula, achieving adaptive correction of aging degree from the underlying mathematical relationship, thus solving the calculation deviation caused by changes in the paper's water absorption capacity after aging. Utilizing the mature assumption that oil saturation is equivalent to equivalent air relative humidity, a quantitative correlation is established between measurable moisture parameters on the oil side and indirect moisture content on the paper side. The internal moisture of the insulating paper can be indirectly calculated using only readily available on-site oil moisture, without the need for offline sampling that could damage the transformer insulation.

[0058] The solutions to the above-mentioned humidity and saturation relationships all depend on two fundamental limiting parameters: saturated vapor pressure and saturated water content in oil. Therefore, it is necessary to complete the calculation of the prerequisite parameters through thermodynamic equations and calibration coefficients to ensure that the moisture balance model can be solved completely.

[0059] In one possible implementation, before constructing the relationship between relative humidity and water vapor partial pressure in the air and saturated vapor pressure, the following is also included: The saturated vapor pressure corresponding to the current temperature is calculated based on the temperature and the Antoine equation. Before constructing the relationship between the relative water saturation of oil based on the water content and the saturated water content in the oil, the following steps are also included: Based on the temperature and a preset coefficient, the saturated water content in the oil corresponding to the current temperature is calculated.

[0060] In some embodiments, the Antoni equation is a classical thermodynamic equation describing the quantitative relationship between temperature and the partial pressure of saturated water vapor in pure water. It is the fundamental formula for calculating water vapor humidity and is used to solve for the limiting partial pressure of water vapor saturation at a specific temperature. The preset coefficients are fixed constants that have been pre-calibrated and stored through experiments. They include the solubility characteristic parameters corresponding to the insulating oil material and are used to calculate the saturated water content of the oil at the corresponding temperature, in conjunction with the temperature.

[0061] In this embodiment, the Antoine equation and a temperature-based preset coefficient are used to quantitatively solve two key parameters, completing the pre-calculation chain of the entire moisture balance model. The corresponding saturation parameters are dynamically calculated based on the real-time temperature of the insulating paper at each time period, and the basic limit values ​​are updated synchronously for each operating segment, eliminating the underlying calculation bias caused by fixed constant approximations. The Antoine equation is a recognized and mature water vapor thermodynamic model with high accuracy in calculating saturated vapor pressure; the oil saturated water content is correlated with temperature using experimentally calibrated fixed preset coefficients, eliminating the need for complex repeated field experiments, and allowing for rapid solution by simply inputting the real-time temperature.

[0062] After completing the construction of the dynamic oil paper moisture balance model, which can accurately obtain the moisture content in the paper at various time periods, in order to further quantify the influence of temperature and moisture on the aging rate, this invention obtains the quantitative correlation between the aging rate and the operating parameters based on the Arrhenius equation, providing theoretical support for the dynamic update of the instantaneous aging rate.

[0063] In practical implementation, existing research has shown that for second-order models... , k 10 This represents the initial aging rate. k 2 represents the rate of change of the aging rate, and the instantaneous aging rate is... When the temperature change is not significant, k 10 , k 2 conforms to the Arrhenius equation, as shown below: In the formula: a The frequency coefficient reflects the threshold frequency of effective collisions between molecules in a reaction system, and its unit is h. -1 ; E a The activation energy is expressed in kJ / mol. R This is the gas constant, typically 8.314 J / (mol·K); T Temperature is the thermodynamic temperature, measured in Kelvin (K).

[0064] When aging conditions remain constant, the remaining power consumption (DP) and expected life can be directly calculated using the original second-order model. However, during transformer operation, temperature... T Over time, and during the aging process, moisture content decreases or increases due to reactions involving consumption or generation. Furthermore, the moisture content has a significant impact on... a The value has a significant impact, leading to k It must be time-varying. Previous studies on the effect of moisture on the aging of insulating paper only considered the initial moisture content and treated it as a constant during the aging process. Therefore, the results of previous studies... k and a It is an average value over the entire aging process, and does not represent the situation at a certain moment or within a certain short period of time during the aging process.

