Self-adaptive dehumidification method in cable end sealing process

Abstract

The invention relates to a self-adaptive dehumidification method in a cable end sealing process. Comprising the following steps: acquiring water absorption data of a cable material; acquiring mass change data of the cable material before and after drying; calculating a water absorption diffusion coefficient and a drying diffusion coefficient of the cable material by using a moisture diffusion model; constructing a cable structure model according to the water absorption diffusion coefficient and the drying diffusion coefficient, and simulating a diffusion dynamic change process of water invading into a cable material along with time and a dehydration dynamic change process in a vacuum drying device; and according to the simulated diffusion dynamic change process, after the cable material reaches a preset condition, the drying temperature and the drying time are adaptively selected according to the simulated dehydration dynamic change process. By simulating the diffusion dynamic change process, moisture in the cable is effectively controlled, performance reduction and damage caused by moisture are prevented, and the service life of the cable is prolonged. The optimal drying temperature and time are selected by simulating the dehydration dynamic change process, the dehumidification efficiency is improved, and the energy consumption is reduced.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of electric power engineering technology and simulation technology thereof, and in particular to an adaptive dehumidification method for a cable end sealing process. Background Art

[0002] As an important medium for power transmission and communication, cables are widely used in industries, construction, transportation, communications, etc. However, cables are often exposed to various complex environmental conditions in actual use, especially in high humidity or humid environments. Cables easily absorb moisture, resulting in a decrease in their insulation performance, thus affecting the safety and stability of power transmission.

[0003] The problem of cable moisture absorption occurs mainly because cable materials (such as polymer insulation layers) absorb moisture from the air in a high humidity environment. The intrusion of moisture can cause problems such as reduced insulation performance, reduced mechanical properties, and shortened cable life. Specifically, after moisture enters the cable insulation layer, it will change the dielectric constant and conductivity of the insulation material, thereby reducing the insulation performance of the cable and increasing the risk of leakage during power transmission; in addition, moisture will cause the insulation material to expand and plastically deform, affecting the mechanical strength and flexibility of the cable, making the cable more susceptible to damage during use; if it is in a humid environment for a long time, the cable will age faster and its service life will be greatly shortened.

[0004] At present, the dehumidification methods for cable ends mainly include heating and drying, vacuum dehumidification and chemical dehumidification. The heating and drying method evaporates the moisture in the cable by heating the cable. This method is simple and easy, but it consumes a lot of energy and requires different temperature control for cables of different materials. The vacuum dehumidification method places the cable in a vacuum environment and reduces the environmental pressure to make the moisture evaporate quickly. This method is more effective, but the equipment cost is high and the operation is complicated. The chemical dehumidification method uses hygroscopic materials (such as silica gel, molecular sieves, etc.) to absorb moisture in the cable. This method is suitable for dehumidification of small-scale cables, but the hygroscopic materials need to be replaced and handled regularly.

[0005] Although the above methods can solve the moisture absorption problem of the cable ends to a certain extent, there are many deficiencies in practical applications. For example, under different environmental temperature and humidity conditions, the moisture absorption and dehumidification characteristics of the cable are different, and a single method is difficult to adapt to all environments; in addition, the existing methods mostly rely on experience and manual adjustment, lack scientific theoretical basis and simulation model, and are difficult to achieve precise control and optimization.

[0006] Therefore, it is necessary to improve one or more problems existing in the above-mentioned related technical solutions.

[0007] It should be noted that this section is intended to provide background or context for the technical solutions of the present invention stated in the claims. The description herein is not admitted to be prior art by inclusion in this section. Summary of the invention

[0008] The object of the present invention is to provide a method for adaptively dehumidifying a cable end during sealing, thereby at least to some extent solving one or more of the above-mentioned problems caused by the limitations and defects of the related art.

[0009] In a first aspect, the present invention provides a method for adaptively dehumidifying a cable end during a sealing process, comprising:

[0010] Performing a water absorption test on the cable material to obtain water absorption rate data of the cable material;

[0011] Performing a vacuum drying test on the water-absorbed cable material to obtain quality change data of the cable material before and after drying;

[0012] Calculating the water absorption diffusion coefficient and the drying diffusion coefficient of the cable material respectively according to the water absorption rate data and the mass change data using a water diffusion model;

[0013] A cable structure model is constructed according to the water absorption diffusion coefficient and the drying diffusion coefficient, and a dynamic change process of water diffusion into the cable material over time and a dynamic change process of dehydration in a vacuum drying device are simulated;

[0014] After the cable material reaches a preset condition according to the simulated diffusion dynamic change process, the cable is dried and dehumidified, and the drying temperature and drying time are adaptively selected according to the simulated dehydration dynamic change process.

