Method for monitoring moisture, computer program, and computer-readable medium

Abstract

The invention relates to a method, in particular a computer-assisted method, for monitoring the moisture of a solid insulation assembly (I) of an electrical device (1), in particular a transformer (1) or a choke, and / or a liquid and / or gaseous insulation medium thereof which is in contact with a solid insulation assembly (I), the method having the following steps: S1) providing and / or creating a simulation model of the electrical device; and S2) carrying out a simulation of the moisture distribution in the electrical device (1), in particular in the solid insulation assembly (I) and / or in the insulation medium, using the simulation model.

Description

[0001]2024PF00306 1 Description Method for monitoring humidity, computer program and computer-readable medium The present invention relates to a method, in particular a computer-aided method, for monitoring the humidity of a fixed insulation arrangement and / or a liquid and / or gaseous insulating medium in contact with a fixed insulation arrangement of an electrical device, in particular a transformer or an inductor. The invention further relates to a computer program and a computer-readable medium. In the context of the energy transition, the operational reliability of electrical devices, for example transformers, plays an increasingly important role. At the same time, the energy transition leads to increasing load fluctuations, which can lead to increased stress on a transformer. Insulation systems of electrical devices often consist of a combination of an insulating medium, which is liquid or gaseous, and a computer program.The insulating medium can be gaseous, and a solid insulating arrangement, typically based on cellulose. Substances that arise due to the aging of the solid insulating arrangement can migrate into the insulating medium and be detected there. This allows for the monitoring of the aging of an electrical device. Humidity has a significant influence on the aging and performance of an electrical device. This refers specifically to the moisture present in the insulating medium and the solid insulating arrangement. Aging processes (2024PF00306 2) or leaks can cause the humidity level to rise over the operating life of an electrical device, such as a transformer. Simultaneously, a higher humidity level can lead to accelerated aging.Fluctuating temperatures can lead to moisture transfer within the rigid insulation assembly or between the rigid insulation assembly and the insulating medium surrounding it. For example, if the temperature in the insulating medium and / or the rigid insulation assembly drops sharply (e.g., during a load fluctuation), the water activity level in the insulating medium can increase rapidly in the short term because the rigid insulation assembly cannot absorb the moisture quickly enough. To address this problem, a sample of the insulating medium can be taken regularly and its moisture content measured. Alternatively, a suitable sensor can be installed to determine the current moisture content in the insulating medium.However, such a measurement of moisture content is always a snapshot, as the moisture content in the insulating medium always depends on the temperature distribution within the electrical device. If excessively high moisture content is detected, the insulating medium can be treated or dried to prevent dielectric problems. However, such a procedure, which is based solely on a snapshot from a sample of the insulating medium or a current measurement, cannot predict how the moisture behaves throughout the entire specified operating range of an electrical device. Therefore, a comprehensive risk assessment regarding moisture cannot be performed.2024PF00306 3 Against this background, the object of the invention is to provide an alternative method for monitoring humidity, which in particular enables a comprehensive risk assessment, preferably over the entire specified operating range of an electrical device. This object is achieved in a method of the type mentioned above, which comprises the following steps: S1) a simulation model of the electrical device is provided and / or created; S2) a simulation of the humidity distribution in the electrical device, in particular in the fixed insulation assembly and / or in the insulating medium, is carried out using the simulation model; wherein, at least in an online simulation mode, measurement data from a humidity measurement of the insulating medium and / or the fixed insulation assembly are determined and used in the simulation.The invention is based on the fundamental idea of ​​combining a simulation model, i.e., practically a digital image or digital twin of the electrical device, with a specific measured value of humidity, at least in a selectable simulation mode (online simulation mode), in order to determine, in particular, the distribution of humidity within the fixed insulation arrangement and / or within the insulating medium. This simulation model can take into account the relationships and interactions of the various processes involved in the electrical device. For example, the simulation model can consider historical operating data, current operating data, and the design of the electrical device, especially the windings (type of winding, conductor, insulation, etc.).This operating data can be relevant for determining the moisture distribution, particularly within the fixed insulation arrangement and / or the insulating medium. In this online simulation mode, the moisture content in the insulating medium is predefined, especially for a specific local area within a tank or boiler of the electrical device, e.g., in the cold oil section, as it is continuously measured by a suitable moisture sensor, particularly a capacitive moisture sensor. In other words, the simulation model or the simulation itself can be designed such that, based on this local measurement, the moisture content in the insulating medium in other areas is calculated. In a further refinement, additional operating parameters of the electrical device can be measured and used in the simulation.This design takes advantage of the fact that the humidity simulation becomes more realistic when, for example, additional operating parameters are measured and considered. An ambient temperature or the external temperature of the electrical device can be measured as an additional operating parameter. It has been shown that the external temperature can influence the conditions inside the electrical device. The temperature of the insulating medium can also be among the operating parameters that are measured. The temperature of the insulating medium determines the heat transfer, especially from a solid insulation arrangement, and thus the cooling effect. Furthermore, the temperature of the insulating medium determines the amount of moisture it can absorb. Simultaneously, a change in temperature also leads to a change in the winding clamping force of the windings of a transformer.The surface temperature of components within the electrical device can also be measured as an operating parameter. Measuring the gas