[0065] The results of isothermal aging experiments with constant moisture content of insulating paper were obtained from known literature. Figure 5(a) shows the relationship between the degree of polymerization of the insulating paper and time at different constant temperatures with moisture contents of 0.5%, 1.6%, and 2.7% under low oxygen (<6000ppm) conditions. The initial degree of polymerization DP0 of the insulating paper was approximately 1200, 1 / DP t The value of -1 / DP0 changes over time as shown in Figure 5(b).

[0066] The points in Figure 5(b) were fitted using the second-order model equations, and the parameters of the aging model under different constant water content and constant temperature are shown in Table 2. Table 2. Temperature and Moisture Content at Different Temperatures and Moisture Contents k 10 , k 2 Transforming the Arrhenius equation yields: because E a , R , a Both are independent of temperature, therefore ln k With 1 / T A linear relationship will be presented.

[0067] Use the data in the table to plot ln k 10 ln k 2 and 1 / T Relationship such as Figure 6 As shown.

[0068] The activation energy for the aging reaction of insulating paper is 111 kJ / mol. The transformation formula of the Arrhenius equation is used to... Figure 6 Fit the data to obtain a The fitting results are shown in Table 3. a The relationship with the moisture content in paper is as follows: Figure 7 As shown.

[0069] Table 3 Experiments under different moisture contents a 10 , a 2 values The data in the graph were fitted using a quadratic polynomial to obtain... a 10 , a The relationship between the aging rate and the moisture content of the insulating paper is shown in the following formula, thus obtaining the quantitative relationship between the aging rate and the moisture content of the insulating paper, as shown in the following formula: In the formula, C pap This represents the moisture content of the paper, expressed as a mass fraction.

[0070] To adapt to the changing operating characteristics of transformers and solve the problem that aging damage under different temperature and water conditions cannot be directly superimposed, this invention introduces an equivalent aging duration mechanism, which, combined with dynamic instantaneous aging rate, completes accurate iterative calculation of aggregation degree in a single time period.

[0071] In one possible implementation, based on the instantaneous aging rate, time period duration, and the initial aggregation degree of the current time period, the final aggregation degree of the current time period is calculated using an improved second-order aging model, including: Calculate the equivalent aging time under the new conditions based on the instantaneous aging rate, the initial degree of polymerization at the current time period, and the factory degree of polymerization of the transformer insulation paper; By inputting the instantaneous aging rate, equivalent aging duration, time period duration, and the initial aggregation degree of the current time period into the improved second-order aging model, the final aggregation degree of the current time period can be calculated.

[0072] In some embodiments, the degree of polymerization at the factory is the original degree of polymerization of the transformer's new insulation paper at the time of manufacture, which is a fixed reference constant used to uniformly calculate the equivalent aging time under different aging degrees. The equivalent aging time is a virtual conversion time that converts the aging rate under the current operating conditions to the equivalent aging time corresponding to a unified reference operating condition (new insulation paper reference), eliminating the problem that aging times cannot be directly added due to differences in different temperature and water conditions.

[0073] In the specific implementation process, based on the time interval of the data points of the aging condition measurement data, for the changing aging conditions caused by varying temperature and moisture content in the paper, the aging situation in each interval under low oxygen conditions is calculated using a second-order model as shown in the following formula: In the formula, Δ t This represents the current interval length (i.e., the duration of the time period), in hours (h). i For interval counting.

[0074] To quantitatively calculate the decrease in DP during the aging process of insulating paper, the dynamic process of moisture content in the insulation paper and paperboard thickness and the oil paper insulation system is ignored, and the moisture content at the boundary of the insulating paper and paperboard is used instead of its internal moisture content.

[0075] The calculation method is as follows: Figure 8 As shown, the specific process is as follows: (1) Input the duration, temperature, water content in oil, and DP of the interval to be calculated.

[0076] (2) Use the above formula to calculate DP at the end of the interval.

[0077] (3) Determine whether the termination condition has been met. If yes, output the DP at the end time. Otherwise, repeat (1) to (3).