[0015] Optionally, the step of performing a water absorption test on a cable material to obtain water absorption rate data of the cable material includes:

[0016] The water absorption weight gain rate is used to characterize the water absorption characteristics of the material. The calculation formula for the water absorption weight gain rate m(t) is:

[0017]

[0018] Among them, m0 is the initial mass of the cable material, m t It is the mass of the cable material after absorbing water.

[0019] Optionally, the step of using a moisture diffusion model and calculating the water absorption diffusion coefficient and the drying diffusion coefficient of the cable material respectively according to the water absorption rate data and the mass change data includes:

[0020] The calculation model formula of the drying diffusion coefficient D during vacuum drying is:

[0021]

[0022] Where m1 is the mass of the sample after drying and dehumidification; m t -m1 is the mass reduced during vacuum drying; m t -m0 is the mass increased by the sample after absorbing water; S is the surface area of ​​the sample; V is the volume of the sample; t is the drying and heating time; d is the thickness of the sample.

[0023] Optionally, the step of using a moisture diffusion model and calculating the water absorption diffusion coefficient and the drying diffusion coefficient of the cable material respectively according to the water absorption rate data and the mass change data includes:

[0024] A moisture diffusion model of the cable material is constructed according to the water absorption rate data, and the moisture diffusion model is used to express the curve relationship between the total moisture content of the material and time; the water absorption diffusion coefficient of the cable material in the current temperature and humidity environment is calculated by the moisture diffusion model.

[0025] Optionally, the step of constructing a cable structure model according to the water absorption diffusion coefficient and the drying diffusion coefficient, and simulating the dynamic change process of water diffusion into the cable material over time and the dynamic change process of dehydration in a vacuum drying device includes:

[0026] A water intrusion simulation model of the cable is established in COMSOL according to the water absorption diffusion coefficient;

[0027] A dehumidification simulation model of the cable is established in COMSOL according to the drying diffusion coefficient;

[0028] The moisture intrusion simulation model and the dehumidification simulation model are combined to establish the cable structure model.

[0029] Optionally, the step of establishing a water intrusion simulation model of the cable in COMSOL according to the water absorption diffusion coefficient includes:

[0030] The simulation model of the cable is constructed through the dilute species transfer module, the transfer properties of the material are set, and the calculated water absorption diffusion coefficient is used as the input parameter.

[0031] Optionally, the step of establishing a dehumidification simulation model of the cable in COMSOL according to the drying diffusion coefficient includes:

[0032] Based on the established cable moisture intrusion simulation model, the material transfer properties are changed and the calculated drying diffusion coefficient in the vacuum dehumidification process is used as an input parameter.

[0033] Optionally, the step of drying and dehumidifying the cable after the cable material reaches a preset condition according to the simulated diffusion dynamic change process, and adaptively selecting the drying temperature and drying time according to the simulated dehydration dynamic change process includes:

[0034] The moisture concentration of the water absorbing end surface is set as a boundary condition, and the preset condition is that the moisture concentration of the cable material reaches the set boundary condition.

[0035] Optionally, the step of setting the water concentration of the water absorbing end surface as a boundary condition includes:

[0036] The saturated vapor pressure is estimated by introducing the Tatens formula and the actual vapor pressure is calculated;

[0037] Calculate the absolute humidity based on the actual vapor pressure and the absolute ambient temperature;

[0038] The absolute humidity is taken as the moisture concentration of the water absorption section.

[0039] Optionally, the step of estimating the saturated vapor pressure by introducing the Tatens formula and calculating the actual vapor pressure includes:

[0040] The introduced Tatens formula is:

[0041]

[0042] Among them, e s represents saturated vapor pressure, T represents air temperature, and e represents actual vapor pressure;

[0043] The actual vapor pressure is calculated by:

[0044] e=e s ×RH×100

[0045] Where RH stands for relative humidity, expressed as a decimal;

[0046] The calculation formula of absolute humidity is:

[0047]

[0048] Among them, R v is the gas constant of water vapor, M is the molar mass of water molecules, T k is the absolute temperature of the environment.