composition is also possible. The current and / or voltage acting within the electrical device can also be measured as operating parameters. It has been shown that changing current loads can also affect the temperature distribution and thus the humidity. The simulation model can be designed to take into account the changing clamping force of the windings as a result of changes in temperature and / or humidity. Preferably, the simulation model or the simulation includes determining the temperature distribution as a function of current and voltage loads, ambient conditions, and / or cooling conditions of the electrical device. Determining a precise humidity distribution within the electrical device is also possible.The temporal profiles of temperature and humidity, in turn, allow conclusions to be drawn about the aging of the insulation. For example, the simulation can include the calculation of aging parameters, especially local aging parameters such as the DP values. When determining the gas composition, the proportion of carbon dioxide (CO2) can be determined in particular. It has been shown that CO2 can form, especially during the aging of the solid insulation assembly. The CO2 content can be determined at various locations within the solid insulation assembly. In a further development, the humidity distribution in the electrical device, especially in the solid insulation assembly and / or in the insulating medium, can be determined using the simulation model without using the measurement data from the humidity measurement in a predictive simulation mode.In this case, one can also speak of a hybrid simulation model. This means that, on the one hand, there is an online simulation mode in which a measured value of the humidity, particularly of the insulating medium, is used during the simulation. On the other hand, there is a predictive simulation mode that makes it possible to calculate the humidity of the fixed insulation assembly and / or the insulating medium for any given operating scenario. This allows for the determination of future humidity levels and the drawing of conclusions, especially regarding aging resistance. In other words, a digital twin is created, which makes it possible to predict which humidity levels will occur under which operating parameters or environmental conditions. From this, conclusions can be drawn about aging.Preferably, in prediction simulation mode, without using further measured operating parameters, the moisture distribution in the electrical device, particularly in the fixed insulation assembly and / or the insulating medium, is determined. In this way, it is possible to determine how the moisture is distributed in the fixed insulation assembly and / or the insulating medium under virtually any operating parameters. From this, conclusions can be drawn about the aging, especially of the fixed insulation assembly. In other words, a moisture distribution can be determined even for operating conditions that have not yet occurred in reality. This allows for a sound estimation, in particular, of the aging resistance and thus also of the probability of failure.According to a preferred embodiment, a moisture distribution is determined by measuring local moisture at several different locations within the fixed insulation assembly and / or in the insulating medium. In this way, a location-dependent moisture distribution can be determined. In a further embodiment, the simulation model can take into account the structural design of the electrical device. In other words, the simulation model can consider the specific structural design, i.e., the design and dimensioning of the individual components, for example, a core, a winding assembly, a compression ring, a mounting plate, and a winding cylinder, as well as a tank containing insulating medium and surrounding the other components. The winding assembly can comprise at least one high-voltage winding and at least one low-voltage winding.Based on the simulation of the moisture distribution, a permissible limit value for moisture can be determined. In particular, depending on the limit value, the moisture level can preferably be categorized at various points. This can be done, for example, according to a traffic light system (red, yellow, green). It is also possible that, as a result of the simulation, maintenance and / or service instructions based on the simulated moisture distribution are issued. In particular, this can include a notification as to whether the insulating medium needs to be treated or dried. Preferably, the limit value for moisture covers the entire specified operating range of the electrical device. This makes it possible to determine whether a limit value is exceeded under possible operating conditions and thus whether there is a moisture risk. The simulation model or the simulation itself can be multi-stage.It comprises several submodels. It can calculate the following quantities, particularly depending on the current and voltage load: - the heat flow and temperature of components or areas of the electrical device, especially the insulating medium in an upper and a lower area of ​​a tank or the coolers, core temperatures, temperatures of winding sections as well as of local hotspots and local oil temperatures in the windings. - The oil flow in the electrical device or in the components of the electrical device, for example in the core, in the windings, in the tank, which is determined by the hydraulic resistance, the buoyancy force and optionally the pump pressure. - The moisture exchange between the solid insulation arrangement and the liquid or...gaseous insulating medium, in particular including possible moisture exchange with the atmosphere through diffusion of moisture to the outside, in a transformer especially through the oil expansion vessel. - Calculation of a local aging parameter, in particular the degree of polymerization (DP value) of the various areas or elements of the solid insulation arrangement, taking into account the influence of moisture and oxygen, the quality of the solid insulation, in particular the cellulose quality (e.g., 2024PF00306 9 thermally non-stabilized or thermostabilized paper), and the moisture formation due to aging.