Method and system for determining winding hot-spot temperature threshold value of oil-immersed power transformer

Abstract

The invention relates to a method and a system for determining a hot-spot temperature threshold value of an oil-immersed power transformer winding. The method comprises the following steps: constructing a residual life evaluation model of a transformer insulation system based on historical data; constructing a calculation model of a long-term hot-spot temperature threshold value of the to-be-evaluated transformer based on the apparent life, the actual operation time and the total design life of the to-be-evaluated transformer; determining the bubble initial temperature of bubbles separated out by the insulation paper based on the internal total pressure of an oil tank of the transformer, the paper moisture content and the oil-paper polymerization degree, and taking the bubble initial temperature as a short-term hot-spot temperature threshold value of a transformer winding; setting a winding hot-spot temperature threshold of the to-be-evaluated transformer based on the long-term hot-spot temperature threshold and the short-term hot-spot temperature threshold of the to-be-evaluated transformer; the set temperature threshold not only reflects the current health condition of the transformer, but also integrates the prediction of the future service life and possible risk factors, so that the maximum operation efficiency of the transformer can be realized on the premise of ensuring the safety.

Description

Technical Field

[0001] The present invention relates to the field of transformer monitoring in power systems, and in particular to a method and system for determining a hot spot temperature threshold value of a winding of an oil-immersed power transformer. Background Art

[0002] As the core hub for power system energy conversion and network topology adjustment, transformers undertake important tasks such as voltage level conversion, power transmission optimization, and power quality control. Their safe and stable operation is crucial for ensuring the reliability of power supply. Insulation problems within transformers are one of the main causes of transformer failure. Winding hotspot temperature, a key factor affecting the aging rate of transformer oil-paper insulation, has a significant impact on the transformer's load capacity and determines whether the transformer is operating safely and reliably. Therefore, it is particularly important to determine the transformer winding hotspot temperature threshold and ensure that the transformer winding hotspot temperature remains below the threshold.

[0003] Existing transformer winding hotspot temperature thresholds are primarily defined by GB / T 1094.7-2008 and IEC 60076-7. When the hotspot temperature of a transformer winding is 98°C, the aging rate of oil-paper insulation (non-thermally modified paper) is 1. Within 140°C, the hotspot temperature and the aging rate of the oil-paper insulation follow a 6°C rule: for every 6°C increase in hotspot temperature, the insulation aging rate doubles. Under normal cyclic load conditions, the hotspot temperature of the winding must not exceed 120°C. This standard does not specify differentiated hotspot temperature thresholds for transformers at different aging stages, failing to fully realize the potential of the equipment at different aging stages. Summary of the Invention

[0004] In response to the technical problems existing in the prior art, the present invention provides a method and system for determining the hot spot temperature threshold of an oil-immersed power transformer winding. The set temperature threshold not only reflects the current health status of the transformer, but also incorporates predictions about its future lifespan and possible risk factors, thereby ensuring that the transformer can achieve maximum operating efficiency while ensuring safety.

[0005] According to a first aspect of the present invention, a method for determining a hot spot temperature threshold of an oil-immersed power transformer winding is provided, comprising: Constructing a remaining life assessment model for a transformer insulation system based on historical data, wherein the remaining life assessment model is a function of the logarithm of the furfural content obtained by decomposing insulating paper in the transformer insulation system and the operating time of the transformer; Calculating the apparent life of the transformer to be evaluated based on the remaining life evaluation model, and constructing a calculation model for the long-term hot spot temperature threshold of the transformer to be evaluated based on the apparent life, actual operating time and total design life of the transformer to be evaluated; Determine the bubble initiation temperature of bubbles precipitated from the insulating paper based on the total internal pressure of the oil tank of the transformer to be evaluated, the moisture content of the paper, and the oil-paper polymerization degree, and use the bubble initiation temperature as the short-term hot spot temperature threshold of the transformer winding; The long-term hot spot temperature threshold of the transformer to be evaluated is calculated based on the calculation model, and the winding hot spot temperature threshold of the transformer to be evaluated is set based on the long-term hot spot temperature threshold and the short-term hot spot temperature threshold of the transformer to be evaluated.

[0006] On the basis of the above technical solution, the present invention can also make the following improvements.

[0007] Optionally, the remaining life assessment model is ; Among them, fur is the furfural content, t is the operating time of the transformer, and a, b, and c are constant parameters calculated based on historical data.

[0008] Optionally, the remaining life assessment model is ; Among them, fur is the furfural content, t is the operating time of the transformer.