[0078] In this embodiment, the temperature and moisture of the transformer fluctuate constantly throughout different periods. The aging damage caused by the same actual duration under different operating conditions is completely different and cannot be directly accumulated. This invention introduces an equivalent aging duration for unified conversion, transforming the actual operating time under fluctuating conditions into an equivalent aging duration under a standard benchmark, thereby achieving a unified quantitative calculation of aging damage under different operating conditions. Instantaneous aging rate, equivalent aging duration, actual period duration, and initial aggregation degree are all used as model inputs. The improved second-order dynamic relationship is used to accurately calculate the final aggregation degree at the end of the current period, forming a standardized and programmable single-period aging quantitative calculation process. The updated final aggregation degree for each period is output, providing an initial aggregation degree for the calculation of the next period, forming a closed-loop calculation logic of time-series segmented iteration, completely simulating the entire process of continuous cumulative aging of the transformer under long-term fluctuating operating conditions. The instantaneous aging rate is updated according to real-time operating conditions in each period, and the equivalent duration is used to correct for differences in operating conditions. The aggregation degree decay is continuous, smooth, and without abrupt changes, effectively reducing the aggregation degree calculation error caused by segmented static parameters. Based on changes in aging conditions (temperature, moisture), the aging rate is adjusted in a timely manner, and the DP change is calculated point-in-time by following the measured temperature and moisture time-series data. Calculations can start from time zero or any time with a known DP. A general model for iterative calculation of DP between time points (i.e., within the interval of measurement points) is used. Starting with directly measured data such as temperature, moisture in oil, and time intervals, the moisture content in the paper is calculated from these data, thereby calculating the aging rate. Then, an improved second-order model is used to calculate the DP decrease within a time interval, and this process is repeated until all intervals have been calculated.

[0079] The key to the improved method lies in the timely change of the aging rate, which requires establishing a quantitative relationship between the aging rate and temperature and moisture content, so as to calculate the change in the aging rate in a timely manner. Based on experimental data from existing literature, the quantitative relationship required for the second-order model, i.e., k, was fitted. 10 The relationship between k2 and moisture, and the modified moisture balance of oil paper.

[0080] To clarify the innovative architecture of the improved second-order aging model of this invention and to distinguish it from the technical defects of the traditional static second-order model, the complete construction principle, variable constraints and aging connection mechanism of the model are explained in detail below.

[0081] In one possible implementation, the improved construction process of the post-second-order aging model includes: A second-order aging kinetic equation describing the decay of the degree of polymerization of insulating paper was established; The instantaneous aging rate, equivalent aging duration, time period duration, and initial polymerization degree of the current time period are used as model input parameters to improve the second-order aging kinetic equation; among them, the equivalent aging duration is calculated by the instantaneous aging rate, factory polymerization degree, and initial polymerization degree of the current time period. The instantaneous aging rate is defined as a variable that dynamically changes with temperature and moisture content of insulating paper at different times, and the degree of polymerization decreases continuously and smoothly with the aging process, thus obtaining an improved second-order aging model.

[0082] In practical implementation, the commonly used indicators to characterize the degree of cellulose degradation are the chain scission number (CSN) or the scission fraction of cellulose units (SFCU). CSN represents the average number of chain breaks per cellulose chain unit during aging, and SFCU represents the ratio of broken glucose units to total glucose units in the cellulose chain. The relationships between CSN, SFCU, and DP are shown in the following equations, where SFCU is the expression on the left side of the second-order aging kinetic model.

[0083] Both CSN and SFCU reflect the degree of reactant consumption or the number of chain ends generated, i.e., the degree of product production. Therefore, SFCU is similar to product concentration and can be used to measure the progress of the aging reaction. As a process quantity, it cannot change abruptly. Therefore, when using an aging kinetic model to describe the aging process, if the reaction conditions change, only the instantaneous aging rate will change accordingly, and subsequent aging will continue based on the new rate brought about by the new conditions.

[0084] The aging rate transition method when aging conditions change is as follows: Figure 9 As shown, curves A and B are the aging curves starting from zero under constant aging conditions A and B, respectively. Taking A as the initial condition, when aging reaches time ti, the aging condition abruptly changes to B. The aging rate, i.e., the slope of the curve, will abruptly change, while the ordinate 1 / DP - 1 / DP0 cannot abruptly change. Therefore, the aging process within the subsequent time interval Δt corresponds to the portion of curve B starting from the current ordinate value. If t... i+1 If the conditions change abruptly again after a certain point, the process of changing from condition A to condition B is repeated, and the curve continues under the next new condition. The overall aging curve is a splicing of aging curves under different constant aging conditions, segmented by the abrupt change points of aging conditions, as shown by the red solid line in the figure.