[0049] The technical solution provided by the present invention may include the following beneficial effects:

[0050] In the present invention, by simulating the dynamic change process of diffusion, the moisture inside the cable is effectively controlled, the performance degradation and damage caused by moisture are prevented, and the service life of the cable is extended. By simulating the dynamic change process of dehydration, the optimal drying temperature and time are selected to improve the dehumidification efficiency and reduce energy consumption. The environmental temperature and humidity data are obtained in real time, and the dehumidification parameters are adjusted dynamically to achieve precise dehumidification. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The accompanying drawings herein are incorporated into and constitute a part of the specification, illustrate embodiments consistent with the present invention, and together with the specification are used to explain the principles of the present invention. Obviously, the accompanying drawings described below are only some embodiments of the present invention, and for those of ordinary skill in the art, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0052] Figure 1 A schematic flow chart showing an adaptive dehumidification method for a cable end sealing process in an exemplary embodiment of the present invention is shown.

[0053] Figure 2 A schematic logic block diagram of an adaptive dehumidification method for a cable end sealing process in an exemplary embodiment of the present invention is shown.

[0054] Figure 3 A moisture diffusion cloud diagram of a moisture intrusion cable model simulation in an exemplary embodiment of the present invention is shown.

[0055] Figure 4 A moisture diffusion cloud diagram of a dehumidification cable model simulation in an exemplary embodiment of the present invention is shown. DETAILED DESCRIPTION

[0056] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the present invention will be more comprehensive and complete and fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0057] In addition, the accompanying drawings are only schematic illustrations of embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings represent the same or similar parts, and their repeated descriptions will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0058] The present invention provides a cable end sealing process adaptive dehumidification method, referring to Figure 1 As shown in , the following steps are included:

[0059] Step S101: performing a water absorption test on a cable material to obtain water absorption rate data of the cable material.

[0060] Step S102: performing a vacuum drying test on the water-absorbed cable material to obtain quality change data of the cable material before and after drying.

[0061] Step S103: using the water diffusion model and according to the water absorption rate data and the mass change data, respectively calculating the water absorption diffusion coefficient and the drying diffusion coefficient of the cable material.

[0062] Step S104: constructing a cable structure model according to the water absorption diffusion coefficient and the drying diffusion coefficient, and simulating the dynamic change process of water diffusion into the cable material over time and the dynamic change process of water dehydration in the vacuum drying device.

[0063] Step S105: After the cable material reaches a preset condition according to the simulated diffusion dynamic change process, the cable is dried and dehumidified, and the drying temperature and drying time are adaptively selected according to the simulated dehydration dynamic change process.

[0064] It should be understood that the present invention proposes an adaptive dehumidification method that comprehensively considers the cable material characteristics and environmental conditions. The method uses COMSOL Multiphysics simulation software to simulate the water absorption and dehumidification process of the cable under the current temperature and humidity conditions in detail, optimizes the sealing effect of the cable end, and thus accurately evaluates and improves the efficiency and reliability of the dehumidification process.

[0065] It is also necessary to understand that the cable model, size, and real-time temperature and humidity data of the environment are first obtained. The cable material slices are subjected to a water absorption test at the current temperature and humidity to obtain the water absorption rate data of the cable material and its mass change before and after water absorption. Based on the water absorption rate data, the Langmuir model is used to calculate the moisture diffusion coefficient of the cable material in the current environment.

[0066] It is also important to understand the use of sensors and data acquisition equipment to obtain cable model, size and environmental real-time temperature and humidity data.

[0067] It is also important to understand that reference Figure 2 As shown, the adaptive dehumidification method for the cable end sealing process is more specifically implemented as follows:

[0068] 1) Obtain cable model, size and real-time temperature and humidity data of the environment.

[0069] 2) Perform a water absorption test on the cable material slices at the current temperature and humidity to obtain the mass change of the cable material before and after water absorption and the water absorption rate of the cable material.

[0070] 3) Based on the water absorption data, the Langmuir model is used to calculate the moisture diffusion coefficient of the cable material in the current environment.

[0071] 4) According to the current temperature and humidity environment, a cable moisture intrusion simulation model is established in COMSOL based on the diffusion coefficient and cable size.

[0072] 5) The moisture concentration of the water absorption end surface is set as the boundary condition to simulate the diffusion process of moisture invading the interior of the cable over time under the current temperature and humidity.

[0073] 6) For materials that are damp during the water absorption test, select an appropriate drying temperature to conduct a vacuum dehumidification test to obtain the quality changes of the cable material before and after dehumidification.

[0074] 7) Based on the dehydration rate data, calculate the diffusion coefficient and mass transfer coefficient of the cable material during vacuum dehumidification at the selected temperature.

[0075] 8) According to the diffusion coefficient in the vacuum dehumidification process, a dehumidification simulation model of the cable is established in COMSOL.