[0009] Optionally, the calculation model of the long-term hotspot temperature threshold is ;in, is the long-term hotspot temperature threshold, is the total design life of the transformer, is the operating time of the transformer, is the estimated apparent life of the transformer.

[0010] Optionally, the calculation model formula of the short-term hotspot temperature threshold is: ; in, P is the total pressure inside the tank, W is the moisture content of the paper, A is a constant parameter related to the degree of polymerization of oil paper, B、n It is a constant parameter calculated based on historical data.

[0011] Optionally, the calculation formula of the constant parameter A related to the polymerization degree of the oil paper is: , DP is the degree of polymerization of oil paper; nB The value is 7064.8, n The value of is 1.4959.

[0012] Optionally, the calculation formula of the degree of polymerization DP of the oil paper is: ; fur is the furfural content, DP is the degree of polymerization of oil paper.

[0013] Optionally, the process of setting the winding hot spot temperature threshold of the transformer to be evaluated based on the long-term hot spot temperature threshold and the short-term hot spot temperature threshold of the transformer to be evaluated includes: The minimum value of the long-term hot spot temperature threshold and the short-term hot spot temperature threshold is selected as the winding hot spot temperature threshold of the transformer to be evaluated.

[0014] According to a second aspect of the present invention, there is provided a system for determining a hotspot temperature threshold value for an oil-immersed power transformer winding, comprising: a remaining life assessment model construction module, a long-term hotspot temperature threshold determination module, a short-term hotspot temperature threshold determination module, and a hotspot temperature threshold determination module; The remaining life assessment model construction module is used to construct a remaining life assessment model for the transformer insulation system based on historical data, wherein the remaining life assessment model is a function of the relationship between the logarithm of the furfural content obtained by decomposing the insulation paper in the transformer insulation system and the operating time of the transformer; The long-term hot spot temperature threshold determination module is used to calculate the apparent life of the transformer to be evaluated based on the remaining life assessment model, and to construct a calculation model for the long-term hot spot temperature threshold of the transformer to be evaluated based on the apparent life, actual operating time and total design life of the transformer to be evaluated; The short-term hot spot temperature threshold determination module is used to determine the bubble initiation temperature of bubbles precipitated from the insulating paper based on the total pressure inside the oil tank of the transformer to be evaluated, the moisture content of the paper, and the oil-paper polymerization degree, and use the bubble initiation temperature as the short-term hot spot temperature threshold of the transformer winding; The hotspot temperature threshold determination module is configured to set the winding hotspot temperature threshold of the transformer to be evaluated based on the long-term hotspot temperature threshold and the short-term hotspot temperature threshold of the transformer to be evaluated.

[0015] The present invention provides a method, system, electronic device and storage medium for determining the hotspot temperature threshold of the winding of an oil-immersed power transformer. First, a remaining life assessment model of the transformer insulation system is established to determine the long-term winding hotspot temperature threshold of the transformer. Then, by improving the bubble starting temperature calculation formula to reflect the change in the degree of polymerization of the insulating paper cellulose, the short-term winding hotspot temperature threshold of the transformer is determined. Finally, a differentiated hotspot temperature threshold determination method is obtained. These set temperature thresholds not only reflect the current health status of the transformer, but also incorporate predictions of its future life and possible risk factors. On this basis, the load capacity of the transformer is optimized and the safety margin is determined, which can ensure that the transformer can achieve maximum operating efficiency while ensuring safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A flow chart of a method for determining a hot spot temperature threshold value of an oil-immersed power transformer winding provided by the present invention; Figure 2 A schematic diagram of the relationship between the measured data of the furfural content of a transformer and the operating time provided by an embodiment of the present invention; FIG3 (a) is a schematic diagram showing the relationship between furfural content and operating time provided by an embodiment of the present invention; FIG3( b ) is a schematic diagram of the relationship between aggregation degree and running time provided by an embodiment of the present invention; Figure 4 A schematic diagram of the thermal aging life status of a transformer provided by an embodiment of the present invention; Figure 5 A schematic diagram of a transformer thermal aging life status assessment provided by an embodiment of the present invention; Figure 6 A schematic diagram of bubble initiation temperature under different polymerization degrees and water contents provided by an embodiment of the present invention; Figure 7 A schematic diagram of parameter fitting under different polymerization degrees and moisture contents provided by an embodiment of the present invention; Figure 8 A schematic diagram showing comparison of results under different parameters of a temperature threshold determination method provided by the present invention; Figure 9 The present invention provides a flow chart of an embodiment of a method for determining a hot spot temperature threshold value of an oil-immersed power transformer winding. DETAILED DESCRIPTION

[0017] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0018] FIG1 is a flow chart of a method for determining a hot spot temperature threshold value of an oil-immersed power transformer winding provided by the present invention. As shown in FIG1 , the method includes: Step 1: construct a remaining life assessment model for the transformer insulation system based on historical data. The remaining life assessment model is a function of the relationship between the logarithm of the furfural content obtained by decomposing the insulation paper in the transformer insulation system and the operating time of the transformer.