[0085] The above method of segmenting the aging process based on changes in aging conditions is specifically calculated using the following formula: In the formula, i Counting for conditional changes; Δ t i The aging time under new constant conditions; DP i and DP i+1They are respectively via Δ t i DP before and after aging; t grad_i Assuming aging from zero to DP under new conditions i Time; k 10_i , k 2_i They are respectively k 10 and k 2 in t i The instantaneous value of a moment.

[0086] Therefore, the decrease in DP after the reaction conditions change can be calculated. For cases where the conditions change multiple times, the total aging time can be divided into continuous time intervals according to the interval of the time series data points of the measured aging conditions. Assuming that the aging conditions remain unchanged within an interval, the aging conditions at the initial moment of the interval are used as the constant aging conditions within that interval. Then, the aging rate and instantaneous parameter values ​​at the initial moment can represent the average value within that interval. For each time interval, the decrease in DP after that interval can be calculated by segmenting the aging process. Thus, the calculation can be iterated from beginning to end until the specified duration.

[0087] In this embodiment, the second-order kinetic equation for the decay of the degree of polymerization of insulating paper serves as the framework, and the physical meaning of the model closely aligns with the aging mechanism of cellulose hydrolysis. An equivalent aging time is added as an input parameter to the traditional second-order equation, overcoming the limitation of traditional models in uniformly calculating aging damage under different temperature and moisture conditions. Simultaneously, the solution logic for the equivalent time is clearly defined, enabling the model to have condition-adjusted capabilities and providing a complete mathematical framework for segmented calculation of the degree of polymerization. The model limits only the instantaneous aging rate to dynamically change with temperature and moisture content, while the degree of polymerization decays continuously and smoothly. This constitutes a core innovation that distinguishes it from existing technologies. Traditional second-order models fit static parameters according to a fixed sampling period; this model updates only the instantaneous aging rate synchronously with real-time conditions at each time period, and the degree of polymerization decays continuously and smoothly throughout the process, aligning with the objective law of slow, non-jumping aging of insulating paper. The degree of polymerization can be calculated under varying temperature and moisture conditions.

[0088] After completing the full-time iterative aggregation degree calculation, it is necessary to rely on standardized judgment rules to transform the numerical aggregation degree results into feasible insulation aging level assessment conclusions, thereby realizing the quantitative judgment of aging status.

[0089] In one possible implementation, after all time-period iterations, the aging status assessment of the insulating paper is completed based on the final obtained degree of polymerization, including: Complete iterative calculations for all time periods, extract the final polymerization degree of the last time period, and use it as the real-time polymerization degree feature value of the insulating paper; The aging status assessment of transformer insulation paper is completed based on the real-time aggregation degree characteristic value and the preset insulation paper aging threshold.

[0090] In some embodiments, the real-time polymerization degree characteristic value of the insulating paper is the final end polymerization degree obtained through full-cycle iteration as the sole quantitative characteristic index, directly representing the total amount of aging damage to the winding insulating paper at present. The preset insulating paper aging threshold is a set of multiple polymerization degree critical values ​​pre-set based on power industry standards and test data, used to classify different aging levels such as intact insulation, mild aging, moderate aging, and severe failure.

[0091] In this embodiment, the final degree of polymerization is extracted after all time-series iterations are completed, fully accumulating all aging damage of the transformer under variable load, temperature, and humidity conditions over many years. The evaluation results can accurately reflect the overall aging level of the insulation, eliminating misjudgments caused by data from local time periods. The degree of polymerization is directly used as the core feature quantity, corresponding one-to-one with the degree of cellulose breakage, with a clear physical meaning. Compared to indirect parameters such as temperature and moisture, it can intuitively and accurately reflect the degree of aging damage inside the insulation paper. By comparing and judging using pre-calibrated aging thresholds, subjective human experience is eliminated, forming a standardized grading evaluation system. The output aging level can be directly used as a quantitative basis for transformer maintenance, replacement, and load adjustment, improving the objectivity of equipment operation and maintenance decisions.

