Streamer discharge simulation modeling method, system, medium and equipment of charge behavior under complex working condition coupling

Abstract

The application belongs to the technical field of equipment insulation influence evaluation considering streamer discharge, and provides a streamer discharge simulation modeling method, system, medium and equipment of charge behavior under complex working condition coupling, which is based on the theory of shearing separation of double electric layer, and an oil-paper-interface multi-region charge dynamic transport simulation model is established by coupling oil flow convection term, shearing term and temperature effect; based on the established transport simulation model, the whole evolution process of streamer discharge from diffusion, longitudinal evolution to transverse migration under the coupling of electric field, fluid field and thermal field is simulated by combining the charge injection and extraction boundary conditions at the electrode, the charge density distribution and electric field strength distribution data in the streamer evolution process are obtained; the streamer evolution law is analyzed based on the charge density distribution and electric field strength distribution data, so as to evaluate the oil-paper insulation state or optimize the oil-paper insulation structure. The coupling effects of electric field, fluid field and thermal field are comprehensively considered, and the actual operating condition of the converter transformer is more accurately simulated.

Description

Technical Field

[0001] This invention belongs to the field of equipment insulation impact assessment technology considering streamer discharge, and particularly relates to streamer discharge simulation modeling method, system, medium and equipment for charge behavior under complex operating conditions. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Converter transformers are core equipment in ultra-high voltage direct current (UHVDC) transmission systems, enabling power transmission and conversion. Their reliable operation is crucial for the safety and stability of the entire power grid. The valve-side winding insulation is subjected to a complex electric field of superimposed AC and DC harmonics for extended periods, while simultaneously operating within a forced oil circulation cooling system, requiring it to withstand the effects of a fluid field with a significant temperature gradient. This complex operating condition, involving the coupling of multiple physical fields (electricity, current, and heat), makes streamer discharge in the oil-paper insulation system a primary cause of insulation faults and even breakdowns.

[0004] Current research on discharge and charge behavior in oil-paper insulation has made some progress. For example, some studies have analyzed the propagation speed, shape, phase distribution, and discharge current of streamers under DC, AC, or AC / DC combined voltages based on different electrode structures. Other studies have explored the influence of harmonics on partial discharge characteristic parameters, or the effect of temperature on the partial discharge initiation voltage and degradation process of insulating materials. Regarding charge behavior, researchers have focused on the charge transport, injection, and accumulation characteristics at the oil-paper interface and within the paper under DC or AC fields. Simulation studies have simulated the charge distribution and electric field distortion during the discharge process by establishing streamer evolution models or bipolar charge transport models.

[0005] It is evident that most existing studies analyze the streamer discharge and charge dynamic behavior in oil-paper insulation separately, and the mechanism of charge influence on streamer discharge under AC / DC superimposed harmonic conditions remains unclear. Furthermore, existing studies typically focus on single or simplified physical fields, failing to comprehensively consider the strong coupling effect of electric field, fluid field, and temperature field in actual converter transformer operation. This makes it difficult to accurately reflect the complex behavior of the insulation system under real operating conditions, and consequently, it is impossible to accurately assess the insulation state of converter transformers and optimize their structural design. Summary of the Invention

[0006] To address at least one of the technical problems mentioned above, this invention provides a method, system, medium, and equipment for simulating and modeling the charge behavior under complex operating conditions. Based on charge measurement, discharge characteristic measurement, and joist evolution simulation, the development and evolution process of joist discharge under the multi-field coupling of electric current and heat is analyzed, providing theoretical support for the state assessment and structural optimization of the oil-paper insulation of converter transformers.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] The first aspect of the present invention provides a method for simulating and modeling the charge behavior of a streamer discharge under complex operating conditions, comprising the following steps:

[0009] Based on the theory of electric double layer shear separation, a simulation model of dynamic charge transport in multiple regions of the oil-paper interface is established, coupling oil flow convection terms, shear terms, and temperature effects; specifically including:

[0010] Based on the influence of oil flow convection terms and temperature, a modified fluid dynamics drift-diffusion model is used to describe the dynamic process of charge in oil.

[0011] Based on the influence of temperature on the carrier migration process, a modified bipolar carrier migration model is used to describe the dynamic process of charge in paper.

[0012] Based on the effects of oil flow convection, oil flow shear, and temperature, a modified Ohmic model is used to describe the charge dynamics at the oil-paper interface.

[0013] Based on the established transport simulation model, combined with the charge injection and extraction boundary conditions at the electrodes, the entire evolution process of the streamer discharge from diffusion and longitudinal evolution to lateral migration under the multi-field coupling of electric current and heat is simulated, and the charge density distribution and electric field intensity distribution data during the streamer evolution process are obtained.

[0014] The evolution of the flow stream is analyzed based on the charge density distribution and electric field intensity distribution data to assess the state of the oil-paper insulation or optimize the oil-paper insulation structure.