[0019] Step 2: Calculate the apparent life of the transformer to be evaluated based on the remaining life evaluation model, and construct a calculation model for the long-term hot spot temperature threshold of the transformer to be evaluated based on the apparent life, actual operating time and total design life of the transformer to be evaluated.

[0020] Step 3: Determine the bubble initiation temperature of bubbles precipitated from the insulating paper based on the total internal pressure of the oil tank of the transformer to be evaluated, the moisture content of the paper, and the oil-paper polymerization degree, and use the bubble initiation temperature as the short-term hot spot temperature threshold of the transformer winding.

[0021] Step 4: setting a winding hot spot temperature threshold of the transformer to be evaluated based on the long-term hot spot temperature threshold and the short-term hot spot temperature threshold of the transformer to be evaluated.

[0022] The present invention provides a method for determining the hot spot temperature threshold of the winding of an oil-immersed power transformer. First, the method combines the historical operating data of the transformer to establish a remaining life assessment model for the transformer insulation system and determine the long-term winding hot spot temperature threshold of the transformer. The bubble starting temperature calculation formula is used to reflect the change in the polymerization degree of the insulating paper cellulose, so that the model can adapt to transformers at different aging stages, determine the short-term winding hot spot temperature threshold of the transformer, and finally obtain a differentiated hot spot temperature threshold determination method. These set temperature thresholds not only reflect the current health status of the transformer, but also incorporate predictions of its future life and possible risk factors. On this basis, the load capacity of the transformer is optimized and the safety margin is determined, which can ensure that the transformer can achieve maximum operating efficiency under the premise of ensuring safety.

[0023] Example 1 The embodiment 1 provided by the present invention is an embodiment of a method for determining a hot spot temperature threshold value of an oil-immersed power transformer winding provided by the present invention, Figure 1 It can be seen that the embodiment of the temperature threshold determination method includes: Step 1: construct a remaining life assessment model for the transformer insulation system based on historical data. The remaining life assessment model is a function of the relationship between the logarithm of the furfural content obtained by decomposing the insulation paper in the transformer insulation system and the operating time of the transformer.

[0024] Transformers consist of components such as the core, windings, oil-paper insulation systems, and auxiliary equipment. These components are subject to thermal, electrical, and mechanical stresses, and undergo various aging mechanisms. Dissolved gas analysis (DGA) is a key technique for characterizing transformer thermal aging. Increased temperature affects the moisture balance in the oil-paper insulation system, promoting moisture migration and accelerating the aging of the paper insulation. Furthermore, increased temperature accelerates oxidation reactions in the oil and paper, producing acidic compounds and accelerating the degradation of the paper insulation, leading to a decrease in insulation performance. Furthermore, high temperatures accelerate the decomposition of cellulose in the insulation paper and the formation of furfural. Regarding electrical properties, increased temperature reduces oil viscosity, affecting its insulation properties and lowering its breakdown voltage. At high temperatures, the increased water solubility and dissolved acids reduce the oil's dielectric strength, thereby lowering its breakdown voltage (DBV). Increased temperature also increases the oil's conductivity, altering polarization processes and increasing the dissipation factor (DF), meaning greater energy loss in an alternating electric field.

[0025] Integrating the characteristics of thermal aging parameters, the present invention identifies furfural, DGA, oil moisture content, acid, DF, DBV, and other parameters as thermal aging health status indicators. These parameters not only directly reflect the transformer's current thermal aging state but are also crucial for accurately assessing the transformer's remaining thermal aging lifespan. The load can be flexibly adjusted based on the transformer's current health and expected lifespan loss. If the assessment results indicate that the transformer is in a delayed aging state, the hotspot temperature threshold can be controlled and its load increased in the short term without compromising its long-term reliability.

[0026] Furfural is present in transformer oil, but it is primarily related to the decomposition of the insulation paper, not the oil. This characteristic provides a method for indirectly assessing the degree of insulation paper aging by monitoring the furfural content in the oil. Field experience has shown that there is a good linear relationship between the logarithm of the furfural content in the oil and the degree of polymerization of the insulation paper. For transformers using non-thermally modified insulation paper, the degree of polymerization ( D P ) and furfural (fur) content satisfy the following logarithmic relationship: (1) In one possible embodiment, the remaining life assessment model is ; Among them, fur is the furfural content, t is the operating time of the transformer in h, and a, b, and c are constant parameters calculated based on historical data.