[0076] 9) Set boundary conditions such as mass transfer coefficient to simulate the process of water being removed from the cable over time at the selected drying temperature.

[0077] 10) According to actual requirements, select the appropriate drying temperature and drying time to determine the best dehumidification method in practical applications.

[0078] It is also important to understand that reference Figure 3 As shown, the moisture diffusion cloud map (400 minutes, 800 minutes, 1200 minutes) of the moisture intrusion experiment under the current temperature and humidity conditions can intuitively display the diffusion of moisture inside the cable. By setting the research step and time range, the law of the change of the internal moisture concentration of the cable port exposed to the current environmental temperature and humidity conditions over time can be obtained, realizing the intuitive display of the change of the moisture concentration inside the cable over time. Through COMSOL simulation software, the present invention draws a change diagram of the moisture concentration inside the cable, and further combines the moisture concentration change diagram calculated by the domain probe. These graphical results intuitively show the moisture penetration behavior and moisture distribution state of the cable at different time nodes.

[0079] It is also necessary to understand that for materials that are damp during the water absorption test, an appropriate drying temperature is selected to conduct a vacuum dehumidification test to obtain the mass change of the cable material before and after dehumidification. Based on the dehydration rate data, the drying diffusion coefficient and mass transfer coefficient of the cable material during the vacuum dehumidification process at the selected temperature are calculated.

[0080] It is also necessary to understand that, based on the drying diffusion coefficient in the vacuum dehumidification process, a cable dehumidification simulation model is established in COMSOL Multiphysics. Boundary conditions such as mass transfer coefficient are set to simulate the process of water being removed from the inside of the cable over time at the selected drying temperature.

[0081] It is also important to understand that reference Figure 4 As shown, through the moisture diffusion cloud diagram in the vacuum dehumidification simulation at selected temperatures (1250 minutes, 1400 minutes, 1600 minutes), the moisture diffusion behavior in the dehumidification process can be analyzed in detail.

[0082] It is also important to understand that this graphical display method not only provides researchers with a window to directly observe the water absorption performance of cables, but more importantly, it allows a clear comparison of the differences in moisture barrier performance between different cable materials and designs. In addition, these simulation result graphs provide valuable information for a deeper understanding of the response mechanism of cable materials to environmental moisture, help identify potential weaknesses in cable performance, and provide a scientific basis for subsequent material improvements and cable design optimization.

[0083] It is also important to understand that the moisture diffusion cloud map generated by the simulation software and the moisture concentration change map calculated by the domain probe can intuitively show the moisture behavior of the cable under different dehumidification conditions. These simulation results can deeply understand the moisture detachment and movement path of the damp cable under different dehumidification conditions, provide a scientific basis, optimize the dehumidification path and parameters, improve the dehumidification efficiency, shorten the cable recovery time, and ensure that the cable can be quickly and safely put back into use.

[0084] It is also necessary to understand that according to actual requirements, the appropriate drying temperature and drying time should be selected to determine the best dehumidification method in actual application. Comprehensively considering the characteristics of cable materials, actual application environment and dehumidification efficiency, the optimal dehumidification conditions and processes are finally determined to provide strong technical support for the safe operation and maintenance of cables.

[0085] It is also necessary to understand that the optimal dehumidification temperature and time should be selected by comprehensively considering the characteristics of the cable material, the actual application environment and the dehumidification efficiency.

[0086] The above-mentioned adaptive dehumidification method for the cable end sealing process is adopted to effectively control the moisture inside the cable by simulating the dynamic change process of diffusion, prevent performance degradation and damage caused by moisture, and extend the service life of the cable. By simulating the dynamic change process of dehydration, the optimal drying temperature and time are selected to improve the dehumidification efficiency and reduce energy consumption. Real-time acquisition of environmental temperature and humidity data, dynamic adjustment of dehumidification parameters, and accurate dehumidification are achieved.

[0087] Next, we will refer to Figures 1 to 4The various steps of the above-mentioned cable end sealing process adaptive dehumidification method in this exemplary embodiment are described in more detail.

[0088] In some embodiments, step S101 includes:

[0089] The water absorption weight gain rate is used to characterize the water absorption characteristics of the material. The calculation formula for the water absorption weight gain rate m(t) is:

[0090]

[0091] Among them, m0 is the initial mass of the cable material, m t It is the mass of the cable material after absorbing water.