[0015] Furthermore, the oil-based model used to describe the dynamic process of charge in the oil is expressed as:

[0016] ,

[0017] ,

[0018] ,

[0019] ,

[0020] ,

[0021] In the formula, , and These represent the charge densities of electrons, positive ions, and negative ions, respectively. Let be the charge density at the oil-paper interface. For oil flow velocity, For electron adsorption time, The electron mobility in oil, and These represent the recombination rates of positive ions with electrons and positive ions with negative ions, respectively. For charge quantity, Let be the relative permittivity of oil. The vacuum permittivity, The positive ion mobility in oil. The migration rate of negative ions in oil. The charge density generation rate caused by field ionization. The charge density generation rate resulting from ion pair dissociation. The charge density generation rate resulting from impact ionization. The thermal conductivity of oil is... For oil density, The specific heat capacity of oil. For electric potential, For electric field strength, It is a vector differential operator.

[0022] Furthermore, the paper model used to describe the dynamic process of charge in the paper is represented as follows:

[0023] ,

[0024] ,

[0025] ,

[0026] ,

[0027] ,

[0028] In the formula, These represent the charge densities of free electrons, trapped electrons, free holes, and trapped holes, respectively. The free electron mobility in the insulating paperboard. The free hole mobility on the insulating paperboard. For maximum electron capture density, The relative permittivity of the insulating paperboard is... These represent the recombination rates of trapped electrons and trapped holes, free electrons and trapped holes, and trapped electrons and free holes, respectively. and These are the trapping rates for electrons and holes, respectively. and These are the extraction rates of electrons and holes, respectively. The vacuum permittivity, denoted as electric field strength.

[0029] Furthermore, the recombination rate, trapping rate, and de-trapping rate are all thermally activated processes, and their calculation process is expressed as follows:

[0030] ,

[0031] In the formula, This indicates the recombination rate, trapping rate, and de-trapping rate of charges in paper at ambient temperature. This represents the recombination rate, trapping rate, and de-trapping rate of charges in the paper at a reference temperature. For reference temperature, for Thermal activation energy during the process Indicates the type of charge in the paper. This indicates the composite rate, the ingress rate, and the detachment rate. Indicates the composite rate. Indicates the trapping rate. Indicates the rate of detachment. Represents electron, It indicates an empty hole.

[0032] Furthermore, the oil-paper interface model used to describe the charge dynamics at the oil-paper interface is expressed as:

[0033] ,

[0034] ,

[0035] In the formula, and These represent the charge densities of electrons, positive ions, and negative ions, respectively. Let be the charge density at the oil-paper interface. For tangential velocity, It is the acceleration due to gravity. For oil density, The charge stripping coefficient, For oil flow shear stress, The positive ion mobility in oil. The migration rate of negative ions in oil. The electron mobility in oil, and These represent the charge densities of free electrons and free holes, respectively. The free electron mobility in the insulating paperboard. The free hole mobility on the insulating paperboard. and These represent the oil-side electric field and the paper-side electric field at the oil-paper interface, respectively. This represents the oil flow velocity.

[0036] Furthermore, the charge injection and extraction boundary conditions at the electrodes include the current density of charge injected into the oil by the high-pressure side electrode, the current density of charge injected into the paper by the low-pressure side electrode, and the current density of charge extracted by the high-pressure side electrode and the low-pressure side electrode.

[0037] Furthermore, the entire evolution process of the streamer discharge under simulated electric-current-thermal multi-field coupling, from diffusion and vertical evolution to lateral migration, includes:

[0038] During the diffusion stage, the simulation simulates the release of positive charges from the needle electrode and their diffusion to the surrounding area, as well as the migration of negative charges to the needle electrode, resulting in charge stratification to form a streamer boundary, and simulates the recombination of positive and negative charges to form a zero electric field region.

[0039] In the longitudinal evolution stage, the simulated flow boundary develops along the symmetrical axis perpendicular to the paperboard and towards the paperboard, forming the main discharge channel;

[0040] During the lateral evolution stage, the simulation shows that after the stream head reaches the paper interface, the positive polarity charge develops and dissipates tangentially at the paperboard interface.

[0041] A second aspect of the present invention provides a streamer discharge simulation modeling system for charge behavior under complex operating conditions, comprising:

[0042] The streamer discharge model construction module is used to establish a simulation model of dynamic charge transport in multiple regions of the oil-paper interface, coupled with oil flow convection, shearing, and temperature effects, based on the theory of electric dipole layer shear separation. Specifically, it includes:

[0043] Based on the influence of oil flow convection terms and temperature, a modified fluid dynamics drift-diffusion model is used to describe the dynamic process of charge in oil.

[0044] Based on the influence of temperature on the carrier migration process, a modified bipolar carrier migration model is used to describe the dynamic process of charge in paper.

[0045] Based on the effects of oil flow convection, oil flow shear, and temperature, a modified Ohmic model is used to describe the charge dynamics at the oil-paper interface.