[0027] In one embodiment, the relationship between the logarithm of furfural mass concentration (unit: mg / L) and the transformer operating time is: (2) In another embodiment, the relationship between the logarithm of furfural mass concentration (unit: mg / L) and the transformer operating time is: (3) Where, t is the operating time of the transformer in h.

[0028] This study collected historical data on furfural content in the oil of 127 transformers in a region without oil changes and visualized the data, as shown in Figure 2. As can be seen from Figure 2, while furfural levels are discrete, the overall trend is that furfural content increases exponentially with increasing operating time. Further data fitting combined with this data yielded the relationship between the logarithm of furfural content and operating time, as shown in Equation (4).

[0029] (4) As shown in Figure 3 (a), a schematic diagram of the relationship between furfural content and operating time provided by an embodiment of the present invention, a comparative analysis of the above-mentioned types of results shows that there are significant differences in the results obtained by evaluating the operating time using different statistical results. The main reason is the difference in the operating environment of the transformer. For example, formula (2) is a formula obtained using data from 74 transformers, and most of the transformers sampled in formula (3) are operating at close to full load. Combined with formula (1), the relationship between the polymerization degree of the insulating paper in the transformer and the operating years in the relationship can be further obtained. As shown in Figure 3 (b), a schematic diagram of the relationship between the polymerization degree and operating time provided by an embodiment of the present invention is shown.

[0030] It can be seen that there are significant differences in the initial polymerization degrees obtained using different formulas. The original polymerization degree of insulating paper is about 1000-1200. Based on this analysis, the data reflected by formula (3) and formula (4) obtained by the present invention are more reasonable.

[0031] Step 2: Calculate the apparent life of the transformer to be evaluated based on the remaining life evaluation model, and construct a calculation model for the long-term hot spot temperature threshold of the transformer to be evaluated based on the apparent life, actual operating time and total design life of the transformer to be evaluated.

[0032] Transformers are affected by factors such as the operating environment and load, and may exhibit accelerated aging, equivalent aging, or delayed aging patterns as shown. Accelerated aging is often caused by high loads or poor heat dissipation. In such cases, operating strategies must be adjusted to delay aging and ensure the transformer's long-term stable operation. Equivalent aging typically involves uniform aging of the transformer under standard operating conditions. Combined with routine maintenance and inspections, the transformer can operate beyond its design lifespan. Delayed aging, on the other hand, occurs primarily due to low operating loads and low ambient temperatures, which cause the transformer's aging rate to fall below the design standard. In these cases, the load can be appropriately increased to improve utilization.

[0033] As shown in FIG4 , a schematic diagram of the thermal aging life status of a transformer provided by an embodiment of the present invention is shown. If the aging rate of the transformer is lower than expected and it is hoped that the transformer still follows the design life, the operating aging rate of the transformer can be adjusted. If the transformer is in a state of delayed aging, the temperature threshold can be appropriately increased. If the transformer is in a state of accelerated aging, the temperature threshold can be appropriately lowered. Combining the operating conditions of the three operating modes of the transformer, namely accelerated aging, equivalent aging, and delayed aging, a plot is drawn according to the furfural content-time relationship. As shown in FIG5 , a schematic diagram of the thermal aging life status evaluation of the transformer provided by an embodiment of the present invention is shown. In conjunction with FIG5 , it can be seen that the relationship between the furfural content of the transformer and the operating time is as follows: when the furfural content of a certain transformer is known, its apparent life can be determined based on the furfural content of the transformer.

[0034] Assume that a transformer T 1 has a total design life of 40 years. The estimated operating life based on furfural content corresponds to the dashed line of approximately 20 years. Based on these calculations, its thermal aging life is comparable to that of a similar transformer operating normally for 20 years. If its actual operating age is 30 years, it can be considered to be in a state of life extension. That is, over the next 10 years, the transformer can consume 20 years of normal aging life, and the winding hotspot temperature threshold can be increased. If its actual operating age is 10 years, it is considered to be in a state of accelerated aging. That is, over the next 30 years, the transformer can consume 20 years of normal aging life, and the hotspot temperature threshold needs to be appropriately lowered.

[0035] When the transformer winding hotspot temperature is 98°C, the aging rate of oil-paper insulation (non-thermally modified paper) is 1. Within 140°C, the hotspot temperature and the aging rate of oil-paper insulation follow a 6°C rule: for every 6°C increase in hotspot temperature, the insulation aging rate doubles. Therefore, based on the insulation life loss equivalent method, the long-term hotspot temperature threshold can be determined using Equation (5).