- The influence of aging on the moisture absorption of the solid insulation, especially cellulose, and - the risk of blistering when the pressure of dissolved gases and moisture in the solid insulation or insulating medium exceeds the ambient pressure acting upon it, which can lead to the destruction of the device. Input variables for the simulation model can include, among others, the ambient temperatures during the operating period under consideration and the current load. Furthermore, a switch position, a cooling stage, and / or the applied voltage can be input variables for the simulation model.In a further embodiment, for the various areas of the solid insulation arrangement, taking into account the calculated local temperatures and / or calculated local aging parameters, and preferably also considering the masses of the solid insulation arrangement, quantities of at least one aging product that exists due to the aging of the solid insulation arrangement and migrates into the insulating medium can be calculated, or such values ​​or data can be considered. Preferably, the calculated quantities of aging products are used to distinguish between a normal and a defective state of the electrical device. In a further embodiment, the simulation model can be designed as a network model. Operational simulation can be performed for a simulation period of several hours, months, or years.2024PF00306 10 Specifically, the simulation model can represent the solid insulation arrangement as comprising several layers, each with a specific thickness. The simulation model can depict diffusion between these layers. Furthermore, an outer layer can be represented as an interface in the simulation model, in contact with the liquid and / or gaseous insulating medium. Here, too, processes such as heat transfer, moisture transfer, and other diffusion processes or general material exchange can occur, which can be represented accordingly in the simulation model. In particular, a transition thickness can be defined here, which assumes a constant value for the simulation model. Specifically, this transition thickness can be at least 0.02 mm and / or at most 0.08 mm. Preferably, this transition thickness is 0.0375 mm.Depending on the water exchange rate of the material, different transition thicknesses can also be used. The simulation model can be designed to determine the water exchange rate (diffusion rates), particularly between different layers of the solid insulation arrangement and / or between the solid insulation arrangement and the insulating medium. Specific factors can be used for this purpose, as described, for example, in: J. Raith, M. Scala and C. Bonini, “Simulation of Long-Term Transformer Operation with a Dynamic Thermal, Moisture and Aging Model”, 5th International Colloquium Transformer Research and Asset Management, Pages 67–83, Opatija, Croatia, 2019. The simulation model can be designed such that a solid insulation arrangement, consisting of paper and / or pressboard, is divided into at least 8 and / or at most 100 layers.Preferably, the insulation arrangement is divided into different layers according to its thickness. For example, an insulation arrangement in the low-voltage range can be 0.28 mm thick and preferably divided into 10 layers, whereas a 1.05 mm thick solid insulation arrangement for high voltages can be divided into approximately 40 layers. Winding cylinders, which can also form part of the solid insulation arrangement, can, for example, have a thickness of 6 mm and can be divided into 80 layers in the simulation model. According to a preferred embodiment, the method according to the invention further includes an aging assessment and, in particular, condition monitoring based on a determined (simulated) moisture distribution.Specifically, the aging assessment can include an aging simulation for different areas of the electrical device, in particular for different areas of the solid insulation assembly and / or for different areas of the volume occupied by the insulating medium. In particular, local temperatures can be calculated, taking these temperatures into account, and optionally taking into account other aging-determining factors, in particular the oxygen content of the insulating medium and / or the solid insulation assembly, and / or the humidity of the insulating medium and / or the solid insulation assembly, local aging parameters, in particular local DP numbers, are calculated for different areas of the solid insulation assembly.In particular, by considering aging through the calculation of a local DP number, which generally cannot be verified by direct measurement, a precise representation of the condition, especially of the solid insulation arrangement, is obtained. In other words, a thermo-hydraulic aging model can be provided or used to determine aging products in particular. Specifically, quantities of 2-FAL and / or CO₂ + CO can be calculated as aging product quantities. In other words, the aging assessment can include the calculation of such quantities of aging products. These quantities represent particularly suitable "aging markers" that can be considered within the framework of the method according to the invention. On the other hand, these quantities can also be readily measured in an insulating medium.As a rule, 2-FAL becomes visible primarily when significant aging has already occurred, while CO2+CO is formed from the outset. When calculating the amounts of aging products for the various locations or areas of the solid insulation assembly, especially different parts thereof, it is advantageous to consider the masses of the various areas or parts of the insulation assembly. This is because the aging products transferring from the solid insulation assembly or parts thereof into the insulating medium will generally depend on the (respective) mass. The insulating medium advantageously has both insulating and cooling properties; in other words, it serves primarily for both insulation and cooling. A thermo-hydraulic aging model can be used to assess the aging; this model is preferably multi-stage or may include several sub-models. The aging model, or...The aging simulation can include the same calculations as the previously described simulation of the moisture distribution. 2024PF00306 13 The abbreviation "DP" in the DP number stands, as is generally known, for "Degree of Polymerization". It is specifically a measure of the decreasing length of cellulose molecules due to thermal aging, which impairs mechanical strength and can lead to an operational risk. The DP number indicates the number of basic molecular units in a cellulose chain, which is formed by polymerization, the joining of the basic molecule. New cellulose has DP values ​​above 1000, while chemical decomposition causes the chains to break into shorter units, reducing their mechanical strength. At DP values ​​below 200, the mechanical strength, such as...The tensile strength is significantly deteriorated, falling well below 50% compared to the initial state. This could jeopardize the safe operation of a transformer, particularly in the event of short circuits in the network, which can lead to high currents and thus significant forces or vibrations, at least temporarily. For the optional calculation of DP values ​​as aging parameters, especially the calculation of the decreasing DP value due to aging, at least one formula is preferably used which takes the initial state DP as an influencing factor. StartThe thermo-hydraulic aging model comprises the time duration t, the temperature ^h of the solid insulation arrangement, in particular cellulose, in the hotspot, and a material property A of the cellulose, which depends on H₂O and O₂ as well as the cellulose quality. For papers, a second cellulose quality is a thermostabilized quality with reduced thermal aging at high temperatures. In this regard, reference is also made to the standard IEC 60076-7:2018 "Loading guide for mineral-oil-immersed power transformers", 2018, and in particular to page 42 with equation A.1 and Table A.1 on page 43, whose parameters easily take into account the temperature, humidity, cellulose quality, and oxygen influence. 