[0046] The streamer discharge evolution simulation module is used to simulate the entire evolution process of streamer discharge from diffusion and longitudinal evolution to lateral migration under the multi-field coupling of electric current and heat, based on the established transport simulation model and combined with the charge injection and extraction boundary conditions at the electrodes, and to obtain the charge density distribution and electric field intensity distribution data during the streamer evolution process.

[0047] The strategy generation module is used to analyze the evolution law of the streamer based on the charge density distribution and electric field intensity distribution data, so as to evaluate the state of the oil-paper insulation or optimize the oil-paper insulation structure.

[0048] A third aspect of the present invention provides a computer-readable storage medium.

[0049] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the above-described method for simulating and modeling charge behavior under complex operating conditions.

[0050] A fourth aspect of the present invention provides a computer device.

[0051] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the steps in the streamer discharge simulation modeling method for charge behavior under complex operating conditions as described above.

[0052] Compared with the prior art, the beneficial effects of the present invention are:

[0053] This invention comprehensively considers the strong coupling effect of electric field, fluid field and temperature field in actual converter transformer operation, accurately reflects the complex behavior of insulation system under real working conditions, and provides a theoretical basis for evaluating the state of oil-paper insulation or optimizing the oil-paper insulation structure.

[0054] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0055] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0056] Figure 1 This is a flowchart of the streamer discharge simulation modeling method for charge behavior under complex operating conditions provided in this embodiment of the invention;

[0057] Figure 2 This is an image of a jet discharge in static oil at 320 K provided in an embodiment of the present invention;

[0058] Figure 3 This is the evolution process of jet discharge in static oil at 320 K provided in the embodiments of the present invention;

[0059] Figure 4 This is an image of a jet discharge in flowing oil at 380 K provided in an embodiment of the present invention;

[0060] Figure 5 This is the evolution process of jet discharge in flowing oil at 380 K provided in the embodiments of the present invention;

[0061] Figure 6This is the charge and electric field intensity curve directly below the needle tip provided in the embodiment of the present invention;

[0062] Figure 7 This invention provides the charge and electric field intensity distribution at the oil-paper interface during the lateral evolution stage, wherein (a) is the charge distribution at the oil-paper interface during the lateral evolution stage, and (b) is the electric field intensity distribution at the oil-paper interface during the lateral evolution stage.

[0063] Figure 8 These are the times required for the jet head to reach points (0,1), (0.4,1), and (0.8,1) at different temperatures, as provided in the embodiments of the present invention.

[0064] Figure 9 These are the charge densities required at the points (0,1), (0.4,1), and (0.8,1) where the jet head reaches at different temperatures, as provided in the embodiments of the present invention.

[0065] Figure 10 This refers to the average discharge amount provided in the embodiments of the present invention;

[0066] Figure 11 This is the maximum discharge amount provided by the embodiments of the present invention;

[0067] Figure 12 This refers to the discharge repetition rate provided in the embodiments of the present invention;

[0068] Figure 13 The discharge stage provided in the embodiments of the present invention. Detailed Implementation

[0069] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0070] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0071] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0072] To address the issues mentioned in the background section, where research on streamer discharge and charge behavior in oil-paper insulation is relatively independent, and the mechanism of charge influence on streamer discharge under AC / DC superimposed harmonic conditions remains unclear, and current research does not comprehensively consider the coupling effects of electric field, fluid field, and temperature field, making it difficult to simulate the actual operating conditions of converter transformers, this application improves the charge drift-diffusion model, bipolar load sub-transfer model, and Euclidean model based on the dipole layer shear separation theory. It simulates the dynamic charge transport process in oil-paper insulation under electro-current-thermal multi-field coupling and discusses the evolution mechanism of streamer discharge at different temperatures. The relationship between the charge characteristics and discharge characteristics of oil-paper insulation is established, and a method for studying the discharge mechanism under complex electro-current-thermal multi-field coupling is proposed, providing theoretical support for the state assessment and structural optimization of oil-paper insulation in converter transformers.

[0073] Example 1

[0074] like Figure 1 As shown, this embodiment provides a method for simulating and modeling the charge behavior under complex operating conditions, including the following steps:

[0075] Step 1: Based on the theory of electric double layer shear separation, establish a simulation model of dynamic charge transport in multiple regions of the oil-paper-interface coupled with oil flow convection, shear, and temperature effects;

[0076] Oil flow not only affects the charge density in the diffuse layer, but the shear force it generates also strips positive ions from the oil side of the compact layer and carries them into the oil flow. At the same time, oil temperature affects the changes in parameters such as charge trapping rate, detrapping rate, ionization rate, recombination rate, and electron adsorption time, thereby influencing the evolution of streamer discharge.