[0036] (5) Where, is the long-term hotspot temperature threshold, is the total design life of the transformer, is the operating life of the transformer, is the estimated apparent life of the transformer.

[0037] Step 3: Determine the bubble initiation temperature of bubbles precipitated from the insulating paper based on the total internal pressure of the oil tank of the transformer to be evaluated, the moisture content of the paper, and the oil-paper polymerization degree, and use the bubble initiation temperature as the short-term hot spot temperature threshold of the transformer winding.

[0038] According to the Chinese national standard GB / T 1094.7-2008, the IEEE Standard C57.91-2011, and the IEC standard, the reference temperature for normal transformer aging is 98°C for non-thermally modified paper and 110°C for thermally modified paper. GB / T 1094.7-2008, IEEE Standard C57.91-2011, and the IEC standard all clearly state that rising temperatures can cause moisture to separate out from transformer insulation paper, forming bubbles. Therefore, determining the bubble initiation temperature is crucial to predict and prevent bubble formation in transformer oil due to excessive temperatures. GB / T 1094.7-2008, the IEC, and the IEEE standards allow for the calculation of the temperature threshold that may lead to bubble formation under specific conditions. This temperature threshold is called the bubble initiation temperature. Research has found that when the moisture content of the paper is below 4%, the bubble initiation temperature of oil-paper insulation typically exceeds 110°C.

[0039] The IEC standard specifies the calculation formula for the bubble initiation temperature, while the IEEE Standard C57.91-2011 recommends the calculation formula for the bubble initiation temperature, but the same formula is used in both standards.

[0040] (6) Where, P is the total pressure inside the oil tank; is the gas content in the oil, %; and W is the water content in the oil, %.

[0041] A correction formula is proposed to solve the problem of the existence of the constant in formula (6), as shown in formula (7), and a more accurate bubble initiation temperature prediction model is obtained: (7) The aging of insulating paper is usually defined and evaluated by its degree of polymerization value. The calculation of the bubble initiation temperature is not only related to the moisture content and gas content, but also affected by the aging state of the paper insulation. The decrease in the degree of polymerization of aged paper insulation may lead to a decrease in the ability of moisture to bind to the paper insulation, which in turn affects the distribution and state of moisture in the paper insulation, and ultimately affects the value of the bubble initiation temperature. Although Equation (6) provides a reference for the calculation of the bubble initiation temperature, the model needs further research to include more variables and conditions, so as to provide a more comprehensive and accurate safety limit for the operating temperature of the transformer. By considering the degree of polymerization value of the insulating paper, the bubble initiation temperature of the insulation system under different aging states can be more accurately predicted, providing more accurate data for the maintenance and evaluation of the transformer.

[0042] Experimental testing revealed the moisture distribution equilibrium of non-thermally modified insulating paper at varying degrees of aging (measured by degree of polymerization (DP)) at various temperatures and constant insulating oil moisture content. The data is shown in Figure 6. This paper analyzes this experimental data and optimizes the bubble initiation temperature prediction model based on the Fessler calculation model for oil-paper moisture balance associated with insulating paper aging.

[0043] The Fessler model is a classic mathematical model used to describe the moisture balance state in oil-paper insulation systems. Its core lies in establishing a quantitative relationship between the moisture content in the insulation paper, temperature, and the water partial pressure in the insulating oil. Fessler proposed an oil-paper insulation moisture balance model and calculation formula as follows: (8) Where: A, B, n is the model constant; W is the moisture content in the insulating paper; p is the partial pressure of water in insulating oil; T For temperature.

[0044] Transforming formula (8), the formula of the embodiment of the calculation model of the short-term hot spot temperature threshold is obtained as follows: (9) in, P is the total pressure inside the tank, W is the moisture content of the paper, A is a constant parameter related to the degree of polymerization of oil paper, B、n It is a constant parameter calculated based on historical data.

[0045] The data in Figure 6 were fitted using formula (9) to obtain the values ​​of various parameters, among which A The values ​​are shown below. It can be seen that under different DP A The value decreases with decreasing degree of polymerization.