[0092] It is important to understand that the cable material is sliced, and a water absorption test is performed at the current temperature and humidity. The mass change of the sample before and after water absorption is recorded to obtain the water absorption rate of the cable material. Taking the 110kV single-core XLPE cable as the research object, the cable material (XLPE, semi-conductive rubber) is sliced ​​to ensure that the surface area of ​​each sample is basically close, and a water absorption test is carried out (without considering the water absorption characteristics of other materials). The test method refers to the standard ISO 62-2008 "Plastics-Determination of water absorption".

[0093] In some embodiments, step S103 includes:

[0094] The calculation model formula of the drying diffusion coefficient D during vacuum drying is:

[0095]

[0096] Where m1 is the mass of the sample after drying and dehumidification; m t -m1 is the mass reduced during vacuum drying; m t -m0 is the mass increased by the sample after absorbing water; S is the surface area of ​​the sample; V is the volume of the sample; t is the drying and heating time; d is the thickness of the sample.

[0097] It is important to understand that the cable material sample that has been dampened in the water absorption test is placed in a vacuum drying box, the vacuum degree, drying temperature and drying time are set, and the vacuum drying test is carried out to record the mass change of the sample before and after dehumidification. The sample that has been dampened after the water absorption test is taken as the research object, and the increased mass of the sample after being dampened is recorded. The sliced ​​sample is placed in a vacuum drying box, the vacuum degree, drying temperature and drying time are set, and then the dehumidification test is started.

[0098] It is also necessary to understand that the removal process of water molecules inside the material can be regarded as a permeation process. According to the definition of diffusion coefficient, the diffusion coefficient D in the vacuum drying process can be expressed as formula (2). t The unit of is g; the unit of S is m 2 ; The unit of V is m 3 ; The unit of t is s; the unit of d is m, the unit of D is m 2 / s.

[0099] In some embodiments, reference Figure 3 As shown, step S103 includes:

[0100] A moisture diffusion model for cable materials is constructed based on the water absorption rate data. The moisture diffusion model is used to express the curve relationship between the total moisture content of the material and time. The water absorption diffusion coefficient of the cable material in the current temperature and humidity environment is calculated through the moisture diffusion model.

[0101] It should be understood that the Langmuir moisture diffusion model can well describe the water absorption characteristics of materials such as electrolytes. The model indicates that the relationship between the total moisture content of the material and time is shown in formula (3), where y(t) is shown in formula (4).

[0102]

[0103] Where, m(t) is the mass increment of water absorbed by the sample, m ∞ is the mass increment of the sample saturated with water, α is the adsorption coefficient of water molecules from free state to bound state per unit time and volume, β is the desorption coefficient of water molecules from bound state to free state per unit time and volume, h is the diffusion coefficient of free water molecules in polymer, t is the water absorption time, and h is the thickness of the sample. Use the least square method in MATLAB to write equations (3) and (4), and then substitute the scatter point values ​​of the water absorption rate of the corresponding material into this model to obtain the water absorption growth curve of the cable material at 90% relative humidity and the diffusion coefficient under this environment.

[0104] In some embodiments, reference Figure 2 As shown, step S104 includes:

[0105] Step S401: Establishing a water intrusion simulation model of the cable in COMSOL according to the water absorption diffusion coefficient.

[0106] Step S402: Establishing a dehumidification simulation model of the cable in COMSOL according to the drying diffusion coefficient.

[0107] Step S403: combining the moisture intrusion simulation model and the dehumidification simulation model to establish a cable structure model.

[0108] It is important to understand that domain probes are set in the water intrusion simulation model and probe graphs are drawn. In order to deeply analyze and understand the changing rules of the water content of cable materials during the water absorption process, multiple domain probes are set in the COMSOL simulation model to cover various domains of cable materials, aiming to explore in detail the differences in the behaviors of different cable materials during water penetration. The probe type is set to "average value", and by capturing the average water content of the material in the entire domain, the changes in the water content of the cable material are monitored in real time, and the probe result graph is drawn in the simulation results. This makes it intuitive and scientific to compare the water absorption characteristics of different cable materials, and further reveals the performance differences of various materials under the same environmental conditions.

[0109] In some embodiments, step S401 includes:

[0110] The simulation model of the cable is constructed through the dilute species transfer module, the transfer properties of the material are set, and the calculated water absorption diffusion coefficient is used as the input parameter.

[0111] It should be understood that first, select the Diluted Species Transport Module in the Chemical Substance Transport Module in the COMSOL software and select the transient study. The 110kV XLPE cable placed in a 90% relative humidity environment is taken as the research object, and the cable geometry model is established. Its internal structure from inside to outside is: copper core, XLPE, semi-conductive rubber, metal shielding layer and outer sheath. The cable size, description of the material of each layer of the cable structure and the structural parameters are shown in Table 1.