[0077] Specifically, the steps include the following:

[0078] Step 101: Based on the influence of oil flow convection term and temperature, modify the hydrodynamic drift-diffusion model to describe the dynamic process of charge in oil;

[0079] In this embodiment, the oil-in-oil model adopts the hydrodynamic drift-diffusion model. The modified oil-in-oil model includes three charge continuity equations (1)-(3), one Poisson equation (4), and one heat conduction equation (5), as shown below:

[0080] (1),

[0081] (2),

[0082] (3),

[0083] (4),

[0084] (5),

[0085] In the formula, , and These represent the charge densities of electrons, positive ions, and negative ions, respectively. Let be the charge density at the oil-paper interface. For oil flow velocity, The electron adsorption time is expressed as , For electron decay length, The electron mobility in oil, For electric field strength, and Let represent the recombination rates of positive ions with electrons and positive ions with negative ions, respectively, expressed as . , , For charge quantity, Let be the relative permittivity of oil. The vacuum permittivity, The positive ion mobility in oil. The migration rate of negative ions in oil. The charge density generation rate caused by field ionization is expressed as... , The number density of ionizable particles, Intermolecular distance, is Planck's constant. For effective electronic quality, The ionization energy of oil, The charge density generation rate resulting from ion pair dissociation is expressed as: , This is the rate factor for the dissociation of oil ion pairs. This represents the dissociation energy of a neutral ion pair. Boltzmann's constant, For ambient temperature, The charge density generation rate caused by impact ionization is expressed as... , The coefficient before the exponent. This is the temperature correction factor. For the exponent term, For vector differential operators, For oil density, The specific heat capacity of oil. The thermal conductivity of oil is... It represents the electric potential.

[0086] Step 102: Based on the effect of temperature, modify the bipolar charge carrier migration model to describe the dynamic process of charge in the paper;

[0087] In this embodiment, the paper model adopts the bipolar load cell migration model, and the modified paper model contains four charge continuity equations (6)-(9) and one Poisson equation (10).

[0088] (6),

[0089] (7),

[0090] (8),

[0091] (9),

[0092] (10),

[0093] In the formula, These represent the charge densities of free electrons, trapped electrons, free holes, and trapped holes, respectively. The free electron mobility in the insulating paperboard. The free hole mobility on the insulating paperboard. For maximum electron capture density, The relative permittivity of the insulating paperboard is... These represent the recombination rates of trapped electrons and trapped holes, free electrons and trapped holes, and trapped electrons and free holes, respectively. and These are the trapping rates for electrons and holes, respectively. and The de-trapping rates of electrons and holes are respectively. The recombination rate, trapping rate, and de-trapping rate are all thermally activated processes and can all be calculated using equation (11):

[0094] (11),

[0095] In the formula, This indicates the recombination rate, trapping rate, and de-trapping rate of charges in paper at ambient temperature. This represents the recombination rate, trapping rate, and de-trapping rate of charges in the paper at a reference temperature. For reference temperature, for example, when the reference temperature is 298 K, All , All are 5×10 -3 s -1 , All are 3×10 -4 s -1 , for Thermal activation energy during the process Indicates the type of charge in the paper. This indicates the composite rate, the ingress rate, and the detachment rate. Indicates the composite rate. Indicates the trapping rate. Indicates the rate of detachment. Represents electron, It indicates an empty hole.

[0096] Step 103: Based on the effects of oil flow convection, oil flow shear, and temperature, modify the Ohm model to describe the charge dynamics at the oil-paper interface.

[0097] The oil-paper interface model used to describe the charge dynamics at the oil-paper interface includes a charge continuity equation (12) and a Navier-Stokes momentum equation (13).

[0098] (12),

[0099] (13),

[0100] In the formula, For tangential velocity, It is the acceleration due to gravity. and These represent the oil-side electric field and the paper-side electric field at the oil-paper interface, respectively. The charge stripping coefficient, The shear stress of the oil flow is expressed as , The viscosity of the oil flow. The position is perpendicular to the direction of oil flow. This represents the oil flow velocity.

[0101] Step 2: Determine the boundary conditions for charge injection and extraction at the electrodes;

[0102] In this embodiment, the charge injection and extraction boundary conditions at the electrodes include the current density of charge injected into the oil by the high-voltage side electrode, the current density of charge injected into the paper by the low-voltage side electrode, and the current density of charge extracted by the high-voltage side electrode and the low-voltage side electrode.

[0103] Specifically, the current density of charge injected into the oil by the high-voltage side electrode. As shown in (14), the current density of charge injected into the paper by the low-voltage side electrode. As shown in (15), both satisfy Schottky's law. The current density of the charge extracted from the high-voltage side electrode and the low-voltage side electrode. and Then they are shown as (16) and (17) respectively.