[0046] Table 1 Data fitting results

[0047] Will A The value is used as the dependent variable and 1 / DP is used as the independent variable for analysis. The fitting result is A The model between the value and the degree of polymerization is finally fitted with the exponential fitting result as shown, and the parameters A The relationship with the degree of polymerization DP is as follows: (10) FIG7 is a schematic diagram of parameter fitting under different polymerization degrees and moisture contents provided by an embodiment of the present invention. In conjunction with FIG7 , in a possible embodiment, nB The value is 7064.8, n The value of is 1.4959. A The fitting expression of the degree of polymerization and n and B Substituting the value of into formula (9), we get the improved bubble starting temperature estimation formula: (11) It can be seen that knowing the total pressure inside the tank P , Paper moisture content W The oil-paper polymerization degree DP can be used to evaluate the bubble initiation temperature. The polymerization degree can be estimated by combining Equation (1), and the pressure and paper moisture content can also be obtained. The data of the insulation paper with a polymerization degree of 1200 is compared with the model. The results are shown in Figure 8. It can be seen that the prediction results of the two models are basically consistent. Because the short-term load capacity of the transformer depends on the constraint of the bubble initiation temperature on the winding hotspot temperature under the current operating conditions, the bubble initiation temperature under different aging conditions is calculated by this model, and the threshold of the winding short-term hotspot temperature can be obtained.

[0048] Step 4: setting a winding hot spot temperature threshold of the transformer to be evaluated based on the long-term hot spot temperature threshold and the short-term hot spot temperature threshold of the transformer to be evaluated.

[0049] Under normal operating conditions, a transformer's long-term load capacity is primarily determined by the impact of thermal aging on insulation performance, while its short-term load capacity depends on the constraints imposed by the bubble initiation temperature on the winding hotspot temperature under current operating conditions. This invention proposes a method for calculating the short-term and long-term hotspot temperature thresholds for the winding. To ensure safe temperature operation of the transformer, the minimum of these two values ​​is used as the hotspot temperature threshold for the transformer winding. The specific implementation method is shown in Figure 9.

[0050] 9 , in a possible embodiment, step 4 includes: selecting a minimum value between a long-term hotspot temperature threshold and a short-term hotspot temperature threshold as the winding hotspot temperature threshold of the transformer to be evaluated.

[0051] Example 2 Example 2 provided by the present invention is an embodiment of a system for determining the hotspot temperature threshold of an oil-immersed power transformer winding provided by the present invention. Combined with Figure 1, it can be seen that the embodiment of the temperature threshold determination system includes: a remaining life assessment model construction module, a long-term hotspot temperature threshold determination module, a short-term hotspot temperature threshold determination module and a hotspot temperature threshold determination module.

[0052] The remaining life assessment model construction module is used to construct a remaining life assessment model for the transformer insulation system based on historical data. The remaining life assessment model is a function of the relationship between the logarithm of the furfural content obtained by decomposing the insulating paper in the transformer insulation system and the operating time of the transformer.

[0053] In one possible embodiment, the remaining life assessment model is: ; Among them, fur is the furfural content, t is the operating time of the transformer, and a, b, and c are constant parameters calculated based on historical data.

[0054] In a possible embodiment, the remaining life assessment model is: .

[0055] Among them, fur is the furfural content, t is the operating time of the transformer.

[0056] The long-term hot spot temperature threshold determination module is used to calculate the apparent life of the transformer to be evaluated based on the remaining life assessment model, and to construct a calculation model for the long-term hot spot temperature threshold of the transformer to be evaluated based on the apparent life, actual operating time and total design life of the transformer to be evaluated.

[0057] In a possible embodiment, the calculation model of the long-term hotspot temperature threshold is: .

[0058] in, is the long-term hotspot temperature threshold, is the total design life of the transformer, is the operating time of the transformer, is the estimated apparent life of the transformer.

[0059] The short-term hot spot temperature threshold determination module is used to determine the bubble initiation temperature of bubbles precipitated from the insulating paper based on the total pressure inside the oil tank of the transformer to be evaluated, the moisture content of the paper, and the oil-paper polymerization degree, and use the bubble initiation temperature as the short-term hot spot temperature threshold of the transformer winding.

[0060] In a possible embodiment, the calculation model formula of the short-term hotspot temperature threshold is: .

[0061] in, P is the total pressure inside the tank, W is the moisture content of the paper, A is a constant parameter related to the degree of polymerization of oil paper, B、n It is a constant parameter calculated based on historical data.

[0062] In a possible embodiment, the calculation formula of the constant parameter A related to the polymerization degree of oil paper is: , DP is the degree of polymerization of oil paper.

[0063] nB The value is 7064.8, n The value of is 1.4959.

[0064] In a possible embodiment, the calculation formula of the degree of polymerization DP of oil paper is: ; fur is the furfural content, DP is the degree of polymerization of oil paper.

[0065] The hotspot temperature threshold determination module is used to set the winding hotspot temperature threshold of the transformer to be evaluated based on the long-term hotspot temperature threshold and the short-term hotspot temperature threshold of the transformer to be evaluated.