[0112] Table 1 Cable size parameters

[0113]

[0114]

[0115] Diluted species transport model, set the initial value of the entire cable to 0. The diffusion coefficient of the cable material is calculated by the Langmuir model. Select the cable material domain, set the diffusion coefficients of different materials to the corresponding domains, and for the copper core, metal shielding layer and outer sheath domains that do not consider water absorption, set their diffusion coefficients to 1×10 -11 m 2 / s.

[0116] In some embodiments, step S402 includes:

[0117] Step S201: Based on the established cable moisture intrusion simulation model, the transfer properties of the material are changed, and the calculated drying diffusion coefficient in the vacuum dehumidification process is used as an input parameter.

[0118] It is also necessary to understand that the simulation model of the cable is constructed through the dilute species transfer module of the COMSOL software. The transfer properties of the material are set, and the calculated drying diffusion coefficient in the vacuum dehumidification process is used as the input parameter. First, select the dilute species transfer module in the chemical substance transfer module in the COMSOL software, and select transient research. The results calculated by the cable water absorption simulation model are taken as the research object, and the results of the calculation are inherited. The cable dehumidification simulation model is set with the calculation results of the water absorption cable model as the initial value. According to the drying diffusion coefficients corresponding to the different materials used in the cable, the drying diffusion coefficients of different materials are set to the corresponding cable material domain in the dilute species transfer module. The transfer properties of each cable material are set through the COMSOL software. In the dilute species transfer module, the initial value of the cable as a whole is set to the concentration value after the current environment absorbs water. Select the cable material domain, set the drying diffusion coefficients of different materials to the corresponding domain, and for the copper core, metal shielding layer and outer sheath, the domains that do not consider water absorption are set to 1×10 -11 m 2 / s.

[0119] According to the cable structure model boundary condition, set it to flux, select the flux type as external convection flux, and set the mass transfer coefficient and bulk concentration values. Select the boundary condition of flux in the physical field column, select the XLPE and semi-conductive rubber domains in the single-core cable, select the flux type as external convection, and set the mass transfer coefficient and bulk concentration 2 values. Since the vacuum drying box is an extremely low vacuum environment, it is considered that the moisture concentration in the box is close to 0 at this time, so the bulk concentration is set to 0.

[0120] Step S2011: Express the flux in terms of the amount of substance and combine it with a convection transfer scenario applicable to gas or liquid to establish a transfer phenomenon equation expression.

[0121] Step S2012: Set the moisture concentration in the vacuum domain to 0, divide the difference between the moisture concentration in the material domain of the cable port surface and the moisture concentration in the vacuum domain by the characteristic length as the concentration gradient of the cable port surface, substitute it into the transfer phenomenon equation expression, and obtain the flux expression.

[0122] Step S2013: define flux as the amount of moisture material flowing through the cable port area per unit time, indicating the degree of moisture concentration removal inside the cable, and determine the mass transfer coefficient expression in combination with the flux expression.

[0123] The mass transfer coefficient calculation model is established through the above steps, and the mass transfer coefficient finally calculated is substituted into the value of the mass transfer coefficient in the setting of the boundary conditions.

[0124] In some embodiments, reference Figure 2 As shown, step S105 includes:

[0125] Step S501: setting the water concentration of the water absorbing end surface as a boundary condition, and the preset condition is that the water concentration of the cable material reaches the set boundary condition.

[0126] It is important to understand that the moisture concentration at the water absorption end face is set as a boundary condition to simulate the diffusion process of moisture invading the interior of the cable over time under the current temperature and humidity. In the COMSOL Multiphysics software, the dilute species transport module is used to build a simulation model of the cable. By setting the transfer properties of the material and using the calculated water absorption diffusion coefficient as an input parameter, the moisture concentration at the water absorption end face is set as a boundary condition to simulate the diffusion process of moisture invading the interior of the cable over time under specific environmental humidity conditions.

[0127] In some embodiments, reference Figure 2 As shown, step S501 includes:

[0128] Step S5011: Estimate the saturated vapor pressure by introducing the Tatens formula and calculate the actual vapor pressure;

[0129] Step S5012: Calculate the absolute humidity according to the obtained actual vapor pressure and the absolute temperature of the environment;

[0130] Step S5013: taking the absolute humidity as the moisture concentration of the water absorption section.