[0104] (14),

[0105] (15),

[0106] (16),

[0107] (17),

[0108] In the formula, This refers to the oil-side electric field at the interface between the high-voltage side electrode and the oil. This represents the paper-side electric field at the interface between the grounded electrode and the paper. and These represent the injection of a potential barrier into the oil from the high-pressure side electrode and the injection of a potential barrier into the paper from the low-pressure side electrode, respectively. The electrode charge extraction coefficient is the needle electrode. The plate electrode charge extraction coefficient, and These represent different charge mobility in oil and paper. and These represent different charge densities in oil and paper, respectively.

[0109] Step 3: Based on the established transport simulation model, and combined with the charge injection and extraction boundary conditions at the electrodes, simulate the entire evolution process of the streamer discharge from diffusion and longitudinal evolution to lateral migration under multi-field coupling of electric current and heat, and obtain the charge density distribution and electric field intensity distribution data during the streamer evolution process; analyze the streamer evolution law based on the charge density distribution and electric field intensity distribution data to evaluate the oil-paper insulation state or optimize the oil-paper insulation structure;

[0110] Specifically, the steps include the following:

[0111] Step 301: Set the boundary conditions such as geometry, voltage, and flow velocity of the transport simulation model;

[0112] In this embodiment, the specific settings of the boundary conditions can be set according to experimental requirements;

[0113] Step 302: Run the simulation based on the boundary conditions to simulate the entire evolution process of the streamer discharge from diffusion and longitudinal evolution to lateral migration under the multi-field coupling of electric current and heat, and obtain the charge density distribution and electric field intensity distribution data during the streamer evolution process;

[0114] Images and evolution of jet discharge in static oil at 320 K are shown below. Figure 2 and Figure 3As shown, the streamer discharge channel is narrow and relatively bright. The streamer head reaches the cardboard, and the connection between the streamer tail and the needle electrode is broken. Through streamer discharge simulation, its evolution process can be roughly divided into three stages:

[0115] 1) Diffusion Stage: The needle electrode releases a large amount of positive charge, while the strong electric field near the needle tip ionizes the oil, generating a large number of electrons and ions. Under the influence of the electric field, negative charges migrate towards the needle electrode, and positive charges diffuse around the needle tip, resulting in charge stratification and the formation of a stream boundary (positive charge). Simultaneously, the recombination of positive and negative charges leads to a zero-electric-field region at the needle tip, breaking the connection between the stream tail and the needle electrode.

[0116] 2) Vertical evolution stage: The streamer boundary near the needle tip continues to spread outwards, forming smaller streamer branches. The electric field strength is highest on the axis of symmetry of the needle tip perpendicular to the cardboard. Under the influence of the electric field, the streamer boundary below the needle tip develops downwards along the axis of symmetry, forming a bright and narrow main discharge channel.

[0117] 3) Lateral evolution stage: After the main stream reaches the paper-paper interface, positive charges will accumulate rapidly and develop along a short tangential distance at the paperboard interface until they dissipate. During this period, the large amount of charge accumulated at the paperboard interface will trigger strong ionization, generating a large amount of negative charges, which will recombine with the downwardly developing positive charges, resulting in a zero electric field region.

[0118] Images and evolution of jet discharge in flowing oil at 380K are shown below. Figure 4 As shown and Figure 5 As shown, the discharge channel is extremely bright and has a large area. The stream is tilted along the oil flow direction and exhibits obvious migration on the cardboard surface. Simulation results show that the discharge diffusion range is larger in high-temperature flowing oil, the stream does not form a narrow discharge channel, and it rapidly develops along the oil flow direction after reaching the cardboard interface, forming a significant surging current.

[0119] Establish a Cartesian coordinate system with the needle tip as the origin. At 5 ns, Figure 5 The charge and electric field intensity curves directly below the needle tip are as follows: Figure 6 As shown. Figure 5 The charge and electric field intensity distribution at the interface of the oil paper is as follows Figure 7 As shown, the stream evolution process, combined with quantitative data analysis, specifically includes:

[0120] Within 0-5 ns, the positive polar charge at the stream boundary rapidly diffuses to the surroundings under the dominant influence of the high mobility caused by high temperature. At this time, the stream evolution speed is relatively fast and less affected by oil flow convection.

[0121] At 5 ns, the stream head evolved longitudinally to a depth of 0.67 mm, with a charge density of 417.56 C / m. 3The electric field strength is 178.16 kV / mm. Within the range of 0.21–0.89 mm, the charge fluctuates around 0. The trend of the electric field strength variation is the same as the change in charge.

[0122] At 10 ns, under the dominant influence of oil convection, the streamer forms a sloping, wide discharge channel along the oil flow direction. Simultaneously, the densely packed positive charges along the axis are carried by the oil flow and migrate tangentially during diffusion and longitudinal evolution. During this tangential migration, they encounter and recombine with longitudinally developing opposite charges. Therefore, the streamer exhibits a distinct stratification phenomenon during the 0-10 ns period.