[0066] In a possible embodiment, the process of the short-term hot spot temperature threshold determination module setting the winding hot spot temperature threshold of the transformer to be evaluated based on the long-term hot spot temperature threshold and the short-term hot spot temperature threshold of the transformer to be evaluated includes: The minimum value of the long-term hot spot temperature threshold and the short-term hot spot temperature threshold is selected as the winding hot spot temperature threshold of the transformer to be evaluated.

[0067] It can be understood that the oil-immersed power transformer winding hotspot temperature threshold determination system provided by the present invention corresponds to the oil-immersed power transformer winding hotspot temperature threshold determination method provided in the aforementioned embodiments. The relevant technical features of the oil-immersed power transformer winding hotspot temperature threshold determination system can refer to the relevant technical features of the oil-immersed power transformer winding hotspot temperature threshold determination method, which will not be repeated here.

[0068] Embodiments of the present invention provide a method and system for determining the hotspot temperature threshold of an oil-immersed power transformer winding. This system, combined with historical transformer operating data, establishes a remaining life assessment model for the transformer insulation system. This system can be used to determine the transformer's accelerated, equivalent, or delayed aging status, and to determine the transformer's long-term hotspot temperature threshold for the winding. Considering the importance of moisture balance in the oil-paper insulation system, a bubble initiation temperature assessment model for comprehensive thermal aging conditions is constructed. An improved bubble initiation temperature calculation formula is used to reflect changes in the degree of polymerization of the insulating paper's cellulose, determining the transformer's short-term hotspot temperature threshold for the winding.

[0069] The embodiments of the present invention provide a method, system, electronic device and storage medium for determining the hotspot temperature threshold of the winding of an oil-immersed power transformer. First, a remaining life assessment model of the transformer insulation system is established to determine the long-term winding hotspot temperature threshold of the transformer. Then, by improving the bubble starting temperature calculation formula to reflect the change in the degree of polymerization of the insulating paper cellulose, the short-term winding hotspot temperature threshold of the transformer is determined. Finally, a differentiated hotspot temperature threshold determination method is obtained. These set temperature thresholds not only reflect the current health status of the transformer, but also incorporate predictions of its future life and possible risk factors. On this basis, the load capacity of the transformer is optimized and the safety margin is determined, which can ensure that the transformer can achieve maximum operating efficiency while ensuring safety.

[0070] It should be noted that, in the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0071] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0072] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded computer, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0073] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0074] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0075] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0076] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for determining a hot spot temperature threshold of an oil-immersed power transformer winding, characterized in that: The temperature threshold determination method includes: Constructing a remaining life assessment model for a transformer insulation system based on historical data, wherein the remaining life assessment model is a function of the logarithm of the furfural content obtained by decomposing insulating paper in the transformer insulation system and the operating time of the transformer; Calculating the apparent life of the transformer to be evaluated based on the remaining life evaluation model, and constructing a calculation model for the long-term hot spot temperature threshold of the transformer to be evaluated based on the apparent life, actual operating time and total design life of the transformer to be evaluated; Determine the bubble initiation temperature of bubbles precipitated from the insulating paper based on the total internal pressure of the oil tank of the transformer to be evaluated, the moisture content of the paper, and the oil-paper polymerization degree, and use the bubble initiation temperature as the short-term hot spot temperature threshold of the transformer winding; The long-term hot spot temperature threshold of the transformer to be evaluated is calculated based on the calculation model, and the winding hot spot temperature threshold of the transformer to be evaluated is set based on the long-term hot spot temperature threshold and the short-term hot spot temperature threshold of the transformer to be evaluated.

2. The method for determining a temperature threshold according to claim 1, wherein: The remaining life assessment model is ; Among them, fur is the furfural content, t is the operating time of the transformer, and a, b, and c are constant parameters calculated based on historical data.

3. The method for determining a temperature threshold according to claim 1, wherein: The remaining life assessment model is ; Among them, fur is the furfural content, t is the operating time of the transformer.

4. The method for determining a temperature threshold according to claim 1, wherein: The calculation model of the long-term hotspot temperature threshold is: ;in, is the long-term hotspot temperature threshold, is the total design life of the transformer, is the operating time of the transformer, is the estimated apparent life of the transformer.

5. The method for determining a temperature threshold according to claim 1, wherein: The calculation model formula of the short-term hot spot temperature threshold is: ； in, P is the total pressure inside the tank, W is the moisture content of the paper, A is a constant parameter related to the degree of polymerization of oil paper, B、n It is a constant parameter calculated based on historical data.