[0092] To further expand the engineering application value of the method, based on the current insulation aging status assessment, this invention relies on the same core model to build an iterative prediction mechanism for remaining life adapted to changing operating conditions, thereby realizing integrated analysis of status assessment and life prediction.

[0093] In one possible implementation, after iterating through all time periods and assessing the aging status of the insulating paper based on the final obtained degree of polymerization, the following steps are also included: The initial expected lifespan of the insulating paper is set, the existing moisture content in the oil at the end of the aging assessment is used as the baseline moisture content, and the moisture growth rate of the insulating oil is calculated based on the transformer operating conditions. Combined with the preset future operating temperature, baseline moisture content, and duration of each time interval, the future real-time moisture content in the oil within each time interval is determined. The initial moisture content of the insulating paper at the corresponding time period is calculated based on the real-time moisture balance relationship between the oil and the paper. The instantaneous aging rate is calculated based on the initial moisture content and the preset future operating temperature. The degree of polymerization decay is solved for time intervals using the improved second-order aging model, and the remaining degree of polymerization of the insulating paper under the current expected lifespan is obtained iteratively. Determine whether the remaining degree of polymerization has reached the preset termination calculation condition; When the termination calculation condition is not met, the initial expected lifetime is adjusted, and the steps to determine the future real-time water content in the oil and subsequent steps are repeated. When the termination calculation conditions are met, record the final expected lifespan and the corresponding remaining degree of polymerization to determine the remaining service life of the insulating paper.

[0094] In some embodiments, the baseline moisture content is the actual moisture content of the transformer insulating oil detected at the time the aging assessment is completed, serving as the initial moisture baseline for future lifespan projections. The moisture growth rate of the insulating oil is the rate of increase in insulating oil moisture per unit time obtained by fitting transformer sealing, operating conditions, and ambient humidity, used to project oil moisture changes in future time periods. The degree of polymerization decay is the decrease in the degree of polymerization of the insulating paper calculated by the improved second-order aging model within a single future time interval, representing the newly added aging damage in that interval. The remaining degree of polymerization is the value of the degree of polymerization of the insulating paper obtained by adding the aging losses of each future interval, starting from the current actual degree of polymerization. The remaining service life is the total expected operating time corresponding to the fulfillment of the termination failure conditions, i.e., the time during which the transformer insulating paper can still operate safely from its current state until aging failure.

[0095] In practice, given the measured aging conditions, the termination condition is reaching the specified calculated aging time. If it is necessary to continue predicting the remaining life based on the measured aging conditions, the calculation continues intermittently based on the predicted subsequent aging conditions. When DP decreases to close to 200, its tensile strength is halved, and it completely loses its mechanical strength and support capacity, thus reaching the end of its lifespan. Therefore, the specified termination condition is that DP is greater than 200 in the current cycle and less than 200 after one additional cycle. The intervals involved in the calculation during this process are accumulated to obtain the predicted remaining lifespan.

[0096] The initial moisture content of the insulation in a newly manufactured transformer is approximately 0.5%. During the transformer's service life, due to aging and external moisture intrusion, the moisture content of the paper insulation can reach 5% by the end of the transformer's lifespan. It is assumed that the moisture content of the insulation paper increases linearly during aging. Temperature is then predicted based on existing measurement data, typically in the form of... Figure 10 As shown.

[0097] Insulation life is achieved through methods such as Figure 11 The calculation process shown terminates when DP is greater than 200 under the current expected lifespan but less than 200 after one year.

[0098] Since general life prediction is all based on unimproved aging kinetic models, a life prediction method matching the improved model is proposed. When the unimproved model is used for life prediction, since the aging curve of the unimproved model is not segmented and is a single function, it is usually straightforward to set the terminal degree of polymerization (DP) = 200, solve the equation to obtain the terminal time, which is the predicted life. However, since the improved model is a segmented function and cannot directly solve the equation, the matching prediction method adopts forward calculation: it judges whether the assumed life is correct by testing whether the forward calculation result is reasonable, so the purpose of looping is to perform multiple trial and error. Under the above-mentioned life prediction method, the adopted aging conditions are variable temperature and moisture, while the prediction method using the unimproved model adopts constant temperature and moisture.