[0123] The positive charges reaching the oil-paper interface do not accumulate for a long time under the influence of the oil flow, but instead rapidly propagate laterally across the paperboard surface, forming a thin charge strip (rush current). The charge density at 0 mm is 4039.06 C / m³ at 15 ns, 55 ns, and 95 ns, respectively. 3 2696.18 C / m 3 and 2583.62 C / m 3 The electric field strengths were 273.56 kV / mm, 173.82 kV / mm, and 168.73 kV / mm, respectively. At these points, the streamer head moved to positions of 0.09 mm, 1.14 mm, and 1.66 mm, respectively. During this process, due to the significant velocity difference between the laterally transported charges and the charges still evolving longitudinally, stratification also occurs.

[0124] The time required for the stream head to reach points (0,1), (0.4,1), and (0.8,1) at different temperatures, and their charge densities, are as follows: Figure 8 and Figure 9 As shown.

[0125] As the temperature increased from 320 K to 380 K, the longitudinal evolution time of the streamer, i.e., the time to reach point (0,1), decreased from 36 ns to 7 ns, representing an approximately 4.14-fold increase in the longitudinal evolution rate. The corresponding interfacial charge density increased from 238.17 C / m³. 3 Increased to 1424.21 C / m 3 The charge accumulation increased by approximately 4.98 times. The increased temperature increased the migration rate of charge carriers in the oil, rapidly reducing the longitudinal evolution time of the streamer. Simultaneously, the increased temperature accelerated the dissociation rate and collisional ionization rate of oil molecules, causing rapid charge accumulation at the oil-paper interface. The electric field distortion and increased ionization frequency caused by charge accumulation led to an increase in discharge repetition rate and discharge quantity, such as... Figure 10- Figure 12 As shown.

[0126] The lateral evolution of the stream was divided into two parts: the first half (points (0,1) to (0.4,1)) and the second half (points (0.4,1) to (0.8,1)). At 320 K, the time for the stream to reach points (0.4,1) and (0.8,1) was 81 ns and 113 ns, respectively. When the temperature increased to 380 K, the corresponding arrival times decreased to 19 ns and 36 ns, respectively. In the first and second halves, the lateral evolution rate of the stream increased by 2.75 times and 0.88 times, respectively. The increase in temperature increased the migration rate of charge carriers in the oil. At the same time, the decrease in oil viscosity increased the oil flow shear term of the charge carriers, which increased the lateral evolution rate of the stream. As the stream head gradually moved away from the strong field region (second half), the tangential electric field at the interface decreased with the lateral distance, the electric force on the charge carriers decreased, and the increase in the lateral evolution rate decreased.

[0127] As the temperature increases from 320 K to 380 K, the charge density at point (0.4,1) increases from 2572.58 C / m². 3 It gradually increased to 2701.17 C / m 3 2889.75 C / m 3 and 3058.64 C / m 3 This represents an increase of approximately 18.9%. Simultaneously, the charge density at point (0.8,1) also increased from 2103.77 C / m³ at 320 K. 3 It increased to 2577.46 C / m at 360 K. 3 This is because the increase in temperature accelerates the lateral charge transport at point (0,1) and simultaneously increases the free hole trapping rate, resulting in a gradual increase in the charge amount at the stream head. The increased interfacial charge density caused by the increased trapping rate leads to a gradual widening of the discharge phase, such as... Figure 13 As shown, at 380 K, the charge density at point (0.8,1) decreased by about 11.4% compared to the charge density at 360 K. This is because, during the latter half of the evolution, while the tangential electric field at the interface gradually weakens, the recombination rate and trapping rate of the charge carriers also gradually increase, and the charge relaxation becomes more significant.

[0128] Step 303: Analyze the evolution law of the streamer based on the charge density distribution and electric field intensity distribution data to evaluate the oil paper insulation state or optimize the oil paper insulation structure;

[0129] Based on streamer evolution simulation, the development and evolution process of streamer discharge under the multi-field coupling of electric current and heat was studied. The simulation results can provide theoretical support for the state assessment and structural optimization of oil-paper insulation of converter transformers, including:

[0130] 1) Due to the negative DC bias and the presence of harmonics, the charge distribution at the oil-paper insulation interface exhibits obvious segmentation and peak phenomena. Increased temperature increases the number of traps within the insulation paper, with deep traps showing a more pronounced increase. At the high-energy end of 0.936 eV, the deep trap density increases from 4.97 × 10⁹ m³ at 320 K. - ³·eV - ¹ 13 × 10⁹ m at 380 K - ³·eV - ¹, which increased by approximately 1.61 times.

[0131] 2) As temperature increases, the streamer initiation voltage first decreases and then increases. The numerous deep traps formed at high temperatures hinder the formation of the first electron avalanche through bound charges, causing the streamer initiation voltage to increase from 8.8 kV at 360 K to 9.2 kV. Guided by the high waveform steepness caused by harmonics, a large number of charges in traps at different energy levels detach and recombine at different times, causing the discharge phase to gradually widen with increasing temperature. At 380 K, the pulse distribution approaches full-phase discharge (349°).