[0131] It is important to understand that in order to accurately simulate and evaluate the impact of environmental conditions on the moisture permeation behavior of cable insulation materials, it is necessary to calculate the absolute humidity values ​​required in the simulation boundary conditions.

[0132] In some embodiments, step S5011 includes:

[0133] The introduced Tatens formula is:

[0134]

[0135] Among them, e s represents saturated vapor pressure, T represents air temperature, and e represents actual vapor pressure;

[0136] The actual vapor pressure is calculated by:

[0137] e=e s ×RH×100 (6)

[0138] Where RH stands for relative humidity, expressed as a decimal;

[0139] The calculation formula of absolute humidity is:

[0140]

[0141] Among them, R v is the gas constant of water vapor, M is the molar mass of water molecules, T k is the absolute temperature of the environment.

[0142] It is important to understand that the saturated vapor pressure is estimated by introducing the Tetens formula, which uses the measured value of the air temperature as an input parameter. s represents the saturated vapor pressure (unit: hPa), T represents the air temperature (unit: Celsius). Actual vapor pressure e (unit: Pa). Ambient absolute temperature T k (Unit: Kelvin). R v is the gas constant of water vapor, which is 461.5 J / (kg·K). Through the above steps, the absolute humidity value at room temperature 25°C and 90% relative humidity can be accurately calculated, which is 1.15 mol / m 3 In COMSOL, select the boundary condition type as concentration, select the cable water absorption end face and set the absolute humidity value under 90% humidity environment.

[0143] The expression of mass transfer coefficient is:

[0144]

[0145] Where m is the mass of water removed during vacuum drying, M is the molar mass of water molecules, t is the drying time, A is the cross-sectional area of ​​the cable port, and C1 is the moisture concentration of the material domain on the cable port surface.

[0146] The specific process of the mass transfer coefficient calculation model is as follows:

[0147] The traditional transfer phenomenon equation expression type is:

[0148]

[0149] That is, j flux is the concentration gradient and diffusion coefficient D(m 2 / s).

[0150] Expressing the flux j in terms of the amount of substance, we get the transformed formula:

[0151]

[0152] The dimensions of this formula are:

[0153] The convective mass transfer coefficient is applicable to the convective transfer scenario of gas or liquid, and its expression is

[0154]

[0155] Where k is the mass transfer coefficient (unit: m / s), L is the characteristic length. For pipe flow, the characteristic length L is the diameter of the cable (unit: m). Therefore, formula (5) is expressed as:

[0156]

[0157] During the vacuum drying process, the water concentration in the vacuum domain is considered to be 0, so the concentration gradient on the cable port surface is The difference between the moisture concentration C1 of the material domain of the cable port surface and the moisture concentration C2 of the vacuum domain is divided by the characteristic length L, and the result is:

[0158]

[0159] The flux is defined as the amount of moisture flowing through the cable port area per unit time, which is used to indicate the degree of moisture concentration removal inside the cable. The new flux expression is:

[0160]

[0161] Where A is the cross-sectional area of ​​the cable port; t is the drying time; n is the amount of water molecules flowing through the cross section, m is the mass of water removed during the vacuum drying process, and M is the molar mass of water molecules.

[0162] Combining formulas (13) and (14), we get:

[0163]

[0164] Where m is the mass of water removed during vacuum drying; M is the molar mass of water molecules; and k is the mass transfer coefficient. Formula (15) is also the mass transfer coefficient expression (8).

[0165] It should be understood that in the cable structure model, a domain probe is set, the probe type is set to "average value", and the corresponding material domain is selected as the average value of the moisture concentration of the material domain. In the definition column, a domain probe is set, the probe type is average value, and the corresponding material domain is selected as the average value of the moisture concentration of the material domain. The other values ​​of formula (8) can be obtained according to the actual situation, and the mass transfer coefficient k of the material domain can be solved by this formula. The calculated mass transfer coefficient is brought into the flux boundary condition setting under the material domain.

[0166] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

[0167] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. The present invention is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the appended claims.

Claims

1. A method for adaptive dehumidification during cable end sealing process, characterized in that: include: Performing a water absorption test on the cable material to obtain water absorption rate data of the cable material; Performing a vacuum drying test on the water-absorbed cable material to obtain quality change data of the cable material before and after drying; Calculating the water absorption diffusion coefficient and the drying diffusion coefficient of the cable material respectively according to the water absorption rate data and the mass change data using a water diffusion model; A cable structure model is constructed according to the water absorption diffusion coefficient and the drying diffusion coefficient, and a dynamic change process of water diffusion into the cable material over time and a dynamic change process of dehydration in a vacuum drying device are simulated; After the cable material reaches a preset condition according to the simulated diffusion dynamic change process, the cable is dried and dehumidified, and the drying temperature and drying time are adaptively selected according to the simulated dehydration dynamic change process.