[0099] In this embodiment, future moisture content in oil is updated interval by interval based on the moisture growth rate, and the moisture balance and aging damage of oil-paper are dynamically deduced, which greatly improves the authenticity of life prediction. The repeated cyclic deduction is carried out by adjusting the initial expected life until the residual degree of polymerization reaches the failure threshold, which eliminates the need for manual estimation, simplifies the calculation process, can automatically output the accurate remaining service life of insulation, and realizes numerical life prediction. The current actual degree of polymerization and on-site measured moisture in oil are taken as the deduction benchmark, instead of the ideal state of brand-new insulation paper, the accumulated historical aging damage of the equipment is fully considered, so the prediction result is more consistent with the real health level of the equipment. Adding a life prediction module on the basis of the previous quantitative assessment of insulation aging can not only judge the current insulation aging level, but also predict the insulation failure time, providing a long-term quantitative decision-making basis for transformer maintenance planning, equipment replacement and load regulation. The future time is calculated in sections, and the temperature, moisture in oil and instantaneous aging rate are updated independently in each interval to simulate the gradual aging under dynamic working conditions such as seasonal load and increased moisture ingress, which is different from the static life estimation with fixed temperature and humidity, and the prediction error is smaller.

[0100] Aiming at the problem that the existing methods for evaluating the aging state of insulating paper based on aging kinetic models are only applicable to constant temperature and do not consider the change of moisture content of insulating paper during the aging process, an insulation paper aging state assessment method based on an improved second-order aging kinetic model that can be used under variable temperature and moisture conditions is proposed.

[0101] The improved second-order aging kinetics model calculation process is as follows: Using the sampling interval of data points measuring temperature and water content in the oil as a benchmark, assuming the aging conditions remain constant within the interval, the instantaneous aging rate at the start of the interval is calculated by measuring the temperature and water content in the oil. The instantaneous aging rate constant at the start is used as the average aging rate constant within the interval. Based on this constant condition, the DP decrease within the interval is calculated using the second-order model. The DP at the end of the previous interval is used as the DP at the start of the next interval, and the calculation is continued until a specified time. The last DP value within the specified time is the aging state of the insulating paper to be evaluated. If the predicted temperature and moisture content are given, the expected remaining life under the current state can be obtained by combining these with termination conditions.

[0102] Based on the proposed degree of polymerization calculation method, a lifetime prediction method based on varying temperature and moisture conditions is presented. By cyclically testing the assumed lifetime against the expected temperature and moisture changes, a reasonable lifetime prediction is ultimately obtained.

[0103] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0104] The following are device embodiments of the present invention. For details not described in detail, please refer to the corresponding method embodiments described above.

[0105] Figure 12 A schematic diagram of the transformer insulation paper aging status assessment device provided in an embodiment of the present invention is shown. For ease of explanation, only the parts related to the embodiment of the present invention are shown, and are described in detail below: like Figure 12 As shown, the transformer insulation paper aging condition assessment device 12 includes: The communication module 121 is used to acquire the timing operation data of the transformer to be evaluated; wherein, the timing operation data includes the temperature of the insulating paper, the moisture content of the insulating oil, and the duration of each time period; The processing module 122 is used to calculate the initial moisture content of the insulating paper for each time period based on the initial degree of polymerization, moisture content in the oil, temperature, and a pre-constructed oil-paper moisture balance relationship. The oil-paper moisture balance relationship is constructed based on a correction coefficient that changes linearly with the degree of polymerization. Based on the initial moisture content and temperature, the instantaneous aging rate of the current time period is calculated. Based on the instantaneous aging rate, time period duration, and initial degree of polymerization of the current time period, the final degree of polymerization of the current time period is calculated using an improved second-order aging model, which serves as the initial degree of polymerization for the next time period. After iterating through all time periods, the aging status assessment of the insulating paper is completed based on the final obtained final degree of polymerization.

[0106] Figure 13 This is a schematic diagram of an electronic device provided in an embodiment of the present invention. For example... Figure 13 As shown, the electronic device 13 of this embodiment includes a processor 130 and a memory 131. The memory 131 stores a computer program 132. When the processor 130 executes the computer program 132, it implements the steps in the various method embodiments described above. Alternatively, when the processor 130 executes the computer program 132, it implements the functions of each module / unit in the various device embodiments described above.