2024PF00306 14 The thermo-hydraulic aging model used according to the invention can comprise at least one such equation.Alternatively or additionally, it may be provided that the following equation is used for the optional calculation of local DP numbers: It contains M t a humidity factor, p(T) a temperature function and O t An oxygen factor, which strongly influences the DP drop according to the equation. For the temperature function, the following is preferred: Non-thermostabilized paper and cellulose ^^^^^^ ൌ ^^,^^^^^^^^^^^^ ⋅ ^^^^,^^^^^^^^^^^^⋅^^ ^^^^^^ ൌ ^^, ^^^^^^^^^^^^ ⋅ ^^^^,^^^^^^^^^^^^⋅^^ For the oxygen factor, the following equation is used in a further advantageous embodiment: ^^^^^,^^^^^^^ ൌ ^^ ^ ^^^^^ െ ^^^ ∙ ^^^^^^^^⁄ ^^^^^^^^ , with O sat =37000 ppm (< 1,000 m sea level, in mineral oil) and O ppmequal to the oxygen concentration present in the transformer. Without measurement, two possibilities can be assumed in particular: - an open system with oxygen supplied from the air, - a closed system with little oxygen. 2024PF00306 15 Preferably, the electrical device is designed as a closed system, in particular by a system or device with an airtight seal. The thermo-hydraulic aging model is suitably designed to calculate both the steady-state and the transient behavior of the following quantities, in particular based on the load: - The heat flow and the temperature of components or areas of the electrical device (in the case of a transformer, in particular the insulating medium, such as oil, in the upper and lower areas of the tank or...The cooler, core temperatures, temperatures of winding sections, as well as local hot spots and local oil temperatures in the windings). - The oil flow in the electrical device or in its components (in the case of a transformer, in the core, the windings, in the tank, etc.), which is determined by the hydraulic resistance, the buoyancy force, and optionally the pump pressure. The aging model is further preferably designed to calculate the following quantities with respect to moisture and aging behavior: - The moisture exchange between solid insulation and liquid or gaseous insulating medium, preferably including any possible moisture exchange with the atmosphere through diffusion of moisture to the outside, in a transformer, in particular through the oil conservator. - Calculation of the local aging quantity, in particular the degree of polymerization (DP value) of the various areas or...Cellulose elements taking into account: 2024PF00306 16 o the influence of moisture and oxygen o the quality of the solid insulation, in particular the cellulose quality (e.g., thermally unstabilized or thermally upgraded paper) o moisture formation due to aging itself - influence of aging (DP value) on the moisture absorption of the solid insulation, in particular cellulose, and - risk of blistering if the pressure of dissolved gases and moisture in the solid insulation or insulating medium exceeds the ambient pressure acting upon it. This can lead to the destruction of the device.In particular, an extended version of the thermo-hydraulic aging model disclosed in the article “Simulation of long-term transformer operation with a dynamic thermal, moisture and aging model”, 5th International Colloquium on Transformer Research and Asset Management, October 2018, Opatija, Croatia (further publication of the article: 5th International Colloquium on Transformer Research and Asset Management, Lecture Notes in Electrical Engineering, vol 671, Springer, Singapore, 2020, https: / / doi.org / 10.1007 / 978-981-15-5600-5_17) can be used. This simulation model can be extended to additionally enable the calculation of aging product quantities.This includes substances that arise due to the aging of the solid insulation assembly (2-FAL and / or CO2+CO) and migrate into the insulating medium. As they spread through the insulating medium, they reach an equilibrium state within the overall system, resulting in a uniform value for the aging product dissolved in the insulating medium, the aging marker (2-FAL, CO2+CO, ...). Input variables for the thermo-hydraulic aging model can include, for example, the ambient temperatures during the operating period under consideration and the load. In a suitable embodiment, the switch position, cooling stage, and / or the applied voltage also constitute input variables for the thermo-hydraulic aging model.It may be provided that, when calculating the amounts of aging products for the various areas of the solid insulation arrangement, the equilibrium state of the respective aging product(s) between the solid insulation arrangement and the insulating medium is taken into account, preferably considering the increase of the respective aging product(s) due to aging and the mixing of the respective aging product(s) in the entire insulating medium. This is particularly important to determine the absorption of at least one aging product into the insulating medium. In other words, the calculation of the amounts of aging products can be carried out in local areas or parts of the solid insulation arrangement where the equilibrium state of the substance or product is determined.The calculation of the local equilibrium between the local solid insulation arrangement and the local insulating medium takes into account the increase of the respective aging product(s) due to aging and the mixing of the respective aging product(s) within the insulating medium, particularly the entire insulating medium. Thus, an equilibrium process can be considered, especially the mixing / redistribution due to transport within the insulating medium. The calculation of the local equilibrium between the local solid insulation arrangement 2024PF00306 18 or areas / locations thereof and the local insulating medium is determined in particular by two effects: the increase of the respective aging product(s) due to aging and the change due to transport within the liquid or gaseous insulating medium. Instead of the iterative change due to transport, a simplification results from an immediate transfer to the entire insulating medium, which, for example,The specific aging product value absorbed in the hotspot does not necessarily correspond to the high specific production rate of the aging product; conversely, areas / locations / parts with low aging may receive elevated aging values ​​than their actual aging would suggest. An integral value can be derived from the calculation of local aging product equilibria. The aging model is preferably designed accordingly. Advantageously, the equilibrium state is at least roughly known and taken into account. In the simplest approach, a constant, temperature-independent ratio can be used for the distribution between solid insulation and insulating medium, assuming that the vapor pressure in the solid insulation and insulating medium has the same temperature dependence, so that their ratio is temperature-independent. This simplified assumption does not hold true for the vapor pressure of water dissolved in cellulose and oil.There, moisture shifts into the insulating medium as the temperature rises. The thermo-hydraulic aging model used is, or will