[0132] 3) The discharge in high-temperature flowing oil was divided into three evolution stages. It was found that the streamer forms a sloping, wide discharge channel in the oil, and after reaching the oil-paper interface, it migrates rapidly along the oil flow direction, forming a significant spur current. Increased temperature increases the dissociation rate of oil molecules and the charge trapping rate in the paper. Accompanying this increase in the oil flow shear term, the head charge of the streamer gradually increases during its lateral evolution. However, the recombination rate and trapping rate of charge carriers also gradually increase. As the streamer moves further away from the strong field region, the charge relaxation phenomenon becomes more pronounced.

[0133] Example 2

[0134] This embodiment provides a streamer discharge simulation modeling system for charge behavior under complex operating conditions, including:

[0135] The streamer discharge model construction module is used to establish a simulation model of dynamic charge transport in multiple regions of the oil-paper interface, coupled with oil flow convection, shearing, and temperature effects, based on the theory of electric dipole layer shear separation. Specifically, it includes:

[0136] Based on the influence of oil flow convection terms and temperature, a modified fluid dynamics drift-diffusion model is used to describe the dynamic process of charge in oil.

[0137] Based on the influence of temperature on the carrier migration process, a modified bipolar carrier migration model is used to describe the dynamic process of charge in paper.

[0138] Based on the effects of oil flow convection, oil flow shear, and temperature, a modified Ohmic model is used to describe the charge dynamics at the oil-paper interface.

[0139] The streamer discharge evolution simulation module is used to simulate the entire evolution process of streamer discharge from diffusion and longitudinal evolution to lateral migration under the multi-field coupling of electric current and heat, based on the established transport simulation model and combined with the charge injection and extraction boundary conditions at the electrodes, and to obtain the charge density distribution and electric field intensity distribution data during the streamer evolution process.

[0140] The strategy generation module is used to analyze the evolution law of the streamer based on the charge density distribution and electric field intensity distribution data, so as to evaluate the state of the oil-paper insulation or optimize the oil-paper insulation structure.

[0141] It should be noted that the specific implementation of the streamer discharge simulation modeling system for charge behavior under complex operating conditions coupled in this embodiment of the invention is similar to the specific implementation of the streamer discharge simulation modeling method for charge behavior under complex operating conditions coupled in this embodiment of the invention. For details, please refer to the description in the method section. To reduce redundancy, it will not be repeated here.

[0142] Example 3

[0143] This embodiment provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps in the above-described method for simulating and modeling charge behavior under complex operating conditions.

[0144] Example 4

[0145] This embodiment provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the steps in the streamer discharge simulation modeling method for charge behavior under complex operating conditions as described above.

[0146] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of hardware embodiments, software embodiments, or embodiments combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage and optical storage) containing computer-usable program code.

[0147] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0148] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0149] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0150] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

[0151] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for simulating and modeling the charge behavior of streamer discharge under complex coupled operating conditions, characterized in that, Includes the following steps: Based on the theory of electric double layer shear separation, a simulation model of dynamic charge transport in multiple regions of the oil-paper interface is established, coupling oil flow convection terms, shear terms, and temperature effects; specifically including: Based on the influence of oil flow convection terms and temperature, a modified fluid dynamics drift-diffusion model is used to describe the dynamic process of charge in oil. Based on the influence of temperature on the carrier migration process, a modified bipolar carrier migration model is used to describe the dynamic process of charge in paper. Based on the effects of oil flow convection, oil flow shear, and temperature, a modified Ohmic model is used to describe the charge dynamics at the oil-paper interface. Based on the established transport simulation model, combined with the charge injection and extraction boundary conditions at the electrodes, the entire evolution process of the streamer discharge from diffusion and longitudinal evolution to lateral migration under the multi-field coupling of electric current and heat is simulated, and the charge density distribution and electric field intensity distribution data during the streamer evolution process are obtained. The evolution of the streamer is analyzed based on the charge density distribution and electric field intensity distribution data to evaluate the state of the oil-paper insulation or optimize the oil-paper insulation structure. The oil-based model used to describe the dynamic process of charge in the oil is expressed as follows: ， ， ， ， ， In the formula, , and These represent the charge densities of electrons, positive ions, and negative ions, respectively. Let be the charge density at the oil-paper interface. For oil flow velocity, For electron adsorption time, The electron mobility in oil, and These represent the recombination rates of positive ions with electrons and positive ions with negative ions, respectively. For charge quantity, Let be the relative permittivity of oil. The vacuum permittivity, The positive ion mobility in oil. The migration rate of negative ions in oil. The charge density generation rate caused by field ionization. The charge density generation rate resulting from ion pair dissociation. The charge density generation rate resulting from impact ionization. The thermal conductivity of oil is... For oil density, The specific heat capacity of oil. For electric potential, For electric field strength, It is a vector differential operator; The paper model used to describe the dynamic process of charge in paper is represented as follows: ， ， ， ， ， In the formula, These represent the charge densities of free electrons, trapped electrons, free holes, and trapped holes, respectively. The free electron mobility in the insulating paperboard. The free hole mobility on the insulating paperboard. For maximum electron capture density, The relative permittivity of the insulating paperboard is... These represent the recombination rates of trapped electrons and trapped holes, free electrons and trapped holes, and trapped electrons and free holes, respectively. and These are the trapping rates for electrons and holes, respectively. and These are the extraction rates of electrons and holes, respectively. The vacuum permittivity, Electric field strength; The oil-paper interface model used to describe the charge dynamics at the oil-paper interface is represented as follows: ， ， In the formula, and These represent the charge densities of electrons, positive ions, and negative ions, respectively. Let be the charge density at the oil-paper interface. For tangential velocity, It is the acceleration due to gravity. For oil density, The charge stripping coefficient, For oil flow shear stress, The positive ion mobility in oil. The migration rate of negative ions in oil. The electron mobility in oil, and These represent the charge densities of free electrons and free holes, respectively. The free electron mobility in the insulating paperboard. The free hole mobility on the insulating paperboard. and These represent the oil-side electric field and the paper-side electric field at the oil-paper interface, respectively. This represents the oil flow velocity.