[0107] For example, computer program 132 may be divided into one or more modules / units, which are stored in memory 131 and executed by processor 130 to complete the present invention. The one or more modules / units may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of computer program 132 in electronic device 13.

[0108] Electronic device 13 may include, but is not limited to, processor 130 and memory 131. Those skilled in the art will understand that... Figure 13 This is merely an example of electronic device 13 and does not constitute a limitation on electronic device 13. It may include more or fewer components than shown, or combine certain components, or different components. For example, electronic device 13 may also include input / output devices, network access devices, buses, etc.

[0109] For the sake of simplicity and clarity, only the above-described functional modules / units are used as examples. In practical applications, the functions described above can be assigned to different functional modules / units as needed. These modules / units can be implemented in hardware, software, or a combination of both.

[0110] In the above embodiments, the descriptions of each embodiment have their own emphasis. Parts not detailed or described in a particular embodiment can be referred to in the relevant descriptions of other embodiments. Unless otherwise specified or in conflict with logic, the terminology and / or descriptions between different embodiments are consistent and can be referenced interchangeably. Technical features in different embodiments can be combined to form new embodiments based on their inherent logical relationships.

[0111] 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, and should all be included within the protection scope of the present invention.

Claims

1. A method for assessing the aging status of transformer insulation paper, characterized in that, include: Obtain the time-series operation data of the transformer to be evaluated; wherein, the time-series operation data includes the temperature of the insulating paper, the moisture content of the insulating oil, and the duration of each time period; For each time period, the initial moisture content of the insulating paper for the current time period is calculated based on the initial degree of polymerization, the moisture content in the oil, the temperature, and the pre-constructed oil-paper moisture balance relationship; wherein the oil-paper moisture balance relationship is constructed based on a correction coefficient that varies linearly with the degree of polymerization. Calculate the instantaneous aging rate for the current time period based on the initial moisture content and the temperature; Based on the instantaneous aging rate, the duration of the time period, and the initial aggregation degree of the current time period, the final aggregation degree of the current time period is calculated using the improved second-order aging model, and used as the initial aggregation degree of the next time period. After all time periods are iterated, the aging status of the insulating paper is evaluated based on the final degree of polymerization.

2. The method for assessing the aging status of transformer insulation paper according to claim 1, characterized in that, The calculation of the initial moisture content of the insulating paper for the current period, based on the initial degree of polymerization, the moisture content in the oil, the temperature, and the pre-established moisture balance relationship between the oil and paper, includes: The correction coefficient is calculated based on the initial aggregation degree of the current time period and the first preset function; The initial moisture content of the insulating paper for the current time period is calculated based on the moisture content in the oil, the temperature, the correction factor, and the moisture balance formula of the oil-paper mixture.

3. The method for assessing the aging status of transformer insulating paper according to claim 2, characterized in that, Before calculating the initial moisture content of the insulating paper for the current time period, the method further includes: Based on the partial pressure of water vapor in the air and the saturated vapor pressure, a formula for the relationship between relative humidity of air is constructed. Based on the water content and saturated water content in the oil, a formula for the relative water saturation of the oil is constructed. Based on the correction factor, the partial pressure of water vapor in the air, and the temperature, a formula is constructed to describe the relationship between the moisture content of paper and the water vapor pressure. Based on the equivalent assumption of relative saturation of water in oil and relative humidity of air, and combining the relationship between relative humidity of air, relative saturation of water in oil, and the relationship between water content in paper and water vapor pressure, the moisture balance relationship of oil-paper is constructed.

4. The method for assessing the aging status of transformer insulating paper according to claim 3, characterized in that, Before constructing the relationship between relative humidity and water vapor partial pressure and saturated vapor pressure in the air, the following steps are also included: The saturated vapor pressure corresponding to the current temperature is calculated based on the temperature and the Antoine equation. Before constructing the relationship between the relative water saturation of oil based on the water content and the saturated water content in the oil, the following steps are also included: Based on the temperature and a preset coefficient, the saturated water content in the oil corresponding to the current temperature is calculated.