be, appropriately designed accordingly. Alternatively or additionally, when calculating the quantities of aging products, a redistribution of the aging products from areas with a higher generation rate to areas with a lower generation rate, particularly via transport through the insulating medium, can be taken into account. Here, too, the thermo-hydraulic aging model used is, or will be, appropriately designed accordingly. This effect depends in particular on the specific solubility properties of the respective aging product(s) in the different areas of the insulation arrangement and the insulating medium.In a further preferred embodiment, the calculation of the aging product quantities is carried out using at least one formula that is or was developed based on measured data, in particular on measured data that link a decreasing DP number with an increasing quantity of at least one aging product, preferably CO2+CO and / or 2-FAL. 2-FAL stands for 2-furfural, a compound from the family of cellulose decomposition products that is particularly informative in practice. In other words, it can be, in particular, one or more formulas that are or were developed using measured data that link the aging parameters of a solid insulation, in particular DP numbers, with quantities of at least one aging product that passes into an associated insulating medium. The DP number decreases with increasing age, and the quantity of the aging product(s) increases.It should be noted that other aging products, such as methanol, also exist. However, these are generally unstable and decompose further. Using these unstable substances would therefore increase the level of complexity. In all cases, however, CO2 + CO is ultimately found. Generally, the proportion of CO, which indicates oxygen deficiency during the decomposition process 2024PF00306 20, depends on the decomposition conditions, such as temperature and the rate of temperature rise. Furthermore, the solubility of CO in oil is worse than that of CO2. For measurement purposes, CO2 and CO are expediently measured separately. As a purely illustrative example, consider a real electrical device, such as a transformer with an oil-filled tank and cellulose-based solid insulation.Using a representative measurement setup, the DP values ​​of the solid insulation (arrangement) as well as quantities of migrated aging products, such as CO2+CO and / or 2-FAL, in the oil are measured, particularly at several time intervals. Corresponding measurement data can, for example, be plotted in a graph, and at least one corresponding fit function can be determined, which can then be incorporated into the simulation model as at least one formula. Such measurement data can be collected specifically for the creation of the simulation model. Alternatively or additionally, existing measurement data can be used. For example, the article "Diagnosis of Thermal Degradation for Thermally Upgraded Paper in Mineral Oil" by Naoki Yamagata et al., 2008 International Conference on Condition Monitoring and Diagnosis, Beijing, China, April 21-24, 2008, is referenced.Figure 8 shows a graph in which the (mean) DP number (as a percentage of the initial value) is plotted against the amount of CO2+CO (ml / g) that passes into the oil for two different types of paper. Papier) is plotted. The corresponding fit lines are also shown. Accordingly, laboratory measurement results are available for a correlation between "CO2+CO production per gram of paper" and the DP number. These are measurements based on a single mass at a single temperature (single-mass model). This is insufficient for an electrical device such as a 2024PF00306 21 transformer. In this embodiment of the present invention, these measurement results are incorporated into a network model to describe the complexity of an electrical device such as a transformer (multi-mass model, transient processes). For a correlation between the DP number and 2-FAL, recorded in the insulating medium, e.g., oil, a modified version, in particular at least one modified equation, of the so-called "De Pablo model" can be used. The main equation of this model is given by De Pablo: [2FAL(^g / g paper)] = ((10 6 *((DP0 / DP t)-1)) / 162*DP0)*96*0.3*1.2 Where DP0 is the initial DP number, DP t the DP number at any given time during aging, “g paper” is the insulation mass, 162 the molecular weight of glucose units, 96 the molecular weight of furfural, 10 6The correction factor from g to ^g, 0.3 is the reaction yield and 1.2 is the furfural absorption correction of the solid insulation. Regarding the “De Pablo model”, reference is also made to the CIGRE reference paper “The Condition of Solid Transformer Insulation at End-of-Life”, CIGRE ELECTRA No. 321, April 2022, by Christoph Krause et al., in particular to page 4 and equations (1) to (3) therein, along with the accompanying explanations. In a preferred embodiment of the inventive method, the above De Pablo equation (corresponding to equation (3) on page 4 of the aforementioned CIGRE reference paper) is used, but without the factor 1.2 at the end, i.e., [2FAL(^g / g paper)] = ((10 6 * - to calculate quantities of 2-FAL. This is because the factor 1.2, lacking transformer-specific information, represents a general conversion to the DP value in the hotspot. The electrical device can be designed such that the insulating medium comprises or is surrounded by an oil. The solid insulation arrangement can comprise cellulose, in particular paper and / or pressboard, or be provided by cellulose, in particular paper and / or pressboard. In a further embodiment, the electrical device can comprise a tank filled with the insulating medium, in which components of the electrical device are housed. Preferably, one or more of the components are provided with the solid insulation arrangement, in particular wrapped with the solid insulation arrangement or parts thereof. The solid insulation arrangement can be multi-part. In step S2, the different areas of the solid insulation arrangements can be different parts of theThe fixed insulation arrangement comprises or is provided by it. In a further embodiment, different components of the electrical device can be assigned different parts of the fixed insulation arrangement. Preferably, different components of the electrical device are provided with different parts of the fixed insulation arrangement, in particular wrapped. 