6. The method for determining a temperature threshold according to claim 5, wherein: The calculation formula of the constant parameter A related to the polymerization degree of the oil paper is: , DP is the degree of polymerization of oil paper; nB The value is 7064.8, n The value of is 1.4959.

7. The method for determining a temperature threshold according to claim 5 or 6, wherein: The calculation formula of the oil paper polymerization degree DP is: ; fur is the furfural content, DP is the degree of polymerization of oil paper.

8. The method for determining a temperature threshold according to claim 1, wherein: The process of setting the winding hot spot temperature threshold of the transformer to be evaluated based on the long-term hot spot temperature threshold and the short-term hot spot temperature threshold of the transformer to be evaluated includes: The minimum value of the long-term hot spot temperature threshold and the short-term hot spot temperature threshold is selected as the winding hot spot temperature threshold of the transformer to be evaluated.

9. A system for determining hot spot temperature threshold of oil-immersed power transformer windings, characterized in that: The temperature threshold determination system includes: a remaining life assessment model construction module, a long-term hotspot temperature threshold determination module, a short-term hotspot temperature threshold determination module, and a hotspot temperature threshold determination module; The remaining life assessment model construction module is used to construct a remaining life assessment model for the transformer insulation system based on historical data, wherein the remaining life assessment model is a function of the relationship between the logarithm of the furfural content obtained by decomposing the insulation paper in the transformer insulation system and the operating time of the transformer; The long-term hot spot temperature threshold determination module is used to calculate the apparent life of the transformer to be evaluated based on the remaining life assessment model, and to construct a calculation model for the long-term hot spot temperature threshold of the transformer to be evaluated based on the apparent life, actual operating time and total design life of the transformer to be evaluated; The short-term hot spot temperature threshold determination module is used to determine the bubble initiation temperature of bubbles precipitated from the insulating paper based on the total pressure inside the oil tank of the transformer to be evaluated, the moisture content of the paper, and the oil-paper polymerization degree, and use the bubble initiation temperature as the short-term hot spot temperature threshold of the transformer winding; The hotspot temperature threshold determination module is configured to set the winding hotspot temperature threshold of the transformer to be evaluated based on the long-term hotspot temperature threshold and the short-term hotspot temperature threshold of the transformer to be evaluated.

10. The temperature threshold determination system according to claim 9, characterized in that: The remaining life assessment model is ; Among them, fur is the furfural content, t is the operating time of the transformer, and a, b, and c are constant parameters calculated based on historical data.

11. The temperature threshold determination system according to claim 9, characterized in that: The remaining life assessment model is ; Among them, fur is the furfural content, t is the operating time of the transformer.

12. The temperature threshold determination system according to claim 9, characterized in that: The calculation model of the long-term hotspot temperature threshold is: ;in, is the long-term hotspot temperature threshold, is the total design life of the transformer, is the operating time of the transformer, is the estimated apparent life of the transformer.

13. The temperature threshold determination system according to claim 9, characterized in that: The calculation model formula of the short-term hot spot temperature threshold is: ； in, P is the total pressure inside the tank, W is the moisture content of the paper, A is a constant parameter related to the degree of polymerization of oil paper, B、n It is a constant parameter calculated based on historical data.

14. The temperature threshold determination system according to claim 9, characterized in that: The calculation formula of the constant parameter A related to the polymerization degree of the oil paper is: , DP is the degree of polymerization of oil paper; nB The value is 7064.8, n The value of is 1.4959.

15. The temperature threshold determination system according to claim 13 or 14, characterized in that: The calculation formula of the oil paper polymerization degree DP is: ; fur is the furfural content, DP is the degree of polymerization of oil paper.

16. The temperature threshold determination system according to claim 9, characterized in that: The process of the short-term hot spot temperature threshold determination module setting the winding hot spot temperature threshold of the transformer to be evaluated based on the long-term hot spot temperature threshold and the short-term hot spot temperature threshold of the transformer to be evaluated includes: The minimum value of the long-term hot spot temperature threshold and the short-term hot spot temperature threshold is selected as the winding hot spot temperature threshold of the transformer to be evaluated.

17. An electronic device, characterized in that: It comprises a memory and a processor, wherein the processor is used to implement the steps of the method for determining the hot spot temperature threshold of the oil-immersed power transformer winding as described in any one of claims 1 to 8 when executing the computer management program stored in the memory.

18. A computer-readable storage medium, characterized in that A computer management program is stored thereon, and when the computer management program is executed by the processor, the steps of the method for determining the hot spot temperature threshold of the oil-immersed power transformer winding are implemented as described in any one of claims 1 to 8.

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