5. The method for assessing the aging status of transformer insulating paper according to any one of claims 1-4, characterized in that, The step of calculating the final aggregation degree of the current time period based on the instantaneous aging rate, the time period duration, and the initial aggregation degree of the current time period, using an improved second-order aging model, includes: Based on the instantaneous aging rate, the initial degree of polymerization in the current period, and the factory degree of polymerization of the transformer insulation paper, calculate the equivalent aging time under the new conditions; The instantaneous aging rate, the equivalent aging duration, the time period duration, and the initial aggregation degree of the current time period are input into the improved second-order aging model to calculate the final aggregation degree of the current time period.

6. The method for assessing the aging status of transformer insulating paper according to any one of claims 1-4, characterized in that, The construction process of the improved second-order aging model includes: A second-order aging kinetic equation describing the decay of the degree of polymerization of insulating paper was established; The instantaneous aging rate, equivalent aging duration, time period duration, and initial aggregation degree of the current time period are used as model input parameters to improve the second-order aging kinetic equation; wherein, the equivalent aging duration is calculated by the instantaneous aging rate, factory aggregation degree, and initial aggregation degree of the current time period. The instantaneous aging rate is defined as a variable that dynamically changes with temperature and moisture content of insulating paper at different time periods, and the degree of polymerization decreases continuously and smoothly with the aging process, thus obtaining the improved second-order aging model.

7. The method for assessing the aging status of transformer insulating paper according to claim 1, characterized in that, After all time-period iterations, the aging status assessment of the insulating paper is completed based on the final obtained degree of polymerization, including: Complete iterative calculations for all time periods, extract the final polymerization degree of the last time period, and use it as the real-time polymerization degree feature value of the insulating paper; The aging status assessment of transformer insulation paper is completed based on the real-time polymerization degree characteristic value and the preset insulation paper aging threshold.

8. The method for assessing the aging status of transformer insulation paper according to claim 1, characterized in that, After all time-period iterations, and based on the final obtained degree of polymerization, the aging status assessment of the insulating paper is completed, the following steps are also included: The initial expected lifespan of the insulating paper is set, the existing moisture content in the oil at the end of the aging assessment is used as the baseline moisture content, and the moisture growth rate of the insulating oil is calculated according to the transformer operating conditions. Combined with the preset future operating temperature, the baseline moisture content, and the duration of each time interval, the future real-time moisture content in the oil within each time interval is determined. Based on the real-time moisture content in the oil and the moisture balance between the oil and paper, the initial moisture content of the insulating paper for the corresponding time period is calculated. The instantaneous aging rate is calculated from the initial moisture content and the preset future operating temperature. The degree of polymerization decay is solved for time intervals by the improved second-order aging model, and the remaining degree of polymerization of the insulating paper under the current expected life is obtained iteratively. Determine whether the remaining degree of polymerization has reached the preset termination calculation condition; When the termination calculation condition is not met, the initial expected lifespan is adjusted, and the steps to determine the future real-time water content in the oil and subsequent steps are repeated. When the termination calculation conditions are met, record the final expected lifespan and the corresponding remaining degree of polymerization to determine the remaining service life of the insulating paper.

9. A device for assessing the aging status of transformer insulation paper, characterized in that, include: A communication module is used to acquire the time-series operation data of the transformer to be evaluated; wherein, the time-series operation data includes the temperature of the insulating paper, the moisture content in the insulating oil, and the duration of each time period; The processing module is used to calculate the initial moisture content of the insulating paper for each time period based on the initial degree of polymerization, the moisture content in the oil, the temperature, and a pre-constructed oil-paper moisture balance relationship; wherein the oil-paper moisture balance relationship is constructed based on a correction coefficient that changes linearly with the degree of polymerization; calculate the instantaneous aging rate for the current time period based on the initial moisture content and the temperature; calculate the final degree of polymerization for the current time period based on the instantaneous aging rate, the time period duration, and the initial degree of polymerization for the current time period using an improved second-order aging model, which serves as the initial degree of polymerization for the next time period; after iterating through all time periods, complete the aging status assessment of the insulating paper based on the final obtained final degree of polymerization.

10. An electronic device, characterized in that, It includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the method as described in any one of claims 1 to 8.

Images