2024PF00306 23 The problem underlying the invention is further solved by a computer program comprising program code means which, when the program is executed on at least one computer, cause the at least one computer to carry out the steps of the method as described above. Furthermore, the problem underlying the invention is solved by a computer-readable medium comprising instructions which, when executed on at least one computer, cause at least one computer to carry out the steps of the method as described above. In theThe computer-readable medium can be, for example, a CD-ROM, a DVD, or a USB or flash memory device. It should be noted that a computer-readable medium is not exclusively a physical medium, but can also be, for example, in the form of a data stream and / or a signal representing a data stream. Further features and advantages of the present invention will become clear with reference to the dependent claims and the following description, with reference to the accompanying drawing. In the drawing: Figure 1 shows a purely schematic partial representation of an electrical device designed as a transformer; Figure 2 shows a purely schematic representation of a simulation model for the transformer from Figure 1; Figure 3 shows two graphs, each showing the calculated diffusion times for (a) 3 mm thick pressboard material and (b) 0.15 mm thick winding paper.Figure 4 shows three graphs with the simulation results over a period of 360 days concerning the humidity, considering only the winding paper of the solid insulation arrangement; Figure 5 shows three graphs with the simulation results over a period of 360 days concerning the humidity, considering both the winding paper and the winding cylinders of the solid insulation arrangement; Figure 6 shows a total of four graphs with the simulated and measured temperatures and water activities in the mineral oil for a period of 98 days and a 7-day excerpt; and Figure 7 shows two graphs with a prediction of the water activity (A) under normal load and (B) under emergency load. Figure 1 shows, to illustrate the method according to the invention, a partial representation of an electrical device provided by a transformer 1. The transformer 1 comprises a tank 2, which is only partially shown in the figure, inin which several components of the transformer 1 are arranged. These include, among others, a core 3, a winding assembly 4, a compression ring 5, a mounting plate 6, and a winding cylinder 7, as shown in Figure 1. The transformer 1 has a fixed insulation assembly I, which consists primarily of pressboard and paper, i.e., cellulose, and is designed in multiple parts. As an example, the widely used core design of a power transformer was chosen, the active part of which comprises the winding assembly 4 extending around the iron core, the conductors of which are insulated by pressboard elements (cellulose), with the conductors typically wrapped with paper (cellulose). On the one hand, the pressboard elements and paper belonging to the winding assembly 4 are components of the fixed insulation assembly I. The same applies to the compression ring 5, the mounting plate 6, and the winding cylinders 7, each of which consists of one or more pressboard elements.The block element designated with reference numeral 8 in Figure 1 is representative of further areas or parts of the insulation assembly I that may be present or are present in this case, in particular further cellulose, and also of further components of the transformer 1 outside the active part. All paper or pressboard parts located on or attached to the various components together form the solid insulation assembly I. Figure 9 indicates a void, or in other words, a recess or hole, in tank 2. Also shown schematically are a preservative, or in other words, an oil expansion vessel 10, a dehumidifier 11, and a cooler 12. The void 9 lies between the cooler 12 and the remaining area of ​​tank 2. Expansion vessels are available in an open design, which allows air to enter. However, the trend towards closed systems—e.g., using rubber membranes—is increasing in order to prevent the entry of air.to prevent aging-accelerating oxygen. In the illustrated embodiment, tank 2 is further filled with a liquid insulating medium, which is a mineral oil 13. In this case, one can also speak of an oil-insulated transformer 1. The solid insulation assembly I and the mineral oil 13 together form an insulation system of the transformer 1. The solid insulation assembly I is in contact with the insulating oil 13. Substances that arise due to the aging of the solid insulation assembly I can pass into the insulating medium 13 and be detected there. These are also referred to as so-called aging markers. Examples of such aging markers include CO2 + CO and / or 2FAL. The oil flow is represented in Figure 1 by simple arrows, which are marked with the reference numeral 14 as an example. Double arrows 15 further indicate, purely schematically, the moisture exchange betweenThe transformer 1 comprises a fixed insulation arrangement I and a liquid insulating medium 13. The individual windings of the winding arrangement 4 are held on the winding cylinder with a defined clamping force or wound onto it. The transformer 1 also includes a moisture sensor 16, in particular a capacitive one, which measures the moisture content, i.e., the water content or water activity, in the mineral oil 13. The moisture content of the fixed insulation arrangement I and the mineral oil 13 can be determined under various operating parameters in different simulation modes using the inventive method. For this purpose, a simulation model of the transformer 1 is provided. Furthermore, the moisture content in the mineral oil 13 is continuously determined by the capacitive moisture sensor 16 as needed. In an online simulation mode, the measurement data from this moisture measurement are used in a simulation using the simulation model.The simulation determines the moisture distribution in the transformer 1, particularly in the fixed insulation assembly I and in the mineral oil 13, which acts as the insulating medium. The simulation model, implemented here as a network model, determines the moisture at various points. Furthermore, it considers the design of the individual components of the transformer 1, especially the tank 2, the core 3, the winding assembly 4, the compression ring 5, the mounting plate 6, and the winding cylinder 7, as well as the fixed insulation assembly I. In a so-called predictive simulation mode, the moisture distribution can be simulated without relying on the measured values ​​of the capacitive moisture sensor 16. This allows operating ranges, such as voltage and current loads, temperatures, pressure conditions, or other environmental conditions, to be simulated during normal operation.not occur, but still remain within the specified operating range. This allows for a comprehensive prediction of the moisture distribution as a function of various input parameters, such as temperatures. The moisture distribution obtained through the simulation, particularly in the solid insulation assembly I and / or the mineral oil 13, can be used to determine the aging, especially of the solid insulation assembly. A thermo-hydraulic aging model can be used for this purpose. This allows the aging of the insulation assembly and / or the mineral oil 13 to be directly inferred from the moisture distribution determined by simulation 2024PF00306 28. It is also possible that if certain moisture values ​​of the insulating medium, in this case the mineral oil 13, are exceeded, a notification is issued indicating that the mineral oil 13 must be processed or dried.Figure 2 schematically shows an exemplary simulation model, which has a multitude of branches and nodes representing the components of transformer 1. Nodes 17 to 19 represent the core 3, nodes 20 to 25 represent the winding arrangement 4, node 26 represents at least a large part of the mineral oil 13 in