2. The cable end sealing process adaptive dehumidification method according to claim 1, characterized in that: The step of performing a water absorption test on the cable material to obtain water absorption rate data of the cable material comprises: The water absorption weight gain rate is used to characterize the water absorption characteristics of the material. The calculation formula for the water absorption weight gain rate m(t) is: Where m0 is the initial mass of the cable material, m t It is the mass of the cable material after absorbing water.

3. The cable end sealing process adaptive dehumidification method according to claim 2, characterized in that: The step of using the moisture diffusion model and calculating the water absorption diffusion coefficient and the drying diffusion coefficient of the cable material respectively according to the water absorption rate data and the mass change data comprises: The calculation model formula of the drying diffusion coefficient D during vacuum drying is: Where m1 is the mass of the sample after drying and dehumidification; m t -m1 is the mass reduced during vacuum drying; m t -m0 is the mass increased by the sample after absorbing water; S is the surface area of ​​the sample; V is the volume of the sample; t is the drying and heating time; d is the thickness of the sample.

4. The cable end sealing process adaptive dehumidification method according to claim 3, characterized in that: The step of using the moisture diffusion model and calculating the water absorption diffusion coefficient and the drying diffusion coefficient of the cable material respectively according to the water absorption rate data and the mass change data comprises: A moisture diffusion model of the cable material is constructed according to the water absorption rate data, and the moisture diffusion model is used to express the curve relationship between the total moisture content of the material and time; the water absorption diffusion coefficient of the cable material in the current temperature and humidity environment is calculated by the moisture diffusion model.

5. The cable end sealing process adaptive dehumidification method according to claim 4, characterized in that: The step of constructing a cable structure model according to the water absorption diffusion coefficient and the drying diffusion coefficient, and simulating the dynamic change process of water diffusion into the cable material over time and the dynamic change process of dehydration in a vacuum drying device includes: A water intrusion simulation model of the cable is established in COMSOL according to the water absorption diffusion coefficient; A dehumidification simulation model of the cable is established in COMSOL according to the drying diffusion coefficient; The moisture intrusion simulation model and the dehumidification simulation model are combined to establish the cable structure model.

6. The cable end sealing process adaptive dehumidification method according to claim 5, characterized in that: The step of establishing a water intrusion simulation model of the cable in COMSOL according to the water absorption diffusion coefficient comprises: The simulation model of the cable is constructed through the dilute species transfer module, the material transfer properties are set, and the calculated water absorption diffusion coefficient is used as the input parameter.

7. The cable end sealing process adaptive dehumidification method according to claim 6, characterized in that: The step of establishing a dehumidification simulation model of the cable in COMSOL according to the drying diffusion coefficient includes: Based on the established cable moisture intrusion simulation model, the material transfer properties are changed and the calculated drying diffusion coefficient in the vacuum dehumidification process is used as an input parameter.

8. The cable end sealing process adaptive dehumidification method according to any one of claims 1 to 7, characterized in that: The step of drying and dehumidifying the cable after the cable material reaches a preset condition according to the simulated diffusion dynamic change process, and adaptively selecting the drying temperature and drying time according to the simulated dehydration dynamic change process includes: The moisture concentration of the water absorbing end surface is set as a boundary condition, and the preset condition is that the moisture concentration of the cable material reaches the set boundary condition.

9. The cable end sealing process adaptive dehumidification method according to claim 8, characterized in that: The step of setting the water concentration of the water absorption end surface as a boundary condition includes: The saturated vapor pressure is estimated by introducing the Tatens formula and the actual vapor pressure is calculated; Calculate the absolute humidity based on the actual vapor pressure and the absolute ambient temperature; The absolute humidity is taken as the moisture concentration of the water absorption section.

10. The cable end sealing process adaptive dehumidification method according to claim 9, characterized in that: The step of estimating the saturated vapor pressure by introducing the Tatens formula and calculating the actual vapor pressure includes: The introduced Tatens formula is: Among them, e s represents saturated vapor pressure, T represents air temperature, and e represents actual vapor pressure; The actual vapor pressure is calculated by: and=and s ×RH×100 Where RH stands for relative humidity, expressed as a decimal; The calculation formula of absolute humidity is: Among them, R v is the gas constant of water vapor, M is the molar mass of water molecules, T k is the absolute temperature of the environment.

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