2. The streamer discharge simulation modeling method for charge behavior under complex operating conditions as described in claim 1, characterized in that, The recombination rate, trapping rate, and de-trapping rate are all thermally activated processes, and their calculation process is expressed as follows: ， In the formula, This indicates the recombination rate, trapping rate, and de-trapping rate of charges in paper at ambient temperature. This represents the recombination rate, trapping rate, and de-trapping rate of charges in the paper at a reference temperature. For reference temperature, for Thermal activation energy during the process Indicates the type of charge in the paper. This indicates the composite rate, the ingress rate, and the detachment rate. Indicates the composite rate. Indicates the trapping rate. Indicates the rate of detachment. Represents electron, It indicates an empty hole.

3. The streamer discharge simulation modeling method for charge behavior under complex operating conditions as described in claim 1, characterized in that, The boundary conditions for charge injection and extraction at the electrodes include the current density of charge injected into the oil by the high-pressure side electrode, the current density of charge injected into the paper by the low-pressure side electrode, and the current density of charge extracted by the high-pressure side electrode and the low-pressure side electrode.

4. The streamer discharge simulation modeling method for charge behavior under complex operating conditions as described in claim 1, characterized in that, The entire evolution process of the streamer discharge under simulated electric-current-thermal multi-field coupling, from diffusion and vertical evolution to lateral migration, includes: During the diffusion stage, the simulation simulates the release of positive charges from the needle electrode and their diffusion to the surrounding area, as well as the migration of negative charges to the needle electrode, resulting in charge stratification to form a streamer boundary, and simulates the recombination of positive and negative charges to form a zero electric field region. In the longitudinal evolution stage, the simulated flow boundary develops along the symmetrical axis perpendicular to the paperboard and towards the paperboard, forming the main discharge channel; During the lateral evolution stage, the simulation shows that after the stream head reaches the paper interface, the positive polarity charge develops and dissipates tangentially at the paperboard interface.

5. A streamer discharge simulation modeling system for charge behavior under complex operating conditions, characterized in that, The method for simulating and modeling the charge behavior under complex operating conditions as described in any one of claims 1-4 includes: The streamer discharge model construction module is used to establish a simulation model of dynamic charge transport in multiple regions of the oil-paper interface, coupled with oil flow convection, shearing, and temperature effects, based on the theory of electric dipole layer shear separation. Specifically, it includes: Based on the influence of oil flow convection terms and temperature, a modified fluid dynamics drift-diffusion model is used to describe the dynamic process of charge in oil. Based on the influence of temperature on the carrier migration process, a modified bipolar carrier migration model is used to describe the dynamic process of charge in paper. Based on the effects of oil flow convection, oil flow shear, and temperature, a modified Ohmic model is used to describe the charge dynamics at the oil-paper interface. The streamer discharge evolution simulation module is used to simulate the entire evolution process of streamer discharge from diffusion and longitudinal evolution to lateral migration under the multi-field coupling of electric current and heat, based on the established transport simulation model and combined with the charge injection and extraction boundary conditions at the electrodes, and to obtain the charge density distribution and electric field intensity distribution data during the streamer evolution process. The strategy generation module is used to analyze the evolution law of the streamer based on the charge density distribution and electric field intensity distribution data, so as to evaluate the state of the oil-paper insulation or optimize the oil-paper insulation structure.

6. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps in the streamer discharge simulation modeling method for charge behavior under complex operating conditions as described in any one of claims 1-4.

7. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps in the streamer discharge simulation modeling method for charge behavior under complex operating conditions as described in any one of claims 1-4.

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