tank 2, node 27 represents the wall of tank 2, node 28 represents the press ring 5, node 29 represents the mineral oil 13 in the upper region of tank 2 and the membrane of the oil expansion vessel 10, nodes 30 to 32 depict the specific design of the oil supply to the winding arrangement 4, nodes 33 and 34 also represent the oil flow in the tank, nodes 35 to 37 refer to the cooler 12, and node 38 represents a pump for circulating the mineral oil 13. The left part of Figure 2 schematically shows a model of the fixed insulation arrangement I and, adjacent to and interacting with it, the mineral oil 13.The solid insulation arrangement I has a thickness d. moistand is divided into several layers, in this case a total of five. The four layers 39 shown on the left represent insulation layers, whereas the layer 40 adjacent to the mineral oil 13 represents a transition layer to the mineral oil 13. The thickness of this transition layer 40 is d^, in this case approximately 0.0375 mm. The arrows 41 represent the diffusion processes that take place within the individual layers 39 and via the transition layer 40 with the mineral oil 13. Water exchange factors are assigned to the individual layers for the simulation model 2024PF00306 29, which represent the diffusion of water through the layers. The water exchange factor of the four (inner) insulation layers 39 is preferably 7.5 times the water exchange factor of the transition layer 40. Figures 3 to 7 show exemplary partial results of the simulation using the simulation model as described above.Figure 3 initially shows results for the diffusion processes at the interface between the solid insulation arrangement I and the mineral oil 13. The graph on the left of Figure 3 depicts the moisture content as a function of the penetration depth into the solid insulation arrangement, which is a 3 mm thick pressboard. The respective lines correspond to the simulation results, while the individual points shown are based on actual measurements. The top line shows the depth profile after 30 days, the line below it after 15 days, the next line below that after 7 days, and the bottom line after 2 days. The graph on the right of Figure 3, which shows the results for 0.15 mm thick winding paper, indicates that the diffusion rate is not constant but appears to depend on the moisture content of the mineral oil 13.Specifically, this graph shows simulated results at the lines and measured results at the individual points shown, depending on the humidity or water content (30 ppm, 50 ppm, and 70 ppm) in the mineral oil 13. Figure 4 shows various simulation results for a simulation over a period of 360 days, assuming a constant temperature distribution, and for a configuration in which only the winding paper 2024PF00306 30 is considered as a fixed insulation arrangement. A distinction is made between the high-voltage and low-voltage windings. The simulation assumes an ambient temperature of 30 °C, resulting in an average temperature of 95 °C for both windings and a temperature of 84 °C for the mineral oil 13 in the upper part of tank 2 and 74 °C in the lower part of tank 2.The initial moisture content in each component of the insulation (fixed insulation assembly) is 0.46%, and the initial moisture content in the mineral oil 13 is 0 ppm. It can be seen that an equilibrium is reached over time, at which the water content in the mineral oil 13 is approximately 8 ppm, and a moisture content of approximately 0.4% is established across the entire paper thickness in both the high-voltage and low-voltage areas. Figure 5 shows essentially the same simulation as Figure 4, but additionally includes a winding cylinder 7 with a thickness of 6 mm, made of pressboard. A comparison with Figure 4 shows that the cylinder 7 must be included, as otherwise the simulation results would yield unrealistically high moisture values.In any case, a strong dependence of the diffusion time on the temperature, the geometry of the individual components, and the respective material (water exchange factors) is evident. To validate the simulation results under varying environmental conditions, a capacitive humidity sensor was used for comparison in a transformer in real-world operation to record the water activity in the mineral oil 13 during operation. Figure 6 shows a comparison of the simulation results with the actual measured values ​​for temperature and water activity in the mineral oil: the left side over a period of 98 days and the right side a section over a period of 7 days. The temperature distribution was calculated taking into account, and depending on, the current load, the ambient temperature, and the status of the cooler.It has been shown that the moisture content in the mineral oil 13 is relatively low during operation, in the range of 0.6% water activity. Overall, there is a good correlation between the measured and calculated results. To achieve this level of correlation, it may be necessary to increase the theoretical value for the diffusion rate or the water exchange factor, for example, by a factor of 4. Finally, Figure 7 shows that critical values ​​for water activity in the mineral oil (greater than 25%) can occur under certain ambient or operating conditions. The graph on the left in Figure 7 shows the course of the water activity starting from an average winding temperature of 95 °C and a mineral oil 13 temperature of 74 °C. The different curves represent different initial values ​​for the water activity of the mineral oil 13.If the current load is briefly reduced to zero, the water activity increases considerably. After a day without current, the transformer was reloaded. It can be seen that the oil temperature then returns to a value of approximately 74 °C, and the water activity returns to its original range. The right-hand graph in Figure 7 assumes emergency operation with a higher load, in which the average winding temperature is initially about 32 °C. After the current load is removed, it is evident that the water activity in the mineral oil 13 increases from an initial activity of approximately 16% to values ​​of approximately 28%, which can be critical for the operation of the transformer. In other words, it is shown that the water activity can almost double when the transformer 1 is stopped after a high-load operation.In other words, the results show that the significant increase in water activity depends on the initial temperature, the initial load, the existing moisture level in the mineral oil, and the geometry of the windings. Therefore, the simulation model or the method according to the invention can be used to predict critical situations with regard to moisture. For this purpose, it can take into account the measured values ​​of a moisture sensor in an online simulation mode. Based on the simulation results, conclusions can be drawn about aging and also about bubble formation in the mineral oil. Although the invention has been illustrated and described in detail by the preferred embodiment, the invention is not limited by the disclosed examples, and other variations can be derived from them by those skilled in the art without departing from the scope of protection of the invention.

Claims

2024PF00306 33 Claims 1. A method, in particular a computer-aided method, for monitoring the moisture content of a fixed insulation assembly (I) and / or a liquid and / or gaseous insulating medium of an electrical device (1), in particular a transformer (1) or a choke, which is in contact with a fixed insulation assembly (I), wherein the method comprises the following steps: S1) a simulation model of the electrical device is provided and / or created; S2) a simulation of the moisture distribution in the electrical device (1), in particular in the fixed insulation assembly (I) and / or in the insulating medium, is carried out using the simulation model; wherein, at least in an online simulation mode, measurement data from a moisture measurement of the insulating medium and / or the fixed insulation assembly (I) are determined and used in the simulation. 2.The method of claim 1, characterized in that further operating parameters of the electrical device (1) are measured and used in the simulation.

3. The method of claim 2, characterized in that the operating temperature is an ambient temperature or an external temperature of the electrical device (1) and / or a temperature of the insulating medium and / or a surface temperature of components of the electrical device (1) and / or a gas composition and / or a current and / or a voltage acting in the electrical device and / or a switch position and / or a. 2024PF00306 34 The condition of a cooling device, e.g., a fan or a pump, is / are measured.

4. Method according to one of the preceding claims, characterized in that, in a predictive simulation mode, the moisture distribution in the electrical device (1), in particular in the fixed insulation arrangement (I) and / or in the insulating medium, is determined using the simulation model without using the measurement data from the moisture measurement.

5. Method according to claim 4, characterized in that the moisture distribution in the electrical device (1), in particular in the fixed insulation arrangement (I) and / or in the insulating medium, is determined in predictive simulation mode without using any further measured operating parameters. 6.A method according to any one of the preceding claims, characterized in that a moisture distribution is determined by determining local moisture at several different locations in the fixed insulation arrangement (I) and / or in the insulating medium.

7. A method according to any one of the preceding claims, characterized in that the simulation model takes into account the design of the electrical device (1).

8. A method according to any one of the preceding claims, characterized in that, based on the simulation of the moisture distribution, a permissible limit value for the moisture is determined, which in particular covers an entire specified operating range of the electrical device. 2024PF00306 35 9. Method according to claim 8, characterized in that the moisture level is categorized, in particular at different locations, and / or that the method further comprises the output of maintenance and / or service instructions based on the simulated moisture distribution, wherein, in particular, a notification is given as to whether the insulating medium needs to be treated.

10. Method according to any of the preceding claims, characterized in that it further comprises an aging assessment and, in particular, condition monitoring based on a determined moisture distribution. 11.The method according to claim 10, characterized in that the aging assessment comprises a simulation for different areas of the electrical device (1), in particular for different areas of the fixed insulation arrangement (I) and / or for different areas of the volume occupied by the insulating medium, wherein, in particular, local temperatures are calculated, taking into account these temperatures and optionally or taking into account further aging-determining influencing factors, in particular the oxygen content of the insulating medium, local aging parameters, in particular local DP numbers, are calculated for different areas of the fixed insulation arrangement (I). 12.Method according to claim 11, characterized in that for the various areas of the solid insulation arrangement (I) taking into account the calculated local temperatures and / or the local aging parameters and preferably also taking into account masses of the solid insulation arrangements (I), quantities of at least one aging product that arises due to the aging of the solid insulation arrangement (I) are determined. 2024PF00306 36 the insulating medium passes through, are calculated, preferably using the calculated aging product quantities to distinguish between a normal and a defective state of the electrical device (1).

13. Method according to one of the preceding claims, characterized in that the simulation model is designed as a network model, and / or that a simulation of operation is carried out for a simulation period of several hours, months or years, and / or that the insulating medium comprises or is provided by an oil, and / or that the solid insulation arrangement (I) comprises or is provided by cellulose, in particular paper and / or pressboard, and / or that the electrical device comprises a tank (2) filled or fillable with the insulating medium, in which components of the electrical device (1) are arranged.wherein one or more of the components are provided with the fixed insulation arrangement (I), in particular are wrapped with the fixed insulation arrangement (I) or parts thereof, and / or that the fixed insulation arrangement (I) is multi-part and the different areas of the fixed insulation arrangement (I) comprise or are defined by different parts of the fixed insulation arrangement (I), wherein, in particular, different parts of the fixed insulation arrangement (I) are assigned to different components of the electrical device (1), wherein, preferably, different components of the electrical device (1) are provided with, in particular are wrapped with, different parts of the fixed insulation arrangement (I).

14. Computer program comprising program code means which, when the program is executed on at least one computer, cause the at least one computer to, 2024PF00306 37. To perform the steps of the method according to any one of claims 1 to 13.

15. Computer-readable medium comprising instructions which, when executed on at least one computer, cause that at least one computer to perform the steps of the method according to any one of claims 1 to 13.

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